CYP24A1 and cervical carcinoma: In addition, evidence of negative feedback inhibition of CYP24A1 induced by autocrine 1,25(OH)D3 synthesis is supported by a transfected 1α-hydroxylase SiHa cell model treated with vitamin D metabolites [66] These preclinical studies collectively support the hypothesis of autocrine activation of 25(OH)D3 to 1,25(OH)D3 by 1α-hydroxylase in cervical cancer cells, which induces the CYP24A1 catabolic enzyme to attenuate an intracellular hypervitaminosis D environment.