Chimeric antigen receptor (CAR)-T cell therapy for solid tumors has garnered significant attention, as evidence by the increasing number of related studies. However, most studies rely on xenograft mouse models, which do not fully capture the complexity of immune interactions in vivo. To address this, we employed immunocompetent mice to compare the efficacy and functional characteristics of 28z and BBz CAR-T cells in a syngeneic B16F10 melanoma model expressing human CD19.
CAR-T cells were administered to tumor-bearing immunocompetent mice, and their pharmacokinetics/pharmacodynamics (PK/PD) were assessed using flow cytometry, IVIS imaging, and Luminex assays. Effector function and therapeutic efficacy were further evaluated in vitro and ex vivo.
BBz CAR-T cells exhibited greater initial tumor infiltration, as evidenced by higher luciferase activity in tumors on day 5 post-infusion. In contrast, 28z CAR-T cells showed superior persistence in both tumor and lymphoid tissues. In peripheral blood, both CAR-T cell types peaked on day 7 and declined thereafter; however, 28z CAR-T cells exhibited enhanced persistence and a predominance of the effector memory phenotype. Circulating cytokine and chemokine levels varied depending on the co-stimulatory domain. In vitro assays revealed that BBz CAR-T cells proliferated more rapidly but also had a higher rate of apoptosis compared to 28z CAR-T cells.
In conclusion, 28z and BBz CAR-T cells demonstrate distinct functional profiles in the syngeneic B16F10 melanoma model. While BBz CAR-T cells offer rapid early tumor infiltration and proliferation, 28z CAR-T cells exhibit greater persistence, sustained effector function, and overall antitumor efficacy. Understanding these differences in immunocompetent models could inform the design of more effective CAR-T cell therapies for solid tumors.