PRF1 and neoplasm: We further investigated the function of tumor-infiltrating CD8+ T cells by analyzing CD62L−CD44+ T cells to identify effector memory CD8+ T cells, which were previously shown to exhibit upregulated expression of cytotoxic markers, including tumor necrosis factor-α (TNF-α), granzyme B and perforin, compared to central memory CD8+ T cells and to exhibit antitumor activity.25 Treatment with MS-20 combined with an anti-PD1 antibody significantly increased the effector memory CD8+ T cells subpopulation compared to that in the vehicle control and anti-PD1 group (Figure 1e).