Our work suggests that PCC0208025 exhibited anti-tumor effects in B16-F10 tumor isograft model through inhibiting Treg expansion and increasing cytotoxic activity of tumor-infiltrating CD8+ T cells by the blockade of PD-1/PD-L1 binding, which provides the pharmacological basis to develop small molecule inhibitors for PD-1/PD-L1 interactions for PCC0208025 as a lead compound. The gene discussed is CD8A; the disease is neoplasm.