Clinical effects and applications of the gut microbiome in hematologic malignancies

Changes in the intestinal microbiota of multiple myeloma patients living in high‑altitude and cold regions analyzed using 16s rRNA high‑throughput sequencing

Multiple myeloma (MM) is a plasma cell clonal disease and these plasma cells can survive in the gut. The intestinal microbiota is a complex ecosystem and its dysfunction can release persistent stimulus signals that trigger genetic mutations and clonal evolution in the gut. The present study analyzed the intestinal microbiota in fecal samples of MM patients in high-altitude and cold regions of China using 16s rRNA sequencing and analyzed significantly enriched species at the phylum and genus levels. Although no significant difference in the alpha diversity was observed between the MM and control groups, a significant difference was noted in the beta diversity. A total of 15 significant differential bacteria at the genus level were found between the two groups, among which Bacteroides, Streptococcus, Lactobacillus and Alistipes were significantly enriched in the MM group. The present study also constructed a disease diagnosis model using Random Forest analysis and verified its accuracy using receiver operating characteristic analysis. In addition, using correlation analysis, it demonstrated that the composition of the intestinal microbiota in patients with MM was associated with complement levels. Notably, the present study predicted that the signaling and metabolic pathways of the intestinal microbiota affected MM progression through Kyoto Encyclopedia of Genes and Genomes functional analysis. The present study provides a new approach for the prevention and treatment of MM, in which the intestinal microbiota may become a novel therapeutic target for MM.

Effects of immune cells in mediating the relationship between gut microbiota and myelodysplastic syndrome: a bidirectional two-sample, two-step Mendelian randomization study

BACKGROUND

The definitive establishment of a causal relationship between gut microbiota and myelodysplastic syndrome (MDS) has not been achieved. Furthermore, the involvement of immune cells in mediating the connection between gut microbiota and MDS is presently unclear.

METHODS

To elucidate the bidirectional correlation between gut microbiota and MDS, as well as to investigate the mediating role of immune cells, a bidirectional two-sample, two-step Mendelian randomization (MR) study was conducted. Summary statistics were obtained from genome-wide association studies (GWAS), including MDS (456,348 individuals), gut microbiota (18,340 individuals), and 731 immune cells signatures (3757 individuals).

RESULTS

Genetically predicted eight gut microbiota traits were significantly associated with MDS risk, but not vice versa. Through biological annotation of host-microbiome shared genes, we found that immune regulation may mediate the impact of gut microbiota on MDS. Subsequently, twenty-three immunophenotypes that exhibited significant associations with MDS risk and five of these immunophenotypes were under the causal influence of gut microbiota. Importantly, the causal effects of gut microbiota on MDS were significantly mediated by five immunophenotypes, including CD4 +T cell %leukocyte, CD127 on CD45RA - CD4 not regulatory T cell, CD45 on CD33 + HLA DR + WHR, CD33 on basophil, and Monocyte AC.

CONCLUSIONS

Gut microbiota was causally associated with MDS risk, and five specific immunophenotypes served as potential causal mediators of the effect of gut microbiota on MDS. Understanding the causality among gut microbiota, immune cells and MDS is critical in identifying potential targets for diagnosis and treatment.

Association of proton pump inhibitor use with survival and adverse effects outcomes in patients with multiple myeloma: pooled analysis of three clinical trials

Proton pump inhibitors (PPIs) are commonly used in cancer patients, but their impact on treatment outcomes in multiple myeloma (MM) patients remains unclear. This study investigated the association of PPI use with survival and adverse effects in MM patients across three randomized-control trials initiating daratumumab, lenalidomide, or bortezomib combination treatments. Cox proportional hazard analysis and logistic regression were employed to assess the associations with treatment outcomes, while adjusting for age, sex, weight, MM international staging system stage, ECOG-performance status, comorbidity count, and presence of gastrointestinal disorders. Pooled data involving 1804 patients revealed that 557 (32%) used PPIs at baseline. PPI use was independently associated with worse overall survival (adjusted HR [95% CI] 1.32 [1.08-1.62], P = 0.007) and grade ≥ 3 adverse events (adjusted OR [95% CI] 1.39 [1.03-1.88], P = 0.030). However, the association with progression-free survival did not reach statistical significance (adjusted HR [95% CI] 1.14 [0.97-1.33], P = 0.112). Findings were consistent across trials and treatment arms. PPI use was identified as a negative prognostic factor in MM patients, potentially enhancing clinical decisions regarding its use. Further research is needed to fully comprehend the impacts and safety of PPI use in MM patients.

The Role of the Gut Microbiome in Hematological Cancers

Humans are in a complex symbiotic relationship with a wide range of microbial organisms, including bacteria, viruses, and fungi. The evolution and composition of the human microbiome can be an indicator of how it may affect human health and susceptibility to diseases. Microbiome alteration, termed as dysbiosis, has been linked to the pathogenesis and progression of hematological cancers. A variety of mechanisms, including epithelial barrier disruption, local chronic inflammation response trigger, antigen dis-sequestration, and molecular mimicry, have been proposed to be associated with gut microbiota. Dysbiosis may be induced or worsened by cancer therapies (such as chemotherapy and/or hematopoietic stem cell transplantation) or infection. The use of antibiotics during treatment may also promote dysbiosis, with possible long-term consequences. The aim of this review is to provide a succinct summary of the current knowledge describing the role of the microbiome in hematological cancers, as well as its influence on their therapies. Modulation of the gut microbiome, involving modifying the composition of the beneficial microorganisms in the management and treatment of hematological cancers is also discussed. Additionally discussed are the latest developments in modeling approaches and tools used for computational analyses, interpretation and better understanding of the gut microbiome data.

Gut microbiota alterations induced by intensive chemotherapy in acute myeloid leukaemia patients are associated with gut barrier dysfunction and body weight loss

BACKGROUND & AIMS

Acute myeloid leukaemia (AML) chemotherapy has been reported to impact gut microbiota composition. In this study, we investigated using a multi -omics strategy the changes in the gut microbiome induced by AML intense therapy and their association with gut barrier function and cachectic hallmarks.

METHODS

10 AML patients, allocated to standard induction chemotherapy (SIC), were recruited. Samples and data were collected before any therapeutic intervention (T0), at the end of the SIC (T1) and at discharge (T4). Gut microbiota composition and function, markers of inflammation, metabolism, gut barrier function and cachexia, as well as faecal, blood and urine metabolomes were assessed.

RESULTS

AML patients demonstrated decreased appetite, weight loss and muscle wasting during hospitalization, with an incidence of cachexia of 50%. AML intensive treatment transiently impaired the gut barrier function and led to a long-lasting change of gut microbiota composition characterized by an important loss of diversity. Lactobacillaceae and Campylobacter concisus were increased at T1 while Enterococcus faecium and Staphylococcus were increased at T4. Metabolomics analyses revealed a reduction in urinary hippurate and faecal bacterial amino acid metabolites (bAAm) (2-methylbutyrate, isovalerate, phenylacetate). Integration using DIABLO revealed a deep interconnection between all the datasets. Importantly, we identified bacteria which disappearance was associated with impaired gut barrier function (Odoribacter splanchnicus) and body weight loss (Gemmiger formicilis), suggesting these bacteria as actionable targets.

CONCLUSION

AML intensive therapy transiently impairs the gut barrier function while inducing enduring alterations in the composition and metabolic activity of the gut microbiota that associate with body weight loss.

TRIAL REGISTRATION

NCT03881826, https://clinicaltrials.gov/ct2/show/NCT03881826.

Mapping the key characteristics of carcinogens for glyphosate and its formulations: A systematic review

Glyphosate was classified as a probable human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC) partially due to strong mechanistic evidence in 2015. Since then, numerous studies of glyphosate and its formulations (GBF) have emerged. These studies can be evaluated for cancer hazard identification with the newly described ten key characteristics (KC) of carcinogens approach. Our objective was to assess all in vivo, ex vivo, and in vitro mechanistic studies of human and experimental animals (mammals) that compared exposure to glyphosate/GBF with low/no exposure counterparts for evidence of the ten KCs. A protocol with our methods adhering to PRISMA guidelines was registered a priori (INPLASY202180045). Two blinded reviewers screened all in vivo, ex vivo, and in vitro studies of glyphosate/GBF exposure in humans/mammals reporting any KC-related outcome available in PubMed before August 2021. Studies that met inclusion criteria underwent data extraction conducted in duplicate for each KC outcome reported along with key aspects of internal/external validity, results, and reference information. These data were used to construct a matrix that was subsequently analyzed in the program R to conduct strength of evidence and quality assessments. Of the 2537 articles screened, 175 articles met inclusion criteria, from which we extracted >50,000 data points related to KC outcomes. Data analysis revealed strong evidence for KC2, KC4, KC5, KC6, KC8, limited evidence for KC1 and KC3, and inadequate evidence for KC7, KC9, and KC10. Notably, our in-depth quality analyses of genotoxicity (KC2) and endocrine disruption (KC8) revealed strong and consistent positive findings. For KC2, we found: 1) studies conducted in humans and human cells provided stronger positive evidence than counterpart animal models; 2) GBF elicited a stronger effect in both human and animal systems when compared to glyphosate alone; and 3) the highest quality studies in humans and human cells consistently revealed strong evidence of genotoxicity. Our analysis of KC8 indicated that glyphosate's ability to modulate hormone levels and estrogen receptor activity is sensitive to both exposure concentration and formulation. The modulations observed provide clear evidence that glyphosate interacts with receptors, alters receptor activation, and modulates the levels and effects of endogenous ligands (including hormones). Our findings strengthen the mechanistic evidence that glyphosate is a probable human carcinogen and provide biological plausibility for previously reported cancer associations in humans, such as non-Hodgkin lymphoma. We identified potential molecular interactions and subsequent key events that were used to generate a probable pathway to lymphomagenesis.

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.

Role of the gut microbiota in hematologic cancer

Hematologic neoplasms represent 6.5% of all cancers worldwide. They are characterized by the uncontrolled growth of hematopoietic and lymphoid cells and a decreased immune system efficacy. Pathological conditions in hematologic cancer could disrupt the balance of the gut microbiota, potentially promoting the proliferation of opportunistic pathogens. In this review, we highlight studies that analyzed and described the role of gut microbiota in different types of hematologic diseases. For instance, myeloma is often associated with Pseudomonas aeruginosa and Clostridium leptum, while in leukemias, Streptococcus is the most common genus, and Lachnospiraceae and Ruminococcaceae are less prevalent. Lymphoma exhibits a moderate reduction in microbiota diversity. Moreover, certain factors such as delivery mode, diet, and other environmental factors can alter the diversity of the microbiota, leading to dysbiosis. This dysbiosis may inhibit the immune response and increase susceptibility to cancer. A comprehensive analysis of microbiota-cancer interactions may be useful for disease management and provide valuable information on host-microbiota dynamics, as well as the possible use of microbiota as a distinguishable marker for cancer progression.

Perturbation of the gut microbiome and association with outcomes following autologous stem cell transplantation in patients with multiple myeloma

The gut microbiome is an important feature of host immunity with associations to hematologic malignancies and cellular therapy. We evaluated the gut microbiome and dietary intake in patients with multiple myeloma undergoing autologous stem cell transplantation. Thirty patients were enrolled, and samples were collected at four timepoints: pre-transplant, engraftment, day +100 (D + 100), and 9-12 months post-transplant. Microbiome analysis demonstrated a loss of alpha diversity at the engraftment timepoint driven by decreases in Blautia, Ruminococcus, and Faecalibacterium genera and related to intravenous antibiotic exposure. Higher fiber intake was associated with increased relative abundance of Blautia at the pre-transplant timepoint. Lower alpha diversity at engraftment was associated with a partial response to therapy compared with complete response (CR) or very good partial response (VGPR) (CR/VGPR vs. PR, p < 0.05). We conclude that loss of bacterial diversity at engraftment may be associated with impaired response to stem cell transplantation in multiple myeloma.

Diagnostic and Therapeutic Uses of the Microbiome in the Field of Oncology

Cancer is a leading cause of death worldwide and it can affect almost every part of the human body. Effective screening and early diagnosis of cancers is extremely difficult due to the multifactorial etiology of the disease and delayed presentation of the patients. The available treatments are usually not specific to the affected organ system, leading to intolerable systemic side effects and early withdrawal from therapies. In vivo and in vitro studies have revealed an association of specific microbiome signatures with individual cancers. The cancer-related human microbiome has also been shown to affect the response of tissues to chemotherapy, immunotherapy, and radiation. This is an excellent opportunity for us to design specific screening markers using the microbiome to prevent cancers and diagnose them early. We can also develop precise treatments that can target cancer-affected specific organ systems and probably use a lesser dose of chemotherapy or radiation for the same effect. This prevents adverse effects and early cessation of treatments. However, we need further studies to exactly clarify and characterize these associations. In this review article, we focus on the association of the microbiome with individual cancers and highlight its future role in cancer screenings, diagnosis, prognosis, and treatments.

Gut Microbiome and Plasma Metabolomic Analysis in Patients with Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematopoietic stem cell disorders. Studies have shown the involvement of an abnormal immune system in MDS pathogenesis. The gut microbiota are known to influence host immunity and metabolism, thereby contributing to the development of hematopoietic diseases. In this study, we performed gut microbiome and plasma metabolomic analyses in patients with MDS and healthy controls. We found that patients with MDS had a different gut microbial composition compared to controls. The gut microbiota in MDS patients showed a continuous evolutionary relationship from the phylum to the species level. At the species level, the abundance of Haemophilus parainfluenzae, Streptococcus luteciae, Clostridium citroniae, and Gemmiger formicilis increased, while that of Prevotella copri decreased in MDS patients compared to controls. Moreover, abundance of bacterial genera correlated with the percentage of lymphocyte subsets in patients with MDS. Metabolomic analysis showed that the concentrations of hypoxanthine and pyroglutamic acid were increased, while that of 3a,7a-dihydroxy-5b-cholestan was decreased in MDS patients compared to controls. In conclusion, gut microbiome and plasma metabolomics are altered in patients with MDS, which may be involved in the immunopathogenesis of the disease.

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

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

The importance of microbiota in hematology

Whilst particular infectious bacteria are well-established to be associated with hematological diseases, more recent interest has focused on the entire microbial community of mucosal surfaces. In particular, the link between hematology and the microbiota (defined as the total assemblage of microorganisms in a mucosal environment)/ microbiome (i.e. the entire ecological habitat, including organisms, their genomes and environmental conditions) is becoming more well-known. Dysbiosis, or a change in the microbiome, has been linked to the development of neoplasms, infections, inflammatory illnesses, and immune-mediated disorders, according to growing data. Microbiota may influence distant tumor microenvironment through a variety of methods, including cytokine release control, dendritic cell activation, and T-cell lymphocyte stimulation. There are numerous major implications to study the microbiome in patients with benign and malignant hematologic disorders. In this review, we investigated the structure and function of the microbiome in patients with benign and malignant hematological diseases. Chemotherapy and immunosuppressive agents used in treatment of these benign and malignant hematological diseases may cause or exacerbate dysbiosis and infectious problems. After understanding the importance of microbiota in hematological diseases, we think that use of probiotics and dietary prebiotic substances targeting microbiota modification aiming to improve hematological disease outcomes should be investigated in future studies.

Characterization of gut microbiota, metabolism and cytokines in benzene-induced hematopoietic damage

Benzene exposure leads to hematopoietic dysfunction and is characterized clinically by a decrease in blood cells, but the underlying mechanisms remain elusive. Disturbed gut microbiota may induce host metabolic, immune disorders and the onset of disease. However, the characterization of gut microbiota, metabolism, cytokines and their association with benzene-induced hematopoietic toxicity lacks systematic evidence. Here, the microbiomics, metabolomics and cytokine network were applied to find out the critical characteristics of gut microbiota, metabolism and cytokines in mice involved in the benzene-induced hematopoietic toxicity. We found that the decline in hematopoietic stem cells was earlier than the hematological changes in the 5 mg/kg and 25 mg/kg benzene exposure groups. While 125 mg/kg benzene exposure resulted in a significant decline in whole blood cells. High-throughput sequencing results showed that benzene exposure disrupted homeostasis of gut microbiota, metabolism and cytokine in mice. 6 bacteria, 12 plasma metabolites and 6 cytokines were associated with benzene-induced hematopoietic damage. Notably, IL-5 was significantly increased in benzene exposure group in a dose-dependent manner, and a significant negative correlation was found between IL-5 and hematopoietic damage. We further found that increased Family_XIII_AD3011_group at the genus level and decreased Anaerotruncus_sp at the species level in benzene-exposed group were strongly associated with hematopoietic toxicity and IL-5. Furthermore, the abundance of Family_XIII_AD3011_group and Anaerotruncus_sp were negatively correlated with Adipic acid and 4-Hydroxyproline, respectively. Our findings indicated that altered flora structure of gut microbiota affects the metabolic phenotype which acts as messengers for the gut microbes, affecting host inflammation. This preliminary study provides new insight into the potential mechanisms of benzene-induced hematopoietic toxicity, further exploration by functional studies is required in the future.

The Role of the Gut Microbiome in Pathogenesis, Biology, and Treatment of Plasma Cell Dyscrasias

In response to emerging discoveries, questions are mounting as to what factors are responsible for the progression of plasma cell dyscrasias and what determines responsiveness to treatment in individual patients. Recent findings have shown close interaction between the gut microbiota and multiple myeloma cells. For instance, that malignant cells shape the composition of the gut microbiota. We discuss the role of the gut microbiota in (i) the development and progression of plasma cell dyscrasias, and (ii) the response to treatment of multiple myeloma and highlight faecal microbiota transplantation as a procedure that could modify the risk of progression or sensitize refractory malignancy to immunotherapy.

The Role of Gut Microbiota in Tumor Immunotherapy

Tumor immunotherapy is the fourth therapy after surgery, chemotherapy, and radiotherapy. It has made great breakthroughs in the treatment of some epithelial tumors and hematological tumors. However, its adverse reactions are common or even more serious, and the response rate in some solid tumors is not satisfactory. With the maturity of genomics and metabolomics technologies, the effect of intestinal microbiota in tumor development and treatment has gradually been recognized. The microbiota may affect tumor immunity by regulating the host immune system and tumor microenvironment. Some bacteria help fight tumors by activating immunity, while some bacteria mediate immunosuppression to help cancer cells escape from the immune system. More and more studies have revealed that the effects and complications of tumor immunotherapy are related to the composition of the gut microbiota. The composition of the intestinal microbiota that is sensitive to treatment or prone to adverse reactions has certain characteristics. These characteristics may be used as biomarkers to predict the prognosis of immunotherapy and may also be developed as “immune potentiators” to assist immunotherapy. Some clinical and preclinical studies have proved that microbial intervention, including microbial transplantation, can improve the sensitivity of immunotherapy or reduce adverse reactions to a certain extent. With the development of gene editing technology and nanotechnology, the design and development of engineered bacteria that contribute to immunotherapy has become a new research hotspot. Based on the relationship between the intestinal microbiota and immunotherapy, the correct mining of microbial information and the development of reasonable and feasible microbial intervention methods are expected to optimize tumor immunotherapy to a large extent and bring new breakthroughs in tumor treatment.