PDCD1 and breast carcinoma: In breast cancer and metastatic pancreatic cancer, the addition of ENT to checkpoint inhibition led to significantly decreased suppression by G-MDSCs through decreasing Arg-1 production and diminishing availability of the PD-L1/PD-1 T-cell inhibitory pathway and increase in activated granzyme-B-producing CD8+ T effector cells in the TME (108).