CYP24A1 is both a crucial inactivating enzyme of VD3/1,25(OH)2D3 and a downstream transcriptional target of VDR; thus, transcriptional activation of CYP24A1 by 1,25(OH)2D3 can attenuate the anti-tumor effect of VD3 therapy 53, 58. The gene discussed is CYP24A1; the disease is neoplasm.