Immunomodulatory properties are also of great importance in malignant tumor diseases, especially within the tumor microenvironment (TME), where MSCs influence tumor biology and immunology by releasing cytokines, chemokines and growth factors [1,9,10] such as transforming growth factor-β1 (TGF- β1), tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ) and hepatocyte growth factor (HGF), as well as interleukin-6 (IL-6) and indoleamine 2,3-dioxygenase (IDO) [11,12,13]. The gene discussed is IDO1; the disease is neoplasm.