ERBB3 and cancer: One of the major advancements in the targeted therapy of cancers, including CRC, was the discovery of the type I growth factor receptor family of tyrosine kinases, which consists of EGFR (HER1, ErbB-1), HER2 (neu, ErbB-2), HER3 (ErbB-3), and HER4 (ErbB-4), of which, EGFR and HER2 are the most extensively studied receptors [12,13,14].