Role of receptor activator of nuclear factor-kappa B ligand (RANKL), osteoprotegerin and macrophage protein 1-alpha (MIP-1a) in monoclonal gammopathy of undetermined significance (MGUS)

Monoclonal Gammopathy of Undetermined Significance and Associated Cardiovascular Outcomes in a Hospital Setting-A Fresh Perspective

There is a paucity of data on the cardiovascular implications of monoclonal gammopathy of undetermined significance, especially among hospitalized patients. Our study aimed to investigate the association between MGUS and cardiovascular outcomes in a hospital setting using the National Inpatient Sample database. MGUS patients were sampled using ICD-10 codes. The patients were stratified into two cohorts based on the presence or absence of MGUS. Comorbidities and cardiovascular outcomes were collected using ICD 10 DM codes. CV outcomes were evaluated before and after 1:1 matching for age, gender, and race. Furthermore, a sensitivity analysis was performed on the matched population, which excluded patients with diabetes mellitus, prior myocardial infarction, chronic kidney disease (stages 3-5), dialysis, hypertension, obesity, metabolic syndrome, cancer, antiplatelets, and oral anticoagulant use and was adjusted for smoking, dyslipidemia, and aspirin use to evaluate the cardiovascular outcomes. MGUS patients had more heart failure, atrial fibrillation, venous thromboembolism, aortic aneurysm, aortic stenosis, aortic regurgitation, mitral stenosis, mitral regurgitation, conduction disorder, cor pulmonale, peripheral vascular disease, and acute myocardial infarction. After matching, MGUS was associated with heart failure, atrial fibrillation, venous thromboembolism, aortic stenosis, mitral regurgitation, conduction disorder, cor pulmonale, and peripheral vascular disease. MGUS was linked to a wide spectrum of cardiovascular diseases in an inpatient setting. Further studies are needed to formulate appropriate recommendations for the screening and management of cardiovascular complications in individuals with MGUS.

Monoclonal Gammopathy of Undetermined Cardiovascular Significance; Current Evidence and Novel Insights

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant condition characterized by the presence of low levels of a monoclonal protein in the serum and a low percentage of clonal plasma cells in the bone marrow. MGUS may progress to multiple myeloma or other plasma cell disorders at a rate of 1% annually. However, MGUS may also have adverse effects on the cardiovascular system independent of its malignant potential. Emerging data have shown that MGUS is associated with cardiovascular disease. The mechanisms underlying this association are not fully understood but may involve genetic abnormalities, vascular calcification, cryoglobulinemia, cold agglutinin disease, autoantibodies and the direct or indirect effects of the monoclonal protein on the vascular endothelium. Herein, we review current evidence in this field and we suggest that patients with MGUS may benefit from regular cardiovascular risk assessment to prevent severe cardiovascular complications, in parallel with close hematological follow-up to monitor potential disease progression.

Monoclonal Gammopathy of Undetermined Significance: A Comprehensive Review

Monoclonal Gammopathy of Undetermined Significance (MGUS) is an asymptomatic premalignant plasma cell dyscrasia with a predominate rise of the IgG immunoglobulin fraction without end-organ damage, often diagnosed incidentally. Despite its progression into various subsequent forms of hematological malignancies, MGUS remains underdiagnosed. A literature search was conducted using the Medline, Cochrane, Embase, and Google Scholar databases, including articles published until December 2022. Keywords used encompassed "Monoclonal Gammopathy of Undetermined Significance," "Plasma Cell dyscrasia," "Monoclonal gammopathy of renal significance," and "IgM Monoclonal gammopathy of Undetermined Significance," This study aimed to conduct a critical review to update knowledge regarding the pathophysiology, risk factors, clinical features, diagnostic protocols, complications, and current and novel treatments for MGUS. We recommend a multidisciplinary approach to manage MGUS due to the complexity of the illness's etiology, diagnosis, and therapy. This comprehensive review also highlights future prospects, such as developing screening protocols for at-risk populations, prevention of disease progression by early diagnosis through genome-wide association studies, and management using Daratumumab and NSAIDs.

Monoclonal Gammopathies and the Bone Marrow Microenvironment: From Bench to Bedside and Then Back Again

Multiple myeloma (MM) is an incurable hematologic malignancy characterized by a multistep evolutionary pathway, with an initial phase called monoclonal gammopathy of undetermined significance (MGUS), potentially evolving into the symptomatic disease, often preceded by an intermediate phase called "smoldering" MM (sMM). From a biological point of view, genomic alterations (translocations/deletions/mutations) are already present at the MGUS phase, thus rendering their role in disease evolution questionable. On the other hand, we currently know that changes in the bone marrow microenvironment (TME) could play a key role in MM evolution through a progressive shift towards a pro-inflammatory and immunosuppressive shape, which may drive cancer progression as well as clonal plasma cells migration, proliferation, survival, and drug resistance. Along this line, the major advancement in MM patients' survival has been achieved by the introduction of microenvironment-oriented drugs (including immunomodulatory drugs and monoclonal antibodies). In this review, we summarized the role of the different components of the TME in MM evolution from MGUS as well as potential novel therapeutic targets/opportunities.

Cancer-related hypercalcemia and potential treatments

Cancer-related hypercalcemia is a common finding typically seen in patients with advanced cancer and occurs in about 20 to 30 percent of cases. The most common cause of hypercalcemia in hospitalized patients is hypercalcemia due to malignancy.This clinical problem is seen in patients with both solid tumors and patients with hematologic malignancies. Hypercalcemia is associated with a poor prognosis in oncology patients. This pathologic condition can occur due to many different mechanisms but is usually caused by abnormal calcium use resulting from bone resorption, intestinal absorption, or renal excretion. Hypercalcemia may present with a wide range of symptoms ranging from gastrointestinal system symptoms to neurologic symptoms. Timely diagnosis and initiation of treatment by the physician significantly reduce the risk of complications. Treatment aims to decrease serum calcium by increasing calciuresis, decreasing bone resorption, and decreasing intestinal calcium absorption. The mainstays of treatment are IV hydration, bisphosphonates and calcitonin, denosumab, and in some patients, prednisone, and cinacalcet. Patients with underlying advanced kidney disease and refractory severe hypercalcemia should be evaluated for hemodialysis. Every physician dealing with oncology patients should know the fastest and most effective management of hypercalcemia. We aimed to contribute in this sense.

Pathophysiology and therapeutic advances in myeloma bone disease

Bone disease is the most common complication in patients with multiple myeloma (MM), and it may lead to skeletal-related events (SREs) such as bone pain, pathological fractures, and spinal cord compression, which impair a patients' quality of life and survival. The pathogenesis of myeloma bone disease (MBD) involves disruption of bone reconstitution balance including excessive activation of osteoclasts, inhibition of osteoblasts, and participation of osteocytes and bone marrow stromal cells. Various factors, such as the receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG), dickkopf-1 (DKK-1), sclerostin, and activin-A, are involved in the development of MBD. Bisphosphonates and the anti-RANKL antibody denosumab are currently the main treatment options for MBD, delaying the onset of SREs. Denosumab is preferred in patients with MM and renal dysfunction. Although effective drugs have been approved, antimyeloma therapy is the most important method for controlling bone disease.

Cardiovascular Morbidity in Monoclonal Gammopathy of Undetermined Significance: A Danish Nationwide Study

Background

Monoclonal gammopathy of undetermined significance (MGUS) is associated with renal dysfunction, inflammation, and increased cardiovascular mortality, but the cardiovascular risks are not fully understood.

Objectives

The authors explored the association of MGUS with a spectrum of cardiovascular diseases using the Danish nationwide databases.

Methods

Between 1995 and 2018, patients 18 years and older with MGUS were age- and sex-matched (1:10) with control patients and followed prospectively until December 31, 2018, for the occurrence of cardiovascular diseases. Patients diagnosed with multiple myeloma, lymphoma, or amyloidosis were excluded. Multivariable adjusted hazard ratios (HRs) for cardiovascular outcomes were estimated using Cox proportional hazard regression.

Results

Patients with MGUS (n = 8,189; mean age 69.8 ± 11.7 years; 51.2% male) had higher prevalence of cardiovascular risk factors at baseline, including hypertension (48.0% vs 38.5%) and type 2 diabetes (13.0% vs 9.3%), compared with control patients. Outcomes included an increased risk of heart failure (HR: 1.55; 95% CI: 1.41-1.69), acute myocardial infarction (HR: 1.22; 95% CI: 1.06-1.40), ischemic stroke (HR: 1.16; 95% CI: 1.03-1.30), atrial fibrillation (HR: 1.32; 95% CI: 1.23-1.42), aortic aneurysm (HR: 1.55; 95% CI: 1.28-1.89), aortic stenosis (HR: 1.60; 95% CI: 1.41-1.82), aortic regurgitation (HR: 1.67; 95% CI: 1.34-2.07), heart block (HR: 1.32; 95% CI: 1.08-1.61), peripheral artery disease (HR: 1.69; 95% CI: 1.47-1.95), cor pulmonale (HR: 2.06; 95% CI: 1.55-2.73), and venous thromboembolism (HR: 1.43; 95% CI: 1.24-1.65). A sensitivity analysis including only patients without certain comorbidities (type 2 diabetes, hypertension, acute myocardial infarction, and chronic kidney disease) yielded similar results.

Conclusions

MGUS is associated with a broad spectrum of cardiovascular diseases, with greater relative risks observed for diseases previously associated with infiltrative and inflammatory disorders. Further studies are warranted to explore the underlying mechanisms.

[Monoclonal gammopathy of (un)known significance]

Monoclonal gammopathies are a frequently diagnosed entity. However, the diagnosis is not always clinically relevant. The diagnosis of a monoclonal gammopathy requires serum electrophoresis, immunofixation and free light chain measurement. Sometimes, monoclonal gammopathies occur in the course of transient or autoimmune inflammation. Further diagnostics should only be performed after risk assessment according to Mayo criteria. In non-low risk patients, a symptomatic myeloma has to be ruled out via SLiM-CRAB criteria. The diagnostic work-up should include whole-body MRI and a bone marrow puncture as well as a 24 h urine sample. If it does not imply myeloma, the diagnosis of MGUS is confirmed and a follow-up after 6 months is recommended. After that, low-risk patients only need SLiM-CRAB screening at clinical signs of progression. All other patients should receive serologic follow-ups once a year. Importantly, MGUS patients show higher morbidity. Amongst a higher prevalence of osteoporosis and immunodeficiency, a wide array of MGUS-associated diseases such as AL amyloidosis, deposition diseases and Fc binding-dependent effects can occur. This article gives an overview over the work-up, observation and caveats of monoclonal gammopathy of (un)known significance.

Reviewing the Significance of Vitamin D Substitution in Monoclonal Gammopathies

Vitamin D is a steroid hormone that is essential for bone mineral metabolism and it has several other effects in the body, including anti-cancer actions. Vitamin D causes a reduction in cell growth by interrupting the cell cycle. Moreover, the active form of vitamin D, i.e., 1,25-dihydroxyvitamin D, exerts various effects via its interaction with the vitamin D receptor on the innate and adaptive immune system, which could be relevant in the onset of tumors. Multiple myeloma is a treatable but incurable malignancy characterized by the growth of clonal plasma cells in protective niches in the bone marrow. In patients affected by multiple myeloma, vitamin D deficiency is commonly correlated with an advanced stage of the disease, greater risk of progression, the development of pathological fractures, and a worse prognosis. Changes in the vitamin D receptor often contribute to the occurrence and progress of deficiencies, which can be overcome by supplementation with vitamin D or analogues. However, in spite of the findings available in the literature, there is no clear standard of care and clinical practice varies. Further research is needed to better understand how vitamin D influences outcomes in patients with monoclonal gammopathies.

Monocyte Subsets and Serum Inflammatory and Bone-Associated Markers in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

BACKGROUND

Monocyte/macrophages have been shown to be altered in monoclonal gammopathy of undetermined significance (MGUS), smoldering (SMM) and active multiple myeloma (MM), with an impact on the disruption of the homeostasis of the normal bone marrow (BM) microenvironment.

METHODS

We investigated the distribution of different subsets of monocytes (Mo) in blood and BM of newly-diagnosed untreated MGUS (n = 23), SMM (n = 14) and MM (n = 99) patients vs. healthy donors (HD; n = 107), in parallel to a large panel of cytokines and bone-associated serum biomarkers.

RESULTS

Our results showed normal production of monocyte precursors and classical Mo (cMo) in MGUS, while decreased in SMM and MM (p ≤ 0.02), in association with lower blood counts of recently-produced CD62L⁺ cMo in SMM (p = 0.004) and of all subsets of (CD62L⁺, CD62L^- and FcεRI⁺) cMo in MM (p ≤ 0.02). In contrast, intermediate and end-stage non-classical Mo were increased in BM of MGUS (p ≤ 0.03), SMM (p ≤ 0.03) and MM (p ≤ 0.002), while normal (MGUS and SMM) or decreased (MM; p = 0.01) in blood. In parallel, increased serum levels of interleukin (IL)1β were observed in MGUS (p = 0.007) and SMM (p = 0.01), higher concentrations of serum IL8 were found in SMM (p = 0.01) and MM (p = 0.002), and higher serum IL6 (p = 0.002), RANKL (p = 0.01) and bone alkaline phosphatase (BALP) levels (p = 0.01) with decreased counts of FcεRI⁺ cMo, were restricted to MM presenting with osteolytic lesions. This translated into three distinct immune/bone profiles: (1) normal (typical of HD and most MGUS cases); (2) senescent-like (increased IL1β and/or IL8, found in a minority of MGUS, most SMM and few MM cases with no bone lesions); and (3) pro-inflammatory-high serum IL6, RANKL and BALP with significantly (p = 0.01) decreased blood counts of immunomodulatory FcεRI⁺ cMo-, typical of MM presenting with bone lesions.

CONCLUSIONS

These results provide new insight into the pathogenesis of plasma cell neoplasms and the potential role of FcεRI⁺ cMo in normal bone homeostasis.

Controversies in the use of new bone-modifying therapies in multiple myeloma

Bone-modifying therapies are essential in the treatment of patients with multiple myeloma. Zoledronic acid is preferred over other bisphosphonates due to its superiority in reducing the incidence of skeletal-related events and improving survival. The anti-receptor activator of nuclear factor-κΒ ligand (RANKL)-targeted agent denosumab has shown its non-inferiority compared to bisphosphonates in preventing skeletal-related events among newly diagnosed patients with myeloma bone disease. Denosumab may confer a survival benefit in patients eligible for autologous transplantation. Denosumab may present a safer profile for patients with renal impairment. Discontinuation of bone-directed therapies can be considered for patients with deep responses and after an adequate time period on treatment; however, a rebound effect may become evident especially in the case of denosumab. Three-monthly infusions of zoledronic acid or at-home denosumab administration should be considered during the coronavirus disease 2019 (COVID-19) pandemic. Measures to prevent hypocalcaemia, renal toxicity and osteonecrosis of the jaw are important for all bone-modifying agents.

Pathogenic Mechanisms of Myeloma Bone Disease and Possible Roles for NRF2

Osteolytic bone lesions are one of the central features of multiple myeloma (MM) and lead to bone pain, fractures, decreased quality of life, and decreased survival. Dysfunction of the osteoclast (OC)/osteoblast (OB) axis plays a key role in the development of myeloma-associated osteolytic lesions. Many signaling pathways and factors are associated with myeloma bone diseases (MBDs), including the RANKL/OPG and NF-κB pathways. NRF2, a master regulator of inflammatory signaling, might play a role in the regulation of bone metabolism via anti-inflammatory signaling and decreased reactive oxygen species (ROS) levels. The loss of NRF2 expression in OCs reduced bone mass via the RANK/RANKL pathway and other downstream signaling pathways that affect osteoclastogenesis. The NRF2 level in OBs could interfere with interleukin (IL)-6 expression, which is associated with bone metabolism and myeloma cells. In addition to direct impact on OCs and OBs, the activity of NRF2 on myeloma cells and mesenchymal stromal cells influences the inflammatory stress/ROS level in these cells, which has an impact on OCs, OBs, and osteocytes. The interaction between these cells and OCs affects the osteoclastogenesis of myeloma bone lesions associated with NRF2. Therefore, we have reviewed the effects of NRF2 on OCs and OBs in MBDs.

Monoclonal Gammopathy of Undetermined Significance (MGUS)-Not So Asymptomatic after All

Monoclonal Gammopathy of Undetermined Significance (MGUS) is considered to be a benign precursor condition that may progress to a lymphoproliferative disease or multiple myeloma. Most patients do not progress to an overt condition, but nevertheless, MGUS is associated with a shortened life expectancy and, in a minority of cases, a number of co-morbid conditions that include an increased fracture risk, renal impairment, peripheral neuropathy, secondary immunodeficiency, and cardiovascular disease. This review aims to consolidate current evidence for the significance of these co-morbidities before considering how best to approach these symptoms and signs, which are often encountered in primary care or within a number of specialties in secondary care.

Monoclonal antibodies against RANKL and sclerostin for myeloma-related bone disease: can they change the standard of care?

Introduction: Over 80% of the patients with multiple myeloma (MM) develop myeloma bone disease (MBD) during the disease course. The clinical consequences include serious skeletal-related events (SRE) that impact survival and quality of life. Bisphosphonates are the mainstay in the treatment of MBD. Currently, new therapeutic strategies are being introduced and broaden the therapeutic options in MBD. Areas covered: The purpose of this review is to summarize the current clinical management of MBD and present novel data regarding monoclonal antibodies against the receptor activator of NF-kappa B ligand (RANKL) and sclerostin that may change the clinical practice. Expert opinion: Our better understanding of the pathophysiology of MBD has identified several factors as potential therapeutic targets. Recent data have shown that the RANKL inhibitor denosumab constitutes a new promising option. The non-inferiority compared with bisphosphonates in terms of SRE prevention, the potential survival benefit, the convenience of subcutaneous administration, and the favorable toxicity profile makes denosumab a valuable alternative for physicians in the current treatment of MBD. Anti-sclerostin antibodies are currently under clinical development. Further investigations are needed to address open questions in the field including the value of anabolic agents combined with anti-resorptive and anti-MM drugs in MBD.

Monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma cell dyscrasia that consistently precedes multiple myeloma (MM) with a 1% risk of progression per year. Recent advances have improved understanding of the complex genetic and immunologic factors that permit progression from the aberrant plasma cell clone to MGUS and overt MM. Additional evidence supports bidirectional interaction of MGUS cells with surrounding cells in the bone marrow niche that regulates malignant transformation. However, there are no robust prognostic biomarkers. Herein we review the current body of literature on the biology of MGUS and provide a rationale for the improved identification of high-risk MGUS patients who may be appropriate for novel clinical interventions to prevent progression or eradicate premalignant clones prior to the development of overt MM.

Disrupted radial and tibial microarchitecture in patients with monoclonal gammopathy of undetermined significance

Patients with monoclonal gammopathy of undetermined significance (MGUS) had abnormalities in volumetric BMD (vBMD), microarchitecture, and stiffness at both the radius and tibia by high-resolution peripheral quantitative CT compared to matched controls. This is the first report demonstrating that patients with MGUS have microarchitectural deficits at multiple skeletal sites.

INTRODUCTION

Fracture risk is elevated in patients with monoclonal gammopathy of undetermined significance (MGUS). However, the pathogenesis of bone disease in these patients is poorly understood. Prior work using high-resolution peripheral CT (HRpQCT) demonstrated abnormal microarchitecture at the radius, with predominantly cortical abnormalities. We hypothesized that patients with MGUS have abnormal microarchitecture at both radius and tibia compared to controls, reflecting global skeletal effects of the disease.

METHODS

This case-control study enrolled 36 subjects; patients with MGUS (n = 12) were matched 1:2 by age, sex, and race to controls (n = 24). Areal BMD (aBMD) was measured by DXA, vBMD, and microarchitecture by HRpQCT, and whole bone stiffness by finite element analysis. Serum was drawn for markers of bone metabolism and inflammation.

RESULTS

By DXA, MGUS patients had lower aBMD at the lumbar spine, femoral neck, and 1/3 radius. Markers of bone metabolism and inflammation did not differ. By HRpQCT at the radius, MGUS patients had lower total, trabecular and cortical density, lower trabecular number, and greater trabecular separation and heterogeneity. At the tibia, MGUS patients had lower total and trabecular density, lower trabecular number, greater separation and heterogeneity, and lower whole bone stiffness.

CONCLUSIONS

Patients with MGUS had lower vBMD, cortical, and trabecular abnormalities at the radius compared to matched controls. At the tibia, trabecular abnormalities predominated. These results suggest that in addition to previously described cortical deficits, deterioration of trabecular bone may contribute to a generalized skeletal fragility in patients with MGUS.

Contributions of the Bone Microenvironment to Monoclonal Gammopathy of Undetermined Significance Pathogenesis

PURPOSE OF REVIEW

MGUS (monoclonal gammopathy of undetermined significance) is a plasma cell disorder characterized by a moderate increase in serum monoclonal protein (≤ 3 g/dL), an increase in bone marrow plasma cell infiltration (≤ 10%) and the absence of any end-organ damage. Although MGUS is considered a benign condition, evidence for clinical consequences is increasing. In this review, we examine the most recent evidence regarding MGUS manifestations and risks and present an overview of MGUS population studies as related to bone disease. Data reveals important MGUS-related bone alterations that may contribute to disease pathogenesis.

RECENT FINDINGS

MGUS patients present a rate of 1% per year risk of progression to the more aggressive multiple myeloma (MM) and therefore research has focused on the study of risk factors and the events leading to this progression. However, the exact health implications of MGUS itself and the mechanisms behind them remain unclear. It is now evident that the bone microenvironment plays a key role in hematologic cancers and other oncogenic processes leading to bone metastasis.

What is the significance of monoclonal gammopathy of undetermined significance?

Monoclonal gammopathy of undetermined significance (MGUS) is characterised by the presence of a monoclonal paraprotein in the blood, without the characteristic end organ damage seen in multiple myeloma. MGUS is more common in older age groups and has a risk of progression to myeloma of 1% per year. Population screening is not currently recommended, but retrospective studies have suggested improvements in myeloma outcomes in those under MGUS follow-up; in addition, MGUS has associated complications, including fracture, osteoporosis, renal disease and infection, which can be treated. Given this increasing evidence of disease related directly to MGUS, strategies for early identification might be needed. In this review, we discuss the complications of MGUS and whether MGUS fulfils the criteria needed to implement a screening programme. We also highlight areas where more evidence is needed, including identification of a higher risk population to make screening more practical and economically viable.

Role of the RANK/RANKL Pathway in Multiple Myeloma

Receptor activator of nuclear factor-kappa B (RANK) and its ligand, RANKL, are expressed in a variety of tissues throughout the body; their primary role is in the regulation of bone remodeling and development of the immune system. Consistent with these functions, evidence exists for a role of RANK/RANKL in all stages of tumorigenesis, from cell proliferation and carcinogenesis to epithelial-mesenchymal transition to neoangiogenesis and intravasation to metastasis to bone resorption and tumor growth in bone. Results from current studies also point to a role of RANK/RANKL signaling in patients with multiple myeloma, who have increased serum levels of soluble RANKL and an imbalance in RANKL and osteoprotegerin. Current therapies for patients with multiple myeloma demonstrate that RANKL may be released by tumor cells or osteoprogenitor cells. This article will review currently available evidence supporting a role for RANK/RANKL signaling in tumorigenesis, with a focus on patients with multiple myeloma.

Mesenchymal stem cells in multiple myeloma: a therapeutical tool or target?

Multiple myeloma (MM) is a malignant plasma cell (PC) disorder, characterized by a complex interactive network of tumour cells and the bone marrow (BM) stromal microenvironment, contributing to MM cell survival, proliferation and chemoresistance. Mesenchymal stem cells (MSCs) represent the predominant stem cell population of the bone marrow stroma, capable of differentiating into multiple cell lineages, including fibroblasts, adipocytes, chondrocytes and osteoblasts. MSCs can migrate towards primary tumours and metastatic sites, implying that these cells might modulate tumour growth and metastasis. However, this issue remains controversial and is not well understood. Interestingly, several recent studies have shown functional abnormalities of MM patient-derived MSCs indicating that MSCs are not just by-standers in the BM microenvironment but rather active players in the pathophysiology of this disease. It appears that the complex interaction of MSCs and MM cells is critical for MM development and disease outcome. This review will focus on the current understanding of the biological role of MSCs in MM as well as the potential utility of MSC-based therapies in this malignancy.

Biology and treatment of myeloma related bone disease

Myeloma bone disease (MBD) is the most common complication of multiple myeloma (MM), resulting in skeleton-related events (SREs) such as severe bone pain, pathologic fractures, vertebral collapse, hypercalcemia, and spinal cord compression that cause significant morbidity and mortality. It is due to an increased activity of osteoclasts coupled to the suppressed bone formation by osteoblasts. Novel molecules and pathways that are implicated in osteoclast activation and osteoblast inhibition have recently been described, including the receptor activator of nuclear factor-kB ligand/osteoprotegerin pathway, activin-A and the wingless-type signaling inhibitors, dickkopf-1 (DKK-1) and sclerostin. These molecules interfere with tumor growth and survival, providing possible targets for the development of novel drugs for the management of lytic disease in myeloma but also for the treatment of MM itself. Currently, bisphosphonates are the mainstay of the treatment of myeloma bone disease although several novel agents such as denosumab and sotatercept appear promising. This review focuses on recent advances in MBD pathophysiology and treatment, in addition to the established therapeutic guidelines.

Prognostic Biomarkers in the Progression From MGUS to Multiple Myeloma: A Systematic Review

Multiple myeloma (MM), characterized by malignant plasma cells in the bone marrow, is consistently preceded by asymptomatic premalignant stage monoclonal gammopathy of undetermined significance (MGUS). These MGUS patients have an annual risk of 1% to progress to MM. Clinical, imaging, and genomic (genetic and epigenetic) factors were identified, whose presence increased the risk of progression from MGUS to MM. In this systematic review we summarize the currently identified clinical, imaging, and genomic biomarkers suggested to increase the progression risk or shown to be differentially expressed/present between both cohorts of patients. Despite the wide range of proposed markers, there are still no reliable biomarkers to individually predict which MGUS patient will progress to MM and which will not. Research on biomarkers in the progression from MGUS to MM will give more insight in the unknown pathogenesis of this hematological malignancy. This would improve research by elucidating new pathways and potential therapeutic targets as well as clinical management by closer follow-up and earlier treatment of high-risk MGUS patients.

A role for bone turnover markers β-CrossLaps (CTX) and amino-terminal propeptide of type I collagen (PINP) as potential indicators for disease progression from MGUS to multiple myeloma

Multiple myeloma (MM) is characterized by bone lesions arising due to unbalanced bone remodeling. Changes in the bone formation marker amino-terminal propeptide of type I collagen (PINP) and the bone resorption marker β-CrossLaps (CTX) reflect physiologic bone turnover. Whether PINP and CTX have a role in disease progression from monoclonal gammopathy of undetermined significance (MGUS) to MM is unknown. In this cross-sectional follow-up study, 241 patients with MM or MGUS were included. Serum levels of PINP and CTX were significantly higher in MM patients compared to MGUS. Moreover, increasing concentrations of PINP and CTX were observed in those MGUS patients progressing to MM, whereas PINP and CTX levels remained unchanged in MGUS patients with stable disease. In conclusion, these data indicate a potential role of PINP and CTX as biomarkers for the progression of MGUS to MM.

Bone disease in monoclonal gammopathy of undetermined significance: results from a screened population-based study

Previous studies have shown that individuals with monoclonal gammopathy of undetermined significance (MGUS) have an increased risk of fractures, although the underlying mechanisms remain unknown. Our aim was to analyze bone mineral density (BMD), bone volume, and risk of fractures among individuals with MGUS. We performed a screening using the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study cohort, consisting of 5764 elderly individuals, identifying 300 individuals with MGUS, and 275 with light-chain MGUS. Quantitative computerized tomography was performed in the lumbar spine and hip to evaluate BMD and bone geometry. Analysis of variance and the Tukey honest significance test were used to compare the groups. Hospital records were used to record fractures, with a mean follow-up of 6.9 years. Cox proportional hazard was used to compare fracture risk. No difference was found in BMD between subjects with MGUS and others in the spine (P = .34) or in total hip (P = .30). Individuals with MGUS had a significant increase in bone volume compared with others in the spine (P < .001) and total hip (P < .001). Overall, the risk of fractures was not significantly increased in individuals with MGUS (hazard ratio [HR], 1.19; 95% confidence interval [CI], 0.94-1.50). Men with MGUS had a significantly increased fracture risk, compared with other men (HR, 1.46; 95% CI, 1.03-2.08). Our results show that although individuals with MGUS do not have decreased BMD, bone volume is increased, and MGUS men have a 50% increased fracture risk. These results indicate that bone disease and fractures in MGUS differ from processes known from osteoporosis.

Down-regulation of osteoprotegerin expression as a novel biomarker for colorectal carcinoma

A better understanding of tumor biology is important in the identification of molecules that are down-regulated in malignancy and in determining their role in tumor suppression. The aim of this study was to analyze osteoprotegerin (OPG) expression in colorectal carcinoma (CRC) and to investigate the underlying mechanism for changes in the expression of OPG. OPG expression was assessed in CRC tissue samples and cell lines. The methylation status of the OPG promoter region was determined, and the effects of demethylation on OPG expression were analyzed. The effects of recombinant OPG (rOPG) administration on cellular functions were also investigated. Clinical and prognostic implications of OPG protein expression in CRC patients were analyzed. The CRC tissues and cells showed significantly lower OPG expression. Pyrosequencing of OPG-silenced CRC cells revealed that the OPG gene promoter was highly methylated. Treatment with demethylating agent significantly elevated OPG mRNA and protein expression. rOPG significantly decreased cell viability and MMP-2 and VEGF-A production in CRC cells. Reduced OPG immunoreactivity was associated with aggressive oncogenic behavior in CRC. Also, OPG expression was found to be an independent predictor of recurrent hepatic metastasis and independent prognostic factor for worse survival rates. We demonstrated that OPG silencing in CRC occurs through epigenetic repression, and is involved in the development and progression of CRC. Our data suggest that OPG is a novel prognostic biomarker and a new therapeutic target for the treatment of patients with CRC.

Mechanisms of bone destruction in multiple myeloma

Osteolytic bone disease is a frequent complication of multiple myeloma, resulting in skeletal complications that are a significant cause of morbidity and mortality. It is the result of an increased activity of osteoclasts, which is not followed by reactive bone formation by osteoblasts. Recent studies have revealed novel molecules and pathways that are implicated in osteoclast activation and osteoblast inhibition. Among them, the most important include the receptor activator of nuclear factor-kappa B ligand/osteoprotegerin pathway, the macrophage inflammatory proteins and the activin-A that play a crucial role in osteoclast stimulation in myeloma, while the wingless-type (Wnt) signalling inhibitors (sclerostin and dickkopf-1) along with the growth factor independence-1 are considered the most important factors for the osteoblast dysfunction of myeloma patients. Finally, the role of osteocytes, which is the key cell for normal bone remodelling, has also revealed during the last years through their interaction with myeloma cells that leads to their apoptosis and the release of RANKL and sclerostin maintaining bone loss in these patients. This review focuses on the latest available data for the mechanisms of bone destruction in multiple myeloma.

Bone Disease in Multiple Myeloma

Bone involvement represented by osteolytic bone disease (OBD) or osteopenia is one of the pathognomonic and defining characteristics of multiple myeloma (MM). Nearly 90 % of patients with MM develop osteolytic bone lesions, frequently complicated by skeletal-related events (SRE) such as severe bone pain, pathological fractures, vertebral collapse, hypercalcemia, and spinal cord compression. All of these not only result in a negative impact on quality of life but also adversely impact overall survival. OBD is a consequence of increased osteoclast (OC) activation along with osteoblast (OB) inhibition, resulting in altered bone remodeling. OC number and activity are increased in MM via cytokine deregulation within the bone marrow (BM) milieu, whereas negative regulators of OB differentiation suppress bone formation. Inhibition of osteolysis and stimulation of OB differentiation leads to reduced tumor growth in vivo. Therefore, novel agents targeting OBD are promising therapeutic strategies not only for the treatment of MM OBD but also for the treatment of MM. Several novel agents in addition to bisphosphonates are currently under investigation for their positive effect on bone remodeling via OC inhibition or OB stimulation. Future studies will look to combine or sequence all of these agents with the goal of not only alleviating morbidity from MM OBD but also capitalizing on the resultant antitumor activity.

Osteolytic lesions, cytogenetic features and bone marrow levels of cytokines and chemokines in multiple myeloma patients: Role of chemokine (C-C motif) ligand 20

The relationship between bone marrow (BM) cytokine and chemokine levels, cytogenetic profiles and skeletal involvement in multiple myeloma (MM) patients is not yet defined. This study investigated a cohort of 455 patients including monoclonal gammopathy of uncertain significance (MGUS), smoldering MM and symptomatic MM patients. Skeletal surveys, positron emission tomography (PET)/computerized tomography (CT) and magnetic resonance imaging (MRI) were used to identify myeloma bone disease. Significantly higher median BM levels of both C-C motif Ligand (CCL)3 and CCL20 were found in MM patients with radiographic evidence of osteolytic lesions as compared with those without, and in all MM patients with positive PET/CT scans. BM levels of CCL3, CCL20, Activin-A and Dickkopf-1 (DKK-1) were significantly higher in patients with high bone disease as compared with patients with low bone disease. Moreover, CCL20 BM levels were significant predictors of osteolysis on X-rays by multivariate logistic analysis. On the other hand, DKK-1 levels were related to the presence of MRI lesions independently of the osteolysis at the X-rays. Our data define the relationship between bone disease and the BM cytokine and chemokine patterns highlighting the tight relationship between CCL20 BM levels and osteolysis in MM.

Factors associated with an increased risk of vertebral fracture in monoclonal gammopathies of undetermined significance

Monoclonal gammopathies of undetermined significance (MGUS) have been shown to be associated with an increased risk of fractures. This study describes prospectively the bone status of MGUS patients and determines the factors associated with vertebral fracture. We included prospectively 201 patients with MGUS, incidentally discovered, and with no known history of osteoporosis: mean age 66.6±12.5 years, 48.3% women, 51.7% immunoglobulin G (IgG), 33.3% IgM and 10.4% IgA. Light chain was kappa in 64.2% patients. All patients had spinal radiographs and bone mineral density measurement in addition to gammopathy assessment. At least one prevalent non-traumatic vertebral fracture was discovered in 18.4% patients and equally distributed between men and women. Fractured patients were older, had a lower bone density and had also more frequently a lambda light chain isotype. Compared with patients with κ light chain, the odds ratio of being fractured for patients with λ light chain was 4.32 (95% confidence interval 1.80-11.16; P=0.002). These results suggest a high prevalence of non-traumatic vertebral fractures in MGUS associated with lambda light chain isotype and not only explained by low bone density.

Osteoprotegerin is a significant prognostic factor for overall survival in patients with primary systemic amyloidosis independent of the Mayo staging

Bone metabolism has not been systematically studied in primary (AL) amyloidosis. Thus we prospectively evaluated bone remodeling indices in 102 patients with newly diagnosed AL amyloidosis, 35 healthy controls, 35 newly diagnosed myeloma and 40 monoclonal gammopathy of undetermined significance patients. Bone resorption markers (C-telopeptide of type-1 collagen, N-telopeptide of type-1 collagen) and osteoclast regulators (soluble receptor activator of nuclear factor-κB ligand (sRANKL), osteoprotegerin (OPG)) were increased in AL patients compared with controls (P<0.01), but bone formation was unaffected. Myeloma patients had increased bone resorption and decreased bone formation compared with AL patients, while sRANKL/OPG ratio was markedly decreased in AL, due to elevated OPG in AL (P<0.001). OPG correlated with N-terminal pro-brain natriuretic peptide (P<0.001) and was higher in patients with cardiac involvement (P=0.028) and advanced Mayo stage (P=0.001). OPG levels above the upper value of healthy controls was associated with shorter survival (34 versus 91 months; P=0.026), while AL patients with OPG levels in the top quartile had very short survival (12 versus 58 months; P=0.024). In Mayo stage 1 disease, OPG identified patients with poor survival (12 versus >60 months; P=0.012). We conclude that increased OPG in AL is not only a compensation to osteoclast activation but may also reflect early cardiac damage and may identify patients at increased risk of death within those with earlier Mayo stage.

Secondary osteoporosis: pathophysiology & diagnosis

Osteoporosis is a skeletal disease characterized by decreased bone mass and microarchitectural changes in bone tissue that increase the susceptibility to fracture. Secondary osteoporosis is loosely defined as low bone mineral density or increased risk of fragility fracture caused by any factor other than aging or postmenopausal status. The purpose of this review is to discuss the current understanding of the pathophysiology and contribution to fracture risk of many of the more common causes of secondary osteoporosis, as well as diagnostic considerations, outlined by organ system. While not comprehensive, included are a wide array of diseases, conditions, and medications that have been associated with bone loss and susceptibility to fractures. The hope is to highlight the importance to the general clinician of screening for and treating the osteoporosis in these patients, so to limit the resultant increased morbidity associated with fractures.

Dilemmas in treating smoldering multiple myeloma

Novel therapies hold promise for high-risk smoldering multiple myeloma (SMM). Recent studies suggest that modern combination approaches can be options for high-risk SMM to obtain deep molecular responses with favorable toxicity profiles. Although pioneering treatment trials based on small numbers of patients suggest progression-free and overall survival benefits, application of the data to real-life practice remains to be validated. Therapeutic modulation of disease tempo, disease burden, clonal evolution, and tumor microenvironment in SMM remains to be understood and calls for reliable biomarkers reflective of disease biology. Here, we review studies that open a new management platform for SMM, address ongoing dilemmas in practice and under investigation, and highlight emerging scientific questions in the era of SMM treatment.

The clinical relevance and management of monoclonal gammopathy of undetermined significance and related disorders: recommendations from the European Myeloma Network

Monoclonal gammopathy of undetermined significance is one of the most common pre-malignant disorders. IgG and IgA monoclonal gammopathy of undetermined significance are precursor conditions of multiple myeloma; light-chain monoclonal gammopathy of undetermined significance of light-chain multiple myeloma; and IgM monoclonal gammopathy of undetermined significance of Waldenström's macroglobulinemia and other lymphoproliferative disorders. Clonal burden, as determined by bone marrow plasma cell percentage or M-protein level, as well as biological characteristics, including heavy chain isotype and light chain production, are helpful in predicting risk of progression of monoclonal gammopathy of undetermined significance to symptomatic disease. Furthermore, alterations in the bone marrow microenvironment of monoclonal gammopathy of undetermined significance patients result in an increased risk of venous and arterial thrombosis, infections, osteoporosis, and bone fractures. In addition, the small clone may occasionally be responsible for severe organ damage through the production of a monoclonal protein that has autoantibody activity or deposits in tissues. These disorders are rare and often require therapy directed at eradication of the underlying plasma cell or lymphoplasmacytic clone. In this review, we provide an overview of the clinical relevance of monoclonal gammopathy of undetermined significance. We also give general recommendations of how to diagnose and manage patients with monoclonal gammopathy of undetermined significance.

Less strength and more fractures for MGUS bones

In this issue of Blood, Farr et al showed that patients with monoclonal gammopathy of undetermined significance (MGUS) have increased cortical bone porosity and reduced bone strength,1 conditions that can lead to the increased fracture risk, which has been reported in MGUS patients.

Smoldering multiple myeloma: present position and potential promises

Since smoldering multiple myeloma (SMM) was first described over three decades ago based on a case series of six patients, its definition and our understanding of the entity have evolved considerably. The risk of progression to symptomatic myeloma (MM) varies greatly among individuals diagnosed with myeloma precursor disease. Epidemiologic, molecular, flow cytometric and radiological techniques have demonstrated that this transformation to MM from precursor states is not sudden but rather a continuous overlapping series of events with evidence of end-organ damage that could manifest in the earliest stages of disease. Contemporary antimyeloma therapies can yield rapid, deep, and durable responses with manageable toxicities, and molecular-cell-based measures are now available to rule out minimal residual disease. With this information, clinical studies with correlative measures can now be developed to test the fundamental hypothesis that intervention in early myeloma may provide a measurable clinical benefit to patients by either delaying progression or eradicating plasma cell clones.

Monoclonal gammopathy of undetermined significance and smoldering multiple myeloma: a review of the current understanding of epidemiology, biology, risk stratification, and management of myeloma precursor disease

The term monoclonal gammopathy of undetermined significance (MGUS) was coined in 1978. The recent advances in our knowledge about MGUS and smoldering multiple myeloma (SMM) have helped us better understand the pathogenesis of myeloma. It seems that myeloma evolves from a precursor state in almost all cases. We do not completely understand the multistep process from the precursor state to myeloma, but studies like whole genome sequencing continue to improve our understanding of this process. The process of transformation may not be linear acquisition of changes, but rather a branched heterogeneous process. Clinical features that are prognostic of rapid transformation have been identified, but no specific molecular markers have been identified. Even with recent advances, multiple myeloma remains an incurable disease in the vast majority, and intervening at the precursor state provides a unique opportunity to alter the natural history of the disease. A limitation is that a vast majority of patients with precursor disease, especially low-risk MGUS, will never progress to myeloma in their lifetime, and treating these patients is not only unnecessary but may be potentially harmful. The challenge is to identify a subset of patients with the precursor state that would definitely progress to myeloma and in whom interventions will have a meaningful impact. As our understanding of the molecular and genetic processes improves, these studies will guide the selection of high-risk patients more appropriately and ultimately direct a tailored management strategy to either delay progression to symptomatic myeloma or even "cure" a person at this premalignant stage.

The role of osteoblast cells in the pathogenesis of unicameral bone cysts

PURPOSE

The pathogenesis of unicameral bone cysts (UBCs) remains largely unknown. Osteoclasts have been implicated, but the role of osteoblastic cells has, to date, not been explored. This study investigated the pathophysiology of UBCs by examining the interactions between the cyst fluid and human bone marrow stromal cells (hBMSCs) and the effect of the fluid on osteogenesis.

METHODS

Fluid was aspirated from two UBCs and analysed for protein, electrolyte and cytokine levels. Graded concentrations of the fluid were used as culture media for hBMSCs to determine the effects of the fluid on hBMSC proliferation and osteogenic differentiation. The fibrocellular lining was analysed histologically and by electron microscopy.

RESULTS

Alkaline phosphatase (ALP) staining of hBMSCs that were cultured in cyst fluid demonstrated increased cell proliferation and osteogenic differentiation compared to basal media controls. Biochemical analysis of these hBMSCs compared to basal controls confirmed a marked increase in DNA content (as a marker of proliferation) and ALP activity (as a marker of osteogenic differentiation) which was highly significant (p < 0.001). Osteoclasts were demonstrated in abundance in the cyst lining. The cyst fluid cytokine profile revealed levels of the pro-osteoclast cytokines IL-6, MIP-1α and MCP-1 that were 19×, 31× and 35× greater than those in reference serum.

CONCLUSIONS

Cyst fluid promoted osteoblastic growth and differentiation. Despite appearing paradoxical that the cyst fluid promoted osteogenesis, osteoblastic cells are required for osteoclastogenesis through RANKL signalling. Three key cytokines in this pathway (IL-6, MIP-1α, MCP-1) were highly elevated in cyst fluid. These findings may hold the key to the pathogenesis of UBCs, with implications for treatment methods.

Elevated circulating sclerostin correlates with advanced disease features and abnormal bone remodeling in symptomatic myeloma: reduction post-bortezomib monotherapy

Sclerostin is a Wingless and Int-1 inhibitor, which is produced by osteocytes and inhibits osteoblast-driven bone formation. Sclerostin is implicated in the pathogenesis of bone loss in metabolic bone disorders but there is no information for its effect on multiple myeloma (MM)-related osteolytic disease. We evaluated circulating sclerostin in 157 newly diagnosed patients with symptomatic myeloma, in 25 with relapsed myeloma who received bortezomib monotherapy, in 21 patients with monoclonal gammopathy of undetermined significance (MGUS), and in 21 healthy controls. Patients with active myeloma had elevated circulating sclerostin compared to MGUS patients and controls (p < 0.01). MM patients who presented with fractures at diagnosis (n = 34) had very high levels of circulating sclerostin compared with all others (p < 0.01), whereas sclerostin correlated negatively with bone specific alkaline phosphatase (a bone formation marker; r = -0.541, p < 0.0001) and positively with C-telopeptide of collagen type-1 (a bone resorption marker; r = 0.524, p < 0.0001). Patients with International Staging System (ISS)-3 disease had higher circulating sclerostin compared to ISS-1 and ISS-2 MM (p = 0.001). Furthermore, patients with high sclerostin (upper quartile, n = 40) had a median survival of 27 months versus 98 months of all others (p = 0.031). Relapsed MM patients had higher levels of circulating sclerostin even compared to newly diagnosed patients (p < 0.01). Bortezomib monotherapy resulted in a reduction of sclerostin by almost 50% in both responders and non-responders. These results suggest that patients with active myeloma have elevated circulating sclerostin, which correlated with advanced disease features including severe bone disease. Our study indicates sclerostin as a possible target for the development of novel therapies to enhance osteoblast function in myeloma.

Computational modeling of interactions between multiple myeloma and the bone microenvironment

Multiple Myeloma (MM) is a B-cell malignancy that is characterized by osteolytic bone lesions. It has been postulated that positive feedback loops in the interactions between MM cells and the bone microenvironment form reinforcing ‘vicious cycles’, resulting in more bone resorption and MM cell population growth in the bone microenvironment. Despite many identified MM-bone interactions, the combined effect of these interactions and their relative importance are unknown. In this paper, we develop a computational model of MM-bone interactions and clarify whether the intercellular signaling mechanisms implemented in this model appropriately drive MM disease progression. This new computational model is based on the previous bone remodeling model of Pivonka et al. [1], and explicitly considers IL-6 and MM-BMSC (bone marrow stromal cell) adhesion related pathways, leading to formation of two positive feedback cycles in this model. The progression of MM disease is simulated numerically, from normal bone physiology to a well established MM disease state. Our simulations are consistent with known behaviors and data reported for both normal bone physiology and for MM disease. The model results suggest that the two positive feedback cycles identified for this model are sufficient to jointly drive the MM disease progression. Furthermore, quantitative analysis performed on the two positive feedback cycles clarifies the relative importance of the two positive feedback cycles, and identifies the dominant processes that govern the behavior of the two positive feedback cycles. Using our proposed quantitative criteria, we identify which of the positive feedback cycles in this model may be considered to be ‘vicious cycles’. Finally, key points at which to block the positive feedback cycles in MM-bone interactions are identified, suggesting potential drug targets.

Bone microstructural changes revealed by high-resolution peripheral quantitative computed tomography imaging and elevated DKK1 and MIP-1α levels in patients with MGUS

Recent population-based studies demonstrate an increased fracture risk with monoclonal gammopathy of undetermined significance (MGUS). The etiology of this increased risk remains unclear, however, because areal bone mineral density (aBMD) measurements by dual-energy x-ray absorptiometry cannot assess bone microstructural properties critical to determining bone quality and strength. To better define the skeletal effects of MGUS, we performed aBMD and high-resolution peripheral quantitative computed tomography volumetric bone mineral density (vBMD) measurements in 50 MGUS patients (20 females, 30 males; mean ± SEM age, 70.5 ± 1.4 years) and 100 matched control subjects. Relative to controls, MGUS patients had decreased aBMD at the femoral neck (P = .05) and total femur (P < .05) but no differences at other sites. In contrast, high-resolution peripheral quantitative computed tomography showed markedly diminished cortical thickness (P < .05) and increased endocortical area (P < .01). Average vBMD (P < .01), cortical vBMD (P < .001), and trabecular thickness (P < .01) were all significantly decreased in MGUS patients, suggestive of impaired bone formation. Serum levels of the Wnt pathway inhibitor Dickkopf-related protein 1 (P < .001) and osteoclast-activating factor MIP-1α (P < .05) also were significantly elevated in MGUS patients. Our data provide the first evidence of altered bone microstructure in MGUS and suggest that cytokines elevated in osteolytic myeloma also may be associated with bone loss in MGUS.

Myelomagenesis: capturing early microenvironment changes

Plasma cell neoplasms result from the clonal expansion of terminally differentiated, immunoglobulin heavy-chain class switched B cells that typically secrete a monoclonal immunoglobulin. The 2008 World Health Organization (WHO) classification of plasma cell neoplasms encompasses a broad spectrum of disorders, from the precursor disorder monoclonal gammopathy of undetermined significance (MGUS) to plasma cell leukemia. The classification includes, in addition to precursor lesion MGUS, plasma cell myeloma, plasmacytoma, immunoglobulin deposition diseases, and osteosclerotic myeloma. Plasma cell myeloma is further divided into symptomatic plasma cell myeloma or multiple myeloma (MM), asymptomatic smoldering myeloma (SMM), non-secretory myeloma, and plasma cell leukemia. Although histopathologic cut-off criteria are incorporated into the classification schema, distinction between MGUS, SMM, and MM depends primarily on the presence or absence of end-organ damage, as defined by "CRAB" criteria (hypercalcemia, renal insufficiency, anemia, lytic bone lesions, or a combination of these). Systematic evaluation of pathogenetic differences between MGUS and MM should offer invaluable insights into early myelomagenesis. Given the complex, intertwined nature of the malignant plasma cell and its surroundings, multiple pathogenetic mechanisms play a critical role in interactions between neoplastic cells and their microenvironment. Understanding the events leading to end-organ damage, like anemia and bone remodeling, is a critical part of investigating early myelomagenesis and should provide us with better tools for early identification and treatment of these patients.

Bone disease in multiple myeloma and precursor disease: novel diagnostic approaches and implications on clinical management

The manifestations of bone involvement in patients with multiple myeloma (MM) can have devastating clinical effects and increase mortality. Recent studies demonstrate that patients with the precursor conditions smoldering MM (SMM) and monoclonal gammopathy of undetermined significance (MGUS) show evidence of bone disease and increased risk of fractures. The understanding of the pathogenesis of bone disease in MM has expanded in recent years. The traditional skeletal survey will probably be replaced by newer and more sensitive imaging techniques, which may have a prognostic impact and change our definition of MGUS and SMM. Bisphosphonates are recommended to prevent skeletal events in patients with MM, and have also been studied in SMM and MGUS. This article summarizes the current knowledge of bone disease in plasma cell disorders, and discusses the current standard and future role of novel imaging techniques, as well as the evidence and current guidelines for bisphosphonates in MM, SMM and MGUS.

CCR1 as a target for multiple myeloma

INTRODUCTION

By directing cell trafficking, differentiation and growth, chemokines modulate the immune response and are involved in the pathogenesis of autoimmune diseases and cancers, including multiple myeloma (MM). MM, the second most common hematological malignancy in the US, is characterized by disordered plasma cell growth within the bone marrow microenvironment. CCL3 and its receptors, CCR1 in particular, play a central role in the pathogenesis of MM and MM-induced osteolytic bone disease.

AREAS COVERED

This review describes the functional role of CCR1 in MM and the preclinical results observed with CCR1 antagonists. CCL3 and CCR1 stimulate tumor growth, both directly and indirectly, via upregulation of cell adhesion and cytokine secretion. In addition, they modulate the osteoclast/osteoblast balance, by inducing osteoclast differentiation and inhibiting osteoblast function. Targeting either ligand or receptor reverses these effects, leading to in vivo tumor burden control and prevention of osteolysis, as confirmed in both murine and humanized mouse models.

EXPERT OPINION

These promising data set the stage for clinical trials to assess the effects of CCR1 inhibitors in MM. The success of these studies depends on the development of novel antagonists with improved chemical/physical properties and careful selection of the patient population who may benefit the most from these agents.

A retrospective study to evaluate the work-up and follow-up of patients with monoclonal gammopathy of undetermined significance

BACKGROUND

Monoclonal gammopathy of undetermined significance (MGUS) is a plasma cell proliferative disorder that transforms into multiple myeloma and other serious B-cell disorders at an approximate rate of 1% per year; these patients are also at increased risk for fractures.

PATIENTS AND METHODS

We conducted a retrospective, multicenter study of 100 patients from seven community health clinics to gain a better understanding of the work-up, follow-up, and treatment of these patients.

RESULTS

MGUS patients appear to undergo inadequate work-up, follow-up, and treatment in the community setting.

CONCLUSIONS

Physicians should adhere to recently established guidelines to ensure that MGUS patients receive optimal care for this condition.

Pathogenesis and management of myeloma bone disease

Osteolytic bone disease is a frequent complication of multiple myeloma, resulting in skeletal complications that are a significant cause of morbidity and mortality. It is the result of increased activity of osteoclasts that is not followed by reactive bone formation by osteoblasts. Recent studies have revealed novel molecules and pathways that are implicated in osteoclast activation and osteoblast inhibition, including the RANKL/osteoprotegerin pathway, macrophage inflammatory proteins and the wingless type signaling pathway. These molecules also appear to interfere with tumor growth and survival, providing possible targets for the development of novel drugs for the management of lytic disease in myeloma. Currently, bisphosphonates are the mainstay of treatment for myeloma bone disease, although several novel agents appear promising. This review focuses on recent advances in understanding the biology of bone disease in multiple myeloma, diagnosis and recent progress in treatment options.

Advances in understanding monoclonal gammopathy of undetermined significance as a precursor of multiple myeloma

Monoclonal gammopathy of undetermined significance (MGUS) affects at least 3% of the population above the age of 50 and is the precursor to multiple myeloma (MM), an incurable malignancy of plasma cells. Recent advances in MGUS include: an improved understanding of the pathogenesis of MGUS and its progression to MM, involving molecular events intrinsic to the malignant plasma cell as well as the microenvironment; novel techniques to assess risk for progression to MM using serum-free light-chain analysis and immunophenotyping; and a renewed interest in chemoprevention of MM. In the future, continued improvement in our understanding of MGUS will lead to the development of better biomarkers for prognosis and therapies for chemoprevention of MM.

From myeloma precursor disease to multiple myeloma: new diagnostic concepts and opportunities for early intervention

Since monoclonal gammopathy of undetermined significance (MGUS) was first described more than 30 years ago, the definition of the entity has evolved. Today, 3 distinct clinical MGUS subtypes have been defined: non-immunoglobulin M (IgM; IgG or IgA) MGUS, IgM MGUS, and light chain MGUS. Each clinical MGUS subtype is characterized by unique intermediate stages and progression events. Although we now have strong evidence that multiple myeloma is consistently preceded by a precursor state at the molecular level, there is urgent need to better understand mechanisms that regulate transformation from precursor to full-blown multiple myeloma. In the future, if such knowledge was available, it would allow clinicians to define high-risk and low-risk precursor patients for a more tailored clinical management. Also, it would provide insights on the individual patient's disease biology, which, in turn, can be used for targeted and more individualized treatment strategies. On the basis of current clinical guidelines, patients diagnosed with MGUS and smoldering myeloma should not be treated outside of clinical trials. In the near future, it seems reasonable to believe that high-risk precursor patients will likely become candidates for early treatment strategies. In this review, we discuss novel insights from recent studies and propose future directions of relevance for clinical management and research studies.