In human primary prostate epithelial cells that expressed CYP27B1, low concentrations of 25(OH)D3 suppressed cell growth.(27) In prostatic cancer cells lacking CYP27B1, 25(OH)D3 failed to demonstrate antiproliferative action.(28) There are several mechanisms mediating the antiproliferative effects of 1,25(OH)2D3. The gene discussed is CYP27B1; the disease is prostate carcinoma.