Down-regulation of the human kallikrein gene 5 (KLK5) in prostate cancer tissues.

Abstract

Kallikreins are a subgroup of serine proteases with diverse physiological functions. Many kallikrein genes are differentially expressed in various malignancies and prostate specific antigen (PSA; encoded by the KLK3 gene) is the best tumor marker for prostate cancer. Human glandular kallikrein (hK2; encoded by the KLK2 gene) is an emerging tumor marker for prostate cancer. KLK5 is a newly discovered human kallikrein gene which shares a high degree of homology and is located adjacent to KLK2 and KLK3 genes on chromosome 19q13.4. Like KLK2 and KLK3, the KLK5 gene is regulated by steroid hormones in the BT-474 breast cancer cell line. We have previously shown that KLK5 is differentially expressed in ovarian and breast cancer. We compared the expression of KLK5 in 29 pairs of histologically confirmed normal and prostate cancer tissues by quantitative RT-PCR using the LightCycler technology. KLK5 expression was significantly lower in cancer tissues compared to their normal counterparts. Lowest levels of expression were found in T3 stage tumors compared with T1 and T2. Also, a significant negative correlation was found between Gleason score and KLK5 expression. KLK5 should be further studied as a potential new prognostic marker in prostate cancer, whose expression is negatively correlated with cancer aggressiveness.