PDCD1 and renal cell carcinoma: In renal cell carcinoma, there is a potential interaction between CD8+CD39+PD-1+ T cells and Foxp3+PD-1+ Treg cells due to the proximity between the cells, forming a spatial niche that is more specialized for immunosuppression under PD-1 blockade, which is more evident in metastatic lesions [82].