Inflammasome Activation Limits Radiotherapy-Induced Antitumor Immunity and Shapes CD8+ Responses in a Sex-Dependent Manner 2260523

Abstract Introduction Radiation therapy (RT) induces immunogenic cell death and antitumor immunity. We demonstrated that myeloid MyD88 signaling restricts CD8+ T cell responses after RT and hypothesized that inflammasome activation downstream of MyD88 contributed to this phenotype. Methods We cocultured bone marrow—derived macrophages and PK5L1940 pancreatic tumor cells in the presence of specific inhibitors to assess the mechanism of inflammasome activation following RT. WT or ASC-mCitrine reporter mice bearing subcutaneous tumors were treated with RT and the caspase-1 inhibitor VX765, with immune profiling and inflammasome activity assessed by flow cytometry. Results RT activated the NLRP3 inflammasome in macrophages dependent on ER Ca2+ release, and mitochondrial ROS. VX765 improved post-RT survival in a CD8+ T cell—dependent manner, with efficacy observed in males. VX765 enhanced the expansion of T-bet+Eomes+Ki67+ CD8+ effector cells and increased tumor antigen—specific T cells. RT also induced IL-23 expression and Th17 response, while VX765 further upregulated IL-23R expression on CD4+ T cells. In females, estrogen and progesterone suppressed inflammasome activation, and VX765 efficacy required hormonal blockade. Conclusion NLRP3 inflammasome activation limits RT-induced antitumor immunity by restricting CD8+ responses. VX765 enhances effector CD8+ T cell expansion and survival in males post-RT. Sex hormones modulate inflammasome activity, impacting efficacy of its blockade in combination with RT. Funding Source Collins Medical Trust K22 CA251643 Providence Foundation Topic Categories Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)