CYP3A4 and cancer: Furthermore, SFN inhibits cancer initiation by modulating metabolic enzymes, leading to the reduction of carcinogen-activating phase I enzymes (e.g., decreasing CYP1A1 (cytochrome P450 family 1 subfamily A member 1) and CYP3A4 (cytochrome P450 family 3 subfamily A member 4) activity) and activation of carcinogen-detoxifying phase II enzymes [22,24].