CAR T Cells Releasing IL-18 Convert to T-Bethigh FoxO1low Effectors that Exhibit Augmented Activity against Advanced Solid Tumors

Adoptive therapy with chimeric antigen receptor (CAR)-redirected T cells has achieved remarkable efficacy in the treatment of hematopoietic malignancies. However, eradicating large solid tumors in advanced stages of the disease remains challenging. We explored augmentation of the anti-tumor immune reaction by establishing an acute inflammatory reaction. Systematic screening indicates that IL-18 polarizes CAR T cells toward T-bet^high FoxO1^low effectors with an acute inflammatory response. CAR T cells engineered with inducible IL-18 release exhibited superior activity against large pancreatic and lung tumors that were refractory to CAR T cells without cytokines. IL-18 CAR T cell treatment was accompanied by an overall change in the immune cell landscape associated with the tumor. More specifically, CD206^- M1 macrophages and NKG2D⁺ NK cells increased in number, whereas Tregs, suppressive CD103⁺ DCs, and M2 macrophages decreased, suggesting that "iIL18 TRUCKs" can be used to sensitize large solid tumor lesions for successful immune destruction.