CYP2A6 and lung carcinoma: Therefore, the presence of CYP2A6 null alleles may theoretically reduce the risk of developing cancer.30-32 A recent case-control study demonstrated a possible protective effect against lung cancer in subjects carrying CYP2A6 deletion alleles.27 It is of interest that subjects heterozygote for the deletion allele had a lower risk of lung cancer than those carrying two CYP2A6*1A alleles in that study.