More recently, epidemiologic studies have highlighted associations between the regular use of non-steroidal anti-inflammatory drugs (NSAID) and reduced glioma risks in humans and it has been shown that COX-2 pathway promotes gliomagenesis by directly supporting systemic development of myeloid derived suppressor cells (MDSCs) and their accumulation in the tumour microenvironment56. This evidence concerns the gene PTGS2 and glioma.