Normal melanocytes and melanoma cells express CYP2R1, CYP27A1, CYP27B1, and CYP24A1 at variable levels, and so can potentially activate and inactivate vitamin D3 by the above pathways [407,438,439,440,441,442,443], which in fact was demonstrated in cultured melanoma cells [444]. The gene discussed is CYP27A1; the disease is melanoma.