RESUMO
OBJECTIVES: The benefits of PSA (prostate specific antigen)-testing in prostate cancer remain controversial with a consequential need for validation of additional biomarkers. We used highly standardized reverse-transcription (RT)-PCR assays to compare transcript levels of 10 candidate cancer marker genes - BMP6, FGF-8b, KLK2, KLK3, KLK4, KLK15, MSMB, PCA3, PSCA and Trpm8 - in carefully ascertained non-cancerous versus cancerous prostate tissue from patients with clinically localized prostate cancer treated by radical prostatectomy. DESIGN AND METHODS: Total RNA was isolated from fresh frozen prostate tissue procured immediately after resection from two separate areas in each of 87 radical prostatectomy specimens. Subsequent histopathological assessment classified 86 samples as cancerous and 88 as histologically benign prostate tissue. Variation in total RNA recovery was accounted for by using external and internal standards and enabled us to measure transcript levels by RT-PCR in a highly quantitative manner. RESULTS: Of the ten genes, there were significantly higher levels only of one of the less abundant transcripts, PCA3, in cancerous versus non-cancerous prostate tissue whereas PSCA mRNA levels were significantly lower in cancerous versus histologically benign tissue. Advanced pathologic stage was associated with significantly higher expression of KLK15 and PCA3 mRNAs. Median transcript levels of the most abundantly expressed genes (i.e. MSMB, KLK3, KLK4 and KLK2) in prostate tissue were up to 10(5)-fold higher than those of other gene targets. CONCLUSIONS: PCA3 expression was associated with advanced pathological stage but the magnitude of overexpression of PCA3 in cancerous versus non-cancerous prostate tissue was modest compared to previously reported data.