Subjects were initially analyzed for CYP2A6 copy number (CYP2A6*4 and CYP2A6*1X2) and genotyped for eight other polymorphisms previously reported to be common in Europeans and potentially associated with CYP2A6 mRNA expression or enzyme activity: 1) rs4803381 (−1013A/G), 2) rs61663607 (−745A/G) [22], 3) rs28399433 (−48T/G, the defining SNP in CYP2A6*9) [23], 4) rs1137115 (51A/G, V17V) [24], 5) rs28399435 (86G/A, S29N, the defining amino acid change in CYP2A6*14)[25], 6) rs2801272 (1799T/A, L160H, the defining amino acid change in CYP2A6*2)[26], 7) the large deletion resulting in the CYP2A7/CYP2A6 hybrid CYP2A6*12 [19]and 8) the 58 bp CYP2A7 gene conversion in the 3′ UTR of CYP2A6*1B [27]. Polymorphism nomenclature follows official recommendations (http://www.cypalleles.ki.se/cyp2a6.htm). A TaqMan CNV assay, Hs00010002_cn (Applied Biosytems, Foster City, CA, USA) was used to determine CYP2A6 copy number. Copy number variation was analyzed by real-time PCR using an ABI-7900 real-time PCR system. Each real-time PCR run included within-plate duplicates and an RNase P reference assay. CopyCaller v1.0 software (Applied Biosystems) was used to interpret copy number results. Individual genotypes at SNPs rs1137115 and rs28399435 had been previously determined using a custom designed
