Four genes predict high risk of progression from smoldering to symptomatic multiple myeloma (SWOG S0120)

Diagnosis and management of smouldering myeloma: A British Society for Haematology Good Practice Paper

Multiple myeloma is a bone marrow-based plasma cell tumour that develops from asymptomatic pre-cursor conditions smouldering myeloma and monoclonal gammopathy of uncertain significance and all are characterised by the presence of a monoclonal protein in the blood. Diagnosis and distinction between these conditions is based on blood tests, the bone marrow biopsy and cross sectional imaging. There are various risk stratification models that group patients with smouldering myeloma into risk groups based on risk of progression to symptomatic disease. Management is mainly observational for patients with smouldering myeloma although clinical trials for high-risk disease may be available. Restaging is required if evidence for progression.

pyComBat, a Python tool for batch effects correction in high-throughput molecular data using empirical Bayes methods

BACKGROUND

Variability in datasets is not only the product of biological processes: they are also the product of technical biases. ComBat and ComBat-Seq are among the most widely used tools for correcting those technical biases, called batch effects, in, respectively, microarray and RNA-Seq expression data.

RESULTS

In this technical note, we present a new Python implementation of ComBat and ComBat-Seq. While the mathematical framework is strictly the same, we show here that our implementations: (i) have similar results in terms of batch effects correction; (ii) are as fast or faster than the original implementations in R and; (iii) offer new tools for the bioinformatics community to participate in its development. pyComBat is implemented in the Python language and is distributed under GPL-3.0 ( https://www.gnu.org/licenses/gpl-3.0.en.html ) license as a module of the inmoose package. Source code is available at https://github.com/epigenelabs/inmoose and Python package at https://pypi.org/project/inmoose .

CONCLUSIONS

We present a new Python implementation of state-of-the-art tools ComBat and ComBat-Seq for the correction of batch effects in microarray and RNA-Seq data. This new implementation, based on the same mathematical frameworks as ComBat and ComBat-Seq, offers similar power for batch effect correction, at reduced computational cost.

SLiM CRAB criteria revisited: temporal trends in prognosis of patients with smoldering multiple myeloma who meet the definition of ‘biomarker-defined early multiple myeloma’—a systematic review with meta-analysis

Background

Biomarker-defined patients with smoldering multiple myeloma (SMM) were included in the diagnostic category of multiple myeloma (MM) by the International Myeloma Working Group (IMWG) in 2014. This includes ≥60% bone marrow plasma cells (BMPCs), free light chain ratio (FLCratio) ≥100, and >1 MRI-defined ≥5 mm focal lesion, also called SLiM CRAB MM. We examined whether the risk of progression of SLiM CRAB MM patients to CRAB positive MM described in recent studies differs from that reported in earlier studies published before the introduction of the new diagnostic criteria.

Methods

We conducted a systematic review with meta-analysis, and included studies on Embase and PubMed (01/01/2010-01/11/2022), selecting studies with digitizable progression curves. Inconsistent studies were excluded. We created forest plots using random effects models from digitized and published data and Kaplan-Meier curves. Main outcomes were median time to progression (TTP), 2-year progression risk, and odds ratios (ORs) comparing 2-year progression risks.

Findings

Our meta-analysis including 11 studies with 3482 patients found an approximately 3-fold longer TTP and 50% lower 2-year progression risk of SliM CRAB MM patients in recent (published after 2014) compared with earlier studies. Median TTP in patients with ≥60% BMPCs was 30.31 months [18.71-62.93] in recent compared with 9.20 months [6.02-15.56] in earlier studies; the 2-year progression risk was 45.45% [20.12-62.75] compared with 86.21% [65.74-94.45] in the respective time periods. In patients with a FLCratio ≥ 100, the median TTP was 48.06 months [40.51-64.91] vs. 15.33 months [9.38-19.10], and the 2-year progression risk was 31.61% [25.30-37.39] vs. 73.00% [62.39-80.62] in recent and earlier studies, respectively. Tests for heterogeneity showed that the two time periods differed significantly in their ORs when comparing patients who met the high-and low risk criteria. No appropriate recent studies on focal lesions have been published.

Interpretation

Recent studies show significantly improved prognosis of biomarker-defined MM with ≥60% BMPCs and FLCratio ≥ 100. This warrants careful evaluation for signs of progression before treatment initiation.

Funding

Funding was provided by the Austrian Forum against Cancer.

Risk Stratification and Treatment in Smoldering Multiple Myeloma

Smoldering multiple myeloma is a heterogeneous asymptomatic precursor to multiple myeloma. Since its identification in 1980, risk stratification models have been developed using two main stratification methods: clinical measurement-based and genetics-based. Clinical measurement models can be subdivided in three types: baseline measurements (performed at diagnosis), evolving measurements (performed over time during follow-up appointments), and imaging (for example, magnetic resonance imaging). Genetic approaches include gene expression profiling, DNA/RNA sequencing, and cytogenetics. It is important to accurately distinguish patients with indolent disease from those with aggressive disease, as clinical trials have shown that patients designated as “high-risk of progression” have improved outcomes when treated early. The risk stratification models, and clinical trials are discussed in this review.

2021 European Myeloma Network review and consensus statement on smoldering multiple myeloma: how to distinguish (and manage) Dr. Jekyll and Mr. Hyde

According to the updated International Myeloma Working Group criteria, smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder characterized by an M-component >3 g/dL, bone marrow plasma cell infiltration >10% and <60%, and absence of any myeloma-defining event. Active multiple myeloma is preceded by SMM, with a median time to progression of approximately 5 years. Cases of SMM range from the extremes of "monoclonal gammopathy of undetermined significance-like", in which patients never progress during their lifetimes, to "early multiple myeloma", in which transformation into symptomatic disease, based on genomic evolution, may be rapid and devastating. Such a "split personality" makes the prognosis and management of individual patients challenging, particularly with regard to the identification and possible early treatment of high-risk SMM. Outside of clinical trials, the conventional approach to SMM generally remains close observation until progression to active multiple myeloma. However, two prospective, randomized trials have recently demonstrated a significant clinical benefit in terms of time to progression, and of overall survival in one of the two studies, for some patients with higher-risk SMM treated with lenalidomide ± dexamethasone, raising the question of whether such an approach should be considered a new standard of care. In this paper, experts from the European Myeloma Network describe current biological and clinical knowledge on SMM, focusing on novel insights into its molecular pathogenesis, new prognostic scoring systems proposed to identify SMM patients at higher risk of early transformation, and updated results of completed or ongoing clinical trials. Finally, some practical recommendations for the real-life management of these patients, based on Delphi consensus methodology, are provided.

The benefits of early intervention using lenalidomide for high-risk smoldering multiple myeloma: emerging data and its promising clinical impact

INTRODUCTION

Multiple myeloma is preceded by the early stages: monoclonal gammopathy of unknown significance (M.G.U.S.) and smoldering myeloma (S.M.M.), which are less genomically complex and where patients are overall healthier with preserved quality of life.

AREAS COVERED

This review focuses on the current evidence in risk stratification and initial therapy for these patients with the goal to delay progression to and/or cure multiple myeloma.

EXPERT OPINION

Advances in the understanding of the factors that contribute to myeloma evolution coupled with new therapeutics that have high efficacy and limited toxicity have revolutionized our approach to early myeloma. Although our current recommendation continues to be to observe S.M.M. outside of clinical trials, the clinical benefit of lenalidomide sets the stage for combinations with immunotherapy, which, in our opinion, will likely lead to regulatory approvals and more widespread treatment of early myeloma.

Plasma cells expression from smouldering myeloma to myeloma reveals the importance of the PRC2 complex, cell cycle progression, and the divergent evolutionary pathways within the different molecular subgroups

Sequencing studies have shed some light on the pathogenesis of progression from smouldering multiple myeloma (SMM) and symptomatic multiple myeloma (MM). Given the scarcity of smouldering samples, little data are available to determine which translational programmes are dysregulated and whether the mechanisms of progression are uniform across the main molecular subgroups. In this work, we investigated 223 SMM and 1348 MM samples from the University of Arkansas for Medical Sciences (UAMS) for which we had gene expression profiling (GEP). Patients were analysed by TC-7 subgroup for gene expression changes between SMM and MM. Among the commonly dysregulated genes in each subgroup, PHF19 and EZH2 highlight the importance of the PRC2.1 complex. We show that subgroup specific differences exist even at the SMM stage of disease with different biological features driving progression within each TC molecular subgroup. These data suggest that MMSET SMM has already transformed, but that the other precursor diseases are distinct clinical entities from their symptomatic counterpart.

MicroRNAs as a Potential New Preventive Approach in the Transition from Asymptomatic to Symptomatic Multiple Myeloma Disease

Simple Summary

Multiple myeloma (MM) is the second most common haematologic malignancy, and it remains an incurable disease despite the advances of novel therapies. It is characterised by a multistep process that arises from a pre-malignant asymptomatic status-defined monoclonal gammopathy of undetermined significance (MGUS), evolves to a middle stage named smouldering myeloma phase (SMM), and culminates in the active disease (MM). Identification of early and non-invasive markers of the disease progression is currently an active field of investigation. In this review, we discuss the role and significance of microRNAs (miRNAs) as potential diagnostic biomarkers to predict the clinical transition from MGUS/SMM status to MM.

Abstract

Multiple myeloma (MM) is a hematological malignancy characterised by proliferation of clonal plasma cells (PCs) within the bone marrow (BM). Myelomagenesis is a multi-step process which goes from an asymptomatic phase, defined as monoclonal gammopathy of undetermined significance (MGUS), to a smouldering myeloma (SMM) stage, to a final active MM disease, characterised by hypercalcemia, renal failure, bone lesions anemia, and higher risk of infections. Overall, microRNAs (miRNAs) have shown to significantly impact on MM tumorigenesis, as a result of miRNA-dependent modulation of genes involved in pathways known to be crucial for MM pathogenesis and disease progression. We aim to revise the literature related to the role of miRNAs as potential diagnostic and prognostic biomarkers, thus highlighting their key role as novel players within the field of MM and related premalignant conditions.

Genomics of Smoldering Multiple Myeloma: Time for Clinical Translation of Findings?

Smoldering multiple myeloma (SMM) is an asymptomatic disorder of clonal bone marrow (BM) plasma cells (PCs) in between the premalignant condition known as monoclonal gammopathy of undetermined significance and overt multiple myeloma (MM). It is characterized by a deep biological heterogeneity that is reflected in a markedly variable progression risk among patients. Recently proposed risk stratification models mainly rely on indirect markers of disease burden and are unable to identify cases in whom clonal PCs have already undergone the "malignant switch" but major clonal expansion has not occurred yet. In the last years, the application of next-generation sequencing (NGS) techniques has led to profound advances in the understanding of the molecular bases of SMM progression, and in all likelihood, it will contribute to the needed improvement of SMM prognostication. In this Review, we describe the recent advances in characterizing the genomic landscape of SMM and intrinsic determinants of its progression, highlighting their implications in terms of understanding of tumor evolution and prognostication. We also review the main studies investigating the role of the microenvironment in this early disease stage. Finally, we mention the results of the first randomized clinical trials and discuss the potential clinical translability of the genomic insights.

Identification of resistance pathways and therapeutic targets in relapsed multiple myeloma patients through single-cell sequencing

Multiple myeloma (MM) is a neoplastic plasma-cell disorder characterized by clonal proliferation of malignant plasma cells. Despite extensive research, disease heterogeneity within and between treatment-resistant patients is poorly characterized. In the present study, we conduct a prospective, multicenter, single-arm clinical trial (NCT04065789), combined with longitudinal single-cell RNA-sequencing (scRNA-seq) to study the molecular dynamics of MM resistance mechanisms. Newly diagnosed MM patients (41), who either failed to respond or experienced early relapse after a bortezomib-containing induction regimen, were enrolled to evaluate the safety and efficacy of a daratumumab, carfilzomib, lenalidomide and dexamethasone combination. The primary clinical endpoint was safety and tolerability. Secondary endpoints included overall response rate, progression-free survival and overall survival. Treatment was safe and well tolerated; deep and durable responses were achieved. In prespecified exploratory analyses, comparison of 41 primary refractory and early relapsed patients, with 11 healthy subjects and 15 newly diagnosed MM patients, revealed new MM molecular pathways of resistance, including hypoxia tolerance, protein folding and mitochondria respiration, which generalized to larger clinical cohorts (CoMMpass). We found peptidylprolyl isomerase A (PPIA), a central enzyme in the protein-folding response pathway, as a potential new target for resistant MM. CRISPR-Cas9 deletion of PPIA or inhibition of PPIA with a small molecule inhibitor (ciclosporin) significantly sensitizes MM tumor cells to proteasome inhibitors. Together, our study defines a roadmap for integrating scRNA-seq in clinical trials, identifies a signature of highly resistant MM patients and discovers PPIA as a potent therapeutic target for these tumors.

Genetic Analysis of Multiple Myeloma Identifies Cytogenetic Alterations Implicated in Disease Complexity and Progression

Multiple myeloma (MM) is a genetically heterogeneous disease characterized by genomic chaos making it difficult to distinguish driver from passenger mutations. In this study, we integrated data from whole genome gene expression profiling (GEP) microarrays and CytoScan HD high-resolution genomic arrays to integrate GEP with copy number variations (CNV) to more precisely define molecular alterations in MM important for disease initiation, progression and poor clinical outcome. We utilized gene expression arrays from 351 MM samples and CytoScan HD arrays from 97 MM samples to identify eight CNV events that represent possible MM drivers. By integrating GEP and CNV data we divided the MM into eight unique subgroups and demonstrated that patients within one of the eight distinct subgroups exhibited common and unique protein network signatures that can be utilized to identify new therapeutic interventions based on pathway dysregulation. Data also point to the central role of 1q gains and the upregulated expression of ANP32E, DTL, IFI16, UBE2Q1, and UBE2T as potential drivers of MM aggressiveness. The data presented here utilized a novel approach to identify potential driver CNV events in MM, the creation of an improved definition of the molecular basis of MM and the identification of potential new points of therapeutic intervention.

What Is New in the Treatment of Smoldering Multiple Myeloma?

Smoldering multiple myeloma (SMM), an asymptomatic plasma cell neoplasm, is currently diagnosed according to the updated IMWG criteria, which reflect an intermediate tumor mass between monoclonal gammopathy of undetermined significance (MGUS) and active MM. However, SMM is a heterogeneous entity and individual case may go from an "MGUS-like" behavior to "early MM" with rapid transformation into symptomatic disease. This wide range of clinical outcomes poses challenges for prognostication and management of individual patients. However, initial studies showed a benefit in terms of progression or even survival for early treatment of high-risk SMM patients. While outside of clinical trials the conventional approach to SMM generally remains that of close observation, these studies raised the question of whether early treatment should be offered in high-risk patients, prompting evaluation of several different therapeutic approaches with different goals. While delay of progression to MM with a non-toxic treatment is clearly achievable by early treatment, a convincing survival benefit still needs to be proven by independent studies. Furthermore, if SMM is to be considered less biologically complex than MM, early treatment may offer the chance of cure that is currently not within reach of any active MM treatment. In this paper, we present updated results of completed or ongoing clinical trials in SMM treatment, highlighting areas of uncertainty and critical issues that will need to be addressed in the near future before the "watch and wait" paradigm in SMM is abandoned in favor of early treatment.

The molecular make up of smoldering myeloma highlights the evolutionary pathways leading to multiple myeloma

Smoldering myeloma (SMM) is associated with a high-risk of progression to myeloma (MM). We report the results of a study of 82 patients with both targeted sequencing that included a capture of the immunoglobulin and MYC regions. By comparing these results to newly diagnosed myeloma (MM) we show fewer NRAS and FAM46C mutations together with fewer adverse translocations, del(1p), del(14q), del(16q), and del(17p) in SMM consistent with their role as drivers of the transition to MM. KRAS mutations are associated with a shorter time to progression (HR 3.5 (1.5–8.1), p = 0.001). In an analysis of change in clonal structure over time we studied 53 samples from nine patients at multiple time points. Branching evolutionary patterns, novel mutations, biallelic hits in crucial tumour suppressor genes, and segmental copy number changes are key mechanisms underlying the transition to MM, which can precede progression and be used to guide early intervention strategies.

Progression from asymptomatic smoldering multiple myeloma (SMM) to symptomatic Multiple Myeloma occurs at different rates in different patients. Here, the authors report fewer NRAS and FAM46C mutations and adverse translocations in SMM compared to MM, while KRAS mutations are associated with a shorter time to progression.

Treatment of Smoldering Multiple Myeloma: Expectant Observation Should Still Be the Standard

Recent clinical trials have addressed the notion of early treatment of smoldering multiple myeloma (SMM). The results evidence improvement in progression-free survival and, in one study, overall survival. Although the treatment of SMM can be considered under specific circumstances, we propose here that careful interpretation of the clinical trials and the patient-specific data are needed before recommending therapy. In particular, many questions remain regarding the best regimen to be used as well as how to adapt based on the underlying disease biology. Hematologists should have a very thorough understanding of models designed to predict the progression from SMM to multiple myeloma, because their correct interpretation is paramount to establish proper care. Although there is no doubt that treatment should be started before overt end-organ damage, we do not believe that the current data support the widespread treatment of all SMM.

How we manage smoldering multiple myeloma

Smoldering myeloma (SMM) is an asymptomatic stage characterized by bone marrow plasma cells infiltration between 10-60% in absence of myeloma-defining events and organ damage. Until the revision of criteria of MM to require treatment, two main prognostic models, not overlapping each other, were proposed and used differently in Europe and in US. Novel manageable drugs, like lenalidomide and monoclonal antibodies, with high efficacy and limited toxicity, improvement in imaging and prognostication, challenge physicians to offer early treatment to highrisk SMM. Taking advantage from the debates offered by SOHO Italy, in this review we will update the evidence and consequent clinical practices in US and Europe to offer readers a uniform view of clinical approach at diagnosis, follow-up and supportive care in the SMM setting.

Recent Advances in the Management of Smoldering Multiple Myeloma

There is remarkable progress in the treatment of multiple myeloma (MM) with significant improvement in survival in the past 10 years. Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) can evolve into symptomatic multiple myeloma (sy-MM) with organ involvement. SMM has associated with a much higher progression to MM compared to MGUS. In 2014, International Myeloma Working Group (IMWG) reclassified ultra-high-risk smoldering myeloma patients with bone marrow plasma cells > 60% or serum-free light chain ratio (FLCr) > 100 or > 1 focal bone lesion on the magnetic resonance imaging as MM. SMM is a heterogeneous disorder with probability for progression to myeloma up to 50% in the first 5 years. Several risk models and clinical features have been identified to stratify the risk of progression to MM. Thanks to advances in our understanding of the genomic profile of MM, there are several ongoing clinical trials, and genomic studies are being done to assess the risk of progression to MM and early intervention. There is still no standard criterion regarding when to start therapy. This review discusses identifying SMM patients who are at high risk of progression to sy-MM and recent development of new and early treatment strategies and ongoing clinical trials for these high-risk SMM patients.

High-risk smoldering myeloma versus early detection of multiple myeloma: Current models, goals of therapy, and clinical implications

Multiple myeloma, a bone marrow cancer, is preceded by precursor stages called monoclonal gammopathy of unknown significance and smoldering multiple myeloma. Over the past few years, highly effective and safe therapies have been made available to treat multiple myeloma. This represents a major breakthrough and has major therapeutic implications. Treatment for multiple myeloma has evolved to include treatment of precursor stages (early treatment) as these therapies are shown to be safe and effective also in smoldering myeloma. Randomized studies have shown that early treatment can delay the onset of multiple myeloma and even improve overall survival compared to observation in smoldering myeloma. The best therapeutic course and selection of patients with smoldering myeloma to treat is still a matter of debate. In this manuscript, we review the definition, management, clinical implications of smoldering myeloma and early detection of myeloma in the current context and with up-to-date data.

Timing of treatment of smoldering myeloma: delay until progression

This article has a companion Point by Mateos and González-Calle.

Early or deferred treatment of smoldering multiple myeloma: a meta-analysis on randomized controlled studies

Purpose

Smoldering multiple myeloma (SMM) is a rare asymptomatic plasma cell disorder. Even with emerging therapeutic approaches and risk stratification, the optimal time to treat SMM remains controversial. This meta-analysis aimed to compare early treatment with deferred treatment of SMM, especially high-risk SMM.

Methods

Early treatment was defined as treatment immediately after diagnosis. Deferred treatment was initiated after progression. The primary outcome was progression. Secondary outcomes were mortality, response, and safety. PubMed, EMBASE, Medline, Cochrane, and ClinicalTrials.gov databases were searched from January 1990 to March 2019. Randomized controlled trials (RCTs) comparing early treatment with deferred treatment in SMM patients were eligible. Risk ratios (RRs) with 95% confidence interval (CI) were pooled.

Results

Eight RCTs covering 885 SMM patients were included. Considering all the different treatment approaches, early treatment significantly decreased progression of SMM (RR=0.53, 95% CI 0.33-0.87, P=0.01). In subgroup analysis, melphalan plus prednisone (RR=0.22, 95% CI 0.08-0.64, P=0.005) and immuno-modulatory drugs (RR=0.43, 95% CI 0.31-0.59, P<0.00001) significantly reduced progression. However, neither mortality nor response rate was significantly affected by early treatment. In terms of high-risk SMM patients, early treatment significantly decreased both progression (RR=0.51, 95% CI 0.37-0.70, P=0.0001) and mortality (RR=0.53, 95% CI 0.29-0.96, P=0.04). Frequently seen adverse events were infection, constipation, asthenia, and second primary malignancy. A remarkably elevated risk of constipation was associated with early treatment using immuno-modulatory agents (RR=4.43, 95% CI 2.14-9.12, P<0.0001). Second primary malignancy was significantly increased with early treatment (RR=4.13, 95% CI 1.07-15.97, P=0.04). No significant difference was identified in infection or asthenia.

Conclusion

These findings suggest that early treatment could decrease progression and mortality of high-risk SMM patients with a tolerable safety profile.

Timing treatment for smoldering myeloma: is earlier better?

INTRODUCTION

In 2014, the International Myeloma Working Group determined that patients with ultra-high-risk smoldering multiple myeloma (SMM) should be considered for treatment as per patients with symptomatic multiple myeloma (MM), despite not having CRAB (hyperCalcemia, Renal insufficiency, Anemia, Bone disease) symptoms. Current research is elucidating whether patients with high-risk, and even intermediate-risk, SMM could benefit from early therapeutic strategies aimed at delaying progression to active MM and prolonging survival. Areas covered: The authors conducted a systematic literature search using PubMed to identify a series of patients with SMM in which prognostic and predictive factors for progression were investigated, plus the main clinical trials in SMM. Additionally, a search of active clinical trials in SMM was conducted at ClinicalTrials.gov. Expert opinion: Patients with high-risk SMM can benefit from active treatment strategies, which may prolong survival and, perhaps, provide a possible path to cure. Enabled by the limited toxicity of new drugs investigated in MM, this approach, together with consolidation with autologous transplantation, is under investigation by American and European groups. In patients with high-risk SMM who are not candidates for transplantation, combinations of oral drugs may prolong time to progression. In the near future, these approaches may be endorsed by results of ongoing clinical trials.

Smoldering multiple myeloma: prevalence and current evidence guiding treatment decisions

Smoldering multiple myeloma (SMM) is an asymptomatic plasma cell proliferative disorder associated with risk of progression to symptomatic multiple myeloma (MM) or amyloidosis. In comparison to monoclonal gammopathy of undetermined significance (MGUS), SMM has a much higher risk of progression to MM. Thanks to advances in our understanding of the risk factors, the subset of patients with ultra-high risk of progression to MM (80%-90% at 2 years) has been identified. The revision of the diagnostic criteria resulted in changes in the management of this cohort of patients. In contrast to the management guidelines for MGUS patients, SMM patients need to be studied more intensively in order to identify biomarkers necessary for accurate risk stratification. In this review, we focus on the risk of progression from SMM to MM, as well as the influence of early treatment on overall survival, time to progression and quality of life.

Heme oxygenase-1 nuclear translocation regulates bortezomibinduced cytotoxicity and mediates genomic instability in myeloma cells

Multiple myeloma (MM) is a clonal B-cell malignancy characterized by an accumulation of clonal plasma cells in the bone marrow leading to bone destruction and bone marrow failure. Several molecular mechanisms underlie chemoresistance among which heme oxygenase-1 (HO-1) could play a major role. The aim of the present research was to evaluate the impact of HO-1 in MM following bortezomib (BTZ) treatment and how HO-1 is implicated in the mechanisms of chemoresistance. MM cells were treated for 24h with BTZ (15 nM), a boronic acid dipeptide inhibitor of the 26S proteasome used in the treatment of patients with MM as first-line therapy. We evaluated cell viability, reactive oxygen species (ROS) formation, endoplasmic reticulum (ER) stress, HO-1 expression and compartmentalization and cellular genetic instability. Results showed that BTZ significantly reduced cell viability in different MM cell lines and induced ER-stress and ROS formation. Concomitantly, we observed a significant overexpression of both HO-1 gene and protein levels. This effect was abolished by concomitant treatment with 4-phenybutirric acid, a molecular chaperone, which is known to reduce ER-stress. Surprisingly, inhibition of HO activity with SnMP (10μM) failed to increase BTZ sensitivity in MM cells whereas inhibition of HO-1 nuclear translocation by E64d, a cysteine protease inhibitor, increased sensitivity to BTZ and decreased genetic instability as measured by cytokinesis-block micronucleus assay. In conclusion, our data suggest that BTZ sensitivity depends on HO-1 nuclear compartmentalization and not on its enzymatic activity and this finding may represent an important tool to overcome BTZ chemoresistance in MM patients.

Smoldering Multiple Myeloma: Emerging Concepts and Therapeutics

Smoldering multiple myeloma (SMM) is a pre-malignant condition with an inherent risk for progression to multiple myeloma (MM). The 2014 IMWG guidelines define smoldering multiple myeloma as a monoclonal gammopathy disorder with serum monoclonal protein (IgG or IgA) ≥30 g/L or urinary monoclonal protein ≥500 mg per 24 h and/or clonal bone marrow plasma cells 10-60 % without any myeloma-defining events or amyloidosis. The risk for progression of SMM to MM vary based on clinical, laboratory, imaging, and molecular characteristics. Observation, with periodic monitoring is the current standard of care for SMM. Over last few years, research advances in SMM have led to the delineation of newer risk factors for progression and identification of a "high-risk" group that would potentially benefit from early treatment. This review focuses on advances in the SMM risk-stratification model and recent clinical trials in this patient population.

Evolutionary biology of high-risk multiple myeloma

The outcomes for the majority of patients with myeloma have improved over recent decades, driven by treatment advances. However, there is a subset of patients considered to have high-risk disease who have not benefited. Understanding how high-risk disease evolves from more therapeutically tractable stages is crucial if we are to improve outcomes. This can be accomplished by identifying the genetic mechanisms and mutations driving the transition of a normal plasma cell to one with the features of the following disease stages: monoclonal gammopathy of undetermined significance, smouldering myeloma, myeloma and plasma cell leukaemia. Although myeloma initiating events are clonal, subsequent driver lesions often occur in a subclone of cells, facilitating progression by Darwinian selection processes. Understanding the co-evolution of the clones within their microenvironment will be crucial for therapeutically manipulating the process. The end stage of progression is the generation of a state associated with treatment resistance, increased proliferation, evasion of apoptosis and an ability to grow independently of the bone marrow microenvironment. In this Review, we discuss these end-stage high-risk disease states and how new information is improving our understanding of their evolutionary trajectories, how they may be diagnosed and the biological behaviour that must be addressed if they are to be treated effectively.

Smoldering Multiple Myeloma: Who and When to Treat

Smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder characterized by the presence of ≥ 3 g/dL serum M-protein and/or 10% to 60% bone marrow plasma cell infiltration with no myeloma-defining event. The risk of progression to active multiple myeloma (MM) is not uniform, and several markers are useful for identifying patients at high risk of progression. The definition of the disease has recently been revisited and asymptomatic MMs at 80% to 90% of progression risk at 2 years are now considered to be active MM candidates for treatment. In the future, more precise biomarkers are necessary for accurate risk stratification to plan an optimized follow-up according to the risk of progression, as well as to expand the group of patients that can obtain a benefit if they receive early treatment. A phase 3, randomized trial in high-risk patients with SMM comparing early treatment versus observation has shown a significant benefit in terms of time to progression and overall survival for early intervention and confirmatory clinical trials will definitively contribute to establish the early treatment as standard of care in high-risk SMM.

Diagnosis and management of smoldering multiple myeloma: the razor's edge between clonality and cancer

Smoldering multiple myeloma (SMM) is a rare plasma cell disorder, and as the disease is asymptomatic, diagnosis is often incidental. SMM is characterized by increased marrow infiltration by clonal plasma cells and/or elevated serum M-protein in the absence of a myeloma-defining event (MDE). In recent years, SMM has gained increased attention owing to a broadening of the criteria for MDE, which include apart from the CRAB criteria, three additional parameters. Survival advantage may be offered by early treatment in the high-risk subset, based on a single trial. In this review, we assess the risk factors and models for progression to multiple myeloma. A review of our diagnostic and management approaches to SMM is presented.

Gene Expression Profiles in Myeloma: Ready for the Real World?

Multiple myeloma is a plasma cell malignancy characterized by molecular and clinical heterogeneity. The outcome of the disease has been dramatically improved with the advent of new drugs in the past few years. However, even in this context of increasing therapeutic options, important challenges remain, such as accurately evaluating patients' prognosis and predicting sensitivity to specific treatments and drug combinations. Transcriptomic studies have largely contributed to help decipher multiple myeloma complexity, characterizing multiple myeloma subgroups distinguished by different outcomes. Microarrays and, more recently, RNA sequencing allow evaluation of expression of coding and noncoding genes, alternate splicing events, mutations, and novel transcriptome modifiers, providing new information regarding myeloma biology, prognostication, and therapy. In this review, we discuss the role and impact of gene expression profiling studies in myeloma. Clin Cancer Res; 22(22); 5434-42. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "MULTIPLE MYELOMA MULTIPLYING THERAPIES".

MGUS to myeloma: a mysterious gammopathy of underexplored significance

All cases of multiple myeloma (MM) are preceded by precursor states termed monoclonal gammopathy of undetermined significance (MGUS) or smoldering myeloma (SMM). Genetic analyses of MGUS cells have provided evidence that it is a genetically advanced lesion, wherein tumor cells carry many of the genetic changes found in MM cells. Intraclonal heterogeneity is also established early during the MGUS phase. Although the genetic features of MGUS or SMM cells at baseline may predict disease risk, transition to MM involves altered growth of preexisting clones. Recent advances in mouse modeling of MGUS suggest that the clinical dormancy of the clone may be regulated in part by growth controls extrinsic to the tumor cells. Interactions of MGUS cells with immune cells, bone cells, and others in the bone marrow niche may be key regulators of malignant transformation. These interactions involve a bidirectional crosstalk leading to both growth-supporting and inhibitory signals. Because MGUS is already a genetically complex lesion, application of new tools for earlier detection should allow delineation of earlier stages, which we term as pre-MGUS Analyses of populations at increased risk of MGUS also suggest the possible existence of a polyclonal phase preceding the development of MGUS. Monoclonal gammopathy in several patients may have potential clinical significance in spite of low risk of malignancy. Understanding the entire spectrum of these disorders may have broader implications beyond prevention of clinical malignancy.

The Changing Landscape of Smoldering Multiple Myeloma: A European Perspective

Smoldering multiple myeloma (SMM) is an asymptomatic clonal plasma cell disorder and bridges monoclonal gammopathy of undetermined significance to multiple myeloma (MM), based on higher levels of circulating monoclonal immunoglobulin and bone marrow plasmocytosis without end-organ damage. Until a Spanish study reported fewer MM-related events and better overall survival among patients with high-risk SMM treated with lenalidomide and dexamethasone, prior studies had failed to show improved survival with earlier intervention, although a reduction in skeletal-related events (without any impact on disease progression) has been described with bisphosphonate use. Risk factors have now been defined, and a subset of ultra-high-risk patients have been reclassified by the International Myeloma Working Group as MM, and thus will require optimal MM treatment, based on biomarkers that identify patients with a >80% risk of progression. The number of these redefined patients is small (∼10%), but important to unravel, because their risk of progression to overt MM is substantial (≥80% within 2 years). Patients with a high-risk cytogenetic profile are not yet considered for early treatment, because groups are heterogeneous and risk factors other than cytogenetics are deemed to weight higher. Because patients with ultra-high-risk SMM are now considered as MM and may be treated as such, concerns exist that earlier therapy may increase the risk of selecting resistant clones and induce side effects and costs. Therefore, an even more accurate identification of patients who would benefit from interventions needs to be performed, and clinical judgment and careful discussion of pros and cons of treatment initiation need to be undertaken. For the majority of SMM patients, the standard of care remains observation until development of symptomatic MM occurs, encouraging participation in ongoing and upcoming SMM/early MM clinical trials, as well as consideration of bisphosphonate use in patients with early bone loss.

Smoldering multiple myeloma risk factors for progression: a Danish population-based cohort study

Several risk scores for disease progression in patients with smoldering multiple myeloma (SMM) have been proposed; however, all have been developed using single-center registries. To examine risk factors for time to progression (TTP) to multiple myeloma (MM) for SMM, we analyzed a nationwide population-based cohort of 321 patients with newly diagnosed SMM registered within the Danish Multiple Myeloma Registry between 2005 and 2014. Significant univariable risk factors for TTP were selected for multivariable Cox regression analyses. We found that both an M-protein ≥30 g/L and immunoparesis significantly influenced TTP (HR 2.7, 95%CI (1.5;4.7), P = 0.001, and HR 3.3, 95%CI (1.4;7.8), P = 0.002, respectively). High free light chain (FLC) ratio did not significantly influence TTP in our cohort. Therefore, our data do not support recent IMWG proposal of identifying patients with FLC ratio above 100 as having ultra high-risk of transformation to MM. Using only immunoparesis and M-protein ≥30 g/L, we created a scoring system to identify low-, intermediate-, and high-risk SMM. This first population-based study of patients with SMM confirms that an M-protein ≥30 g/L and immunoparesis remain important risk factors for progression to MM.