CYP27B1 and cancer: Multiple lines of evidence have shown the vitamin D pathway dysregulation in different types of cancer, for instance, cytochrome P450 (CYP) genes such as CYP2R1, CYP27A1, and CYP27B1. 6, 7, 8In summary, vitamin D synthesis is as follows: CYP2R1 and CYP27A1 convert vitamin D to circulating 25(OH)D.