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Background Oncogenic RAS mutations are prevalent in solid tumors and play a central role in driving immune evasion. While RAS inhibitors (RASi) have shown promise in reshaping the tumor microenvironment—most notably by enhancing T cell infiltration—clinical responses remain inconsistent and often transient due to rapid emergence of resistance. 1 A largely uncharted aspect of this resistance lies in how RAS signaling influences antigen presentation, a key determinant of immune recognition and T cell activation. Recent insights reveal that RAS interacts with metabolic pathways—including ferroptosis, iron homeostasis, and lipid metabolism—that are not only vital for tumor survival but also tightly linked to the immunopeptidome.2 We hypothesized that RAS inhibition leads to distinct changes in the MHC-presented peptide landscape, potentially unveiling immunogenic vulnerabilities that can be exploited for combination immunotherapy.Methods We utilized a combination of cultured cells, syngeneic transplant models, and GEMMs (Kras^LSL-G12D; p53^fl/fl) treated with clinically relevant RAS inhibitors. Immunopeptidomics was performed via MHC-I and MHC-II immunoprecipitation followed by LC-MS/MS peptide sequencing. To integrate antigen presentation with translational dynamics, we conducted ribosome profiling in parallel.Results RAS inhibition dramatically reshapes the tumor immunopeptidome, revealing both treatment-specific and treatment-induced antigens. We identified unique peptides selectively presented upon RASi treatment in both LUAD, PDAC, and melanoma models. Comparative analysis between in vitro and in vivo systems revealed context-dependent peptide repertoires, underscoring the influence of the tumor microenvironment on antigen presentation.Integration with ribosome profiling uncovered key metabolic adaptations following RAS inhibition, including compensatory changes in translation that affect the immunopeptidome. A subset of RASi-induced peptides were prioritized based on presentation frequency, therapeutic window, and predicted immunogenicity. Immunological assays confirmed several peptides to be immunogenic, supporting their candidacy as immunotherapy targets.Conclusions This work uncovers a previously underappreciated layer of immune modulation by RAS signaling, demonstrating that RAS inhibition not only disrupts oncogenic signaling pathways but also reprograms antigen presentation. We are building a comprehensive database of RASi-induced tumor antigens with high therapeutic potential. Ongoing studies include mechanistic dissection of altered antigen processing, in vivo validation through peptide-based vaccines, and leveraging TCR mimetic scFvs to target newly revealed MHC-bound peptides. By linking oncogene-driven metabolism to immune recognition, our findings offer a roadmap for rational design of combination therapies that synergize RAS inhibitors with precision immunotherapies—advancing the goal of durable tumor regression in RAS-driven cancers.References Punekar SR, Velcheti V, Neel BG, et al. The current state of the art and future trends in RAS-targeted cancer therapies. Nat Rev Clin Oncol 2022;19:637–655. https://doi.org/10.1038/s41571-022-00671-9Zhou Q, Meng Y, Li D, et al. Ferroptosis in cancer: from molecular mechanisms to therapeutic strategies. Sig Transduct Target Ther 2024;9:55. https://doi.org/10.1038/s41392-024-01769-5Ethics Approval All animal studies were conducted in accordance with the ethical standards and guidelines of the Moffitt Cancer Center‘s Institutional Animal Care and Use Committee (IACUC). Protocols were approved by the IACUC under protocol R IS00013155, and all procedures adhered to the U.S. Public Health Service Policy on Humane Care and Use of Laboratory Animals and the NIH Guide for the Care and Use of Laboratory Animals.