Microglia/macrophages secrete multiple cytokines, growth factors, enzymes, and reactive oxygen species that can directly or indirectly lead to angiogenesis (e.g., VEGF), tumor proliferation (e.g., EGF), and invasion (e.g., metalloproteases) of glioma and metastatic cancer cells in the brain [89,90,108,110,125,126]. This evidence concerns the gene VEGFA and glioma.