摘要
Abstract
Objective:Minichromosome maintenance protein 4(MCM4)is a regulator involved in the initiation and elongation stages of DNA replication.This study aims to investigate the correlation between MCM4 expression and immune cells and molecules in the tumor microenvironment(TME)of lung adenocarcinoma(LUAD),and the ability of MCM4 to predict patient sensitivity to immunotherapy and prognosis.
Methods:Transcriptome data and clinical data of LUAD patients were downloaded and analyzed from The Cancer Genome Atlas(TCGA)and Gene Expression Omnibus(GEO)databases.The training set comprised 503 patients from the TCGA dataset,while the validation set comprised 857 patients from the GEO dataset.The expression of MCM4 in normal and tumor tissues was analyzed using the tumor immune estimation resource(TIMER)database.LUAD tumor samples were divided into MCM4 low expression and MCM4 high expression groups,and R software was used to analyze the relationship between MCM4 expression and overall survival(OS)of LUAD patients.Gene set enrichment analysis was performed using gene sets from the Kyoto Encyclopedia of Genes and Genomes(KEGG)to identify biological processes related to MCM4 gene expression.The Tumor Immune Dysfunction and Exclusion(TIDE)score was used to predict the efficacy of immunotherapy in LUAD patients.Immune scores,stromal scores,and estimation of stromal and immune cells in malignant tumor tissues using expression data(ESTIMATE)scores were assessed to analyze the relationship between MCM4 expression and immune cells and immune checkpoints(ICs)in the TME.Clinical validation was conducted using immunohistochemical staining on 60 biopsy or surgical specimens diagnosed as LUAD(55 of LUAD cancerous tissues and adjacent tissues,5 of normal lung tissues)from Renmin Hospital of Wuhan University.
Results:Differential expression of the MCM4 gene and protein was observed between normal lung tissue and adenocarcinoma tissue.In both the training and validation sets,patients in the MCM4 low expression group had better OS compared to those in the MCM4 high expression group.MCM4 expression was associated with prognosis in LUAD patients.MCM4 expression was significantly correlated with oocyte meiosis,cell cycle,and DNA replication pathways,and positively correlated with Ki-67 coding gene MKI67 and proliferation-related gene C1orf112.MCM4 expression was negatively correlated with TIDE score and positively correlated with ICs expression,indicating that MCM4 expression could predict the efficacy of immunotherapy in patients.Compared to the MCM4 low expression group,the MCM4 high expression group had higher tumor purity and lower proportions of stromal cells and immune cells.MCM4 expression was negatively correlated with CD8+T cells and significantly positively correlated with Th2 cells and myeloid-derived suppressor cells,indicating that high expression of MCM4 in tumor tissue was associated with poor prognosis in patients.Pan-cancer analysis results showed that in most tumors among 33 types,MCM4 expression was positively correlated with the expression of ICs,Th2 cells,regulatory T cells,programmed death-1(PD-1),programmed death-ligand 1(PD-L1),and PD-1-PD-L1 score,and negatively correlated with CD8+T cells and NK cells.Clinical data validation results showed that MCM4 staining intensity and the positive cell proportion were higher in tumor tissue than in tumor stroma.MCM4 score was significantly positively correlated with Ki-67.
Conclusion:MCM4,as a proliferation signal,affects immune infiltration and prognosis in lung adenocarcinoma,and high expression of MCM4 is associated with increased infiltration of inhibitory immune cells and increased probability of immunotherapy benefits in the TME.关键词
微小染色体维持蛋白4/肺腺癌/增殖/免疫抑制/预后Key words
minichromosome maintenance protein 4/lung adenocarcinoma/proliferation/immunosuppression/prognosis
