Radiotherapy in combination with PD-1 and TIGIT blockade mediate antitumor abscopal effects and immune memory via CD8+ T cells

Abstract

This study investigated the synergistic antitumor effects of radiotherapy combined with anti-PD-1 and anti-TIGIT antibodies (aPD-1/aTIGIT), focusing on primary and abscopal tumor control, immune mechanisms, and long-term immune memory. Using bilateral subcutaneous tumor models (LLC, CMT-167, B16-F10, MC38) in C57/BL6 mice, we demonstrated that triple therapy (radiotherapy + aPD-1 + aTIGIT) significantly enhanced tumor regression and systemic antitumor responses. Flow cytometry, multicolor immunofluorescence, and single-cell transcriptomics revealed that triple therapy amplified CD8⁺ T cell activation, reversed exhaustion, and increased tumor infiltration. M1 macrophages exhibited robust immune activation and enhanced interactions with CD8⁺ T cells, driven by upregulated NF-κB, STAT1, and chemokine pathways. Longitudinal Luminex cytokine profiling identified sustained increases in TNF-α, CXCL10, and CCL5 post-treatment, supporting macrophage-T cell crosstalk. Rechallenge experiments and adoptive CD8⁺ T cell transfers confirmed that triple therapy generated durable central memory CD8⁺ T cells, which mediated antigen-specific immune memory and prevented tumor recurrence. These findings establish CD8⁺ T cells as central mediators of abscopal effects and long-term immunity, highlighting the critical role of M1 macrophage polarization in amplifying therapeutic synergy. By elucidating the mechanisms underlying resistance to PD-1 monotherapy, this study provides a translatable strategy to enhance clinical outcomes through radiotherapy-immunotherapy combinations.