| Objective:The Colorectal cancer is one of the most common cancer. The incidence rats of Colorectal cancer ranks the third place in the digestive tumors,some areas has risen to second place.With the improvement of our people's living standards,and the structure changes in dietary,the incidence groth of our country has been twice as much as the world average.Although the treatment such as radiotherapy and chemotherapy before and after surgery has had a positive effect,Five-year survival rate in advanced cancer is still not optimisitic.Diagnosis and treatment of the increasingly grim task requires health workers to be able to clear in early colorectal cancer diagnosis, then treat it.So we need an effective early screening methods to deal with delays in diagnosis and treatment of CRC,which can make the tumor at an early stage to be root.At present , for CRC diagnosis methods includ Colonoscop, Proctoscopy and Fecal occult blood test and so on,but none of them has good compliance,non-invasive,sesitivity and specificity of good features at the same time,so it maks our work of early diagnosis difficult to carry out.Statistics show that only about 10%-15% patients of CRC receive an eraly diagnosis and treament. In order to improve the survival rate five years or even decades,We have an urgent need to find a non-invasive, convenient and sensitive new method for early diagnosis. Detected the tumor-related DNA changes in stool provides a new idea for the early diagnosis of CRC. As an important complement to the mechanism of tumor,Epigenetic changes are more common than genetic alterations of gene expression and regulation mechanism. Detection of stool gene promoter methylation compared with detection of gene mutation results more satisfactory. WIF-1 gene encoding the WIF-1 protein which are secreted proteins,and there is no Cysteine-rich region is the different of secreted frizzled - related protein family. The WIF-1 protein and Wnt proteins have a strong affinity [1],so that it can competitively block the Wnt signal transduction. WIF-1 transcriptional inactivation and its promoter methylation frequency increased have closely related, and it also with the CRC caused by aberrant of Wnt pathway close. We speculate that WIF-1 promoter methylation can be used as a biomarker in stool DNA for the detection of CRC,then we test the WIF-1 promoter methylation of patient's stool and analysis it with the clinical case data. Evaluate the early diagnosis of cancer and precancerous lesion ,and summarize the result and experience of extracting DNA from the stool and PCR of the product.Methods:1 Stool from patients suffering from colorectal cancer who were admitted to Fourth Hospital of Hebei Medical University in the second department of general surgery and patients suffering from colorectal polyps or normal people who examine in endoscopic examination room during May 2007 to December 2008 were collected, and record the results of the final pathology.2 After stool DNA isolated by the stool DNA isolation kit and verify the existence of the human genome, MS-PCR(methylation-specific PCR)was applied to analyze the promoter hypermethylation of WIF-1 gene in the stool DNA.3 SPSS13.0 was applied to analyze the results of experiment.Results: Stool DNA were isolated from stool samles of 62 Patients and at last 49 samples Verify existence of the human genome and completed the MS-PCR, ineluding 27 Patienis with CRC and 14 Patienis with colorectal polyps and 8 patients without colorectal neoplasia. The WIF-1 gene promoter hypermethylation in CRC and colorectal polyps were 70.4%(19/27) and 50%(7/14)respectively, while the normal control group no methylation occurs, This method had a sensitivity of 70.4% and specifieity of 68.2% for detection CRC,and it had a sensitivity of 68.8% and specificity of 76.5% for detection cancer and advanced adenomas. The difference in hypermethylation Status of the WIF-1 gene promoter between the CRC and the control group statisticall significant (P=0.001P<0.05), There was also a significant difference between the colorectal polyps and the control groups(P=0.022 P<0.05). There was no significant difference between the CRC and the colorectal poly ps groups(P=0.306 P>0.05). .The promoter hype rmethylation of WIF-1gene didn't correlate with age,gender,tumor site,histological differentiation, Lylmphatic metastasis and TNM stage.Conclusions:We can get high success rate by using the stool DNA isolation kit, However, details of drawning and samples itself can still produce a significant impact on the quantity of stool DNA.The effect of MS-PCR after extraction of DNA and Sulfite modification is good ,illustrate the kit have a high capacity in removing inhibitor of stool. The stool DNA WIF-1 gene promoter hypermethylation test can provide high sensitivity for detection CRC and precancerous lesions,Which can be used as indicators for early diagnosis,but the specifieity is low. It can not distinguish carcinoma from adenoma very well. The WIF-1 gene promoter hypermethylation was not assoeiated with the clinicopathological characteristics of the CRC patients. (Including age,gender,tumorsite,histological differentiation lymphatic metastasis and TNM stage.) The detection of WIF-1 gene promoter hypermethylation in stool DNA is a Potential noninvasive screening method for CRCand deserves further research. |
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