Intestinal toll-like receptor 4 knockout alters the functional capacity of the gut microbiome following irinotecan treatment

Targeting the gut microbiota: a new strategy for colorectal cancer treatment

BACKGROUND

How to reduce the high incidence rate and mortality of colorectal cancer (CRC) effectively is the focus of current research. Endoscopic treatment of early-stage CRC and colorectal adenomas (CAC) has a high success rate, but although several treatments are available for advanced CRC, such as surgery, radiotherapy, chemotherapy, and immunotherapy, the 5-year survival rate remains low. In view of the high incidence rate and mortality of CRC, early rational drug prevention for high-risk groups and exploration of alternative treatment modalities are particularly warranted. Gut microbiota is the target of and interacts with probiotics, prebiotics, aspirin, metformin, and various Chinese herbal medicines (CHMs) for the prevention of CRC. In addition, the anti-cancer mechanisms of probiotics differ widely among bacterial strains, and both bacterial strains and their derivatives and metabolites have been found to have anti-cancer effects. Gut microbiota plays a significant role in early drug prevention of CRC and treatment of CRC in its middle and late stages, targeting gut microbiota may be a new strategy for colorectal cancer treatment.

Is There an Interplay between Environmental Factors, Microbiota Imbalance, and Cancer Chemotherapy-Associated Intestinal Mucositis?

Interindividual variation in drug efficacy and toxicity is a significant problem, potentially leading to adverse clinical and economic public health outcomes. While pharmacogenetics and pharmacogenomics have long been considered the primary causes of such heterogeneous responses, pharmacomicrobiomics has recently gained attention. The microbiome, a community of microorganisms living in or on the human body, is a critical determinant of drug response and toxicity. Factors such as diet, lifestyle, exposure to xenobiotics, antibiotics use, illness, and genetics can influence the composition of the microbiota. Changes in the intestinal microbiota are particularly influential in drug responsiveness, especially in cancer chemotherapy. The microbiota can modulate an individual's response to a drug, affecting its bioavailability, clinical effect, and toxicity, affecting treatment outcomes and patient quality of life. For instance, the microbiota can convert drugs into active or toxic metabolites, influencing their efficacy and side effects. Alternatively, chemotherapy can also alter the microbiota, creating a bidirectional interplay. Probiotics have shown promise in modulating the microbiome and ameliorating chemotherapy side effects, highlighting the potential for microbiota-targeted interventions in improving cancer treatment outcomes. This opinion paper addresses how environmental factors and chemotherapy-induced dysbiosis impact cancer chemotherapy gastrointestinal toxicity.

Updated perspectives on the contribution of the microbiome to the pathogenesis of mucositis using the MASCC/ISOO framework

Advances in the treatment of cancer have significantly improved mortality rates; however, this has come at a cost, with many treatments still limited by their toxic side effects. Mucositis in both the mouth and gastrointestinal tract is common following many anti-cancer agents, manifesting as ulcerative lesions and associated symptoms throughout the alimentary tract. The pathogenesis of mucositis was first defined in 2004 by Sonis, and almost 20 years on, the model continues to be updated reflecting ongoing research initiatives and more sophisticated analytical techniques. The most recent update, published by the Multinational Association for Supportive Care in Cancer and the International Society for Oral Oncology (MASCC/ISOO), highlights the numerous co-occurring events that underpin mucositis development. Most notably, a role for the ecosystem of microorganisms that reside throughout the alimentary tract (the oral and gut microbiota) was explored, building on initial concepts proposed by Sonis. However, many questions remain regarding the true causal contribution of the microbiota and associated metabolome. This review aims to provide an overview of this rapidly evolving area, synthesizing current evidence on the microbiota's contribution to mucositis development and progression, highlighting (i) components of the 5-phase model where the microbiome may be involved, (ii) methodological challenges that have hindered advances in this area, and (iii) opportunities for intervention.

Could paraprobiotics be a safer alternative to probiotics for managing cancer chemotherapy-induced gastrointestinal toxicities?

Clinical oncology has shown outstanding progress improving patient survival due to the incorporation of new drugs. However, treatment success may be reduced by the emergency of dose-limiting side effects, such as intestinal mucositis and diarrhea. Mucositis and diarrhea management is symptomatic, and there is no preventive therapy. Bacterial and fungal-based compounds have been suggested as an alternative for preventing the development of diarrhea in cancer patients. Using probiotics is safe and effective in immunocompetent individuals, but concerns remain during immunosuppressive conditions. Paraprobiotics, formulations composed of non-viable microorganisms, have been proposed to overcome such limitation. The present literature review discusses current evidence regarding the possible use of paraprobiotics as an alternative to probiotics to prevent gastrointestinal toxicity of cancer chemotherapy.

Experimental Chemotherapy-Induced Mucositis: A Scoping Review Guiding the Design of Suitable Preclinical Models

Mucositis is a common and most debilitating complication associated with the cytotoxicity of chemotherapy. The condition affects the entire alimentary canal from the mouth to the anus and has a significant clinical and economic impact. Although oral and intestinal mucositis can occur concurrently in the same individual, these conditions are often studied independently using organ-specific models that do not mimic human disease. Hence, the purpose of this scoping review was to provide a comprehensive yet systematic overview of the animal models that are utilised in the study of chemotherapy-induced mucositis. A search of PubMed/MEDLINE and Scopus databases was conducted to identify all relevant studies. Multiple phases of filtering were conducted, including deduplication, title/abstract screening, full-text screening, and data extraction. Studies were reported according to the updated Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines. An inter-rater reliability test was conducted using Cohen's Kappa score. After title, abstract, and full-text screening, 251 articles met the inclusion criteria. Seven articles investigated both chemotherapy-induced intestinal and oral mucositis, 198 articles investigated chemotherapy-induced intestinal mucositis, and 46 studies investigated chemotherapy-induced oral mucositis. Among a total of 205 articles on chemotherapy-induced intestinal mucositis, 103 utilised 5-fluorouracil, 34 irinotecan, 16 platinum-based drugs, 33 methotrexate, and 32 other chemotherapeutic agents. Thirteen articles reported the use of a combination of 5-fluorouracil, irinotecan, platinum-based drugs, or methotrexate to induce intestinal mucositis. Among a total of 53 articles on chemotherapy-induced oral mucositis, 50 utilised 5-fluorouracil, 2 irinotecan, 2 methotrexate, 1 topotecan and 1 with other chemotherapeutic drugs. Three articles used a combination of these drugs to induce oral mucositis. Various animal models such as mice, rats, hamsters, piglets, rabbits, and zebrafish were used. The chemotherapeutic agents were introduced at various dosages via three routes of administration. Animals were mainly mice and rats. Unlike intestinal mucositis, most oral mucositis models combined mechanical or chemical irritation with chemotherapy. In conclusion, this extensive assessment of the literature revealed that there was a large variation among studies that reproduce oral and intestinal mucositis in animals. To assist with the design of a suitable preclinical model of chemotherapy-induced alimentary tract mucositis, animal types, routes of administration, dosages, and types of drugs were reported in this study. Further research is required to define an optimal protocol that improves the translatability of findings to humans.

Effects of a novel toll-like receptor 4 antagonist IAXO-102 in a murine model of chemotherapy-induced gastrointestinal toxicity

INTRODUCTION

Gastrointestinal mucositis (GIM) is a side effect of high-dose irinotecan (CPT-11), causing debilitating symptoms that are often poorly managed. The role of TLR4 in the development of GIM has been clearly demonstrated. We, therefore, aimed to investigate the potential of the TLR4 antagonist, IAXO-102, to attenuate gastrointestinal inflammation as well as supress tumour activity in a colorectal-tumour-bearing mouse model of GIM induced by CPT-11.

METHODS

24 C57BL/6 mice received a vehicle, daily i.p. IAXO-102 (3 mg/kg), i.p. CPT-11 (270 mg/kg) or a combination of CPT-11 and IAXO-102. GIM was assessed using validated toxicity markers. At 72 h, colon and tumour tissue were collected and examined for histopathological changes and RT-PCR for genes of interest; TLR4, MD-2, CD-14, MyD88, IL-6, IL-6R, CXCL2, CXCR1, and CXCR2.

RESULTS

IAXO-102 prevented diarrhoea in mice treated with CPT-11. Tumour volume in IAXO-102-treated mice was lower compared to vehicle at 48 h (P < 0.05). There were no differences observed in colon and tumour weights between the treatment groups. Mice who received the combination treatment had improved tissue injury score (P < 0.05) in the colon but did not show any improvements in cell proliferation or apoptotic rate. Expression of all genes was similar across all treatment groups in the tumour (P > 0.05). In the colon, there was a difference in transcript expression in vehicle vs. IAXO-102 (P < 0.05) and CPT-11 vs. combination (P < 0.01) in MD-2 and IL-6R, respectively.

CONCLUSION

IAXO-102 was able to attenuate symptomatic parameters of GIM induced by CPT-11 as well as reduce tissue injury in the colon. However, there was no effect on cell proliferation and apoptosis. As such, TLR4 activation plays a partial role in GIM development but further research is required to understand the specific inflammatory signals underpinning tissue-level changes.

Supporting the gastrointestinal microenvironment during high-dose chemotherapy and stem cell transplantation by inhibiting IL-1 signaling with anakinra

High-dose chemotherapy causes intestinal inflammation and subsequent breakdown of the mucosal barrier, permitting translocation of enteric pathogens, clinically manifesting as fever. Antibiotics are mainstay for controlling these complications, however, they are increasingly recognized for their detrimental effects, including antimicrobial resistance and dysbiosis. Here, we show that mucosal barrier injury induced by the mucotoxic chemotherapeutic agent, high-dose melphalan (HDM), is characterized by hyper-active IL-1b/CXCL1/neutrophil signaling. Inhibition of this pathway with IL-1RA, anakinra, minimized the duration and intensity of mucosal barrier injury and accompanying clinical symptoms, including diarrhea, weight loss and fever in rats. 16S analysis of fecal microbiome demonstrated a more stable composition in rats receiving anakinra, with reduced pathogen expansion. In parallel, we report through Phase IIA investigation that anakinra is safe in stem cell transplant patients with multiple myeloma after HDM. Ramping-up anakinra (100–300 mg administered intravenously for 15 days) did not cause any adverse events or dose limiting toxicities, nor did it change time to neutrophil recovery. Our results reinforce that strengthening the mucosal barrier may be an effective supportive care strategy to mitigate local and systemic clinical consequences of HDM. We are now conducting a Phase IIB multicenter, placebo-controlled, double-blinded trial to assess clinical efficacy of anakinra (AFFECT-2).

Trial registration: ClinicalTrials.gov identifier: NCT03233776.