Androgens in breast cancer have been studied alone and in correlation with estrogens as estrogen to testosterone ratio. 5-α-reductase is one of the important enzymes participating in androgen metabolism, which affects androgen activity by affecting conversion of testosterone to dihydrotestosterone. We hypothesized that polymorphisms in the SRD5A2 gene (encoding 5-α-reductase) may affect breast cancer risk by affecting total androgen activity. Complete coding region of the SRD5A2 gene was sequenced in a group of 628 patients and 244 control samples from three southern states (Tamil Nadu, Andhra Pradesh, and Karnataka) of India. We observed three common polymorphisms in this gene namely, A49T, V89L, and (TA)n repeats. A49T locus was monomorphic in the study population, but V89L showed a strong correlation with breast cancer (P=0.03, OR=1.40, CI=1.02-1.91). (TA)0/(TA)9 and (TA)9/(TA)9 genotypes were at a lower risk of breast cancer (P=0.01, OR=0.64, CI=0.46-0.90). We conclude that SRD5A2 genotypes significantly affect breast cancer risk in the South Indian populations.
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