Metformin confers sensitisation to syrosingopine in multiple myeloma cells by metabolic blockage and inhibition of protein synthesis.

Multiple myeloma (MM) remains an incurable haematological malignancy despite substantial advances in therapy. Hypoxic bone marrow induces metabolic rewiring in MM cells contributing to survival and drug resistance. Therefore, targeting metabolic pathways may offer an alternative treatment option. In this study, we repurpose two FDA-approved drugs, syrosingopine and metformin. Syrosingopine was used as a dual inhibitor of monocarboxylate transporter 1 and 4 (MCT1/4) and metformin as an inhibitor for oxidative phosphorylation (OXPHOS). Anti-tumour effects were evaluated for single agents and in combination therapy. Survival and expression data for MCT1/MCT4 were obtained from the Total Therapy 2, Mulligan, and Multiple Myeloma Research Foundation cohorts. Cell death, viability, and proliferation were measured using Annexin V/7-AAD, CellTiterGlo, and BrdU, respectively. Metabolic effects were assessed using Seahorse Glycolytic Rate assays and LactateGlo assays. Differential protein expression was determined using western blotting, and the SUnSET method was implemented to quantify protein synthesis. Finally, the syngeneic 5T33MMvv model was used for in vivo analysis. High-level expression of MCT1 and MCT4 both correlated with a significantly lower overall survival of patients. Lactate production as well as MCT1/MCT4 expression were significantly upregulated in hypoxia, confirming the Warburg effect in MM. Dual inhibition of MCT1/4 with syrosingopine resulted in intracellular lactate accumulation and reduced cell viability and proliferation. However, only at higher doses (>10 µm) was syrosingopine able to induce cell death. By contrast, combination treatment of syrosingopine with metformin was highly cytotoxic for MM cell lines and primary patient samples and resulted in a suppression of both glycolysis and OXPHOS. Moreover, pathway analysis revealed an upregulation of the energy sensor p-AMPKα and more downstream a reduction in protein synthesis. Finally, the combination treatment resulted in a significant reduction in tumour burden in vivo. This study proposes an alternative combination treatment for MM and provides insight into intracellular effects. © 2023 The Pathological Society of Great Britain and Ireland.

Thrombotic Thrombocytopenic Purpura: When Basic Science Meets Clinical Research.

The therapeutic landscape of thrombotic thrombocytopenic purpura (TTP) is rapidly changing with the recent availability of new targeted therapies. This progressive shift from empiricism to pathophysiology-based treatments reflects an intensive interaction between the continuous findings in the field of basic science and an efficient collaborative clinical research and represents a convincing example of the strength of translational medicine. Despite the rarity of TTP, national and international efforts could circumvent this limitation and shed light on the epidemiology, clinical presentation, prognosis, and long-term outcome of this disease. Importantly, they also provided high-quality results and practice changing studies for the benefit of patients. We report here the most recent therapeutic findings that allowed progressively improving the prognostic of TTP, both at the acute phase and through long-term outcome.

The Transfer of Sphingomyelinase Contributes to Drug Resistance in Multiple Myeloma.

Multiple myeloma (MM) is well-known for the development of drug resistance, leading to relapse. Therefore, finding novel treatment strategies remains necessary. By performing a lipidomics assay on MM patient plasma, we aimed to identify new targets. We observed a dysregulation in the sphingolipid metabolism, with the upregulation of several ceramides and downregulation of sphingomyelin. This imbalance suggests an increase in sphingomyelinase, the enzyme responsible for hydrolyzing sphingomyelin into ceramide. We confirmed the upregulation of acid sphingomyelinase (ASM) in primary MM cells. Furthermore, we observed an increase in ASM expression in MM cell lines treated with melphalan or bortezomib, as well as in their exosomes. Exosomes high in ASM content were able to transfer the drug-resistant phenotype to chemosensitive cells, hereby suggesting a tumor-protective role for ASM. Finally, inhibition of ASM by amitriptyline improved drug sensitivity in MM cell lines and primary MM cells. In summary, this study is the first to analyze differences in plasma lipid composition of MM patients and match the observed differences to an upregulation of ASM. Moreover, we demonstrate that amitriptyline is able to inhibit ASM and increase sensitivity to anti-myeloma drugs. This study, therefore, provides a rational to include ASM-targeting-drugs in combination strategies in myeloma patients.

AXL Receptor Tyrosine Kinase as a Therapeutic Target in Hematological Malignancies: Focus on Multiple Myeloma.

AXL belongs to the TAM (TYRO3, AXL, and MERTK) receptor family, a unique subfamily of the receptor tyrosine kinases. Their common ligand is growth arrest-specific protein 6 (GAS6). The GAS6/TAM signaling pathway regulates many important cell processes and plays an essential role in immunity, hemostasis, and erythropoiesis. In cancer, AXL overexpression and activation has been associated with cell proliferation, chemotherapy resistance, tumor angiogenesis, invasion, and metastasis; and has been correlated with a poor prognosis. In hematological malignancies, the expression and function of AXL is highly diverse, not only between the different tumor types but also in the surrounding tumor microenvironment. Most research and clinical evidence has been provided for AXL inhibitors in acute myeloid leukemia. However, recent studies also revealed an important role of AXL in lymphoid leukemia, lymphoma, and multiple myeloma. In this review, we summarize the basic functions of AXL in various cell types and the role of AXL in different hematological cancers, with a focus on AXL in the dormancy of multiple myeloma. In addition, we provide an update on the most promising AXL inhibitors currently in preclinical/clinical evaluation and discuss future perspectives in this emerging field.

The anaphase-promoting complex/cyclosome: a new promising target in diffuse large B-cell lymphoma and mantle cell lymphoma.

BACKGROUND: The aggressive B-cell non-Hodgkin lymphomas diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) are characterised by a high proliferation rate. The anaphase-promoting complex/cyclosome (APC/C) and its co-activators Cdc20 and Cdh1 represent an important checkpoint in mitosis. Here, the role of the APC/C and its co-activators is examined in DLBCL and MCL. METHODS: The expression and prognostic value of Cdc20 and Cdh1 was investigated using GEP data and immunohistochemistry. Moreover, the therapeutic potential of APC/C targeting was evaluated using the small-molecule inhibitor proTAME and the underlying mechanisms of action were investigated by western blot. RESULTS: We demonstrated that Cdc20 is highly expressed in DLBCL and aggressive MCL, correlating with a poor prognosis in DLBCL. ProTAME induced a prolonged metaphase, resulting in accumulation of the APC/C-Cdc20 substrate cyclin B1, inactivation/degradation of Bcl-2 and Bcl-xL and caspase-dependent apoptosis. In addition, proTAME strongly enhanced the anti-lymphoma effect of the clinically relevant agents doxorubicin and venetoclax. CONCLUSION: We identified for the first time APC/C as a new, promising target in DLBCL and MCL. Moreover, we provide evidence that Cdc20 might be a novel, independent prognostic factor in DLBCL and MCL.

Exosomes play a role in multiple myeloma bone disease and tumor development by targeting osteoclasts and osteoblasts.

Progression of multiple myeloma (MM) is largely dependent on the bone marrow (BM) microenvironment wherein communication through different factors including extracellular vesicles takes place. This cross-talk not only leads to drug resistance but also to the development of osteolysis. Targeting vesicle secretion could therefore simultaneously ameliorate drug response and bone disease. In this paper, we examined the effects of MM exosomes on different aspects of osteolysis using the 5TGM1 murine model. We found that 5TGM1 sEVs, or 'exosomes', not only enhanced osteoclast activity, they also blocked osteoblast differentiation and functionality in vitro. Mechanistically, we could demonstrate that transfer of DKK-1 led to a reduction in Runx2, Osterix, and Collagen 1A1 in osteoblasts. In vivo, we uncovered that 5TGM1 exosomes could induce osteolysis in a similar pattern as the MM cells themselves. Blocking exosome secretion using the sphingomyelinase inhibitor GW4869 not only increased cortical bone volume, but also it sensitized the myeloma cells to bortezomib, leading to a strong anti-tumor response when GW4869 and bortezomib were combined. Altogether, our results indicate an important role for exosomes in the BM microenvironment and suggest a novel therapeutic target for anti-myeloma therapy.

Multiple myeloma exosomes establish a favourable bone marrow microenvironment with enhanced angiogenesis and immunosuppression.

Multiple myeloma (MM) pathogenesis and progression largely rely on the cells and extracellular factors in the bone marrow (BM) microenvironment. Compelling studies have identified tumour exosomes as key regulators in the maintenance and education of the BM microenvironment by targeting stromal cells, immune cells, and vascular cells. However, the role of MM exosomes in the modification of the BM microenvironment and MM progression remains unclear. Here, we explored the functions of MM exosomes in angiogenesis and immunosuppression in vitro and in vivo. Murine MM exosomes carrying multiple angiogenesis-related proteins enhanced angiogenesis and directly promoted endothelial cell growth. Several pathways such as signal transducer and activator of transcription 3 (STAT3), c-Jun N-terminal kinase, and p53 were modulated by the exosomes in endothelial and BM stromal cells. These exosomes promoted the growth of myeloid-derived suppressor cells (MDSCs) in naive mice through activation of the STAT3 pathway and changed their subsets to similar phenotypes to those seen in MM-bearing mice. Moreover, MM exosomes up-regulated inducible nitric oxide synthase and enhanced the immunosuppressive capacity of BM MDSCs in vivo. Our data show that MM exosomes modulate the BM microenvironment through enhancement of angiogenesis and immunosuppression, which will further facilitate MM progression. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Extracellular vesicle cross-talk in the bone marrow microenvironment: implications in multiple myeloma.

The bone marrow (BM) represents a complex microenvironment containing stromal cells, immune cells, osteoclasts, osteoblasts, and hematopoietic cells, which are crucial for the immune response, bone formation, and hematopoiesis. Apart from soluble factors and direct cell-cell contact, extracellular vesicles (EVs), including exosomes, were recently identified as a third mediator for cell communication. Solid evidence has already demonstrated the involvement of various BM-derived cells and soluble factors in the regulation of multiple biological processes whereas the EV-mediated message delivery system from the BM has just been explored in recent decades. These EVs not only perform physiological functions but can also play a role in cancer development, including in Multiple Myeloma (MM) which is a plasma cell malignancy predominantly localized in the BM. This review will therefore focus on the multiple functions of EVs derived from BM cells, the manipulation of the BM by cancer-derived EVs, and the role of BM EVs in MM progression.