Abstract 5356: Wild type Kirsten rat sarcoma (Kras) activation drives evasion of interferon-mediated immunity in hepatocellular carcinoma

Abstract Background: Immune checkpoint inhibitors (ICIs) exhibit heterogeneous efficacy in patients with advanced hepatocellular carcinoma (HCC). Currently, there are no effective biomarkers to select patients who could benefit the most from ICIs or to predict response outcomes. Increasing evidence indicates that oncogenic pathway activation is associated with the generation of an unfavorable tumor microenvironment, with consequent immunotherapy resistance. Therefore, an understanding of the immune evasive mechanism of HCC is urgently needed. Methods: Utilizing the antigen-expressing c-MycOE/Tp53KO HCC mouse model, a critical oncogenic signaling pathway in immune evasion was identified by data-independent acquisition mass spectrometry (DIA-MS) proteomics. Potential downstream pathways were investigated by scRNA-seq, immune profiling, western blot, and multiplexed immunofluorescence staining. We also examined the therapeutic potential of targeting wild-type Kras using the Kras inhibitor MRTX0902 and the MEK inhibitor trametinib to enhance the efficacy of immunotherapy in HCC. Results: We identified a significant upregulation of wild-type Kras in immune-escaped tumors, with concurrent activation of its ligand-driven EGFR and its downstream MEK/ERK signaling. Likewise, endogenous Kras overexpression in this model resulted in increased tumor burden with reduced survival time in mice, implicating the regulatory role of Kras signaling in immune evasion. Clinically, wild-type Kras showed elevated expression in HCC at both the mRNA and protein levels, and was associated with tumor recurrence and poorer patient survival. Through scRNA-seq analysis, we demonstrated that Kras hindered dendritic cell recruitment, leading to compromised Cd8+ T cell activity via the suppression of interferon-mediated Cxcl9. Wild-type Kras activation further impaired HCC recognition by T cells via the downregulation of MHC-I expression. Notably, the combination therapy of MRTX0902, trametinib, and anti-PD-1 effectively enhanced intratumoral Cd8+ T cell infiltration and demonstrated a favorable response in survival outcomes. Conclusion: This study showed that wild-type Kras, via the activation of its downstream MEK/ERK signaling, acts as a crucial immune evasive mechanism in HCC and contributes to resistance to anti-PD-1 therapy. It also provided new insights into the therapeutic potential of targeting wild-type Kras to enhance the efficacy of anti-PD-1 therapy, providing a foundation for further exploration and potential clinical applications in HCC. Citation Format: Mang Leng Lei, Terence Kin Wah Lee. Wild type Kirsten rat sarcoma (Kras) activation drives evasion of interferon-mediated immunity in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5356.