Variation Of MUC1in The Process Of Colitis Associated Colon Carcinogenesis And The Effect Of Apple Polysaccharides On MUC1Expression

Objective: MUC1, a high molecular weight and high glycosylated transmembrane protein,highly expressed in tumor tissue, and is closely related to the occurrence, developmentand metastasis of tumor. MUC1as an important marker of tumor biology has drawn moreand more attention. In this study, apple polysaccharides were extractedfrom apple pomace,and colon cancer cell lines SW-1116, HT-29, and colitis-associated colon cancer micemodel were used to observe the effect of apple polysaccharide on MUC1and itspreventive effect on colitis carcinogenesis; study the changes of MUC1in colitiscarcinogenesis process, and provide a theoretical basis for MUC1as a potentialtherapeutic target for colitis associated colorectal cancer prevention.Methods: The methods of water extraction, ethanol precipitation, enzyme degradation, anddialysis were used to extract polysaccharides from pomace; Colon cancer cell lines SW-1116and HT-29, were treated with0.5mg/mL,1mg/mL apple polysaccharide (AP) for24and48h. Proteins were then extracted, and Western-blot was used to detect the MUC1expression. Carcinogenic agent azoxymethane (AOM) and proinflammatory agent dextransodium sulfate (DSS) were applied orderly to copy colitis associated colon cancer mousemodel. One hundred and fifty five-week-old male ICR mice were randomly divided intofive groups, namely, control group, model group,3dose of AP group (n=30). At thebeginning of the experiment, the control group mice were given saline only, and the restmice were injected intraperitoneally with a single dose of10mg/kg AOM. One week later,the mice were given2.5%(w/v) DSS in their drinking water for1week. This was followedby no further treatment for1week. After another week of2.5%DSS treatment, normalwater was given for an additional16week. On week7, the mice in AP-treated groups werethen maintained on the basal diets mixed with different concentrations of AP (1.25%,2.5%and5%w/w) for14weeks. In the3rd,6th,9th,15th and20th weeks, mice were randomlyselected from the normal and model and treatment group to kill, the remaining mice weresacrificed on week20by ether overdose and colon sample was then collected forhistopathological examinations and western-blot. All the processes were handling in icebath. Results: Apple polysaccharides with a sugar content of87.3%and molecular weight of50000-100000Da were obtained; After treatment with AP for24h and48h, MUC1in SW-1116and HT-29cells decreased in comparison with those in control group, especially at48h time point (P <0.05). H.E. staining showed that: in the20th week, adenocarcinoma and/or adenoma occurred in the colons of all the mice of the model group. AP administrationcontrolled the development of colon cancer to varying degrees;5%of AP reduced theincidence of colon tumors significantly. In the acute phase of inflammation,MUC1expression in colonic mucosa had no significant changes. However, when theinflammation developed and tumor formed, MUC1expression significantly increased (P<0.01). AP treatment (especially at the dose of5%) lowered down MUC1on protein level.Conclusion:Apple polysaccharide could prevent against colitis associated colon cancer in ICR miceeffectively.There were high level of MUC1expression in the ongoing process of colonic inflammation,and abnormally high expression of MUC1in tumor formation, suggesting the MUC1variation is closely related to colitis carcinogenesis process.Apple polysaccharide may prevent colitis associated colon carcinogenesis byregulatingMUC1expression.