Schisanhenol Inhibits the Proliferation of Hepatocellular Carcinoma Cells by Targeting Programmed Cell Death-ligand 1 via the STAT3 Pathways.

Background: Programmed cell death-ligand 1 (PD-L1) is overexpressed in tumor cells, which promotes tumor cell survival and cell proliferation and causes tumor cells to escape T-cell killing. Schisanhenol, a biphenyl cyclooctene lignin-like compound, was extracted and isolated from the plant named Schisandra rubriflora (Franch.).

Purpose: In this work, we studied the anticancer potential of schisanhenol and explored whether schisanhenol mediated its effect by inhibiting the expression of PD-L1 in vitro and in vivo.

Materials and methods: In vitro, we performed western blot, immunofluorescence, immunoprecipitation, and colony formation assays to study the proteins, genes, and pathways related to the anti-tumour activity of schisanhenol. In vivo, we explored the antitumor activity of schisanhenol through orthotopic liver transplantation and subcutaneous transplantation tumor models of hepatocellular carcinoma (HCC) cells.

Results: We found that schisanhenol decreased the viability of HCC cells. It inhibited the expression of programmed cell death ligand-1 (PD-L1), which plays a pivotal role in tumorigenesis. Subsequently, schisanhenol suppressed the expression of PD-L1 by decreasing the activation of STAT3. Furthermore, we found that schisanhenol inhibited the activation of STAT3 via JAK/STAT3 (T705), Src/STAT3 (T705), and PI3K/AKT/mTOR/STAT3 (S727) pathways. Colony formation tests showed that schisanhenol suppressed cell proliferation by inhibiting PD-L1. Schisanhenol also enhanced cytotoxic T lymphocytes (CTL) activity and regained their ability to kill tumour cells in co-culture. Finally, in vivo observation confirmed the antitumor activity of schisanhenol.

Conclusion: Schisanhenol inhibits the proliferation of HCC cells by targeting PD-L1 via the STAT3 pathways. These findings prove that schisanhenol is a valuable candidate for HCC therapeutics and reveal previously unknown characteristics of schisanhenol.