ABSTRACT
Objective:To investigate the role of celecoxib in inhibiting liver cancer and to explore the potential molecular mech-anisms.Methods:A total of 65 cases of patients with primary hepatocellular carcinoma(HCC) underwent surgical treatment in our hospital from February 2012 to June 2016 were recruited as study object.Another 15 cases of normal liver tissue offered by the department of hepatobiliary surgery were selected as control.Immunohistochemical staining(IHC) was used to detect the expression level of COX-2 and PD-1 in tumor and normal tissue samples.Pearson correlation analysis were used to evaluate the correlation between COX-2 and PD-1 in HCC patients.Construction of H22 hepatoma cells bearing BALB/c mice model,randomly divided them into control group,celecoxib group and PD-1 antibody group(15 mice for each group).Sacrificed all mice alive at the end of the 4th weeks after the treatment and removed the tumors then.The tumor growth curves and survival curves were drawn to observe the anti-tumor effect.IHC were used to evaluate the expression of COX-2,PD-1 as well as the number of CD8+T and foxp3 positive Treg cells in tumor tissue.Flow cytometry were used to determine the number of CD8+T and CD4+CD25+Treg cells in peripheral blood.The peripheral blood mononuclear cell(PBMC) of BALB/c mice were separated and scramble or PD-1 siRNA were transfected then,Western blot analysis were used to detected the level of COX-2,PD-1,CD8 and Foxp3 after the treatment of celecoxib.Results:IHC results showed that the expression level of COX-2 and PD-1 in tumor tissue of HCC patients were significant higher than control(P<0.001).Pearson correlation analysis showed COX-2 were both positive correlated with PD-1 in the tumor tissue of HCC patients(R2=0.673,P<0.001).The tumor growth curves and survival curves in celecoxib or PD-1 antibody groups were significant better than in control group (P<0.05).There were no significant difference of tumor growth curves and survival curves between celecoxib group and PD-1 antibody group(P>0.05).IHC and flow cytometry analysis showed that celecoxib treatment significant decreased the expression level of PD-1(P<0.05).Both celecoxib and PD-1 antibody treatment significant increased the number of CD8+T cells while decreased the number of Treg cells in the tissue or the peripheral blood(P<0.05).Western blot analysis showed that celecoxib significant decreased the level of COX-2,PD-1,CD8 and Foxp3 in PBMCs,while it did not affect the level of CD8 and Foxp3 in PD-1 siRNA transfected PBMCs.Conclusion:The expression level of COX-2 and PD-1 were increased in the tumor tissue of HCC patients.Celecoxib may inhibit liver cancer by regulating PD-1 mediated tumor immune via inhibiting COX-2.