Coexpression Of Il7 And Ccl21 Increases Efficacy Of Car-T Cells In Solid Tumors Without Requiring Preconditioned Lymphodepletion

Purpose: T-cell recruitment, survival, and proliferation are the important limitations to chimeric antigen receptor (CAR) T cells therapy in the treatment of solid tumors. In this study, we engineered CAR-T cells to coexpress cytokines IL7 and CCL21 (7 x 21 CAR-T), a cytokine combination in order to improve proliferation and chemotaxis of CAR-T cells.Experimental Design: CLDN18.2-specific second-generation CAR-T cells coexpressing cytokines were prepared using retroviral vector transduction. The proliferation and migration of genetically engineered CAR-T cells were evaluated in vitro. The antitumor activities of genetically engineered CAR-T cells were evaluated against multiple solid tumors in C57BL/6 mice in vivo.Results: In vitro, the proliferation and chemotaxis of 7 x 21 CAR-T cells are significantly improved when compared with those of the conventional CAR-T cells. In vivo, 7 x 21 CAR-T cells revealed superior therapeutic effects to either conventional CAR-T cells or 7 x 19 CAR-T cells which coexpress IL7 and CCL19 as previously reported in three different solid tumors without cyclophosphamide precondition. Interestingly, 7 x 21 CAR-T cells could also suppress the tumor growth with heterogeneous antigen expression and even induce tumor complete remission. Mechanistically, IL7 and CCL21 significantly improved survival and infiltration of CAR-T cells and dendritic cells in tumor. In addition, CCL21 also inhibited the tumor angiogenesis as proved by IHC.Conclusions: Coexpression of IL7 and CCL21 could boost CAR-T cells' antitumor activity, and 7 x 21 CAR-T cells may be served as a promising therapy strategy for solid tumors.