ERBB2 and breast cancer: Gossypol causes anti-proliferative activity and apoptosis in breast cancer cells (Gilbert et al., 1995; Ye et al., 2010; Messeha et al., 2019), and when R-(-)-gossypol (AT-101) is administered in conjunction with trastuzumab in HER-2 positive breast cancer cell line, it causes synergistic cytotoxicity and apoptosis (Bulut et al., 2020).