ERBB3 and hypopharyngeal carcinoma: The diabody, composed of the antigen-binding sites of a humanized cetuximab (IgG hu225) and IgG 3-43, which target EGFR and HER3, respectively, has been reported to downregulate p-EGFR (Y1068) and p-HER3 (Y1289), as well as their downstream effectors p-AKT (T308) and p-ERK (T202/Y204), in FaDu, a hypopharyngeal carcinoma cell line.