The Study Of Enterococcus Feacails In Promoting The Tumorgenesis Of Colorectal Cancer And The Methodology Exploration Of PGEP In Clearing Intestinal Bacteria

BACKGROUND AND OBJECTIVEColorectal cancer is one of the most common malignant tumors of the digestive system,and its occurrence and development is a complex process regulated by multiple factors and carried out in multiple steps,and the imbalance of intestinal flora is an important cause.There are a large number of microorganisms in the human digestive tract,and the number,composition and biological activity of these microorganisms play an important role in maintaining human health or the occurrence and development of various diseases.A large number of existing studies have shown that intestinal flora disorder is closely related to colorectal cancer,and some studies have found that enterococcus faecials is highly enriched in the stool of patients with colorectal cancer,but its specific role and mechanism are still unclear.In the preparation of animal models related to intestinal flora and intestinal diseases,antibiotics are usually required to clear the intestinal bacteria to increase the colonization of the target bacteria.At the same time,microbes often cause mucosal damage and induce intestinal inflammation,which in turn affects the accuracy of the results.Therefore,looking for a modelling method that can effectively remove intestinal bacteria and avoid serious intestinal inflammation is an essential prerequisite for the study of intestinal flora,especially intestinal inflammation mediated by intestinal flora Broader application prospects in disease-related research.METHODS1.The study of enterococcus feacails in promoting the tumorgenesis of colorectal cancer in rats(1)Combined with the intragastric technique of Enterococcus faecalis/PBS solution,construct a model of DMH-induced colorectal cancer in rats,and observe the general condition of mice and changes in body weight during the modeling period;(2)At the end of the experiment,dissect and observe and compare the number and size of colorectal tumors in rats gavaged with Enterococcus faecalis/PBS solution,observe the histological morphology of the tumor by HE staining,and detect the expression of Ki-67 by immunohistochemical staining.2.The methodology exploration of PGEP to clear intestinal bacteria(1)Through the observation of the stool in rats,to explore the optimal dose and interval of intragastric PGEP as a condition for subsequent formal experiment grouping;(2)To use PBS solution/PGEP/antibiotics solution for gavage experiment treatment,through RT-qPCR detection,analyze the change of Ct value in bacteria which in the intestine of rats before and after gavage treatment in PBS solution/PGEP/antibiotics solution;(3)To use the above mouse model,observe the inflammation of mouse intestinal tissue after three different treatments under HE staining microscope.RESULT1.The study of enterococcus feacails in promoting the tumorgenesis of colorectal cancer in rats(1)Compared with the mice in the PBS solution gavage group,the rats in the Enterococcus faecalis gavage group had severe hair loss and prolapsed,and the rats in the Enterococcus faecalis gavage group at the end of the experiment had significantly lower body weight than the mice in the PBS gavage group(26.8±0.255g vs 28.3 ±0.165g,P<0.001);(2)Compared with the PBS solution gavage group,the rats with Enterococcus faecalis gavage group had more colorectal tumors(3.9±1.210 vs 1.9 ± 0.788,P<0.001)and the largest diameter(4.4 ± 0.883mm vs 2.368 ± 0.779mm,P<0.001);(3)HE section observation of PBS solution gavage group of mice colorectal adenoma is more common in low-grade intraepithelial neoplasia,but also high-grade intraepithelial neoplasia,but no clear intramucosal cancer.Colorectal adenoma in mice fed with Enterococcus faecalis was mostly accompanied by high-grade intraepithelial neoplasia,and some intramucosal carcinoma formation;and immunohistochemistry results showed that the positive rate of Ki67 in colorectal tumor tissue of Enterococcus faecalis gavage group was significantly higher than that of the control group(86.5 ± 4.74%vs 38±5.87%,P<0.001).2.The methodology exploration of PGEP to clear intestinal bacteria(1)With a single PGEP gavage capacity of 600ul,the frequency of once every 15min,continuous treatment for 2h,the stool of the rats was a pale yellow clear solution without stool,indicating that the intestine was completely cleaned;(2)The results of RT-qPCR showed that the Ct values of the total bacteria in the stool of the three groups of rats were(13.5575± 0.78 vs 13.5568±0.156 vs 13.4628± 0.242,F=0.381,P=0.691),and after different treatment,the increase of the Ct value of the intestinal flora in the antibiotic group was most apparent(13.4628±0.242 vs 20.8585 ± 0.317,P<0.001),followed by the PGEP group(13.5568 ± 0.156 vs 16.3214± 0.462,P<0.001),the Ct value of the PBS group was almost unchanged(13.5575± 0.78 vs 13.5935±0.187,P>0.05).;(3)HE section observation showed that after treatment with three different reagents,the intestinal tissue of the PBS treatment group and the PGEP treatment group showed no obvious inflammation reaction,while the intestinal tissue of the antibiotic treatment group showed obvious inflammationCONCLUSIONS1.Enterococcus faecalis can promote the occurrence and development of colorectal tumors in rats,and improve the ability to promote the proliferation of tumor cells;2.Compared with antibiotics to clear intestinal bacteria,the intestinal inflammation of mice after PGEP solution treatment is significantly reduced,and has a certain effect of bacteria removal.It has more application value in the research of intestinal inflammatory diseases.