PDCD1 and cancer: It was reported that the binding of PD-L1 to PD-1 may cause T cell apoptosis, anergy, exhaustion, and interleukin-10 (IL-10) expression, suggesting that PD-L1 can act as a defender for PD-L1+ cancer cells from CD8+ T cell–mediated lysis (12, 13) (Figure 1).