PDCD1 and pancreatic neoplasm: Trafficking into pancreatic tumor microenvironment, endogenous CD8+ T cells reactivate recognition and destruction of neoplastic cells by the combination of programmed cell death protein 1 (PD-1) and C-X-C chemokine receptor type 4 (CXCR4) blockade as the basis for combination immunotherapy in PC (Seo et al., 2019).