Ginsenoside Rg3 improves atezolizumab immune checkpoint therapy in triple-negative breast cancer by targeting FUT8-mediated PD-L1 N-glycosylation

Background: Triple-negative breast Cancer (TNBC) exhibits the highest level of immunogenicity among breast Cancer subtypes, making it particularly responsive to immunotherapy due to tumor immune infiltration and elevated expression of immune markers. Atezolizumab, an important PD-L1 inhibitor, may reduce immunosuppressive signals by blocking PD-L1/PD-1 binding but is limited by its off-target and high cost. Glycosylation, as a key post-translational modification, is recognized for its significant role in regulating PD-L1 protein stability, which in turn promotes PD-L1/PD-1 interaction and facilitates immune evasion. Ginsenoside Rg3 is a bio-active ingredient derived from the traditional Chinese herb ginseng that exerts an acknowledged immunomodulatory effect.

Methods: The potential mechanisms by which Rg3 influences glycosylation of PD-L1 by downregulating FUT8 expression were investigated by western blotting, qPCR, and immunofluorescence. Flow cytometry was integrated with the above experiments to study the suppressive impact of atezolizumab on PD-L1 in both monotherapy and combination therapy. In vitro coculture systems of tumor cells and T cells, combined with an in vivo syngeneic mouse model, were employed to assess cytotoxicity, tumor growth, and T cell activation.

Results: Ginsenoside Rg3 could suppress PD-L1 glycosylation by targeting the E-cadherin/β-catenin/FUT8 pathway to reduce its surface expression on tumor cells. Moreover, downregulating PD-L1 glycosylation enhanced atezolizumab efficacy, resulting in increased T cell activation and cytotoxic function in coculture settings. Additionally, Rg3 synergized with atezolizumab to decrease tumor volume and strengthen anti-tumor T cell immunity.

Conclusion: Our findings demonstrated that ginsenoside Rg3 regulates PD-L1 stability by downregulating its glycosylation, thereby improving atezolizumab efficacy to exert the anti-tumor immune therapy.