TGFB1 and neoplasm: Moreover, NK cells, as key components of the innate immune system, are anti-tumor effector cells, which also can be impaired by soluble cytokines present in the TME (including CSC-derived cytokines), such as PGE2, IL-10, TGF-β1, granulin-epithelin precursor (GEP), and IDO 101, 102.