Toll-like receptor 4 Asp299Gly and Thr399Ile polymorphisms in cancer: A meta-analysis

Toll-like receptor 4 (TLR4) is critical in the recognition of Gram-negative bacteria serving as a key immune system effector. Recently, a number of case-control studies were conducted to investigate the association between TLR4 gene polymorphism and cancer risk, especially Asp299Gly and Thr399Ile polymorphisms. However, published data were still conflicting. In this paper, we summarized 9463 cancer cases and 10,825 controls from 22 studies and attempted to assess the susceptibility of TLR4 gene polymorphism to cancers by a synthetical meta-analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the relationship. Our results suggested that Asp299Gly represented a risk factor on cancers in digestive system (G allele versus A allele, OR = 1.64, 95% CI: 1.02–2.64; GA + GG versus AA, OR = 1.64, 95% CI: 1.00–2.71) but tend to have a protective effect on prostate cancer (GG versus AA, OR = 0.37, 95% CI: 0.14–0.98; GG versus GA + AA, OR = 0.37, 95% CI: 0.14–0.98). Thr399Ile polymorphism was significantly associated with an elevated cancer risk in overall analysis (T allele versus C allele, OR = 1.72, 95% CI: 1.27–2.33; TC versus CC, OR = 1.63, 95% CI: 1.18–2.26; TT + TC versus CC, OR = 1.70, 95% CI: 1.24–2.34) and especially in gastrointestinal subgroup (T allele versus C allele, OR = 2.01, 95% CI: 1.40–2.89; TC versus CC, OR = 1.86, 95% CI: 1.26–2.74; TT + TC versus CC, OR = 1.97, 95% CI: 1.35–2.88). Further prospective researches with larger numbers of worldwide participants are warranted to draw comprehensive and true conclusions.