STAT3 and neoplasm: In the tumor microenvironment, IL-6 is produced by multiple cell types including tumor infiltrating immune cells, fibroblast stromal cells and the tumor cells themselves, induced by various factors such as NF-κB, prostaglandin E2 (PGE2), interleukin-β (IL-1β), hypoxia, the lack of STAT3-inhibitors such as SOCS, microRNAs (miRNA) among others [29–31, 33–35].