CXCL8 and central nervous system cancer: IL-33 exists in nuclear and secretory forms; nuclear IL-33 stimulates glioma cells to express inflammatory cytokines (IL-1β, IL-8, IL-6, etc.), and secretory IL-33 is secreted by glioma cells, which activates microglia and drives them to a pro-tumor phenotype; both synergistically accelerate glioma progression (152).