IL6 and neoplasm: The present of several immunosuppressive factors in tumor microenvironment including the high production of inhibitory cytokines (interleukin-(IL-) 10, transforming growth factor beta (TGF-β), vascular endothelial growth factor (VEGF), and IL-6), the activation of STAT3, the expansion of Treg cells, and the significant suppressive effect of MDSC has been investigated [55–57, 59–64].