PDCD1 and neoplasm: In triple-negative breast cancer (TNBC), high tumor infiltrating lymphocytes and programmed cell death ligand 1 receptor (PD-L1) on tumor cells or in the tumor microenvironment predict the response to chemotherapy (13) and the clinical activity of anti-PD-1 immune check-point inhibitors (14, 15), thereby suggesting a potential candidate for the clinical development of highly cytotoxic NK cell-based immunotherapy.