CYP2A13 and lung cancer: The possible regulation or implication of the estrogen receptor (ER) in CYP2A13 expression can be speculated from the case control study, where a nonsignificant increase in lung cancer risk was observed in the group of women carriers of the minor allele of CYP2A13 SNP rs1709084 (13103A>G), in which, the effect was further modified by smoking [76].