The influence of PSA-RNA yield on the analysis of expressed prostatic secretions (EPS) for prostate cancer diagnosis.

INTRODUCTION In patients with prostate cancer, luminal prostate-specific antigen (PSA) enters the circulation because the basement membrane and glandular epithelium are damaged. Given that excess mobilization of prostate cells during prostatic massage can influence normalization in diagnostic testing, we studied PSA mRNA levels in expressed prostatic secretions (EPS) from patients undergoing biopsy for prostate cancer to determine if prostate cells are preferentially mobilized from patients with prostate cancer during prostatic massage. MATERIALS AND METHODS Quantitative Reverse-Transcription PCR (qRT-PCR) was used to measure the RNA levels of GAPDH, PSA, TMPRSS2:ERG and PCA3 in EPS specimens obtained from patients undergoing biopsy for prostate cancer. RESULTS The level of PSA mRNA is significantly elevated in EPS specimens obtained from patients with a subsequent diagnosis of prostate cancer. This correlation influenced diagnostic testing results from EPS in two ways. First, when used as an exclusion parameter it appears to improve the diagnostic performance of TMPRSS2:ERG in EPS. Second, when used as a normalization parameter it appears to decrease the performance of these same tests. CONCLUSION When comparing the results of mRNA based prostate cancer diagnostics in EPS it will be essential to consider PSA mRNA as a prostate specific gene and not a housekeeping gene.

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