Immunity in malignant brain tumors - Tumor entities, role of immunotherapy, and specific contribution of myeloid cells to the brain tumor microenvironment.

Malignant brain tumors lack effective treatment, that can improve their poor overall survival achieved with standard of care. Advancement in different cancer treatments, has shifted the focus in brain tumor research and clinical trials towards immunotherapy-based approaches. The investigation of the immune cell landscape revealed a dominance of myeloid cells in tumor microenvironment. Their exact role und functions are subject of ongoing research. Current evidence suggests a complex interplay of tumor cells and myeloid cells with competing functions towards support vs. control of tumor growth. Here, we provide a brief overview on the three most abundant brain tumor entities: meningioma, glioma, and brain metastases. We also describe the field of ongoing immunotherapy trials and their results, including immune checkpoint inhibitors, vaccination studies, oncolytic viral therapy, and CAR-T cells. Finally, we summarize the phenotypes of microglia, monocyte-derived macrophages, border associated macrophages, neutrophils, and potential novel therapy targets. This article is protected by copyright. All rights reserved.