METHODS OF DIAGNOSING AND PROGNOSING LUNG CANCER
The present invention provides methods of detecting cancer using biomarkers.
This application claims the benefit of U.S. Ser. No. 60/888,190 filed Feb. 5, 2007 and the contents of which are incorporated herein by reference in its entirety.
FIELD OF THE INVENTIONThe invention relates to generally to detecting cancer.
BACKGROUND OF THE INVENTIONNon-small cell lung cancer (NSCLC) is the most common and lethal cancer world-wide. At least three major histologies of NSCLC are described: squamous carcinoma (48%), large cell carcinoma (12%) and adenocarcinoma (40%) The standard treatment for these patients is systemic chemotherapy. However, systemic chemotherapy has modest efficacy and has not greatly prolonged the median survival (8-12 months) or 5-year survival rates (2%) in these patients. Although these sub-types differ markedly in histologic appearance and gene expression, each is highly lethal, and until recently, little clinical distinction has been made among these entities.
It is anticipated that a better understanding of the molecular mechanisms involved in the initiation and progression lung tumorigenesis—as well as the impact of environmental exposures on lung carcinogenesis—would help guide the development of better and more targeted lung cancer therapeutics as well as potential prevention strategies. The recent identification of the oncogenic kinase domain mutations in the epidermal growth factor receptor (EGFR) in human lung adenocarcinomas and their association with sensitivity to small molecule EGFR kinase inhibitors such as gefitinib and erlotinib further support the that the molecular understanding of the mechanisms involved in lung tumorigenesis will lead to advances in patient screening, development of better targeted therapeutics, and identification of patients who are best suited for each type of targeted treatment. Activating K-RAS, EGFR, and BRAF mutations comprise the most common oncogenic mutations in human NSCLC. However, their interaction with other concurrent tumor suppressor loss is not well understood.
SUMMARY OF THE INVENTIONThe invention provides biological markers for monitoring, diagnosing and prognosing lung cancer.
In one aspect the invention provides a method for determining the aggressiveness of a lung cancer in a mammal, e.g. human, by determining in a test sample from the mammal, the presence or absence of Lkb1 expression or activity and correlating the presence or absence with aggressiveness of the lung cancer. The absence of Lkb1 expression or decrease of the activity of Lkb1 indicates the cancer is aggressive and/or metastatic. In contrast, the presence of intact Lkb1, e.g. non-mutated indicates the cancer is not aggressive. The test sample is for example a tumor biopsy.
Optionally, the method includes determining the presence or absence of an additional tumor biomarker such as determining the presence or absence of a mutation in K-ras, EGFR or BRAF.
Also included in the invention is a method of assessing the efficacy of an m-TOR inhibitor for treating or inhibiting the growth of lung cancer in a patient, by detecting inactivation of Lkb1 gene expression in a lung cancer tumor from a subject. Inactivation of Lkb1 gene expression in the lung cancer tumor indicates treatment with an m-TOR inhibitor is efficacious.
Lung cancer is diagnosed or a predisposition to developing lung cancer in a subject by determining a level of expression of a lung cancer-associated gene in a patient derived tissue sample. By LC associated gene is meant a gene that is characterized by a level of expression which differs in a cell obtained from a lung cancer cell compared to a normal cell. A normal cell is one obtained from lung tissue. A LC-associated gene includes for example LC 1-461. An alteration, e.g., increase of the level of expression of the gene compared to a normal control level of the gene indicates that the subject suffers from or is at risk of developing lung cancer.
Alternatively, expression of a panel of LC-associated genes in the sample is compared to a LC control level of the same panel of genes. By LC control level is meant the expression profile of the LC-associated genes found in a population suffering from lung cancer.
Gene expression is increased or decreased 10%, 25%, 50% compared to the control level. Alternately, gene expression is increased or decreased 1, 2, 5 or more fold compared to the control level. Expression is determined by detecting hybridization, e.g., on a chip, of a LC-associated gene probe to a gene transcript of the patient-derived tissue sample.
The patient derived tissue sample is any tissue from a test subject, e.g., a patient known to or suspected of having lung cancer. For example, the tissue contains a sputum, blood, serum, plasma or lung cell.
The invention also provides a LC reference expression profile of a gene expression level of two or more of PRC 1-461.
The invention further provides a kit with a detection reagent which binds to two or more LC nucleic acid sequences or which binds to a gene product encoded by the nucleic acid sequences. Also provided is an array of nucleic acids that binds to two or more LC nucleic acids.
In another aspect, the invention includes a transgenic animal whose genome contains a mutant K-ras oncogene, e.g. G12D mutation and at least one Lkb1 null allele. The transgenic animal constitutively expresses a mutated K-ras protein in at least one tissue and exhibits accelerated development of a lung tumor. Optionally, the animal is homozygous null for Lkb1.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.
The invention is based upon the discovery of biomarkers for the detection and assessment of cancer. Specifically, it has been shown that a somatic deficiency in the kinase, Lkb1 accelerates the development of lung tumerigenesis. More specifically, Lkb1 deficiency in the setting of K-rasG12D mutation (K-rasLkb1L/L) was associated with decreased tumor latency and increased tumor aggressiveness including metastasis. Furthermore, tumors from K-ras Lkb1L/L mice demonstrated mice exhibit the full range of histologic subtypes (including squamous, adenosquamous, and large-cell) that arise in humans, whereas K-rasG12D mutation, Ink4a/Arf inactivation, or p53 inactivation alone or in combination result only in adenocarcinoma. These findings suggest that, unexpectedly, Lkb1 influences cell differentiation in addition to its roles in the suppression of cell growth. Experiments in vitro demonstrate that LKB1 suppresses lung tumorigenesis and progression through both p16INK4a-ARF-p53 dependent and independent mechanisms. These data indicate that LKB1 regulates lung tumor progression by controlling multiple aspects of cell growth and differentiation.
Additionally, a comprehensive microarray analysis was performed on K-ras induced lung tumors to identify commonly over-expressed genes. Four hundred and sixty one genes were up-regulated.
The genes whose expression levels are modulated (i.e., increased) in lung cancer are summarized in Table A and are collectively referred to herein as “lung cancer-associated genes”, “LC nucleic acids” or “LC polynucleotides” and the corresponding encoded polypeptides are referred to as “LC polypeptides” or “LC proteins.” Unless indicated otherwise, “LC” is meant to refer to any of the sequences disclosed herein. (e.g., LC 1-461). The genes have been previously described and are presented along with a database accession number.
Accordingly, the invention provides methods of detecting and evaluating the aggressiveness of lung cancer in a subject by determining the presence or absence of Lkb1. In addition, the differentially expressed genes identified herein are used for diagnostic purposes and to develop gene targeted therapeutic approaches to inhibiting lung cancer.
Inherited mutation in LKB1 results in the Peutz-Jeghers syndrome (PJS), characterized by intestinal hamartomas and an increased frequency of gastrointestinal and breast cancer36. Somatic inactivation of LKB1 occurs in human lung adenocarcinoma9,10,37, but its tumor suppressor role in this tissue is uncertain. Although activation of many kinases (e.g. BRAF, EGFR, etc.) is oncogenic, LKB1 appears unusual in cancer biology in that its kinase activity conveys tumor suppressor activity38. LKB1 can phosphorylate multiple cellular substrates and has been implicated in playing important roles in a myriad of cellular metabolic functions including protein synthesis, gluconeogensis, adipogenesis, and steroidogenesis as well as cell polarity. All the substrates of LKB1 that are relevant to tumor suppression are not known, but AMPK, the kinase crucially involved in regulating the mTOR pathway, has been shown to be one definite LKB substrate39-41.
LKB1 phosphorylates and activates AMP Kinase (AMPK) in settings of high AMP levels (i.e., low energy states). AMPK, in turn, phosphorylates Tuberin, but unlike phosphorylation by Akt, this activates Tuberin's GAP activity leading to inhibition of mTOR activity. However, in LKB1-deficient cells, AMPK cannot be activated, and mTOR remains constitutively active under conditions of energy stress. Thus, mTOR is regulated by growth factor receptor signaling, nutrient availability, and the energy status of the cell. This ensures that a cell normally commits to growth upon appropriate growth stimuli and environmental cues. Transformed and cancer cells, however, bypass one or more of these control mechanisms to grow without restraint. The mTOR pathway is frequently deregulated in many different types of cancer.
In addition, recent studies suggest that LKB1 may play an important role in mediating the cellular responses to DNA damage. ATM, a kinase involved in DNA damage checkpoint and p53-dependent apoptosis, phosphorylates LKB1 on Thr366 after radiation-induced DNA damage43,44. This region of LKB1 had been shown to be necessary for its growth suppression function43,44. Thus, the loss of LKB1 might render the affected cells more prone to DNA damage and increased genetic alterations. Lastly, reactive lipid species, such as cyclopentenone, often generated in the setting of chronic inflammation and oxidative stress, can inactivate the functional activity of LKB1 through the formation of a covalent adduct at Cys210, an important amino acid in LKB1's activation loop45.
A human Lkb1 nucleic acid and polypeptide are shown in Table 1 and 2 respectively (SEQ ID NO:1 and SEQ ID NO:2).
The aggressiveness of lung cancers is determined by examining the presence (e.g, expression) or absence of a Lkb1 nucleic acid, polypeptide or activity in a test sample (i.e., a patient derived sample). Preferably, the test sample is a tumor biopsy. A change in the level of the Lkb1 nucleic acid, polypeptide or activity compared to a control sample is indicative of the aggressiveness of the lung cancer in the subject. The absence of the Lkb1 nucleic acid or polypeptide or a decrease in the activity of Lkb1 in the test sample indicates that the cancer is aggressive, thus a less favorable prognosis for the patient. An aggressive tumor is metastatic, thus the absence of the Lkb1 nucleic acid or polypeptide or a decrease in the activity of Lkb1 in the test sample indicates that the tumor is metastatic. In contrast, the presence of the Lkb1 nucleic acid or polypeptide or activity of Lkb1 indicates that the lung cancer is not aggressive, thus a more favorable prognosis for the patient.
Additionally, the presence or absence of a mutation the Lkb1 nucleic acid is indicative of the aggressiveness of the lung cancer in the subject. For example, the presence of a mutation in the the Lkb1 nucleic acid in the test sample indicates that the cancer is aggressive, thus a less favorable prognosis for the patient. Whereas the absence a mutation in the Lkb1 nucleic acid indicates that the lung cancer is not aggressive, thus a more favorable prognosis for the patient.
By aggressiveness it is meant that that the tumor is quick growing and spreading (i.e, metastasizing.
The amount of the Lkb1 nucleic acid, polypeptide or activity is determined in the test sample and compared to the expression of the normal control level. By normal control level is meant the expression level of a Lkb1 nucleic acid, polypeptide or activity typically found in a subject not suffering from lung cancer.
The alteration in the amount of the Lkb1 nucleic acid, polypeptide or activity is statistically significant. By statistically significant is meant that the alteration is greater than what might be expected to happen by change alone. Statistical significance is determined by method known in the art. For example statistical significance is determined by p-value. The p-values is a measure of probability that a difference between groups during an experiment happened by chance. (P(z≧zobserved)). For example, a p-value of 0.01 means that there is a 1 in 100 chance the result occurred by chance. The lower the p-value, the more likely it is that the difference between groups was caused by treatment. An alteration is statistically significant if the p-value is at least 0.05. Preferably, the p-value is 0.04, 0.03, 0.02, 0.01, 0.005, 0.001 or less.
The “diagnostic accuracy” of a test, assay, or method concerns the ability of the test, assay, or method to distinguish between patients having aggressive lung cancer and non-aggressive lung cancer is based on whether the patients have a “clinically significant presence or absence” of a Lkb1 nucleic acid, polypeptide or activity. By “clinically significant presence” is meant that the presence of the Lkb1 nucleic acid, polypeptide or activity in the patient (typically in a sample from the patient) is higher or lower than the predetermined cut-off point (or threshold value) for Lkb1 nucleic acid, polypeptide or activity and therefore indicates that the patient has cancer for which the sufficiently high presence of that protein is a marker.
The terms “high degree of diagnostic accuracy” and “very high degree of diagnostic accuracy” refer to the test or assay for that Lkb1 nucleic acid, polypeptide or activity with the predetermined cut-off point correctly (accurately) indicating the presence or absence of the cancer. A perfect test would have perfect accuracy. Thus, for individuals who have aggressive lung cancer, the test would indicate only positive test results and would not report any of those individuals as being “negative” (there would be no “false negatives”). In other words, the “sensitivity” of the test (the true positive rate) would be 100%. On the other hand, for individuals who did not have aggressive lung cancer, the test would indicate only negative test results and would not report any of those individuals as being “positive” (there would be no “false positives”). In other words, the “specificity” (the true negative rate) would be 100%. See, e.g., O'Marcaigh A S, Jacobson R M, “Estimating The Predictive Value Of A Diagnostic Test, How To Prevent Misleading Or Confusing Results,” Clin. Ped. 1993, 32(8): 485-491, which discusses specificity, sensitivity, and positive and negative predictive values of a test, e.g., a clinical diagnostic test.
Changing the cut point or threshold value of a test (or assay) usually changes the sensitivity and specificity but in a qualitatively inverse relationship. For example, if the cut point is lowered, more individuals in the population tested will typically have test results over the cut point or threshold value. Because individuals who have test results above the cut point are reported as having the disease, condition, or syndrome for which the test is being run, lowering the cut point will cause more individuals to be reported as having positive results (i.e., that they have cancer). Thus, a higher proportion of those who have cancer will be indicated by the test to have it. Accordingly, the sensitivity (true positive rate) of the test will be increased. However, at the same time, there will be more false positives because more people who do not have the disease, condition, or syndrome (i.e., people who are truly “negative”) will be indicated by the test to have Lkb1 nucleic acid, polypeptide or activity values above the cut point and therefore to be reported as positive rather than being correctly indicated by the test to be negative. Accordingly, the specificity (true negative rate) of the test will be decreased. Similarly, raising the cut point will tend to decrease the sensitivity and increase the specificity. Therefore, in assessing the accuracy and usefulness of a proposed medical test, assay, or method for assessing a patient's condition, one should always take both sensitivity and specificity into account and be mindful of what the cut point is at which the sensitivity and specificity are being reported because sensitivity and specificity may vary significantly over the range of cut points.
There is, however, an indicator that allows representation of the sensitivity and specificity of a test, assay, or method over the entire range of cut points with just a single value. That indicator is derived from a Receiver Operating Characteristics (“ROC”) curve for the test, assay, or method in question. See, e.g., Shultz, “Clinical Interpretation Of Laboratory Procedures,” chapter 14 in Teitz, Fundamentals of Clinical Chemistry, Burtis and Ashwood (eds.), 4th edition 1996, W.B. Saunders Company, pages 192-199; and Zweig et al., “ROC Curve Analysis: An Example Showing The Relationships Among Serum Lipid And Apolipoprotein Concentrations In Identifying Patients With Coronary Artery Disease,” Clin. Chem., 1992, 38(8): 1425-1428.
An ROC curve is an x-y plot of sensitivity on the y-axis, on a scale of zero to one (i.e., 100%), against a value equal to one minus specificity on the x-axis, on a scale of zero to one (i.e., 100%). In other words, it is a plot of the true positive rate against the false positive rate for that test, assay, or method. To construct the ROC curve for the test, assay, or method in question, patients are assessed using a perfectly accurate or “gold standard” method that is independent of the test, assay, or method in question to determine whether the patients are truly positive or negative for the disease, condition, or syndrome (for example, coronary angiography is a gold standard test for the presence of coronary atherosclerosis). The patients are also tested using the test, assay, or method in question, and for varying cut points, the patients are reported as being positive or negative according to the test, assay, or method. The sensitivity (true positive rate) and the value equal to one minus the specificity (which value equals the false positive rate) are determined for each cut point, and each pair of x-y values is plotted as a single point on the x-y diagram. The “curve” connecting those points is the ROC curve.
The area under the curve (“AUC”) is the indicator that allows representation of the sensitivity and specificity of a test, assay, or method over the entire range of cut points with just a single value. The maximum AUC is one (a perfect test) and the minimum area is one half. The closer the AUC is to one, the better is the accuracy of the test.
By a “high degree of diagnostic accuracy” is meant a test or assay (such as the test of the invention for determining the clinically significant presence of Lkb1 nucleic acid, polypeptide or activity, in which the AUC (area under the ROC curve for the test or assay) is at least 0.70, desirably at least 0.75, more desirably at least 0.80, preferably at least 0.85, more preferably at least 0.90, and most preferably at least 0.95.
By a “very high degree of diagnostic accuracy” is meant a test or assay in which the AUC (area under the ROC curve for the test or assay) is at least 0.875, desirably at least 0.90, more desirably at least 0.925, preferably at least 0.95, more preferably at least 0.975, and most preferably at least 0.98.
Optionally, the subject is tested for carrying other indicators of susceptibility of developing cancer. For example, the presence or absence of a mutation in K-ras, EGFR or BRAF is determined in the test sample.
The Lkb1 nucleic acid, polypeptide or activity are detected in any suitable manner, but is typically detected by contacting a sample from the patient with an antibody which binds the Lkb1 nucleic acid, polypeptide and then detecting the presence or absence of a reaction product. The antibody may be monoclonal, polyclonal, chimeric, or a fragment of the foregoing, as discussed in detail above, and the step of detecting the reaction product may be carried out with any suitable immunoassay. The sample from the subject is typically a tumor biopsy as described above.
Lung cancer is also diagnosed by examining the expression of one or more LC nucleic acid or polypeptide sequences from a test population of cells, (i.e., a patient derived tissue sample) that contain or suspected to contain a non-small cell lung cancer cell. Preferably, the test cell population comprises a lung cell, e.g., a cell obtained from the lung. Gene expression is also measured from blood or other bodily fluids such as sputum.
Expression of one or more of a lung cancer-associated gene, e.g., LC 1-461 is determined in the test cell and compared to the expression of the normal control level. By normal control level is meant the expression profile of the lung cancer-associated genes typically found in a population not suffering from lung cancer. An increase of the level of expression in the patient derived tissue sample of the lung cancer associated genes indicates that the subject is suffering from or is at risk of developing lung cancer.
Also provided is a method of assessing the prognosis of a subject with lung cancer by comparing the expression of one or more LC sequences in a test cell population to the expression of the sequences in a reference cell population derived from patients over a spectrum of disease stages. By comparing gene expression of one or more LC sequences in the test cell population and the reference cell population(s), or by comparing the pattern of gene expression over time in test cell populations derived from the subject, the prognosis of the subject can be assessed. For example, an increase in expression of one or more of the sequences LC 1-461 compared to a normal control indicates less favorable prognosis.
The differentially LC sequences identified herein also allow for the course of treatment of lung cancer to be monitored. In this method, a test cell population is provided from a subject undergoing treatment for lung cancer. If desired, test cell populations are obtained from the subject at various time points before, during, or after treatment. Expression of one or more of the LC sequences, in the cell population is then determined and compared to a reference cell population which includes cells whose lung cancer state is known. The reference cells have not been exposed to the treatment.
If the reference cell population contains no lung cancer cells, a similarity in expression between LC sequences in the test cell population and the reference cell population indicates that the treatment is efficacious. However, a difference in expression between LC sequences in the test population and this reference cell population indicates the a less favorable clinical outcome or prognosis.
By “efficacious” is meant that the treatment leads to a reduction in expression of a pathologically upregulated gene, increase in expression of a pathologically down-regulated gene or a decrease in size, prevalence, or metastatic potential of lung cancer in a subject. When treatment is applied prophylactically, “efficacious” means that the treatment retards or prevents lung cancer from forming. Assessment of lung cancer is made using standard clinical protocols.
Efficaciousness is determined in association with any known method for diagnosing or treating non-small cell lung cancer. Lung cancer is diagnosed for example, by identifying symptomatic anomalies, e.g., chronic cough, hoarseness, coughing up blood, weight loss, loss of appetite, shortness of breath, wheezing, repeated bouts of bronchitis or pneumonia, and chest pain or histopathologically.
Expression of Lkb1 also allows the identification of patients who will be responsive to systemic therapy, e.g. m-TOR inhibitors. In this method, a tumor sample is provided from a subject and Lkb1 expression is determined. Identification of inactivation of the Lkb1 gene indicate that the therapy will be efficacious. In contrast a the patient will likely not be responsive to systemic treatment with an M-TOR inhibitor if the Lkb1 gene is active. By inactivation is meant a decrease in Lkb1 expression or activity. For example the Lkb1 gene is inactivated due to a mutation.
The subject is preferably a mammal. The mammal is, e.g., a human, non-human primate, mouse, rat, dog, cat, horse, or cow. Subjects are typically human females or human males.
The subject has been previously diagnosed as carrying a cancer, and possibly has already undergone treatment for the cancer. Alternatively, the subject has not been previously diagnosis as carrying a cancer. The present invention is useful with all patients at risk for a cancer. Although each type of cancer has their own set of risk factors, the risk of developing cancer increases as with aged, gender, race and personal and family medical history. Other risk factors are largely related to lifestyle choices, while certain infections, occupational exposures and some environmental factors can also be related to developing cancer. Lung cancer risk factors include personal and family history of lung cancer, smoking, exposure to asbestos, radon or other carcinogens, air pollution, Vitamin A deficiency, or reoccurring inflammation.
Diagnosis of cancer is typically made through the identification of a mass on an examination, though it may also be through other means such as a radiological diagnosis, or ultrasound. Treatment is typically through cytoreductive surgery. In addition, many patients will require radiation therapy.
Expression of the Lkb1, a LC nuclic acid or polypeptide or other cancer biomarkers (e.g., K-ras, EGFR or BRAf) is determined at the protein or nucleic acid level using any method known in the art. For example, Northern hybridization analysis using probes which specifically recognize one or more of these sequences can be used to determine gene expression. Alternatively, expression is measured using reverse-transcription-based PCR assays, e.g., using primers specific for the differentially expressed sequence of genes. Expression is also determined at the protein level, i.e., by measuring the levels of peptides encoded by the gene products described herein, or activities thereof. Such methods are well known in the art and include, e.g., immunoassays based on antibodies to proteins encoded by the genes. Any biological material can be used for the detection/quantification of the protein or it's activity. Alternatively, a suitable method can be selected to determine the activity of proteins encoded by the marker genes according to the activity of each protein analyzed.
Immunoassays carried out in accordance with the present invention may be homogeneous assays or heterogeneous assays. In a homogeneous assay the immunological reaction usually involves the specific antibody (e.g., fibrinogen αC domain peptide or hemoglobin polypeptide), a labeled analyte, and the sample of interest. The signal arising from the label is modified, directly or indirectly, upon the binding of the antibody to the labeled analyte. Both the immunological reaction and detection of the extent thereof are carried out in a homogeneous solution. Immunochemical labels which may be employed include free radicals, radioisotopes, fluorescent dyes, enzymes, bacteriophages, or coenzymes.
In a heterogeneous assay approach, the reagents are usually the sample, the antibody, and means for producing a detectable signal. Samples as described above may be used. The antibody is generally immobilized on a support, such as a bead, plate or slide, and contacted with the specimen suspected of containing the antigen in a liquid phase. The support is then separated from the liquid phase and either the support phase or the liquid phase is examined for a detectable signal employing means for producing such signal. The signal is related to the presence of the analyte in the sample. Means for producing a detectable signal include the use of radioactive labels, fluorescent labels, or enzyme labels. For example, if the antigen to be detected contains a second binding site, an antibody which binds to that site can be conjugated to a detectable group and added to the liquid phase reaction solution before the separation step. The presence of the detectable group on the solid support indicates the presence of the antigen in the test sample. Examples of suitable immunoassays are radioimmunoassays, immunofluorescence methods, or enzyme-linked immunoassays.
Those skilled in the art will be familiar with numerous specific immunoassay formats and variations thereof, which may be useful for carrying out the method disclosed herein. See generally E. Maggio, Enzyme-Immunoassay, (1980) (CRC Press, Inc., Boca Raton, Fla.); see also U.S. Pat. No. 4,727,022 to Skold et al. titled “Methods for Modulating Ligand-Receptor Interactions and their Application,” U.S. Pat. No. 4,659,678 to Forrest et al. titled “Immunoassay of Antigens,” U.S. Pat. No. 4,376,110 to David et al., titled “Immunometric Assays Using Monoclonal Antibodies,” U.S. Pat. No. 4,275,149 to Litman et al., titled “Macromolecular Environment Control in Specific Receptor Assays,” U.S. Pat. No. 4,233,402 to Maggio et al., titled “Reagents and Method Employing Channeling,” and U.S. Pat. No. 4,230,767 to Boguslaski et al., titled “Heterogeneous Specific Binding Assay Employing a Coenzyme as Label.”
Antibodies are conjugated to a solid support suitable for a diagnostic assay (e.g., beads, plates, slides or wells formed from materials such as latex or polystyrene) in accordance with known techniques, such as precipitation. An antibody or antibody fragment that binds to CA-125 or CEA may optionally be conjugated to the same support, as discussed above. Antibodies as described herein may likewise be conjugated to detectable groups such as radiolabels (e.g., 35 S, 125 I, 131 I), enzyme labels (e.g., horseradish peroxidase, alkaline phosphatase), and fluorescent labels (e.g., fluorescein) in accordance with known techniques.
Screening Methods
An agent that inhibits the expression or activity of a lung cancer-associated gene is identified by contacting a test cell population expressing a lung cancer associated upregulated gene with a test agent and determining the expression level of the lung cancer associated gene. A decrease in expression compared to the normal control level indicates the agent is an inhibitor of a lung cancer associated upregulated gene and useful to inhibit non-small cell lung cancer.
The differentially expressed sequences disclosed herein can also be used to identify candidate therapeutic agents for treating lung cancer. The method is based on screening a candidate therapeutic agent to determine if it converts an expression profile of LC 1-461 sequences characteristic of a lung cancer state to a pattern indicative of a non lung cancer state.
In the method, a cell is exposed to a test agent or a combination of test agents (sequentially or consequentially) and the expression of one or more LC 1-461 sequences in the cell is measured. The expression profile of the LC sequences in the test population is compared to expression level of the LC sequences in a reference cell population that is not exposed to the test agent.
Alternatively, the screening of the present invention may comprise the steps described below. A protein required for the screening can be obtained as a recombinant protein by using the nucleotide sequence of the marker gene. Based on the information on the marker gene, one skilled in the art can select the biological activity of a protein as an index of screening and a measurement method for the activity.
(1) the step of contacting a candidate agent with the protein encoded by a marker gene; and
(2) the step of selecting a candidate agent that alters the activity of the protein as compared with that in a control.
Alternatively, the screening of the present invention may comprise the steps described below. A reporter construct required for the screening can be prepared by using the transcriptional regulatory region of a marker gene. When the transcriptional regulatory region of a marker gene has been known to those skilled in the art, a reporter construct can be prepared by using the previous sequence information. When the transcriptional regulatory region of a marker gene remains unidentified, a nucleotide segment containing the transcriptional regulatory region can be isolated from a genome library based on the nucleotide sequence information of the marker gene.
(1) the step of preparing a reporter construct that ensures the expression of the reporter gene under control of the transcriptional regulatory region of the marker gene;
(2) the step of contacting a candidate agent with host cells containing and capable of expressing the above-mentioned reporter construct; and
(3) the step of measuring the expression level of the reporter gene, and selecting a candidate agent that has an activity of altering the expression level when compared with that in a control.
There is no limitation on the type of candidate agent in the screening of the present invention. The candidates of the present invention can be obtained using any of the numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the “one-bead one-compound” library method; and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam (1997)Anticancer Drug Des. 12:145).
Examples of methods for the synthesis of molecular libraries can be found in the art, for example in: DeWitt et al. (1993) Proc. Natl. Acad. Sci. USA 90:6909; Erb et al. (1994) Proc. Natl. Acad. Sci. USA 91:11422; Zuckermann et al. (1994). J. Med. Chem. 37:2678; Cho et al. (1993) Science 261:1303; Carrell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2059; Carell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2061; and Gallop et al. (1994) J. Med. Chem. 37:1233.
Libraries of compounds may be presented in solution (e.g., Houghten (1992) Bio Techniques 13:412), or on beads (Lam (1991) Nature 354:82), chips (Fodor (1993) Nature 364:555), bacteria (U.S. Pat. No. 5,223,409), spores (U.S. Pat. Nos. 5,571,698; 5,403,484; and 5,223,409), plasmids (Cull et al. (1992) Proc. Natl. Acad. Sci. USA 89:1865) or phage (Scott and Smith (1990) Science 249:386; Devlin (1990) Science 249:404; Cwirla et al. (1990) Proc. Natl. Acad. Sci. USA 87:6378; and Felici (1991) J. Mol. Biol. 222:301).(United States Patent Application 20020103360)
An agent effective i in suppressing expression of overexpressed genes is deemed to lead to a clinical benefit such compounds are further tested for the ability to prevent cancer cell growth.
Differences in the genetic makeup of individuals can result in differences in their relative abilities to metabolize various drugs. An agent that is metabolized in a subject to act as an anti-cell lung cancer agent can manifest itself by inducing a change in gene expression pattern in the subject's cells from that characteristic of a cancerous state to a gene expression pattern characteristic of a non-cancerous state. Accordingly, the differentially expressed LC sequences disclosed herein allow for a putative therapeutic or prophylactic anti-lung cancer agent to be tested in a test cell population from a selected subject in order to determine if the agent is a suitable ant lung cancer agent in the subject.
To identify an anti-lung cancer agent, that is appropriate for a specific subject, a test cell population from the subject is exposed to a therapeutic agent, and the expression of one or more of LC 1-461 sequences is determined. For example a test cell population is incubated in the presence of a candidate agent and the pattern of gene expression of the test sample is measured and compared to one or more reference profiles, e.g., a non-lung cancer reference expression profile or an lung cancer reference expression profile.
A decrease in expression of one or more of the sequences LC 1-461 oin a test cell population relative to a reference cell population containing non-lung cancer is indicative that the agent is therapeutic.
The test cell population is any cell expressing the lung cancer-associated genes. For example, the test cell population contains an epithelial cell. For example, the test cell is immortalized cell line derived from a lung cancer cell.
The test agent can be any compound or composition.
Kits
The invention also includes an Lkb1 or LC-detection reagent, e.g., a nucleic acid that specifically binds to or identifies one or more NSC nucleic acids such as oligonucleotide sequences, which are complementary to a portion of a Lkb1 or LC nucleic acid or antibodies which bind to proteins encoded by a Lkb1 or LC nucleic acid. The reagents are packaged together in the form of a kit. The reagents are packaged in separate containers, e.g., a nucleic acid or antibody (either bound to a solid matrix or packaged separately with reagents for binding them to the matrix), a control reagent (positive and/or negative), and/or a detectable label. Instructions (e.g., written, tape, VCR, CD-ROM, etc.) for carrying out the assay are included in the kit. The assay format of the kit is a Northern hybridization or a sandwich ELISA known in the art.
For example, Lkb1 or LC detection reagent, is immobilized on a solid matrix such as a porous strip to form at least one Lkb1 or LC detection site. The measurement or detection region of the porous strip may include a plurality of sites containing a nucleic acid. A test strip may also contain sites for negative and/or positive controls. Alternatively, control sites are located on a separate strip from the test strip. Optionally, the different detection sites may contain different amounts of immobilized nucleic acids, i.e., a higher amount in the first detection site and lesser amounts in subsequent sites. Upon the addition of test sample, the number of sites displaying a detectable signal provides a quantitative indication of the amount of Lkb1 or LC present in the sample. The detection sites may be configured in any suitably detectable shape and are typically in the shape of a bar or dot spanning the width of a teststrip.
Alternatively, the kit contains a nucleic acid substrate array comprising one or more nucleic acid sequences. The nucleic acids on the array specifically identify one or more nucleic acid sequences represented by LKB1 ore LC 1-461. The expression of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 40 or 50 or more of the sequences represented by LC 1-461 are identified by virtue if the level of binding to an array test strip or chip. The substrate array can be on, e.g., a solid substrate, e.g., a “chip” as described in U.S. Pat. No.5,744,305.
Arrays and Pluralities
The invention also includes a nucleic acid substrate array comprising one or more nucleic acid sequences. The nucleic acids on the array specifically corresponds to one or more nucleic acid sequences represented by LC 1-461. The level expression of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 40 or 50 or more of the sequences represented by LC 1-461 are identified by detecting nucleic acid binding to the array.
The invention also includes an isolated plurality (i.e., a mixture if two or more nucleic acids) of nucleic acid sequences. The nucleic acid sequence are in a liquid phase or a solid phase, e.g., immobilized on a solid support such as a nitrocellulose membrane. The plurality includes one or more of the nucleic acid sequences represented by LC 1-461. In various embodiments, the plurality includes 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 40 or 50 or more of the sequences represented by LC 1-461
Chips
The DNA chip is a device that is convenient to compare expression levels of a number of genes at the same time. DNA chip-based expression profiling can be carried out, for example, by the method as disclosed in “Microarray Biochip Technology ” (Mark Schena, Eaton Publishing, 2000), etc.
A DNA chip comprises immobilized high-density probes to detect a number of genes. Thus, expression levels of many genes can be estimated at the same time by a single-round analysis. Namely, the expression profile of a specimen can be determined with a DNA chip. The DNA chip-based method of the present invention comprises the following steps of:
(1) synthesizing cRNAs or cDNAs corresponding to the marker genes;
(2) hybridizing the cRNAs or cDNAs with probes for marker genes; and
(3) detecting the cRNA or cDNA hybridizing with the probes and quantifying the amount of mRNA thereof.
The cRNA refers to RNA transcribed from a template cDNA with RNA polymerase. A cRNA transcription kit for DNA chip-based expression profiling is commercially available. With such a kit, cRNA can be synthesized from T7 promoter-attached cDNA as a template by using T7 RNA polymerase. On the other hand, by PCR using random primer, cDNA can be amplified using as a template a cDNA synthesized from mRNA.
On the other hand, the DNA chip comprises probes, which have been spotted thereon, to detect the marker genes of the present invention. There is no limitation on the number of marker genes spotted on the DNA chip. For example, it is allowed to select 5% or more, preferably 20% or more, more preferably 50% or more, still more preferably 70% or more of the marker genes of the present invention. Any other genes as well as the marker genes can be spotted on the DNA chip. For example, a probe for a gene whose expression level is hardly altered may be spotted on the DNA chip. Such a gene can be used to normalize assay results when assay results are intended to be compared between multiple chips or between different assays.
A probe is designed for each marker gene selected, and spotted on a DNA chip. Such a probe may be, for example, an oligonucleotide comprising 5-50 nucleotide residues. A method for synthesizing such oligonucleotides on a DNA chip is known to those skilled in the art. Longer DNAs can be synthesized by PCR or chemically. A method for spotting long DNA, which is synthesized by PCR or the like, onto a glass slide is also known to those skilled in the art. A DNA chip that is obtained by the method as described above can be used for diagnosing a disease X according to the present invention.
The prepared DNA chip is contacted with cRNA, followed by the detection of hybridization between the probe and cRNA. The cRNA can be previously labeled with a fluorescent dye. A fluorescent dye such as Cy3(red) and Cy5 (blue) can be used to label a cRNA. cRNAs from a subject and a control are labeled with different fluorescent dyes, respectively. The difference in the expression level between the two can be estimated based on a difference in the signal intensity. The signal of fluorescent dye on the DNA chip can be detected by a scanner and analyzed by using a special program. For example, the Suite from Affymetrix is a software package for DNA chip analysis.
Transgenic Animals
In another aspect, the present invention includes transgenic animals containing a heterologous (or exogenous) gene construct. Specifically, the invention provided a transgenic animal whose genome contains a mutant K-ras oncogene and at least one Lkb1 null allele. Optionally, animal is homozygous null for Lkb1. The animal exhibits accelerated development of a lung tumor. Preferably the K-ras mutation is a G12 D mutation.
The preparation of a transgenic mammal requires introducing a nucleic acid construct that will be used to express a nucleic acid encoding a light-generating fusion protein into an undifferentiated cell type, e.g., an embryonic stem (ES) cell. The ES cell is then injected into a mammalian embryo, where it will integrate into the developing embryo. The embryo is then implanted into a foster mother for the duration of gestation.
Embryonic stem cells are typically selected for their ability to integrate into and become part of the germ line of a developing embryo so as to create germ line transmission of the heterologous gene construct. Thus, any ES cell line that has this capability is suitable for use herein. One mouse strain that is typically used for production of ES cells is the 129J strain. A preferred ES cell line is murine cell line D3 (American Type Culture Collection catalog no. CRL 1934). The cells are cultured and prepared for DNA insertion using methods well known in the art, such as those set forth by Robertson (Robertson, In: Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, E. J. Robertson, ed., IRL Press, Washington, D.C., 1987.). Insertion of the nucleic acid construct into the ES cells can be accomplished using a variety of methods well known in the art including for example, electroporation, microinjection, and calcium phosphate treatment.
The term “transgene” is used herein to describe genetic material that has been or is about to be artificially inserted into the genome of a mammalian cell, particularly a mammalian cell of a living animal. The transgene is used to transform a cell, meaning that a permanent or transient genetic change, preferably a permanent genetic change, is induced in a cell following incorporation of an heterologous nucleic acid, such as DNA. A permanent genetic change is generally achieved by introduction of the DNA into the genome of the cell. Vectors for stable integration include plasmids, retroviruses and other animal viruses, YACs, and the like. Of interest are transgenic mammals, e.g. cows, pigs, goats, horses, etc., and particularly rodents, e.g., rats, mice, etc. Preferably, the transgenic animals are mice.
Transgenic animals comprise an heterologous nucleic acid sequence present as an extrachromosomal element or stably integrated in all or a portion of its cells, especially in germ cells. Unless otherwise indicated, it will be assumed that a transgenic animal comprises stable changes to the germline sequence. During the initial construction of the animal, “chimeras” or “chimeric animals” are generated, in which only a subset of cells have the altered genome. Chimeras are primarily used for breeding purposes in order to generate the desired transgenic animal. Animals having a heterozygous alteration are generated by breeding of chimeras. Male and female heterozygotes are typically bred to generate homozygous animals.
The heterologous gene is usually either from a different species than the animal host, or is otherwise altered in its coding or non-coding sequence. The introduced gene may be a wild-type gene, naturally occurring polymorphism, or a genetically manipulated sequence, for example having deletions, substitutions or insertions in the coding or non-coding regions. Where the introduced gene is a coding sequence, it is usually operably linked to a promoter, which may be constitutive or inducible, and other regulatory sequences required for expression in the host animal. By “operably linked” is meant that a DNA sequence and a regulatory sequence(s) are connected in such a way as to permit gene expression when the appropriate molecules, e.g., transcriptional activator proteins, are bound to the regulatory sequence(s). The transgenic animals of the invention can comprise other genetic alterations in addition to the presence of the heterologous gene. For example, the host's genome may be altered to affect the function of endogenous genes, contain marker genes, or other genetic alterations such as are described in the Examples.
Although not necessary to the operability of the invention, the transgenic animals described herein may comprise alterations to endogenous genes in addition to (the genetic alterations described above. For example, the host animals may be either “knockouts” and/or “knockins” for a target gene(s) as is consistent with the goals of the invention (e.g., the host animal's endogenous HIF1α may be “knocked out” and/or the endogenous bioluminescent fusion protein “knocked in”. Knockouts have a partial or complete loss of function in one or both alleles of an endogenous gene of interest. Knockins have an introduced transgene with altered genetic sequence and/or function from the endogenous gene. The two may be combined, for example, such that the naturally occurring gene is disabled, and an altered form introduced.
In a knockout, preferably the target gene expression is undetectable or insignificant. For example, a knock-out of an gene means that function of the gene has been substantially decreased so that expression is not detectable or only present at insignificant levels. This may be achieved by a variety of mechanisms, including introduction of a disruption of the coding sequence, e.g., insertion of one or more stop codons, insertion of a DNA fragment, etc., deletion of coding sequence, substitution of stop codons for coding sequence, etc. In some cases the exogenous transgene sequences are ultimately deleted from the genome, leaving a net change to the native sequence. Different approaches may be used to achieve the “knock-out”. A chromosomal deletion of all or part of the native gene may be induced, including deletions of the non-coding regions, particularly the promoter region, 3′ regulatory sequences, enhancers, or deletions of gene that activate expression of genes. A functional knock-out may also be achieved by the introduction of an anti-sense construct that blocks expression of the native genes (See, e.g., Li and Cohen (1996) Cell 85:319-329). “Knock-outs” also include conditional knock-outs, for example where alteration of the target gene occurs upon exposure of the animal to a substance that promotes target gene alteration, introduction of an enzyme that promotes recombination at the target gene site (e.g. Cre in the Cre-lox system), or other method for directing the target gene alteration postnatally.
A “knockin” of a target gene means an alteration in a host cell genome that results in altered expression or function of a native target gene. Increased (including ectopic) or decreased expression may be achieved by introduction of an additional copy of the target gene, or by operatively inserting a regulatory sequence that provides for enhanced expression of an endogenous copy of the target gene. These changes may be constitutive or conditional, i.e. dependent on the presence of an activator or represser. The use of knockin technology may be combined with production of exogenous sequences to produce the transgenic animals of the invention.
A selection marker can be any nucleic acid sequence that is detectable and/or assayable. Examples of selection markers include positive selection markers and negative selection markers. Positive selection markers include drug resistance genes; e.g., neomycin resistance genes or hygromycin resistance genes, or beta-galactosidase genes. Negative selection markers, e.g., thymidine kinase gene, diphtheria toxin gene and ganciclovir are useful in the heterologous gene construct in order to eliminate embryonic stem (ES) cells that do not undergo homologous recombination. The selection marker gene is usually operably linked to its own promoter or to another strong promoter from any source that will be active or can easily be activated in the cell into which it is inserted; however, the marker gene need not have its own promoter attached as it may be transcribed using the promoter of the light-generating fusion protein gene to be suppressed. In addition, the marker gene will normally have a polyA sequence attached to the 3′
“Enhancer elements” include nucleic acid sequences that are bound by polypeptides associated with transcription, and are usually in cis with the nucleic acid encoding a light-generating fusion protein. Examples of enhancer elements include cyclic AMP response elements (CRE), serum response elements (SRE), nuclear factor B (NF-κB), activator protein 1 (AP-1), serum response factor (SRF), and p53 binding sites. These enhancer elements may further include a TATA box.
The heterologous gene construct may be constitutively expressed in the transgenic mammal. The gene construct may expressed in specific tissues, e.g., the construct is under the control of a tissue-specific promoter.
EXAMPLE 1 General Methods Mouse Colony and Tumor Analysis:All mice were housed and treated in accordance with protocols approved by the institutional care and use committees for animal research at the Dana-Farber Cancer Institute and the University of North Carolina. The LSL-K-rasG12D mice (K-ras) were provided in a mixed genetic background by Dr. Tyler Jacks. All cohorts in Table I were of a similar, mixed genetic background (˜75% C57B1/6, ˜25% FVB/n and 129SvEv). Over 500 mice were analyzed in a standard manner for Table I, but CRE-treated littermates of less informative genotypes (e.g. compound heterozygotes, etc.) and animals treated with empty adenovirus are not shown in the interest of brevity. In all cases, heterozygote mice showed tumor-prone phenotypes intermediate to the wild-type and homozygous mutant animals. For CRE-expression, 5×106 pfu adenoviral-CRE (purchased from University of Iowa adenoviral core) was administered intra-nasally as previously described19,23.
Mice were sacrificed and the left lungs were dissected. The right lung and mediastinal structures were inflated with neutral buffered 10% formalin for 10 minutes and fixed in 10% formalin overnight at room temperature. Fixed tissues were embedded in paraffin, sectioned at 5 m, and Hematoxylin and eosin (H&E) stained (Department of Pathology in Brigham and Women's Hospital). Immunohistochemical analyses were performed as described36,37. The antibodies used were: CCSP (sc-9772, Santa Cruz), SPC (AB3786, Chemicon), pan-Keratin (Z0622, Dako), p63 (ab3239, Abcam), p-AMPK (2535, Cell signaling), Phospho-Acetyl-CoA Carboxylase (Ser79) (3661, Cell Signaling), and VEGFc (2712, Cell signaling).
In Vitro Analyses:Murine Embryo Fibroblasts (MEFs) cultured from day 13.5 embryos were serially passaged in DMEM (GIBCO)+10% Fetal Bovine Serum (Sigma), 50M -mercaptoethanol (Sigma), and pen/strep antibiotic (Invitrogen) on a 3T9 protocol at 21% O2. For Lkb1 replacement, late passage (P18) Lkb1−/− MEFs or A549 cells (ATCC) were transduced with either pBABE-puro, or pBABE-Lkb1 (wild-type), or pBABE-Lkb1K78I, selected with 1 g/ml puromycin for 4 days, and then harvested for RNA and protein after 4 days without selection. For conditional excision of Lkb1, Lkb1L/− MEFs were treated with 1010 PFU/mL of Adenoviral-CRE or Adenoviral-Empty for 24 hours. Cells were then passaged according to 3T9 protocol for an additional 15 days.
Western Blotting and mRNA Analysis:
Western blot assays were performed as previously described38 with antibodies against p16INK4a (M-156, Santa Cruz), Arf (ab-80, Abcam), Actin (C-1, Santa Cruz), Lkb1 (Rabbit polyclonal antibody, 1:5000 dilution), tubulin (clone DM 1A, Sigma-Aldrich Co), p63 (4892, Cell signaling). Expression of mRNA was analyzed by quantitative TaqMan real-time PCR as previously described with some modifications39. Reactions were carried out using cDNA equivalent to 80 ng RNA and performed in triplicate for each sample. 18S rRNA was used as a loading control for all reactions. Primer set for 18S (Hs99999901_s1) was purchased from Applied Biosystems; p16INK4a and Arf primers were generated as previously described39.
Soft Agar AssayParental A549 cell and A549 stable cell lines with expression of wt LKB1 and LKB1 K78I cells EGFR-expressing NIH-3T3 cells were suspended in a top layer of RPMI1640 containing 10% FBS and 0.4% Select agar (Gibco/Invitrogen) at 5,000 cells per well in triplicate in 6-well plates and plated on a bottom layer of RPMI1640 containing 10% FBS and 1% Select agar. After 2-wk culture, cells were stained with 0.5 ml of Crystal Violet for 1 hour. The colonies were then counted in triplicate wells from ten fields photographed with a 10× objective.
In Vivo Lung Seeding Assay of NSCLC Cell LinesParental A549 cell and A549 stable cell lines with expression of wt LKB1 and LKB1 K78I cells were injected into SCID mice intravenously via tail veins. After 8-week of inoculation, the mice were sacrificed and the lungs were dissected for both gross inspection and histology analysis.
Statistical AnalysisTumor-free survival and comparisons of tumor numbers and colonies in soft agar were analyzed using Graphpad Prism4. Statistical analysis were performed using nonparametric Mann-Whitney test. Comparisons of mRNA levels were made using the unpaired student t-test. All error bars indicate +/− standard error of the mean (SEM).
Microarray AnalysisTotal RNA was extracted, amplified and labeled as described (Giovanni et al) and hybridized to Mouse430A2 GeneChip Arrays (Affymetrix, Santa Clara, Calif.) representing 22690 unique transcripts. Probe level intensity CEL files were preprocessed using the Robust Multichip Average40-42 as implemented in Bioconductor (http://www.bioconductor.org/). Gene expression data were filtered using low stringency, pre-defined criteria: probe set intensity (>32 in all samples) and dynamic variation (more than 2-fold over the entire sample set). After filtering, 9239 probe sets remained upon which unsupervised 2-way hierarchical clustering was performed (We can put a reference here if we have the space: Eisen M B, Spellman P T, Brown P O, Botstein D: Cluster analysis and display of genome-wide expression patterns. Proc Natl Acad Sci USA 1998, 95(25):14863-14868). Multiple probe sets that presented the same genes were collapsed by taking the median value for that gene per array yielding 6871 unique genes, upon which 2-way hierarchical clustering was performed (
To discern the relationship among tumor suppressor lesions in lung carcinogenesis, a conditionally activatable Lox-Stop-Lox K-rasG12D (hereafter K-ras) allele19 and four conditional (L/L) or germline null (−/−) alleles: Lkb1L/L (Ref.), p53L/L (Ref.20), Ink4a/Arf −/− (Ref.21), and p16INK4a−/− (Ref.22) were intercrossed. Somatic, lung-specific K-ras activation and/or tumor suppressor inactivation was accomplished through inoculation of young adult mice (5-6 weeks of age) with adenoviral-CRE by inhalation as reported19,23. This method transduced a small percentage of pulmonary cells, predominantly of the medium airways. Animals were sacrificed at scheduled time points or for morbidity, and comprehensive autopsies performed to determine tumor number, histology, invasion and metastasis (See, Table I). Control animals of each genotype were treated with empty adenovirus, but no tumors were noted in any cohort in the absence of transient CRE expression.
Isolated K-ras activation led to tumors with high multiplicity but relatively long latency and low aggressiveness. In contrast, concomitant p16INK4a and p53 inactivation in animals lacking the activatable K-ras allele produced infrequent, but highly lethal, hemorrhagic tumors; suggesting that K-ras mutation initiates tumorigenesis while p16INK4a and p53 constrain tumor progression (See, Table I). Potent cooperation was noted between somatic K-ras activation and somatic loss of p53. In contrast to the overexpression setting, however, only modest cooperation was noted between single copy K-ras mutation and p16INK4a inactivation alone or in combination with Arf (Ink4a/Arf−/−) inactivation (See, Table I). These data demonstrate that p16 and p53 combine to suppress pulmonary tumorigenesis, but highlight a more prominent tumor suppressor role for p53 than p16INK4a or Arf in response to single-copy K-ras mutation in the lung.
Surprisingly, however, the strongest genetic interaction between any two alleles was that seen when K-ras mutation was combined with homozygous Lkb1 inactivation (See, Table I and
Time course experiments were performed to better delineate the cooperation between K-ras activation and Lkb1 loss in lung tumorigenesis. (
Local invasion or metastasis was not observed in in K-ras mice. In contrast, lung tumors from K-ras Lkb1L/L or L/− mice displayed local invasion into the pleura as well as metastases to lymph nodes and bone. Regional lymph node metastasis was observed in approximately one fourth of K-ras Lkb+/− or L/+ mice, and in the majority of K-ras LkbL/L or L/− mice (
Analysis of tumors from K-ras Lkb1L/L or L/− mice revealed distinct differences in tumor histopathology compared to tumors in the other cohorts listed in Table I. Consistent with prior reports19,24-28, all tumors from K-ras mice with or without Ink4a/Arf or p53 inactivation were of the characteristic adenocarcinoma subtype, as were tumors from p16INK4a−/−p53L/L mice. In contrast, the lungs 17 of 27 Adeno-CRE treated K-ras Lkb1L/L or L/− mice demonstrated a histology other than pure adenocarcinoma: 15 of 27 lungs harbored squamous cell carcinoma (SCC) or adenosquamous tumors (mixed) and 2 of 27 lungs showed large cell carcinoma (LCC) (
Analysis of tumors from K-ras Lkb1L/L or L/− mice revealed distinct differences in tumor histopathology compared to tumors in the other cohorts listed in Table I. Consistent with prior reports19, 24-28, all tumors from K-ras mice with or without Ink4a/Arf or p53 inactivation were of the characteristic adenocarcinoma subtype, as were tumors from p16INK4a−/−p53L/L mice. In contrast, the lungs 17 of 27 Adeno-CRE treated K-ras Lkb1L/L or L/− mice demonstrated a histology other than pure adenocarcinoma: 15 of 27 lungs harbored squamous cell carcinoma (SCC) or adenosquamous tumors (mixed) and 2 of 27 lungs showed large cell carcinoma (LCC) (
Protein expression analyses confirmed these differences in tumor histology. Squamous tumors from K-ras Lkb1L/L or L/− mice did not stain for pro-surfactant protein C (SP-C), a marker of type II pneumocytes expressed in lung adenocarcinoma, but did demonstrate strong staining for pan-keratin and p63, markers of SCC (
To study the mechanism whereby loss of Lkb1 modifies the histological versatility and malignancy of lung cancer, RNA expression profiling was performed of lung tumors with or without Lkb1 loss (
Based on gene expression, the adenocarcinomas further clustered into two groups that were specified by Lkb1 expression. Tumors A-C from K-ras Lkb1+/+ mice showed high expression of Lkb1 and several other transcripts associated with carbohydrate metabolism (e.g. Acetyl-CoA acyltransferase and lactate dehydrogenase; Cluster B). DAVID analysis32 suggested that the 235 transcripts that strongly correlated (r>0.86,) with Lkb1 expression were significantly enriched for genes involved in ATP synthesis as well as metabolism of fatty acids and carbohydrates, consistent with the known role of Lkb1 in regulating the nutrient-sensing AMPK pathway33. Correspondingly, these tumors harbored increased expression of the active, phosphorylated forms of AMPK and an AMPK target (Acetyl Co-A carboxylase or ACC) compared to tumors lacking Lkb1. The other group of adenocarcinomas, from K-ras Lkb1L/+ or L/−mice (tumors D, H and I), were characterized by reduced, but not necessarily absent, expression of Lkb1. In accord with the increased frequency metastasis of this group (Table I), these tumors also demonstrated increased expression of several genes associated with angiogenesis and/or metastasis. For example, the 461 gene cluster (r>0.65, Supp. Data File 4) surrounding Cluster C contained Nedd9, Vegf-c, lysl oxidases (Lox, Loxl1 and Loxl3), Pdgf's (A, B and C), Pdgf receptor, and MMP2. Increased Vegf-c expression was confirmed by immunohistochemical analysis (Supp.
In an effort to further delineate these disparate anti-cancer functions of Lkb1, in vitro analyses was performed. Previous reports have suggested that loss of Lkb1 and p16INK4a are mutually exclusive in human lung adenocarcinoma3, and that loss of Lkb1 attenuates expression of p16INK4a and Arf protein in response to oncogenic Ras in murine embryo fibroblasts15. Cultured murine embryo fibroblasts (MEFs) was used to examine the relationship between Lkb1 and expression of the Ink4a/Arf tumor suppressor locus. Upon culture, wild-type MEFs demonstrated a rapid increase in Lkb1 protein expression, which preceded the culture-induced expression of p16INK4a and Arf (
To investigate the INK4a/ARF-independent effects of LKB1 on metastasis, A549 cells, a human lung carcinoma cell line, that harbor a K-RAS activating mutation was and lack INK4a/ARF and LKB1 expression was used. A549 cells stably expressing equivalent LKB1 or LKB1K78I were established (
Multiple cytogenetic and molecular studies have shown that there are many genetic changes in human lung carcinomas resulting in the inactivation of tumor suppressor genes and mutation/activation of oncogenes61,62. Thus, it is virtually certain that in lung carcinomas (or other tumor types) that K-ras, EGFR, or BRAF mutants are not the sole mutation that occurs. Furthermore, these additional genetic alterations likely play important roles in the initiation and progression of tumorigenesis as well as sensitivities of the tumors to treatments. LKB1 mutations appear to be relatively common (˜25%) in NSCLC and thus, are likely to occur concurrently with K-ras, EGFR and BRAF mutations. A recent study suggested that LKB1 mutations are commonly found with K-RAS mutations in human lung cancers. It has been recently shown that Lkb1 cooperates with K-ras mutant to shorten the latency of lung tumorigenesis in the lox-stop-lox K-ras knock-in model (See, examples above). These preliminary findings will be confirmed in the tet-op K-ras G12D mouse model. This is important, as the lox-stop-lox K-ras model has a different level (endogenous level) of K-ras expression than the tet-op K-ras model (overexpression), and this might have a differential effect on tumorigenesis. Furthermore, the K-RAS locus is commonly amplified in human NSCLCs, thus suggesting K-RAS is over-expressed in this tumor type. Similarly, it will be determined whether Lkb1 deficiency will synergize with EGFR and BRAF mutations in lung tumorigenesis and if the tet-op-K-ras cohorts can serve as a positive control.
The inventors have generated and characterized the doxycycline inducible tet-op-K-ras, tet-op-EGFR, tet-op-BRAF mutant alleles Upon induced expression of K-ras, EGFR or BRAF mutant in the lung epithelial cells, these mice develop lung adenocarcinomas with a latency of 12 to 16 weeks (See. Examples above) To specifically delete the Lkb1 conditional alleles in the same lung cells that express mutant K-ras, EGFR, or BRAF, a recently generated SPC-Cre-ERT2 allele will be employed. The SPC promoter will direct the expression of the Cre-recombinase/estrogen receptor (Cre-ERT2) mutant fusion protein specifically in the lung type II pneumocytes epithelial cells (in the same cell compartment that are expressing the K-ras/EGFR/BRAF mutants. The administration of tamoxifen will activate the Cre recombinase activity. Using these unique alleles, the following 12 cohorts of mice (30 mice in each cohort) will be generated:
1. Lkb1 L/L, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2. Lkb1 L/L, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and tamoxifen: control)
3. Lkb1 L/L, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4. Lkb1 L/L, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (doxy and tamoxifen: experimental cohort)
1a. Lkb1 L/L, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2a. Lkb1 L/L, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and tamoxifen: control)
3a. Lkb1 L/L, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4a. Lkb1 L/L, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (doxy and tamoxifen: experimental cohort)
1b. Lkb1 L/L tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2b. Lkb1 L/L, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and tamoxifen: control)
3b. Lkb1 L/L, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4b. Lkb1 L/L, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (doxy and tamoxifen: experimental cohort)
At 3 weeks of age, mice from cohorts 2, 4, 2a, 4a, 2b, and 4b will be injected intraperitionally with 4 mg of tamoxifen over a 5-day period to activate the Cre-recombinase activity in the type II pneumocytes and delete the Lkb1 alleles as described above.
Mice from cohorts 3, 3a, 3b, 4, 4a, and 4b will be administered doxycycline continuously through their drinking water to activate the expression of mutant K-ras, EGFR, and BRAF. During these experiments, mice will be inspected daily Monday through Friday. Any mouse that show evidence of respiratory distress or illness will be euthanized (along with age-matched controls from the other cohorts) and subjected to analysis. To determine if the loss of Lkb1 affects overall survival of these mice, 10 mice from each cohort will be followed until it is time for them to be euthanized and a Kaplan-Meier survival curve will be generated. Of note, the person deciding which mice should be euthanized will be blinded regarding their specific genotypes. In addition to measuring effects on survival, we will also determine if loss of Lkb1 affects K-ras, EGFR, and BRAF mutant-induced tumor burden. For these studies, three mice from each cohort will be sacrificed by CO2 inhalation at 3, 6, 9, 12, 15, and 18 weeks after continuous administration for the lung tumor burden analyses and assessment of Lkb1 signaling. At the time of sacrifice, each organ from the mouse, including the heart, bones, liver, spleen, brain, kidney, and adrenal glands will be microscopically inspected for visible signs of metastases. Additionally, these organs will be fixed in formalin for subsequent detailed histological analyses. The left lung will be removed and snap-frozen in liquid nitrogen for protein, DNA, and RNA analyses. When macroscopic tumors are evident, they will be dissected out of the tumor to enable tumor specific molecular studies. The right lung (with the left main bronchus ligated with a suture) will then be inflated at 25 cm H2O pressure with 10% buffered formalin for 10 minutes via of an intratracheal catheter. The right lung will then be removed and fixed in 10% buffered formalin for 24 hours before embedding in paraffin. Serial mid-sagittal sections (5 μM thickness) will be obtained for histological analysis.
Data on the histological types, lung tumor multiplicity as well as the grade of the tumor will be tabulated on each lung. Paraffin-embedded lung is cut in to 4 um sections, stained with H&E and tumor-quantified using Bioquant software; specifically, the size and number of specific tumors are determined. Using this software, lung sections are captured in a 2× field and a line is drawn around the periphery of the lung. The software then calculates the area of the tumor (mm2). The same tools are used to determine the size of each tumor in the lung (total tumor area/total lung area×100). These measurements will be compared at different time points after Cre activation. Experiments will be performed at all six time points (5 mice of each genotype per time point).
EXAMPLE 9 Assessment of LKB1 Signaling in Lung TumorsLung tumors will be evaluated by western blot and IHC analyses to probe the activity of the known LKB1 signaling pathway. When tumors arise, they will be evaluated by IHC, using specific antibodies against LKB1 to ensure the loss of LKB1 and antibodies against P-S6 Kinase and P-S6 as readouts for activated mTOR signaling. IHC will be performed Drs. Padera, using previously described methods. Colored signal will be generated with a combined secondary antibody-peroxidase kit (Envision+; DAKO, Carpinteria, Calif.), according to the manufacturer's instructions. The slides will be evaluated the pathologists using light microscopy to select and analyze the 100×-magnification field with the highest concentration of positive-staining tumor cells with a clear background. Positive cases are defined by the presence of membrane, cytoplasmic, or nuclear staining, depending on the antigen. The grading of antigen expression is performed independently by at least two of the pathologists. The presence of positive staining in in situ lesions is noted. Scoring of invasive tumor is performed by two methods as previously described69. In the first method, scores of 0-3 are assigned according to the percentage of positive tumor cells (0=0%; 1=<25%; 2=25-50%; 3=>50%) and the intensity of staining (0=0; 1=1+; 2=2+; 3=3+). The two scores are multiplied to give an overall score of 0-9, of which 0-2 is considered negative, 3-6 moderate, and 7-9 strong staining. The second method of scoring examines the intensity of staining of tumor cells compared to adjacent normal cells. Here, the intensity of staining in greater than 50% of the tumor is compared to the intensity of staining in adjacent normal glands on the same slide and scored on a scale of 1-3, where 1=tumor staining less than normal, 2=tumor equivalent to normal and 3=tumor greater than normal. A score of 3 is considered as overexpression. The choice of the scoring method will depend on the antigen. Controls for the specificity of an antibody used for IHC will include tumor derived from xenografts that are known to express or not express a given protein as determined by western blot analysis. Data will be collected on the intensity and frequency of staining using immunohistochemistry and a semi-quantitative scoring system will be used as described above. Furthermore, tumors will be categorized as positive or negative. For example, for the first scoring method described above, scores 0-2 and 3-6 would be grouped together as “negative,” and scores 7-9 would be “positive.” The most appropriate groupings will be determined empirically for each antigen. The list of antibodies suitable for use in this analyses are listed in Table 2.
Protein, DNA and RNA will be harvested from any found tumors in the left lungs. With these reagents, the level of mutated kinase expression and autophosphorylation will be analyzed as well as the activation status of the various downstream pathways via western blot and expression analyses. The loss of Lkb1 in the tumors from the various cohorts with genotyping and western analyses will be assessed. All tumors found will also be cultured in an attempt to establish cell lines. These cell lines will greatly facilitate the in vitro signal transduction and drug sensitivity studies.
To determine whether or not the temporal sequence of genetic alterations play differential and distinct roles in the initiation and progression of lung tumorigenesis, the same experiment as outlined above with the same identical cohorts of mice above (30 mice in each cohort), but switch the sequence of Lkb1 inactivation and K-ras/EGFR/BRAF mutant induction. First doxycycline will be administered continuously through the drinking water to all the mice in the cohort. After 8 weeks on doxycycline, two treated mice from each cohort will be sacrificed and their lungs harvested for immunohistochemical staining and western analyses to confirm the expression of the K-ras, EGFR, or BRAF mutant expression and the activation of the downstream pathways. After the confirmation, the remaining 18 mice in each cohort will be injected intraperitionally with 4 mg of tamoxifen over a 5-day period to activate the Cre-recombinase activity in the nucleus to delete the Lkb1 alleles. Three mice from each cohort will be sacrificed by CO2 inhalation at 3, 6. 9, 12, 15, and 18 weeks after tamoxifen treatment for analysis. Identical analyses on these mice as outlined for the initial reverse temporal sequence will be performed.
The results from both sets of experiments will be compared directly, in particular, the histological types, lung tumor multiplicity as well as the grade of the tumor.
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- Lastly, the following mouse cohorts (30 mice per cohort) will be generated:
1. Lkb1 L/+, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2. Lkb1 L/+, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and tamoxifen: control)
3. Lkb1 L/+, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4. Lkb1 L/+, tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (doxy and yes tamoxifen: experimental cohort)
1a. Lkb1 L/+, tet-op-EGFR L858R, CCSP-rtTA,SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2a. Lkb1 L/+, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and tamoxifen: control)
3a. Lkb1 L/+, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4a. Lkb1 L/+, tet-op-EGFR L858R, CCSP-rtTA, SPC-Cre-ERT2 (doxy and tamoxifen: experimental cohort)
1b. Lkb1 L/+, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and no tamoxifen: control)
2b. Lkb1 L/+, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (no doxy and yes tamoxifen: control)
3b. Lkb1 L/+, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (doxy and no tamoxifen: control)
4b. Lkb1 L/+, tet-op-BRAF V600E, CCSP-rtTA, SPC-Cre-ERT2 (doxy and yes tamoxifen: experimental cohort)
The same experiments as outlined above for the initial cohorts to determine whether the loss of a single copy of Lkb1 (haploinsufficiency) impact on the phenotypes of the K-ras, EGFR, and BRAF mutant-driven lung tumors.
EXAMPLE 10 Use Pharmacological and Genetic Approaches to Dissect the Role of Dysregulated Pathway Caused by LKB1 Loss that are Involved in the Initiation and Progression of K-RAS, EGFR, and BRAF Lung TumorigenesisLkb1 is implicated in various aspects of cellular metabolism and polarity control. Lkb1 exerts its effects on diverse cellular functions through phosphorylation of different cellular substrates. In addition to the first identified physiological substrate of Lkb1 kinase, AMPK, 13 other AMPK-related serine/threonine kinases have been subsequently identified as Lkb1 substrates. Of these different pathways, the most characterized is the AMPK/TSC1/TSC2/mTOR signaling pathways, as this pathway is frequently activated in various types of cancers. In the preliminary studies, it was revealed in K-ras-driven lung tumors with LKB1 loss had elevated mTOR activity. The role of the activated AMPK/TSC1/TSC2/mTOR pathway caused by the loss of Lkb1 function in worsening the biological behavior of the K-ras LKB1 compound mutant lung tumors will be determined
To determine if the activated mTOR pathway is the main cause for the more aggressive phenotype seen in the K-ras/Lkb1 compound mutant lung tumors 78 mice from each of the following cohorts will be generated:
1. Tet-op-K-ras G12D, CCSP-rtTA, SPC-Cre-ERT2 (control cohort)
2. Tet-op-K-ras G12D, CCSP-rtTA, Lkb1 L/L, SPC-Cre-ERT2 (experimental cohort)
Seventy-eight mice will be used for experiments in which Lkb1 is deleted after K-ras-driven tumors are present, and the other 78 mice will be used for experiments in which Lkb1 is deleted before K-ras expression is induced. For the first set of experiments, Lkb1 will be deleted after K-ras tumors are formed.
In the experiment in which Lkb1 is deleted before K-ras expression is induced, 78 mice at 3 weeks of age from the each cohort will be injected intraperitionally with 4 mg of tamoxifen over a 5 day period to activate the Cre recombinase activity in the nucleus (deleting both alleles of LKB1 in pneumocytes in cohort 2). These tamoxifen-treated animals will be then administered doxycycline continuously through their diet to activate the expression of the mutant K-ras. Concurrently, in each cohort, 26 mice will be treated once daily with 2 mg/kg of rapamycin intraperitionally, 26 mice with 4 mg/kg of rapamycin intraperitionally and 26 mice with placebo vehicle. These dosing schedules are well established and have been shown to inhibit mTOR activity in xenograft models. Eight mice from each of the sub-cohorts will be followed until it is appropriate for them to be euthanized, and a Kaplan-Meier survival curve will be generated. To evaluate the effects of mTOR inhibition on the phenotype of the K-ras LKB1 compound mutant lung tumors, three mice from each sub-cohort will be sacrificed by CO2 inhalation following 3, 6, 9, 12, 15, and 18 weeks of doxycycline treatment. At the time of sacrifice, tumor burden, tumor histology, and inhibition of the mTOR signaling by methods outlined above will be evaluated. If possible, the mice will be sacrificed 4 hours after the administration of the last dose of the drug to ensure uniformity, as serum from the mouse will be collected at the time of harvest to assess rapamycin levels. In addition, any tumor nodules from these tumor-bearing mice will be microdissected out. PCR and southern analyses on DNA isolated from these microdissected tumors will be utilized to verify if the Lkb1 recombination indeed occurs. Furthermore, we will assess tumors via IHC and western blot analysis to document loss of LKB1 protein expression. By comparing the results from the different cohorts, it can be determined if activated mTOR pathway plays a significant role in the altered phenotype seen in the K-ras Lkb1 compound mutant mice.
The above experiments will allow for the determination of the role of activated mTOR pathway in K-ras Lkb1 mutant lung tumor initiation.
To evaluate the potential differing effects on the initiation and progression of K-ras Lkb1 compound mutant-driven lung tumorigenesis, the same experiments as outlined above will be repeated with the same identical cohorts of mice (80 mice in each cohort). Doxycycline will be administered continuously through their diet to all mice in the cohort. After 8 weeks on doxycycline, two treated mice from each cohort will be sacrificed and their lungs harvested for immunohistochemical staining and western analyses to confirm the expression of the mutant K-ras expression and the activation of the downstream pathways. After the confirmation, the remaining mice in each cohort will be injected intraperitionally with 4 mg of tamoxifen over a 5-day period to activate Cre-recombinase activity to delete the Lkb1 alleles. The remaining 78 mice from each cohort will be divided into 3 sub-cohorts and be administered placebo, rapamycin at 2 mg/kg and rapamycin at 4 mg/kg once daily as outlined above while remaining on continuous doxycycline treatment. Eight mice from each sub-cohort will be utilized to generate Kaplan-Meier survival curves. As described above, three mice from each sub-cohort will be sacrificed by CO2 inhalation following 3, 6, 9, 12, 15, and 18 weeks of doxycycline treatment. At the time of sacrifice, tumor burden, tumor histology, and inhibition of the mTOR signaling will be evaluated by methods outlined above.
As TSC1/TSC2 is directly downstream of AMPK but upstream of mTOR, if the effect seen with loss of Lkb1 in the K-ras/Lkb1 tumors is mainly due to the activated mTOR pathway, genetic inactivation of the TSC1/TSC2 complex in the K-ras lung tumors should give a similar phenotype as the K-ras Lkb1 mutant mice. A Tsc1 conditional knockout allele into lox-stop-lox K-ras conditional mouse strain (K-ras L/+) will be breed and the following colonies will be generated:
1. Tsc1 +/+, K-ras L/+
2. Tsc1 L/L, K-ras L/+
3. Tsc1 L/+, K-ras L/+
4. Lkb1 +/+, K-ras L/+
5. Lkb1 L/L, K-ras L/+
6. Lkb1 L/+, K-ras L/+
Tumors will be induced in the K-ras L/+ mice by treating the mice with a recombinant adenovirus expressing Cre recombinase (adeno-Cre) via inhalation as has been done previously. Expression of the Cre recombinase promotes a recombination event that induces expression of the mutant K-ras. In brief, when the mice are ˜7 weeks old, they will be anaesthetized with 0.013 ml/kg of Avertin solution. 5 million colony-forming units of adenoviral Cre (purchased from the University of Iowa) will be administered in a solution of MEM and CaCl2. The solution will be applied to the nares of the anesthetized mice. This procedure invariably induces tumors in M. musculus and the mice usually become ill from respiratory distress starting at about 8 weeks. During these experiments, mice will be inspected daily, Monday through Friday. Any mice that show evidence of respiratory distress or illness will be euthanized (along with age-matched controls from the other cohorts) and subjected to analysis. To determine if the loss of Tsc1 affects overall survival of these mice and directly compare the results to LKB1 loss, 10 mice from each cohort will be followed until it is time for them to be euthanized and a Kaplan-Meier survival curve will be generated. Of note, the person deciding which mice should be euthanized will be blinded regarding their specific genotypes. In addition to measuring effects on survival, it will also be determined if loss of Tsc1 affects K-ras-induced tumor burden. For these studies, five mice from each cohort will be sacrificed by CO2 inhalation at 6, 8, 12, 18, and 21 weeks after Cre administration for the lung tumor burden and immunohistochemical analyses. At the time of sacrifice, each organ from the mouse, including the heart, bones, liver, spleen, brain, kidney, and adrenal glands we be inspected macroscopically for visible signs of metastases. Additionally, these organs will be fixed in formalin for subsequent detailed histological analyses. The left lung will be removed and snap-frozen in liquid nitrogen for protein, DNA, and RNA analyses. When macroscopic tumors are evident, they will be dissected out of the tumor to enable tumor specific molecular studies. The right lung (with the left main bronchus ligated with a suture) will then be inflated at 25 cm H2O pressure with 10% buffered formalin for 10 minutes via of an intratracheal catheter. The right lungs will then be removed and fixed in 10% buffered formalin for 24 hours before embedding in paraffin. Serial mid-sagittal sections (5 μM thickness) will be obtained for histological analysis. Tumor genotyping will also be performed to confirm recombination and deletion of the Tsc1locus.
These experiments will determine if loss of Tsc1 effects K-ras mutant-induced tumorigenesis in a similar manner as Lkb1 loss. It is anticipated that loss of Tsc1 will accelerate K-ras tumorigenesis. However, these Lkb1 experiments are necessary controls for direct comparison to the impact Tsc1 loss in K-ras lung tumorigenesis.
To globally determine the effect of LKB1 in K-ras/EGFR/BRAF-driven tumorigenesis expression profiling from the RNA derived from the lung tumor nodules collected from the tumor bearing cohorts (3, 4, 3a, 4a, 3b, 4b) described above will be performed. All the tumors to be profiled will first be confirmed for the presence or absence of Lkb1 by genotyping and immunohistochemical analyses and for their precise histological classification by the three pathologists. It is anticipated that in the K-ras Lkb1 mutant cancers, there will be both adenocarcinomas and squamous cell carcinomas. RNA for profiling from 15 adenocarcinomas from K-ras alone tumors (from cohort 3) and 15 adenocarcinomas from K-ras Lkb1 −/− compound mutant tumors (from cohort 4) will be prepared. 15 lung squamous cell carcinomas from the K-ras Lkb1 mutant mouse cohorts will also be collected. It is not expected to have any lung squamous cell carcinomas from the K-ras alone cohort. 15 paired EGFR, EGFR Lkb1 −/−, BRAF, BRAF Lkb1 −/− adenocarcinomas from the other cohorts will also be collected. If tumors of other histological types emerge from these cohorts, RNA from them will be prepared (up to 15 tumors from each histological subtype) for expression profiling.
Briefly, RNA will be prepared from the mouse tumors generated from the different cohorts using the standard trizol method and digested with DNase I, and purified through the Qiagen column. The purified RNA will be sent to the Dana-Farber Cancer Institute Microarray Core Facility for expression profiling using the Affymetrix Mouse Expression Array 430A2.0 (22,626 known genes).
Data generated from each profiling will be downloaded as “cel” image files. Low-level analyses will be performed using the dChip software. These analyses will include image analysis (grid alignment, target detection, intensity extraction, and local background correction); normalization based on an invariant set and subsequent median smoothing; and model-based expression indices will be computed for each probe.
High-level analyses of the gene expression data will be performed in the R statistical computing environment. A total of approximately 105 samples (see above) will be expression-profiled to determine the transcriptional level of 22,626 known genes. Gene expression profiles between paired K-ras, EGFR, and BRAF cohorts with and without Lkb1 function will also be compared. In addition, the transcription signature of the K-ras alone driven tumors will also be compared to those driven by EGFR or BRAF alone. Specifically, we will compare gene expression profiles of: (1) K-ras, Lkb1 +/+ vs. K-ras, Lkb1 −/−, (2) EGFR, Lkb1 +/+ vs. EGFR, Lkb1 −/−, (3) BRAF, Lkb1 +/+ vs. BRAF, Lkb1 −/−, (4) K-ras, Lkb1 +/+ vs. EGFR, Lkb1 +/+ vs. BRAF, Lkb1 +/+, (5) K-ras, Lkb1 −/− vs. EGFR, Lkb1 −/− vs. BRAF, Lkb1 −/−. Both individual gene analyses and pathway analyses will be performed. For individual gene analyses, individually differentially expressed genes will be studied by performing the comparisons listed above using two-sample t-tests tailored towards micro-array analysis, e.g., using the software package SAM72,73. To control for the error rates of a large number of hypothesis tests, the False Discovery Rates will be calculated. Each cohort to be compared will have 15 tumors, and the number of genes to be compared will depend on filtering of unexpressed genes done in the low level analysis.
To assess expected power of our study, preliminary data comparing gene expression profiles of K-ras Lkb1 +/+ tumors vs. K-ras Lkb1 −/− tumors will be used to estimate the standard errors and a reasonable range of effect sizes and performed power calculations using the method of Tibshirani, which gives estimates of false discovery rates and false negative rates and which is particularly suitable, as it makes few assumptions regarding correlation and variance of genes. Power in this situation is defined as 1-FDR and depends on the mean difference between groups of logged expression values, sample size, and the number of genes that are truly significant for that effect size (for Tibshirani's method this is set equal to the number of genes called significant). Plots of FDR estimates for mean differences of 0.58, 1, 1.32, and 1.58 (corresponding to fold changes of 1.5, 2, 2.5, and 3 for the raw unlogged data) are given below.
From these plots on
Although individual gene analysis is useful, cellular processes often affect sets of genes. Traditional analyses have focused on individually highly ranked genes. However, this approach suffers from several major limitations: (1) Long lists of individually significant genes without a single encompassing theme are difficult to interpret. (2) Single gene analyses miss important pathway effects as cellular processes often affect sets of genes and individually highly ranked genes are often downstream genes, so moderate changes in many genes may give more insight into biological mechanisms than dramatic change in a single gene. (3) Individual highly ranked genes can be poorly annotated and are often not reproducible from studies to studies. Knowledge-based studies on gene sets, e.g. genetic pathways are more biologically interpretable and reproducible. Biological knowledge based pathway analysis will also be performed. Examples of candidate lung cancer pathways we will consider include the mTOR and the angiogenesis pathway as seen from our preliminary studies. Pathways will be constructed based on: (1) genes demonstrated to be associated with a particular gene ontology term; (2) genes demonstrated to be associated with a particular KEGG pathway; (3) gene lists manually assembled based on the previous literature.
Gene set enrichment analysis (GSEA), the principle component analysis, the global testing approach and logistic version of the kernel machine method can be used to test for modified regulation of entire groups of genes between samples cohorts. GSEA is suitable for comparative tests, while the others are suitable for self-contained tests. Since this pathway analysis is knowledge-based, self-contained tests are more suitable. The Principle Components Analysis method essentially performs dimension reduction by constructing weighted averages of genes comprising a pathway. Weights are based on directions of greatest variability of the genes in the pathway and can be found by finding the eigenvectors corresponding to the largest eigenvalues of the covariance matrix of the genes. Each weighted average can then be considered as a super-gene and we will test for differences in these super-genes between pathways via standard multivariate tests, the Hotelling's T2-test in the two-group comparison case and in the multiple groups setting, MANOVA. The principle component analysis is particularly suitable when the number of subjects per group is small. Both the global testing method and the kernel machine method are based on logistic regression by regression cohort status on gene expressions. The global testing method and principal components method can also show which genes, and what combination of genes, drive the difference between cohorts for each pathway. For the global testing method, influence plots are generated while for the principal components analysis method the weights used to find the super-genes indicate the relative importance of each gene in generating a difference. This can potentially elucidate the mechanisms by which a pathway is affected. The logistic analog of the kernel machine method further allows interactions among genes within a pathway when comparing different cohorts.
From the above expression profiling experiments and analyses, it is anticipated that the expression profiling will confirm that the mTOR pathways are hyper-activated in tumors without Lkb1 function. More importantly, it is also anticipated that many novel Lkb1 dependent genes and pathways that are involved in lung cancer progression and metastases will be discovered. In addition, there might be unique Lkb1 cancer relevant pathways that are activated/inactivated depending on the initial oncogenic stimuli. (For example, Lkb1 dependent pathway X is only activated in EGFR mutant driven lung tumors while Lkb1 dependent pathway Y is only activated in K-ras mutant driven lung tumors.) It is also anticipated that the expression profiling to confirm that the mTOR pathways are hyper-activated in tumors without Lkb1 function.
EXAMPLE: 11 Determination of the the Impact of Concentrated Ambient Particles (CAPs), an Environmental Insult, on Inflammation, Proliferation, Apoptosis, and LKB1 Function on K-RAS, EGFR, and BRAT Mutant MiceWith the generation of different genetically engineered mice that are prone to develop lung cancer, we now have the tools and reagents to examine the environmental interaction with these defined oncogenic stimuli and determine the role of environmental insult on lung cancer initiation and progression. Concentrated air particles (CAPs) system is a well-established and ideal model to dissect the role of air pollution in lung cancer progression through its effect on the primed lung epithelial compartment in our genetically defined lung oncogenic mouse models. It is hypothesized that prolonged CAPs exposure will cause chronic lung inflammation. The chronic lung inflammatory environment will generate reactive oxidative species leading to increased DNA damage, and genetic inactivation of important lung tumor suppressors such as LKB1, and accelerate lung tumorigenesis. The following series of experiments will test this hypothesis.
The following 6 cohorts of mice (60 mice per cohort) will be generated:
1. Tet-op-K-ras G12D, CCSP-rtTA, (no doxy: control)
2. Tet-op-K-ras G12D, CCSP-rtTA, (doxy: experimental cohort)
1a. Tet-op-EGFR L858R, CCSP-rtTA, (no doxy: control)
2a. Tet-op-EGFR L858R, CCSP-rtTA (doxy: experimental control)
1 b. Tet-op-BRAF V600E, CCSP-rtTA, (no doxy: control)
2b. Tet-op-BRAF V600E, CCSP-rtTA, (doxy: experimental)
At 10 weeks of age, mice from cohort 2, 2a, and 2b will be put on continuous doxycycline diet. All the mice from each of the cohorts will then be randomly divided into two equal groups (30 mice in each sub-cohort). One group of mice will be exposed The Harvard/EPA Ambient Particle Concentrator (HAPC) generates concentrated aerosols of outdoor air particles that can subsequently be directly delivered to animals (described below) for a total of 20 weeks. The other group will be exposed to filtered air in an identical exposure chamber.
The Harvard/EPA Ambient Fine Particle Concentrator (HAPC) will be used to expose animals to concentrated ambient fine particles (0.1-2.5 μm). Boston atmospheres typically consist of particles generated by vehicle exhaust, power plant emissions, home heating, and transported aerosols. Employment of this system allows for the direct investigation of the potential harm of “real world” particles in our genetically defined mouse models. Briefly, the HAPC used for the animal inhalation studies consists of three components: (1) a high-volume conventional impactor with a 2.5-μm cutoff size, (2) a series of three virtual impactors with a 0.1-μm cutoff size (concentrator stages I, II, and III), and (3) an animal exposure chamber. The first impactor is a high-volume conventional impactor (Fractionating Sampler, Anderson, Inc., Atlanta, Ga.) and removes particles larger than 2.5 μm operating at 5000 L/min, while smaller particles escape collection. The deflected flow of the conventional impactor is drawn through a series of three virtual Impactors. Each virtual impactor accelerates all airborne particles in a rectangular nozzle. These particles cross the deflected air streamlines, and enter a slit-shaped collection probe, while particles smaller than 0.1 μm follow the deflected streamlines, or enter the collection probe, but are unlikely to be concentrated. Particles in the size range 0.1-2.5 μm pass through the collection probe and are referred to as the minor flow (20% of the total flow). The minor flow of the third stage virtual impactor contains the concentrated aerosol. The total flow rate into the third stage is 50 L/min, and concentrated particles are supplied to the animal exposure chamber at 40 L/min. The remaining 10 L/min is used for characterization of the aerosol. The total concentration factor for the three virtual impactor stages is about 30. The concentrated air from stage III of the virtual impactor is supplied to the whole-body animal exposure unit (described below) through a manifold connection port on top of the chamber. Sham exposures are also performed in the exposure unit at the same pressure and flow rate with the air passed through a glass fiber filter (Gelman, Type A/E, Ann Arbor, Mich.) connected at the inlet of the chamber to remove particles. The filter efficiency is 99.6-99.9%. The use of the three virtual impactor stages results in a pressure drop of about 10 in H2O. The aerosol flow rate provides for a residence time in the exposure chamber of about 3.5 minutes. This residence time results in minimal particle losses on the chamber wall. The virtual impactor residence time is only a few seconds. The portable chamber for rodent concentrated air particle (CAPs) exposure has a volume of 142 L and is specially designed to fit inside a larger 1000-L stainless steel and glass outer chamber. Because the air pumping units are downstream from the concentrator/inhalation chamber, both the external chamber and the exposure chamber are operated under a negative pressure (˜10 in H2O). The chamber is designed to optimally utilize the flow rates from the concentrator to deliver the aerosol to the rodents. A manifold connection port on top of the chamber allows for direct connection to the HAPC. The unit is rectangular in shape with a grated floor to allow waste products to fall into trapezoidal waste collection areas underneath; drain valves in the bottom of the trapezoidal waste collection areas allow for removal of animal waste during exposure. A second manifold on the back of the unit is connected to a negative pressure system to maintain air exchange in the system. Up to six stainless steel wire-mesh cages (holding up to 50 animals each) can be placed into the unit at one time.
CAPs characterization will be performed weekly to ensure that there is no dramatic change in its composition during the course of the experiments using gravimetric particle mass determinations, liquid chromatography for sulfate, X-ray fluorescence for elemental analysis and thermal and optical reflectance method for elemental carbon analyses.
Mice from all the cohorts will be monitored closely for clinical signs of stress or tumors. Any mouse that shows any clinical signs of having stress or tumors will be sacrificed for analyses into the causality and nature of pathology. In addition four mice from each cohort will be sacrificed for analyses at weeks 2, 4, 8, 12, and 16 weeks post CAPs or filtered air exposure. The remaining 10 mice from each cohort are used to generate Kaplan Meier curves.
At the time of sacrifice, each organ from the mouse including the heart, lung, pancreas, liver, spleen, kidney, bladder, and intestines will be inspected macroscopically for signs of abnormality and fix them in formalin for subsequent detailed histological analyses Blood and serum from each mouse via cardiac puncture will also be collected. For the lungs, prior to fixation, bronchioalevolar lavage (BAL) will be performed to obtain fluids and cells. As described above, ligated left lung will be harvested and snap-frozen for subsequent DNA, RNA, and protein analyses. The right lung will then be inflated at 25 mm with 3% gluteraldehyde in 0.1 M cacodylte buffer to 25 cm H2O (for 15 min), then ligated and removed. This procedure would preserve the physiological air space architecture. The lungs collected from the different cohorts will be assessed for tumor burden. The tumors will also be analyzed for loss of Lkb1 via IHC and western analyses as well as activated mTOR pathway.
Bone marrow from the femurs will be harvested to generate primary bone marrow culture suspension. Metaphase spreads from these primary cells derived from the various cohorts will be prepared to quantitatively determine the frequency of chromosomal aberrations caused by chronic oxidative and mutagenic stress from the CAPs. This series of experiments will determine the potency of CAPs as a carcinogen and inducers of DNA double strand breaks.
Immuno-staining with Ki67 antibody will be performed on histological sections of the lungs and the other organs from the six cohorts harvested at the determined time points to assess the steady state rate of proliferation in response to chronic CAPs exposure in the various organs from the different cohorts. Similarly, TUNEL analyses will be performed to determine the steady state rate of apoptosis.
The steady state level of the lung and the circulating pro-inflammatory cytokines including IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12(p70), TNFα, IFNγ and GM-CSF will be quantitatively determined using the Upstate Beadlyte®/Luminex® multiplex mouse multi-cytokine detection system which allowed for sensitive and accurate measurement of all the above cytokine simultaneously in a small volume of serum.
As the temporal relationship between environmental exposure to CAPs and oncogene activation might be important to lung tumorigenesis and progression. Thus, the experiments described above will be repeated in a different temporal sequence. Using the same cohorts of animals as described above, animals in the different cohorts we be chronically exposed the either to CAPs or filtered air starting at 3 weeks of age. After 20 weeks of exposure, all the mice will be placed on filtered air, and the mice in 2, 2a, and 2b will be put on continuous doxycycline diet. This set of experiment will address the impact of existing chronic lung inflammation caused by environmental insult (CAPs) on oncogene-driven lung tumorigenesis.
Lastly, if there are major differences in the between the CAPs exposed mouse cohorts and the control cohorts in either the latency, aggressiveness or the histology of lung tumors, the tumors from each of the cohorts will be isolated and similar expression profiling analyses will be performed as detailed above to determine the pathways that are de-regulated as a result of the CAPs exposure.
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While the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.
Claims
1. A method for determining the aggressiveness of a lung cancer in a mammal, said method comprising determining, in a test sample from said mammal, the presence or absence of Lkb1 and correlating said presence or absence with said aggressiveness.
2. The method of claim 1, wherein said mammal is a human.
3. The method of claim 1, wherein said test sample is a tumor biopsy.
4. The method of claim 1, wherein said absence of said Lkb1 or decrease of the activity of said Lkb1 indicates said cancer is aggressive.
5. The method of claim 1, wherein said presence of said intact Lkb1 indicates said cancer is not aggressive.
6. The method of claim 1, wherein said absence of said Lkb1 or decrease of the activity of said Lkb1 indicates said cancer is metastatic.
7. The method of claim 1, further comprising determining the presence or absence of a mutation in K-ras, EGFR or BRAF.
8. A method of assessing the efficacy of a m-TOR inhibitor for treating or inhibiting the growth of lung cancer in a patient, comprising detecting inactivation of Lkb1 gene expression in a lung cancer tumor from a subject, wherein said inactivation of Lkb1 gene expression in the lung cancer tumor indicates treatment with an m-TOR inhibitor is efficacious.
9. A method of diagnosing lung cancer or a predisposition to developing lung cancer in a subject, comprising determining a level of expression of an lung cancer-associated gene in a patient derived tissue sample, wherein an increase of said level compared to a normal control level of said gene indicates that said subject suffers from or is at risk of developing lung cancer.
10. The method of claim 9, wherein said lung cancer-associated gene is selected from the group consisting of LC 1-461, wherein an increase in said level compared to a normal control level indicates said subject suffers from or is at risk of developing lung cancer.
11. The method of claim 9, wherein said increase is at least 10% greater than said normal control level.
12. The method of claim 9, wherein said method further comprises determining said level of expression of a plurality of lung cancer-associated genes.
13. A lung cancer reference expression profile, comprising a pattern of gene expression of two or more genes selected from the group consisting of LC 1-461.
14. A kit comprising a detection reagent which binds to two or more nucleic acid sequences selected from the group consisting of LC 1-461.
15. An array comprising a nucleic acid which binds to two or more nucleic acid sequences selected from the group consisting of LC 1-461.
16. A transgenic animal whose genome comprises a mutant K-ras oncogene and at least one Lkb1 null allele, wherein said transgenic animal constitutively expresses a mutated K-ras protein in at least one tissue and exhibits accelerated development of a lung tumor.
17. The transgenic animal of claim 16 in which said animal is homozygous null for Lkb1.
18. The transgenic animal of claim 16, wherein said K-ras oncogen contains a G12D mutation.
Type: Application
Filed: Feb 4, 2008
Publication Date: May 19, 2011
Inventors: Kwok-Kin Wong (Arlington, MA), Bruce Johnson (Arlington, MA), Pasi Janne (Arlington, MA), Hongbin Ji (Arlington, MA), Nabeel Bardeesy (Arlington, MA), Norman Sharpless (Arlington, MA)
Application Number: 12/449,404
International Classification: A01K 67/033 (20060101); G01N 33/574 (20060101); C12Q 1/68 (20060101); C40B 40/06 (20060101); C40B 30/04 (20060101);
