Analysis Of Methylation Of MiR34b/c Gene In Colorectal Cancer And Its Significance In Early Diagnosis

BackgroudBecause of the development of our country’s economy, the progress of the society, theimprovement of people’s living standards, lifestyle change, and population aging, thecause of death spectrum of our population has changed a lot. The tumor is a major threatto human health. The new cases of colorectal cancer in the whole world accounted for9.4%of all cancer in2002, incidence of male has become the fourth, women third.Investigation to one over ten of the population in2005found increased incidence ofcolorectal cancer patients with an annual increasing rate of3.9%, while the world averagejust2%. According to incomplete statistics, China’s colorectal cancer incidence andmortality in2005are respectively172000and99000, more than the United States[1].Inrecent years, studies have found that the colorectal cancer incidence in the westerndeveloped countries have a downward trend, it means this has a closely link to the early diagnosis of cancer and cancer prevention. There are no symptoms of early colorectalcancer, only5%is diagnosed in the early,60-70%is diagnosed in the middle or late,colorectal cancer radical surgery in the5-year survival rate is only50.21%, thepostoperative recurrence rate is30%[2]. Therefore, early diagnosis is the key to improveclinical cure rate. However, there is no ideal early screening or non-invasive means todiagnosis of colorectal cancer until now. Studies in recent years have shown that miRNAsare widely participating in malignant tumor occurrence and development through theregulation of multiple genes, the studies also find that about50%of miRNAs in genomeCpG sequence are apparent genetic silence of the important targets. Preliminary studyshowed that miR34b/c in colorectal cancer had high frequency of abnormal methylation, itwas an important molecular characteristics of colorectal cancer. Colorectal cancer cells orthe secretion of free DNA fallen off through the waste discharge in vitro, stool DNA alsohad a higher proportion of tumor DNA. Therefore, detection of fecal miR34b/c genemethylation may become new biomarkers of colorectal cancer in early diagnosis orscreening. In this paper, the author adopted multiple displacement amplificationtechnology joint methylation-specific PCR analysis of126colorectal cancer patients’stools miR-34b/c gene methylation state, in order to explore the application value in earlydiagnosis of colorectal cancer.Aim:Explore the values of methylation of miR34b/c gene in diagnosis of colorectalcancer.Methods:Multiple displacement amplification (MDA) was apply to make amplification ofbisulfite modified genomic DNA; Methylation-specific PCR (MSP) was used to analyzemethylation of miR34b/c in126colorectal cancers tissues, stools DNA and stools DNA in64patients with benign disease.Results:1、In126cancer tissues and their para-cancer tissues,95.2%(120/126) and11.9%(15/126) of methylation of miR34b/c were found respectively and there are a significant difference between them (P<0.01).2、The methylaton of miR34b/c was90.2%(111/123) in stool DNA from cancerpatients and was7.8%(5/64) in stool DNA from patients with benign disease, and thereare also a significant difference between them (P<0.01). Sensitivity and specifity ofdiagnosis by methylation of miR34b/c was90.2%and92.2%respectively.3、There are no difference between mehylation of miR34b/c and clinical pathologicparameters (P>0.05).Conclusion:MiR34b/c methylation is an important molecular characteristic of colorectal cancer; itmay be as a novel bio-marker in diagnosis of colorectal cancer, multiple displacementamplification combined with methylation specific PCR provides an ideal means to thestudy of small RNA methylation analysis.