In addition, in breast cancer cells indoleamine 2,3-dioxygenase (IDO)-expressing humanized MSCs (MSC-IDO) were capable of suppressing T-lymphocyte proliferation in vitro as well as reducing tumor-infiltrating CD8+ T cells and B cells in vivo, similar effects were also observed in melanoma and lymphoma tumor models [49]. Here, IDO1 is linked to breast cancer.