PDCD1 and neoplasm: In our current study, regorafenib or cabozantinib + anti-PD-1 antibody, with or without chidamide treatment, significantly reduced Tregs in tumors, suggesting that the anticancer activity may be attributed to Treg suppression, as shown in Figure 2F. These findings were consistent with a previous study showing that VEGF binds to the VEGF co-receptor neuropilin1 in Tregs, which is critical for tumor homing [41], and cabozantinib decreased Treg-mediated tumor infiltration, which would improve the T-cell immune response [42].