Effect Of EZH2 On The Immune Microenvironment Of Malignant Pleural Mesothelioma

Objective:To detect the expression of EZH2 in Malignant pleural mesothelioma（MPM）,and to further investigate the effect of Enhancer of zeste homolog 2（EZH2）on the immune microenvironment.Methods:A total of 20 patients with pathological diagnosis of MPM after operation from January 2016 to December 2020 in The Affiliated Hospital of Inner Mongolia Medical University,with an average age of 63.8±5.95 years,including 12 males and 8 females,were collected and archived for tissue wax block sections.Immunohistochemistry（IHC）was used to determine the expression of EZH2,DNMT1,CXCL9 and CXCL10 in MPM tissues.Multiplex fluorescence immunohistochemical Staining（mf-IHC）was used to detect the distribution of CD8⁺T cells and CD68⁺HLA-DR⁺（M1-type Tumor-associated macrophage,TAMs）,CD68⁺HLA-DR^-（M2-type TAM）,CD56^bright Natural killer（NK）and CD56^dim NK cell.The correlation between EZH2 and DNMT1,CXCL9 and CXCL10expression and its effect on the above immune cells were analyzed by statistical method.Results:1.Among the 20 MPM tissues,18 cases had high expression of EZH2,with a high expression rate of 90%;19 cases had high expression of DNMT1,with a high expression rate of 95%;and 18 cases had high expression of CXCL9,with a high expression rate of 90%;13cases had high expression of CXCL10,and the high expression rate was 65%.2.EZH2 and DNMT1 were co-highly expressed in 18 cases,with a high expression rate of 90%（18/20）,and co-lowly expressed in 1 case,with a low expression rate of 5%（1/20）;EZH2 and CXCL9 were co-high expressed in 17 cases,the high expression rate was 85%（17/20）,and 1 case was co-low expression,and the low expression rate was 5%（1/20）;EZH2and CXCL10 were co-highly expressed in 11 cases,with high expression rate of 55%（11/20）.There were 0 cases of common low expression,and the low expression rate was 0%（0/20）.The common high expression rate of DNMT1,CXCL9 and CXCL10 was 85%（17/20）and 60%（12/20）,respectively,and the common low expression rate was 0%（0/20）.Spearman correlation analysis was used to analyze their correlation,and the results showed that EZH2was positively correlated with DNMT1（r_s=0.474,P=0.035）;EZH2 was negatively correlated with CXCL10 expression（r_s=0.462,P=0.04）;EZH2 showed a weak negative correlation with the expression of CXCL9,and the result was not statistically significant（P>0.05）.There was a weak negative correlation between DNMT1 and the expression of CXCL9 and CXCL10,and the results were not statistically significant（P>0.05）.3.The distribution of CD8⁺T cells,M1-type TAM,M2-type TAM,CD56^bright NK cell and CD56^dim NK cell was detected by mf-IHC method in the MPM tissues.There were differences in the distribution of CD8⁺T cells,M1-type TAM,M2-type TAM,CD56^bright NK cell and CD56^dim NK cell in the tumor parenchyma area and tumor interstitial area between different individuals.The cell density of CD8⁺T cell,M1-type TAM,M2-type TAM,CD56^bright NK cell and CD56^dim NK cell in tumor stroma was higher than that in tumor parenchyma（P<0.05）.4.The expressions of EZH2,DNMT1,CXCL9 and CXCL10 were not correlated with the cell density of CD8⁺T cells in tumor parenchyma and tumor stroma（P>0.05）.5.The expression of EZH2 was negatively correlated with the density of CD56^dim NK cell in tumor parenchyma and tumor interstitium（P=0.02）,but not with the density of CD56^dim NK cell in tumor interstitium（P>0.05）.EZH2 expression was not correlated with CD56^bright NK cell density in tumor parenchyma and tumor stroma（P>0.05）.6.The expression of EZH2 was negatively correlated with the cell density of M1-type TAM in tumor parenchyma and tumor stroma（P=0.009,0.036）,and DNMT1 was positively correlated with the cell density of M1-type TAM in tumor stroma（P=0.038）.EZH2expression was no correlation between M2-type TAM in tumor parenchyma and tumor stroma（P>0.05）.Conclusion:1.EZH2 and DNMT1 are highly expressed in MPM,and both EZH2 and DNMT1 may be involved in inhibiting the expression of Th1-type chemokine CXCL10.2.There is heterogeneity in the immune microenvironment among different MPM individuals,and there are differences in the infiltration of immune cells in the tumor stroma and tumor parenchyma.3.EZH2 may inhibit the tumor infiltration of M1-type TAM and NK cells in MPM.