Sequential expression of myc-, ras-, oncogene products and EGF receptor during DMBA-induced tongue carcinogenesis.

The mechanism leading to development of oral cancer has not been completely understood. It is currently believed that alternation of a number of genes can result in the development of epidermoid carcinomas. In this investigation, we used a 9,10-dimethyl 1,2-benzanthracene (DMBA)-induced carcinogenesis in a hamster tongue model to investigate the expression of c-myc, c-Ha-ms proteins and epidermal growth factor receptor (EGFr). During the DMBA-carcinogenesis of the tongue, the number of c-myc protein positive cells were increased in epithelial dysplasia and elevated throughout the process of tumorigenesis. The expression of c-Ha-ras protein was detected in normal epithelium. The level of c-Ha-ras protein expression was decreased in the dysplastic stage, and it was almost negative in squamous cell carcinomas. Detection of EGFr overexpression occurred only after 1-4 weeks of DMBA treatment, at a very early stage of tumor development, and increased through carcinogenesis varying individually within the malignant tissues. These results suggest that c-myc protein and c-Ha-ras protein expression may have an important role in malignant transformation, and the overexpression of EGFr can be correlated to very early stages of tumor development in the DMBA-induced in vivo tongue carcinogenesis.