PRF1 and neoplasm: Towards the end (day 37) of treatment CD8+ T cells appear to have entered a late stage of tumor killing due to the loss of numerous effector markers including Eomes and perforin (Fig. 5f; see Additional file 10: Figure S10 for CD8+ T cell phenotypes for all groups and tissues) [52], and further supported by the fact that tumors rapidly regress and clear between days 37 to 50 (see Fig. 2c and e).