Studies [50] have suggested that compared to Tregs in peripheral blood, tumor-infiltrating Tregs exhibit more proliferative and immunosuppressive phenotypes, with increased expression of CTLA-4, CD25, GITR, 4−1BB, OX40, ICOS, LAG-3, TIM3, TIGIT, and PD-1. This evidence concerns the gene PDCD1 and neoplasm.