Abstract 7023: ENPP1 inhibits the cGAS-STING pathway to mediate immune evasion in EGFR-TKI resistant NSCLC.

Abstract Third-generation EGFR tyrosine kinase inhibitors (TKIs), such as osimertinib, have demonstrated promising clinical efficacy in EGFR-mutant non-small cell lung cancer (NSCLC). Despite substantial progress with EGFR-TKIs, the development of acquired resistance remains a major clinical challenge. Notably, the addition of immunotherapy after TKI resistance has not resulted in significant survival benefits compared to chemotherapy. In this study, single-cell RNA sequencing analysis of key immune cell subpopulations and tumor immune features revealed an immunosuppressive shift in the tumor microenvironment of TKI-resistant tumors, characterized by an increased proportion of M2 macrophages, reduced dendritic cells (DCs) and M1 macrophages, and immune function scores indicative of an immunosuppressive state. Comprehensive transcriptomic profiling of established osimertinib-resistant NSCLC cell lines (HCC827OR, H1975OR, PC9OR) demonstrated a significant upregulation of ENPP1 expression compared with their parental, TKI-sensitive counterparts. Given that ENPP1 functions as a cGAMP hydrolase and is implicated in STING pathway suppression and immune evasion, we first assessed cGAMP hydrolysis activity and found that resistant cells exhibited enhanced cGAMP-degrading capacity. Co-culture experiments of tumor cells with antigen-presenting cells (APC) revealed that resistant tumor cells more effectively suppressed cGAS-STING signaling in APCs, thereby attenuating T-cell activation and cytotoxicity. Both genetic silencing of ENPP1 via siRNA and pharmacological inhibition using the ENPP1 inhibitor ENPP-1-IN-1 enhanced STING pathway activation in APCs and restored T-cell activation and cytotoxic functions in co-culture systems. Bioinformatic prediction and dual-luciferase assays identified SP1 as a direct transcriptional regulator of ENPP1. Finally, immune reconstitution mouse models confirmed that ENPP-1-IN-1 potentiated the efficacy of anti-PD-1 therapy in HCC827OR xenografts by increasing immune infiltration and T-cell activity. Collectively, our study highlights a critical role for ENPP1 in mediating immune evasion through suppression of the cGAMP-STING pathway in the EGFR-TKI resistant tumor, supporting ENPP1 as a promising therapeutic target to enhance immunotherapy efficacy in EGFR-TKI resistant NSCLC. Citation Format: Chao Zhou, Yuqing Liu, Jun Lu, Baohui Han. ENPP1 inhibits the cGAS-STING pathway to mediate immune evasion in EGFR-TKI resistant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7023.