Abstract 5801: Identifying vulnerabilities to immune checkpoint inhibitors of oncogene-addicted non-small cell lung cancer subgroups

Abstract Purpose: Even though the treatment with PD-(L)1 axis blockers induces tumor response in approximately 20% of unselected patients with advanced Non-Small Cell Lung Cancer (NSCLC), patients harboring EGFR alterations have poor outcomes with anti-PD-(L)1 antibody. Targeted therapy with Tyrosine Kinase Inhibitors (TKIs) is the standard of care for patients with advanced-stage-EGFR-mutant. However, resistance to kinase inhibitors is almost inevitable. EGFR-mutant NSCLCs typically have a low TMB, low levels of CD8+ T cells and natural killer cell infiltration, a limited T cell receptor repertoire and abundant infiltration of Treg cells, which might account for the poor efficacy of Immune Checkpoint Inhibitors (ICIs) of this genomic subtype. We propose to investigate potential vulnerabilities and opportunities to overcome primary resistance to ICIs conferred by oncogene addiction in these patients. Methods: In order to identify mechanisms involved in the restricted immune response of this subgroup we are performing a sub-genome-scale in vivo CRISPR/Cas9 screening. Murine cell lines were derived from the genetically-engineered mouse model of Egfr-mutant lung cancer bearing exon 19 deletions or the L860R missense mutation. Genetically modified cell lines with the CRISPR/Cas9 library will be implanted subcutaneously into the flank of immunocompetent mice. A group of mice will then receive ICI treatment at different days post-tumor challenge and sgRNA abundances between the different mouse groups will be compared. Results: Both oncogenic Egfr mouse cell lines were sensitive to an EGFR-specific TKI, showing a decrease in phospho-Y1068-EGFR. These results demonstrate the oncogenic dependence on EGFR signaling for growth.In addition, Egfr-del19 or Egfr-L860R tumors injected subcutaneously were resistant to anti-PD1 and/or anti-CTLA-4 blocking antibodies, similar to the lack of response to human EGFR-mutant NSCLC to immunotherapy.Nowadays, we are conducting the in vivo sub-genome-scale screens and quality control analyses indicated excellent screen performance. Indeed, the vast majority of sgRNAs were well represented in all conditions and recovered within replicates. Conclusion: We expect to identify new resistance mechanisms that could result in novel treatment strategies for these NSCLC subgroups. The identification of these targets will provide the opportunity to reprogram the tumor microenvironment and to improve the efficacy of immunotherapy in a subset of patients with lung adenocarcinoma. Citation Format: Inés Díaz-Cano, José Gracia, Patricia Cozar, Belén Revuelta, Nuria Carrizo, Juan Dubrot, Luis Paz-Ares, Itziar Otano. Identifying vulnerabilities to immune checkpoint inhibitors of oncogene-addicted non-small cell lung cancer subgroups [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5801.