Licorice Active Constituents-licochalcone A Anti-tumor Pharmacodynamic Research Report

Background: Glycyrrhiza glabra L.,a traditional medicinal,has a history of thousands of years.It is widely used in clinic and has been listed in Chinese Pharmacopoeia.Licochalcone A is a natural product isolated from the root of Glycyrrhiza glabra L.It is also the characteristic chalcone of licorice.It has a variety of pharmacological activities,but its anti-colon cancer mechanism is still unclear.Aim of the study: We explored the potential mechanism of licochalcone A down regulating PD-L1 in colon cancer,and provided new natural candidate compounds for enterprise specific research and development of PD-L1 drugs for colon cancer.Materials and methods: In vitro,the mechanism of licochalcone A at inhibiting PD-L1 expression was investigated by molecular docking,western blot,RT-PCR,flow cytometry,immunofluorescence and immunoprecipitation assays.The co-culture model of T cells and tumor cells was used to detect the activity of cytotoxic T lymphocytes.Colony formation,Ed U labelling,apoptosis,wound healing,invasion and tube formation assays were used to detect changes in cellular proliferation,apoptosis and angiogenesis.In vivo,anti-tumor activity of licochalcone A was assessed in a xenograft model of HCT116 cells.Results: In the present study,we found that licochalcone A suppressed the expression of programmed cell death ligand-1(PD-L1),which plays a key role in regulating the immune response.In addition,licochalcone A inhibited the expressions of p65 and Ras.Immunoprecipitation experiment showed that licochalcone A suppressed the expression of PD-L1 by blocking the interaction between p65 and Ras.In the co-culture model of T cells and tumor cells,licochalcone A pretreatment enhanced the activity of cytotoxic T lymphocytes and restored the ability to kill tumor cells.In addition,we showed that licochalcone A inhibited cell proliferation,angiogenesis and promotes cell apoptosis by targeting PD-L1.In vivo xenograft assay confirmed that licochalcone A inhibited the growth of tumor xenografts.Conclusion: Licochalcone A(LCA)inhibits PD-L1 expression by down regulating NF-κB and Ras/Raf/MEK signaling pathways,consequently suppressing proliferation and promoting apoptosis of tumor cells.In general,this study revealed the anti-colon cancer properties of licochalcone A,and provided new insights into the anti-cancer mechanism of licochalcone A.More importantly,it provides a theoretical basis for the research and development of colon cancer drugs with licochalcone A as a specific target for PD-L1.