STAT1 and breast carcinoma: Similarly, human mesenchymal stem cell (MSC)‐derived exosomes could activate Wnt signalling pathway in recipient breast cancer cells and then promote cellular proliferative ability.75 In addition, Boelens et al76 proved that exosomes released from stromal cells can activate STAT1‐dependent antiviral signalling and NOTCH3 pathways in breast cancer cells and regulate stroma‐mediated expansion of therapy‐resistant cells.