The network of immunosuppressive pathways in glioblastoma.

Glioblastoma remains a fatal tumor despite increased knowledge regarding the complex signalling pathways that drive this devastating disease. Recently, immunotherapeutic approaches have shown remarkable and durable responses in various cancers including metastatic melanoma and advanced non-small cell lung cancer. So far, it remains unclear whether these immunotherapeutics may also work against glioblastoma and other tumors residing in the central nervous system. It is well known that patients with glioblastoma suffer from profound local immunosuppression that represents the major hurdle to overcome in the context of immunotherapy. Several studies have demonstrated that this immunosuppressive phenotype is orchestrated by glioma-derived membrane-bound and soluble factors as well as the particular microenvironment within the brain. Here, we discuss the molecular and cellular pathways involved in glioblastoma-mediated inhibition of the immune system and highlight possible treatment approaches aiming at reinvigorating anti-tumor immune responses.