Purpose: To compare antitumor effector function mediated by CD4+ and CD8+ chimeric antigen receptor (CAR)-T cells targeting IL13 receptor α2 (IL13Rα2) for treatment of glioblastoma (GBM).
Experimental Design: CD4+ and CD8+ IL13Rα2-specific CAR-T cells, derived from enriched central memory T cells (Tcm), were evaluated for their antitumor potential both in vitro by recursive challenge with GBM cells and in vivo in established orthotopic GBM xenograft models. Further, GBM-stimulated CD4+ and CD8+ CAR-T cells were examined for their exhaustion- and memory-associated phenotypes at transcriptional and protein levels, which would account for their differential antitumor activity.
Results: While CD8+ CAR-T cells mediated robust short-term cytolytic effector function, they became rapidly exhausted and lost antitumor potential after repeated stimulation with tumor cells. CD4+ CAR-T cells, by contrast, persisted and retained effector potency even after repetitive tumor challenge. CD4-mediated cytotoxicity acted through the granzyme B/perforin pathway and was independent of the CD8+ cells. Activated CD4+ CAR-T cells augmented the proliferation of CD8+ cells, but failed to protect the CD8+ cells against stimulation-induced exhaustion. In NSG mice bearing GBM xenografts, CD4+ CAR-T cell treatment led to long-term tumor-free survival, while CD8+ CAR-T cell treated mice showed short-term tumor regression followed by antigen-positive relapse and associated T cell exhaustion. Upon GBM stimulation, CD4+ cells expressed less co-inhibitory receptors and more memory-associated markers than the CD8+ T cell subset. Further, a comprehensive transcriptional analysis revealed that when activated, CD4+ cells retained expression of genes involved in survival- and self-renewal-related pathways, indicating a less exhausted status and a better functional persistence in comparison to the CD8+ cells.
Conclusion: We observed a superior anti-GBM activity mediated by CD4+ CAR-T cells over the CD8+ subset, featured by their ability to maintain long-term immune response and reduce stimulation-induced exhaustion. It is thus inferred that the frequency of CD4+ cells could be an important criteria for evaluating the efficacy of CAR-T cells as immunotherapeutic products.
Citation Format: Dongrui Wang, Renate Starr, Brenda Aguilar, Alfonso Brito, Brenda Chang, Aniee Sarkissian, Behnam Badie, Michael E. Barish, Stephen J. Forman, Christine E. Brown. CD4+ outperform CD8+ central memory-derived CAR T cells, mediating persistent antitumor responses and long-term eradication of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3024. doi:10.1158/1538-7445.AM2017-3024