ERBB2 and cancer: Its function in HER2-amplified cancers is engaged in a ligand-independent manner, and antibodies targeting its extracellular domain (ECD) are unable to inhibit its signaling functions in these cancers (Blackburn et al., 2012; Garner et al., 2013; Kugel et al., 2014; McDonagh et al., 2012; Schoeberl et al., 2010; Campbell et al., 2022).