Expression of kallikrein-related peptidase 7 is decreased in prostate cancer

Abstract

Recent evidence suggests that the human kallikrein 7 (KLK7) is differentially regulated in a variety of tumors. The aim of this study was to determine the expression of kallikrein-related peptidase 7 and KLK7 in our large collection of prostate samples. Between August 2000 and December 2012, 116 patients with histologically confirmed prostate cancer (PCa) and 92 with benign prostate hyperplasia (BPH) were recruited into the study. Using immunohistochemistry, quantitative reverse transcription polymerase chain reaction (RT-PCR) and western blot, kallikrein-related peptidase 7 expression in BPH and PCa tissues was determined at the mRNA and protein levels. The relationships between kallikrein-related peptidase 7 mRNA expression and clinicopathological features were analyzed. A total of 64 of 92 (69.57%) benign cases showed positive staining for KLK7 and 23 of 116 (19.83%) malignant cases showed positive, the difference of KLK7 expression between PCa and BPH was statistically significant (P < 0.001). The expression level of kallikrein-related peptidase 7 mRNA was significantly decreased in PCa tissues compared with that in BPH tissues and normal prostate tissue. Kallikrein-related peptidase 7 mRNA exhibited different expression patterns in terms of localization depending on pathological category of PCa. Similarly, our western immunoblot analyses demonstrated that the protein expression levels of KLK7 was lower in PCa than in BPH tissues and normal prostate tissue. Kallikrein-related peptidase 7 and KLK7 expression are down-regulated in PCa and lower expression of kallikrein-related peptidase 7 closely correlates with higher Gleason score and higher prostate-specific antigen level.

Figure 1

Quantitative real-time polymerase chain reaction showing expression level of KLK7 mRNA. (a) KLK7 mRNA expression in PCa tissues, BPH tissues and normal prostate tissue (**P< 0.01). (b) KLK7 mRNA expression in the three subgroups of localized PCa samples, Gleason score < 7, =7 and > 7 (*P< 0.05). (c) KLK7 mRNA expression in the three subgroups of localized PCa samples, PSA levels < 10 ng ml−1, 10–20 ng ml−1, and > 20 ng ml−1 (*P< 0.05). (d) KLK7 mRNA expression in PIN localized PCa and metastatic PCa (*P< 0.05). BPH: benign prostate hyperplasia; PCa: prostate cancer; PIN: prostatic intraepithelial neoplasia; LPCa: localized prostate cancer; MPCa: metastatic prostate cancer; PSA: prostate-specific antigen.

Figure 2

Immunohistochemistry. (a) Positive staining of hK7 was observed in the cytoplasm of benign prostate epithelium, scale bar = 100 μm. (b) Little or no staining of hK7 was observed in prostate cancer, scale bar = 100 μm.

Figure 3

Western blots showing expression of hK7 in PCa tissues, BPH tissues and normal prostate tissue. BPH: benign prostate hyperplasia; PCa: prostate cancer.