PDCD1 and neoplasm: NK cells provide first-line defense against malignantly transformed cells [38]; [39] and recent evidence of the use of antibodies blocking the immunosuppressive receptor programmed cell death 1 (PD-1) pathway underscored the central role of reinduction of host immune system and of potentiating the NK-cell mediated cytotoxicity in several tumor prognosis [40]; [41] including CRC [3].