Study Of DNA Hypermethylation And Expression Of MicroRNA-375Gene In Patients With Gastric Cancer

Objective:Gastric carcinoma(GC) is one of the most common malignancies worldwide,and accounting for the first common cause of cancer-related death in China at present. GC is often asymptomatic or causes only nonspecific symptoms in its early stages so that it is very important to find new methods for early diagnosis and treatment.DNA methylation is the most well defined epigenetic mechanism and plays an important role in maintaining the normal cell function,genetic imprinting,embryonic development and human tumorigenesis.DNA hypomethylation is the initial epigenetic abnormality recognized in most regions of human tumors, and regional hypermethylation of anti-oncogenes can occur very early in tumorigenesis.MicroRNAs (miRNAs) are a class of18～25-nucleotide (nt)-long noncoding RNAs expressed by all metazoan eukaryotes.As is often the case for aberrant expressions of miRNAs, the common mechanisms include the epigenetic modification of miRNAs, especially the altered DNA methylation triggers the miRNAs silencing.The deregulation of miRNAs has great influence on oncogenesis,tumor development and differentiation.The expression level of miRNA-375is relatively lower in some malignant tumor,such as GC and esophageal carcinoma. Bioinformatic studies indicate that miRNA-375close to or overlapping with CpG islands and within promoter regions could be involved in autoregulation of the methylation. In order to provide clues on using miRNA methylation status as potential diagnosis and therapy target, we detect aberrant DNA methylation of miRNA-375gene and its expression in GC tissues, explore the effection of methylation on the expression, and further predicte potential target for miRNA-375in GC.Methods:1A total of90subjects were divided into GC group (n=54) and control groups (n=36).2To predict CpG island with respect to the promoter of miRNA-375and design primers for DNA methylation specific PCR (MSP) by bioinformatics.The methylation status of miRNA-375gene promoter methylation was detected by MSP.3The expression of miRNA-375gene was detected by real-time fluorescent quantitative reversed transcriptive PCR (real-time qRT-PCR).4To predict the possible targets of miRNA-375by bioinformatics.Results:1DNA methylation of miRNA-3751.1DNA methylation of miRNA-375in GC The positive rate of DNA methylation of miRNA-375gene was significantly higher in GC group(62.96%) than that in control group (22.22%)(P<0.05).1.2The relationship between DNA methylation of miRNA-375and the clinicopathologic features in GC The positive rate of DNA methylation of miRNA-375gene was significantly lower in well-differentiated and moderately-differentiated carcinoma group(44.44%) than that in poorly-differentiated carcinoma group(72.22%)(P<0.05). There were no statistical significant differences of the positive rate of DNA methylation of miRNA-375gene between different groups of age,sex,lymphatic metastasis and clinical stages (P>0.05).2The expression of miRNA-375gene2.1The expression of miRNA-375gene in GC The expression of miRNA-375gene in GC group was significantly lower compared with control group(P<0.05).2.2The relationship between the expression of miRNA-375gene and the clinicopathologic features in GC The expressions of miRNA-375gene in well-differentiated and moderately-differentiated carcinoma group was significantly higher than poorly-differentiated carcinoma group(P<0.05). There were no statistical significant differences of the expressions of miRNA-375gene between different groups of age,sex,lymphatic metastasis and clinical stages (P>0.05).3Bioinformatic studies indicates that SP1、AHR、GATA6�'�KLF4may the targets of miRNA-375.Conclusions:1We predict that the promoter of miRNA-375gene contains CpG islands by bioinformatic and confirm that the positive rate of DNA hypermethylation of miRNA-375gene was significantly higher in GC group than that in control group.The hypermethylation positivity of miRNA-375was correlated with pathological differentiation degree of GC.These results suggest that DNA hypermethylation of miRNA-375gene might be a useful molecular biomarker for early diagnosis and prognosis of GC.2The expression of miRNA-375gene was significantly decreased in GC group than in control group and correlated with pathological differentiation degree.The downregulation of miRNA-375,which is mainly caused by promoter methylation,is one of the crucial molecular mechanisms involved in the development and progression of GC.3miRNA-375may exert its function through the regulation of SP1、AHR、GATA6and KLF4in the development and progression of GC, providing the basis for the further study of miRNA-375in gastric cancer.