MKI67 and head and neck squamous cell carcinoma: Furthermore, TCF-1+Ki67+CD8+ TILs, a key predictor of ICB efficacy in breast cancer37, showed a significantly higher CD39+PD-1+ positivity rate compared to TCF-1+Ki67-CD8+ TILs in the HNSCC dataset (Fig. S3H), indicating that many highly proliferative TCF-1+CD8+ T cells are reflective of CD39+ Tpex cells.