Glioma–Immune Cell Crosstalk in Tumor Progression.

Simple Summary: The environment surrounding primary glioma brain tumors plays a critical role in tumor development and progression. Immune cells are important constituents of this tumor microenvironment. Classically, immune activation is thought to halt tumor progression; however, recent evidence has shown that glioma cells can interact with immune cells to convert them into tumor-supporting cells. These reprogrammed immune cells allow glioma cells to evade the anti-tumor effects of the immune system and can even promote tumor growth. Understanding the mechanisms that result in this altered immune tumor microenvironment may pave the way to new therapies for brain tumors. This review aims to provide an updated view of the mechanisms underlying glioma–immune cell interactions and novel therapies being developed to combat glioma immune evasion. Glioma progression is a complex process controlled by molecular factors that coordinate the crosstalk between tumor cells and components of the tumor microenvironment (TME). Among these, immune cells play a critical role in cancer survival and progression. The complex interplay between cancer cells and the immune TME influences the outcome of immunotherapy and other anti-cancer therapies. Here, we present an updated view of the pro- and anti-tumor activities of the main myeloid and lymphocyte cell populations in the glioma TME. We review the underlying mechanisms involved in crosstalk between cancer cells and immune cells that enable gliomas to evade the immune system and co-opt these cells for tumor growth. Lastly, we discuss the current and experimental therapeutic options being developed to revert the immunosuppressive activity of the glioma TME. Knowledge of the complex interplay that elapses between tumor and immune cells may help develop new combination treatments able to overcome tumor immune evasion mechanisms and enhance response to immunotherapies. [ABSTRACT FROM AUTHOR]