Mechanism Of Cellulose Inhibiting Intestinal Adenoma In Apc^min/+ Colorectal Cancer Mice

Objective:Apc ^min/+mice are commonly used as models of colorectal cancer and can develop multiple intestinal adenomas spontaneously,we feed them diets containing different specifications of cellulose to investigate the changes of intestinal microbiota,the expression of Wnt pathway related molecules,to analyze the possible mechanism of cellulose anti-colorectal tumor.Methods:1、The experimental groups:Ten C57BL/6J female mice were divided to control group（CG）,fed with standard AIN-93M,5%cellulose;forty Apc ^min/+mice were divided randomly according to weight into model group（MG）,fed with 0%cellulose AIN-93M;low dose cellulose group（LCEG）,fed with 2.5%cellulose AIN-93M;medium dose cellulose group（MCEG）,fed with standard AIN-93M,5%cellulose;high dose cellulose group（HCEG）,fed with 10%cellulose AIN-93M.AIN-93M feeds with different dose of cellulose were given after one week of adaptive feeding（standard AIN-93M,5%cellulose）.After 14weeks’feeding,mice were sacrificed and specimens were collected for the subsequent experiment.2、Specimen processing and testingIntestine:Mice were sacrificed and the small intestine and colorectum of mice were cut longitudinally,the number of adenomas was recorded and the adenoma inhibition rate was calculated;The small intestine was divided into the proximal segment near the stomach and the distal segment near the cecum;The adenoma tissue of the distal small intestine was used for HE staining,Western blotting was performed on the other adenoma tissues from the distal small intestine to observe the changes of Wnt pathway related molecularsβ-catenin,Cyclin D1 and c-myc.Stool:1g of mice feces（about 3-5 grains）was collected,respectively put into sterile EP tubes,flash-frozen in liquid nitrogen and immediately stored in-80℃refrigerator,and uniformly sent for 16S r DNA microbiota detection.Results:1、The adenoma inhibition rates of LCEG,MCEG,HCEG were 25.5%,55.3%and 77.7%,compared with CG,the LCEG,MCEG and HCEG had fewer small intestinal adenomas（p<0.05）,and the higher the cellulose content,the lower the number of intestinal adenomas,the less malignant the intestinal adenomas;2、Cellulose inhibited the Wnt pathway moleculesβ-catenin,cyclin D1,c-myc（1）Compared with CG,the expression levels of nucleusβ-catenin of the adenoma cells of MG,LCEG,MCEG increased（p<0.05）;Compared with MG,the expression levels of LCEG,MCEG,HCEG decreased（p<0.05）,compared with LCEG,the expression levels of MCEG,HCEG decreased（p<0.05）;（2）Compared with CG,the expression levels of cyclin D1 of the adenoma cells of MG,LCEG increased（p<0.05）;Compared with MG,the expression levels of LCEG,MCEG,HCEG decreased（p<0.05）,compared with LCEG,the expression levels of MCEG,HCEG decreased（p<0.05）;（3）Compared with CG,the expression levels of c-myc of the adenoma cells of MG,LCEG increased（p<0.05）;Compared with MG,the expression levels of LCEG,MCEG,HCEG decreased（p<0.05）,compared with LCEG,the expression levels of MCEG,HCEG decreased（p<0.05）,compared with MCEG,the expression levels of HCEG decreased（p<0.05）.3、Cellulose changed the gut microbiota（1）Compared with CG,the relative abundance of beneficial bacteria Ruminococcus in MG,LCEG,MCEG decreased（p<0.05）;the relative abundance in HCEG was higher than MG and LCEG（p<0.05）;（2）Compared with CG,the relative abundance of pathogenic bacteria Verrucomicrobia increased（p<0.05）;the abundance of MCEG,HCEG was lower than MG,LCEG（p<0.05）,the abundance of HCEG was lower than MCEG（p<0.05）;（3）Compared with CG,the relative abundance of pathogenic bacteria Clostridium,Akkermansia of MG,LCEG increased（p<0.05）;Compared with MG,LCEG,the abundance of MCEG,HCEG decreased（p<0.05）;（4）The higher the cellulose content,the closer the gut microbiota of Apc ^min/+mice to C57BL/6J normal mice;（5）There are obvious positive correlations between the abundance of pathogenic bacteria Verrucomicrobia,Clostridium,Akkermansia and the expression levels of nucleusβ-catenin,cyclin D1,c-myc（p<0.05）;Conclusion:Adding cellulose to food can reduce the number of intestinal adenomas and the malignancy of intestinal adenomas in Apc ^min/+colorectal cancer model mice,and its possible mechanism may be the inhibition of Wnt pathway activation;the decrease of the abundance of pathogenic bacteria and the increase of the abundance of beneficial bacteria so that the structure of gut microbiota get changed and get closer to the normal gut microbiota.