To gain further insight into how FOXO3a suppresses breast cancer metastasis, we examined the effect of FOXO3a on many microenvironmental genes, including TGF-β, TNF-α, EGF, FGF, PDGF, VEGF, and IGF, which have been implicated in promoting metastasis (Supplementary Fig. 3A). This evidence concerns the gene TNF and breast cancer.