Year: 2016
Type: article
Abstract: BACKGROUND: Glioblastoma (GBM) is the most aggressive primary brain tumor in humans, and is virtually incurable with conventional therapies. Immunotherapy with T cells expressing chimeric antigen receptors (CARs) specific for the GBM antigen IL13Rα2 is an attractive approach to improve outcomes. We recently generated the first scFv-based CAR that is specific for IL13Rα2 and demonstrated that IL13Rα2-CARs with a CD28.ζ endodomain had potent anti-GBM activity in preclinical models. However, CAR T-cell persistence was limited, resulting in recurrence of IL13Rα2-positive GBMs. Since IL13Rα2-CARs with other endodomains (41BB, 41BB and OX40) did not improve outcomes, the goal of this project was to evaluate if transgenic expression of IL-15, a cytokine that is critical for T-cell proliferation and survival, enhances persistence and anti-tumor activity of IL13Rα2-CAR.CD28.ζ T cells. METHODS: We generated IL13Rα2-CAR.CD28.ζ T cells expressing IL-15 (IL13Rα2-CAR. IL15 T cells) by double transducing T cells with retroviruses containing expression cassettes encoding i) IL13Rα2-CAR.CD28.ζ or ii) IL-15, ΔNGFR, and iC9 separated by 2A sequences. We determined the effector function of IL13Rα2-CAR. IL15 T cells in vitro using standard assays, and in the U373 GBM xenograft model. RESULTS: Double transduction of CD3/CD28-activated T cells resulted in T-cell lines that expressed both transgenes in 45-50% of T cells. At base line IL13Rα2-CAR. IL15 T cells produced on average 69.5 pg/ml of IL15. Production was significantly increased after CD3 or antigen-specific T-cell stimulation (176.7 pg/ml; n=6; p<0.001). IL13Rα2-CAR. IL15 T cells were as efficient as IL13Rα2-CAR T cells in killing IL13Rα2-positive GBMs in vitro. After intratumoral injection into U373 glioma-bearing mice IL13Rα2-CAR. IL15 T cells persisted significantly longer than IL13Rα2-CAR T cells (p<0.05). This resulted in a significant increase in progression free (98 vs 49 days; p=0.004) and overall survival (p=0.006) of treated mice. Up to date, 4/10 IL13Rα2-CAR. IL15 T-cell treated mice remain glioma free with a follow up of at least 80 days. Recurring U373 gliomas post IL13Rα2-CAR. IL15 T-cell therapy had down regulated IL13Rα2 expression, indicating immune escape. This was specific for the targeted antigen since LL13Rα2-CAR.LL15 T-cell-treated U373 gliomas continued to express other tumor antigens such as EphA2 and HER2 at unchanged levels in comparison to controls. CONCLUSION: Here we demonstrate that transgenic expression of IL15 enhances the in vivo persistence of IL13Rα2-CAR T cells resulting in improved anti-glioma activity. However, enhanced in vivo persistence of T cells also resulted in the development of antigen-loss variants highlighting the need to target multiple antigens in tumors with heterogeneous antigen expression such as GBM.
Source: Molecular Therapy
Language: English
Topic: CAR-T cell therapy research
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W2567190127