Apolipoprotein E (APOE) Polymorphisms and Susceptibility to Breast Cancer: A Meta-Analysis

Purpose Apolipoprotein E (APOE, MIM: 107741) has three functionally distinct isoforms of the protein (E2, E3, and E4), encoded by corresponding alleles epsilon 2, epsilon 3, and epsilon 4, which have been well described. Findings from previous studies investigating association between APOE polymorphisms and breast cancer risk have been inconsistent. The present meta-analysis was conducted in order to investigate association of APOE polymorphisms with risk of breast cancer. Materials and Methods Several electronic databases were used for identification of studies containing information on APOE polymorphisms and breast cancer risk published up to January 2012. We identified 10 eligible studies, including 3,835 subjects (2008 patients, and 1,827 healthy controls), that reported on polymorphisms of APOE and risk of breast cancer. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were obtained using a fixed and random-effects models. Results Among studies reported from Asia, an association of the epsilon 4 allele with increased risk of breast cancer, in comparison with the epsilon 3 allele, was observed (OR, 1.56; 95% CI, 1.19 to 2.04; p=0.001). It should be noted that allele epsilon 2 showed no association with breast cancer risk. Among Caucasians, neither the epsilon 4 (OR, 0.99; 95% CI, 0.83 to 1.17; p=0.917) nor the epsilon 2 (OR, 0.92; 95% CI, 0.72 to 1.17; p=0.514) allele showed an association with susceptibility to breast cancer, when compared with the epsilon 3 allele. Carriers of the epsilon 4 allele (E4E4, E4E3, and E4E2 genotypes), in comparison with the E3E3 genotype, showed an association with elevated risk of breast cancer only among Asians (OR, 1.75; 95% CI, 1.23 to 2.47; p=0.002). No publication bias was detected. Conclusion This meta-analysis suggest that the APOE epsilon 4 allele is a low-penetrant risk factor for development of breast cancer.