PDCD1 and familial pancreatic carcinoma: Despite the groundbreaking success of immunotherapy with antibodies against immune checkpoints such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed death-ligand 1 (PD-L1) in multiple solid malignancies (10–13), pancreatic cancer remains treatment refractory (14–16).