MMP9 and central nervous system cancer: Factors released from glioma cells include extracellular matrix (ECM) components [9], such as versican [10] and tenascin-C (TNC) [11], factors released from TAMs include matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-9 (MMP9) and matrix metalloproteinase-14 (MMP14) 12–14 and the human specific CC motif chemokine ligand 18 (CCL18) [15].