IL6 and central nervous system cancer: Elevated levels of pro-inflammatory cytokines (e.g., interleukin-6, tumor necrosis factor α, interferon α, interferon γ and transforming growth factor β) and neurotransmitters (e.g., dopamine, norepinephrine and serotonin) may be crucial contributors to the development of both depressive/anxiety disorders and glioma [30, 32–35].