Expression of a neu/c-erbB-2-like product in neuroendocrine cells of mammals

The neu/c-erbB-2 oncogen encodes a 185 kDa protein closely homologous to th e epidermal growth factor receptor. The protein product (p185) is a glycopr otein with an external domain and an internal domain with tyrosine kinase a ctivity. Amplification and/or overexpression of p185 is related to several human adenocarcinomas. Subsequent studies demonstrated its presence in cert ain neuroendocrine (NE) neoplasms, including phaeochromocytomas, insulinoma s and medullary thyroid carcinomas. However, relatively little is known abo ut its role in normal cell growth regulation and development. Therefore, ou r objetive was to determine whether neu/c-erbB-2 was expressed in normal NE tissues of different mammals, specially in humans, as it was in their neop lasms. We have examined by immunohistochemistry different endocrine glands (thyroid, pancreas, suprarrenal and hypophysis) and the small intestine of human beings, rats and guinea pigs, using two polyclonal antibodies raised against the intracytoplasmic part of the protein, and specific antigen abso rption controls. We have found that a neu/c-erbB-2-like product occurs in a ll normal NE tissues examined: C cells of the thyroid gland, chromaffin cel ls of the adrenal medulla, pancreatic islets, enteroendocrine cells of the small intestine and, finally, scattered cells of the adenohypophysis, accor ding to a typical granular immunohistochemical pattern. Our results indicat e that normal NE cells share a new common antigen in their cytoplasms, a ne u/c-erbB-2-like product, with a similar immunostaining pattern to that pres ented by the neoplasms derived from them.