Quantitative Analysis of Human Kallikrein 5 (KLK5) Expression in Prostate Needle Biopsies: An Independent Cancer Biomarker

BACKGROUND: Kallikrein 5 (KLK5), a recently cloned member of the kallikrein family, codes for the secreted protein KLK-5. Active KLK5 protein has a trypsin activity, and the expression of KLK5 gene seems to be regulated by steroid hormones. We performed an expression analysis and clinical evaluation of the KLK-5 gene, at the mRNA level, in prostate needle biopsies. METHOD: We examined KLK5 mRNA concentrations in 103 prostate tissue specimens. After testing of RNA quality, cDNA was prepared by reverse transcription. A highly sensitive quantitative real-time PCR (qRT-PCR) method for KLK5 mRNA quantification was developed using the SYBR Green chemistry. GAPDH was used as a housekeeping gene. RESULTS: Specimens from patients with benign prostatic hyperplasia (BPH) showed higher levels of KLK5 mRNA expression than those from patients with prostate cancer (PCa) (P = 0.024). ROC analysis demonstrated that KLK5 expression had significant discriminatory value between BPH and PCa (AUC 0.64; P = 0.016). KLK5 mRNA expression showed a statistically significant negative correlation with the total PSA serum concentration in the PCa patients (P = 0.003). Early-stage tumors showed higher KLK5 expression than late-stage ones (P = 0.014), whereas KLK5 expression was negatively correlated to Gleason score (P = 0.005). CONCLUSIONS: KLK5 mRNA, analyzed by quantitative PCR in prostate needle biopsies, could be an independent biomarker for the differential diagnosis and prognosis in prostate cancer. (C) 2009 American Association for Clinical Chemistry