Inhibition of the HER2 signaling pathway results in upregulation of HER3 RNA and protein [71,72,73] A study by Al-Akhrass et al. indicated that a feed-forward loop between SorLA and HER3 determines heregulin response and neratinib resistance via the upregulation of HER2 and HER3 [74] Furthermore, it has been demonstrated that treating HER2+ breast cancer cells with the HER2 tyrosine kinase inhibitor lapatinib results in higher HER2/HER3 heterodimerization than prior to treatment [75]. Here, ERBB2 is linked to breast cancer.