HER3/ERBB3 is a member of the family of ERBB receptor protein tyrosine kinase family, but lacks tyrosine kinase activity. The phosphoric acidization of ERBB3 depends on the combination of other ERBB tyrosine kinase. When combined with ligands, an heterodimers is formed between ERBB3 and other ERBB proteins. ERBB3 is widely expressed in human adult tissues, including cells of the gastrointestinal, urinary, respiratory, reproductive tracts, skin, endocrine and nervous systems. ERBB3 is highly expressed in many cancer cells, such as breast, ovarian, lung, colorectal, melanoma, head and neck, cervical and prostate cancers.