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Purpose: Most chimeric antigen receptor (CAR) T-cell strategies against glioblastoma have demonstrated only modest therapeutic activity and are based on persistent gene modification strategies that have limited transgene capacity, long manufacturing processes, and the risk for uncontrollable off-tumor toxicities. mRNA-based T-cell modifications are an emerging safe, rapid, and cost-effective alternative to overcome these challenges, but are underexplored against glioblastoma. Experimental Design: We generated mouse and human mRNA-based multifunctional T cells coexpressing a multitargeting CAR based on the natural killer group 2D (NKG2D) receptor and the proinflammatory cytokines IL12 and IFNα2 and assessed their antiglioma activity in vitro and in vivo. Results: Compared with T cells that either expressed the CAR or cytokines alone, multifunctional CAR T cells demonstrated increased antiglioma activity in vitro and in vivo in three orthotopic immunocompetent mouse glioma models without signs of toxicity. Mechanistically, the coexpression of IL12 and IFNα2 in addition to the CAR promoted a proinflammatory tumor microenvironment and reduced T-cell exhaustion as demonstrated by ex vivo immune phenotyping, cytokine profiling, and RNA sequencing. The translational potential was demonstrated by image-based single-cell analyses of mRNA-modified T cells in patient glioblastoma samples with a complex cellular microenvironment. This revealed strong antiglioma activity of human mRNA-based multifunctional NKG2D CAR T cells coexpressing IL12 and IFNα2 whereas T cells that expressed either the CAR or cytokines alone did not demonstrate comparable antiglioma activity. Conclusions: These data provide a robust rationale for future clinical studies with mRNA-based multifunctional CAR T cells to treat malignant brain tumors.

BACKGROUND Genetically engineered T cells that express a chimeric antigen receptor (CAR) have shown powerful anti-tumor activity in extracranial malignancies. This concept is now also being explored against glioblastoma. However, many single target antigens used for CAR cell therapy are non-homogeneously expressed. We assessed the therapeutic potential of CAR T cells targeting 2 antigens which are homogeneously expressed by glioma cells which reduces the probability of tumor immune escape due to antigen loss. METHODS We analyzed the expression of CD112 and CD155, which are ligands to the activating immune cell receptor DNAX Accessory Molecule-1 (DNAM-1), in a panel of mouse and human glioma cell lines as well as in human glioblastoma samples and generated glioma cells with a CD112 or CD155 knock-out. To exploit the specific binding properties of DNAM-1, we generated first or second-generation CAR T cells that use DNAM-1 as an antigen-binding domain and investigated their anti-tumor activity in vitro and in vivo using syngeneic orthotopic mouse glioma models. RESULTS CD112 and CD155 are homogeneously expressed in mouse and human glioma cell lines as well as human glioblastoma tissue specimens. CRISPR/Cas9-mediated knock-out of CD112 or CD155 affected the migration of glioma cells, but had no impact on the proliferation or susceptibility to irradiation or temozolomide. DNAM-1-based CAR T cells exerted high cytolytic activity and secretion of various effector cytokines in vitro. Upon intravenous administration, DNAM-1-based CAR T cells did not exert significant toxicity, homed to the tumor site in the brain and prolonged the survival of orthotopic glioma-bearing mice with durable anti-tumor responses in a fraction of mice. CONCLUSION CD112 and CD155 represent attractive targets for glioma immunotherapy using genetically engineered immune cells. Based on the data obtained from our preclincal assessment of DNAM-1-based CAR T cells, this immunotherapeutic strategy might also be explored in human glioma patients.

BACKGROUND Cancer immunotherapy with genetically engineered T cells that express a chimeric antigen receptor (CAR) has led to impressive responses in extracranial malignancies and is also explored against glioblastoma. However, CAR T cell strategies that are currently being explored against glioblastoma target single tumor antigens, which are non-homogeneously expressed and are prone to antigen escape. Furthermore, the immunosuppressive brain tumor microenvironment hampers anti-tumor efficacy. METHODS By immunohistochemistry and flow cytometry, we investigated the expression of CD155 and CD112, which are ligands to the activating immune cell receptor DNAX accessory molecule-1 (DNAM-1), in human and mouse glioma cell lines as well as in human glioblastoma samples. To understand their functional role, we generated CD155 or CD112 knock-out glioma cell lines using CRISPR/Cas9 and studied proliferation, sensitivity to irradiation or temozolomide as well as migration. To exploit the promiscuous binding features of DNAM-1, we generated different first or second-generation CAR T cells that use DNAM-1 as a tumor-binding domain. Subsequently, we investigated their anti-tumor activity in vitro in co-culture assays and in vivo in syngeneic orthotopic murine glioma models. RESULTS CD155 and CD112 are homogenously expressed in human and mouse glioma cell lines and human glioblastoma tissues. Knock-out of these ligands affected the migration of tumor cells, but did not affect proliferation or sensitivity to irradition or temozolomide. DNAM-1-based CAR T cells demonstrated high cytolytic activity and effector cytokine secretion in vitro. In vivo, DNAM-1 based CAR T cells reached to the tumor site in the brain upon intravenous administration, prolonged survival of orthotopic glioma-bearing mice and led to a durable anti-tumor response in a fraction of mice. The treatment was tolerated without toxicities. CONCLUSION We elucidated the tumor-intrinisic role of CD155 and CD112 and provide the first systematical preclincal assessment of DNAM-1 CAR T cells against glioma. These findings provide a rationale to test this immunotherapeutic strategy also in human glioma patients.