Detection And Clinical Significance Of The Methylation P16and RASSF1A Gene In Colorectal Adenocarcinoma

Objective: The aim of the present study is the detection of methylation statusfor some tumor suppressor genes including P16and RASSF1A in colorectaladenocarcinoma, colorectal adenoma and normal formalin fixed paraffinembedded (FFPE) tissues and analyze the relationship between methylationstatus of those genes and clinical pathological features in order to evaluate thepossibility of developing molecular marker for early detection of colorectaladenocarcinoma. Methods:1. FFPE tissues were collected from96patients (41adenocarcinoma,30adenoma, and25normal tissues) in the Department ofPathology, the Affiliated Hospital of Luzhou Medical College during January2013to December2013.All patients have no history of chemotherapy,radiotherapy and all specimens were confirmed by pathology.2. FFPE DNA Kitwas used to extract genome DNA.3. The DNA was modified by sulfitemethods and then the methylation status of the promoter of P16and RASSF1Agenes was detected by nested methylation-specific PCR (nMSP).4. SPSS18.0was used to analysis analyze all of the dates. Results:1.The rates ofmethylation of the promoter of P16gene in colorectal adenocarcinoma group,colorectal adenoma group and normal group were58.54%（24/41）、36.67%（11/30）、4.00%（1/25），the difference was significant(χ2=19.721，P＜0.05).The rates of methylation of the promoter of P16gene in well differentiatedgrade, moderately differentiated grade and poorly differentiated grade were 31.25%（5/16）、73.68%（14/19）、83.33%（5/6）, the difference wassignificant(χ2=8.224，P＜0.05). The rates of methylation of P16gene was morefrequently found in tumors with lymph node metastasis than in thosewithout(80.00%vs41.15%, P＜0.05). The rates of methylation of P16gene wasno correlation with sexuality, age, the depth of invasion, tumor size and Dukesstaging in colorectal adenocarcinoma(P＞0.05).2. The rates of methylation ofthe promoter of RASSF1A gene in colorectal adenocarcinoma group, colorectaladenoma group and normal group were48.78%（20/41）、23.33%（7/30）、0%（0/25），the difference was significant(χ2=18.777，P＜0.05). The rates ofmethylation of the promoter of RASSF1A gene in well differentiated grade,moderately differentiated grade and poorly differentiated grade were31.25%（5/16）、57.89%（11/19）、66.67%（4/6）, the difference wassignificant(χ2=8.926，P＜0.05). The rates of methylation of RASSF1A genewas no correlation with sexuality, age, the depth of invasion, lymph nodemetastasis, tumor size and Dukes staging in colorectal adenocarcinoma(P＞0.05).3. The sperman correlation analysis indicated that there is no correlationbetween the methylation of the promoter of P16and RASSF1A gene.Conclusions:1.The methylation of the promoter of P16and RASSF1A genewere detected，and the method of nMSP is accurate, reliable and feasible.2. Therates of methylation of P16and RASSF1A gene in normal group, colorectaladenoma group and colorectal adenocarcinoma group were gradually increased,indicating that aberrant methylation of the P16and RASSF1A gene play a role in tumourigenesis and development of colorectal tumor.3. The methylation ofP16and RASSF1A gene were related to degree of differentiation, in addition,the methylation of P16were also related to lymph node metastasis, suggeststhat methylation of the P16may promote the invasion and metastasis ofcolorectal tumor.4. There was no relationship between the promotermethylation status of p16and RASSF1A genes, therefore, suggests that theymay be independent risk factors in tumourigenesis and development ofcolorectal adenocarcinoma.5. To detect the levels of the methylation of P16and RASSF1A gene may serve as a new method for early diagnosis ofcolorectal tumor.