During the later phase of tumor growth (days 11–14) (Figure 7C and Supplemental Figure 12, G–I), CD44hiCD62loTcf1–CD8+ TILs in WT mice gradually gained expression of immune checkpoint molecules (PD-1, Tim3, Lag3, Ctla4) and TOX, a master transcription factor responsible for reprograming CD8+ T cells into the exhausted state (35, 36). Here, CTLA4 is linked to neoplasm.