Short Communication Genetic Polymorphisms of the Transforming Growth Factor-b1 Gene and Breast Cancer Risk: A Possible Dual Role at Different Cancer Stages

Transforming growth factor-B (TGF-B) inhibits the proliferation of carcinomas in early stages of breast cancer, whereas it promotes tumor growth and metastasis in later stages of cancer. We evaluated a possible association between TGF-b1 gene polymorphisms and breast cancer risk in a populationbased case-control study of Chinese women living in Shanghai, which included 1,127 breast cancer cases and 1,228 population controls. Two polymorphisms, C-509T and T+29C, were in strong linkage disequilibrium. There were no overall differences in the genotype distribution of T+29C polymorphisms of the TGF-b1 gene among cases and controls. However, the distribution of the high-activity C allele of T+29C polymorphisms differed by cancer stages (P trend = 0.02). This allele was associated with decreased risk of early-stage breast cancer [stages 0 and I; odds ratio (OR), 0.73; 95% confidence interval (95% CI), 0.54-0.99], and the OR was further reduced to 0.66 (95% CI, 0.45-0.96) for those homozygous for this allele (P trend = 0.03). On the other hand, the same allele was associated with nonsignificantly increased risk of breast cancer with advanced stages III and IV (OR, 1.33; 95% CI, 0.81-2.18), which differed significantly from that observed for early-stage cancer (P = 0.04). This result suggests a possible dual effect of TGF-B1 shown by in vitro experiments and provides an explanation for some of the inconsistent findings from previous epidemiologic studies that did not evaluate this association by cancer stage. (Cancer Epidemiol Biomarkers Prev 2005;14(6):1567–70)