Serum level of cathepsin B and its density in men with prostate cancer as novel markers of disease progression.

Cathepsin B has been shown to play an important role in invasion and metastasis of prostate cancer. The objective of this study was to determine whether serum levels of cathepsin B and its density (cathepsin B-D) could be used as predictors of disease extension as well as prognosis in patients with prostate cancer. Serum levels of cathepsin B in 60 healthy controls, 80 patients with benign prostatic hypertrophy (BPH) and 120 patients with prostate cancer were measured by a sandwich enzyme immunoassay. Cathepsin B-D was calculated by dividing the serum levels of cathepsin B by the prostate volume, which was measured using transrectal ultrasonography. We subsequently analyzed the association between these two factors and several clinicopathological factors. The mean values of cathepsin B and cathepsin B-D in patients with prostate cancer were significantly higher than those in healthy controls and BPH patients. Moreover, the cathepsin B and cathepsin B-D levels in patients with metastasis were significantly elevated compared with those in patients without metastasis. Among patients undergoing radical prostatectomy, the levels of cathepsin B and cathepsin B-D in those with pathologically confirmed extraprostatic disease were significantly higher than in patients with organ-confined disease. However, there was no significant association between the elevation of cathepsin B and cathepsin B-D levels and cause-specific survival in prostate cancer patients. These findings indicate that the elevation of serum cathepsin B and cathepsin B-D could be used as novel predictors of disease extension, but not survival, in patients with prostate cancer.