Diagnosing and Monitoring CNS Malignancies Using MicroRNA
The use of specific microRNAs (miRNAs) present in CSF as biomarkers for particular brain malignancies and disease activity.
This application is a continuation of U.S. patent application Ser. No. 13/885,762, filed May 16, 2013, which is a U.S. National Phase Application under 35 U.S.C. §371 of International Patent Application No. PCT/US2011/061047, filed on Nov. 16, 2011, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/457,000, filed on Nov. 16, 2010. The entire contents of the foregoing are hereby incorporated by reference in their entireties.FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
This invention was made with Government support under Grant Nos. CA023100, CA124804, and CA138734 awarded by the National Institutes of Health. The Government has certain rights in the invention.TECHNICAL FIELD
The present methods relate to the use of specific microRNAs (miRNAs) that are present in CSF as biomarkers for particular brain malignancies and disease activity.BACKGROUND
The most frequently occurring brain malignancies in adults are metastatic brain cancers (e.g., from primary melanoma, lung cancer, breast cancer, gastrointestinal cancer (e.g., pancreatic or colorectal), kidney cancer, bladder cancer, certain sarcomas, or testicular or germ cell tumors) followed by glioblastoma (GBM). GBM is the most aggressive primary brain cancer, which generally has a poor prognosis with median survival of about 14 months, despite aggressive treatment (Filippini et al. Neuro Oncol. 2008; 10(0):79-87). Currently diagnosis of brain tumors is made with brain biopsy if possible and the analysis of cerebrospinal fluid (CSF) for the presence of cancer cells (cytology). CSF can be accessed readily for longitudinal disease monitoring during and after therapy. However, the currently used method of CSF analysis has moderate sensitivity, is non-quantitative and technically challenging. There is presently no routine way to subtype the malignancy and monitor molecular changes from CSF indicating the need for more accurate and reliable biomarkers and methods.SUMMARY
The present invention is based on the identification of specific miRNAs that can serve as biomarkers for particular brain malignancies and disease activity.
Thus, in a first aspect, the invention provides methods for detecting or making a diagnosis between metastatic and primary brain tumors. The methods include determining levels of miR-10b, miR-21, and miR-200 in a sample from a subject, and comparing the levels of miR-10b, miR-21, and miR-200 to reference levels of miR-10b, miR-21, and at least one miR-200 family member. The presence of levels of all of miR200, miR-10b or miR-21 below the reference levels indicates the absence of a metastatic or primary brain tumor. The presence of levels of miR-10b or miR-21 above the reference levels indicates the presence of a metastatic or primary brain tumor. The presence of levels of the miR-200 family member above the reference level indicates the presence of a metastatic brain tumor.
In another aspect, the invention provides computer-implemented methods for detecting or making a diagnosis between metastatic and primary brain tumors. The methods include determining levels of miR-10b, miR-21, and at least one miR-200 family member, in a sample from a subject, to provide a subject dataset; downloading the dataset into a computer system having a memory, an output device, and a processor programmed for executing an algorithm, wherein the algorithm assigns the datasets into one of two categories levels of miR-10b, miR-21, and at least one miR-200 family member; assigning the subject dataset into the first or second category; and generating an output comprising a report indicating the assignment to the first or second category.
In some embodiments, the first category is presence of a primary brain tumor and the second category is presence of a metastatic brain tumor. In some embodiments, an assignment to the first category is made based on the presence of levels of miR-10b or miR-21 above reference levels, and the presence of levels of the miR-200 family member below a reference level; and an assignment to the second category is made based on the presence of levels of miR-10b or miR-21 above reference levels, and the presence of levels of the miR-200 family member above the reference level.
In some embodiments, the first category is presence of a primary brain tumor or a metastatic brain tumor, and the second category is absence of a primary brain tumor or a metastatic brain tumor. In some embodiments, an assignment to the first category is made based on the presence of any of miR200, miR-10b or miR-21 above reference levels, and an assignment to the second category is made based on the presence of levels of all of miR200, miR-10b or miR-21 below the reference levels.
In some embodiments, the algorithm is a linear algorithm or radial basis function.
In some embodiments, the algorithm is a linear algorithm comprising:
(a*miR-125b)+(b*miR-10b)+(c*miR-21)+(d*miR-141)+(e*miR-200a)+(f*miR-200b)+(g*miR-200c)−h, wherein a-g are weights and h is a constant, determined using a support vector machine algorithm.
In some embodiments, the methods further include selecting a treatment for a metastatic or primary brain tumor for the subject, based on the presence of a metastatic or primary brain tumor.
In some embodiments, the methods further include administering the treatment to the subject.
In another aspect, the invention provides methods for monitoring progression of a brain tumor. The methods include determining levels of one or more of miR-10b, miR-21, and a miR-200 family member in a first sample; and determining levels of one or more of miR-10b, miR-21, and a miR-200 family member in a subsequent sample. The presence of levels of miR-10b, miR-21, or miR-200 family member in the subsequence sample above the levels in the first sample indicates the presence of progression or recurrence of the brain tumor, and levels of miR-10b miR-21, or miR-200 family member in the subsequent sample below the levels in the first sample indicates that the brain tumor is regressing or is in remission.
In some embodiments, wherein the subject has been diagnosed with a primary brain tumor, the methods include monitoring levels of one or both of miR-10b and miR-21. In some embodiments, wherein the subject has been diagnosed with a metastatic brain tumor, the methods include monitoring levels of one or more of miR-10b, miR-21, and a miR-200 family member.
In some embodiments, the methods further include administering a treatment to the subject, e.g., between the first and subsequent samples, and a decrease in levels of miR-10b, miR-21, or at least one miR-200 family member in the subsequence sample as compared to the level in the first sample indicates that the treatment was effective, e.g., reduced the size of the tumor. No change indicates that the treatment either halted tumor growth or had no effect, and an increase indicates that the treatment was not effective.
In some embodiments, the treatment includes administration of one or more of surgical resection, chemotherapy, or radiotherapy.
In some embodiments of the methods described herein, the sample comprises cerebrospinal fluid from a subject.
In some embodiments of the methods described herein, the subject is a human who has or is suspected of having a brain tumor.
In some embodiments of the methods described herein, the levels are determined using RT-PCR.
In some embodiments of the methods described herein, the miR-200 family member is miR-200a, miR-200b, miR-200c, miR-141, or miR-429.
In some embodiments of the methods described herein, the method comprises normalizing the levels to a level of a housekeeping miRNA, e.g., miR-125 or miR-24.
In some embodiments of the methods described herein, the primary brain tumor is a glioma, glioblastoma, hemangioma, or medulloblastoma.
In some embodiments of the methods described herein, the metastatic brain tumor is from a primary lung, breast, kidney, bladder, testicular, germ cell or gastrointestinal cancer, or melanoma.
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. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.
Other features and advantages of the invention will be apparent from the following detailed description and figures, and from the claims.
miRNAs are small endogenous mediators of RNA interference and key regulatory components of many biological processes required for organism development, cell specialization and homeostasis. Many miRNAs exhibit tissue-specific patterns of expression and are deregulated in various cancers, where they can either be oncogenic (oncomirs) or tumor suppressive. The recent discovery of miRNAs in the secreted membrane vesicles, exosomes2, 3, as well as in the blood serum4, 5 and other body fluids6 suggested that miRNAs play a role in intercellular communication in both paracrine and endocrine manner. It had also opened a new exciting direction for study of miRNAs as biomarkers for diseases, and cancer diagnostics by miRNA profile in blood serum became a quickly growing field7.
Several studies have reported miRNA detection, among several biological fluids, in CSF8-10, raising the possibility that miRNAs in CSF might serve as informative biomarkers of central nervous system (CNS) disease. Such a possibility, largely unexplored until now, is supported by the finding that different types of brain cancer have distinct signatures of miRNA expression, with some miRNAs species abundant in cancer while undetectable in healthy brain11-13. Since CSF is separated from blood circulation by blood-brain barrier, it is conceivable that CSF might better retain a unique signature of miRNA expression specific for brain tumors.
A recent study demonstrated the usefulness of miRNA profiling in CSF for diagnostics of brain lymphoma10. In the current study, levels of several candidate miRNAs were tested in the CSF of patients with GBM and compared to those of metastatic brain cancers and a variety of non-neoplastic CNS diseases. There was a strong association between the particular types of brain cancer and the presence of specific miRNAs in CSF. Using this approach enables detection of GBM and metastatic brain cancers, and discrimination between them with about 95% accuracy. These results demonstrate the utility of miRNA as biomarkers of high-grade brain malignancies and reveal their value for the development of diagnostic and prognostic tools, as well as for monitoring of CNS pathology in general.
Methods of Diagnosis/Detection of CNS Malignancies
Thus, the methods described herein can be used to diagnose, i.e., detect the presence of, a CNS malignancy, based on levels of miRNAs in CSF, e.g., levels of one or more of miR-21, miR-10b, and or a miR-200 (as used herein, the term “miR-200” encompasses all members of the miR-200 family, i.e., miR-200a, miR-200b, miR-200c, miR-141, and miR-429). In some embodiments, levels of miR-10b are determined and compared to a reference level, and the presence of levels of miR-10b in the subject above the reference level indicates that the subject has a metastatic or neoplastic primary brain tumor, e.g., GBM. In some embodiments, levels of miR-200 are determined and compared to a reference level, and the presence of levels of miR-200 (e.g., miR-200a) in the subject above the reference level indicates that the subject has a metastatic brain tumor, e.g., from primary lung or breast cancer. In some embodiments, levels of miR-21 are determined and compared to a reference level, and the presence of levels of miR-21 in the subject above the reference level indicates that the subject has a metastatic or neoplastic primary brain tumor, e.g., GBM. In some embodiments, the methods include determining levels of miR-10b or miR-21 and miR-200 (either non-normalized or normalized to relatively uniformly expressed miRNAs such as miR-125 or miR-24), and comparing the levels of each miRNA to a reference level. In this case, the presence of elevated miR-10b or miR-21 indicates the presence of a metastatic or neoplastic primary brain tumor, e.g., GBM, and the presence of miR-200 indicates the presence of a metastatic brain tumor. See, e.g.,
In some embodiments, the methods are used to determine whether a metastatic brain tumor originated from a primary breast or lung tumor. The methods include detecting levels of miR-200a and/or miR-200b. The presence of increased levels of miR-200a and miR-200b (two miRNAs encoded as a cluster at chromosome 1p36.33) in CSF indicate an increased likelihood of the presence of metastatic breast cancer relative to lung cancer. In some embodiments, the methods include determining CSF levels of miR-141 and -200c (co-encoded at chromosome 12p13.31), which are expressed at similar levels in breast and lung cancer cases, and determining a ratio between the miRNAs of the two different miR-200 genomic clusters (e.g., [level of miR200a+level of miR200b]/[level of miR141+miR200c], wherein a ratio above a reference ratio indicates an increased likelihood of the presence of metastatic breast cancer relative to lung cancer.
In some embodiments, the methods are used to make a differential diagnosis of GBM versus brain metastasis, or GBM and brain metastasis versus non-neoplastic tumors on the basis of detection of levels in a CSF sample of seven miRNAs: miR-10b, miR-21, miR-125b, miR-141, miR-200a, miR-200b, and miR-200c as independent variables. Each of these miRNAs is detected in the sample, and an algorithm (e.g., a linear or radial is applied to make a diagnosis.
Reference levels can be determined using methods known in the art, e.g., standard epidemiological and biostatistical methods. The reference level can represent the levels in a reference cohort, e.g., levels in subjects who do not have GBM or metastatic brain cancer. The reference levels can be, e.g., median levels, or levels representing a cutoff for the highest quartile, and can be set to provide sufficient specificity and accuracy to provide for an optimal level of true positives/true negatives while minimizing levels of false positives/false negatives. Appropriate methods are known in the art. See, e.g., Fleiss, “Design and Analysis of Clinical Experiments,” (Wiley-Interscience; 1 edition (Feb. 22, 1999)); Lu and Fang, “Advanced Medical Statistics,” (World Scientific Pub Co Inc (Mar. 14, 2003)); Armitage et al., “Statistical Methods in Medical Research, 4th Ed”, Blackwell Science (Boston, Mass., Oxford: Blackwell Scientific Publications, 2001).
In some embodiments, the methods include determining levels of miR-125b, and normalizing levels of other miRNAs to the levels of miR-125b, see, e.g.,
In some embodiments, miRNA levels are determined after an initial diagnosis of a brain mass, e.g., detection of a mass using an imaging method such as MM, or after a subject has presented with symptoms that are consistent with a brain mass, to assist in making a differential diagnosis of GBM versus brain metastasis versus non-neoplastic tumor. A health care provider can identify subjects who have symptoms consistent with a brain mass based on knowledge in the art; general signs and symptoms include new onset or change in pattern of headaches; headaches that gradually become more frequent and more severe; unexplained nausea or vomiting; vision problems, such as blurred vision, double vision or loss of peripheral vision; gradual loss of sensation or movement in an arm or a leg; difficulty with balance; speech difficulties; confusion in everyday matters; personality or behavior changes; seizures, especially in someone who doesn't have a history of seizures; and hearing problems.
In some embodiments, once a differential diagnosis is made, the methods include the selection and optionally the administration of a treatment for the diagnosed disease. Thus, the methods can include selecting a treatment regimen for the subjects comprising one or more of surgical intervention, chemotherapy, and radiotherapy. For all brain cancers, the choice of therapy (e.g., surgery, radiation and/or chemotherapy) can be chosen depending on site, size, neurological function, and systemic disease status. For example, if the subject has GBM, then a treatment regime including radiation, temozolamide, and avastin may be selected and optionally administered. If the subject has metastatic brain cancer, then the treatment may depend on the source of the metastasis, i.e., on the primary cancer. For metastatic breast cancer, then the treatment could include chemotherapies approved for breast cancer (e.g., herceptin, lapatinib, doxil, or taxanes); for lung metastases, then lung cancer therapies can be selected (e.g., tarceva, alimta, or carboplatin). One of skill in the art would be able to select an appropriate treatment based on knowledge in the art. See, e.g., the National Comprehensive Cancer Network (NCCN) Guidelines, available on the internet at nccn.org.
For a subject who has been determined to have a non-neoplastic lesion using a method described herein, the methods can include monitoring the subject on a continuing basis to detect any change in the lesion, e.g., a shift to malignancy, which would be indicated by an increase in levels of miR-10b, miR-21, or miR-200.
Methods of Monitoring CNS Malignancies
The methods described herein can also be used to monitor a subject, e.g., a subject who is undergoing treatment or being followed for progression. The methods include determining levels of miR-10b, miR-21, and/or miR-200, wherein the presence of levels of miR-10b, miR-21, or miR-200 above a reference level indicate the presence of recurrence of the malignancy, and levels below the reference level indicate that the subject is in remission.
In some embodiments, e.g., for a subject who is undergoing treatment, levels of miR-10b, miR-21, and/or miR-200 can be monitored over time (e.g., by comparing levels determined from first and second, e.g., subsequent, samples taken over time; the first sample can be, but need not be, a baseline or initial sample); a decrease in levels of miR-10b, miR-21, and/or miR-200 in a subject undergoing treatment indicates that the treatment is effective. An increase in levels indicates progression. No significant change in levels indicates that no significant change has occurred, i.e., no significant change in a subject being treated that the treatment is at best slowing growth of the tumor, or is ineffective, and no significant change in a subject who is not being treated indicates that the tumor is not progressing. The presence of elevated levels in a subject who was previously in remission indicates the presence of a recurrence of the tumor, and can indicate a need for treatment.
In addition, the methods can be used to detect real progression versus pseudoprogression (a phenomenon in which a subject is observed to have experienced disease growth immediately after therapy, e.g., after radiotherapy, but are later shown to have improved or stable disease by brain imaging, see, e.g., Hoffman et al., J Neurosurg 50:624-628, 1979; Brandes et al., Clin Oncol 26:2192-2197, 2008; de Witt et al., Neurology 63:535-537, 2004; Taal et al., Cancer 113:405-410, 2008), e.g., in subjects with GBM. In the case of an apparent progression (e.g., as measured by imaging), the presence of stable or decreasing levels of miR-10b (or miR-200) as compared to earlier levels (e.g., pre-treatment levels) indicates that the apparent progression is a pseudoprogression.
The levels can be determined, e.g., before, during, or after treatment, e.g., treatment with surgery (e.g., resection or debulking), chemotherapy, or radiotherapy.
Methods of Detection
Any methods known in the art can be used to detect and/or quantify levels of a miRNA as described herein. For example, the level of a miRNA can be evaluated using methods known in the art, e.g., RT-PCR (e.g., the TAQMAN miRNA assay or similar), quantitative real time polymerase chain reaction (qRT-PCR), Northern blotting, RNA in situ hybridization (RNA-ISH), RNA expression assays, e.g., microarray analysis, deep sequencing, cloning or molecular barcoding (e.g., NANOSTRING, as described in U.S. Pat. No. 7,473,767). Analytical techniques to determine miRNA levels are known. See, e.g., Sambrook et al., Molecular Cloning: A Laboratory Manual, 3rd Ed., Cold Spring Harbor Press, Cold Spring Harbor, N.Y. (2001).
In some embodiments, the methods include contacting an agent that selectively binds to a biomarker, e.g., to a miRNA (such as an oligonucleotide probe that binds specifically to the miRNA) with a sample, to evaluate the level of the miRNA in the sample. In some embodiments, the agent bears a detectable label. The term “labeled,” with regard to an agent encompasses direct labeling of the agent by coupling (i.e., physically linking) a detectable substance to the agent, as well as indirect labeling of the agent by reactivity with a detectable substance. Examples of detectable substances are known in the art and include chemiluminescent, fluorescent, radioactive, or colorimetric labels. For example, detectable substances can include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, bioluminescent materials, and radioactive materials. Examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, beta-galactosidase, or acetylcholinesterase; examples of suitable prosthetic group complexes include streptavidin/biotin and avidin/biotin; examples of suitable fluorescent materials include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride, quantum dots, or phycoerythrin; an example of a luminescent material includes luminol; examples of bioluminescent materials include luciferase, luciferin, and aequorin, and examples of suitable radioactive material include 125I, 131I, 35S or 3H.
In some embodiments, high throughput methods, e.g., arrays (e.g., TAQMAN Array MicroRNA Cards) or gene chips as are known in the art (see, e.g., Ch. 12, “Genomics,” in Griffiths et al., Eds. Modem genetic Analysis, 1999,W. H. Freeman and Company; Ekins and Chu, Trends in Biotechnology, 1999;17:217-218; MacBeath and Schreiber, Science 2000, 289(5485):1760-1763; Hardiman, Microarrays Methods and Applications: Nuts & Bolts, DNA Press, 2003), can be used to detect the presence and/or level of a miRNA.
In some embodiments, the methods include using a modified RNA in situ hybridization technique using a branched-chain DNA assay to directly detect and evaluate the level of a miRNA in the sample (see, e.g., Luo et al., U.S. Pat. No. 7,803,541B2, 2010; Canales et al., Nature Biotechnology 24(9):1115-1122 (2006); Nguyen et al., Single Molecule in situ Detection and Direct Quantiication of miRNA in Cells and FFPE Tissues, poster available at panomics.com/index.php?id=product_87). A kit for performing this assay is commercially-available from Affymctrix (VicwRNA).
Human miRNA Sequences
The following table sets forth sequences for mature human miRNAs useful in the present methods.
Algorithms and Computer-Implemented Methods
In some embodiments, the methods include using one or more algorithms to assign a diagnosis, based on levels of miRNAs as described herein. For example, the methods can include the use of a linear algorithm, in which one or more of the levels are weighted. In another example, the methods can include the use of a radial basis function (RBF). Appropriate linear and RBF algorithms useful in the present methods can be generated using methods known in the art, e.g., a support vector machine (SVM). The SVM was originally developed by Boser, Guyon and Vapnik (“A training algorithm for optimal margin classifiers”, Fifth Annual Workshop on Computational Learning Theory, Pittsburgh, ACM (1992) pp. 142-152). See, e.g., Vapnik, “Statistical Learning Theory.” John Wiley & Sons, Inc. 1998; Cristianini and Shawc-Taylor, “An Introduction to Support Vector Machines and other kernel-based learning methods.” Cambridge University Press, 2000. ISBN 0-521-78019-5; and Scholkopf and Smola, “Learning with Kernels.” MIT Press, Cambridge, Mass., 2002, as well as U.S. Pat. Nos. 7,475,048 and 6,882,990, all of which are incorporated herein by reference in their entirety for their teachings relating to computer systems and SVM-based methods. For example, the present methods can be performed using a computer system as described in
The invention is further described in the following examples, which do not limit the scope of the invention described in the claims.
Materials and Methods
The following materials and methods were used in Examples 1-5, below.
Collection of samples. CSF and brain tumor samples were obtained from the Department of Neurosciences, UC San Diego, Moores Cancer Center, La Jolla, Calif., Department for Neurosurgery at Brigham and Women's Hospital, Boston, Mass., and from the Department for Neurosurgery at Göttingen University Medical Center, Göttingen, Germany over the period of 2-5 years. At least one ml of each CSF sample was cleared of cells and debris immediately after collection by brief centrifugation at 3000 rpm 5 min at 4° C. and stored in aliquots at −80° C. All tumor specimens were fresh-frozen on dry ice and stored at −80° C. until tested.
RNA isolation and miRNA profiling. CSF samples were lyophilized and total RNA was extracted using mirVana miRNA isolation kit (Ambion) according to the manufacturer's protocol. The amount of RNA extracted from the CSF samples was within 50-2500 ng/ml range, consistent with the previous findings3. Total RNA from frozen tumor tissues was isolated using Trizol reagent (Invitrogen). The levels of individual miRNAs in CSF and tumors were determined by TaqMan miRNA assays from Applied Biosystems. Four ng of total RNA was used in 6 μl of reverse transcription reaction with specific miRNA RT probes, prior to TaqMan real-time PCR reactions that were performed in duplicates. MiR-125b, which is abundantly and uniformly expressed in brain, was detected in all CSF samples and used as an internal control for normalization (
Samples classification and data analysis. A total of 118 patients of two neurooncological clinics, and corresponding CSF samples were analyzed in this study. 108 patients were classified into six groups based on clinical and pathological diagnoses (including CSF cytology and tumor histology when applicable), and magnetic resonance imaging (MRI) findings (Table 1A, the detailed patients' characteristics are listed in Table 1B). The first control group referred as “Non-neoplastic” includes patients with various neurological conditions other than brain neoplasia. The patients in this group had no cancer at the time of CSF collection, and no previous history of CNS malignancies. The second group “GBM” includes patients diagnosed with active GBM. GBM was referred to as clinically “active” when primary tumor mass was apparent by MRI imaging at the time of CSF samples collection and was further classified as GBM by tumor tissue histology. The two groups called “Breast to Brain” and “Lung to Brain” comprise of samples from the patients with parenchymal brain metastasis from breast carcinoma and lung cancer (including SCLC and NSCLC), respectively. The presence of metastases in these patients was confirmed by MRI imaging at the time of CSF collection. Two additional groups represent patients with documented leptomeningial metastasis of these cancers (CSF or MRI positive disease). Additional seven patients not included in the groups described above were analyzed separately. These patients represent cases of remission of primary and metastatic brain tumors, as indicated by no detectable brain tumor at the time of CSF collection based on imaging features, clinical stability and CSF cytology. The remaining three patients were analyzed in the longitudinal study.
Statistical Analysis and Support Vector Machine (SVM)-based data classification. The differences in CSF miRNAs levels between groups of samples were determined using Graph Pad Prism software by Wilcoxon Signed Rank test, and two-tailed P-values were calculated.
SVM was implemented within a machine learning software package weka (Witten, “Data Mining: Practical machine learning tools and techniques, 3rd Edition”. Morgan Kaufmann, San Francisco (2011)), available on the internet at cs.waikato.ac.nz/ml/weka. In such an approach, a sample's miRNA levels were treated as independent variables and the type of cancer, if any, as a variable to be predicted. The SVM was trained and tested on such a dataset, using standard N-fold cross-validation process. In this process the SVM was trained on all samples, except for one, and tested on that holdout sample. The procedure was repeated as many times as there were samples in the dataset, hence each sample once and only once forms the holdout set. The following choices of non-default parameters working best: Classifier: SMO, kernel RBF, Complexity parameter=one for all tasks, except breast vs. lung metastasis, in which case it was 100. Ct data were used for the classification as is, with no standardization or normalization, except “1000” was used on the place of Ct values in the cases of undetectable miRNA.
The Cancer Genome Atlas (TCGA) miRNA expression microarray data for GBM patients were downloaded from tcga-data.nci.nih.gov/tcga/homepage.htm; see Hudson et al., Nature 464:993-998 (2010). The fold difference in specific signals between GBM (n=261) and normal brain (n=10) tissue were calculated for each miRNA as described3.Example 1 miR-10b is Present and miR-21 is Elevated in CSF of Glioblastoma and Brain Metastasis Patient
To identify miRNA biomarkers for GBM, a candidate approach was used based on previous miRNA profiling data3, 14, 15. An additional analysis of miRNA expression in 261 GBM patients utilized The Cancer Genome Atlas (TCGA) dataset (Hudson et al., Nature 464:993-998 (2010)) and revealed a panel of miRNAs deregulated in GBM relative to normal brain tissues (
miR-10b levels were examined in the CSF samples of the study cohort patients, and miR-10b-specific qRT-PCR product was detected in CSF of 17 out of 19 GBM patients (89% cases,
Next CSF levels were assessed for another candidate miRNA, miR-21, which is the most common miRNA elevated in GBM and other cancers20 and also most strongly up-regulated in GBM as compared to normal brain (
The levels of three additional candidate miRNAs upregulated in GBM relative to normal brain, miR-15b, miR-17-5p and miR-93 (
miR-10b is expressed in most extracranial tissues21, 22 (
According to miRNA profiling across different tissues, miRNAs of miR-200 family are good candidates fulfilling this criteria. All members of this family are highly expressed in lung and breast tissues and epithelial cancers, including lung and breast carcinomas, but are barely detectable in brain22, 24, and
To explore a potential of miRNA-200 for distinguishing between GBM and metastatic brain cancer, the levels of four miR-200 family members, miR-200a, miR-200b, miR-200c and miR-141, were assessed in CSF of control, GBM and metastatic brain cancer patients. Remarkably, all four miRNAs were highly expressed in the majority of CSF samples collected from the patients with brain and leptomeningial metastasis, but not in the control or GBM cases (
In attempt to discriminate between metastasis from breast vs. lung cancer, miR-195 levels were assessed in several randomly selected CSF samples, since circulating miR-195 was proposed as a differential biomarker of breast vs. lung cancer25. However, no significant differences were found in miR-195 levels in CSF of breast and lung cancer metastasis patients (
The relationships discovered between the miRNA CSF levels and diagnostic outcomes are illustrated by a simple diagnostic decision tree (
Various SVM algorithms were applied for classification of the samples. In one case (GBM vs. metastasis classification) a very simple linear classifier provides discrimination with about 95% accuracy. The levels of two miRNAs, miR-200a and miR-125b were used in this case as independent variables, and a linear function of these two Ct levels employed as a classifier with the coefficients calculated in the process of the classifier training.
Another case that allows for a similar interpretation is the classification of GBM and brain metastasis versus non-neoplastic controls. In that case a linear classifier was constructed that uses Ct levels of three miRNAs: miR-10b, miR-200a and miR-125b as features. Accordingly, a two-dimensional plane in the space spawned by the levels of these three miRNAs separated the space into two domains.
Linear algorithms provided satisfactory classification for GBM v Metastasis (using the formula 0.3364*miR-125b+0.0808*miR-10b+0.4578*miR-21+−0.0871*miR-141+0.001*miR-200a+0.0213*miR-200b+−0.3419*miR-200c−7.2516); GBM and metastasis versus non-neoplastic (0.0003*miR-125b+−0.0021*miR-10b+−0.0002*miR-21+0*miR-141+0*miR-200a+0*miR-200b+−0.0021*miR-200c+3.1536); GBM versus non-neoplastic (0.0002*miR-125b+0.0021*miR-10b+−0.0001*miR-21+0*miR-141+0*miR-200a+0*miR-200b+0*miR-200c−1.0849); Metastases versus non-neoplastic (0*miR-125b+0*miR-10b+0*miR-21+0*miR-141+0*miR-200a+0*miR-200b+0.0021*miR-200c−1.0744); GBM versus non-GBM (all others) (0.2468*miR-125b+0.1816*miR-10b+0.107*miR-21+0.0007*miR-141+0.0003*miR-200a+−0.0032*miR-200b+−0.1817*miR-200c−7.7752); Metastasis versus non-metastasis (all others) (0.3348*miR-125b+0.0838*miR-10b+0.4619*miR-21+−0.0902*miR-141+0.001*miR-200a+0.0284*miR-200b+−0.3482*miR-200c−7.3231); Breast versus lung (0.1592*miR-125b+−0.0003*miR-10b+0.0381*miR-21+−0.5325*miR-141+0.5346*miR-200a+−0.0014*miR-200b+−0.1282*miR-200c−1.0529). In each case, a negative result puts the sample into the first class, and a positive result puts the sample into the second class.
Similarly, various SVM classifiers were tested and the RBF kernel provided good separation between all classes of samples. The best classification accuracy was achieved using the levels of seven miRNAs: miR-10b, miR-21, miR-125b, miR-141, miR-200a, miR-200b, and miR-200c as independent variables.
This analysis revealed that different types of cancer are distinguished from each other as well as from non-neoplastic control with the average cross-validation accuracy of about 90% (Table 2A). That means that the SVM incorrectly predicted the class of about one of ten previously unseen samples. This analysis suggests a possibility of computational differential diagnostics of brain cancers using miRNA profiling.Example 4 The origin of miRNA in CSF
miRNAs detected in the CSF of brain cancer patients may originate from brain tumor cells, from surrounding brain tissues or from extracranial tissues due to the blood-brain barrier disruption associated with tumor growth. To discriminate between these possibilities miR-10b and miR-21 expression levels were determined in tumor biopsies obtained during brain surgery and corresponding CSF samples from the same patients. A positive correlation was observed between miR-10b expression level in the brain tumor and corresponding CSF specimens, and no such correlation was observed for miR-21 (
To examine whether CSF levels of miRNAs reflect a disease status/activity, miRNA was studied in CSF of active GBM and metastatic brain cancer versus tumor remission cases. The disease was considered in remission if, following treatment, there were no evidence of tumor mass detected by MRI and CSF cytological analysis was negative. Neither miR-10b nor miR-200 family members were detected after 40 cycles of qRT-PCR reaction in CSF samples in any of remission cases (Table 3,
To further test whether the CSF levels of specific miRNAs reflect the disease status/activity and responsiveness to therapy, miRNA levels were determined in CSF of lung cancer and GBM patients longitudinally during course of erlotinib treatment. miRNA analysis was accompanied by MRI, CSF cytology, and clinical monitoring of the disease status. A NSCLC patient (patient A) developed parenchymal and leptomeningeal disease during course of treatment and medication adjustment (
Patient B (
Altogether, these data indicate for the first time that CSF miRNA levels may serve as biomarkers of brain cancer progression and response to therapy.
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It is to be understood that 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.
9. A method of monitoring progression of a brain tumor, the method comprising: determining, using real time polymerase chain reaction (RT-PCR) or an RNA expression assay, levels of one or more of miR-10b, miR-21, and a miR-200 family member in a first sample comprising cerebrospinal fluid from a subject; and
- determining, using real time polymerase chain reaction (RT-PCR) or an RNA expression assay, levels of one or more of miR-10b, miR-21, and a miR-200 family member in a subsequent sample comprising cerebrospinal fluid from the subject;
- comparing the levels of the one or more of miR-10b, miR-21, and a miR-200 family member in the first sample to the levels of the one or more of miR-10b, miR-21, and a miR-200 family member in the subsequent sample; and
- determining presence of progression or recurrence of the brain tumor based on the presence of levels of miR-10b, miR-21, or miR-200 family member in the subsequence sample above the levels in the first sample, or determining that the brain tumor is regressing or is in remission based on levels of miR-10b miR-21, or miR-200 family member in the subsequent sample below the levels in the first sample.
10. The method of claim 9, wherein:
- the subject has been diagnosed with a primary brain tumor, and the method includes monitoring levels of one or both of miR-10b and miR-21; or
- the subject has been diagnosed with a metastatic brain tumor, and the method includes monitoring levels of one or more of miR-10b, miR-21, and a miR-200 family member.
11. The method of claim 9, wherein the method further comprises administering a treatment to the subject after obtaining the first sample and before obtaining the subsequent sample, and wherein a decrease in levels of miR-10b, miR-21, or at least one miR-200 family member in the subsequence sample as compared to the level in the first sample indicates that the treatment is effective.
12. The method of claim 11, wherein the treatment comprises administration of one or more of surgical resection, chemotherapy, or radiotherapy.
15. The method of any of claim 9, in which the levels are determined using RT-PCR.
16. The method of claim 9, wherein the miR-200 family member is miR-200a, miR-200b, miR-200c, miR-141, or miR-429.
17. The method of claim 9, wherein the method comprises normalizing the levels to a level of miR-125 or miR-24.
18. The method of claim 9, wherein the primary brain tumor is a glioma, glioblastoma, hemangioma, or medulloblastoma.
20. A method of treating metastatic or primary brain tumors in a subject, the method comprising:
- determining levels of miR-10b, miR-21, and miR-200 in a sample comprising cerebrospinal fluid (CSF) from a subject, and
- comparing the levels of miR-10b, miR-21, and miR-200 to reference levels of miR-10b, miR-21, and at least one miR-200 family member, and
- determining that the subject does not have a metastatic or primary brain tumor when the levels of all of miR200, miR-10b or miR-21 are below the reference levels;
- diagnosing a metastatic or primary brain tumor in a subject who has levels of miR-10b or miR-21 above the reference levels, and administering a treatment for a metastatic or primary brain tumor to the subject; and
- diagnosing a metastatic brain tumor when the levels of the miR-200 family member are above the reference level, and administering a treatment for metastatic brain cancer to a subject who has levels of the miR-200 family member above the reference level.
21. The method of claim 20, wherein determining levels of miR-10b, miR-21, and miR-200 in a sample comprises using real time polymerase chain reaction (RT-PCR) or an RNA expression assay.
22. The method of claim 20, wherein the treatment comprises administration of one or more of surgical resection, chemotherapy, or radiotherapy.