CXCL12 and glioblastoma: In contrast, glioblastoma tumour cells may be the main source of CCL2, CXCL10 and CXCL12 production in the tumour microenvironment given the elevated CCL2 detected in GNS cell culture supernatants and the minimal levels of CXCL10 and CXCL12 detected in dissociated tumour supernatants.