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

Causal associations between the gut microbiota and multiple myeloma: a two-sample Mendelian randomization study

Background

Previous observational studies have indicated a potential association between the gut microbiota and multiple myeloma (MM). However, the relationship between the gut microbiota and MM remains unclear. This study aimed to ascertain the existence of a causal link between the gut microbiota and MM.

Methods

To investigate the potential causal relationship between gut microbiota and MM, a two-sample Mendelian randomization (MR) analysis was conducted. Exposure data was obtained from the MiBioGen consortium, which provided genetic variants associated with 211 bacterial traits. MM outcome data was obtained from the FinnGen consortium. The selection of Single nucleotide polymorphisms estimates was performed through meta-analysis using inverse-variance weighting, and sensitivity analyses were conducted using weighted median, MR Egger, Simple mode, and MR-PRESSO.

Results

The results of the study demonstrated a significant positive correlation between the genus Eubacterium ruminantium group and the risk of MM (OR 1.71, 95% CI 1.21 to 2.39). Conversely, the genus: Dorea (OR 0.46, 95% CI 0.24 to 0.86), Coprococcus1 (OR 0.47, 95% CI 0.22 to 1.00), RuminococcaceaeUCG014 (OR 0.57, 95% CI 0.33 to 0.99), Eubacterium rectale group (OR 0.37, 95% CI 0.18 to 0.77), and order: Victivallales (OR 0.62, 95% CI 0.41-0.94), class: Lentisphaeria (OR 0.62, 95% CI 0.41 to 0.94), exhibited a negative association with MM. The inverse variance weighting analysis provided additional support for these findings.

Conclusion

This study represents an inaugural exploration of MR to investigate the connections between gut microbiota and MM, thereby suggesting potential significance for the prevention and treatment of MM.

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.

Historical Perspective of High-Dose Therapy Followed by Autologous Stem Cell Transplantation in Multiple Myeloma

BACKGROUND

High-dose therapy (HDT) followed by autologous stem cell transplantation (ASCT) has become part of standard of care (SOC) in newly diagnosed multiple myeloma. In this review, we provide a historical perspective on ASCT since its introduction in the 1990s.

SUMMARY

Overall survival (OS) benefit for HDT followed by ASCT was demonstrated in studies comparing HDT with ASCT to standard-dose therapy (SDT) before the era of novel agents. Conditioning is done with melphalan 200 mg/m2. Lower doses (MEL140, MEL150) for older patients with comorbidities are safe and have comparable results. The addition of busulfan to melphalan improves progression-free survival (PFS) but not OS. HDT with ASCT after induction with novel agents prolongs PFS but not OS compared to SDT alone. The benefit is more evident in patients with high-risk cytogenetics. Mobilization can be achieved with granulocyte colony-stimulating factor alone, but is improved with the addition of chemotherapy. Plerixafor reduces mobilization failure and enables sufficient stem cell collection after induction with novel agents. ASCT is safe with a low rate of mortality (1%), and selected patients can be managed as outpatients.

KEY MESSAGES

HDT followed by ASCT remains part of SOC due to its PFS benefit and relatively low toxicity.

Is There Still a Role for Stem Cell Transplantation in Multiple Myeloma?

No therapy in multiple myeloma has been as extensively investigated as stem cell transplantation following high-dose chemotherapy. A search of the national library of medicine in February 2023 revealed over 27,000 publications covering stem cell transplantation. No other treatment for multiple myeloma has been so vigorously investigated. However, given the rapid advances seen in the treatment of multiple myeloma, it is legitimate to ask whether the technique first introduced in 1983 by Thomas McIlwain still has relevance. In 1984,Barlogie introduced infusional vincristine, doxorubicin, and dexamethasone and in 1986 published a first series on high-dose therapy with autologous marrow-derived stem cells. At this point, the only available therapies were melphalan, prednisone, other intensive steroids such as methylprednisolone, and interferon. Cyclophosphamide was used both orally and parenterally. VBMCP was introduced as a combination therapy at Memorial Hospital subsequently shown not to be superior to melphalan and prednisone.

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.

Dietary and microbiome evidence in multiple myeloma and other plasma cell disorders

Multiple Myeloma (MM) remains an incurable plasma cell neoplasm. Although little is known about the etiology of MM, several metabolic risk factors such as obesity, diabetes mellitus, diet, and the human intestinal microbiome have been linked to the pathogenesis of MM. In this article, we provide a detailed review of dietary and microbiome factors involved in the pathogenesis of MM and their impact on outcomes. Concurrent with treatment advancements that have improved survival in MM, focused efforts are needed to reduce the burden of MM as well as improve MM specific and overall outcomes once MM is diagnosed. The findings presented in this review will provide a comprehensive guide on the evidence available to date of the impact of dietary and other lifestyle interventions on the gut microbiome and on MM incidence, outcomes, and quality of life. Data generated from such studies can help formulate evidence-based guidelines for healthcare providers to counsel individuals at risk such as those with Monoclonal Gammopathy of Undetermined Significance (MGUS) and Smoldering Multiple Myeloma (SMM) as well as MM survivors with respect to their dietary habits.

The Interaction between Gut Microbiota and Host Amino Acids Metabolism in Multiple Myeloma

Although novel therapies have dramatically improved outcomes for multiple myeloma (MM) patients, relapse is inevitable and overall outcomes are heterogeneous. The gut microbiota is becoming increasingly recognized for its influence on host metabolism. To date, evidence has suggested that the gut microbiota contributes to MM, not only via the progressive activities of specific bacteria but also through the influence of the microbiota on host metabolism. Importantly, the abnormal amino acid metabolism, as well as the altered microbiome in MM, is becoming increasingly apparent, as is the influence on MM progression and the therapeutic response. Moreover, the gut-microbiota-host-amino-acid metabolism interaction in the progression of MM has been highlighted. Modulation of the gut microbiota (such as fecal microbiota transplantation, FMT) can be modified, representing a new angle in MM treatment that can improve outcomes. In this review, the relationship between gut microbiota, metabolism, and MM, together with strategies to modulate the microbiota, will be discussed, and some unanswered questions for ongoing and future research will be presented.

Gut microbiome in multiple myeloma: Mechanisms of progression and clinical applications

The gut commensal microbes modulate human immunity and metabolism through the production of a large number of metabolites, which act as signaling molecules and substrates of metabolic reactions in a diverse range of biological processes. There is a growing appreciation for the importance of immunometabolic mechanisms of the host-gut microbiota interactions in various malignant tumors. Emerging studies have suggested intestinal microbiota contributes to the progression of multiple myeloma. In this review, we summarized the current understanding of the gut microbiome in MM progression and treatment, and the influence of alterations in gut microbiota on treatment response and treatment-related toxicity and complications in MM patients undergoing hematopoietic stem cell transplantation (HSCT). Furthermore, we discussed the impact of gut microbiota-immune system interactions in tumor immunotherapy, focusing on tumor vaccine immunotherapy, which may be an effective approach to improve anti-myeloma efficacy.