Epidermal Growth Factor Receptor (EGFR) mutant lung adenocarcinomas are sensitive to the tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. EGFR is one member of a family of four receptor tyrosine kinases (EGFR, ERBB2, ERBB3 and ERBB4) that can homo- and/or hetero-dimerize leading to activation of the RAS-MAPK and phosphoinositide 3-kinase (PI3K) pathways. In EGFR mutant lung cancer cell lines, ERBB3 has been implicated in activation of the PI3K pathway. However, the requirement for ERBB3 in the initiation, progression and therapeutic response of EGFR mutant tumors remains undetermined. Using genetically engineered mouse models we investigated the contribution of Erbb3 to the development of EGFR-induced lung adenocarcinomas and their response to TKIs. We found that upon conditional deletion of Erbb3 in the lungs of mice that express mutant EGFR tumorigenesis and erlotinib sensitivity were unaffected. In the absence of Erbb3, tumors retained activation of the Pi3k pathway via the adapter proteins Gab1 and Gab2. Acute loss of ERBB3 in human lung adenocarcinoma cell lines with sensitizing EGFR mutations had a modest effect on phosphorylation of AKT and cell viability that varied among cell lines. These data demonstrate that activation of the Pi3k pathway in EGFR mutant tumors is independent of Erbb3 and has implications for the potential of ERBB3 as a therapeutic target in lung cancer. Knowledge of the role EGFR heterodimerization partners play in mutant EGFR-driven lung cancer can help guide the selection of which EGFR family members to target in the treatment of this disease.
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C113.
Citation Format: Xiaoling Song, Pang-Dian Fan, Udayan Guha, David Threadgill, Harold Varmus, Katerina Politi. ERBB3 independent activation of the PI3K pathway in EGFR mutant lung adenocarcinomas. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C113.