KLK3 and Familial prostate cancer: Although administration of a soy isoflavone supplement for up to one year did not significantly lower the prostate-specific antigen (PSA) in the blood serum of men that had not confirmed prostate cancer yet [192], the soy isoflavone supplement seems to slow down rising concentration of PSA in the blood serum, a phenomenon that is connected to prostate tumor growth in patients with prostate cancer [193].