Tannins in Terminalia bellirica inhibits hepatocellular carcinoma growth via re-educating tumor-associated macrophages and restoring CD8+T cell function

Tumor-associated macrophages (TAMs) are the major immunosuppressive components infiltrating the tumor microenvironment (TME). Targeting TAMs has emerged as a promising strategy to remodel immunosuppressive TME and enhance T-cell mediated anti-tumor immunity for cancer therapy. In this study, we investigate the effect and mechanism of total tannin fraction of Terminalia bellirica (Gaertn.) Roxb. (TB-TF) against hepatocellular carcinoma (HCC) using established Hepa1-6 orthotopic mouse model and murine bone marrow derived macrophage polarization model. Here we showed that TB-TF significantly inhibited orthotopic tumor growth and promoted the polarization of M2-TAMs toward the anti-tumor M1 phenotype in vivo. Further studies showed that TB-TF reversed tumor-conditioned medium induced M2 polarization of macrophages as indicated by increased expression of TNF-alpha, IL-1 beta, and iNOS, and decreased expression of Arg-1, thereby re-educating macrophages cocultured with tumor-conditioned medium into M1 phenotype. In addition, we found that TB-TF also promoted T cell infiltration mediated by chemokines such as CCL5 and CXCL10, and restored the cytotoxic function of CD8+T cells as evidenced by upregulated expression of Granzyme B, Perforin, and IFN-gamma. Our data suggest TB-TF as a promising anti-cancer agent, mediates its anti-tumor effects via remodeling the tumor immunosuppressive microenvironment, indicating its potential in the immunotherapy for hepatocellular carcinoma.

Automated summary

The study shows that the total tannin fraction of Terminalia bellirica (TB-TF) can inhibit hepatocellular carcinoma growth, promote the polarization of tumor-associated macrophages towards an anti-tumor phenotype, increase T cell infiltration, and restore cytotoxic function of CD8+T cells.