XCL1 and glioblastoma: Secondly, GBM cells usually recruit regulatory T cell (Treg cell) into GBM tissue by secreting chemokines such as colony stimulating factor 1 (CSF1), C-X-C Motif Chemokine Ligand 12 (CXCL12), C-X-C Motif Chemokine Ligand 1 (CXCL1) and granulocyte–macrophage colony stimulating factor (GM-CSF) [11].