Translational model of melphalan-induced gut toxicity reveals drug-host-microbe interactions that drive tissue injury and fever

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.

Gastrointestinal mucositis: a sign of a (systemic) inflammatory response

PURPOSE OF REVIEW

Gastrointestinal mucositis (GIM) is a significant complication of cancer therapy. Whilst inflammation is a central feature of GIM, studies attempting to mitigate mucosal damage via this mechanism are scarce. This review describes the relation between GIM, local and systemic inflammation, and the microbiome and its metabolites, and explores recent research on therapeutics that target this relationship.

RECENT FINDINGS

Recent literature underscores the pivotal role of inflammation in GIM, elucidating its bidirectional relation with disturbance of the gut microbiota composition and intestinal permeability. These events cause a heightened risk of bloodstream infections and lead to systemic inflammation. While studies investigating risk prediction models or therapeutics targeting GIM-related inflammation remain scarce, results have shown promise in finding biomarkers and alleviating GIM and its accompanying clinical symptoms.

SUMMARY

The findings underscore the important role of inflammation and the microbiome in GIM. Understanding the inflammatory pathways driving GIM is crucial for developing effective treatments. Further research is needed using genomics, epigenomics, and microbiomics to explore better risk prediction models or therapeutic strategies aimed at mitigating GIM-related inflammation.

Fibre-rich diet attenuates chemotherapy-related neuroinflammation in mice

The gastrointestinal microbiota has received increasing recognition as a key mediator of neurological conditions with neuroinflammatory features, through its production of the bioactive metabolites, short-chain fatty acids (SCFAs). Although neuroinflammation is a hallmark shared by the neuropsychological complications of chemotherapy (including cognitive impairment, fatigue and depression), the use of microbial-based therapeutics has not previously been studied in this setting. Therefore, we aimed to investigate the effect of a high fibre diet known to modulate the microbiota, and its associated metabolome, on neuroinflammation caused by the common chemotherapeutic agent 5-fluorouracil (5-FU). Twenty-four female C57Bl/6 mice were treated with 5-FU (400 mg/kg, intraperitoneal, i.p.) or vehicle control, with or without a high fibre diet (constituting amylose starch; 4.7 % crude fibre content), given one week prior to 5-FU and until study completion (16 days after 5-FU). Faecal pellets were collected longitudinally for 16S rRNA gene sequencing and terminal SCFA concentrations of the caecal contents were quantified using gas chromatography-mass spectrometry (GC-MS). Neuroinflammation was determined by immunofluorescent analysis of astrocyte density (GFAP). The high fibre diet significantly altered gut microbiota composition, increasing the abundance of Bacteroidaceae and Akkermansiaceae (p < 0.0001 and p = 0.0179) whilst increasing the production of propionate (p = 0.0097). In the context of 5-FU, the diet reduced GFAP expression in the CA1 region of the hippocampus (p < 0.0001) as well as the midbrain (p = 0.0216). Astrocyte density negatively correlated with propionate concentrations and the abundance of Bacteroidaceae and Akkermansiaceae, suggesting a relationship between neuroinflammatory and gastrointestinal markers in this model. This study provides the first evidence of the neuroprotective effects of fibre via dietary intake in alleviating the neuroimmune changes seen in response to systemically administered 5-FU, indicating that the microbiota-gut-brain axis is a targetable mediator to reduce the neurotoxic effects of chemotherapy treatment.

Review on the effect of chemotherapy on the intestinal barrier: Epithelial permeability, mucus and bacterial translocation

Chemotherapy kills fast-growing cells including gut stem cells. This affects all components of the physical and functional intestinal barrier, i.e., the mucus layer, epithelium, and immune system. This results in an altered intestinal permeability of toxic compounds (e.g., endotoxins) as well as luminal bacterial translocation into the mucosa and central circulation. However, there is uncertainty regarding the relative contributions of the different barrier components for the development of chemotherapy-induced gut toxicity. This review present an overview of the intestinal mucosal barrier determined with various types of molecular probes and methods, and how they are affected by chemotherapy based on reported rodent and human data. We conclude that there is overwhelming evidence that chemotherapy increases bacterial translocation, and that it affects the mucosal barrier by rendering the mucosa more permeable to large permeability probes. Chemotherapy also seems to impede the intestinal mucus barrier, even though this has been less clearly evaluated from a functional standpoint but certainly plays a role in bacteria translocation. Combined, it is however difficult to outline a clear temporal or succession between the different gastrointestinal events and barrier functions, especially as chemotherapy-induced neutropenia is also involved in intestinal immunological homeostasis and bacterial translocation. A thorough characterization of this would need to include a time dependent development of neutropenia, intestinal permeability, and bacterial translocation, ideally after a range of chemotherapeutics and dosing regimens.

Mucositis and Infection in Hematology Patients

Survival in patients with hematological malignancies has improved over the years, both due to major developments in anticancer treatment, as well as in supportive care. Nevertheless, important and debilitating complications of intensive treatment regimens still frequently occur, including mucositis, fever and bloodstream infections. Exploring potential interacting mechanisms and directed therapies to counteract mucosal barrier injury is of the utmost importance if we are to continue to improve care for this increasingly growing patient population. In this perspective, I highlight recent advances in our understanding of the relation of mucositis and infection.

Whey-based diet containing medium chain triglycerides modulates the gut microbiota and protects the intestinal mucosa from chemotherapy while maintaining therapy efficacy

Cytotoxicity (i.e. cell death) is the core mechanism by which chemotherapy induces its anti-cancer effects. Unfortunately, this same mechanism underpins the collateral damage it causes to healthy tissues. The gastrointestinal tract is highly susceptible to chemotherapy's cytotoxicity, resulting in ulcerative lesions (termed gastrointestinal mucositis, GI-M) that impair the functional capacity of the gut leading to diarrhea, anorexia, malnutrition and weight loss, which negatively impact physical/psychological wellbeing and treatment adherence. Preventing these side effects has proven challenging given the overlapping mechanisms that dictate chemotherapy efficacy and toxicity. Here, we report on a novel dietary intervention that, due to its localized gastrointestinal effects, is able to protect the intestinal mucosal from unwanted toxicity without impairing the anti-tumor effects of chemotherapy. The test diet (containing extensively hydrolyzed whey protein and medium chain triglycerides (MCTs)), was investigated in both tumor-naïve and tumor-bearing models to evaluate its effect on GI-M and chemo-efficacy, respectively. In both models, methotrexate was used as the representative chemotherapeutic agent and the diet was provided ad libitum for 14 days prior to treatment. GI-M was measured using the validated biomarker plasma citrulline, and chemo-efficacy defined by tumor burden (cm³/g body weight). The test diet significantly attenuated GI-M (P = 0.03), with associated reductions in diarrhea (P < 0.0001), weight loss (P < 0.05), daily activity (P < 0.02) and maintenance of body composition (P < 0.02). Moreover, the test diet showed significant impact on gut microbiota by increasing diversity and resilience, whilst also altering microbial composition and function (indicated by cecal short and brained chain fatty acids). The test diet did not impair the efficacy of methotrexate against mammary adenocarcinoma (tumor) cells. In line with the first model, the test diet minimized intestinal injury (P = 0.001) and diarrhea (P < 0.0001). These data support translational initiatives to determine the clinical feasibility, utility and efficacy of this diet to improve chemotherapy treatment outcomes.

Rodent models for anticancer toxicity studies: contributions to drug development and future perspectives

Antineoplastic treatment induces a type of gastrointestinal toxicity known as mucositis. Findings in animal models are usually easily reproducible, and standardized treatment regimens are often used, thus supporting translational science. Essential characteristics of mucositis, including intestinal permeability, inflammation, immune and oxidative responses, and tissue repair mechanisms, can be easily investigated in these models. Given the effects of mucositis on the quality of life of patients with cancer, and the importance of experimental models in the development of more effective new therapeutic alternatives, this review discusses progress and current challenges in using experimental models of mucositis in translational pharmacology research. Teaser Experimental models for studying gastrointestinal mucositis have provided a wealth of information improving the understanding of antineoplastic toxicity.

Application of big data analyses to compare the impact of oral and gastrointestinal mucositis on risks and outcomes of febrile neutropenia and septicemia among patients hospitalized for the treatment of leukemia or multiple myeloma

PURPOSE

Oral ulcerative mucositis (UM) and gastrointestinal mucositis (GIM) have been associated with increased likelihood of systemic infection (bacteremia and sepsis) in patients being treated for hematological malignancies. To better define and contrast differences between UM and GIM, we utilized the United States 2017 National Inpatient Sample and analyzed patients hospitalized for the treatment of multiple myeloma (MM) or leukemia.

METHODS

We utilized generalized linear models to assess the association between adverse events-UM and GIM-among hospitalized MM or leukemia patients and the outcome of febrile neutropenia (FN), septicemia, burden of illness, and mortality.

RESULTS

Of 71,780 hospitalized leukemia patients, 1255 had UM and 100 GIM. Of 113,915 MM patients, 1065 manifested UM and 230 had GIM. In an adjusted analysis, UM was significantly associated with increased risk of FN in both the leukemia (aOR = 2.87, 95% CI = 2.09-3.92) and MM cohorts (aOR = 4.96, 95% CI = 3.22-7.66). Contrastingly, UM had no effect on the risk of septicemia in either group. Likewise, GIM significantly increased the odds of FN in both leukemia (aOR = 2.81, 95% CI = 1.35-5.88) and MM (aOR = 3.75, 95% CI = 1.51-9.31) patients. Similar findings were noted when we restricted our analysis to recipients of high-dose condition regimens in preparation for hematopoietic stem-cell transplant. UM and GIM were consistently associated with higher burden of illness in all the cohorts.

CONCLUSION

This first use of big data provided an effective platform to assess the risks, outcomes, and cost of care of cancer treatment-related toxicities in patients hospitalized for the management of hematologic malignancies.

Exposure of anti-infective drugs and the dynamic changes of the gut microbiota during gastrointestinal mucositis in autologous stem cell transplant patients: a pilot study

Gastrointestinal mucositis could potentially compromise drug absorption due to functional loss of mucosa and other pathophysiological changes in the gastrointestinal microenvironment. Little is known about this effect on commonly used anti-infectives. This study aimed to explore the association between different stages of gastrointestinal mucositis, drug exposure, and gut microbiota. A prospective, observational pilot study was performed in HSCT patients aged ≥ 18 years receiving anti-infectives orally. Left-over blood samples and fecal swabs were collected from routine clinical care until 14 days after HSCT to analyze drug and citrulline concentrations and to determine the composition of the gut microbiota. 21 patients with a median age of 58 (interquartile range 54-64) years were included with 252 citrulline, 155 ciprofloxacin, 139 fluconazole, and 76 acyclovir concentrations and 48 fecal swabs obtained. Severe gastrointestinal mucositis was observed in all patients. Due to limited data correlation analysis was not done for valacyclovir and fluconazole, however we did observe a weak correlation between ciprofloxacin and citrulline concentrations. This could suggest that underexposure of ciprofloxacin can occur during severe mucositis. A follow-up study using frequent sampling rather than the use of left-over would be required to investigate the relationship between gastrointestinal mucositis, drug exposure, and gut microbiome.

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.

A Gut Instinct on Leukaemia: A New Mechanistic Hypothesis for Microbiota-Immune Crosstalk in Disease Progression and Relapse

Despite significant advances in the treatment of Chronic Myeloid and Acute Lymphoblastic Leukaemia (CML and ALL, respectively), disease progression and relapse remain a major problem. Growing evidence indicates the loss of immune surveillance of residual leukaemic cells as one of the main contributors to disease recurrence and relapse. More recently, there was an appreciation for how the host’s gut microbiota predisposes to relapse given its potent immunomodulatory capacity. This is especially compelling in haematological malignancies where changes in the gut microbiota have been identified after treatment, persisting in some patients for years after the completion of treatment. In this hypothesis-generating review, we discuss the interaction between the gut microbiota and treatment responses, and its capacity to influence the risk of relapse in both CML and ALL We hypothesize that the gut microbiota contributes to the creation of an immunosuppressive microenvironment, which promotes tumour progression and relapse.

The Insider: Impact of the Gut Microbiota on Cancer Immunity and Response to Therapies in Multiple Myeloma

The human microbiota is a unique set of microorganisms colonizing the human body and evolving within it from the very beginning. Acting as an insider, the microbiota provides nutrients, and mutualistically interacts with the host’s immune system, thus contributing to the generation of barriers against pathogens. While a strong link has been documented between intestinal dysbiosis (i.e., disruption to the microbiota homeostasis) and diseases, the mechanisms by which commensal bacteria impact a wide spectrum of mucosal and extramucosal human disorders have only partially been deciphered. This is particularly puzzling for multiple myeloma (MM), a treatable but incurable neoplasia of plasma cells that accumulate in the bone marrow and lead to end-organ damage. Here we revise the most recent literature on data from both the bench and the bedside that show how the gut microbiota modulates cancer immunity, potentially impacting the progression of asymptomatic monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM) to full blown MM. We also explore the effect of the gut microbiome on hematopoietic stem cell transplantation, chemotherapy, immunomodulating therapy and cancer immunotherapy in MM patients. Additionally, we identify the most cogent area of investigation that have the highest chance to delineate microbiota-related and pathobiology-based parameters for patient risk stratification. Lastly, we highlight microbiota-modulating strategies (i.e., diet, prebiotics, probiotics, fecal microbiota transplantation and postbiotics) that may reduce treatment-related toxicity in patients affected by MM as well as the rates of undertreatment of SMM patients.

Does Chemotherapy-Induced Gastrointestinal Mucositis Affect the Bioavailability and Efficacy of Anti-Infective Drugs?

Antimicrobial prophylaxis is increasingly being used in patients with hematological malignancies receiving high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT). However, few studies have focused on the potential impact of gastrointestinal mucositis (GI-M), a frequently observed side effect of chemotherapy in patients with cancer that affects the gastrointestinal microenvironment, on drug absorption. In this review, we discuss how chemotherapy leads to an overall loss of mucosal surface area and consequently to uncontrolled transport across the barrier. The barrier function is depending on intestinal luminal pH, intestinal motility, and diet. Another factor contributing to drug absorption is the gut microbiota, as it modulates the bioavailability of orally administrated drugs by altering the gastrointestinal properties. To better understand the complex interplay of factors in GI-M and drug absorption we suggest: (i) the longitudinal characterization of the impact of GI-M severity on drug exposure in patients, (ii) the development of tools to predict drug absorption, and (iii) strategies that allow the support of the gut microbiota. These studies will provide relevant data to better design strategies to reduce the severity and impact of GI-M in patients with cancer.

Microbe defines the efficacy of chemotherapeutic drug: a complete paradigm

The human body harbors a diverse microbiome that regulates host physiology and disease development. Several studies have also been reported where the human microbiome interferes with the efficacy of chemotherapeutics. Reports have also suggested the use of microbes in specific targeting and drug delivery. This review mainly focuses on the alteration in the efficacy of the drug by human microbiota. We have also discussed how the diversity in microbes can determine the therapeutic outcomes of a particular drug. The pathways involved in the alteration are also focused, with some highlights on microbes being used in cancer therapy.

NO, way to go: critical amino acids to replenish nitric oxide production in treating mucositis

PURPOSE OF REVIEW

There is still an unmet need for preventive and treatment strategies for chemotherapy-induced and radiotherapy-induced mucositis and its associated systemic inflammatory response (SIR) in cancer patients. Because of citrulline depletion due to cytotoxic therapy, nitric oxide (NO) production can be reduced, limiting its effect in many physiological processes. Restoring NO production could relieve mucositis severity by supporting host damage control mechanisms. Amino acids glutamine, arginine and citrulline are involved in NO production. This review including recent literature of preclinical and clinical studies will discuss the potential benefits of glutamine, arginine and citrulline on mucositis development with focus on NO production.

RECENT FINDINGS

Mucositis severity is more defined by host response to DNA damage than by DMA damage itself. Citrulline depletion because of afunctional enterocytes could be responsible for NO depletion during cytotoxic therapy. Restoring NO production during cytotoxic therapy could have a beneficial effect on mucositis development. Citrulline seems a more promising NO donor than glutamine or arginine during cytotoxic therapy, although clinical studies in mucositis patients are currently lacking.

SUMMARY

Glutamine, arginine and citrulline show in-vitro beneficial effects on inflammatory processes involved in mucositis. Translation to the clinic is difficult as demonstrated with use of glutamine and arginine. Citrulline, being the most potent NO donor with excellent oral bio-availability, is very promising as treatment choice for mucositis and its use deserves to be investigated in clinical trials with mucositis patients.