To investigate the effect of SUMOylation on lymphocytes in peripheral blood, we treated PBMC of 27 lung cancer patients receiving PD-1 treatment with different concentrations of 2-D08 (a specific inhibitor of SUMOylation) in vitro, and analyzed the activation status (CD69+) and the death rates (Annexin V+) of different lymphocyte subsets by flow cytometry analysis. This evidence concerns the gene PDCD1 and lung cancer.