Abstract 1573: Thermal trapping of MMC7 induces G2/M arrest, autophagy, and cGAS-STING signaling to augment anti-PD-1 efficacy

Abstract Background: Overcoming resistance to immune checkpoint blockade, such as anti-PD-1 therapy, remains a critical challenge in oncology. This study investigates the potential of mild hyperthermia to modulate tumor cell biology and enhance immunotherapy efficacy. Methods: Human tumor cell lines were subjected to mild hyperthermia (42°C) for 4 hours. Chromatin binding of MMC7 was assessed by chromatin fractionation and immunofluorescence. Cell cycle distribution was analyzed by flow cytometry. Autophagy induction was evaluated using LC3B-II conversion and autophagosome formation assays. Activation of the cGAS-STING pathway was measured via phosphorylation of STING and TBK1, and interferon-stimulated gene (ISG) expression. In vivo efficacy was validated using syngeneic mouse tumor models treated with hyperthermia (localized 42°C for 4 hours) combined with anti-PD-1 antibody. Results: Sustained mild hyperthermia (42°C for 4 hours) specifically inhibited the dissociation of MMC7 from chromosomes, resulting in prolonged G2/M phase arrest in tumor cells. This arrest triggered significant induction of autophagy and robust activation of the cGAS-STING innate immune signaling pathway, characterized by increased cGAS activity, STING/TBK1 phosphorylation, and downstream ISG expression. Critically, this hyperthermia-induced immunogenic state synergistically enhanced the anti-tumor efficacy of PD-1 blockade therapy. Mouse tumor models recapitulated these findings, demonstrating significantly improved tumor control and survival in cohorts receiving the combination of localized hyperthermia and anti-PD-1 compared to either treatment alone. Conclusion: Our findings demonstrate that controlled mild hyperthermia (42°C, 4h) induces persistent MMC7-chromatin binding, leading to G2/M arrest, autophagic activation, and potent stimulation of the cGAS-STING pathway within tumor cells. This creates a favorable tumor microenvironment that overcomes resistance and synergistically enhances the effectiveness of PD-1 checkpoint blockade immunotherapy. This combination strategy presents a promising novel approach for improving cancer treatment outcomes. Citation Format: Shan Li, Xiaofeng Ding, Zhilian Zhou, Huanlin Zhang, Tingting Lin, Lifeng Zhu, Yingming Sun, . Thermal trapping of MMC7 induces G2/M arrest, autophagy, and cGAS-STING signaling to augment anti-PD-1 efficacy [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 1573.