In this study, we found that at a physiological concentration, 25(OH)D3 (25D3), the precursor of 1,25D3 and an inactive form of vitamin D because of its much weaker binding activity to the vitamin D receptor (VDR) compared with 1,25D3, had a gene expression profile similar to that of 1,25D3 in prostate cancer LNCaP cells. The gene discussed is VDR; the disease is prostate carcinoma.