TGFB1 and breast cancer: When stratified by family history of breast cancer, we observed that a 10 kg/m2 increase in BMI from age 10 was associated with a 6.6% increase in TGFB1 gene expression among women with a positive family history of breast cancer and a 0.8% decrease among women with no family history of breast cancer (pinteraction = 0.03).