STAT3 and breast cancer: The functional relevance of the CD44s isoforms has been highlighted in malignancies other than colon cancer, namely in prostate (Lu et al., 2015) and breast cancer where it activates, among others, PDGFRβ/Stat3 and Akt signaling to promote EMT and CSC traits (Brown et al., 2011; Zhang et al., 2019a).