CYP2R1 and Familial prostate cancer: Prostate cancer cells (LNCaP and 22Rv1) showed low to no expression of CYP27B1 (encoding a vitamin D 25-hydroxylase; Fig. 1A) and were unable to metabolize 25D to the active hormone 1,25D, as shown by the lack of CYP24A1 (encoding vitamin D 24-hydroxylase) induction by 25D (Supplementary Fig. S1A).