Establishment and characterization of EGFR Tyrosine Kinase Inhibitor-resistant lung cancer cell lines

Anti-EGFR therapy is among the most promising molecular targeted therapies against cancer developed in the past decade. The small molecule tyrosine kinase inhibitors (TKI), Erlotinib and Gefitinib, are effective treatments for Non Small Cell Lung Cancer (NSCLC) with EGFR activating mutations, but these tumors invariably develop drug resistance. For acquired resistance, secondary mutation in the EGFR gene or alternative EGFR-independent activation of cell growth signaling pathways is well known. However in 30-40% of the cases of EGFR TKI-resistance, the mechanism underpinning the therapeutic resistance is unknown. To explore additional mechanisms of Erlotinib resistance, we generated resistant clones of the Erlotinib hypersensitive NSCLC cell line, HCC827 and HCC4006, by exposing these cells to high concentration (1mM) or increasing concentrations of Erlotinib for 4 months. The resultant cell lines, were resistant to Erlotinib and Gefitinib in vitro (IC50>10 ?M) but sensitive to Paclitaxel. Molecular and biochemical characterization - including in vitro and in vivo (mouse xenografts) functional studies, CGH array and gene-expression profiling - are still in progress. Preliminary analyses indicates that: a) the resistant cell lines lack the common secondary EGFR mutation T790M and KRAS mutations; b) the MET proto-oncogene is amplified in some resistant cell lines; c) some resistant cell lines have overexpression of selected tyrosine kinase receptors; d) some resistant cell lines have morphological and molecular marker changes compatible with an epithelial-to-mesenchymal transition (EMT).