Lack of an association between a functional polymorphism in the interleukin-6 gene promoter and breast cancer risk: a meta-analysis involving 25,703 subjects.

The association between a single-nucleotide polymorphism (SNP) -174G > C (rs1800795) located in the IL-6 gene promoter and breast cancer risk is still controversial and ambiguous. We performed in this study a more precise estimation of the relationship by meta-analyzing the currently available evidence from literature. A total of 11 publications containing 12 studies including 10,137 cases and 15,566 controls were identified. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association in the codominant model, dominant model, and recessive model. When all the studies were pooled into the meta-analysis, there was no evidence showing a significant association between -174G > C and breast cancer risk (for CC vs. GG: OR = 1.024, 95% CI: 0.935-1.121; for GC vs. GG: OR = 1.008, 95% CI: 0.946-1.073; for dominant model: OR = 0.980, 95% CI: 0.857-1.121; and for recessive model: OR = 1.027, 95% CI: 0.944-1.117). In the subgroup analyses by ethnicity, no significant associations were observed in any genetic models. In summary, the present meta-analysis suggests that the functional polymorphism -174G > C within the IL-6 gene promoter is not associated with breast cancer risk. Identifying a unique SNP as a breast cancer risk predictor remains a very challenging task.