Approaches with the knockdown of GRP78 helped to elucidate that this chaperone is required for the self-renewal ability and radioresistance in CSC-like cell fractions from breast cancer MCF-7 cells [231] and also for chemo- and radioresistance in CD24(−)/CD44(+) stem cells of head and neck cancer [214]. This evidence concerns the gene CD44 and breast carcinoma.