Gastrointestinal toxicity during induction treatment for childhood acute lymphoblastic leukemia: The impact of the gut microbiota

Chemotherapy-induced microbiota exacerbates the toxicity of chemotherapy through the suppression of interleukin-10 from macrophages

The gut microbiota has been shown to influence the efficacy and toxicity of chemotherapy, thereby affecting treatment outcomes. Understanding the mechanism by which microbiota affects chemotherapeutic toxicity would have a profound impact on cancer management. In this study, we report that fecal microbiota transplantation from oxaliplatin-exposed mice promotes toxicity in recipient mice. Splenic RNA sequencing and macrophage depletion experiment showed that the microbiota-induced toxicity of oxaliplatin in mice was dependent on macrophages. Furthermore, oxaliplatin-mediated toxicity was exacerbated in Il10-/- mice, but not attenuated in Rag1-/- mice. Adoptive transfer of macrophage into Il10-/- mice confirmed the role of macrophage-derived IL-10 in the improvement of oxaliplatin-induced toxicity. Depletion of fecal Lactobacillus and Bifidobacterium was associated with the exacerbation of oxaliplatin-mediated toxicity, whereas supplementation with these probiotics alleviated chemotherapy-induced toxicity. Importantly, IL-10 administration and probiotics supplementation did not attenuate the antitumor efficacy of chemotherapy. Clinically, patients with colorectal cancer exposed to oxaliplatin exhibited downregulation of peripheral CD45+IL-10+ cells. Collectively, our findings indicate that microbiota-mediated IL-10 production influences tolerance to chemotherapy, and thus represents a potential clinical target.

Gastrointestinal barrier integrity and mucosal inflammation as risk factors of blood stream infections in children treated for acute lymphoblastic leukaemia

Chemotherapy-induced mucositis increases the risk of blood stream infections (BSI) due to translocation of bacteria across the intestinal epithelium. Our study investigated if quantitative measures of intestinal mucositis severity, including plasma citrulline (a marker of functional enterocytes) and CCL20 (an intestinal immune homeostatic chemokine), could identify patients at risk of BSI. A total of 106 children with ALL undergoing induction treatment (NOPHO ALL 2008) were included and information regarding BSI episodes was collected from the patients' medical records. Twenty-seven patients (25%) developed BSI during induction. Patients with BSI had a larger decrease in citrulline after chemotherapy than patients without BSI, and nearly all BSI episodes (25/27) occurred in the group of patients exhibiting a drop in citrulline (OR = 6.4 [95% CI: 1.4-29.3], P = .008). Patients who developed BSI had higher plasma CCL20 levels on days 8, 15 and 22 than patients without BSI (all P < .05), and elevated CCL20 levels on day 8 increased the risk of subsequent BSI (OR = 1.57 [1.11-2.22] per doubling of CCL20 level, P = .01) in a multivariable logistic regression analysis. These findings suggest that children with ALL who develop BSI during chemotherapy are characterised by more severe intestinal mucositis, as measured by plasma citrulline and CCL20. These markers may be useful in early risk stratification to guide treatment decisions.

Microbiota, Diet and Acute Leukaemia: Tips and Tricks on Their Possible Connections

Acute leukaemia is probably one of the most recurrent cancers in children and younger adults, with an incidence of acute lymphoblastic leukaemia in 80% of cases and an incidence of acute myeloid leukaemia in 15% of cases. Yet, while incidence is common in children and adolescents, acute leukaemia is a rare disease whose aetiology still requires further analysis. Many studies have investigated the aetiology of acute leukaemia, reporting that the formation of gut microbiota may be modified by the start and development of many diseases. Considering that in patients affected by acute lymphoblastic leukaemia, there is an inherent disequilibrium in the gut microbiota before treatment compared with healthy patients, increasing evidence shows how dysbiosis of the gut microbiota provokes an inflammatory immune response, contributing to the development of cancer. Our analysis suggeststhe key role of gut microbiota in the modulation of the efficacy of leukaemia treatment as well as in the progress of many cancers, such as acute leukaemia. Therefore, in this paper, we present an examination of information found in literature regarding the role of dietary factors and gut microbiota alterations in the development of leukaemia and suggest possible future preventive and therapeutic strategies.

The gut microbiome: an important factor influencing therapy for pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most prevalent form of pediatric leukemia. The gut microbiome (GM) is crucial for proper nutrition, immunity, and biological conflict. Since the relationship between ALL and GM is bidirectional, ALL occurrence and treatment are closely related to GM destruction and the development of impaired immunity. Studies have discovered significant GM alterations in patients with ALL, including decreased diversity, that are likely directly caused by the development of ALL. Chemotherapy, antibiotic therapy, and hematopoietic stem cell transplantation (HSCT) are the mainstays of treatment for pediatric ALL. These approaches affect the composition, diversity, and abundance of intestinal microorganisms, which in turn affects therapeutic efficiency and can cause a variety of complications. Modulating the GM can aid the recovery of patients with ALL. This article discusses the various treatment modalities for pediatric ALL and their corresponding effects on the GM, as well as the changes in the GM that occur in children with ALL from diagnosis to treatment. Gaining a greater understanding of the link between ALL and the GM is expected to help improve treatment for pediatric ALL in the future.

Pronounced gut microbiota signatures in patients with JAK2V617F-positive essential thrombocythemia

Essential thrombocythemia (ET) is part of the Philadelphia chromosome-negative myeloproliferative neoplasms. It is characterized by an increased risk of thromboembolic events and also to a certain degree hypermetabolic symptoms. The gut microbiota is an important initiator of hematopoiesis and regulation of the immune system, but in patients with ET, where inflammation is a hallmark of the disease, it is vastly unexplored. In this study, we compared the gut microbiota via amplicon-based 16S rRNA gene sequencing of the V3-V4 region in 54 patients with ET according to mutation status Janus-kinase 2 (JAK2V617F)-positive vs JAK2V617F-negative patients with ET, and in 42 healthy controls (HCs). Gut microbiota richness was higher in patients with ET (median-observed richness, 283.5; range, 75-535) compared with HCs (median-observed richness, 191.5; range, 111-300; P < 0.001). Patients with ET had a different overall bacterial composition (beta diversity) than HCs (analysis of similarities [ANOSIM]; R = 0.063, P = 0.004). Patients with ET had a significantly lower relative abundance of taxa within the Firmicutes phylum compared with HCs (51% vs 59%, P = 0.03), and within that phylum, patients with ET also had a lower relative abundance of the genus Faecalibacterium (8% vs 15%, P < 0.001), an important immunoregulative bacterium. The microbiota signatures were more pronounced in patients harboring the JAK2V617F mutation, and highly similar to patients with polycythemia vera as previously described. These findings suggest that patients with ET may have an altered immune regulation; however, whether this dysregulation is induced in part by, or is itself inducing, an altered gut microbiota remains to be investigated. IMPORTANCE Essential thrombocythemia (ET) is a cancer characterized by thrombocyte overproduction. Inflammation has been shown to be vital in both the initiation and progression of other myeloproliferative neoplasms, and it is well known that the gut microbiota is important in the regulation of our immune system. However, the gut microbiota of patients with ET remains uninvestigated. In this study, we characterized the gut microbiota of patients with ET compared with healthy controls and thereby provide new insights into the field. We show that the gut microbiota of patients with ET differs significantly from that of healthy controls and the patients with ET have a lower relative abundance of important immunoregulative bacteria. Furthermore, we demonstrate that patients with JAK2V617F-positive ET have pronounced gut microbiota signatures compared with JAK2V617F-negative patients. Thereby confirming the importance of the underlying mutation, the immune response as well as the composition of the microbiota.

Gut microbiome immaturity and childhood acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common cancer of childhood. Here, we map emerging evidence suggesting that children with ALL at the time of diagnosis may have a delayed maturation of the gut microbiome compared with healthy children. This finding may be associated with early-life epidemiological factors previously identified as risk indicators for childhood ALL, including caesarean section birth, diminished breast feeding and paucity of social contacts. The consistently observed deficiency in short-chain fatty-acid-producing bacterial taxa in children with ALL has the potential to promote dysregulated immune responses and to, ultimately, increase the risk of transformation of preleukaemic clones in response to common infectious triggers. These data endorse the concept that a microbiome deficit in early life may contribute to the development of the major subtypes of childhood ALL and encourage the notion of risk-reducing microbiome-targeted intervention in the future.

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.

Title: Obesogenic microbial signatures and the development of obesity in childhood acute lymphoblastic leukemia

Childhood acute lymphoblastic leukemia (ALL) is the most common childhood cancer with survival exceeding 90% for standard-risk groups. A debilitating side-effect of treatment is the development of overweight/obesity (OW/OB), which develops in approximately 40% of children by the end of treatment. The microbiome has been associated with the development of OW/OB. We examined fluctuations in the microbiome with the development of OW/OB during the first six months of treatment at diagnosis, and two subsequent timepoints (N = 62). Shotgun metagenomic sequencing was performed on Illumina Nextseq system, and taxa and functional pathways were extracted from sequences using kraken2 and humann2, respectively. An association of increased presence of several species (e.g., Klebsiella pneumoniae, Escherichia coli) was observed in children with OW/OB, while lean-promoting species (Veillonella, Haemophilus, and Akkermansia) were increased in children who maintained a normal weight. Pathway analysis revealed purine nucleotide biosynthesis, sugar nucleotide biosynthesis, and enzyme cofactor biosynthesis were positively correlated with Bacteroides spp. among children with OW/OB. We identified several taxa and functional pathways that may confer increased risk for the development of OW/OB. The associations observed in this pilot are preliminary and warrant further research in the microbiome and the development of OW/OB in childhood ALL.

Adverse effects of antibiotics in children with cancer: are short-course antibiotics for febrile neutropenia part of the solution?

INTRODUCTION

Febrile neutropenia is a common complication experienced by children with cancer or those undergoing hematopoietic stem cell transplantation. Repeated episodes of febrile neutropenia result in cumulative exposure to broad-spectrum antibiotics with potential for a range of serious adverse effects. Short-course antibiotics, even in patients with high-risk febrile neutropenia, may offer a solution.

AREAS COVERED

This review addresses the known broad effects of antibiotics, highlights developments in understanding the relationship between cancer, antibiotics, and the gut microbiome, and discusses emerging evidence regarding long-term adverse antibiotic effects. The authors consider available evidence to guide the duration of empiric antibiotics in pediatric febrile neutropenia and directions for future research.

EXPERT OPINION

Broad-spectrum antibiotics are associated with antimicrobial resistance, Clostridioides difficile infection, invasive candidiasis, significant disturbance of the gut microbiome and may seriously impact outcomes in children with cancer or undergoing allogenic hematopoietic stem cell transplant. Short-course empiric antibiotics are likely safe in most children with febrile neutropenia and present a valuable opportunity to reduce the risks of antibiotic exposure.

Human microbiomes in cancer development and therapy

Colonies formed by bacteria, archaea, fungi, and viral groups and their genomes, metabolites, and expressed proteins constitute complex human microbiomes. An increasing evidences showed that carcinogenesis and disease progression were link to microbiomes. Different organ sources, their microbial species, and their metabolites are different; the mechanisms of carcinogenic or procancerous are also different. Here, we summarize how microbiomes contribute to carcinogenesis and disease progression in cancers of the skin, mouth, esophagus, lung, gastrointestinal, genital, blood, and lymph malignancy. We also insight into the molecular mechanisms of triggering, promoting, or inhibiting carcinogenesis and disease progress induced by microbiomes or/and their secretions of bioactive metabolites. And then, the strategies of application of microorganisms in cancer treatment were discussed in detail. However, the mechanisms by which human microbiomes function are still poorly understood. The bidirectional interactions between microbiotas and endocrine systems need to be clarified. Probiotics and prebiotics are believed to benefit human health via a variety of mechanisms, in particular, in tumor inhibition. It is largely unknown how microbial agents cause cancer or how cancer progresses. We expect this review may open new perspectives on possible therapeutic approaches of patients with cancer.

The gastrointestinal antibiotic resistome in pediatric leukemia and lymphoma patients

Introduction

Most children with leukemia and lymphoma experience febrile neutropenia. These are treated with empiric antibiotics that include β-lactams and/or vancomycin. These are often administered for extended periods, and the effect on the resistome is unknown.

Methods

We examined the impact of repeated courses and duration of antibiotic use on the resistome of 39 pediatric leukemia and lymphoma patients. Shotgun metagenome sequences from 127 stool samples of pediatric oncology patients were examined for abundance of antibiotic resistance genes (ARGs) in each sample. Abundances were grouped by repeated courses (no antibiotics, 1-2 courses, 3+ courses) and duration (no use, short duration, long and/or mixed durationg) of β-lactams, vancomycin and "any antibiotic" use. We assessed changes in both taxonomic composition and prevalence of ARGs among these groups.

Results

We found that Bacteroidetes taxa and β-lactam resistance genes decreased, while opportunistic Firmicutes and Proteobacteria taxa, along with multidrug resistance genes, increased with repeated courses and/or duration of antibiotics. Efflux pump related genes predominated (92%) among the increased multidrug genes. While we found β-lactam ARGs present in the resistome, the taxa that appear to contain them were kept in check by antibiotic treatment. Multidrug ARGs, mostly efflux pumps or regulators of efflux pump genes, were associated with opportunistic pathogens, and both increased in the resistome with repeated antibiotic use and/or increased duration.

Conclusions

Given the strong association between opportunistic pathogens and multidrug-related efflux pumps, we suggest that drug efflux capacity might allow the opportunistic pathogens to persist or increase despite repeated courses and/or duration of antibiotics. While drug efflux is the most direct explanation, other mechanisms that enhance the ability of opportunistic pathogens to handle environmental stress, or other aspects of the treatment environment, could also contribute to their ability to flourish within the gut during treatment. Persistence of opportunistic pathogens in an already dysbiotic and weakened gastrointestinal tract could increase the likelihood of life-threatening blood borne infections. Of the 39 patients, 59% experienced at least one gastrointestinal or blood infection and 60% of bacteremia's were bacteria found in stool samples. Antimicrobial stewardship and appropriate use and duration of antibiotics could help reduce morbidity and mortality in this vulnerable population.

Gut microbiota in acute leukemia: Current evidence and future directions

Gut microbiota includes a large number of microorganisms inhabiting the human gastrointestinal tract, which show a wide range of physiological functions, including digestion, metabolism, immunity, neural development, etc., and are considered to play an increasingly important role in health and disease. A large number of studies have shown that gut microbiota are closely associated with the onset and development of several diseases. In particular, the interaction between gut microbiota and cancer has recently attracted scholars' attention. Acute leukemia (AL) is a common hematologic malignancy, especially in children. Microbiota can affect hematopoietic function, and the effects of chemotherapy and immunotherapy on AL are noteworthy. The composition and diversity of gut microbiota are important factors that influence and predict the complications and prognosis of AL after chemotherapy or hematopoietic stem cell transplantation. Probiotics, prebiotics, fecal microbiota transplantation, and dietary regulation may reduce side effects of leukemia therapy, improve response to treatment, and improve prognosis. This review concentrated on the role of the gut microbiota in the onset and development of AL, the response and side effects of chemotherapy drugs, infection during treatment, and therapeutic efficacy. According to the characteristics of gut microbes, the applications and prospects of microbial preparations were discussed.

Oral Lactoferrin Supplementation during Induction Chemotherapy Promotes Gut Microbiome Eubiosis in Pediatric Patients with Hematologic Malignancies

Induction chemotherapy is the first-line treatment for pediatric patients with hematologic malignancies. However, several complications may arise, mainly infections and febrile neutropenia, with a strong impact on patient morbidity and mortality. Such complications have been shown to be closely related to alterations of the gut microbiome (GM), making the design of strategies to foster its eubiosis of utmost clinical importance. Here, we evaluated the impact of oral supplementation of lactoferrin (LF), a glycoprotein endowed with anti-inflammatory, immunomodulatory and antimicrobial activities, on GM dynamics in pediatric oncohematologic patients during induction chemotherapy. Specifically, we conducted a double blind, placebo-controlled trial in which GM was profiled through 16S rRNA gene sequencing before and after two weeks of oral supplementation with LF or placebo. LF was safely administered with no adverse effects and promoted GM homeostasis by favoring the maintenance of diversity and preventing the bloom of pathobionts (e.g., Enterococcus). LF could, therefore, be a promising adjunct to current therapeutic strategies in these fragile individuals to reduce the risk of GM-related complications.

Gut Microbiome Suffers from Hematopoietic Stem Cell Transplantation in Childhood and Its Characteristics Are Positively Associated with Intra-Hospital Physical Exercise

Gut microbiome impairment is a serious side effect of cancer treatment. The aim of this study was to identify the effects of hematopoietic stem cell transplantation (HSCT) treatment on gut microbiota composition in children with acute lymphoblastic leukemia (ALL). Fecal microbiotas were categorized using specific primers targeting the V1-V3 region of 16S rDNA in eligible pediatric ALL patients after HSCT (n = 16) and in healthy controls (Ctrl, n = 13). An intra-hospital exercise program was also organized for child patients during HSCT treatment. Significant differences in gut microbiota composition were observed between ALL HSCT and Ctrl with further negative effects. Plasma C-reactive protein correlated positively with the pathogenic bacteria Enterococcus spp. and negatively with beneficial bacteria Butyriccocus spp. or Akkermansia spp., respectively (rs = 0.511, p = 0.05; rs = -0.541, p = 0.04; rs = -0.738, p = 0.02). Bacterial alpha diversity correlated with the exercise training characteristics. Therefore, specific changes in the microbiota of children were associated with systemic inflammation or the ability to exercise physically during HSCT treatment.

The interplay between anticancer challenges and the microbial communities from the gut

Cancer being an increasing burden on human health, the use of anticancer drugs has risen over the last decades. The physiological effects of these drugs are not only perceived by the host's cells but also by the microbial cells it harbors as commensals, notably the gut microbiota. Since the early '50 s, the cytotoxicity of anticancer chemotherapy was evaluated on bacteria revealing some antimicrobial activities that result in an established perturbation of the gut microbiota. This perturbation can affect the host's health through dysbiosis, which can lead to multiple complications, but has also been shown to have a direct effect on the treatment efficiency.We, therefore, conducted a review of literature focusing on this triangular relationship involving the microbial communities from the gut, the host's disease, and the anticancer treatment. We focused specifically on the antimicrobial effects of anticancer chemotherapy, their impact on mutagenesis in bacteria, and the perspectives of using bacteria-based tools to help in the diagnostic and treatment of cancer.

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.

Antibiotics in early life and childhood pre-B-ALL. Reasons to analyze a possible new piece in the puzzle

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer with precursor B-cell ALL (pB-ALL) accounting for ~ 85% of the cases. Childhood pB-ALL development is influenced by genetic susceptibility and host immune responses. The role of the intestinal microbiome in leukemogenesis is gaining increasing attention since Vicente-Dueñas' seminal work demonstrated that the gut microbiome is distinct in mice genetically predisposed to ALL and that the alteration of this microbiome by antibiotics is able to trigger pB-ALL in Pax5 heterozygous mice in the absence of infectious stimuli. In this review we provide an overview on novel insights on the role of the microbiome in normal and preleukemic hematopoiesis, inflammation, the effect of dysbiosis on hematopoietic stem cells and the emerging importance of the innate immune responses in the conversion from preleukemic to leukemic state in childhood ALL. Since antibiotics, which represent one of the most widely used medical interventions, alter the gut microbial composition and can cause a state of dysbiosis, this raises exciting epidemiological questions regarding the implications for antibiotic use in early life, especially in infants with a a preleukemic "first hit". Sheading light through a rigorous study on this piece of the puzzle may have broad implications for clinical practice.

THE EFFECT OF S-ADEMETIONINE ON PLASMA CITRULLINE LEVEL DURING CHEMOTHERAPY-INDUCED OXIDATIVE STRESS IN PATIENTS WITH CHRONIC LYMPHOPROLIFERATIVE DISORDERS

OBJECTIVE

The aim: To investigate the effect of S-ademetionine on plasma citrulline level in patients with chronic lymphoproliferative disorders (CLPD) during chemotherapy-induced oxidative stress.

PATIENTS AND METHODS

Materials and methods: 25 patients with CLPD were examined. Examinations were conducted twice: before chemotherapy (CT) and after 3 courses of CT. Several biochemical markers in the blood were determined: the activity of catalase, the level of plasma citrulline, the concentration of N-acetylneuraminic acid (NANA) and the concentration of substances that form a trimethine complex (TBARS) with 2-thiobarbituric acid. Patients were divided into groups: І (n=14) - patients who underwent only CT; ІІ (n=16) - patients who during CT received S-ademetionine, at a dose of 1000 mg/day intravenously for 10 days, then 500 mg twice a day for 20 days. ІІІ (n=20) -the control group of 20 practically healthy individuals.

RESULTS

Results: Patients in both groups with CLPD had pre-existed mucosal injury that was characterized by 1.25 (p=0.0025) and 1.26 times (р=0.006) higher blood NANA concentration compared to the control group. The conduction of CT was associated with enterocytes dysfunction, which was characterized by 1,66 times (p=0,0002) lower plasma citrulline level in patients of group I compared to the initial examination. The infusion of S-ademetionine attenuated intestinal dysfunction that was associated with 1,23 times (p=0,0005) higher blood citrulline level after the CT as compared to group I.

CONCLUSION

Conclusions: The infusion of S-ademetionine as adjuvant treatment in patients with CLPD provided effective prophylaxis of intestinal injury that was associated with higher blood citrulline level after the conduction of CT.

Gut microbiome in pediatric acute leukemia: from predisposition to cure

The gut microbiome (GM) has emerged as a key factor in the genesis and progression of many diseases. The intestinal bacterial composition also influences treatment-related side effects and even the efficacy of oncological therapies. Acute leukemia (AL) is the most common cancer among children and the most frequent cause of cancer-related death during childhood. Outcomes have improved considerably over the past 4 decades, with the current long-term survival for acute lymphoblastic leukemia being ∼90%. However, several acute toxicities and long-term sequelae are associated with the multimodal therapy protocols applied in these patients. Specific GM configurations could contribute to the multistep developmental hypothesis for leukemogenesis. Moreover, GM alterations occur during the AL therapeutic course and are associated with treatment-related complications, especially during hematopoietic stem cell transplantation. The GM perturbation could last even after the removal of microbiome-modifying factors, like antibiotics, chemotherapeutic drugs, or alloimmune reactions, contributing to several health-related issues in AL survivors. The purpose of this article is to provide a comprehensive review of the chronological changes of GM in children with AL, from predisposition to cure. The underpinning biological processes and the potential interventions to modulate the GM toward a potentially health-promoting configuration are also highlighted.

The Microbiome in Childhood Acute Lymphoblastic Leukemia

For almost 30 years, the term "holobiont" has referred to an ecological unit where a host (e.g., human) and all species living in or around it are considered together. The concept highlights the complex interactions between the host and the other species, which, if disturbed may lead to disease and premature aging. Specifically, the impact of microbiome alterations on the etiology of acute lymphoblastic leukemia (ALL) in children is not fully understood, but has been the focus of much research in recent years. In ALL patients, significant reductions in microbiome diversity are already observable at disease onset. It remains unclear whether such alterations at diagnosis are etiologically linked with leukemogenesis or simply due to immunological alteration preceding ALL onset. Regardless, all chemotherapeutic treatment regimens severely affect the microbiome, accompanied by severe side effects, including mucositis, systemic inflammation, and infection. In particular, dominance of Enterococcaceae is predictive of infections during chemotherapy. Long-term dysbiosis, like depletion of Faecalibacterium, has been observed in ALL survivors. Modulation of the microbiome (e.g., by fecal microbiota transplant, probiotics, or prebiotics) is currently being researched for potential protective effects. Herein, we review the latest microbiome studies in pediatric ALL patients.

State of the art: the role of citrulline as biomarker in patients with chemotherapy- or graft-versus-host-disease-induced mucositis

PURPOSE OF REVIEW

Serum or plasma citrulline levels are used as biomarker for a broad spectrum of intestinal functions. During high-dose chemotherapy, citrulline levels are decreased due to mucositis, a common side effect of chemotherapy. This may decrease intestinal function and result in diarrhea. In this review, most recent studies investigating citrulline as biomarker for intestinal function are discussed, with focus on patients with oncological diseases, specifically hematological malignancies with chemotherapy- or Graft-versus-Host-disease (GVHD)-induced mucositis.

RECENT FINDINGS

Citrulline has recently been widely studied in relation to intestinal function and various clinical conditions. It seems therefore a promising noninvasive biomarker in clinical practice for more than intestinal function alone. The association between citrulline levels and intestinal function in patients with hematological malignancies, with or without mucositis remains unclear, as no other parameters of intestinal function for this purpose were assessed.

SUMMARY

In conclusion, citrulline seems to be a promising noninvasive biomarker for various intestinal conditions in general, and potentially for intestinal function in patients with chemotherapy- or GVHD-induced mucositis. It is unclear from recent literature whether high fecal volume or diarrhea as side effect, results in impaired intestinal function and severe malabsorption and if citrulline biomarkers can be useful to detect this.

Induction therapy for acute lymphoblastic leukemia: incidence and risk factors for bloodstream infections

Among the treatment-related acute toxic effects, risks for bloodstream infections (BSIs) are associated with several variables. The authors carried out a retrospective cohort study with 259 children and adolescents with ALL, treated with the GBTLI-LLA 2009 protocol, in order to assess the incidence of BSIs in the induction phase; to determine the risk factors for these BSIs; and to identify the related microorganisms and sensitivity profile of the microorganisms related to these infections. BSIs were documented in 19.3% of patients. The isolated microorganisms were 39 Gram-negative bacteria, 21 Gram-positive bacteria, and four fungi. There was a statistically significant risk of BSI between the variables: protocol for T-line-derived leukemia (Derived T Protocol) (p = 0.020), oral manifestations (p = 0.015), central venous catheter (p = 0.008), and bladder catheter (p = 0.004). BSI is a frequent event in ALL patients during the induction phase. The identification of these factors can allow the elaboration and improvement of strategies for the intensification of supportive care, prevention, and rapid treatment of infections.

Microbiota long-term dynamics and prediction of acute graft-versus-host disease in pediatric allogeneic stem cell transplantation

BACKGROUND

Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) exhibit changes in their gut microbiota and are experiencing a range of complications, including acute graft-versus-host disease (aGvHD). It is unknown if, when, and under which conditions a re-establishment of microbial and immunological homeostasis occurs. It is also unclear whether microbiota long-term dynamics occur at other body sites than the gut such as the mouth or nose. Moreover, it is not known whether the patients' microbiota prior to HSCT holds clues to whether the patient would suffer from severe complications subsequent to HSCT. Here, we take a holobiont perspective and performed an integrated host-microbiota analysis of the gut, oral, and nasal microbiota in 29 children undergoing allo-HSCT.

RESULTS

The bacterial diversity decreased in the gut, nose, and mouth during the first month and reconstituted again 1-3 months after allo-HSCT. The microbial community composition traversed three phases over 1 year. Distinct taxa discriminated the microbiota temporally at all three body sides, including Enterococcus spp., Lactobacillus spp., and Blautia spp. in the gut. Of note, certain microbial taxa appeared already changed in the patients prior to allo-HSCT as compared with healthy children. Acute GvHD occurring after allo-HSCT could be predicted from the microbiota composition at all three body sites prior to HSCT. The reconstitution of CD4⁺ T cells, T_H17, and B cells was associated with distinct taxa of the gut, oral, and nasal microbiota.

CONCLUSIONS

This study reveals for the first time bacteria in the mouth and nose that may predict aGvHD. Monitoring of the microbiota at different body sites in HSCT patients and particularly through involvement of samples prior to transplantation may be of prognostic value and could assist in guiding personalized treatment strategies. The identification of distinct bacteria that have a potential to predict post-transplant aGvHD might provide opportunities for an improved preventive clinical management, including a modulation of microbiomes. The host-microbiota associations shared between several body sites might also support an implementation of more feasible oral and nasal swab sampling-based analyses. Altogether, the findings suggest that the microbiota and host factors together could provide actionable information to guiding precision medicine. Video Abstract.

Peptidoglycan Recognition Peptide 2 Aggravates Weight Loss in a Murine Model of Chemotherapy-Induced Gastrointestinal Toxicity

Introduction: Chemotherapy-induced gastrointestinal toxicity (CIGT) is a frequent, severe and dose-limiting side effect. Few treatments have proven effective for CIGT. CIGT is characterized by activation of the nuclear factor kappa B pathway which, leads to upregulation of proinflammatory cytokines. The innate immune protein peptidoglycan recognition peptide 2 (PGLYRP2) binds to and hydrolyzes microbial peptidoglycan. Expression of PGLYRP2 is upregulated in the intestine of chemotherapy-treated piglets. In this experimental study, we investigated the role of Pglyrp2 in the development and severity of murine CIGT. Methods: Pglyrp2 wildtype and Pglyrp2 knockout mice received intraperitoneal injections of chemotherapy (Doxorubicin 20 mg/kg) to induce CIGT. Weight was monitored daily, and animals were euthanized after 2 or 7 days. Expression of proinflammatory cytokines in the jejunum was measured by quantitative real-time polymerase-chain reaction and enzyme-linked immunosorbent assay. Villus height, crypt depth, and histologic inflammation were evaluated on haematoxylin and eosin stained tissue specimens. Results: Chemotherapeutic treatment induced weight loss (p < 0.05), shortening of the small intestine (p < 0.05), elongation of villus height (p < 0.05), increased crypt depth (p < 0.05), and led to elevated mRNA levels of II1β (p < 0.05), II6 (p < 0.05), and Tnf (p < 0.001) at day 2. Protein levels of IL1β, IL6, and TNFα did not change after exposure to chemotherapy. Doxorubicin treated wildtype mice had a more pronounced weight loss compared to knockout mice from day 3 to day 7 (D3-D6: p < 0.05 and D7: p < 0.01). No other phenotypic differences were detected. Conclusion: Pglyrp2 aggravates chemotherapy-induced weight loss but does not induce a specific pattern of inflammation and morphological changes in the small intestine.

The impact of modulating the gastrointestinal microbiota in cancer patients

Gastrointestinal microbiota is vastly deregulated in cancer patients due to different factors, but the exact mechanisms of interaction between cancer and microbiome are still poorly understood. Current evidence suggests that alterations in the composition of the microbiota may affect efficacy and toxicity of anti-cancer therapies. Recent preclinical and clinical studies demonstrate different mechanisms and outcomes of deregulation of gut microbiome, and investigate effects of modulating gastrointestinal microbiota in cancer patients. This paper reviews effects of altered microbiome on anti-cancer management, including antibiotics, chemotherapy and immunotherapy, as well as possible outcomes of modulating altered microbiome by probiotics or faecal microbiome transplantation in cancer patients.

Gut microecology: Why our microbes could be key to our health

The human body contains a large number of microorganisms, and the gut microecology environment contains the largest number and types of microorganisms. The structure and function of gut microbiota are closely related to the health of the human body. In a cascade of studies, the diversity of gut microbiota and its metabolite often found changed in patients or mice model. What kind of gut microbiota that associated with the occurrence or treatment of diseases were also found in many studies. Gut microbiota and its products can affect the function of the human body. Short-chain fatty acids, bile acid, indoles and so on were found can regulate the inflammation, immune response to affect the process of diseases. Immune cells like natural killer T cells, CD3 + T cells were also found had a link to gut microbiota which associated with diseases. Changes in gut microbiota are associated with changes in the body's major systems, such as the digestive system, the endocrine system, the cardiovascular system, the endocrine and metabolic system, the urinary system diseases, the respiratory system and so on. It is of great significance to study gut microecology for the prevention and treatment of various human diseases.