Abstract 414: Comprehensive molecular characterization of mechanisms involved in primary resistance to EGFR tyrosine kinase inhibitors
Authors: Coya Juan Manuel , Álvarez Eva , Gómez-Sánchez David , Rosado Aranzazu , Ferrer Irene , Paz-Ares Luis 
Published: June 2022

Abstract
Lung cancer is the leading cause of cancer-related deaths worldwide. Tyrosine kinase inhibitors (TKIs) targeting epidermal growth factor receptor (EGFR) activating mutations have significantly improved patient´s treatment with these alterations. However, 15-20% of EGFR-mutated patients do not respond to the therapy, even harboring the same mutations than responders. Little is known about the mechanisms involved in this primary resistance. This work aims to characterize molecular aberrations in clones with intrinsic resistance to first and third generation EGFR-TKIs generated from non-small cell lung cancer (NSCLC) cell lines. Three Erlotinib-sensitive (HCC827, PC9 and H4006) and one Osimertinib-sensitive (H1975) NSCLC cell lines were used to generate primary resistance models through a pulsatile method in which cells were treated with a high concentration of the TKI during a short period of time. Survivor colonies were individually expanded in the presence of the inhibitor until resistant cell lines were established. Exome, transcriptome and methylome were then analyzed in selected clones. Erlotinib- and Osimertinib-resistant clones exhibited cross-resistance to other EGFR-targeted therapies, such as Afatinib and Cetuximab, but not to the chemotherapeutics Carboplatin or Cisplatin. Among derived clones, we found several genetic alterations in genes associated with TKI acquired resistance, including NTRK1, ARID2, ERBB3, RET, and other genes. MET amplification was exclusively associated with resistant HCC827-derived clones. We also identified non-genetic alterations that include increased expression and over-activation of well-known TKI resistance-associated proteins, such as AXL, FGFR1, or AKT, as well as induction of epithelial-to-mesenchymal transition (EMT) and stemness-related genes. Transcriptome and methylome analyses revealed EMT plasticity among resistant clones that could reflect different EMT states conferring resistance in pre-treated tumors. Molecular inhibition of MET, a recognized resistance mechanism, sensitizes MET-amplified resistant clones to Erlotinib. Combination treatments or genetic inhibitions will be further performed to validate our findings. Taken together, our results suggest that multiple genetic and non-genetic alterations already present before TKI treatment could account for primary resistance. We will employ integrative analysis of our multi-omic data to identify novel targets that allow to overcome EGFR-TKI resistance. Further clinical validation will help to prospectively select the best treatment option for EGFR-mutated patients for the sake of precision medicine.
Citation Format: Juan Manuel Coya, Eva Álvarez, David Gómez-Sánchez, Aranzazu Rosado, Irene Ferrer, Luis Paz-Ares. Comprehensive molecular characterization of mechanisms involved in primary resistance to EGFR tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 414.