| Colorectal Cancer(CRC)is one of the most common malignant tumors,and the incidence of colorectal cancer is increasing year by year.Among them,colitis related colon cancer(Colitis Associated Cancer,CAC)is one of the common clinical colorectal cancer.Surgery combined with chemotherapy and radiotherapy is the mainly method for the treatment of colon cancer.However,most of the chemotherapeutic drugs have a large side effect,and the tumor is susceptible to tolerance.Therefore,it is necessary to find novel,effective and lower toxic drugs in the treatment of colon cancer.Extracellular polysaccharide(Exopolysaccharidesl-1,EPS1-1)is extracted from the fermentation broth of Rhizopus nigricans.The molecular weight is 9682Da,mainly connected with 1,6-Glcp linkage.Previous studies showed that EPS 1-1 promoted the apoptosis of colon cancer HCT-116 cells,and significantly inhibited the growth of tumor bearing S180 tumor and CT26 tumor mice and alleviating chronic atrophic gastritis.In this study,a mouse model of colitis associated cancer was established to study the effect of EPS 1-1 on colon cancer.CAC mouse model was established using azoxymethane(AOM)combined with dextran sodium sulfate(DSS).In the model group,the pathological symptoms of weight loss,piloerection,hematochezia and insensitivity appeared at the third week.After forming the mouse model,the mice were executed and dissected at thirteenth weeks.In the model group,the survival rate in model group is 75.0%and the colon tissues were shortened and the gastric tissue were expanded.The tumor rate of colorectal cancer was 100%,the number of tumors was 11.07±3.45 and the diameter of the tumor of more than 3mm was 30.87%.The histological section result showed the proliferated glands of the colon epithelial cells,disorganized structure,disappeared recess and mucous layer,deeply stained nucleus and the highly ratio of nuclear to cytoplasm and dense inflammatory infilt.However,the mice in the EPS 1-1 treated group only developed mild pathological symptoms at fifth weeks.EPS 1-1 maintained normal colonic length and gastric tissue structure,and reduced the number and size of colon tumors.The colonic structure was relatively complete and the survival rate was 35.7%higher than that in the model group.These results indicated that EPS1-1 significantly inhibited the occurrence and development of AOM/DSS induced colitis associated colon cancer.Further studies indicated that the early indicator of colon cancer-COX-2 showed diffuse expression in the colon tissue of the model group as compared with the control group.Wnt signaling pathway is an important signaling pathway in the development and progression of colon cancer.The key protein p-catenin of Wnt signaling pathway and the expression of CyclinD1 and C-Myc were significantly up-regulated in the model group.But EPS 1-1 significantly decreased the expression level of COX-2 and three key proteins of Wnt signaling pathways.The occurrence of cancer is a complex and changeable process,including changes in physiological processes such as malignant proliferation and apoptosis.The number of positive cells of Ki-67 and PCNA in colon tissue were increased significantly in the model group.TUNEL results showed that the number of apoptotic cells in the model group was less than 2.03%,while the number of apoptotic cells in the EPS 1-1 group was 11.4 times than the model group.Therefore,EPS 1-1 significantly increased the expression of the activated Caspase-3 and the mRNA transcriptional level of apoptotic genes P53 and Bax,and down regulated the anti-apoptotic protein Bcl-2.These results suggested that EPS 1-1 may inhibit the proliferation of colon cancer cells and promote the apoptosis of colon cancer cells through Wnt signaling pathway.CD68 and F4/80 macrophages could be activated under the stimulation of proinflammatory cell division and then produce complex network reactions,thus affecting the occurrence of colon cancer.Immunohistochemical detection showed that the CD68+ and F4/80+ macrophage were infiltrated in the colon tumor tissue of the model group,but the number of positive cells decreased significantly in the colon tissue of EPS1-1 group.EPS1-1 also inhibited the expression of NF-κB,and reduced the levels of its regulatory inflammatory cytokines in colon tumor tissues.In addition,the results of immune organ indicators-thymus and spleen indices and blood routine test showed that EPS 1-1 increased the spleen and thymus index,reduced the number of leukocytes and platelets in the blood of colon cancer mice,and increased the number of red blood cells and hemoglobin,which indicats EPS 1-1 reduced the risk of infection and inflammation in mice and improved the function of the immune system in mice.In conclusion,EPS 1-1 inhibits the expression of key genes and proteins in the Wnt signaling pathway,reduces the proliferation of colon cancer cells and promotes the apoptosis of colon cancer cells,thus significantly inhibits the occurrence and development of colon cancer. |
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