Consistency Study On APC Gene Mutation In Colorectal Cancer Tissue And Exfoliated Cells In Stool

Background Colorectal cancer is one of the common gastrointestinal cancer, seriousthreat to human life and health. As the insidious onset of colorectal cancer, early, oftenwithout obvious symptoms, once symptoms appear, is the most advanced. Survival rateof patients with colorectal cancer is directly related to the degree of progression of thedisease at diagnosis related. foci in patients with colorectal cancer confined to theintestinal wall (A or B of period), five-year survival rate of>75%. when there is lymphnode metastasis, the five-year survival rate of patients dropped to30%-60%. Therefore,effective early diagnosis of colorectal cancer screening, can greatly improve the survivalrate of patients and reduce mortality. Fecal occult blood test is far the most commonscreening methods, but the low specificity, and easily affected by food. The developmentof colorectal cancer is the affected by of a multi-gene, multi-stage, multi-step complexprocess regulation, This process is often associated with cell proliferation, apoptosisuncontrolled related, involving the activation of oncogenes, tumor suppressor geneinactivation, the mismatch repair genes and change some of the modified gene. Changes incertain genes just at certain stages of colorectal cancer occur with high frequencies,resulting in incidence of colorectal cancer. Which involves associated with colorectalcancer have APC, MMR, DCC, P53tumor suppressor gene and K-ras, C-mycproto-oncogene mutations. APC gene is the susceptibility genes of familial adenomatouspolyposis (familial adenomatous polyposis, FAP), the early molecular events occurringcolorectal cancer, but the stability in the whole process of tumor development. Recentstudies show that APC gene in85%of colon cancer is deletion or inactivation, Andthe deletion of the gene is closely related to the genetic susceptibility of colon cancer.Studies have shown that stool and tissue APC gene combined detection have high specificity to colorectal cancer screening and diagnosis of high-risk populations andavoided pain endoscopic examination. This research project intends to use the proteintruncation technology (PTT) to detect APC gene mutations of cancer tissue and exfoliatedcells in stool of patients with sporadic colorectal, to explore the feasibility of stool genedetection instead of tissue.Objictive Utilization the protein truncation test (PTT) combined detection of APCgene mutations of cancer tissue and exfoliated cells in stool of patients with sporadiccolorectal,and to explore its role in colorectal cancer screening and establish the feasibilityof non-invasive screening method for colorectal cancer, thereby explore the earlydiagnosis of colorectal cancer both cost-effective and efficient screening methods.Method1. October2011to October2012,50patients with colorectal cancer wereselected at Ningxia medical university general hospital, these patients had been come fromthe clinic by colonoscopy and pathologically and then had been surgical resection anddiagnosed by colonoscopy as sporadic colorectal cancer,collected the patients stool3-5g, asmall amount of cancer tissue（Greater than1g）,30cases normal population had beendiagnosed by gastrointestinal endoscopy, Imaging,experimental and physicalexamination,collected the people’s stool3-5g, a small amount of intestinal tissue（Greaterthan1g）,all these were stored at-80℃. Amplification of the target DNA.2.The proteintruncation test was used to analyze the fifteenth exon mutations of APC gene of tissuesand exfoliated cells in stools of fifty cases of sporadic colorectol cancer and thirty casesnormal population；3. For the detection of gene mutations of stool and cancer tissue werestatistically analyzed,and to explore the positive rate of patients with sporadic colorectalcancer tissues and stool APC gene mutation in exon15of the presence or absence ofdifferences.Rusult1.The success rate of amplification the target gene was100%(50/50)Using tissue extracted DNA as template and was86%(43/50) extracted with stool DNA astemplate.2.Application the digital PTT technology with fluorescently labeled detect thefifteenth exon truncated mutations of APC gene of50tumor tissue,17cases were detectionin and the mutation rate was34%（17/50）(primers15A mutations detected in four cases, primers15B mutations detected in seven cases, primers15C mutations detected in twocases, primers15D mutations detected in four cases); And detect the fifteenth exontruncated mutations of APC gene of50exfoliated cells in stool,14cases were detection inand the mutation rate was28%（14/43）(primers15A mutations detected in two cases,primers15B mutations detected in six cases, primers15C mutations detected in two cases,primers15D detected four cases). The cancer tissue and13cases of corresponding stoolwere positive.3.Application the digital PTT technology with fluorescently labeled detectthe fifteenth exon truncated mutations of APC gene of30cases normal colon tissue andexfoliated cells in stool，there were no truncated mutations.4.there was no differencebetween the positive rate of tumor tissue and exfoliated cells in stool by chi-squaretest(P>0.05). Kappa value of0.749.Conclusion1. Detected the mutation of APC gene in stool is feasible of earlyscreening for sporadic colorectal cancer.2.To detect APC gene in colorectal cancer tissueand exfoliative cells in stool are better consistency,as providing the feasibility basis forAPC gene testing is substitute for cancer tissue.3.Protein truncation test (PTT) has certainadvantages in detecting the mutation of APC gene which has been caused frameshiftmutation in deletion or insertion of long fragment peptide chain.