| Background and purpose:Lung cancer is the most common type of tumor worldwide and the number one cause of cancer death.Non-small cell lung cancer(NSCLC)is the type with the largest proportion of lung cancer,and lung adenocarcinoma is an important component of non-small cell lung cancer.Driver gene mutation is one of the important reasons for the development of nonsmall cell lung cancer,and affects the efficacy of various lung cancer treatment methods including immunotherapy.Among them,the kinase-dead mutation of the driver gene LKB1 is considered to be an important cause of resistance to immune checkpoint inhibitor therapy in patients with non-small cell lung cancer.Therefore,exploring the impact of LKB1 gene mutations on the immune microenvironment and the underlying regulatory mechanism is of great significance for the selection of appropriate treatment methods for precise treatment of lung cancer patients with LKB1 gene mutations.Immune checkpoint inhibitor therapy with the PD-1/PD-L1 signal axis as the target has achieved encouraging good results in the treatment of a variety of tumors,including lung cancer.Although there is some controversy,the expression of PD-L1 on the surface of tumor cells is also considered as a biomarker predicting the effectiveness of immune checkpoint inhibitors.Previous studies have observed low expression of PD-L1 in tumor cells from patients with LKB1 mutations.However,there are few reports on the specific regulatory mechanism of LKB1 on PD-L1 expression,and the relationship between LKB1 mutation,tumor immune microenvironment,and PD-L1 expression remains to be determined.In this study,TCGA and GEO databases were used to determine the PD-L1 expression pattern in tumor cells from patients with LKB1 mutations.It was experimentally verified that the regulation of PD-L1 expression by LKB1 gene mutation requires the presence of IFN-y in the tumor microenvironment and activation of the IFN-y signaling pathway.The specific mechanism of LKB1 regulating PD-L1 expression in tumor cells through IFN-y signaling pathway was also discussed.Methods:This study analyzed and compared the differentially expressed genes of patients with lung adenocarcinoma in the TCGA and GEO databases,and established an in vitro cell model of LKB1-k78i kinase-dead mutation by lentivirus transfection of Calul cells,H358 cells and A549 cells.The relationship between the LKB1 mutation and PD-L1 expression in the above cells was verified by Western blot method.At the same time,a recombinant IFN-y stimulated culture system was used to simulate the immune microenvironment of IFN-γ.Relationship between PD-L1 expression.And through Western blot,qRT-PCR and bioinformatics analysis,we explored the specific regulation mechanism of LKB1 mutation on PD-L1 expression.Results:Analysis of the results from public databases and in vitro experiments indicate that the regulation of PD-L1 by LKB1 gene mutation requires the participation of the immune microenvironment.In the presence of IFN-y,LKB1 can inhibit the up-regulation of PD-L1 by IFN-γ,resulting in the relative down-regulation of PD-L1.Further test results showed that in the presence of IFN-y,the level of phosphorylation-activated Statl decreased and the expression of JAK1 decreased after LKB1 mutation,resulting in a decrease in the sensitivity of the JAK1-Statl signaling pathway and a decrease in PD-L1 expression.Further analysis of this regulatory effect shows that the regulation of the JAK1-Statl pathway by the LKB1 mutation may be mediated by PDGFB and IRF3.Conclusion:The lung cancer driver gene LKB1 kinase-dead mutation can inhibit the activity of the IFN-y-JAK1-Statl signaling pathway,thereby inhibiting the strong up-regulation of PD-L1 expression by IFN-γ,which is manifested by the reduced expression of PD-L1 after LKB1 mutation.This may be the molecular basis for the poor efficacy of immunotherapy in patients with LKB1 mutations.LKB1 mutation is a potential biomarker for immunotherapy in patients with lung adenocarcinoma. |
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