CD274 and neoplasm: Tumor cell derived extracellular PD-L1 promoted immune invasion in tumor immune microenvironment by binding to its receptor PD-1 [39] and triggering intracellular cell death pathway [43], and this study investigate this issue by co-culturing the NSCLC cells with CD8+ T cells isolated from human peripheral blood mononuclear cells (hPBMCs) in a transwell co-culturing system to avoid direct cell-to-cell contact (Fig. 8a), which excluded the possibility that CD8+ T cells interacted with the tumor antigens presented in NSCLC cell membranes, but merely interacted with the secreting tumor antigens.