Evaluation of Tissue PCA3 Expression in Prostate Cancer by RNA in situ Hybridization - A Correlative Study with Urine PCA3 and TMPRSS2-ERG

PCA3 is a prostate-specific non-coding RNA, with utility as urine based early detection biomarker. Here, we report the evaluation of tissue PCA3 expression by RNA in-situ hybridization in a cohort of 41 mapped prostatectomy specimens. We compared tissue PCA3 expression with tissue level ERG expression and matched pre-prostatectomy urine PCA3 and TMPRSS2-ERG levels. Across 136 slides containing 138 foci of prostate cancer, PCA3 was expressed in 55% of cancer foci and 71% of high grade prostatic intraepithelial neoplasia foci. Overall, the specificity of tissue PCA3 was >90% for prostate cancer and high grade prostatic intraepithelial neoplasia combined. Tissue PCA3 cancer expression was not significantly associated with urine PCA3 expression. PCA3 and ERG positivity in cancer foci were positively associated (p<0.01). We report the first comprehensive assessment of PCA3 expression in prostatectomy specimens, and find limited correlation between tissue PCA3 and matched urine in prostate cancer.