Correlation And Mechanism Of Hypomethylation Of TCF7 And Its High Expression With Risk And Prognosis Of Colorectal Cancer

Objective: Colorectal cancer(CRC)is a common and popular gastrointestinal cancer disease worldwide.Its occurrence and development involve a variety of complex mechanisms,and changes in DNA methylation in epigenetics are an important part of it.Because the methylation change of DNA promoter mainly affects its gene expression level,and the regulatory mechanism of gene promoter low methylation-high mRNA expression plays an important role in the occurrence and development of colorectal cancer,so we adopted TCGA Analysis and screening of methylation and gene expression data of colorectal cancer in the database to find relevant genes with relatively low but important regulatory mechanisms,and conduct preliminary analysis of relevant functions and prognosis to locate TCF7 has also carried out research on the relevance and mechanism of colorectal cancer risk,prognosis,so as to provide new ideas for the diagnosis and treatment of colorectal cancer.Material method: Download TCGA colorectal cancer methylation and mRNA expression data,use R language to calculate differentially expressed genes and differentially methylated genes,bivariate correlation analysis to select low methylation-high expression gene sets,and then use prognostic screening TCF7 with a high methylation-expression negative correlation and a poor prognostic effect was found.Meth HC,oncomine,CCLE and other bioinformatics databases were used to analyze the TCF7 promoter methylation,gene expression,relationship with clinicopathological parameters and the correlation between the two in colorectal cancer,and to verify with q PCR and BSP in clinical samples.The transcription factor database TRAP was used to analyze the transcription factors that may be bound to the5'UTR region of the TCF7 promoter and affected by methylation,and the correlation between the target transcription factor and TCF7 expression was analyzed using the CCLE database.Then use the CCLE database to analyze the differentially expressed genes related to TCF7 low methylation-high expression colorectal cancer cells,and use the DAVID database to analyze the functions of the differentially expressed genes,and use the STRING database and its plug-in cytoscape to find the interaction between the differential genes And the core genes in it,and verified by real-time quantitative PCR.5'UTR fluorescent plasmids with different methylation status were constructed and transfected into 293 T cells,and then double luciferase activity was performed to detect the transcription activity of different methylation status groups.Student-t test and rank-sum test were used to analyze the difference between measurement data groups.Statistical analysis was performed using SPSS 20.0 software(IBM Corporation,Armonk,NY,USA),P<0.05 was defined as having statistical significance.Results: 1)Bioinformatics analysis: 22% of gene promoters in colorectal cancer showed low methylation status,while 70% of genes showed high expression status.TCF7 is a gene with significant promoter hypomethylation-high expression and associated with poor prognosis of patients.2)Bioinformatics analysis found that the TCF7 promoter of colorectal cancer is generally hypomethylated,especially the methylation of the 5'UTR region is significantly lower than that of normal tissues;the expression of TCF7 in colorectal cancer is significantly higher than that of the control group,and it is associated with tumor invasion Significantly correlated with metastasis;TCF7 5'UTR region methylation was significantly negatively correlated with gene expression.Tissue sample test results show that 5'UTR is hypomethylated in colorectal cancer,while TCF7 is highly expressed,and the two are negatively correlated.TCF7 promoter region 5'UTR hypomethylation and high mRNA expression have no significant correlation with prognosis.3)The luciferase activity of TCF7 promoter 5'UTR hypermethylation group decreased significantly.Bioinformatics analysis found that the transcription factor MYB can bind to the Cp G site in the 5'UTR region of the TCF7 promoter;under different methylation binding states,the expression of MYB and TCF7 are highly correlated.The test results of tissue samples found that MYB was significantly correlated with TCF7 expression.4)Bioinformatics analysis: there are 157 differentially expressed genes related to TCF75'UTR low methylation-high expression colon cancer cell line,mainly related to cell adhesion,extracellular matrix composition,collagen and glycoprotein metabolism.The test results of tissue samples found that among the core genes of differential genes,COL4A3 and TCF7 have expression correlation.Conclusion: There are a few promoter hypomethylation-overexpression genes in colorectal cancer,which are mainly related to extracellular matrix and exosome function.The methylation of TCF7 is significantly correlated with expression,and with tumor invasion and metastasis.The poor prognosis of patients is related.TCF7 promoter region 5'UTR methylation can affect gene expression.Genes related to TCF7 promoter region 5'UTR low methylation and high expression are mainly related to cell adhesion,extracellular matrix collagen and glycoprotein metabolism.MYB and COL4A3 are transcription factors regulated by methylation of TCF7 and related core genes with important synergistic relationship with TCF7,respectively.