EPEN-33. STUDY OF ANTI-HER2 CAR T CELLS IN THE IMMUNOSUPPRESSIVE EPENDYMOMA TUMOR MICROENVIRONMENT

Abstract

Ependymoma (EPN) is a brain tumor that is chemotherapy insensitive. Surgery can remove grossly visible tumor in most EPN cases but, even when combined with radiation, there is a 10-year relapse rate of over 70%. Chimeric antigen receptor (CAR) T cell therapy has been very effective in the clinic treating patients with hematologic malignancies, but progress in solid tumors has lagged. Microarray analysis of pediatric EPN samples revealed HER2 as an important target. A second-generation anti-HER2 CAR-T cell containing the CD3-zeta and 4-1BB signaling motifs will be studied against two patient derived, high-risk EPN cell lines (811 and 928). Co-culture assays will be performed to determine specific cytokine release indicative of CAR-T cell activation upon antigen recognition. Cytolytic assays to determine EPN cell killing by CAR-T cells will be done using continuous monitoring through the IncuCyte allowing for direct evaluation of both cytotoxicity and localization of CAR-T cells to tumor cells. An orthotopic intraventricular xenograft model will be employed to validate these findings. Finally, experiments to determine the effect of the immunosuppressive EPN tumor environment on CAR-T cells will be performed. HER2 CAR-T cells secreted increased cytokine levels (IFN-γ, IL-2, TNFα) in the presence of 811 and 928 tumor cells compared to control T cells. HER2-BBz-CAR T cells demonstrated significant killing of 928 and 811 (p<0.0001), even at low E:T ratios. HER2 CAR-T cells demonstrate antigen recognition of EPN cell lines and confers specific killing activity against HER2-positive EPN cell lines. Further studies are ongoing.