STAT3 and breast cancer: Because miR-96 negatively regulates PTPN9 expression, PTPN9 directly interacts with STAT3 and mediates its dephoshorylation23, while phosphorylated STAT3 promotes miR-96 expression30, 46, miR-96, PTPN9 and STAT3 may form a double-negative feedback loop (equal to positive feedback) controlling cellular phenotypes in breast cancer.