P08.19.A IMMUNE MODULATION AND SURVIVAL BENEFIT OF ICAM-1 CAR T-CELLS IN PRECLINICAL GLIOMA MODELS

Abstract BACKGROUND Glioblastoma is the most fatal primary brain tumor in adults, with poor prognosis despite aggressive therapy. Existing therapeutic options remain limited, highlighting the need for innovative treatment approaches. Chimeric antigen receptor (CAR) T-cell therapy offers a promising strategy in which T cells are genetically engineered to express synthetic receptors that specifically recognize surface antigens on tumor cells. However, its success in glioblastoma has been limited due to challenges such as antigen heterogeneity, immune evasion through antigen loss, restricted CAR T-cell infiltration, and poor persistence within the hostile tumor microenvironment (TME). Given these limitations, researchers have turned their attention to alternative targets with broader expression profiles. One such candidate is intercellular adhesion molecule-1 (ICAM-1), which is upregulated not only on glioblastoma cells but also on tumor-associated immune and endothelial cells, thereby offering the potential to attack the tumor from multiple angles. MATERIAL AND METHODS ICAM-1 expression was analyzed using tissue microarrays from human glioblastoma and normal brain specimens. Healthy human donor T-cells or murine splenocytes were used to generate second-generation CAR T-cells through lentiviral and retroviral transduction. Their cytotoxic potential was assessed in vitro using co-culture assays with glioma and endothelial cell lines. Therapeutic efficacy was evaluated in vivo in both syngeneic and xenograft glioma mouse models. Furthermore, ex vivo tumor analyses using high-dimensional flow cytometry and immunohistochemistry provided insights into changes within the TME. RESULTS ICAM-1 was significantly upregulated in human glioblastoma compared to normal brain tissue with particularly elevated levels in recurrent tumors. Single-cell RNA sequencing and immunohistochemistry confirmed ICAM-1 expression across glioma cells, tumor-associated immune cells, and endothelial cells. Functionally, ICAM-1-directed CAR T-cells demonstrated robust and antigen-specific cytotoxic activity in vitro. In vivo, intratumoral CAR T-cell administration significantly prolonged survival in both syngeneic and xenograft glioma mouse models. Ex vivo analysis revealed increased infiltration of B- and T-cells, a reduction in monocyte-derived macrophages, and a decrease in tumor vascularization, indicating CAR T-cell-mediated remodeling of the TME. CONCLUSION These findings show the therapeutic benefits of ICAM-1 targeting CAR T-cells in both human and murine glioma models. Moreover, the detection of treatment-induced alterations within the TME provides valuable insights, highlighting the potential of CAR T-cells to not only target tumor cells but also modulate bystander cells to create a more tumor-suppressive environment.