PDCD1 and cancer: The synergistic effect between TGF-β inhibitor (e.g. anti-TGF-β, receptor kinase inhibitor, cancer vaccine) and anti-PD-1/PD-L1 has been validated in multiple murine tumor models, including but not limited to CT26 (mouse colon cancer), MC38 (mouse colon cancer), 3LL (mouse Lewis lung cancer), and EMT-6 (mouse breast cancer) (47, 54, 138, 139).