Study On The Mechanism Of Ulcerative Colitis And The Risk Factors Of Colorectal Polyps

Background:Colorectal cancer is the third most common cancer worldwide, it accounts for the third cancer-related death in men and the second in women. Epidemiological studies have shown that patients with chronic inflammation are susceptible of tumorigenesis in various organs, chronic inflammation is associated with one fifth of human tumors.Ulcerative colitis is a kind of nonspecific chronic inflammation, mainly involving the mucosa of rectum and colon. The dominant symptoms in UC are abdominal pain, diarrhea, blood in stool and tenesmus, it follows a chronic intermittent course of more than ten years or even decades. One of its serious consequences is colorectal cancer, the risk of colorectal cancer in patients with UC is higher than the general population. Patients with long duration, extensive lesions, early onset, severe inflammation, false inflammatory polyp, PSC and family history of colorectal cancer are more likely to occur.The pathogenesis of UCRCC is different from sporadic colorectal cancer, the latter pathogenesis is relatively clear, mainly the colorectal cancer gene pathway proposed by Fearon and Vogelstein, in which a series of genetic mutations that lead to adenoma and eventually become cancer. In this model the initiate events are the genetic mutations occurred in sequence, one of the most important is APC gene mutation, which can lead to the activation of Wnt signaling pathway. Wnt signaling pathway also plays an important role in the process of UCRCC, but its activation is not due to the APC or K-ras gene mutations, its pathogenesis is still not clear.Objectives:In this paper we use the cytokines IL-6and TNF alpha, both of them play an important role in UC and CRC, we also choose the normal colonic epithelial cells and colon cancer cells, then we will observe the effect of above mentioned cytokines on beta-catenin, which is the key protein in Wnt signaling pathway, we want to explore the possible signaling pathways involved in cytokine events, and to verify the possible mechanism of UCRCC occurrence, that in UC various inflammatory factors may replace the classical genetic changes in colorectal cancer, lead to the occurrence and development of UCRCC.Methods:We chose the normal colonic epithelial cell CCD841CoN, the colon cancer cell HCT116, detected the beta-catenin expression levels in different cells by Western blot and real-time fluorescent quantitative PCR, then cytokines TNF alpha and IL-6acted on different cells, we observed their influences on beta-catenin expression in the transcription and translation level, used the Co-immunoprecipitation method to detect the beta-catenin combined with nuclear TCF4proteins and measured the beta-catenin/TCF4complex transcriptional activity by Dual luciferase reporter gene assay, measured the cell GSK3beta activity with colorimetry assay. In addition, we gave the specific inhibitors PD98059for MAPK or LY294002for PI3k signaling pathway before cytokines INF alpha and IL-6acted on cell respectively, and then repeated the above experiments.Results:1. The basic expression level of beta-catenin in various cell lines are different, the protein expression of beta-catenin in DLD-1, HCT116, SW480cells are higher, compared to the less expression in CCC-HIE-2, Lovo and HT29cell, and there is no expression observed in RKO and CCD841CoN. SW480cell also has the maximum beta-catenin mRNA expression, while HT29cell has the least, the beta-catenin mRNA expression levels are moderate in HCT116, DLD-1, Lovo, RKO and CCC-HIE-2;2. The optimal stimulation condition of IL-6and TNF alpha on HCT116action is, IL-650ng/ml work for6h, TNF alpha50ng/ml work for6h;3. IL-6and TNF alpha stimulated HCT116cell with the conditions recommended above, beta-catenin expression in both protein level and mRNA levels were significantly elevated;4. In HCT116cell, the upregulated beta-catenin due to the IL-6(50ng/ml,6h) and TNF alpha (50ng/ml,6h) stimulation most enter the nucleus, form complexes with TCF4;5. In HCT116cell, the upregulated beta-catenin/TCF4complexes due to the IL-6(50ng/ml,6h) and TNF alpha (50ng/ml,6h) stimulation can specifically activate the downstream genes transcription, enhanced the Wnt signaling pathways;6. The effect of IL-6can be blocked by LY294002(30umol/L,1h) and the effect of TNF alpha can be blocked by LY294002(30umol/L,1h) and PD98059(20umol/L,1h), and LY294002plays the main role.7. After IL-6(50ng/ml,6h) or TNF alpha (50ng/ml,6h) stimulation, the GSK3beta kinase activity of HCT116cell was decreased, and this can be partly blocked by LY294002(30umol/L,1h) or PD98059(20umol/L,1h).Conclusions:Cytokines IL-6or TNF alpha act on HCT116cell can increase beta-catenin expression in both protein level and mRNA level, and can partly inhibit the GSK3beta kinase activity, the process is mediated by PI3K and MAPK signaling pathway, and PI3K plays the main role. The elevated beta-catenin enter into the nucleus and form complexes with TCF4, can specifically upregulated the Wnt signaling pathways, lead to target genes transcription. This result suggests that inflammatory cytokines can activate the Wnt signaling pathway through a different way from sporadic CRC, and this can provide support for the mechanisms of ulcerative colitis carcinogenesis. Backgroud:Cobrectal cancer is one of the most common human malignancies, and has a high mortality rate. The western countries have proposed screening programs and promoted, as a results, colorectal cancer incidence and mortality showed a downward trend. But in China, with the improvement of living standards and westernized lifestyle, colorectal cancer incidence in our country is a upward trend. Based on the "adenoma-dysplasia-cancer" cancer model, we think that adenomatous us colorectal polyps in their precancerous lesions is very important. If adenomatous colorectal polyps are discovered and successfully removed, the incidence of colorectal cancer can be significantly reduced. Our countries have no screening programs, and the vast majority of patients are not regularly checked for colorectal.60%of CRC patients have been reached middle-advanced stage when examined. Therefore, through screening of the population, polyps, especially colorectal adenomatous polyps, can be discovered in early time, which is important of colorectal cancer prevention, treatment and prognosis.Objective:To investigate the risk factors that may associated with colorectal polyps, in order to provide evidence for the implementation of targeted clinical screening.Methods:We selected patients who underwent complete colonoscopy from Peking Union Medical College Hospital endoscopy center between June1,2012and May31,2013. These patients were divided into polyps group and normal control group. Each case undertook the same questionnaire about their general situation and endoscopic polyps performance. The data were statistical analysed by SAS9.2.Results:We received106colorectal polyps patients as polyps group and383normal persons composed control group. The single factor analysis show that the factors, including gender, age, family history of cancer, history of digestive system operation, intake of fruits and vegetables, intake of red meat, intake of preserved food, smoke and drink, are related to colorectal polyps. Analyses were performed by multivariate logistic regression analyses. Age (OR=1.343,95%CI:1.063-1.697), family history of cancer (OR=3.013,95%CI:1.675-5.419) and high proportion of red meat intake (OR=1.650,95%CI:1.085-2.509) are independent risk factors for colorectal polyps occurred.High proportion of fresh fruits and vegetables intake(OR=0.119,95%CI:0.076-0.188) are protective factors. Adenomatous polyps is easier to be detected in male than in female (P <0.05) and the proportion of patients with adenomatous polyps increased with age (P<0.05).Conclusions:Age, family history of cancer and high proportion of red meat intake are independent risk factors for colorectal polyps occurred, while high proportion of fresh fruits and vegetables intake are protective factors. Elderly male patients may have increase risk to occur adenomatous polyps. Risk factors questionnaire is useful in targeting for colorectal tumors screening.