Meta-analyses of the associations between four common TGF-β1 genetic polymorphisms and risk of colorectal tumor.

The associations between four common genetic polymorphisms of transforming growth factor-β1 (TGF-β1 -509 C > T, +869 T > C, +915 G > C, and -800 G > A) and risk of colorectal tumor (including adenoma and cancer) have been widely studied. To date, no conclusions could be available because of controversial results reported. Thus, we conducted a meta-analysis to further assess the associations. We searched the databases of Medline, Embase, and Wangfang to identify eligible studies, and latest update was on January 1, 2012. Odds ratio (OR) and 95% confidence interval (95%CI) were calculated to present the associations. Our meta-analysis indicated that TGF-β1 -509 C > T, +869 T > C, +915 G > C, and -800 G > A were not associated with risk of colorectal adenoma (OR = 0.89 for C carriers vs. TT for -509 C > T, 1.03 for C carriers vs. TT for +869 T > C, 1.09 for C carriers vs. GG for +915 G > C, and 1.19 for A carriers vs. GG for 800 G > A). However, C allele of TGF-β1 -509 C > T and A allele of -800 G > A were associated with increased risk of colorectal cancer (CRC), and OR (95%CI) was 1.23 (0.99-1.52) for CC vs. TT for -509 C > T and 6.64 (3.46-12.72) for A carriers vs. GG. The positive association between -509 C allele and risk of CRC was more obvious when subgroup analyses were conducted for population-based and large sample-sized studies as well as Caucasians. In contrast, we did not observed any associations between TGF-β1 +869 T > C, +915 G > C, and risk of CRC. This study indicated that C allele of TGF-β1-509 C > T and A allele of -800 G > A might contribute to the increased risk of CRC, and could be used as two of genetic marks for screening individuals at high risk of CRC. Because of modest limitation, large sample-sized studies were required to confirm the findings.