ACTIVATION OF EGF RECEPTOR FAMILY MEMBERS SUPPRESSES THE CYTOTOXIC EFFECTS OF TUMOR-NECROSIS-FACTOR-ALPHA

Tumor necrosis factor (TNF)-alpha has a broad range of biological acti vities, which depend heavily on cell type and physiological condition. In a panel of human tumor cell lines we analyzed expression of the re ceptor tyrosine kinases EGFR, ErbB2 and ErbB3, and the response to TNF -alpha. Among the cell lines tested those resistant to TNF-alpha were found to express high levels of either EGFR, or ErbB2 and ErbB3. In TN F-sensitive breast and cervical carcinoma cells activation of EGFR or ErbB2 by the exogenous growth factors EGF and heregulin beta 1 resulte d in a significant increase in the number of cells surviving TNF-alpha treatment. In contrast, inhibition of EGFR activation in TNF-resistan t breast carcinoma cells by the novel antagonistic anti-EGFR antibody 14E1 sensitized the cells to the cytotoxic effects of TNF-alpha. A bac terially expressed fusion protein consisting of a 14E1 single-chain (s c) Fv antibody fragment linked to human TNF-alpha retained TNF-alpha a ctivity. This scFv(14E1)-TNF-alpha molecule localized specifically to EGFR on the surface of tumor cells and activated the NF-kappa B pathwa y in co-cultured T cells, as demonstrated by electrophoretic mobility shift assays.