IL6 and cancer: TANs provide a favorable environment for cancer development, angiogenesis and metastatic spread by secreting cytokines and chemokines, such as interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor α (TNF-α) and vascular endothelial growth factor (VEGF) [26,27].