STAT3 and breast cancer: In neuroblastoma and mesothelioma, ERK5 is activated by PI3K/AKT signaling; in breast cancer, STAT3 enhances MEK5 expression; and in renal epithelial cells, TGFβ1-induced MEK5/ERK5 activation occurs through ALK and p38 MAPK, facilitating MEF2C-mediated transcription.