CXCL12 and neoplasm: When resistance occurs, basic plasma levels of FGF and SDF1α were increased as were circulating endothelial cells, suggesting a microenvironmental role in promoting resistance and tumor recurrence.16 Although GBM is considered as immunologically “cold” tumors which do not respond to immune checkpoint inhibitors well, studies have suggested that anti-angiogenic therapy may change the tumor microenvironment into immunological favorable “hot” tumors.