Interleukin 6 G-174 C polymorphism and breast cancer risk

Interleukin-6 (IL-6) is a growth factor involved in many processes including carcinogenesis. The C allele of the G-174 C promoter single nucleotide polymorphism (SNP) in the IL-6 gene decreases levels of IL-6 expression and it has been studied in the context of breast cancer progression yielding contradicting results. Furthermore a recent study found that carriers of the C allele were at an increased risk for this disease. We aim to evaluate the association between this variant and breast cancer risk in Caucasian postmenopausal women. Women participating in the Rotterdam Study (N=3822), including 171 patients with breast cancer were genotyped for this polymorphism. In order to assess the relationship between this SNP and breast cancer we carried out a logistic regression in relation to the incidence of breast cancer. The C allele frequency was 41.3% and the genotypes followed Hardy-Weinberg distribution (p=0.3). The logistic regression analysis showed a slight increase of risk for C allele carriers (odds ratio=1.24, 95% CI: 0.8-1.9), compared to non-carriers of this allele. This increased risk was not statistically significant. Our data suggest that the IL-6 G-174 C polymorphism does not seem to play a role in breast cancer risk, although its role as a prognostic factor remains to be studied.