PDCD1 and cancer: Ishida and his colleague (Ishida et al., 1992; Dong et al., 1999; Fitzsimmons and Sadkowsky, 2002) first discovered that PD-1 (CD279) can induce apoptosis in mouse T-cell hybridoma since 1992, there have been more and more studies on PD-1/PD-L1, which has become a “superstar” in cancer research.