Expression of c-erbB proto-oncogene during dimethylbenzanthracene-induced tumorigenesis in hamster cheek pouch.

Repeated local applications of dimethylbenzanthracene (DMBA) induce epidermoid carcinomas in 14 weeks in the cheek pouch of Syrian hamsters. Characteristic histopathological changes similar to the ones observed in human oral cancers can be detected during the development of these tumors in the hamster cheek pouch. Results presented in this report demonstrate that the cellular proto-oncogene c-erbB is amplified and expressed in an epidermoid carcinoma cell line (HCPC-1), derived from one such cheek pouch tumor. The expression of the gene cannot be detected in the untreated cheek pouch tissue whereas the level of expression of the gene is significantly high in the tumor cell line. The expression of c-erbB gene can also be detected in cheek pouch tissue at an early stage (8-9 weeks) of tumor development and in all tumor-bearing tissue of subsequent stages. The stage of expression of c-erbB gene does not coincide with the stage in which extensive hyperplasia of the epithelial cells (5 weeks) is observed. Rather, this coincides with the onset of the early invasion of the connective tissue by the dysplastic epithelium. The expression of c-erbB gene increases in parallel with the increased tumor burden. These results implicate the possible role of c-erbB gene in the genesis of DMBA-induced oral epithelial carcinomas.