Objective: To investigate the associations of the XbaI and PvuII gene polymorphisms in estrogen receptor alpha (ER alpha) gene and breast cancer risk.
Methods: Using the method of restrictive fragment length polymorphism, the XbaI and PvuII genotypes of ER alpha gene were examined in 138 female breast cancer patients and 140 healthy control subjects that age and sex matched. Analyses stratified by menopausal status were conducted to check the associations of the XbaI and PvuII gene polymorphisms of ER alpha gene and breast cancer risk.
Results: The frequencies of the XbaI and PvuII alleles of ER alpha gene were 28.9% for XbaI X allele and 39.6% for P PvuII allele, respectively, in healthy Han Chinese. The frequencies of XX and PP genotypes were 4.3% and 15.0%, respectively. The frequencies of Xx genotype and carrier with X allele (XX + Xx) in breast cancer patients were 34.8% and 39.1%, respectively, significantly lower than that in controls with 49.3% and 53.6%, respectively (P = 0.013 and P = 0.016, respectively). The odds ratio (OR) for heterozygous Xx and carriers with X allele (XX + Xx) were 0.538 (95% CI: 0.330 - 0.879) and 0.557 (95% CI: 0.346 - 0.897), respectively, decreased the breast cancer risk compared with the homozygous xx genotype. The decreases in the OR showed to be more significantly in the postmenopausal women, OR were 0.366 (95% CI: 0.161 - 0.834) and 0.371 (95% CI: 0.167 - 0.823), respectively. No significant difference was showed in the PvuII genotype distribution between patients and controls.
Conclusions: The XbaI gene polymorphism of ER alpha gene was associated with breast cancer risk, more significantly in postmenopausal women. The XbaI X allele could decrease the risk of breast cancer. No apparent effect of the PvuII gene polymorphisms of ER alpha gene was identified.