Abstract: A method for enhancing the detection of prostate specific antigen in a biological sample comprising (a) extracting mRNA from the sample: (b) contacting the mRNA from step (a) with reverse transcriptase under conditions allowing for the production of cDNA; (c) contacting the cDNA from step (b) with a pair of reverse transcriptase polymerase chain reaction primers capable of specifically hybridizing with DNA encoding prostate specific antigen wherein one such primer is an oligonucleotide of 12 to 30 nucleotides in length and comprises the sequence 5-CACCCATCCTA-3' and wherein the second such primer is an oligonucleotide of 12 to 30 nucleotides in length and comprises the sequence 5'-TCCAGCCACGAC-3'; and wherein at least one of the primers is covalently linked to a modified digoxigenin molecule and under conditions allowing for extension of the primers; and (d) detecting the resulting amplified DNA.

Abstract: This invention provides a method of determining the stage of prostate cancer in a human subject using a sample of peripheral blood from a human subject. The invention uses reverse transcriptase-PCR to detect the mRNA encoding prostate specific antigen (PSA) in circulating cells expressing PSA. The invention further uses digoxigenin enhancement of the resultant cDNA signal. The method has an overall sensitivity capable of detecting one PSA expressing cell per 100,000 cells. The method produced no false positives and had a superior detection selectivity for patients with nonlocalized prostate cancer.