Genotype frequencies of selected drug metabolizing enzymes and ABC drug transporters among breast cancer patients on FAC chemotherapy

Abstract

Polymorphic genes of drug metabolizing enzymes and transporters may influence drug response. With some exemptions, single nucleotide polymorphisms in such genes, however, are not known to be susceptibility factors for breast cancer. This study explored genotype profiles for the breast cancer patients on fluorouracil, doxorubicin and cyclophosphamide (FAC) in a Pakistani set of population and their comparison with HapMap data. Sixty-eight female breast cancer patients were included. All received FAC chemotherapy. Relevant genotyping was done either through restriction fragment length polymorphism or pyrosequencing. The variant allele frequencies were: 5.1% for CYP2C9*2 (430C>T), 15.4% for CYP2C9*3 (1075A>C), 27.2% for CYP2C19*2 (681G>A), 33.1% for GSTA1*B (-69C>T, -52G>A), 62.5% for ALDH3A1*2 (985C>G), 58.8% and 4.4% for ABCB1 (2677 G>T/A), 64.7% for ABCB1 3435 C>T, and 15.4%, 33.1% and 39.7% for ABCC2 (-24 C>T, 1249 G>A and 3972 C>T). In comparison with HapMap, this first exploration in Pakistani samples shows higher frequency of (i) CYP2C9*3 carriers (p < 0.05) than in Hispanic, Chinese, Japanese and African samples, (ii) ALDH3A1*2 carriers (p < 0.01) than Caucasian, Hispanic, Chinese, Japanese and African samples. For ABC transporters, a higher frequency of variant allele was observed in (iii) ABCB1 2677 G>T/A (p < 0.01) than Caucasian, Hispanic and African, (iv) ABCB1 3435 C>T (p < 0.05) than Chinese, Japanese and African, (v) ABCC2 1249 G>A (p < 0.01) than Hispanic, Chinese and Japanese samples. In conclusion, cyclophosphamide activation and detoxification of reactive intermediates may be altered in the Pakistani. Though carriers of CYP2C19*2 were higher than in Caucasian and Hispanics, they did not reach statistical significance (p = 0.05).