BRCA1 and ovarian cancer: The deletion variant in this region may also affect the regulation of a nearby gene CYP2A6,29 which is known to have a key role in the metabolism of a number of substrates including nicotine, coumarin and valproic acid.30 Interestingly, a deletion at the CYP2A6 locus has been found to be associated with decreased risk of lung cancer in Asian smokers,31 which is comparable to our finding that CYP2A7 deletions were more frequent in non-affected high-risk BRCA1 pathogenic variant carriers compared with those with ovarian cancer (MAF—3.8% versus 1.1%).