The association between two polymorphisms of eNOS and breast cancer risk: a meta-analysis

Breast cancer is one of the most common malignant tumors worldwide. Endothelial nitric oxide synthase (eNOS) plays a key role in breast cancer development. The associations between the two eNOS polymorphisms (E298D rs1799983, −786T>C rs2070744) and breast cancer risk are inconclusive. A meta-analysis was performed in this study. By searching Medline, ISI Web of Knowledge, ScienceDirect, EBSCO, CNKI, and SinoMed database, six case–control studies were collected for the eNOS E298D polymorphism (3,038 cases and 2,508 controls) and three case–control studies were eligible for the eNOS −786T>C polymorphism. Crude ORs with 95% CIs were used to assess the strength of association between the two eNOS polymorphisms and breast cancer risk. The pooled ORs were performed for codominant model, dominant model, and recessive model, respectively. Overall, significantly decreased risk was observed for E298D (for EE vs. DD: OR = 0.74, 95% CI = 0.59–0.94; for ED vs. DD: OR = 0.78, 95% CI = 0.61–0.98; for dominant model: OR = 0.77, 95% CI = 0.61–0.96) and −786T > C (for TT vs. CC: OR = 0.60, 95% CI = 0.42–0.86; for dominant model: OR = 0.66, 95% CI = 0.47–0.94). In the subgroup analysis by ethnicity, significant decreased risks were found for E298D (for EE vs. DD: OR = 0.75, 95% CI = 0.56–0.99) and −786T>C (for TT vs. CC: OR = 0.53, 95% CI = 0.35–0.81; for dominant model: OR = 0.61, 95% CI = 0.41–0.91; for recessive model: OR = 0.70, 95% CI = 0.55–0.91) among Caucasians; significant decreased risks were observed for E298D (for ED vs. DD: OR = 0.12, 95% CI = 0.02–0.96; for dominant model: OR = 0.13, 95% CI = 0.02–1.00) among Asians. In conclusion, this meta-analysis suggests that both eNOS E298D and −786T>C polymorphisms are associated with reduced breast cancer risk.