2464 - The Role of Tumor-Intrinsic Interferon Signaling and Associated Microenvironmental Remodeling in Solid Tumor CAR T-Cell Therapy Response
Presenter(s)
S. Gholamin1, S. S. Gholamin1, Y. Zhao1, S. Xu1, M. Aftabizadeh1, B. Comin-Anduix2, C. Masia1, R. A. Wong1, B. Aguilar3, R. Starr1, D. Y. Torrejon2, D. Alizadeh3, X. Wu1, A. Kalbasi4, A. Ribas2, S. J. Forman5, and C. Brown3; 1City of Hope, Duarte, CA, 2UCLA, Los Angeles, CA, 3City of Hope National Medical Center, Duarte, CA, 4Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, 5Department of Hematology and Hematopoietic Cell Transplantation, City of Hope National Medical Center, Duarte, CA
Purpose/Objective(s): Despite rapidly expanding CAR T cell trials in solid tumors, efficacy remains limited across diverse tumor types. Previous studies revealed that solid tumors with interferon (IFN) signaling loss demonstrate resistance to CAR T therapy, in part through reduced IFN?-induced cell-adhesion programs. However, how IFN signaling deficiency enforces resistance via remodeling of the tumor microenvironment (TME) is not fully elucidated.
Materials/Methods: Here, we established YUMM melanoma wild-type (WT) and JAK1 knockout (JAK1/KO; type I/II IFN signaling–deficient) mouse tumors expressing IL13Ra2. These cells were treated with murine IL13 (mIL13) CAR T cells in vitro and in vivo. In vitro cytotoxicity assays were performed at 24, 48, and 72 hours, and the quantity of killed cells was assessed by flow cytometry. Bulk RNA-seq was performed on WT versus JAK1/KO tumor cells exposed to CAR T–conditioned media (media from CAR T cells co-cultured with WT tumor cells) at the time points described above. Tumor cells were inoculated into the flanks of C57BL/6 mice and randomized to receive mIL13 CAR T cell treatment or control. Tumors were measured with calipers post-treatment in each group.
Results: In vitro studies revealed comparable killing of WT and JAK1/KO YUMM tumors exposed to mIL13 CAR T cells at different time points. We next compared transcriptional mediators downstream of IFN effector signaling in both tumor types exposed to CAR T cell–conditioned media, identifying ISG15 as one of the top differentially expressed genes. In vivo experiments revealed that JAK1/KO tumors demonstrated resistance to mIL13 CAR T cells compared with WT counterparts. Single-cell RNA-seq and CyTOF analyses of in vivo tumors pre- and post-mIL13 CAR T cell therapy demonstrated that JAK1/KO tumors maintained an immunosuppressive niche after therapy, with reduced activated/naïve T cells and increased exhausted/regulatory T cells, suppressive myeloid populations, and heterogeneous suppressive fibroblasts. Unconjugated ISG15 combined with mIL13 CAR T cell therapy significantly reduced tumor size compared with either monotherapy.
Conclusion: Tumor IFN signaling loss drives CAR T resistance largely through establishment of an immunosuppressive TME rather than loss of intrinsic susceptibility in YUMM JAK1/KO model compared to WT. Combination of unconjugated ISG15 with mIL13 CAR T cell therapy significantly reversed the resistance of YUMM JAK1/KO tumors and supports a rational combination strategy for IFN-deficient solid tumors.