Specifically MMTV-TGF-α mice crossed with leptin deficient mice fail to develop tumors [218,219] and treatment with a leptin antagonist decreases the growth of murine triple-negative breast tumors [220] and 4T1 mammary cancer cell growth via reducing levels of VEGF, pSTAT3 and cyclin D1 [221]. This evidence concerns the gene LEP and breast cancer.