In a study of 577 BC patients, HER2 expression was positively correlated with ALDH1+ BCSCs [60]; enforced HER2 expression in BC cell lines increased ALDH1+ BCSCs, which was blocked by trastuzumab (Herceptin, a monoclonal anti-HER2 antibody) [168]. The gene discussed is ALDH1A1; the disease is breast cancer.