CYP17A1 and Familial prostate cancer: Mechanistically, this 7% increase in the risk of prostate cancer was attributed to the location of rs2486758 in the promoter region of CYP17A1. Alterations of CYP17A1 activity including up-regulation have been described as a mechanism of resistance to AA/P in human prostate cancer xenografts, making the enzyme a potential candidate as a predictive biomarker [29].