In a study to determine how c-erbB-2 contributes to lung carcinogenesis, an analysis of E6 cells, a tumorigenic, clonal isolate of human bronchial epithelial cells (Beas-2B) engineered to overproduce c-erbB-2, shows that these cells also produce TGF-alpha. Transfection of these cells with an antisense TGF-alpha construct yielded clones which no longer produced detectable TGF-alpha protein. These cells were no longer tumorigenic. In complementary experiments, nontumorigenic E2 clones which overexpress c-erbB-2 were transfected with a sense TGF-alpha construct. Clones isolated from this transfection expressed higher levels of TGF-alpha than the parental E2 but significantly less than E6. These clones were not tumorigenic. Further characterization of the erbB family members expressed in these cells, indicated that erbB-1 (EGFR), erbB-3 and erbB-4 are expressed in all clones. RT-PCR studies show a low level of expression of heregulin. Immunoprecipitation analysis of complexes of c-erbB-2 revealed that this molecule was found in a complex with the EGF receptor in cells producing high levels of TGF-alpha.
