Effect of gefitinib on EGFR Mutated Lung Cancer Cell Lines

Abstract

3172 Background: EGFR is frequently overexpressed in many cancerous tumors such as lung, colon, breast and brain. Receptor tyrosine kinase inhibitors (TKI) such as gefitinib (Iressa) and Tarceva have been widely used for targeted therapy in cancer. These drugs inhibit the EGFR kinase activity by binding the ATP pocket within the catalytic domain. The inhibition of EGFR blocks MAP Kinase and PI3K-Akt pathways, and therefore, preventing cell proliferation and tumor growth. Recent clinical studies of patients with NSCLC showed that Tarceva is most effective in population with EGFR mutation. We describe a multiplexed proximity-based eTag assays for EGFR and Her family receptor dimerization following signaling phosphorylations, to study the effect Iressa on EGFR inhibition in lung cancer cell lines with mutant EGFR. Material and Methods: Lung cancer cell lines such as NCI-358 and NCI-1734 expressing wild type EGFR and NCI-1650 expressing mutant EGFR (in-frame deletion delE746-A750) and NCI-1975 expressing EGFR with missense mutation L858R were selected. These cell lines were treated with Iressa for 1–16 h followed by 100 ng/ml of EGF stimulation. EGFR/Her receptors were analyzed for receptor dimerization and downstream signaling pathway activation. Results: Her1/1 and Her1/2 were detected in both wild type and mutant cell cell lines. Upon treatment with Iressa, the EGFR phosphoryltion was inhibited in both wild type and mutant lung cancer cell lines, but the IC50s for cell lines with mutant EGFR were ∼50–100 times lower. Her1/1 and Her1/2 dimerization significantly increased in all cell lines following stimulation with Iressa. The MAP kinase pathway was inhibited upon treatment with Iressa, and like EGFR inhibition, the IC50s for mutant cell lines were 50–100 times lower as compared to wild type cell lines. Conclusion: We used the multiplexed eTag Assay system to study the effect of Iressa on EGFR in model cell lines, which express wild type and mutant EGFR. The results indicated that these EGFR inhibitors are more effective in cells with mutant EGFR. No significant financial relationships to disclose.