MMP9 and glioblastoma: The multidimensional mechanisms by which myeloid cells promote GBM angiogenesis include: direct secretion of proangiogenic factors (e.g., VEGF, IL-8); extracellular matrix (ECM) remodelling (via proteases such as MMP-9); hypoxia-driven signalling pathways (HIF-1α-LGMN axis); paracrine loops (IL-1β/IL-1R1); and indirect support for VM formation (via regulation of CSCs and EMT).