Bcl-2 Enhances Chimeric Antigen Receptor T Cell Persistence by Reducing Activation-Induced Apoptosis

SIMPLE SUMMARY: Chimeric antigen receptor-modified T cells (CAR-T) have shown great success in the treatment of B-cell leukemia. However, their efficacy is compromised in B-cell-derived lymphoma and solid tumors. Optimization of CAR design to improve in vivo persistence is a focus of current CAR-T cell research. The aim of our study is to access the potential added value of integration of anti-apoptotic molecules for enhancing anti-tumor activity of CAR-T cells. We confirmed that integrating B cell lymphoma-2 (Bcl-2) into CAR-T cells improved the proliferation ability of CAR-T cells in vitro and in vivo, which led to enhanced anti-tumor activity and prolonged survival in a mouse xenograft lymphoma model. This work provides proof of concept evidence for a new strategy to optimize the function of CAR-T cells against lymphoma. ABSTRACT: Purpose: To evaluate the potential added value of integrating anti-apoptotic molecules for improving the anti-tumor activity of CAR-T cells. Methods: Four small molecules inhibiting apoptosis were tested for their ability to prevent activated induced CAR-T cell death. Five CD20-targeting, CD137 (4-1BB) and CD3ζ integrated CAR-T cells (20BBZ) with constitutively expressed anti-apoptotic genes were established, and we screened out the strongest proliferation enhancer: Bcl-2. The memory subtype and the exhaustion markers of CAR-T cells were analyzed. The anti-tumor activities of Bcl-2 integrating CAR-T cells (20BBZ-Bcl-2) were evaluated in vitro and in a mouse xenograft lymphoma model. Conclusion: The 20BBZ-Bcl-2 CAR-T cells showed improved proliferation ability compared to 20BBZ CAR-T cells in vitro. In addition, activation-induced apoptosis was reduced in the 20BBZ-Bcl-2 CAR-T cells. Consistent with the enhanced proliferation in vitro, 20BBZ-Bcl-2 CAR-T cells exhibited improved anti-tumor activity in a mouse xenograft lymphoma model.