Chronic inflammation drives glioma growth: cellular and molecular factors responsible for an immunosuppressive microenvironment

This review examines glioma disease initiation, promotion, and progression with a focus on the cell types present within the tumor mass and the molecules responsible for the immunosuppressive microenvironment that are present at each step of the disease. The cell types and molecules present also correlate with the grade of malignancy. An overall "type 2" chronic inflammatory microenvironment develops that facilitates glioma promotion and contributes to the neo-vascularization characteristic of gliomas. An immunosuppressive microenvironment shields the tumor mass from clearance by the patient′s own immune system. Here, we provide suggestions to deal with a chronically-inflamed tumor microenvironment and provide recommendations to help optimize adjuvant immune- and gene therapies currently offered to glioma patients.