Abstract A139: Mechanism of treatment-induced drug resistance in lung cancer (2018)

Abstract Objectives: Lung cancer is the number one cause of cancer-related deaths. About 20% of all non-small cell lung cancer (NSCLC) patients are expected to harbor an Epidermal Growth Factor Receptor (EGFR) activating mutation. First- and second-generation EGFR tyrosine kinase inhibitors (TKIs) are clinically approved to treat advanced NSCLC patients. However, despite the initial clinical responses to these EGFR-targeted therapies, long-term efficacy is not possible because acquired drug resistance hampers the effectiveness of these therapies. Even with gradually increasing knowledge, many routes to resistance have yet to be discovered. We found that a polymeric nanofibrous scaffold platform established in our laboratory allows growth of three-dimensional (3D) tumor-like aggregates (tumoroids), which resemble in vivo tumors. We hypothesize that 3D scaffold will allow us to elucidate EGFR TKI resistance mechanisms and help design more efficient treatment strategies to block resistance. Methods: To investigate drug resistance to EGFR TKIs, we have developed lapatinib-resistant human lung cancer cell lines as models for de novo drug resistance. To derive drug-resistant (DR) cells, three human lung cancer cell lines with different EGFR-activating mutations were grown in static concentrations of lapatinib for up to 30 days. The drug sensitivity of the parental and DR cells on both the monolayer and 3D scaffold was determined by testing a panel of standard-of-care chemotherapeutics along with EGFR TKIs. Mass spectroscopy was used to determine the relative levels of certain key proteins being expressed in the H1975 and lapatinib DR-H1975 cell lines. Expression of intriguing proteins found in the mass spec data was confirmed and validated in our EGFR TKI resistant models using other methods, including Western blotting and mRNA transcript analysis. Inhibitors, as well as siRNA, of selected proteins were then used to determine if these proteins played a role in EGFR TKI resistance. Results: A comparison of the drug sensitivity showed that parental cells were at least 3-fold more sensitive to the EGFR TKIs compared to the DR cells. The sensitivity to EGFR TKIs was further decreased when DR cells were cultured on our fibrous 3D scaffold. EGFR TKI resistant cells were also resistant to other anticancer agents, such as taxol and gemcitabine. Data mining the significantly differentially expressed proteins list generated by the mass spectroscopic analysis revealed that the protein expression is skewed in lapatinib DR-H1975 cell line as compared to the H1975 cell line. Proteins involved in all aspects of homeostasis including metabolism, biosynthesis, and oxidative regulation were significantly upregulated in the lapatinib-resistant cell line. We are currently working to determine if all the EGFR TKI resistant cell lines are producing similar mechanisms of resistance. Conclusions: Studying the cellular effects of acquired EGFR TKI resistance, as well as the mechanism through which this resistance is maintained, can help to better understand how lung cancer cells become drug resistant to EGFR TKIs and help strategize potential ways of overcoming this resistance. Research supported by: R01CA152005, HHSN261201400022C, HHSN261201400028C. Citation Format: Mark C. Howell, Ryan Green, Rajesh Nair, Stanley Stevens, Jit Banerjee, Shyam Mohapatra, Subhra Moahpatra. Mechanism of treatment-induced drug resistance in lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A139.