STAT3 and breast cancer: STAT3 also mediates oncogenesis by recruiting DNA methyltransferase 1 (DNMT1) to gene promoters to silence tumor suppressor genes, such as PTPN6, IL-2Rγ, CDKN2A, DLEC1, and STAT1 by CpG methylation in malignant T lymphocytes and breast cancer cells [59, 60] (Fig. 5f).