Structural shift of gut microbiota during chemopreventive effects of epigallocatechin gallate on colorectal carcinogenesis in mice

AIM To investigate the effect of epigallocatechin gallate(EGCG) on structural changes of gut microbiota in colorectal carcinogenesis.METHODS An azoxymethane(AOM)/dextran sodium sulfate(DSS)-induced colitis mouse model was established. Fortytwo female FVB/N mice were randomly divided into the following three groups: group 1(10 mice, negative control) was treated with vehicle, group 2(16 mice, positive control) was treated with AOM plus vehicle, and group 3(16 mice, EG) was treated with AOM plus EGCG. For aberrant crypt foci(ACF) evaluation, the colons were rapidly took out after sacrifice, rinsed with saline, opened longitudinally, laid flat on a polystyrene board, and fixed with 10% buffered formaldehyde solution before being stained with 0.2% methylene blue in saline. For tumor evaluation, the colon was macroscopically inspected and photographed, then the total number of tumors was enumerated and tumor size measured. For histological examination, the fixed tissues were paraffin-embedded and sectioned at 5 mm thickness. Microbial genomic DNA was extracted from fecal and intestinal content samples using a commercial kit. The V4 hypervariable regions of 16 S r RNA were PCR-amplified with the barcoded fusion primers. Using the best hit classification option, the sequences from each sample were aligned to the RDP 16 S r RNA training set to classify the taxonomic abundance in QIIME. Statistical analyses were then performed.RESULTS Treatment of mice with 1% EGCG caused a significant decrease in the mean number of ACF per mouse, when compared with the model mice treated with AOM/DSS(5.38 ± 4.24 vs 13.13 ± 3.02, P < 0.01). Compared with the positive control group, 1% EGCG treatment dependently decreased tumor load per mouse by 85%(33.96 ± 6.10 vs 2.96 ± 2.86, respectively, P < 0.01). All revealed that EGCG could inhibit colon carcinogenesis by decreasing the number of precancerous lesions as well as solid tumors, with reduced tumor load and delayed histological progression of CRC. During the cancerization, the diversity of gut microbiota increased, potential carcinogenic bacteria such as Bacteroides were enriched, and the abundance of butyrate-producing bacteria(Clostridiaceae, Ruminococcus, etc.) decreased continuously. In contrast, the structure of gut microbiota was relatively stable during the intervention of EGCG on colon carcinogenesis. Enrichment of probiotics(Bifidobacterium, Lactobacillu, etc.) might be a potential mechanism for EGCG's effects on tumor suppression. Via bioinformatics analysis, principal coordinate analysis and cluster analysis of the tumor formation process, we found that the diversity of gut microbiota increased in the tumor model group while that in the EGCG interfered group(EG) remained relatively stable.CONCLUSION Gut microbiota imbalance might be a potential mechanism for the prevention of malignant transformation by EGCG, which is significant for diagnosis, treatment, prognosis evaluation, and prevention of colorectal cancer.

Glucagon-like peptide-2 protects impaired intestinal mucosal barriers in obstructive jaundice rats

AIM: To observe the protective effect of glucagon-like peptide-2(GLP-2) on the intestinal barrier of rats with obstructive jaundice and determine the possible mechanisms of action involved in the protective effect.METHODS: Thirty-six Sprague-Dawley rats were randomly divided into a sham operation group, an obstructive jaundice group, and a GLP-2 group; each group consisted of 12 rats. The GLP-2 group was treated with GLP-2 after the day of surgery, whereas the other two groups were treated with the same concentration of normal saline. Alanine aminotransferase(ALT), total bilirubin, and endotoxin levels were recorded at 1, 3, 7, 10 and 14 d. Furthermore, on the 14 th day, body weight, the wet weight of the small intestine, pathological changes of the small intestine and the immunoglobulin A(Ig A) expressed by plasma cells located in the small intestinal lamina propria were recorded for each group.RESULTS: In the rat model, jaundice was obvious, and the rats' activity decreased 4-6 d post bile duct ligation. Compared with the sham operation group, the obstructive jaundice group displayed increased yellow staining of abdominal visceral serosa, decreased small intestine wet weight, thinning of the intestinal muscle layer and villi, villous atrophy, uneven height, fusion, partial villous epithelial cell shedding, substantial inflammatory cell infiltration and significantly reduced Ig A expression. However, no significant gross changes were noted between the GLP-2 and sham groups. With time, the levels of ALT, endotoxin and bilirubin in the GLP-2 group were significantly increased compared with the sham group(P < 0.01). The increasing levels of the aforementioned markers were more significant in the obstructive jaundice group than in the GLP-2 group(P < 0.01).CONCLUSION: GLP-2 reduces intestinal mucosal injuries in obstructive jaundice rats, which might be attributed to increased intestinal Ig A and reduced bilirubin and endotoxin.

Suppression of colorectal tumorigenesis by recombinant Bacteroides fragilis enterotoxin-2 in vivo

AIM To evaluate the impact of recombinant Bacteroides fragilis enterotoxin-2 (BFT-2, or Fragilysin) on colorectal tumorigenesis in mice induced by azoxymethane/dextran sulfate sodium (AOM/DSS). METHODS Recombinant proBFT-2 was expressed in Escherichia coli strain Rosetta (DE3) and BFT-2 was obtained and tested for its biological activity via colorectal adenocarcinoma cell strains SW-480. Seventy C57BL/6J mice were randomly divided into a blank (BC; n = 10), model (AD; n = 20), model + low-dose toxin (ADLT; n = 20, 10 mu g), and a model + high-dose toxin (ADHT; n = 20, 20 mu g) group. Mice weight, tumor formation and pathology were analyzed. Immunohistochemistry determined Ki-67 and Caspase-3 expression in normal and tumor tissues of colorectal mucosa. RESULTS Recombinant BFT-2 was successfully obtained, along with its biological activity. The most obvious weight loss occurred in the AD group compared with the ADLT group (21.82 +/- 0.68 vs 23.23 +/- 0.91, P < 0.05) and the ADHT group (21.82 +/- 0.68 vs 23.57 +/- 1.06, P < 0.05). More tumors were found in the AD group than in the ADLT and ADHT groups (19.75 +/- 3.30 vs 6.50 +/- 1.73, P < 0.05; 19.75 +/- 3.30 vs 6.00 +/- 2.16, P < 0.05). Pathology showed that 12 mice had adenocarcinoma and 6 cases had adenoma in the AD group. Five mice had adenocarcinoma and 15 had adenoma in the ADLT group. Four mice had adenocarcinoma and 16 had adenoma in the ADHT group. The incidence of colorectal adenocarcinoma in both the ADHT group and the ADHT group was reduced compared to that in the AD group (P < 0.05, P < 0.05). The positive rate of Ki-67 in the ADLT group and the ADHT group was 50% and 40%, respectively, both of which were lower than that found in the AD group (94.44%, P < 0.05, P < 0.05). Caspase-3 expression in the ADLT group and the ADHT group was 45% and 55%, both of which were higher than that found in the BC group (16.67%, P < 0.05, P < 0.05). CONCLUSION Oral administration with lower-dose biologically active recombinant BFT-2 inhibited colorectal tumorigenesis in mice.

Transanal minimally invasive surgery vs endoscopic mucosal resection for rectal benign tumors and rectal carcinoids: A retrospective analysis

BACKGROUND Transanal minimally invasive surgery(TAMIS)is a good choice for resection of rectal neoplasms.Endoscopic mucosal resection(EMR)is also widely used in the treatment of benign rectal tumors such as rectal polyps and rectal adenomas.However,no studies have compared the outcome of TAMIS and EMR.AIM To compare the short-term outcomes after TAMIS and EMR for rectal carcinoid and benign tumors(including rectal polyps and adenomas).METHODS From January 2014 to January 2019,44 patients who received TAMIS and 53 patients who received EMR at The Fifth People's Hospital of Shanghai were selected.Primary outcomes(surgical-related)were operating time,blood loss,length of postoperative hospital stay,rate of resection margin involvement and lesion fragmentation rate.The secondary outcomes were complications such as hemorrhage,urinary retention,postoperative infection and reoperation.RESULTS No significant differences were observed in terms of blood loss(12.48±8.00 mL for TAMIS vs 11.45±7.82 mL for EMR,P=0.527)and length of postoperative hospital stay(3.50±1.87 d for TAMIS vs 2.72±1.98 d for EMR,P=0.065)between the two groups.Operating time was significantly shorter for EMR compared with TAMIS(21.19±9.49 min vs 49.95±15.28 min,P=0.001).The lesion fragmentation rate in the EMR group was 22.6%(12/53)and was significantly higher than that(0%,0/44)in the TAMIS group(P=0.001).TAMIS was associated with a higher urinary retention rate(13.6%,6/44 vs 1.9%,1/53 P=0.026)and lower hemorrhage rate(0%,0/44 vs 18.9%,10/53 P=0.002).A significantly higher reoperation rate was observed in the EMR group(9.4%,5/53 vs 0%,0/44 P=0.036).

Evaluation of specific fecal protein biochips for the diagnosis of colorectal cancer

AIM: To develop and initially test a potential fecal protein biochip for the screening of colorectal cancer (CRC).