Another major source of IL-6 is tumor-associated macrophages (TAMs), which secrete additional cytokines, such as IL-10, IL-34 and colony-stimulating factor 1 (CSF1), all of which contribute to chemoresistance in breast, lung, colorectal, prostate and pancreatic cancers [37,38,39,40,41]. Here, CSF1 is linked to neoplasm.