Abstract PS4-02-12: Combination of CDK4/6 and EZH2 Inhibitors Enhances Anti-Tumor Immunity in Triple-Negative Breast Cancer via the MAVS-TBK1-STAT1 Signaling Pathway and Synergizes with Anti-PD-1 Therapy

Abstract Background and Purpose: Although immune checkpoint inhibitors (ICIs) combined with chemotherapy have been established as the standard treatment regimen for triple-negative breast cancer (TNBC), the proportion of patients deriving significant clinical benefit remains limited. Identifying novel therapeutic targets and developing synergistic strategies to enhance the efficacy and broaden the applicability of ICIs represent critical areas of ongoing research. Methods: A series of comprehensive experiments, including 4T1 orthotopic breast cancer mouse models, tumor-T cell co-culture systems, transcriptome sequencing, flow cytometry, immunoblotting, and qPCR, were performed to systematically elucidate the anti-tumor immune mechanisms of the drug combination. Results: The combination of CDK4/6 and EZH2 inhibitors significantly inhibited 4T1 orthotopic tumor growth and promoted CD8+ T cell infiltration. Transcriptomic analysis identified differential gene enrichment in pathways related to cell adhesion and migration. qPCR demonstrated a notable upregulation of chemokine mRNAs (e.g., CXCL9, CXCL10, CXCL11) in the combination treatment group, while in vitro migration assays confirmed enhanced recruitment of CD8+ T cells. Mechanistically, the combination therapy activated the MAVS-TBK1 axis via dsRNA signaling (but not dsDNA) signaling, leading to STAT1 phosphorylation and increased IFN-β secretion, which subsequently upregulated chemokine expression (no such effects were observed with H151, a STING pathway inhibitor). Furthermore, the combination therapy synergistically enhanced the efficacy of anti-PD-1 monoclonal antibodies. Conclusion: This study demonstrates that the combination of CDK4/6 and EZH2 inhibitors induces chemokine expression and facilitates CD8+ T cell infiltration via the MAVS-TBK1-STAT1 axis, thereby enhancing anti-tumor immunity and providing a novel synergistic approach for TNBC immunotherapy. Citation Format: S. Li, Z. Ningning, S. Qing, W. Guanwen, Q. Fanli, W. Long, Q. Yang, Z. Xiaohua. Combination of CDK4/6 and EZH2 Inhibitors Enhances Anti-Tumor Immunity in Triple-Negative Breast Cancer via the MAVS-TBK1-STAT1 Signaling Pathway and Synergizes with Anti-PD-1 Therapy abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-02-12.