MMP2 and glioblastoma: The activation of CX3CL1 (chemokine C-X3-C motif ligand 1, also known as fractalkine)/CX3CR1 (CX3C chemokine receptor 1) in tumor-associated microglia/macrophages (TAMs) increases the adhesion/migration capacity of GBM cells through the expression of MMP-2, -9, and -14 [63].