CXCR4 and glioblastoma: Indeed, when we looked at the gene expression levels of GNG4 and CXCR4 in different GBM subtypes, GNG4 was most down regulated and CXCR4 was most up regulated in mesenchymal subtype of GBM which is characterized by more malignant and invasive phenotype as compared to classical, neural and proneural [30, 31].