CYP24A1 and colon adenoma: CYP24A1 levels are upregulated in various solid tumours including colorectal tumours.14, 15, 16 Increased expression of CYP24A1 is an early event during colorectal carcinogenesis and the upregulation is already observed in colonic adenomas.17 The high CYP24A1 expression in tumour cells probably leads to depletion of local 1,25‐D3 levels in the tumour environment, decreasing its antitumourigenic functions.