B7-H3 is actively being explored as an immunotherapy target for pediatric patients with solid tumors using monoclonal antibodies or T cells expressing chimeric antigen receptors (CARs). B7-H3-CARs containing a 41BB costimulatory domain are currently favored by several groups based on preclinical studies. In this study, we initially performed a detailed analysis of T cells expressing B7-H3-CARs with different hinge/transmembrane (CD8_ versus CD28) and CD28 or 41BB costimulatory domains (CD8_/CD28, CD8_/41BB, CD28/CD28, CD28/41BB). Only subtle differences in effector function were observed between CAR T cell populations in vitro. However, CD8_/CD28-CAR T cells consistently outperformed other CAR T cell populations in three animal models, resulting in a significant survival advantage. We next explored whether adding 41BB signaling to CD8_/CD28-CAR T cells would further enhance effector function. Surprisingly, incorporating 41BB signaling into the CAR endodomain had detrimental effects, while expressing 41BBL on the surface of CD8_/CD28-CAR T cells enhanced their ability to kill tumor cells in repeat stimulation assays. Furthermore, 41BBL expression enhanced CD8_/CD28-CAR T cell expansion in vivo and improved antitumor activity in one of four evaluated models. Thus, our study highlights the intricate interplay between CAR hinge/transmembrane and costimulatory domains. Based on our study, we selected CD8_/CD28-CAR T cells expressing 41BBL for early phase clinical testing.
Author Info: (1) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (2) Department of Bone Marrow Transplantation and
Author Info: (1) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (2) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (3) Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (4) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (5) Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (6) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (7) Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (8) Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (9) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (10) Experimental Cellular Therapeutics Laboratory, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (11) Vector Development and Production Laboratory, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (12) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (13) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. (14) Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
