TNF and cancer: Indeed, interleukin (IL) -8, macrophage migration inhibitory factor (MIF), and plasminogen activator inhibitor-1 (PAI-1) released by metastatic lung cancer cells were found to be able to activate astrocytes that produced growth factors [i.e., IL-6, IL-1β, and tumor necrosis factor-α (TNF-α)], thus fostering cancer cell growth in the brain niche [17].