CYP24A1 (24-hydroxylase) is the main enzyme that inactivates vitamin D hormones, especially 1,25-dihydroxyvitamin D (calcitriol), by hydroxylating it toward water-soluble metabolites. In cancer biology, that matters because calcitriol signaling through the vitamin D receptor (VDR) can push cells toward differentiation, cell-cycle arrest, and sometimes apoptosis, and can dampen pro-inflammatory signaling. So, when CYP24A1 is high, tumors can effectively “turn off” local vitamin D anti-tumor signaling.
Many studies report CYP24A1 overexpression in subsets of cancers (commonly discussed in colon/colorectal, breast, lung, prostate, ovarian, thyroid, melanoma, among others).
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