PDCD1 and pancreatic neoplasm: Although immune checkpoint inhibitors, such as cytotoxic T lymphocyte protein 4 (CTLA4) and programmed cell death protein 1 (PD-1) have shown promise for the treatment of multiple cancers, these agents demonstrate limited responses for the treatment of patients with PDAC, probably due to the multiple immune-regulatory pathways within the pancreatic tumor microenvironment (TME) [8].