The relationship between the expression of hMLH1 and miR-148a and microsatellite instability in sporadic colorectal cancer
Objective To detect the expression of human mismatch repair gene 1(hMLH1)protein and miR-148a in sporadic colorectal cancer(sCRC)tissue and their relationship with microsatellite instability(MSI).Methods Ninety sCRC tissue specimens and their corresponding normal adjacent tissues were collected from the pathology department of our hospital.Collect clinical medical records of patients,detect tissue DNA microsatellite instability using multiplex fluorescence PCR,detect tissue hMLH1 protein expression using immunohistochemistry staining,detect tissue miR-148a expression using real-time fluorescence quantitative PCR(qPCR),and analyze the targeting relationship between miR-148a and hMLH1 mRNA using dual luciferase reporter assay.Results Among the 90 sCRC tissues,MSI was detected in 29 cases(32.22%)and hMLH1 protein expression was missing in 24 cases(26.67%).According to luciferase reporter gene analysis,miR-148a mimics can inhibit the luciferase activity of reporter gene plasmids containing the 3'UTR-WT sequence of hMLH1 mRNA;Moreover,the relative expression level of miR-148a in hMLH1 protein expression deficient tissues was higher than that in non deficient tissues(P<0.05);In addition,the loss rate of hMLH1 protein expression and the relative expression level of miR-148a in MSI tissues are higher than those in microsatellite stable(MSS)tissues.The loss rate and MSI ratio of hMLH1 protein expression in the right colon and rectum,pN0/1 stage,and pM0 stage were higher than those in the left colon,pN2 stage,and pM0 stage(P<0.05);In addition,the relative expression level of miR-148a in tissues with tumor diameter>5.0 cm,right colon and rectum,pT3/4 phase,pN2 phase,and pM1 phase was lower than that in tissues with tumor diameter≤5.0 cm,left colon,pT1/2 phase,pN0/1 phase,and pM0 phase(P<0.05).Conclusion About 30%of sCRC patients have hMLH1 protein expression deficiency and MSI status.The relative expression level of miR-148a in sCRC tumor tissue is reduced,leading to a weakened inhibitory effect on hMLH1 gene expression,which may be one of the important reasons affecting the MSI status of sCRC tumor cells.
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