STAT3 and breast cancer: Yang et al. (47) also found that chemotherapy activated the EZH2/STAT3 axis in breast cancer cells, which in turn secreted miR-378a-3p- and miR-378d-rich exosomes that were taken up by surviving breast cancer cells and then activated the WNT and NOTCH stem cell pathways by targeting DKK3 and NAMB, ultimately leading to drug resistance (47).