CYP24A1 and melanoma: This surprising expression pattern of CYP24A1 in human melanomas could in part be explained by the recent discovery that CYP24A1, apart from inactivating calcitriol, also hydroxylates 20-hydroxyvitamin D3 (20(OH)D3) to two major dihydroxy-derivatives, 20,24-dihydroxyvitamin D3 (20,24(OH)2D3) and 20,25-dihydroxyvitamin D3 (20,25(OH)2D3), which are significantly more efficient at inhibiting melanoma growth in soft agar than 1,25(OH)2D3 and 20(OH)D3 [48].