Association between IL6 -174G/C and cancer: A meta-analysis of 105,482 individuals.

Interleukin-6 (IL6) is a pleiotropic inflammatory cytokine, which is implicated in the development and progression of several types of cancer. The -174G/C polymorphism of the IL6 gene controls serum levels of IL6 and may be associated with cancer risk, but the results from the published studies on the association between this polymorphism and cancer risk are conflicting. A comprehensive meta-analysis was conducted to assess the association of IL6 -174G/C with cancer risk. Studies were identified by searches of MEDLINE and HuGE Published Literature databases, with no restrictions. An eligible 83 articles involving 44,735 cancer patients and 60,747 controls were included. Combined odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association between the IL6 -174 G/C polymorphism and cancer risk. Potential sources of heterogeneity were explored by meta-regression and sensitivity analysis. Overall, the IL6 -174G/C polymorphism was not significantly associated with cancer risk. However, cancer risk was increased for individuals with the CC genotype compared to those carrying the GG genotype in African populations (OR=1.83, 95% CI 1.26-2.67, P=0.002), but not in Caucasian populations (OR=1.00, 95% CI 0.92-1.08, P=0.938). The present meta-analysis provides the first evidence of the ethnic-specific association of the IL6 -174G/C polymorphism with cancer risk. Further investigations with a large number of cases and controls are required to confirm the associations between this polymorphism and cancer in Africans.