-174G/C interleukin-6 gene promoter polymorphism predicts therapeutic response to etanercept in rheumatoid arthritis

To examine whether -174G/C interleukin-6 (IL-6) gene polymorphism, previously reported to correlate with IL-6 level, influences response to etanercept therapy in patients with rheumatoid arthritis. Seventy-seven patients with active RA were studied, at baseline and 6- and 12-month follow-up after etanercept therapy. Treatment response was estimated according to the European League Against Rheumatism response criteria. RA patients were genotyped for -174G/C IL-6 gene polymorphism by the PCR–RFLP method, and influence of genotype at this polymorphism to clinical response to etanercept was assessed. After 12 months of treatment, the percentage of responders (patients who had DAS28 improvement >1.2) was significantly increased in patients carrying the IL-6 -174G/G genotype (95.7 %) compared with those with the G/C (75.6 %) or CC (44.4 %) genotype (p = 0.006 by Chi-square test). No significant difference in the mean values of DAS28 improvement was observed between groups with different genotype. RA patients with an IL-6 -174GG genotype respond to etanercept better than patients with GC or CC genotype. This finding, if confirmed in future studies, suggests that the -174G/C IL-6 polymorphism may be a genetic marker of responsiveness to tumor necrosis factor-alpha (TNF-α) blockers in RA.