Abstract 1207: Transactivation of EGFR/ErbB2 receptor by TNF abrogates TNF-induced apoptosis in bronchial epithelial cells and non-small cell lung cancer cells
Authors: Yamaoka Toshimitsu , Polk D. Brent , Murata Yasunori , Ohki Yasunari , Kusumoto Sojiro , Sugiyama Tomohide , Shirai Takao , Okuda Kentaro , Ohnishi Tsukasa , Hirose Takashi , Ohmori Tohru , Adachi Mitsuru 
Published: February 2011

Abstract
[Background] Epidermal Growth Factor Receptor (EGFR) and other ErbB receptors; ErbB2-4, through cytokine and growth factor stimulation, are upregulated in pneumonitis and lung cancer, suggesting that the activation of ErbB receptors is response to pneumonitis and lung cancer in humans. TNF is a cytokine with many biological properties including both anti- and pro-apoptotic signaling pathways. However, the molecular switch, which determines TNF regulation of these two different functions is not well characterized. We previously presented that TNF transactivated both EGFR and ErbB2 via Src kinase activity that promote the survival response to TNF. In the present study, we tested the hypothesis that EGFR/ErbBs activity regulates TNF-mediated bronchial epithelial and non-small cell lung cancer cell survival.
[Method] Bronchial epithelial, Beas-2B cells and non-small cell lung cancer, NCI-H292 cells were used for these studies. Cells were treated with TNF (100 ng/ml) in the presence of either PI 3-kinase inhibitor (wortmannin or LY294002), MAP kinase inhibitor (U0126), MMP inhibitor (GM6001 or TAPI-1 or −2) or EGFR tyrosine kinase inhibitor (Erlotinib). Apoptosis and signal transduction pathway activation were determined by TUNEL staining and Western blot analysis, respectively.
[Results] In Beas-2B and NCI-H292 cells, TNF-induced apoptosis was significantly enhanced in the presence of EGFR tyrosine kinase inhibitor. Similarly, treatment of Beas-2B and NCI-H292 cells with TNF failed to increase apoptosis except in the presence of PI 3-kinase inhibitor, which increased the apoptotic response 10-fold. Treatment with TNF in the presence of MAP kinase inhibitor, did not increase apoptosis. In Beas 2B and NCI-H292 cells, TNF stimulated EGFR/ErbB2 phosphorylation within 5 min. EGFR/ErbB2 transactivation by TNF was blocked with GM6001 and TAPI-1, which inhibited MMP activity, especially TACE. Furthermore, in the presence of neutralizing antibodies for HB-EGF, TGF-α and EGF, EGFR/ErbB2 transactivation by TNF was inhibited, suggesting TNF-stimulated EGFR/ErbB2 transactivation via TACE cleavage of HB-EGF, TGF- α and EGF abrogates TNF-induced apoptosis in human bronchial epithelial cell and lung cancer cell. TNF stimulated AKT activation via EGFR tyrosine kinase activation. Akt was shown to be a downstream target of TNF-activated EGFR/ErbB2.
[Conclusion] We demonstrate that TNF stimulates EGFR/ErbB2 transactivation via ADAM/MMP in a manner that requires HB-EGF, TGF- α and EGF with AKT as a critical downstream regulator of TNF-induced anti-apoptosis. This novel observation has significant implications for understanding the role of EGFR/ErbB2 in maintaining human bronchial epithelial cell homeostasis in an environment of inflammation, injury/repair, such as inflammation-associated carcinogenesis and tumor progression.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1207.