Glioma cells activate the MEK (A kinase of MAPK)/ERK (extracellular regulated protein kinases) signaling pathway by secreting cytokines that downregulate the expression of aquaporin 1 (AQP1, a transmembrane glycoprotein involved in tumor angiogenesis) on microglia, attenuate their response to pro-inflammatory factors, and convert them to a pro-tumor phenotype, ultimately promoting tumor progression. The gene discussed is GPNMB; the disease is neoplasm.