Genetic variation in TNFα, PPARγ, and IRS-1 genes, and their association with breast-cancer survival in the HEAL cohort.

Abstract

Tumor necrosis factor-α (TNF-α), peroxisome proliferator-activated receptor-γ (PPARγ), and insulin receptor substrate-1 (IRS-1) are associated with obesity, insulin resistance, and inflammation. Few data exist on associations between polymorphisms in these genes and mortality in breastcancer survivors. We investigated associations between TNF-α -308G>A (rs1800629); PPARγ Pro12Ala (rs1801282); and IRS-1 Gly972Arg (rs1801278) polymorphisms and anthropometric variables, circulating levels of previously measured biomarkers, and tumor characteristics in 553 women enrolled in the Health, Eating, Activity, and Lifestyle Study, a multiethnic, prospective cohort study of women diagnosed with stage I-IIIA breast cancer between 1995 and 1999 (median follow-up 14.7years). Using Cox proportional hazards models adjusted for possible confounders, we evaluated associations between these polymorphisms and mortality. Carriers of the PPARγ variant allele had statistically significantly lower rates of type 2 diabetes (P=0.04), lower BMI (P=0.01), and HOMA scores [P=0.004; non-Hispanic White (NHWs) only]; carriers of the TNF-α variant A allele had higher serum glucose (P=0.004, NHW only); and the IRS-1 variant was associated with higher leptin levels (P=0.003, Hispanics only). There were no associations between any of the polymorphisms and tumor characteristics. Among 141 deaths, 62 were due to breast cancer. Carriers of the TNF-α-variant A allele had a decreased risk of breast-cancer-specific mortality [hazard ratio (HR) 0.30; 95% confidence interval (CI) 0.10-0.83] and all-cause mortality (HR 0.51; 95% CI 0.28-0.91). Neither the PPARγ nor the IRS-1 polymorphism was associated with mortality outcome. The TNF-α -308 G>A polymorphism was associated with reduced breast-cancer-specific and all-cause mortality.