Han et al. observed that, relative to WT, casp1 knockout mice were resistant to tumor irradiation therapy. They examined individual components of this CASP1-dependent (IL-1-dependent) response to tumor irradiation by utilizing an array of gene- and cell type-specific knockout and Cre recombinase transgenic mice. Extracellular vesicular components of irradiated tumors activated the AIM2 inflammasome, and tumor supernatant induced IL-1 production through NLRP3. These two pathways coordinated in the production of IL-1, resulting in DC activation and cross-priming of intratumoral CD8+ T cells.
Contributed by Margot O’Toole
ABSTRACT: The inflammasome promotes inflammation-associated diseases, including cancer, and contributes to the radiation-induced tissue damage. However, the role of inflammasome in radiation-induced antitumor effects is unclear. We observed that tumors transplanted in Casp1-/- mice were resistant to radiation treatment compared with tumors in wild-type (WT) mice. To map out which molecule in the inflammasome pathway contributed to this resistant, we investigated the antitumor effect of radiation in several inflammasome-deficient mice. Tumors grown in either Aim2-/- or Nlrp3-/- mice remained sensitive to radiation, like WT mice, whereas Aim2-/-Nlrp3-/- mice showed radioresistance. Mechanistically, extracellular vesicles (EVs) and EV-free supernatant derived from irradiated tumors activated both Aim2 and Nlrp3 inflammasomes in macrophages, leading to the production of interleukin-1β (IL-1β). IL-1β treatment helped overcome the radioresistance of tumors growing in Casp1-/- and Aim2-/-Nlrp3-/- mice. IL-1 signaling in dendritic cells (DCs) promoted radiation-induced antitumor immunity by enhancing the cross-priming activity of DCs. Overall, we demonstrated that radiation-induced activation of the AIM2 and NLRP3 inflammasomes coordinate to induce some of the antitumor effects of radiation by triggering IL-1 signaling in DCs, leading to their activation and cross-priming.