Tackling the Threat of Cancer Due to Pathobionts Producing Colibactin: Is Mesalamine the Magic Bullet?

Effects of Mesalamine Combined with Live Combined Bifidobacterium, Lactobacillus and Enterococcus Capsules on Intestinal Mucosa Barrier Function and Intestinal Microbiota in Mildly Active Crohn's Disease Patients

Objective: This study is aimed at investigating the impact of mesalamine combined with Live combined Bifidobacterium, Lactobacillus and Enterococcus capsules on intestinal mucosa barrier function and intestinal microbiota in mildly active Crohn's disease patients.Methods: Ninety-six Crohn's disease patients in mild activity period were randomized into the control group (treated with mesalamine) and the observation group (treated with mesalamine combined with Live combined Bifidobacterium, Lactobacillus and Enterococcus capsules) (n = 48). After 4 wk of treatment, the patients were evaluated for their clinical efficacy. Intestinal microbiota counts, serum inflammatory factors, T lymphocyte subsets, and mucosal barrier function indicators in both groups were assessed.Results: After 4 wk of treatment, the total clinical effective rate of the observation group was higher than that of the control group. The number of Lactobacillus acidophilus (L. acidophilus) and Bifidobacterium Longum (B. longum) in the intestinal tract, serum IL-10 levels, and peripheral blood CD4+ and CD4+/CD8+ levels were higher, and the number of Bacteroides vulgatus (B. vulgatus), the levels of TNF-α, IL-6, CRP, CD8+, ET, D-lactate, DAO, and urine L/M ratio were lower in the observation group in comparison to those in the control group (all p < 0.05).Conclusion: Mesalamine combined with Live combined Bifidobacterium, Lactobacillus and Enterococcus capsules are more effective in treating mildly active Crohn's disease.

Metabolic Interaction Between Host and the Gut Microbiota During High-Fat Diet-Induced Colorectal Cancer

Colorectal cancer (CRC) is the second-highest cause of cancer-associated mortality among both men and women worldwide. One of the risk factors for CRC is obesity, which is correlated with a high-fat diet prevalent in Western dietary habits. The association between an obesogenic high-fat diet and CRC has been established for several decades; however, the mechanisms by which a high-fat diet increases the risk of CRC remain unclear. Recent studies indicate that gut microbiota strongly influence the pathogenesis of both high-fat diet-induced obesity and CRC. The gut microbiota is composed of hundreds of bacterial species, some of which are implicated in CRC. In particular, the expansion of facultative anaerobic Enterobacteriaceae, which is considered a microbial signature of intestinal microbiota functional imbalance (dysbiosis), is associated with both high-fat diet-induced obesity and CRC. Here, we review the interaction between the gut microbiome and its metabolic byproducts in the context of colorectal cancer (CRC) during high-fat diet-induced obesity. In addition, we will cover how a high-fat diet can drive the expansion of genotoxin-producing Escherichia coli by altering intestinal epithelial cell metabolism during gut inflammation conditions.

Current understandings of colibactin regulation

The biosynthetic machinery for the production of colibactin is encoded by 19 genes (clbA - S) within the pks pathogenicity island harboured by many E. coli of the B2-phylogroup. Colibactin is a potent genotoxic metabolite which causes DNA-damage and which has potential roles in microbial competition and fitness of pks+ bacteria. Colibactin has also been strongly implicated in the development of colorectal cancer. Given the genotoxicity of colibactin and the metabolic cost of its synthesis, the regulatory system governing the clb cluster is accordingly highly complex, and many of the mechanisms remain to be elucidated. In this review we summarise the current understanding of regulation of colibactin biosynthesis by internal molecular components and how these factors are modulated by signals from the external environment.

The role of gut microbiota and drug interactions in the development of colorectal cancer

The human gut microbiota is a complex ecosystem regulating the host's environmental interaction. The same functional food or drug may have varying bioavailability and distinct effects on different individuals. Drugs such as antibiotics can alter the intestinal flora, thus affecting health. However, the relationship between intestinal flora and non-antibiotic drugs is bidirectional: it is not only affected by drugs; nevertheless, it can alter the drug structure through enzymes and change the bioavailability, biological activity, or toxicity of drugs to improve their efficacy and safety. This review summarizes the roles and mechanisms of antibiotics, antihypertensive drugs, nonsteroidal anti-inflammatory drugs, lipid-lowering drugs, hypoglycemic drugs, virus-associated therapies, metabolites, and dietary in modulating the colorectal cancer gut microbiota. It provides a reference for future antitumor therapy targeting intestinal microorganisms.

The pks island: a bacterial Swiss army knife? Colibactin: beyond DNA damage and cancer

The structure and mode of action of colibactin with its potential involvement in cancer have been extensively studied but little is known about the intrinsic function of the biosynthetic gene cluster, coding for colibactin, as a bacterial genotoxin. Paradoxically, this pathogenicity island is also found in commensal and probiotic strains of Escherichia coli and in bacterial species colonizing olive trees and the digestive tract of bees. In this review, we summarize the available literature to address the following key questions. What does this genomic island really encode? What explains the extensive dissemination of this genetically mobile element? What do we really know about the biosynthetic and secretory pathways of colibactin? What is its inherent target/function?