IL6 and neoplasm: Several other immunosuppressive molecules including indoleamine 2,3-dioxygenase (IDO), which is an enzyme responsible for tryptophan depletion, and some cytokines such as interleukin 6 (IL-6), interleukin 10 (IL-10), and prostaglandin E2, released from tumor or stromal cells, also contribute to modulating immune cell phenotypes in the TME (Figure 1).