Expression And Clinical Significance Of CD73 In EGFR-Mutant Lung Adenocarcinoma

Background and Objective:Lung cancer is the malignant tumor with the highest morbidity and mortality in China.Immunotherapy is a research hotspot in recent years,programmed cell death protein 1(PD-1)/programmed cell death protein ligand 1(PD-L1)immune checkpoint inhibitors have become one of the standard treatments for advanced non-small cell lung cancer.However,patients with advanced non-small cell lung cancer with epidermal growth factor receptor(EGFR)mutations do not respond well to immune checkpoint inhibitors.tyrosine kinase inhibitors(TKIs)are still the standard first-line treatment.However,most patients will inevitably develop drug resistance after treatment with TKIs.For patients with drug resistance,the classical treatment is platinum-based systemic chemotherapy,but the efficacy is poor.In recent years,CD73 has become a research hotspot.Studies have shown that the high expression of CD73 is related to the poor prognosis of a variety of cancers,and is related to the inhibitory tumor microenvironment.The high expression of CD73 may serve as a potential therapeutic target to enhance the efficacy of immune checkpoint inhibitors in EGFR-mutant NSCLC patients who developed resistance to TKIs.Therefore,the aim of this study is to explore the expression of CD73 in EGFRmutant lung adenocarcinoma patients,the effect of CD73 expression level on the prognosis of patients,and the signaling pathway mediated by CD73.Meanwhile,the dynamic changes of CD73 in patients’ baseline tumor tissues and tissues after TKIs treatment resistance,and the relationship between CD73 and tumor microenvironment were also investigated.The aim of this study is to provide new clues for the treatment of lung adenocarcinoma patients with EGFR mutations.Methods:In the first part,the expression of CD73 mRNA in EGFR-mutant,EGFR-wild-type lung adenocarcinomas and EGFR-mutant adjacent normal tissues was explored using public databases.The relationship between CD73 expression and prognosis,clinicopathological factors,tumor microenvironment,immune checkpoints,and CD73mediated signaling pathway in lung adenocarcinoma patients with EGFR mutation were investigated.At the same time,immunohistochemical staining was used to detect CD73 protein in 42 cases of advanced lung adenocarcinoma with EGFR mutation and 40 cases of advanced lung adenocarcinoma with EGFR wild type.CD8,Foxp3 and PDL1 protein were detected in patients with EGFR mutation.To explore the expression of CD73 in advanced lung adenocarcinoma with EGFR mutation and its effect on tumor immune microenvironment at the protein level.In the second part,immunohistochemical staining was used to detect the expression of CD73,CD8,Foxp3 and PD-L1 in the baseline and pathological tissue samples of 26 patients with EGFR-mutant advanced lung adenocarcinoma who developed resistance to TKIs.The relationship between CD73 expression and CD8,Foxp3 and PD-L1 in the tumor microenvironment after drug resistance was also explored.Results:1.The Cancer Genome Atlas(TCGA)public data analysis showed that the expression of CD73 mRNA was higher in lung adenocarcinoma with EGFR mutation than that with EGFR wild type,and the expression level was significantly positively correlated with EGFR mRNA.High expression of CD73 mRNA is an independent poor prognostic factor for lung adenocarcinoma with EGFR mutation.High expression of CD73 mrna is associated with shorter Progression-Free Survival(PFS)and Overall Survival(OS)in patients with lung adenocarcinoma.In lung adenocarcinoma with EGFR mutation,high expression of CD73 was closely related to lower microsatellite instability(MSI)and higher hypoxia fraction.The expression of CD73 mRNA was negatively correlated with the infiltration level of CD8+T lymphocytes,natural killer cells and myeloid dendritic cells,and positively correlated with the infiltration level of tumor-associated fibroblasts.There was no significant correlation between CD73 mRNA expression and age,gender,tumor stage and tumor mutation burden.CD73 may mediate phosphatidylinositol 3kinase/protein-serine-threonine kinase in EGFR-mutated lung adenocarcinoma by mediating PI3K/protein-serine-threonine kinase.Common oncogenic pathways such as AKT and mitogen-activated protein kinase(MAPK)promote the occurrence and development of tumors and the formation of inhibitory tumor microenvironment.2.Immunohistochemical staining results showed that the expression level of CD73 protein in the tumor cells of advanced lung adenocarcinoma with EGFR mutation was significantly higher than that in the surrounding tissues,and the high expression rate of CD73 protein(staining score≥50%)in advanced lung adenocarcinoma with EGFR mutation was higher than that in advanced lung adenocarcinoma with EGFR wild type.There was no significant correlation between CD73 expression and age,gender,smoking history and tumor stage in advanced lung adenocarcinoma with EGFR mutation.In advanced lung adenocarcinoma with EGFR mutation,the expression level of CD8 protein in tumors with high CD73 expression was significantly lower than that in tumors with low CD73 expression.The expression of CD73 protein was positively correlated with the expression of PD-L1 in tumors after TKIs resistance.Conclusions:1.CD73 expression was higher in EGFR-mutant lung adenocarcinoma patients than in EGFR-wild type lung adenocarcinoma patients,and CD73 high expression was an independent poor prognostic factor.2.In EGFR-mutant lung adenocarcinomas,high expression of CD73 was associated with lower infiltration levels of CD8+T lymphocytes,natural killer cells and myeloid dendritic cells,higher infiltration levels of tumor-associated fibroblasts,lower microsatellite instability and higher hypoxia fraction.3.CD73 may promote the occurrence and development of tumors and the formation of inhibitory tumor microenvironment by mediating the oncogenic pathways such as PI3K/AKT and MARK in lung adenocarcinoma with EGFR mutation.4.There was a significant positive correlation between CD73 expression and PD-L1 expression in advanced lung adenocarcinoma patients with EGFR mutation who were resistant to TKIs.5.High expression of CD73 is a potential therapeutic target for EGFR-mutant lung adenocarcinoma patients.Targeting CD73 may reverse the suppressive tumor microenvironment,thereby enhancing the efficacy of immune checkpoint inhibitors.