An updated meta-analysis of transforming growth factor-β1 gene: Three well-characterized polymorphisms with asthma

The association between TGF-β1 polymorphisms and asthma risk has been widely reported, but results were controversial. We performed this meta-analysis based on the Preferred Reporting Items for Systematic Reviews and meta-analyses statement (PRISMA). Electronic database of Pub Med, Web of Science, CBM, and CNKI were searched for eligible articles published up to September, 2013. The effect summary odds ratio (OR) and 95% confidence intervals were obtained. Finally, a total of 20 articles were identified, 17 studies with 3694 cases and 5613 controls for C-509T polymorphism, 7 studies with 1109 cases and 1098 controls for T869C polymorphism and 5 studies with 849 cases and 829 controls for G915C polymorphism. For C-509T, significant associations with asthma were found in Asians (TT+TC vs. CC: P=0.004, OR=1.43, 95%CI=1.12-1.81, P_{heterogeneity}=0.001) and in Caucasians (P=0.05, OR=1.16, 95%CI=1.00-1.34, P_{heterogeneity}=0.36). With respect to T869C, a small significant association was observed in overall analysis of allele contrasts(C vs. T: OR=1.14, 95%CI: 1.01-1.29, P=0.03) and homozygote comparison (CC vs. TT: OR=1.29, 95%CI: 1.00-1.65, P=0.05), but no significant risks were found among Caucasian population and Asian population. For G915C polymorphism, no significant association with asthma risk was demonstrated in overall analysis and subgroup analyses according to ethnicity for all genetic models. This meta-analysis suggested that TGF-β1 C-509T and T869C polymorphisms may be risk factors for asthma.