Cancer Immunoediting in Gliomas: Recent Advances and Implications for Immunotherapy

Gliomas are an aggressive class of primary brain tumors with high rates of recurrence and a dismal overall survival [1]. While existing therapeutic strategies provide some benefit, their effects are variable, and no curative modalities exist. The poor prognosis of these patients largely stems from the heterogenous molecular profile of these tumors and their tumor immune microenvironment (TIME) [2,3]. In addition to tumor expression of PD-L1, glioma cells release immunosuppressive cytokines and chemokines, like IL-10, TGF-β, and PGE2 in the intercellular tumor milieu, which have been shown to reduce antigen presenting activity and downregulate the proliferation of natural killer (NK) and CD8+ cytotoxic T-cells [4-7]. These tumor-derived factors facilitate the increased presence of immunosuppressive cell populations like myeloidderived suppressor cells (MDSC), tumor-associated macrophages (TAM), and regulatory T-cells (Tregs), which synergistically contribute to immune evasion and poor response to immunotherapies [4,8,9].