Investigational antibodies targeting the ECD of HER3 are similarly effective at inhibiting ligand-driven physiologic HER2-HER3 signaling but are ineffective at disrupting HER2-HER3 signaling or inhibiting the growth of HER2-overexpressing cancer cells (Blackburn et al., 2012; Garner et al., 2013; Kugel et al., 2014; McDonagh et al., 2012; Schoeberl et al., 2010). Here, ERBB3 is linked to cancer.