Abstract Background: Accumulated DNA double-strand breaks (DSBs), a key hallmark of cancer, are efficiently repaired during interphase to preserve proper mitotic progression, a process crucial for preventing genomic collapse. This protective strategy also represents a potential vulnerability for selectively eliminating tumor cells. However, when unrepaired DSBs persist into mitosis, the subsequent cellular fate and underlying mechanisms remain poorly understood. Using a cell model harboring under-repaired mitotic DSBs, we found that these mitotic DSBs robustly trigger NLRP3 mediated pyroptosis, an inflammatory form of cell death characterized by the release of inflammatory molecules, which has the potential to stimulate antitumor immunity within the tumor microenvironment. Mechanically, we identify 53BP1, an DNA repair associated protein, as a new regulator that drives mitotic pyroptosis. Methods and Results: Using flow cytometry, western blot and immunofluorescence co-localization, a cell model in which DSBs prematurely enter into mitosis was established. Leveraging live-cell imaging and the H2B-mCherry system, we observed that DSBs in mitosis induces pyroptosis mediated by NLRP3 inflammation activation, as evidenced by characteristic pyroptotic morphologies, ASC foci formation and GSDMD cleavage. To elucidate the underlying mechanism of NLRP3 activation during mitosis, we employed liquid chromatography-mass spectrometry (LC-MS) combined with a DNA damage response (DDR) gene library analysis. This approach identified p53-binding protein 1 (TP53BP1) as the most abundant and intriguing candidate for NLRP3 interaction and activation in mitosis, which was further validated by molecular cloning, co-immunoprecipitation assays, and immunofluorescence co-localization. Furthermore, validation experiments across multiple cell models demonstrated that the phosphorylated 53BP1 during mitosis promoted NLRP3 inflammation activation and induced pyroptosis. This effect was consistent with the pyroptotic phenotype observed in a mouse model harboring a phosphorylated 53BP1 knock-in mutation. Conclusion: Our work identifies 53BP1 as a novel NLRP3 regulator that activates NLRP3 inflammation during mitosis and induces pyroptosis, thereby revealing a new mechanism that compensates for the loss of NEK7-dependent NLRP3 activation during mitosis. This study provides an unprecedented insight into the crosstalk between the DNA damage response and the NLRP3 mediated pyroptosis, and offers a conceptual framework for the development of new therapeutic strategies. Citation Format: Mengshi Luo, Yuewen Zhang, Wenjian Gong, Zhiqi Liao, Linghui Wang, Qiuyang Xu, Xingzhe Liu, Yijie Wu, Xuejiao Zhao, Gorden B. Mills, Ding Ma, Guangnian Zhao, Qinglei Gao, Yong Fang. Mitotic entry with DSB induces pyroptosis through 53BP1-mediated NLRP3 inflammasome activation 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 5671.
Luo et al. (Fri,) studied this question.