IMMU-17. TARGETING GLIOBLASTOMA WITH DNAM-1-BASED CHIMERIC ANTIGEN RECEPTOR (CAR) T CELLS

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.