Overexpression of c-erbB-3 in various stages of human squamous cell carcinomas.

Amplification of the c-erbB-3 gene and the expression of its mRNA and protein in human squamous cell carcinomas (SCC) were analyzed. Although no amplification of the c-erbB-3 gene was observed, overexpression of its mRNA was observed in SCC by RT-PCR. The expression of this gene in SCC was 15-50 times higher than in normal fibroblasts. Overexpression of the secreted type of erbB-3 mRNA was also observed in all SCC. Moreover, overproduction of the c-erbB-3 protein was also detected in SCC by dot blot analysis using anti-c-erbB-3 monoclonal antibodies. In nude mice, the expression of c-erbB-3 mRNA was higher in metastatic tumors compared with primary tumors. These results suggest that both the transmembrane and secreted types of c-erbB-3 play a significant role in the formation and development of SCC.