ERBB2 and breast cancer: Human BC cell lines MCF-7, T-47D [both hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated], MDA-MB-231 and BT-549 (both triple-negative, wild-type PIK3CA) were exposed to a combination of low-dose VRL and alpelisib for 3 and 7 days.