To confirm this observation at protein level, 24 formalin-fixed paraffin-embedded tumor samples were collected from NSCLC patients treated with an anti-PD-1 antibody sintilimab (Supplementary Table 2) and examined for PD-L2 and FOXP3 expression with IHC and multiplex IHC assays. Here, PDCD1 is linked to non-small cell lung carcinoma.