CYP2A6 and breast carcinoma: Iscan et al. [13] studied the expression of CYPs in breast cancer tissues, and the results showed that in comparison with normal tissues, the expression of CYP1A1 is lower, and CYP2A6, 2F1, 2A7, 2A13, 3A4, 3A5, and 3A7 are not expressed.