The increased PD-L1 expression induces poorer prognosis in melanoma. The small molecule inhibitors of PD-1/PD-L1 pathways have been an encouraging drug development strategy because of good affinity and oral bioavailability without immunogenicity and immunotoxicities of PD-1/PD-L1 antibodies. In this study, we studied the effects of PCC0208025 (BMS202), a small molecule inhibitor of PD-L1, on PD-1/PD-L1 binding and the cytokines secretion in human CD3 + cells in vitro. We also investigated the antitumor and immunomodulatory activity of PCC0208025 and the pharmacokinetics properties in B16-F10 melanoma-bearing mice. The results showed that PCC0208025 inhibited the PD-1/PD-L1 proteins binding, and rescued PD-L1-mediated inhibition of IFN-γ production in human CD3 + T cells in vitro. Furthermore, in B16-F10 melanoma-bearing mice, PCC0208025 presented the antitumor effects, enhanced IFN-γ levels in plasma, increased the frequency of CD3 + CD8 + T and CD8 + IFN-γ + T and the ratios of CD8 + /Treg, and deceased the CD4 + CD25 + CD127 low/− (Treg) number in tumor. Pharmacokinetics study found that PCC0208025 was absorbed and distributed into the tumors with much higher concentrations than those of the blockade against PD-1/PD-L1 binding. Our work suggests that PCC0208025 exhibited anti-tumor effects through inhibiting Treg expansion and increasing cytotoxic activity of tumor-infiltrating CD8 + T cells by the blockade of PD-1/PD-L1 binding, which may provide the pharmacological basis to develop small molecule inhibitors of PD-1/PD-L1 binding for PCC0208025 as a lead compound.
The purposes of this study are to investigate the antitumor activities of NSK-01105, a novel sorafenib derivative, in in vitro and in vivo models, and explore the potential mechanisms. The effects of NSK-01105 on proliferation and apoptosis of prostate cancer cells were established by cytotoxicity assays, apoptosis analysis, flow cytometry analysis, and Western blot analysis. Two xenograft tumor models were used to verify the therapeutic effect of NSK-01105 in vivo. NSK-01105 exhibited broad-spectrum antitumor activity, particularly in prostate cancer cells. Characterization of apoptosis morphology was observed, and the percentage of apoptosis-positive cells significantly increased after NSK-01105 treatment for 24 h. Furthermore, a significant increase of the "sub-G1" population in LNCaP and PC-3 cells after NSK-01105 treatment was determined by cell cycle analysis. Tumor growth was significantly suppressed by once daily oral 30 mg/kg dose of NSK-01105 with the inhibition rates of 63.82% in LNCaP models and 64.29% in PC-3 models, respectively. The activation of Raf-1 kinase and epidermal growth factor receptor was downregulated by NSK-01105 at 10 μmol/L. Consequently, the dual inhibitions of Raf/MEK/ERK and PI3K/Akt/mTOR signal pathways were observed by Western blot analysis. Collectively, our results suggest a role of NSK-01105 in treatment for human prostate tumors by inhibiting cell proliferation and inducing apoptosis. NSK-01105 appears to be a promising orally active anticancer drug and deserves further investigation.
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