Microbiota Manipulation With Prebiotics and Probiotics in Patients Undergoing Stem Cell Transplantation

Nutrition issues in adult hematopoietic cell transplantation: A narrative review of latest advances

Patients undergoing hematopoietic cell transplantation (HCT) are a highly heterogenous population with respect to their unique nutrient requirements and need for nutrition support. Dose-intensive conditioning regimens in addition to the debilitating effects of graft-vs-host disease impact and adversely affect the transplant recipient's nutrition status. Decreased oral intake, increased nutrient requirements, and impaired nutrient absorption and utilization often necessitate specialized nutrition support. The use of parenteral nutrition and enteral nutrition support, as well as dietary intervention strategies for immunocompromised patients, have varied over the past five decades and are highly dependent on the type of transplant used. This review highlights adult nutrition assessment components, nutrition support practices, and management of complex nutrition consequences associated with HCT.

Modern views of nutritional support in patients undergoing allogeneic stem cell transplantation

Patients undergoing allogeneic stem cell transplant (HSCT) have a higher risk of developing malnutrition. The aetiology is multifactorial and complex: the conditioning regimen causes damages to the gastrointestinal tract that can contribute to trigger graft-versus-host disease and/or infectious complications that adversely affect food intake and the gut absorption of nutrients in transplant recipients. Consequently, patients might develop weight loss and muscle wasting. There is mounting evidence that insufficient muscle mass increases the risk of toxicity to many chemotherapy drugs. Furthermore, the screening for malnutrition, assessment and intervention can vary among HSCT centers. Hereby, we report the main nutritional clinical issues in the field of HSCT and the main nutritional tools used in this setting. Future clinical trials investigating nutritional tools and dose-escalating studies based on pre-treatment body composition assessment may help having the potential to alter cancer treatment paradigms.

Gut microbiome in children undergoing hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is used in children as a treatment for various cancers, e.g. acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), or other diseases, e.g. severe congenital immunodeficiency, metabolic disorders, hence the patient population is quite diverse. There is an increasing interest on the role of the microbiome in peri-transplant period. In this review, concepts of HSCT with the focus on the importance of microbiome composition, its changes during treatment and possible microbiota oriented interventions will be discussed. This paper analyzes data in pediatric population, but in view of interesting results and absence of analogous data for pediatric patients, it also looks at studies performed on adult population and pre-clinical trials on animals discussing possible translation to children.

Chinese guidelines for integrated diagnosis and treatment of intestinal microecology technologies in tumor application (2024 Edition)

ABSTRACT

Intestinal microecology (IM) is the largest and most important microecological system of the human body. Furthermore, it is the key factor for activating and maintaining the physiological functions of the intestine. Numerous studies have investigated the effects of the gut microbiota on the different tissues and organs of the human body as well as their association with various diseases, and the findings are gradually being translated into clinical practice. The gut microbiota affects the occurrence, progression, treatment response, and toxic side effects of tumors. The deepening of research related to IM and tumors has opened a new chapter in IM research driven by methods and technologies such as second-generation sequencing and bioinformatics. The IM maintains the function of the host immune system and plays a pivotal role in tumor-control drug therapy. Increasing evidence has proven that the efficacy of tumor-control drugs largely depends on the IM balance, and strategies based on the IM technology show promising application prospects in the diagnosis and treatment of tumor. The Tumor and Microecology Professional Committee of the Chinese Anti-cancer Association gathered relevant experts to discuss and propose the "Chinese guidelines for integrated diagnosis and treatment of IM technologies in tumor application (2024 Edition)," which was established based on the research progress of the application of the IM technology in tumor to provide a basis for the standardization of the diagnosis and treatment of the IM technology in the tumor.

Nutritional aspects in autoimmune diseases undergoing hematopoietic stem cell transplantation: overview and recommendations on behalf of the EBMT ADWP and Nurses Group

Autoimmune diseases (ADs) represent a heterogeneous group of conditions affecting 5-10% of the global population. In recent decades, hematopoietic stem cell transplant (HSCT), mainly autologous, has been successfully adopted to treat patients affected by severe/refractory ADs. In this context malnutrition has a detrimental impact on relapse, mortality, infection rate, engraftment, long-term survival, and prolongation of hospitalization. However, in this population, the management of nutrition should be improved since nutritional assessment is partially performed in routine clinical practice. A panel of nurses and physicians from the European Society for Blood and Marrow Transplantation (EBMT) reviewed all available evidence based on current literature and expert practices from centers with extensive experience in HSCT for ADs, on the nutritional management of ADs patients during HSCT procedure. In this context, adequate nutritional status predicts a better response to treatment and improves quality of life. Herein, a systematic and comprehensive monitoring of nutritional status before, during and after HSCT, with adequate nutritional support in the case of ADs patients, in addition to assessing the dietary requirements associated with HSCT has been covered. Moreover, given the singularity of each AD, the underlying disease should be considered for an appropriate approach. The management and evaluation of nutritional status must be carried out by a multidisciplinary team to assess the needs, monitor the effectiveness of each intervention, and prevent complications, especially in complex situations as patients affected by ADs.

Blood and guts: how the intestinal microbiome shapes hematopoiesis and treatment of hematologic disease

ABSTRACT

Over the past 10 years, there has been a marked increase in recognition of the interplay between the intestinal microbiome and the hematopoietic system. Despite their apparent distance in the body, a large literature now supports the relevance of the normal intestinal microbiota to steady-state blood production, affecting both hematopoietic stem and progenitor cells as well as differentiated immune cells. Microbial metabolites enter the circulation where they can trigger cytokine signaling that influences hematopoiesis. Furthermore, the state of the microbiome is now recognized to affect outcomes from hematopoietic stem cell transplant, immunotherapy, and cellular therapies for hematologic malignancies. Here we review the mechanisms by which microbiotas influence hematopoiesis in development and adulthood as well as the avenues by which microbiotas are thought to impact stem cell transplant engraftment, graft-versus-host disease, and efficacy of cell and immunotherapies. We highlight areas of future research that may lead to reduced adverse effects of antibiotic use and improved outcomes for patients with hematologic conditions.

Gut microbiota, microbiota-derived metabolites, and graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is one of the most effective treatment strategies for leukemia, lymphoma, and other hematologic malignancies. However, graft-versus-host disease (GVHD) can significantly reduce the survival rate and quality of life of patients after transplantation, and is therefore the greatest obstacle to transplantation. The recent development of new technologies, including high-throughput sequencing, metabolomics, and others, has facilitated great progress in understanding the complex interactions between gut microbiota, microbiota-derived metabolites, and the host. Of these interactions, the relationship between gut microbiota, microbial-associated metabolites, and GVHD has been most intensively researched. Studies have shown that GVHD patients often suffer from gut microbiota dysbiosis, which mainly manifests as decreased microbial diversity and changes in microbial composition and microbiota-derived metabolites, both of which are significant predictors of poor prognosis in GVHD patients. Therefore, the purpose of this review is to summarize what is known regarding changes in gut microbiota and microbiota-derived metabolites in GVHD, their relationship to GVHD prognosis, and corresponding clinical strategies designed to prevent microbial dysregulation and facilitate treatment of GVHD.

Feasibility of a dietary intervention to modify gut microbial metabolism in patients with hematopoietic stem cell transplantation

Evaluation of the impact of dietary intervention on gastrointestinal microbiota and metabolites after allogeneic hematopoietic stem cell transplantation (HCT) is lacking. We conducted a feasibility study as the first of a two-phase trial. Ten adults received resistant potato starch (RPS) daily from day -7 to day 100. The primary objective was to test the feasibility of RPS and its effect on intestinal microbiome and metabolites, including the short-chain fatty acid butyrate. Feasibility met the preset goal of 60% or more, adhering to 70% or more doses; fecal butyrate levels were significantly higher when participants were on RPS than when they were not (P < 0.0001). An exploratory objective was to evaluate plasma metabolites. We observed longitudinal changes in plasma metabolites compared to baseline, which were independent of RPS (P < 0.0001). However, in recipients of RPS, the dominant plasma metabolites were more stable compared to historical controls with significant difference at engraftment (P < 0.05). These results indicate that RPS in recipients of allogeneic HCT is feasible; in this study, it was associated with significant alterations in intestinal and plasma metabolites. A phase 2 trial examining the effect of RPS on graft-versus-host disease in recipients of allogeneic HCT is underway. ClinicalTrials.gov registration: NCT02763033 .

Chronic GvHD NIH Consensus Project Biology Task Force: evolving path to personalized treatment of chronic GvHD

Chronic graft-versus-host disease (cGvHD) remains a prominent barrier to allogeneic hematopoietic stem cell transplantion as the leading cause of nonrelapse mortality and significant morbidity. Tremendous progress has been achieved in both the understanding of pathophysiology and the development of new therapies for cGvHD. Although our field has historically approached treatment from an empiric position, research performed at the bedside and bench has elucidated some of the complex pathophysiology of cGvHD. From the clinical perspective, there is significant variability of disease manifestations between individual patients, pointing to diverse biological underpinnings. Capitalizing on progress made to date, the field is now focused on establishing personalized approaches to treatment. The intent of this article is to concisely review recent knowledge gained and formulate a path toward patient-specific cGvHD therapy.

The European Society for Blood and Marrow Transplantation (EBMT) roadmap and perspectives to improve nutritional care in patients undergoing hematopoietic stem cell transplantation on behalf of the Cellular Therapy and Immunobiology Working Party (CTIWP) and the Nurses Group (NG) of the EBMT

Malnutrition is the most common comorbidity during the continuum of hematopoietic stem cell transplant (HSCT) and negatively impacts clinical outcomes, response to therapy, quality of life, and costs. The intensive conditioning regimen administered before transplant causes inflammatory damages to the gastrointestinal system, which themselves contribute to trigger graft versus host disease (GvHD) in the allogeneic setting. GvHD and other post-transplant complications such as infections adversely affect food intake and gut absorption of nutrients. Consequently, patients exhibit signs of malnutrition such as weight loss and muscle wasting, thus triggering a "vicious circle" that favours additional complications. Among HSCT centres, there is marked variability in nutritional care, from screening for malnutrition to nutritional intervention. The present paper, elaborated by the Cellular Therapy and Immunobiology Working Party and the Nurses Group of the European Society for Blood and Marrow Transplantation, aims at defining a roadmap that identifies the main nutritional critical issues in the field of HSCT. This document will be propaedeutic to the development of clinical algorithms to counteract risk factors of malnutrition, based on scientific evidence and shared among HSCT centres, and thus maximize transplant outcomes.

The Role of Fecal Microbiota Transplantation in the Allogeneic Stem Cell Transplant Setting

Microbiota changes during allogeneic hematopoietic stem cell transplantation has several known causes: conditioning chemotherapy and radiation, broad-spectrum antibiotic administration, modification in nutrition status and diet, and graft-versus-host disease. This article aims to review the current knowledge about the close link between microbiota and allogeneic stem cell transplantation setting. The PubMed search engine was used to perform this review. We analyzed data on microbiota dysbiosis related to the above-mentioned affecting factors. We also looked at treatments aimed at modifying gut dysbiosis and applications of fecal microbiota transplantation in the allogeneic stem cell transplant field, with particular interest in fecal microbiota transplantation for graft-versus-host disease (GvHD), multidrug-resistant and clostridium difficile infections, and microbiota restoration after chemotherapy and antibiotic therapy.

Neutropenia and antibiotics: when, what, how and why?

PURPOSE OF REVIEW

Our aim is to review recent literature on antibiotic use in patients with neutropenia.

RECENT FINDINGS

Prophylactic antibiotics are associated with risks and have limited mortality benefit. While early antibiotic use in febrile neutropenia (FN) is critical, early de-escalation or discontinuation may be safe in many patients.

SUMMARY

With an increasing understanding of potential risks and benefits of use and improved risk assessment, paradigms of antibiotic use in neutropenic patients are changing.

From support to therapy: rethinking the role of nutrition in acute graft-versus-host disease

Allogeneic Hematopoietic stem cell transplantation (HSCT) offers a potential cure for patients with hematologic malignancies. Unfortunately, graft-versus-host disease (GVHD) remains a major obstacle to the greater success of this treatment. Despite intensive research efforts over the past several decades, GVHD is still a major cause of morbidity and mortality in patients receiving allogeneic HSCT. The genetic disparity between donor and recipient is the primary factor that dictates the extent of alloimmune response and the severity of acute GVHD (aGVHD). However, some nongenetic factors are also actively involved in GVHD pathogenesis. Thus, identifying host factors that can be readily modified to reduce GVHD risk is of important clinical significance. We are particularly interested in the potential role of nutrition, as a nongenetic factor, in the etiology and management of aGVHD. In this article, we summarize recent findings regarding how different routes of nutritional support and various dietary factors affect aGVHD. Since diet is one of the most important factors that shape gut microbiota, we also provide evidence for a potential link between certain nutrients and gut microbiota in recipients of allogeneic HSCT. We propose a shifting role of nutrition from support to therapy in GVHD by targeting gut microbiota.

Nutritional modulation of the gut microbiome in allogeneic hematopoietic stem cell transplantation recipients

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents a potentially curative strategy for many oncological and non-oncological diseases, but it is associated with marked morbidity and mortality. The disruption of gut microbiota (GM) eubiosis has been linked to major allo-HSCT complications, including infections and acute graft vs. host disease (aGvHD), and correlates with mortality. This increasing knowledge on the role of the GM in the allo-HSCT procedure has led to fascinating ideas for modulating the intestinal ecosystem in order to improve clinical outcomes. Nutritional strategies, either by changing the route of nutritional supplementation or by administering specific molecules, are increasingly being considered as cost- and risk-effective methods of modulating the GM. Nutritional support has also emerged in the past several years as a key feature in supportive care for allo-HSCT recipients, and deterioration of nutritional status is associated with decreased overall survival and higher complication rates during treatment. Herein we provide a complete overview focused on nutritional modulation of the GM in allo-HSCT recipients. We address how pre transplant diet could affect GM composition and its ability to withstand the upsetting events occurring during transplantation. We also provide a complete overview on the influence of the route of nutritional administration on the intestinal ecosystem, with a particular focus on the comparison between enteral and parenteral nutrition (PN). Moreover, as mounting evidence are showing how specific components of post-transplant diet, such as lactose, could drastically shape the GM, we will also summarize the role of prebiotic supplementation in the modulation of the intestinal flora and in allo-HSCT outcomes.

A Promising Insight: The Potential Influence and Therapeutic Value of the Gut Microbiota in GI GVHD

Allogeneic hematopoietic cell transplantation (allo-HSCT) is a reconstruction process of hematopoietic and immune functions that can be curative in patients with hematologic malignancies, but it carries risks of graft-versus-host disease (GVHD), thrombotic microangiopathy (TMA), Epstein–Barr virus (EBV) infection, cytomegalovirus infection, secondary hemophagocytic lymphohistiocytosis (sHLH), macrophage activation syndrome (MAS), bronchiolitis obliterans, and posterior reversible encephalopathy syndrome (PRES). Gastrointestinal graft-versus-host disease (GI GVHD), a common complication of allo-HSCT, is one of the leading causes of transplant-related death because of its high treatment difficulty, which is affected by preimplantation, antibiotic use, dietary changes, and intestinal inflammation. At present, human trials and animal studies have proven that a decrease in intestinal bacterial diversity is associated with the occurrence of GI GVHD. Metabolites produced by intestinal bacteria, such as lipopolysaccharides, short-chain fatty acids, and secondary bile acids, can affect the development of GVHD through direct or indirect interactions with immune cells. The targeted damage of GVHD on intestinal stem cells (ISCs) and Paneth cells results in intestinal dysbiosis or dysbacteriosis. Based on the effect of microbiota metabolites on the gastrointestinal tract, the clinical treatment of GI GVHD can be further optimized. In this review, we describe the mechanisms of GI GVHD and the damage it causes to intestinal cells and we summarize recent studies on the relationship between intestinal microbiota and GVHD in the gastrointestinal tract, highlighting the role of intestinal microbiota metabolites in GI GVHD. We hope to elucidate strategies for immunomodulatory combined microbiota targeting in the clinical treatment of GI GVHD.

Integrating the Synergy of the Gut Microbiome into Regenerative Medicine: Relevance to Neurological Disorders

A new paradigm of cell therapy-based approaches as a solution to several diseases caused by damage or loss of cells/tissues leading to organ failure heralded the birth of a new branch in medicine called regenerative medicine (RM), which was further fueled by in vitro cell expansion and tissue engineering (TE) technologies, including the ability to grow embryonic stem cells, induce pluripotent stem cells, and so on. RM addresses organ failure by repair, regeneration, or restoration, rejuvenation using cells, stem cells, or progenitor cells as tools having added cell-derived products also as a tool, and extracellular matrix component-based support, either direct or indirect (e.g., matrix induced autologous chondrocyte implantation) using scaffolds. Now, the main objective of RM is to solve the functional loss of cells that have evolved from cells as tools to cell-derived factors and scaffolds per se as tools. In this context, an important yet indispensable group of cells that constitute the major portion of the human body in terms of the number of cells having several essential roles to play, both directly and indirectly, starting from digestion and the immune system to the growing evidence of influencing neuronal function, aging, and carcinogenesis has been ignored. We would like to focus on these in this review as they should essentially be considered as a tool of RM, especially for neurological disorders for their vital role. What we are indicating is the second genome or the gut microbiome.

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 Impact of NLRP3 Activation on Hematopoietic Stem Cell Transplantation

NLR family pyrin domain-containing 3 (NLRP3) is an intracellular protein that after recognizing a broad spectrum of stressors, such as microbial motifs and endogenous danger signals, promotes the activation and release of the pro-inflammatory cytokines IL-1β and IL-18, thus playing an essential role in the innate immune response. Several blood cell types, including macrophages, dendritic cells, and hematopoietic stem and progenitor cells (HSPCs), express NLRP3, where it has been implicated in various physiological and pathological processes. For example, NLRP3 participates in the development and expansion of HSPCs, and their release from bone marrow into the peripheral blood has been implicated in certain hematological disorders including various types of leukemia. In addition, accumulating evidence indicates that activation of NLRP3 plays a pivotal role in the development of transplant complications in patients receiving hematopoietic stem cell transplantation (HSCT) including graft versus host disease, severe infections, and transplant-related mortality. The majority of these complications are triggered by the severe tissue damage derived from the conditioning regimens utilized in HSCT which, in turn, activates NLRP3 and, ultimately, promotes the release of proinflammatory cytokines such as IL-1β and IL-18. Here, we summarize the implications of NLRP3 in HSCT with an emphasis on the involvement of this inflammasome component in transplant complications.

Retinoic Acid Signaling Modulates Recipient Gut Barrier Integrity and Microbiota After Allogeneic Hematopoietic Stem Cell Transplantation in Mice

Graft-versus-host disease (GVHD) remains a major complication after allogeneic hematopoietic stem cell transplantation (HSCT). An impaired intestinal epithelial barrier is an important component of GVHD pathogenesis. However, contributing host factors that modulate mucosal barrier integrity during GVHD are poorly defined. We hypothesized that vitamin A and retinoic acid (RA) exert positive impacts on maintaining intestinal barrier function after HSCT, thus preventing or dampening GVHD severity. Unexpectedly, we found that exogenous RA increased intestinal permeability of recipient mice after allogeneic HSCT. Serum bacterial endotoxin levels were significantly higher in GVHD mice fed a vitamin A-high (VAH) diet compared to those fed a vitamin A-normal (VAN) diet, indicating a more compromised intestinal barrier function. Furthermore, VAH mice showed more severe lung GVHD with increased donor T cell infiltration in this tissue and died significantly faster than VAN recipients. 16S rRNA sequencing of fecal samples revealed significant differences in the diversity and composition of gut microbiota between VAN and VAH transplant recipients. Collectively, we show that retinoic acid signaling may negatively impact intestinal barrier function during GVHD. Mild vitamin A supplementation is associated with increased lung GVHD and more profound gut dysbiosis. Micronutrients such as vitamin A could modulate complications of allogeneic HSCT, which may be mediated by shaping gut microbiota.

Gut Microbiome Modulation and Faecal Microbiota Transplantation Following Allogenic Hematopoietic Stem Cell Transplantation

Nowadays, allogenic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy that is mainly recommended for hematologic malignancies. However, complications (such as graft-versus-host disease, mucositis, disease relapse, and infections) associated with the HSCT procedure contribute to the development of gut microbiota imbalance, gut-barrier disruption, and increased intestinal permeability. In the present narrative review, the crosstalk between gut microbiota products and intestinal homeostasis is discussed. Notably, gut-microbiota-related aspects have an impact on patients' clinical outcomes and overall survival. In accordance with the most recent published data, gut microbiota is crucial for the treatment effectiveness of many diseases, not only gastrointestinal cancers but also hematologic malignancies. Therefore, it is necessary to indicate a therapeutic method allowing to modulate gut microbiota in HSCT recipients. Currently, fecal microbiota transplantation (FMT) is the most innovative method used to alter/restore gut microbiota composition, as well as modulate its activity. Despite the fact that some previous data have shown promising results, the knowledge regarding FMT in HSCT is still strongly limited, except for the treatment of Clostridium difficile infection. Additionally, administration of prebiotics, probiotics, synbiotics, and postbiotics can also modify gut microbiota; however, this strategy should be considered carefully due to the high risk of fungemia/septicemia (especially in case of fungal probiotics).

Is it time to reconsider prophylactic antimicrobial use for hematopoietic stem cell transplantation? a narrative review of antimicrobials in stem cell transplantation

INTRODUCTION

Hematopoietic Stem Cell Transplantation (HSCT) is a life-saving procedure for multiple types of hematological cancer, autoimmune diseases, and genetic-linked metabolic diseases in humans. Recipients of HSCT transplant are at high risk of microbial infections that significantly correlate with the presence of graft-versus-host disease (GVHD) and the degree of immunosuppression. Infection in HSCT patients is a leading cause of life-threatening complications and mortality.

AREAS COVERED

This review covers issues pertinent to infection in the HSCT patient, including bacterial and viral infection; strategies to reduce GVHD; infection patterns; resistance and treatment options; adverse drug reactions to antimicrobials, problems of antimicrobial resistance; perturbation of the microbiome; the role of prebiotics, probiotics, and antimicrobial peptides. We highlight potential strategies to minimize the use of antimicrobials.

EXPERT OPINION

Measures to control infection and its transmission remain significant HSCT management policy and planning issues. Transplant centers need to consider carefully prophylactic use of antimicrobials for neutropenic patients. The judicious use of appropriate antimicrobials remains a crucial part of the treatment protocol. However, antimicrobials' adverse effects cause microbiome diversity and dysbiosis and have been shown to increase morbidity and mortality.

Fecal microbiota transplantation in the treatment of intestinal steroid-resistant graft-versus-host disease: two case reports and a review of the literature

Acute graft-versus-host disease (aGvHD) reduces the efficiency and safety of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In recent years, attempts have been made to transplant fecal microbiota from healthy donors to treat intestinal GvHD. This study presented two cases of patients undergoing allo-HSCT who were later selected for fecal microbiota transplantation (FMT). In the first patient, FMT resulted in the complete resolution of symptoms, whereas therapeutic efficacy was not achieved in the second patient. FMT eliminated drug-resistant pathogens, namely very drug-resistant Enterococcus spp., but not multidrug-resistant Acinetobacter baumannii or Candida spp. Further research is needed, particularly on the safety of FMT in patients with intestinal steroid-resistant GvHD and on the distant impact of transplanted microflora on the outcomes of allo-HSCT. FMT appears promising for the treatment of patients with steroid-resistant GvHD.

Nutritional Supplements and Complementary/Alternative Medications in Patients With Hematologic Diseases and Hematopoietic Stem Cell Transplantation

This perspective article discusses the various practices classified as complementary and alternative medicine (CAM) and reviews the benefits and uncertainties with respect to nutritional supplements in patients with hematological disease. It considers the high prevalence of CAM use especially among cancer survivors, particularly patients with hematologic malignancies and allogeneic stem cell transplant survivors, many of whom believe (because of extensive advertising) that supplements are anticancer/antitoxic agents, despite the paucity of evidence to support any benefit and the enormous cost to the individual. CAM constitutes various practices and nutritional behaviors including prayers, relaxation, spiritual healing, nutritional supplements, meditation, religious counseling, massage, and support groups. We highlighted the current literature regarding CAM practices and focused our discussion on the omnipresent nutritional supplements in particular to further expound on their benefits and adverse effects. As the number of survivors after HSCT increases over the next several years along with prevalence of CAM use, it becomes imperative to ascertain any beneficial potential, as well as toxicities associated with CAM use in this population.

A single strain of Bacteroides fragilis protects gut integrity and reduces GVHD

Graft-versus-host disease (GVHD) is a pathological process caused by an exaggerated donor lymphocyte response to host antigens after allogeneic hematopoietic cell transplantation (allo-HCT). Donor T cells undergo extensive clonal expansion and differentiation, which culminate in damage to recipient target organs. Damage to the gastrointestinal tract is a main contributor to morbidity and mortality. The loss of diversity among intestinal bacteria caused by pretransplant conditioning regimens leads to an outgrowth of opportunistic pathogens and exacerbated GVHD after allo-HCT. Using murine models of allo-HCT, we found that an increase of Bacteroides in the intestinal microbiota of the recipients was associated with reduced GVHD in mice given fecal microbial transplantation. Administration of Bacteroides fragilis through oral gavage increased gut microbiota diversity and beneficial commensal bacteria and significantly ameliorated acute and chronic GVHD development. Preservation of gut integrity following B. fragilis exposure was likely attributed to increased short chain fatty acids, IL-22, and regulatory T cells, which in turn improved gut tight junction integrity and reduced inflammatory cytokine production of pathogenic T cells. The current study provides a proof of concept that a single strain of commensal bacteria can be a safe and effective means to protect gut integrity and ameliorate GVHD after allo-HCT.

Fecal Microbiota Transplantation in Allogeneic Hematopoietic Stem Cell Transplantation Recipients: A Systematic Review

The disruption of gut microbiota eubiosis has been linked to major complications in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Various strategies have been developed to reduce dysbiosis and related complications. Fecal microbiota transplantation (FMT) consists of the infusion of fecal matter from a healthy donor to restore impaired intestinal homeostasis, and could be applied in the allo-HSCT setting. We conducted a systematic review of studies addressing the use of FMT in allo-HSCT patients. In the 23 papers included in the qualitative synthesis, FMT was used for the treatment of recurrent Clostridioides difficile infections or as a therapeutic strategy for steroid-resistant gut aGvHD. FMT was also performed with a preventive aim (e.g., to decolonize from antibiotic-resistant bacteria). Additional knowledge on the biological mechanisms underlying clinical findings is needed in order to employ FMT in clinical practice. There is also concern regarding the administration of microbial consortia in immune-compromised patients with altered gut permeability. Therefore, the safety profile and efficacy of the procedure must be determined to better assess the role of FMT in allo-HSCT recipients.

Intestinal Regulatory T Cells

Mucosal surfaces are distinctive sites exposed to environmental, dietary, and microbial antigens. Particularly in the gut, the host continuously actively adapts via complex interactions between the microbiota and dietary compounds and immune and other tissue cells. Regulatory T cells (Tregs) are critical for tuning the intestinal immune response to self- and non-self-antigens in the intestine. Its importance in intestinal homeostasis is illustrated by the onset of overt inflammation caused by deficiency in Treg generation, function, or stability in the gut. A substantial imbalance in Tregs has been observed in intestinal tissue during pathogenic conditions, when a tightly regulated and equilibrated system becomes dysregulated and leads to unimpeded and chronic immune responses. In this chapter, we compile and critically discuss the current knowledge on the key factors that promote Treg-mediated tolerance in the gut, such as those involved in intestinal Treg differentiation, specificity and suppressive function, and their immunophenotype during health and disease. We also discuss the current state of knowledge on Treg dysregulation in human intestine during pathological states such as inflammatory bowel disease (IBD), necrotizing enterocolitis (NEC), graft-versus-host disease (GVHD), and colorectal cancer (CRC), and how that knowledge is guiding development of Treg-targeted therapies to treat or prevent intestinal disorders.

Treatment of intestinal graft-versus-host disease with unrelated donor fecal microbiota transplantation capsules: A case report

INTRODUCTION

Fecal microbiota transplantation (FMT), administering fecal suspensions via a nasoduodenal tube, has achieved a promising effect in the treatment of intestinal graft-versus-host disease (GvHD) in some pilot studies. In this study, oral FMT capsules from unrelated donor were used for the first time in the treatment of intestinal GvHD. Patient concerns: A 31-year-old male who was diagnosed as "myelodysplastic syndromes with excess blasts II" (intermediate risk 2 of international prognostic scoring system) received human leukocyte antigen -matched sibling donor allogeneic hematopoietic stem cell transplantation. The patient developed diarrhea, vomiting, and bloody stool on 28 days after transplantation.

DIAGNOSIS

Intestinal acute GvHD was diagnosed clinically with histological confirmation by colonoscopy and pathological biopsy.

INTERVENTIONS

This patient was treated with first cycle of oral FMT capsules after failure to initial treatment of methylprednisolone (2 mg/kg/d) combined with recombinant human tumor necrosis factor-α receptorII: IgG Fc fusion protein (25 mg, biw). The symptoms of intestinal GvHD were relieved but recurred 11 days later. Second cycle of oral FMT capsules was carried out.

OUTCOMES

After 2 cycles of fecal bacteria transplantation, intestinal GvHD was gradually controlled and did not recur again during the 2-month follow-up. The diversity and structure of the intestinal flora after FMT was closer to that of healthy donors than that before.

CONCLUSION

Our case showed oral FMT capsules could be used as a treatment option for corticosteroid refractory intestinal GvHD. Further studies are warranted to assess the clinical efficacy and safety of oral FMT capsules in the treatment of intestinal GvHD.

RATIONALE

Fecal microbiota transplantation (FMT), administering fecal suspensions via a nasoduodenal tube, has achieved a promising effect in the treatment of intestinal graft-versus-host disease (GvHD) in some pilot studies. In this study, oral FMT capsules from unrelated donor were used for the first time in the treatment of intestinal GvHD.

PATIENT CONCERNS

A 31-year-old male who was diagnosed as "myelodysplastic syndromes with excess blasts II" (intermediate risk 2 of international prognostic scoring system) received human leukocyte antigen -matched sibling donor allogeneic hematopoietic stem cell transplantation. The patient developed diarrhea, vomiting, and bloody stool on 28 days after transplantation.

DIAGNOSES

Intestinal acute GvHD was diagnosed clinically with histological confirmation by colonoscopy and pathological biopsy.

INTERVENTIONS

This patient was treated with first cycle of oral FMT capsules after failure to initial treatment of methylprednisolone (2 mg/kg/d) combined with recombinant human tumor necrosis factor-a receptorII: IgG Fc fusion protein (25 mg, biw). The symptoms of intestinal GvHD were relieved but recurred 11 days later. Second cycle of oral FMT capsules was carried out.

OUTCOMES

After 2 cycles of fecal bacteria transplantation, intestinal GvHD was gradually controlled and did not recur again during the 2-month follow-up. The diversity and structure of the intestinal flora after FMT was closer to that of healthy donors than that before.

CONCLUSION

Our case showed oral FMT capsules could be used as a treatment option for corticosteroid refractory intestinal GvHD. Further studies are warranted to assess the clinical efficacy and safety of oral FMT capsules in the treatment of intestinal GvHD.

LESSONS

There is still a possibility of recurrence after the treatment of GvHD with capsule fecal microbiota transplantation. How to optimize the dosage and treatment course of fecal microbiota capsule administration needs further exploration.

Challenging and Practical Aspects of Nutrition in Chronic Graft-versus-Host Disease

There is a paucity of information about nutrition in chronic graft-versus-host disease (GVHD). The role of nutrition is important because malnutrition is strongly associated with severe chronic GVHD manifestations. There is a high prevalence of metabolic syndrome and osteoporosis in this setting. Here we review the literature, describe main aspects of nutrition and discuss macronutrients (ie, vitamins), micronutrients (ie, Mg, Zn, Ca, and K) and supplements (probiotics and omega 3 fatty acids). A search was carried out in March 2020 using PubMed. Databases were screened for searching terms in titles and abstracts referring to chronic GVHD, nutrition intervention, protein, and body composition. Data were extracted for the following outcomes: nutrition, nutrition intervention, chronic GVHD, nutrition deficiencies, diet, vitamin, dry eye, probiotic, protein, and body composition. In this report, we summarize interventional nutrition studies reported in oncology and metabolic syndrome settings and describe our nutritional clinical practice in hematopoietic cell transplantation and chronic GVHD. The impact of nutrition evaluation and intervention on muscle mass loss, dry eye, dysgeusia, metabolic syndrome, osteoporosis, and comorbidities associated with chronic GVHD need to be studied prospectively.

Clostridium difficile in Immunocompromised Hosts: A Review of Epidemiology, Risk Factors, Treatment, and Prevention

Clostridium difficile is a significant pathogen in healthcare today, impacting both hospitalized and community-based patients. Immunocompromised patients experience a high incidence of C. difficile infection, ranging from 6% to 33% in the hematology-oncology population and up to 23% among lung transplant recipients, and have a rate of 7.1-8.3 cases per 1000 patient-years in patients with human immunodeficiency virus (HIV). Recurrence of C. difficile infections among immunocompromised patients is also high, with rates up to 40% in both the hematology-oncology population and solid organ transplant recipients. This higher incidence of C. difficile infection and recurrence is believed to be secondary to frequent antimicrobial use, suppressed immune function, increased exposure to healthcare settings, and higher prevalence of C. difficile colonization. This review summarizes published data describing the epidemiology, risk factors for acquisition and infection, treatment, and prevention of C. difficile in hematology-oncology, solid organ transplant, and HIV-infected patients.

Microbiome-intestine cross talk during acute graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (allo-SCT) offers cure for a variety of conditions, in particular, but not limited to, hematologic malignancies. However, it can be associated with life-threatening complications, including graft-versus-host disease (GVHD) and infections, which are factors limiting its widespread use. Technical advances in the field of microbiome research have allowed for a better understanding of the microbial flora of the human intestine, as well as dissection of their interactions with the host immune system in allo-SCT and posttransplant complications. There is growing evidence that the commensal microbiome is frequently dysregulated following allo-SCT and that this dysbiosis can predispose to adverse clinical outcomes, especially including acute intestinal GVHD and reduced overall survival. In this review, we discuss the interactions between the microbiome and the components of the immune system that play a major role in the pathways leading to the inflammatory state of acute intestinal GVHD. We also discuss the microbiome-centered strategies that have been devised or are actively being investigated to improve the outcomes of allo-SCT patients in regard to acute intestinal GVHD.

Microbiome and diversity indices during blood stem cells transplantation - new perspectives?

OBJECTIVE

The human body is colonized by bacteria, fungi and viruses. Resident commensal bacteria are a fundamental line of resistance to colonization by exogenous microbes. They actively regulate the production of nutrients by the host through a negative feedback mechanism, in order to prevent the availability of nutrients for potential pathogens. While only a small fraction of these microorganism may be pathogenic, the relationship between host and commensal microbiome is now studied as a whole, impacting several aspects of the host biology. Some studies have made clear the progresses in examining the role of microbiome on transplants and graft versus host disease (GVHD) severity and its pathogenesis: the risk of complications from allogenic hematopoietic stem cells transplantation (HSCT) is greater with the highest mortality if a patient has a lower bacterial diversity in the gut prior to the transplantation process beginning. Microbiota-associated molecular patterns are directly recognized by pathogen recognition receptors. The development of molecular methods has greatly expanded our knowledge of the composition and function of the microbiome in health and disease, shortening the response times vs. microbiological culture tests. The gut flora can make the difference when it comes to allo-HSCT. The aim of the study was to monitor microbiome of 10 children during allo-HSCT.

METHODS

Oral specimens and gut faecal microbiome (100 grams) samples were collected at 2, 16, 24 days. The samples were analysed by polymerase chain reaction and primary sequencing was done. To calculate the biodiversity of microbiome the Shannon index and the Observed species index were chosen.

RESULTS

Our study suggests some differences in the diversity indices (DIs) in 5 children affected by GVHD vs. not affected. The DIs in oral and faecal specimens show in all patients a diminution in the post-transplant phase with an improvement in species diversity after 16 days from the transplant. The Observed species index in faeces specimens after 16 days was higher in patients which had not GVHD; moreover, patients with GVHD showed a deterioration at 24 days. Oral specimens after 24 days showed a parallel trend in the two groups. The Shannon index shows a downward trend in faeces specimens of the children with GVHD at 24 days; the children without GVHD recover a good trend of entropy. Oral specimens at 24 days show low entropy in the two groups. Very aggressive bacterial species as Cronobacter and Routella in the faeces specimens of a child had not serious consequences for disease status: Cronobacter were not present 24 days after transplantation.

CONCLUSIONS

The data show the microbial metabolome could have an impact on patients with GVHD vs. no GVHD. A better understanding of the role of the oral and gut microbiome in GVHD can give directions to move towards the development of innovative approaches for preventing GVHD following allo-HCT, reducing also antibiotic therapy.

Safety of Probiotics Among High-Risk Pediatric Hematopoietic Stem Cell Transplant Recipients

INTRODUCTION

Increased diversity of the intestinal microbiome has been significantly associated with lower mortality after hematopoietic stem cell transplant (HSCT). Probiotics, such as Lactobacillus species with defined probiotic potential, may have beneficial properties including restoration of commensal species to the intestinal tract, anti-microbial effects, and healing of the intestinal mucosa. However, the use of probiotics in immune-compromised patients raises concerns, specifically regarding the risk for possible Lactobacillus bacteremia. Risk of bacteremia is an even greater concern in HSCT patients with breakdown of mucosal barriers, specifically patients with Clostridium difficile infection (CDI) or gastrointestinal graft-versus-host disease (GVHD). Minimal data have been reported on the safety of probiotics in these high-risk HSCT populations.

METHODS

We performed a retrospective study of allogeneic HSCT recipients at our institution between 2011 and 2016, and identified 14 patients (median age 7 years) prescribed probiotics, 10 of whom received probiotics prior to day 100 after HSCT.

RESULTS

Eight of ten patients were diagnosed with acute GVHD, four of whom (40%) specifically had acute GVHD involving the gastrointestinal tract. Five patients (50%) on probiotics prior to day 100 were diagnosed with CDI (median onset at day 13 post-transplant). There were no cases of Lactobacillus bacteremia, including in patients with GVHD or CDI.

CONCLUSION

This small case series supports the safe use of probiotics in a high-risk population of pediatric HSCT patients with compromised intestinal mucosal integrity. Further studies are needed to determine if probiotics have benefit in preventing and treating gastrointestinal GVHD or CDI.

The microbiome and ophthalmic disease

IMPACT STATEMENT

This review describes a growing body of research on relationships between the microbiome and eye disease. Several groups have investigated the microbiota of the ocular surface; dysregulation of this delicate ecosystem has been associated with a variety of pro-inflammatory states. Other research has explored the effects of the gastrointestinal microbiota on ophthalmic diseases. Characterizing the ways these microbiotas influence ophthalmic homeostasis and pathogenesis may lead to research on new techniques for managing ophthalmic disease.

Modulating the microbiome to improve therapeutic response in cancer

Although novel therapies, including immunotherapy, have dramatically improved outcomes for many patients with cancer, overall outcomes are heterogeneous and existing biomarkers do not reliably predict response. To date, predictors of response to cancer therapy have largely focused on tumour-intrinsic features; however, there is growing evidence that other host factors (eg, host genomics and the microbiome) can substantially affect therapeutic response. The microbiome, which refers to microbiota within a host and their collective genomes, is becoming increasingly recognised for its influence on host immunity, as well as therapeutic responses to cancer treatment. Importantly, microbiota can be modified via several different strategies, affording new angles in cancer treatment to improve outcomes. In this Review, we examine the evidence on the role of the microbiome in cancer and therapeutic response, factors that influence and shape host microbiota, strategies to modulate the microbiome, and present key unanswered questions to be addressed in ongoing and future research.

Hematopoietic Stem Cell Transplantation From Unrelated Donors in 2 Cases of Interleukin-10 Receptor Deficiency: Is Surgery Not a Requirement?

Mutations in interleukin-10 and its receptors cause infantile inflammatory bowel disease (IBD), a hyperinflammatory disorder characterized by severe, treatment-refractory colitis, multiple abscesses, and enterocutaneous fistulas. Patients with infantile IBD often require several surgical interventions, including complete colectomy, and hematopoietic stem cell transplantation is currently the only known medical therapy. Traditionally, operative management has been preferred before stem cell transplantation because of the latter's increased susceptibility to procedural complications; however, surgical intervention could be delayed, and possibly reconsidered, because our 2 patients with infantile IBD demonstrated a rapid response to treatment via engraftment.

Optimization of nutrition during allogeneic hematologic stem cell transplantation

PURPOSE OF REVIEW

Malnutrition before and during hematopoietic stem cell transplantation (HSCT) is an independent risk factor for mortality in patients undergoing hematopoietic stem cell transplantation. Yet, optimal use of nutritional support to improve outcomes remains controversial. Our aim was to do an up-to-date literature review regarding nutritional therapy in allogeneic HSCT, the neutropenic diet and the use of immunonutrients.

RECENT FINDINGS

Several observational studies find malnutrition to be associated with poor outcome, increased complications and lower overall survival. There are, however, few interventional trials proving the benefits of nutritional therapy in this population compared with no nutritional treatment. Regarding routes of treatment, studies suggested that parenteral nutrition is associated with higher risk for complications compared with enteral nutrition. Whether the use of specific formulas, such as immunonutrition, has a beneficial effect on clinical outcome is not established yet. Strict use of neutropenic diets did not show a reduction in infection risk and clinical outcome, and can no longer be recommended.

SUMMARY

Our updated search confirms that malnutrition is a strong negative predictor for outcome, yet optimal use of nutritional interventions to prevent or treat malnutrition remains ill-defined. There is need for larger randomized trials to better address these issues in the future.

Gut microbiota injury in allogeneic haematopoietic stem cell transplantation

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is considered to be the strongest curative immunotherapy for various malignancies (primarily, but not limited to, haematologic malignancies). However, application of allo-HSCT is limited owing to its life-threatening major complications, such as graft-versus-host disease (GVHD), relapse and infections. Recent advances in large-scale DNA sequencing technology have facilitated rapid identification of the microorganisms that make up the microbiota and evaluation of their interactions with host immunity in various diseases, including cancer. This has resulted in renewed interest regarding the role of the intestinal flora in patients with haematopoietic malignancies who have received an allo-HSCT and in whether the microbiota affects clinical outcomes, including GVHD, relapse, infections and transplant-related mortality. In this Review, we discuss the potential role of intestinal microbiota in these major complications after allo-HSCT, summarize clinical trials evaluating the microbiota in patients who have received allo-HSCT and discuss how further studies of the microbiota could inform the development of strategies that improve outcomes of allo-HSCT.

Third-party fecal microbiota transplantation following allo-HCT reconstitutes microbiome diversity

We hypothesized that third-party fecal microbiota transplantation (FMT) may restore intestinal microbiome diversity after allogeneic hematopoietic cell transplantation (allo-HCT). In this open-label single-group pilot study, 18 subjects were enrolled before allo-HCT and planned to receive third-party FMT capsules. FMT capsules were administered no later than 4 weeks after neutrophil engraftment, and antibiotics were not allowed within 48 hours before FMT. Five patients did not receive FMT because of the development of early acute gastrointestinal (GI) graft-versus-host disease (GVHD) before FMT (n = 3), persistent HCT-associated GI toxicity (n = 1), or patient decision (n = 1). Thirteen patients received FMT at a median of 27 days (range, 19-45 days) after HCT. Participants were able to swallow and tolerate all FMT capsules, meeting the primary study endpoint of feasibility. FMT was tolerated well, with 1 treatment-related significant adverse event (abdominal pain). Two patients subsequently developed acute GI GVHD, with 1 patient also having concurrent bacteremia. No additional cases of bacteremia occurred. Median follow-up for survivors is 15 months (range, 13-20 months). The Kaplan-Meier estimates for 12-month overall survival and progression-free survival after FMT were 85% (95% confidence interval, 51%-96%) and 85% (95% confidence interval, 51%-96%), respectively. There was 1 nonrelapse death resulting from acute GI GVHD (12-month nonrelapse mortality, 8%; 95% confidence interval, 0%-30%). Analysis of stool composition and urine 3-indoxyl sulfate concentration indicated improvement in intestinal microbiome diversity after FMT that was associated with expansion of stool-donor taxa. These results indicate that empiric third-party FMT after allo-HCT appears to be feasible, safe, and associated with expansion of recipient microbiome diversity. This trial was registered at www.clinicaltrials.gov as #NCT02733744.

Impact of route and adequacy of nutritional intake on outcomes of allogeneic haematopoietic cell transplantation for haematologic malignancies

BACKGROUND

Allogeneic haematopoietic cell transplantation (HCT) is often associated with poor oral intake due to painful mucositis and gastrointestinal sequalae that occur following a preparative regimen of intensive chemotherapy and/or total body radiation. Although attractive to assume that optimal nutrition improves HCT outcomes, there are limited data to support this. It is also unclear whether artificial nutrition support should be provided as enteral tube feeding or parenteral nutrition (PN).

METHODS

We analysed day-100 non-relapse mortality (NRM), incidence of acute graft-versus-host disease (GvHD), acute gastrointestinal GvHD, 5-year survival and GvHD-free/relapse-free survival (GRFS) according to both route and adequacy of nutritional intake prior to neutrophil engraftment, together with other known prognostic factors, in a retrospective cohort of 484 patients who underwent allogeneic HCT for haematologic malignancy between 2000 and 2014.

RESULTS

Multivariate analyses showed increased NRM with inadequate nutrition (hazard ratio (HR) 4.1; 95% confidence interval (CI) 2.2-7.2) and adequate PN (HR 2.9; 95% CI 1.6-5.4) compared to adequate enteral nutrition (EN) both P < .001. There were increased incidences of gastrointestinal GvHD of any stage and all GvHD ≥ grade 2 in patients who received PN (odds ratio (OR) 2.0; 95% CI 1.2-3.3; P = .006, and OR 1.8; 95% CI 1.1-3.0; P = .018, respectively), compared to adequate EN. Patients who received adequate PN and inadequate nutrition also had reduced probabilities of survival and GRFS at 5 years.

CONCLUSION

Adequate EN during the early transplantation course is associated with reduced NRM, improved survival and GRFS at 5 years. Furthermore, adequate EN is associated with lower incidence of overall and gut acute GvHD than PN, perhaps because of its ability to maintain mucosal integrity, modulate the immune response to intensive chemo/radiotherapy and support the gastrointestinal tract environment, including gut microflora.

Gut microbiota and its implications in small bowel transplantation

The gut microbiota is mainly composed of a diverse population of commensal bacterial species and plays a pivotal role in the maintenance of intestinal homeostasis, immune modulation and metabolism. The influence of the gut microbiota on solid organ transplantation has recently been recognized. In fact, several studies indicated that acute and chronic allograft rejection in small bowel transplantation (SBT) is closely associated with the alterations in microbial patterns in the gut. In this review, we focused on the recent findings regarding alterations in the microbiota following SBTand the potential roles of these alterations in the development of acute and chronic allograft rejection. We also reviewed important advances with respect to the interplays between the microbiota and host immune systems in SBT. Furthermore, we explored the potential of the gut microbiota as a microbial marker and/or therapeutic target for the predication and intervention of allograft rejection and chronic dysfunction. Given that current research on the gut microbiota has become increasingly sophisticated and comprehensive, large cohort studies employing metagenomic analysis and multivariate linkage should be designed for the characterization of host-microbe interaction and causality between microbiota alterations and clinical outcomes in SBT. The findings are expected to provide valuable insights into the role of gut microbiota in the development of allograft rejection and other transplant-related complications and introduce novel therapeutic targets and treatment approaches in clinical practice.

Changes in intestinal microbiota and their effects on allogeneic stem cell transplantation

The human intestinal microbiota is essential for microbial homeostasis, regulation of metabolism, and intestinal immune tolerance. Rapidly evolving understanding of the importance of the microbiota implicates changes in the composition and function of intestinal microbial communities in an assortment of systemic conditions. Complications following allogeneic stem cell transplant now join the ever-expanding list of pathologic states regulated by intestinal microbiota. Dysbiosis, or disruption of the normal ecology of this microbiome, has been directly implicated in the pathogenesis of entities such as Clostridium difficile infections, graft-versus-host disease (GVHD), and most recently disease relapse, all of which are major causes of morbidity and mortality in patients undergoing allogeneic stem cell transplant. In this review, we elucidate the key origins of microbiotic alterations and discuss how dysbiosis influences complications following allogeneic stem cell transplant. Our emerging understanding of the importance of a balanced and diverse intestinal microbiota is prompting investigation into the appropriate treatment of dysbiosis, reliable and early detection of such, and ultimately its prevention in patients to improve the outcome following allogeneic hematopoietic stem cell transplant.

Targeted molecular ablation of cancer stem cells for curing gastrointestinal cancers

Abundance of the ATPase-binding cassette (ABC) transporters and deranged self-renewal pathways characterize the presence of cancer stem cells (CSCs) in gastrointestinal cancers (GI cancers), which play crucial roles in tumorigenesis, chemotherapy resistance, tumor recurrence, and cancer metastasis. Therefore, in order to ensure high cure rates, chemoquiescence, CSCs should be ablated. Recent advances in either understanding CSCs or biomarker identification enable scientists to develop techniques for ablating CSCs and clinicians to provide cancer cure, especially in GI cancers characterized by inflammation-driven carcinogenesis. Areas covered: A novel approach to ablate CSCs in GI cancers, including esophageal, gastric, and colon cancers, is introduced along with explored underlying molecular mechanisms. Expert commentary: Though CSC ablation is still in the empirical stages and not in clinical practice, several strategies for ablating CSCs in GI cancers had been published, proton-pump inhibitors (PPIs) that regulate the membrane-bound ABC transporters, which underlie drug resistance; chloroquine (CQ) that inhibits autophagy, which is responsible for tumor survival; Hedgehog/Wnt/Notch inhibitors that influence the underlying stem-cell growth, and some natural products including Korean red ginseng, cancer-preventive kimchi, Artemisia extract, EGCG from green tea, and walnut extracts.

Associations between acute gastrointestinal GvHD and the baseline gut microbiota of allogeneic hematopoietic stem cell transplant recipients and donors

Growing evidence suggests that host-microbiota interactions influence GvHD risk following allogeneic hematopoietic stem cell transplant. However, little is known about the influence of the transplant recipient's pre-conditioning microbiota nor the influence of the transplant donor's microbiota. Our study examines associations between acute gastrointestinal GvHD (agGvHD) and 16S rRNA fecal bacterial profiles in a prospective cohort of N=57 recipients before preparative conditioning, as well as N=22 of their paired HLA-matched sibling donors. On average, recipients had lower fecal bacterial diversity (P=0.0002) and different phylogenetic membership (UniFrac P=0.001) than the healthy transplant donors. Recipients with lower phylogenetic diversity had higher overall mortality rates (hazard ratio=0.37, P=0.008), but no statistically significant difference in agGvHD risk. In contrast, high bacterial donor diversity was associated with decreased agGvHD risk (odds ratio=0.12, P=0.038). Further investigation is warranted as to whether selection of hematopoietic stem cell transplant donors with high gut microbiota diversity and/or other specific compositional attributes may reduce agGvHD incidence, and by what mechanisms.

Pharmacokinetics-directed Intravenous Busulfan Combined With High-dose Melphalan and Bortezomib as a Conditioning Regimen for Patients With Multiple Myeloma

BACKGROUND

High-dose chemotherapy followed by autologous stem cell transplantation (ASCT) has a well-established role in the treatment of patients with multiple myeloma. Melphalan 200 mg/m² (Mel200) is the most commonly used preparative regimen. Several studies have provided evidence for potential synergism and safety when combining bortezomib (Btz) or busulfan (Bu) with melphalan (Mel).

PATIENTS AND METHODS

We conducted a prospective phase II study to investigate the safety and efficacy of conditioning with pharmacokinetics (PK)-directed intravenous (IV) Bu with Btz and Mel. Bu dosing was adjusted to target a total area under the curve (AUC) of 20,000 μM × min. Patients received Btz (1 mg/m² × 4 doses) and Mel (140 mg/m²).

RESULTS

A total of 19 subjects were enrolled. Their median age was 55 years, and the median follow-up period was 23.7 months. PK testing resulted in 86% of patients achieving an estimated total AUC of 20,000 ± 2500 μM × min. The overall response rate (ORR) at day +100 after ASCT was 100% in the evaluable patients, with 11% of patients achieving a complete response. The 2-year progression-free survival rate was 57.9% (95% confidence interval [CI], 38%-89%), and the 2-year overall survival rate was 88.5% (95% CI, 76%-100%). The most common grade 3 and 4 toxicities were febrile neutropenia, dysphagia/odynophagia, and oral mucositis. No case of hepatic sinusoidal obstruction syndrome developed. One treatment-related mortality occurred before day +100.

CONCLUSION

A preparative regimen of PK-directed IV Bu with Btz and Mel led to an ORR of 100% with acceptable toxicity and should be considered for direct comparison with the Mel200 regimen in future trials.

Revisiting nutritional support for allogeneic hematologic stem cell transplantation-a systematic review

In 2009, the American Society of Parenteral and Enteral Nutrition and its European counterpart (Euopean Society for Parenteral and Enteral Nutrition) published guidelines regarding nutritional support of patients with hematologic stem cell transplantation. Our aim was to do an up-to-date literature review regarding benefit of nutritional interventions and treatment recommendations. We searched MEDLINE, EMBASE and Cochrane Library for interventional and observational clinical studies. We extracted data based on a predefined case report form and assessed bias. Out of 459 potential abstracts, 13 studies of mostly moderate quality with a total of 18 167 patients were included. Two very large trials reported negative associations of malnutrition and survival, transplant-related mortality and relapse risk. Some trials found enteral nutrition (EN) to be as effective as parenteral nutrition (PN) with lower complication rates. In addition, EN was associated with better survival, less acute GvHD and faster neutrophil recovery. A neutropenic diet was not superior regarding overall survival, but in contrast resulted in higher infection risk. Current moderate quality studies show negative associations of malnutrition and clinical outcomes, with EN being superior to PN. There was no benefit of neutropenic diets. Large, randomized controlled studies are needed to better understand optimal nutritional support in this patient population.