ERBB2 and breast cancer: Subsequently, we have accumulated compelling evidence and notably, we found that treatment of breast cancer cells representative of the TNBC subtype or of the HER2-E subtype significantly depleted the highly tumorigenic CD44+/CD24− and ALDH+ BCSC subpopulations and induced their differentiation into the least tumorigenic phenotype (ie CD44−/CD24− and ALDH- resulting in suppression of their tumorsphere formation/self-renewal capacities (53, 76).