Using random-effects meta-analysis on a subsample of 2151 primary breast cancer patients with overall survival data, we found high PPARγ mRNA expression (stratified by study-specific medians) to be associated with improved prognosis (inverse variance-weighted HR = 0.84; 95% CI: 0.71–0.99; P = 0.036) (Figs. S1A and S2A), which lends support to the notion that PPARγ acts as a tumor suppressor gene in breast cancer [3–9]. This evidence concerns the gene PPARG and breast cancer.