Abstract 1838: Mechanism of EGFR and c-Met TKI resistance and role of co-expression of EGFR and c-Met in non-small cell lung cancer patients

Current EGFR/c-Met tyrosine kinase inhibitor (TKI) combination therapies are shown to be susceptible to acquired resistance in the majority of NSCLC patients. To understand how cells develop EGFR/c-Met TKI resistance, we use three model NSCLC cell lines: H2170, H358 and H1975. H2170 and H358 cell lines express high levels of EGFR and c-Met and are EGFR wild-type. These cell lines were made resistant to the EGFR TKI erlotinib, the c-Met TKI SU11274 and a combination of both by exposure to increasing concentrations of these TKIs. The H1975 cell line is positive for two EGFR TKD mutations (T790M and L858R) which confer resistance to erlotinib. Studies have shown that EGFR/c-Met TKI resistant cells may use alternative signaling pathways to activate downstream transcription/translation proteins previously activated by EGFR and c-Met signaling. The Wnt/β-catenin and mTOR pathways are demonstrated to have significant roles in cell survival, resistance and tumorigenesis in NSCLC. Several EGFR/c-Met-linked proteins in these two signaling pathways were differentially modulated in H2170 and H358 resistant lines. The Wnt signaling transducer β-catenin plays a role in cellular proliferation and death and its deregulation is implicated in lung cancer. Protein kinase GSK-3 also plays an important role in lung cancer and its inhibition by Wnt results in mTOR activation. It is encoded by two genes, GSK-3α and GSK-3β. GATA-6 is a transcriptional activator of Wnt and is also implicated in several cancers. Active β-catenin was found to be 2 to 4-fold upreglated in H2170 SU11274-resistant (SR) cells and 2 to 20-fold upreglated in H2170 erlotinib-resistant (ER) cells, in the presence and absence of TKIs and growth factor ligands, when compared to naive H2170 cells. GATA-6 was found to be 1.5 to 4-fold upreglated in H2170 SR cells and 2 to 3-fold upreglated in H2170 ER cells. Conversely, p-GSK-3α and p-GSK-3β were found to be 1.2 to 4.8-fold and 1.5 to 10.7-fold downreglated in H2170 SR cells, respectively. These results indicate increased activation of the Wnt/β-catenin and mTOR pathways in TKI resistant cells. We are currently studying the expression of these proteins further in the H1975 cell line. To translate our studies to patients, we are investigating the role of EGFR/c-Met synergism in NSCLC by conducting a retrospective biomarker analysis using IHC on 100 tissue samples from patients with stage 3 and 4 squamous cell and adenocarcinoma. Preliminary results indicate that EGFR and c-Met receptors are co-expressed in lung cancer tissues and we are acquiring data to determine how co-localization and synergism affects patient prognosis. Further studies are being conducted on proteins in the Wnt and mTOR signaling pathways, such as p70S6Kinase, mTOR, β-Catenin and Axin-2, and their involvement in patient prognosis and resistance. This study may provide clinicians with novel targets for improving treatment options for future NSCLC patients. Citation Format: Gregory Michael Botting, Kymberly Harrington, Caleb Shearrow, Zachary Crees, Jennifer Girard, Kavin Arasi, Neelu Puri. Mechanism of EGFR and c-Met TKI resistance and role of co-expression of EGFR and c-Met in non-small cell lung cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1838. doi:10.1158/1538-7445.AM2014-1838