STAT3 and breast carcinoma: First, this enhanced effect could be induced by an increased secretion of cytokines, as shown for IGF1 [123], which stimulated the invasiveness of breast cancer cells by activating its downstream targets ERK, serine/threonine-protein kinase mTOR, and STAT3 [137], and for leptin, with the expression and activation of its various effector genes [83,124].