Molecular basis of clonal evolution in multiple myeloma

Activated Tim-3/Galectin-9 participated in the development of multiple myeloma by negatively regulating CD4 T cells

The interaction between Tim-3 on T cells and its ligand Galectin-9 negatively regulates the cellular immune response. However, the regulation of Tim-3/Galectin-9 on CD4 T cell subsets in multiple myeloma (MM) remains unclear. The aim of this study was to investigate the relationship between the regulation of CD4 T cell subsets by the Tim-3/Galectin-9 pathway and clinical prognostic indicators in MM. Tim-3/Galectin-9 were detected by flow cytometry, PCR and ELISA in 60 MM patients and 40 healthy controls, and its correlation with clinical prognostic parameters was analyzed. The expressions of Tim-3 on CD4 T cells, Galectin-9 mRNA in PBMC and level of Galectin-9 protein in serum were significantly elevated in MM patients, especially those with poor prognostic indicators. In MM patients, Tim-3 was highly expressed on the surfaces of Th1, Th2, and Th17 cells, but lowly expressed on Treg. Moreover, level of cytokine IFN-γ in serum was negatively correlated with Tim-3+Th1 cell and Galectin-9mRNA, Galectin-9 protein level. In addition, cell culture experiments showed that the anti-tumor effect and the ability to secrete IFN-γ were restored by blocking the Tim-3/Galectin-9 pathway. In MM patients, Tim-3/Galectin-9 is elevated and associated with disease progression, by inhibiting the cytotoxic function of Th1, and also promoting Th2 and Th17 to be involved in immune escape of MM. Therefore, Tim-3/Galectin-9 may serve as a new immunotherapeutic target for MM patients.

Chromosomal defects in multiple myeloma

Multiple myeloma is a plasma cell neoplasm driven by primary (e.g. hyperdiploidy; IGH translocations) and secondary (e.g. 1q21 gains/amplifications; del(17p); MYC translocations) chromosomal events. These are important to detect as they influence prognosis, therapeutic response and disease survival. Currently, cytogenetic testing is most commonly performed by interphase fluorescence in situ hybridisation (FISH) on aspirated bone marrow samples. A number of variations to FISH methodology are available, including prior plasma cell enrichment and incorporation of immunophenotypic plasma cell identification. Other molecular methods are increasingly being utilised to provide a genome-wide view at high resolution (e.g. single nucleotide polymorphism (SNP) microarray analysis) and these can detect abnormalities in most cases. Despite their wide application at diagnostic assessment, both FISH and SNP-array have relatively low sensitivity, limiting their use for identification of prognostically significant low-level sub-clones or for disease monitoring. Next-generation sequencing is increasingly being used to detect mutations and new FISH techniques such as by flow cytometry are in development and may address some of the current test limitations. Here we review the primary and secondary cytogenetic aberrations in myeloma and discuss the range of techniques available for their assessment.

Lymphomas and Amyloid in the Gastrointestinal Tract

Lymphoproliferative disorders are a heterogeneous group of neoplasms with varying clinical, morphologic, immunophenotypic, and genetic characteristics. A subset of lymphomas have a proclivity for the gastrointestinal tract, although this region may also be involved by systemic lymphomas. In addition, a number of indolent lymphoproliferative disorders of the gastrointestinal tract have been defined over the past decade, and it is important to accurately differentiate these neoplasms to ensure that patients receive the proper management. Here, the authors review lymphoid neoplasms that show frequent gastrointestinal involvement and provide updates from the recent hematolymphoid neoplasm classification systems.

Intratumor heterogeneity: models of malignancy emergence and evolution

Cancer is a complex and heterogeneous disease characterized by the accumulation of genetic alterations that drive uncontrolled cell growth and proliferation. Evolutionary dynamics plays a crucial role in the emergence and development of tumors, shaping the heterogeneity and adaptability of cancer cells. From the perspective of evolutionary theory, tumors are complex ecosystems that evolve through a process of microevolution influenced by genetic mutations, epigenetic changes, tumor microenvironment factors, and therapy-induced changes. This dynamic nature of tumors poses significant challenges for effective cancer treatment, and understanding it is essential for developing effective and personalized therapies. By uncovering the mechanisms that determine tumor heterogeneity, researchers can identify key genetic and epigenetic changes that contribute to tumor progression and resistance to treatment. This knowledge enables the development of innovative strategies for targeting specific tumor clones, minimizing the risk of recurrence and improving patient outcomes. To investigate the evolutionary dynamics of cancer, researchers employ a wide range of experimental and computational approaches. Traditional experimental methods involve genomic profiling techniques such as next-generation sequencing and fluorescence in situ hybridization. These techniques enable the identification of somatic mutations, copy number alterations, and structural rearrangements within cancer genomes. Furthermore, single-cell sequencing methods have emerged as powerful tools for dissecting intratumoral heterogeneity and tracing clonal evolution. In parallel, computational models and algorithms have been developed to simulate and analyze cancer evolution. These models integrate data from multiple sources to predict tumor growth patterns, identify driver mutations, and infer evolutionary trajectories. In this paper, we set out to describe the current approaches to address this evolutionary complexity and theories of its occurrence.

Anti‑BCMA CAR‑T cell immunotherapy for relapsed or refractory multiple myeloma

The present study aimed to study the efficacy and adverse effects of anti-B-cell maturation antigen (BCMA) chimeric antigen receptor T (CAR-T) cell therapy in relapsed or refractory multiple myeloma. Patients were divided into three dose groups based on cell therapy concentration. After CAR-T cell therapy for 10 patients with recurrent or refractory multiple myeloma, the patients were monitored and evaluated regularly to observe the efficacy and adverse reactions of CAR-T cell therapy. At a median follow-up of 337 (253-504) days, one patient succumbed 24 days due to rapidly progressing disease. The overall response rate of nine patients was 88.9%, including 77.8% (7/9) with minimal residual disease negative complete remission (CR) and 11.1% (1/9) with partial remission. A total of three patients were maintained in remission state for more than a year and eight were maintained for more than six months. Among the three patients with extramedullary invasion, two extramedullary lesions disappeared and one was stable. The highest copy number of CAR-T cells in seven patients with CR was >1x105 copies/µl gDNA, and the best therapeutic effect can be achieved within 30 (7-30) days after the copy number of CAR-T cells reached 1x105 copies/µl genomic DNA. The median onset time in the nine patients was 43 (22-169) days, and the median progression-free survival was 337 (253-504). Among the 10 patients, nine (90%) had cytokine release syndrome, all of which were below grade II. There were nine (90%) patients with hematological adverse reactions, six (60%) patients with severe anemia, five (50%) patients with grade III and above leukopenia, five (50%) patients with granulocytopenia, four (40%) patients with grade III and above thrombocytopenia, and three (30%) patients with grade III and above pancytopenia. It was concluded that anti-BCMA CAR-T cell therapy is a promising treatment method for relapsed or refractory multiple myeloma and extramedullary invasion, with stable efficacy and controllable adverse effects.

Review on Bortezomib Resistance in Multiple Myeloma and Potential Role of Emerging Technologies

Multiple myeloma is a hematological cancer type. For its treatment, Bortezomib has been widely used. However, drug resistance to this effective chemotherapeutic has been developed for various reasons. 2D cell cultures and animal models have failed to understand the MM disease and Bortezomib resistance. It is therefore essential to utilize new technologies to reveal a complete molecular profile of the disease. In this review, we in-depth examined the possible molecular mechanisms that cause Bortezomib resistance and specifically addressed MM and Bortezomib resistance. Moreover, we also included the use of nanoparticles, 3D culture methods, microfluidics, and organ-on-chip devices in multiple myeloma. We also discussed whether the emerging technology offers the necessary tools to understand and prevent Bortezomib resistance in multiple myeloma. Despite the ongoing research activities on MM, the related studies cannot provide a complete summary of MM. Nanoparticle and 3D culturing have been frequently used to understand MM disease and Bortezomib resistance. However, the number of microfluidic devices for this application is insufficient. By combining siRNA/miRNA technologies with microfluidic devices, a complete molecular genetic profile of MM disease could be revealed. Microfluidic chips should be used clinically in personal therapy and point-of-care applications. At least with Bortezomib microneedles, it could be ensured that MM patients can go through the treatment process more painlessly. This way, MM can be switched to the curable cancer type list, and Bortezomib can be targeted for its treatment with fewer side effects.

Chimeric antigen receptor T-cell therapy for multiple myeloma

Multiple myeloma (MM) is a malignant plasma cell disorder that remains incurable for most patients, as persistent clonal evolution drives new mutations which confer MM high-risk signatures and resistance to standard care. The past two decades have significantly refashioned the therapeutic options for MM, especially adoptive T cell therapy contributing to impressive response rate and clinical efficacy. Despite great promises achieved from chimeric antigen receptor T-cell (CAR-T) therapy, the poor durability and severe toxicity (cytokine release syndrome and neurotoxicity) are still huge challenges. Therefore, relapsed/refractory multiple myeloma (RRMM), characterized by the nature of clinicopathologic and molecular heterogeneity, is frequently associated with poor prognosis. B Cell Maturation Antigen (BCMA) is the most successful target for CAR-T therapy, and other potential targets either for single-target or dual-target CAR-T are actively being studied in numerous clinical trials. Moreover, mechanisms driving resistance or relapse after CAR-T therapy remain uncharacterized, which might refer to T-cell clearance, antigen escape, and immunosuppressive tumor microenvironment. Engineering CAR T-cell to improve both efficacy and safety continues to be a promising area for investigation. In this review, we aim to describe novel tumor-associated neoantigens for MM, summarize the data from current MM CAR-T clinical trials, introduce the mechanism of disease resistance/relapse after CAR-T infusion, highlight innovations capable of enhanced efficacy and reduced toxicity, and provide potential directions to optimize manufacturing processes.

Preclinical evidence of a direct pro-survival role of arginine deprivation in multiple myeloma

Multiple myeloma grows by establishing multiple interactions with bone marrow cells. These include expansion of myeloid-derived suppressor cells, which drive immunoevasion via mechanisms that include arginase-1-driven depletion of L-arginine, thus indirectly promoting myeloma cell survival and tumor progression. The peculiar biology of malignant plasma cells postulates that arginine depletion may benefit their fitness also directly, e.g., by engaging the integrated stress response, or by stimulating autophagy through mTORC1 inhibition. We thus investigated the direct impact of arginine deprivation on myeloma cells and challenged its pathophysiological relevance in vitro and in vivo. First, we found that partial arginine depletion spared proliferation of human multiple myeloma cells at concentrations that arrest human T cells. Next, we asked if arginine shortage activates putative adaptive pathways in myeloma cells. Low arginine failed to activate the integrated stress response, as indicated by unmodified phosphorylation of the eukaryotic initiation factor 2α, but sizably inhibited mTORC1, as revealed by reduced phosphorylation of ribosomal protein S6. Notably, depressed mTORC1 activity was not sufficient to increase autophagy, as assessed by the lysosomal digestion rate of the autophagosome-associated protein, LC3-II. Rather, it stimulated mTORC2, resulting in increased phosphatidylinositol-3 kinase-dependent AKT phosphorylation and activity, leading to heightened inhibitory phosphorylation of the pro-apoptotic BAD protein. We then tested whether arginine depletion-activated AKT may protect malignant plasma cells from cell death. Indeed, culturing myeloma cells in low arginine medium significantly reduced the apoptotic effect of the first-in-class proteasome inhibitor, bortezomib, an outcome prevented by pharmacological inhibition of AKT phosphorylation. Finally, we challenged the relevance of the identified circuit in vivo. To gauge the pathophysiologic relevance of low arginine to myeloma growth independently of immunoevasion, we xenotransplanted human myeloma cells subcutaneously into T cell-deficient Rag2^–/–γc^–/– recipient mice and treated palpable tumor-bearing mice with the clinical-grade arginase inhibitor CB1158. Arginase inhibition significantly raised serum arginine concentration, reduced tumor growth by caliper assessment, and decreased intra-tumor AKT phosphorylation in vivo. Altogether, our results reveal a novel direct pro-survival effect of arginine deprivation on myeloma cells, with potential therapeutic implications.

Segmentation and counting of multiple myeloma cells using IEMD based deep neural network

In biomedical image analysis, segmentation of cell nuclei from microscopic images is a highly challenging research problem. In the computer-assisted health care system, the segmented microscopic cells have been used by many biological researchers for the early prediction of various diseases. Multiple myeloma is one type of disease which is also term as a plasma cell cancer. The segmentation of the nucleus and cell is a very critical step for multiple myeloma detection. Here, In this work, we have designed two modules. One is for recognizing the nucleus of myeloma cells with a deep IEMD neural network, and the other is for differentiating the cell i.e cytoplasm. The different IMFs provides detailed frequency component of an image which are used for feature extraction. This will significantly improves the performance. We proposed a new counting algorithm for counting the myeloma-affected plasma cells in this paper. An algorithm for counting overgrowth plasma cells within the myeloid tissue has been developed using the Python TensorFlow framework. Experimental outcomes on SegPC datasets substantiate that, the proposed deep learning approach outperforms other competitive methods in myeloma recognition and detection. The result of this research indicates that, the proposed image segmentation mechanism can recognize multiple myeloma with superiority. Early detection of multiple myeloma at the initial stage increases the chances to cure patients.

Kinase Inhibition in Multiple Myeloma: Current Scenario and Clinical Perspectives

Multiple myeloma (MM) is a blood cell neoplasm characterized by excessive production of malignant monoclonal plasma cells (activated B lymphocytes) by the bone marrow, which end up synthesizing antibodies or antibody fragments, called M proteins, in excess. The accumulation of this production, both cells themselves and of the immunoglobulins, causes a series of problems for the patient, of a systemic and local nature, such as blood hyperviscosity, renal failure, anemia, bone lesions, and infections due to compromised immunity. MM is the third most common hematological neoplasm, constituting 1% of all cancer cases, and is a disease that is difficult to treat, still being considered an incurable disease. The treatments currently available cannot cure the patient, but only extend their lifespan, and the main and most effective alternative is autologous hematopoietic stem cell transplantation, but not every patient is eligible, often due to age and pre-existing comorbidities. In this context, the search for new therapies that can bring better results to patients is of utmost importance. Protein tyrosine kinases (PTKs) are involved in several biological processes, such as cell growth regulation and proliferation, thus, mutations that affect their functionality can have a great impact on crucial molecular pathways in the cells, leading to tumorigenesis. In the past couple of decades, the use of small-molecule inhibitors, which include tyrosine kinase inhibitors (TKIs), has been a hallmark in the treatment of hematological malignancies, and MM patients may also benefit from TKI-based treatment strategies. In this review, we seek to understand the applicability of TKIs used in MM clinical trials in the last 10 years.

Gene expression profiling and in vitro functional studies reveal RAD54L as a potential therapeutic target in multiple myeloma

Background

Current advances in the molecular biology of multiple myeloma (MM) are not sufficient to fully delineate the genesis and development of this disease.

Objective

This study aimed to identify molecular targets underlying MM pathogenesis.

Methods

mRNA expression profiling for 29 samples (19 MM samples, 7 MM cell lines and 3 controls) were obtained using microarray. We evaluated the in vitro effects of RAD54L gene silencing on the proliferation, apoptosis and cell cycle distribution in KMS-28BM human MM cells using siRNA approach. Cell proliferation was determined by MTS assay while apoptosis and cell cycle distribution were analysed with flow cytometry. Gene and protein expression was evaluated using RT-qPCR and ELISA, respectively.

Results

Microarray results revealed a total of 5124 differentially expressed genes (DEGs), in which 2696 and 2428 genes were up-regulated and down-regulated in MM compared to the normal controls, respectively (fold change ≥ 2.0; P < 0.05). Up-regulated genes (RAD54L, DIAPH3, SHCBP1, SKA3 and ANLN) and down-regulated genes (HKDC1, RASGRF2, CYSLTR2) have never been reported in association with MM. Up-regulation of RAD54L was further verified by RT-qPCR (P < 0.001). In vitro functional studies revealed that RAD54L gene silencing significantly induced growth inhibition, apoptosis (small changes) and cell cycle arrest in G0/G1 phase in KMS-28BM (P < 0.05). Silencing of RAD54L also decreased its protein level (P < 0.05).

Conclusions

This study has identified possible molecular targets underlying the pathogenesis of MM. For the first time, we reveal RAD54L as a potential therapeutic target in MM, possibly functioning in the cell cycle and checkpoint control.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13258-022-01272-7.

The yin–yang effects of immunity: From monoclonal gammopathy of undetermined significance to multiple myeloma

Multiple myeloma (MM) is the third most common malignant neoplasm of the hematological system. It often develops from monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) precursor states. In this process, the immune microenvironment interacts with the MM cells to exert yin and yang effects, promoting tumor progression on the one hand and inhibiting it on the other. Despite significant therapeutic advances, MM remains incurable, and the main reason for this may be related to the complex and variable immune microenvironment. Therefore, it is crucial to investigate the dynamic relationship between the immune microenvironment and tumors, to elucidate the molecular mechanisms of different factors in the microenvironment, and to develop novel therapeutic agents targeting the immune microenvironment of MM. In this paper, we review the latest research progress and describe the dual influences of the immune microenvironment on the development and progression of MM from the perspective of immune cells and molecules.

Presence of bone marrow fibrosis in multiple myeloma may predict extramedullary disease

We analyzed the incidence of bone marrow fibrosis in 91 newly diagnosed Japanese multiple myeloma (MM) patients and evaluated the impact of fibrosis on clinical characteristics and therapeutic outcomes. Thirty-four (37%) patients had greater than grade 1 bone marrow fibrosis. The presence of bone marrow fibrosis did not affect laboratory data, the percentage of plasma cells in bone marrow or cytogenetic findings. It also had no significant effect on response to initial treatment, engraftment after autologous hematopoietic stem cell transplantation or overall survival. Interestingly, the incidence of extramedullary disease at diagnosis was significantly higher in patients with bone marrow fibrosis (p = 0.006). Analysis of biological characteristics of MM cells revealed that expression of CD49e, an alpha5/beta1 integrin, was downregulated in MM cells derived from patients with bone marrow fibrosis (p = 0.026). When seven of the original 34 patients were re-evaluated for fibrosis grading after treatment, five (71%) showed a reduction in fibrosis. Our present findings suggest that the presence of bone marrow fibrosis may predict development of extramedullary disease in MM.

From Biology to Treatment of Monoclonal Gammopathies of Neurological Significance

Monoclonal gammopathy and peripheral neuropathy are common diseases of elderly patients, and almost 10% of patients with neuropathy of unknown cause have paraprotein. However, growing evidence suggests that several hematological malignancies synthesize and release monoclonal proteins that damage the peripheral nervous system through different mechanisms. The spectrum of the disease varies from mild to rapidly progressive symptoms, sometimes affecting not only sensory nerve fibers, but also motor and autonomic fibers. Therefore, a multidisciplinary approach, mainly between hematologists and neurologists, is recommended in order to establish the correct diagnosis of monoclonal gammopathy of neurological significance and to tailor therapy based on specific genetic mutations. In this review, we summarize the spectrum of monoclonal gammopathies of neurological significance, their distinctive clinical and neurophysiological phenotypes, the most relevant pathophysiological events and new therapeutic approaches.

The Rationale for the Dual-Targeting Therapy for RSK2 and AKT in Multiple Myeloma

Multiple myeloma (MM) is characterized by remarkable cytogenetic/molecular heterogeneity among patients and intraclonal diversity even in a single patient. We previously demonstrated that PDPK1, the master kinase of series of AGC kinases, is universally active in MM, and plays pivotal roles in cell proliferation and cell survival of myeloma cells regardless of the profiles of cytogenetic and genetic abnormalities. This study investigated the therapeutic efficacy and mechanism of action of dual blockade of two major PDPK1 substrates, RSK2 and AKT, in MM. The combinatory treatment of BI-D1870, an inhibitor for N-terminal kinase domain (NTKD) of RSK2, and ipatasertib, an inhibitor for AKT, showed the additive to synergistic anti-tumor effect on human MM-derived cell lines (HMCLs) with active RSK2-NTKD and AKT, by enhancing apoptotic induction with BIM and BID activation. Moreover, the dual blockade of RSK2 and AKT exerted robust molecular effects on critical gene sets associated with myeloma pathophysiologies, such as those with MYC, mTOR, STK33, ribosomal biogenesis, or cell-extrinsic stimuli of soluble factors, in HMCLs. These results provide the biological and molecular rationales for the dual-targeting strategy for RSK2 and AKT, which may overcome the therapeutic difficulty due to cytogenetic/molecular heterogeneity in MM.

The Peptide–Drug Conjugate Melflufen Modulates the Unfolded Protein Response of Multiple Myeloma and Amyloidogenic Plasma Cells and Induces Cell Death

Immunoglobulin light-chain (AL) amyloidosis is a rare disease caused by clonal plasma cell secretion of misfolded light chains that assemble as toxic amyloid fibrils, depositing in vital organs including the heart and kidneys, causing organ dysfunction. Plasma cell–directed therapeutics are expected to reduce production of toxic light chain by eliminating amyloidogenic cells in bone marrow, thereby diminishing amyloid fibril deposition and providing the potential for organ recovery. Melphalan flufenamide (melflufen) is a first-in-class peptide–drug conjugate that targets aminopeptidases and rapidly releases alkylating agents inside tumor cells. Melflufen is highly lipophilic, permitting rapid uptake by cells, where it is enzymatically hydrolyzed by aminopeptidases, resulting in intracellular accumulation of the alkylating agents, including melphalan. Previous data demonstrating sensitivity of myeloma cells to melflufen suggest that the drug might be useful in AL amyloidosis. We describe the effects of melflufen on amyloidogenic plasma cells in vitro and ex vivo, demonstrating enhanced cytotoxic effects in comparison to melphalan, as well as novel mechanisms of action through the unfolded protein response (UPR) pathway. These findings provide evidence that melflufen-mediated cytotoxicity extends to amyloidogenic plasma cells, and support the rationale for the evaluation of melflufen in patients with AL amyloidosis.

Genome Instability in Multiple Myeloma: Facts and Factors

Multiple myeloma (MM) is a malignant neoplasm of terminally differentiated immunoglobulin-producing B lymphocytes called plasma cells. MM is the second most common hematologic malignancy, and it poses a heavy economic and social burden because it remains incurable and confers a profound disability to patients. Despite current progress in MM treatment, the disease invariably recurs, even after the transplantation of autologous hematopoietic stem cells (ASCT). Biological processes leading to a pathological myeloma clone and the mechanisms of further evolution of the disease are far from complete understanding. Genetically, MM is a complex disease that demonstrates a high level of heterogeneity. Myeloma genomes carry numerous genetic changes, including structural genome variations and chromosomal gains and losses, and these changes occur in combinations with point mutations affecting various cellular pathways, including genome maintenance. MM genome instability in its extreme is manifested in mutation kataegis and complex genomic rearrangements: chromothripsis, templated insertions, and chromoplexy. Chemotherapeutic agents used to treat MM add another level of complexity because many of them exacerbate genome instability. Genome abnormalities are driver events and deciphering their mechanisms will help understand the causes of MM and play a pivotal role in developing new therapies.

An Overview of Organoid and 3-Dimensional Models in Multiple Myeloma

ABSTRACT

Multiple myeloma is a hematological malignancy of differentiated B cells that resides primarily in bone marrow niches. Its interaction with the microenvironment is known to provide a survival advantage and plays an important role in drug resistance. Despite the increased efficacy of new treatment drugs, clinical results oftentimes fall short of in vitro observations, and this disease remains incurable. Conventional 2-dimensional cultures used to perform chemosensitivity assays and the established multiple myeloma cells lines commonly used do not replicate the conditions seen in vivo. This review presents various 3-dimensional culture platforms for myeloma that attempt to overcome this obstacle by incorporating aspects of the tumor microenvironment. The unique features of each model and contributions they have provided in personalized medicine, tumor physiology, and chemosensitivity assays will be summarized.

Evolutionary Mechanisms of Cancer Suggest Rational Therapeutic Approaches

The goal in personalized therapeutic approaches for cancer medicine is to identify specific mutations with prognostic and therapeutic value in order to tailor the therapy for the single patient. The most powerful obstacle for personalized medicine arises from intratumor heterogeneity and clonal evolution, which can promote drug resistance. In this scenario, new technologies, such as next-generation sequencing, have emerged as a central diagnostic tool to profile cancer (epi)genomic landscapes. Therefore, a better understanding of the biological mechanisms underlying cancer evolution is mandatory and represents the current challenge to accurately predict whether cancer will recur after chemotherapy with the aim to tailor rational therapeutic approaches.

Clonal Evolution of Multiple Myeloma-Clinical and Diagnostic Implications

Plasma cell dyscrasias are a heterogeneous group of diseases characterized by the expansion of bone marrow plasma cells. Malignant transformation of plasma cells depends on the continuity of events resulting in a sequence of well-defined disease stages, from monoclonal gammopathy of undetermined significance (MGUS) through smoldering myeloma (SMM) to symptomatic multiple myeloma (MM). Evolution of a pre-malignant cell into a malignant cell, as well as further tumor progression, dissemination, and relapse, require development of multiple driver lesions conferring selective advantage of the dominant clone and allowing subsequent evolution under selective pressure of microenvironment and treatment. This process of natural selection facilitates tumor plasticity leading to the formation of genetically complex and heterogenous tumors that are notoriously difficult to treat. Better understanding of the mechanisms underlying tumor evolution in MM and identification of lesions driving the evolution from the premalignant clone is therefore a key to development of effective treatment and long-term disease control. Here, we review recent advances in clonal evolution patterns and genomic landscape dynamics of MM, focusing on their clinical implications.

A Comprehensive Review of the Genomics of Multiple Myeloma: Evolutionary Trajectories, Gene Expression Profiling, and Emerging Therapeutics

Multiple myeloma (MM) is a blood cancer characterized by the accumulation of malignant monoclonal plasma cells in the bone marrow. It develops through a series of premalignant plasma cell dyscrasia stages, most notable of which is the Monoclonal Gammopathy of Undetermined Significance (MGUS). Significant advances have been achieved in uncovering the genomic aberrancies underlying the pathogenesis of MGUS-MM. In this review, we discuss in-depth the genomic evolution of MM and focus on the prognostic implications of the accompanied molecular and cytogenetic aberrations. We also dive into the latest investigatory techniques used for the diagnoses and risk stratification of MM patients.

Multiple myeloma with t(11;14)-associated immature phenotype has lower CD38 expression and higher BCL2 dependence

CD38 expression on myeloma cells is a critical factor affecting the early response to the anti-CD38 antibody daratumumab. However, factors affecting CD38 expression in untreated multiple myeloma are not fully elucidated. In this study, we found that CD38 expression was significantly lower in myeloma patients with the translocation t(11;14)-associated immature plasma cell phenotype, and particularly in those expressing B-cell-associated genes such as PAX5 and CD79A. CD138, a representative marker of plasmacytic differentiation, was also significantly lower in these patients, suggesting that CD38 expression may be associated with the differentiation and maturation stages of myeloma cells. Furthermore, the BCL2/BCL2L1 ratio, a response marker of the BCL2 inhibitor venetoclax, was significantly higher in patients with the immature phenotype expressing B-cell-associated genes. The BCL2/BCL2L1 ratio and CD38 expression were significantly negatively correlated. We also confirmed that patients with translocation t(11;14) expressing B-cell-associated genes were indeed less sensitive to daratumumab-mediated direct cytotoxicity but highly sensitive to venetoclax treatment in ex vivo assays. Moreover, all-trans-retinoic acid, which enhances CD38 expression and induces cell differentiation in myeloma cells, reduced B-cell marker expression and the BCL2/BCL2L1 ratio in myeloma cell lines, leading to reduced efficacy of venetoclax. Venetoclax specifically induces cell death in myeloma with t(11;14), although why patients with translocation t(11;14) show BCL2 dependence is unclear. These results suggest that BCL2 dependence, as well as CD38 expression, are deeply associated with the differentiation and maturation stages of myeloma cells. This study highlights the importance of examining t(11;14) and considering cell maturity in myeloma treatment strategies.

Impact of hypoxia on the pathogenesis and therapy resistance in multiple myeloma

Multiple myeloma (MM) is a refractory plasma cell tumor. In myeloma cells, the transcription factor IRF4, the master regulator of plasma cells, is aberrantly upregulated and plays an essential role in oncogenesis. IRF4 forms a positive feedback loop with MYC, leading to additional tumorigenic properties. In recent years, molecular targeted therapies have contributed to a significant improvement in the prognosis of MM. Nevertheless, almost all patients experience disease progression, which is thought to be a result of treatment resistance induced by various elements of the bone marrow microenvironment. Among these, the hypoxic response, one of the key processes for cellular homeostasis, induces hypoxia‐adapted traits such as undifferentiation, altered metabolism, and dissemination, leading to drug resistance. These inductions are caused by ectopic gene expression changes mediated by the activation of hypoxia‐inducible factors (HIFs). By contrast, the expression levels of IRF4 and MYC are markedly reduced by hypoxic stress. Notably, an anti‐apoptotic capability is usually acquired under both normoxic and hypoxic conditions, but the mechanism is distinct. This fact strongly suggests that myeloma cells may survive by switching their dependent regulatory factors from IRF4 and MYC (normoxic bone marrow region) to HIF (hypoxic bone marrow microenvironment). Therefore, to achieve deep remission, combination therapeutic agents, which are complementarily effective against both IRF4‐MYC‐dominant and HIF‐dominated fractions, may become an important therapeutic strategy for MM.

Smoldering multiple myeloma - Past, present, and future

Smoldering multiple myeloma (SMM) routinely precedes the development of multiple myeloma. While some patients experience aggressive disease, others have more indolent courses akin to those with monoclonal gammopathy of undetermined significance. Much effort has been made to understand the pathobiological basis of this heterogeneity. Scientific advancements have led to the emergence of various clinical and genomic markers of relevance, translating into evolution of disease definitions over time. More recently, the interest in manipulation of biological pathways has intensified in a bid to stall or halt disease progression. Studies with lenalidomide have exemplified the promise of early intervention, whereas numerous therapeutic approaches remain the subject of ongoing clinical investigation. This review summarizes the historic progress made in defining SMM as a distinct clinicopathologic entity, provides a critical appraisal of the evidence guiding risk assessment, and suggests a pragmatic approach to its modern-day management. Finally, an overview of developments on the horizon is also provided.

Identification and monitoring of Copy Number Variants (CNV) in monoclonal gammopathy

Monoclonal gammopathy of undetermined significance (MGUS) represents the pre-clinical stage of Multiple Myeloma (MM) with the 5% of MGUS progresses to MM. Although the progression from MGUS to MM has not been completely characterized, it is possible to monitor the DNA modifications of patients diagnosed with MGUS to detect early specific genomic abnormalities, including copy number variations (CNV). The CNVs of chromosome 1q and chromosome 13q are associated with a worse prognosis in MM.In the present study, we showed that it is possible to monitor the 1q21 gain and 13q deletion frequencies in gDNA using digital PCR. The CNV analysis of three cell lines with a well-characterized cytogenetic profile were compared with measures performed by a real-time PCR approach and with a digital PCR approach. Then, we analyzed CNVs in CD138⁺ plasma cells isolated from bone marrow of MGUS and MM patients.Our results show that digital PCR and targeted DNA monitoring represent a specific and accurate technique for the early detection of specific genomic abnormalities both in MM and in MGUS patients.Our results could represent a remarkable advancement in MM and MGUS diagnosis and in CNV analysis for the evaluation of the risk of progression from MGUS to MM.

Whole-genome optical mapping of bone-marrow myeloma cells reveals association of extramedullary multiple myeloma with chromosome 1 abnormalities

Extramedullary disease (EMM) represents a rare, aggressive and mostly resistant phenotype of multiple myeloma (MM). EMM is frequently associated with high-risk cytogenetics, but their complex genomic architecture is largely unexplored. We used whole-genome optical mapping (Saphyr, Bionano Genomics) to analyse the genomic architecture of CD138+ cells isolated from bone-marrow aspirates from an unselected cohort of newly diagnosed patients with EMM (n = 4) and intramedullary MM (n = 7). Large intrachromosomal rearrangements (> 5 Mbp) within chromosome 1 were detected in all EMM samples. These rearrangements, predominantly deletions with/without inversions, encompassed hundreds of genes and led to changes in the gene copy number on large regions of chromosome 1. Compared with intramedullary MM, EMM was characterised by more deletions (size range of 500 bp–50 kbp) and fewer interchromosomal translocations, and two EMM samples had copy number loss in the 17p13 region. Widespread genomic heterogeneity and novel aberrations in the high-risk IGH/IGK/IGL, 8q24 and 13q14 regions were detected in individual patients but were not specific to EMM/MM. Our pilot study revealed an association of chromosome 1 abnormalities in bone marrow myeloma cells with extramedullary progression. Optical mapping showed the potential for refining the complex genomic architecture in MM and its phenotypes.

Proteasomal adaptations to FDA-approved proteasome inhibitors: a potential mechanism for drug resistance?

With proteasome inhibitors (PIs) becoming clinically available since 2003, outcomes for patients with multiple myeloma (MM) have dramatically changed, improving quality of life and survival. Despite the impressive treatment success, however, almost all MM patients who initially respond to these PIs eventually develop resistance. Furthermore, a portion of MM patients is inherently unresponsive to the PIs. Extensive mechanistic investigations identified several non-proteasomal signaling pathways suspected to be linked to the PI resistance, for which several excellent reviews are currently available. On the other hand, it is still unclear how cancer cells under high PI environments adapt to spare proteasome activity essential for survival and proliferation regardless of cancer evolution stages. This review outlines current progress towards understanding the proteasomal adaptations of cells in response to PI treatment to maintain necessary proteasome activity. A better understanding of cellular proteasomal changes in response to the PIs could provide a rationale to develop new therapeutics that could be used to overcome resistance to existing PI drugs.

Management of patients with difficult-to-treat multiple myeloma

Newer treatments for multiple myeloma (MM) have improved response rates and survival for many patients. However, MM remains challenging to treat due to the propensity for multiple relapses, cumulative and emergent toxicities from prior therapies and increasing genomic complexity that arises due to clonal evolution. In particular, patients with relapsed/refractory MM often require increased complexity of treatment, yet still experience poorer outcomes compared with patients who are newly diagnosed. Additionally, several patient subgroups, including those with extramedullary disease and patients who are frail and/or have multiple comorbidities, have an unfavorable prognosis and remain undertreated. This review (based on an Updates-in-Hematology session at the 25th European Hematology Association Annual Congress 2020) discusses the management of these difficult-to-treat patients with MM.

Treatment Strategies Considering Micro-Environment and Clonal Evolution in Multiple Myeloma

Simple Summary

Multiple myeloma is an uncurable hematological malignancy, although the prognosis of myeloma patients is getting better using proteasome inhibitors (PIs), immune modulatory drugs (IMiDs), monoclonal antibodies (MoAbs), and cytotoxic agents. Drug resistance makes myeloma difficult to treat and it can be subdivided into two broad categories: de novo and acquired. De novo drug resistance is associated with the bone marrow microenvironment including bone marrow stromal cells, the vascular niche and endosteal niche. Acquired drug resistance is related to clonal evolution and non-genetic diversity. The initial treatment plays the most important role considering de novo and acquired drug resistance and should contain PIs, IMIDs, MoAbs, and autologous stem cell transplantation because these treatments improve the bone marrow microenvironment and might prevent clonal evolution via sustained deep response including minimal residual disease negativity.

Abstract

Multiple myeloma is an uncurable hematological malignancy because of obtained drug resistance. Microenvironment and clonal evolution induce myeloma cells to develop de novo and acquired drug resistance, respectively. Cell adhesion-mediated drug resistance, which is induced by the interaction between myeloma and bone marrow stromal cells, and soluble factor-mediated drug resistance, which is induced by cytokines and growth factors, are two types of de novo drug resistance. The microenvironment, including conditions such as hypoxia, vascular and endosteal niches, contributes toward de novo drug resistance. Clonal evolution was associated with acquired drug resistance and classified as branching, linear, and neutral evolutions. The branching evolution is dependent on the microenvironment and escape of immunological surveillance while the linear and neutral evolution is independent of the microenvironment and associated with aggressive recurrence and poor prognosis. Proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), monoclonal antibody agents (MoAbs), and autologous stem cell transplantation (ASCT) have improved prognosis of myeloma via improvement of the microenvironment. The initial treatment plays the most important role considering de novo and acquired drug resistance and should contain PIs, IMIDs, MoAb and ASCT. This review summarizes the role of anti-myeloma agents for microenvironment and clonal evolution and treatment strategies to overcome drug resistance.

EWSR1 overexpression is a pro-oncogenic event in multiple myeloma

Multiple myeloma (MM) is cytogenetically, genetically and molecularly heterogenous even among subclones in one patient, therefore, it is essential to identify both frequent and patient-specific drivers of molecular abnormality. Following previous molecular investigations, we in this study investigated the expression patterns and function of the Ewing sarcoma breakpoint region 1 (EWSR1) gene in MM. The EWSR1 transcriptional level in CD138-positive myeloma cells was higher in 36.4% of monoclonal gammopathy of undetermined significance, in 67.4% of MM patients compared with normal plasma cells, and significantly higher in ten human myeloma-derived cell lines (HMCLs) examined. EWSR1 gene knockdown caused growth inhibition with an increase of apoptotic cells in NCI-H929 and KMS-12-BM cells. Gene expression profiling using microarray analysis suggested EWSR1 gene knockdown caused transcriptional modulation of several genes associated with processes such as cell proliferation, cell motility, cell metabolism, and gene expression. Of particular, EWSR1 gene knockdown caused upregulation of let-7c and downregulation of its known targets K-RAS and AKT. Finally, our analysis using community database suggested that high EWSR1 expression positively associates with poor prognosis and advanced disease stage in MM. These findings suggest that EWSR1 overexpression is a pro-oncogenic molecular abnormality that may participate in MM progression.

CAR T cell therapies for patients with multiple myeloma

Despite several therapeutic advances over the past decade, multiple myeloma (MM) remains largely incurable, indicating a need for new treatment approaches. Chimeric antigen receptor (CAR) T cell therapy works by mechanisms distinct from those of other MM therapies and involves the modification of patient or donor T cells to target specific cell-surface antigens. B cell maturation antigen (BCMA) is expressed only on plasma cells, a small subset of B cells and MM cells, which makes it a suitable target antigen for such therapies. At the time of writing, data from >20 clinical trials involving anti-BCMA CAR T cells have demonstrated that patients with relapsed and/or refractory MM can achieve objective responses. These early investigations have been instrumental in demonstrating short-term safety and efficacy; however, most patients do not have disease remission lasting >18 months. Attempts to reduce or delay the onset of relapsed disease are underway and include identifying additional CAR T cell target antigens and methods of enhancing BCMA expression on MM cells. Engineering CAR T cells to enhance both the activity and safety of treatment continues to be a promising avenue for improvement. In this Review we summarize data from clinical trials that have been carried out to date, describe novel antigens that could be targeted in the future, and highlight potential future innovations that could enhance the efficacy and/or reduce the toxicities associated with CAR T cell therapies.

From pathogenesis to personalized treatments of neuropathies in hematological malignancies

The peripheral nervous system may be involved at any stage in the course of several hematological diseases, the most common being monoclonal gammopathies (of undetermined significance or malignant) or lymphomas. The underlying pathogenic mechanisms are different and therapies aim at targeting the dangerous either B-cell or plasma cell clones. Recently, high-throughput technologies, and next-generation sequencing have increased our knowledge of hematological diseases pathogenesis by the identification of somatic mutation affecting pivotal signaling pathways. Accordingly, new target therapies are used that may also be borrowed for treatment of neuropathies in hematological diseases.