As PD-1 expression was elevated in the TILs of the ENKL tissues, and PD-L1 and PD-L2 expression was elevated in the tumor cells and cell lines, coculture experiments of the SNK-6 cells and purified allogeneic CD8+ T cells (effector:target ratio, 10:1) were established by simulating the tumor microenvironment in vivo. Here, CD8A is linked to neoplasm.