Pathogenesis of myeloma bone disease

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.

Immunomodulatory drugs lenalidomide and pomalidomide inhibit multiple myeloma-induced osteoclast formation and the RANKL/OPG ratio in the myeloma microenvironment targeting the expression of adhesion molecules

Multiple myeloma (MM)-induced osteoclast (OC) formation is mainly due to an imbalance of the receptor activator NF-κB ligand (RANKL)-osteoprotegerin (OPG) ratio in favor of RANKL in the bone microenvironment and to the CCL3 production by MM cells. The purpose of the study was to investigate the effect of the immunomodulatory drugs on RANKL/OPG ratio, the production of pro-osteoclastogenic cytokines, and MM-induced OC formation. We found that in vivo concentrations of both lenalidomide (LEN) and pomalidomide (POM) significantly blunted RANKL upregulation normalizing the RANKL/OPG ratio in human osteoprogenitor cells (PreOBs) when co-cultured with MM cells and also inhibited CCL3 production by MM cells. A reduction in CD49d expression, a molecule critically involved in RANKL upregulation in the MM microenvironment, accompanied this effect. Consistently, the pro-osteoclastogenic property of MM cells co-cultured with PreOBs was reduced by both LEN and POM. We further investigated the effect of these drugs on the transcriptional profile of both MM cells and PreOBs by microarray analysis, which showed that adhesion molecules, such as ITGA8 and ICAM2, are significantly downregulated in MM cells. Our data suggest that LEN and POM inhibit MM-induced OC formation through normalization of the RANKL/OPG ratio targeting the expression of adhesion molecules by MM cells.

RANKL expression, function, and therapeutic targeting in multiple myeloma and chronic lymphocytic leukemia

Bone destruction is a prominent feature of multiple myeloma, but conflicting data exist on the expression and pathophysiologic involvement of the bone remodeling ligand RANKL in this disease and the potential therapeutic benefits of its targeted inhibition. Here, we show that RANKL is expressed by primary multiple myeloma and chronic lymphocytic leukemia (CLL) cells, whereas release of soluble RANKL was observed exclusively with multiple myeloma cells and was strongly influenced by posttranscriptional/posttranslational regulation. Signaling via RANKL into multiple myeloma and CLL cells induced release of cytokines involved in disease pathophysiology. Both the effects of RANKL on osteoclastogenesis and cytokine production by malignant cells could be blocked by disruption of RANK-RANKL interaction with denosumab. As we aimed to combine neutralization of RANKL with induction of antibody-dependent cellular cytotoxicity of natural killer (NK) cells against RANKL-expressing malignant cells and as denosumab does not stimulate NK reactivity, we generated RANK-Fc fusion proteins with modified Fc moieties. The latter displayed similar capacity compared with denosumab to neutralize the effects of RANKL on osteoclastogenesis in vitro, but also potently stimulated NK cell reactivity against primary RANKL-expressing malignant B cells, which was dependent on their engineered affinity to CD16. Our findings introduce Fc-optimized RANK-Ig fusion proteins as attractive tools to neutralize the detrimental function of RANKL while at the same time potently stimulating NK cell antitumor immunity.

p38 MAPK in myeloma cells regulates osteoclast and osteoblast activity and induces bone destruction

p38 mitogen-activated protein kinase (MAPK), which is constitutively activated in human myeloma, has been implicated in bone destruction by this cancer, but the processes it recruits are obscure. In this study, we show that p38 activity in myeloma inhibits osteoblast differentiation and bone formation, but also enhances osteoclast maturation and bone resorption. p38 regulated the expression and secretion of the Wnt pathway antagonist DKK-1 and the monocyte chemoattractant MCP-1. Attenuating p38, DKK-1, or MCP-1 were each sufficient to reduce bone lesions in vivo. Although it is well known that DKK-1 inhibits osteoblast differentiation, we found that together with MCP-1, it could also promote osteoclast differentiation and bone resorption. The latter effects were mediated by enhancing expression of RANK in osteoclast progenitor cells and by upregulating secretion of its ligand RANKL from stromal cells and mature osteoblasts. In summary, our study defined the mechanisms by which p38 signaling in myeloma cells regulates osteoblastogenesis, osteoclastogenesis, and bone destruction. Our findings, which may have implications for bone invasion by other cancers where p38 is elevated, strongly suggests that targeting p38 for inhibition may offer an effective therapeutic approach to treat osteolytic bone lesions in patients with myeloma.

Bone marrow microenvironment in multiple myeloma progression

Substantial advances have been made in understanding the biology of multiple myeloma (MM) through the study of the bone marrow (BM) microenvironment. Indeed, the BM niche appears to play an important role in differentiation, migration, proliferation, survival, and drug resistance of the malignant plasma cells. The BM niche is composed of a cellular compartment (stromal cells, osteoblasts, osteoclasts, endothelial cells, and immune cells) and a noncellular compartment including the extracellular matrix (ECM) and the liquid milieu (cytokines, growth factors, and chemokines). In this paper we discuss how the interaction between the malignant plasma cell and the BM microenvironment allowed myeloma progression through cell homing and the new concept of premetastatic niche.

In silico investigations of the anti-catabolic effects of pamidronate and denosumab on multiple myeloma-induced bone disease

It is unclear whether the new anti-catabolic agent denosumab represents a viable alternative to the widely used anti-catabolic agent pamidronate in the treatment of Multiple Myeloma (MM)-induced bone disease. This lack of clarity primarily stems from the lack of sufficient clinical investigations, which are costly and time consuming. However, in silico investigations require less time and expense, suggesting that they may be a useful complement to traditional clinical investigations. In this paper, we aim to (i) develop integrated computational models that are suitable for investigating the effects of pamidronate and denosumab on MM-induced bone disease and (ii) evaluate the responses to pamidronate and denosumab treatments using these integrated models. To achieve these goals, pharmacokinetic models of pamidronate and denosumab are first developed and then calibrated and validated using different clinical datasets. Next, the integrated computational models are developed by incorporating the simulated transient concentrations of pamidronate and denosumab and simulations of their actions on the MM-bone compartment into the previously proposed MM-bone model. These integrated models are further calibrated and validated by different clinical datasets so that they are suitable to be applied to investigate the responses to the pamidronate and denosumab treatments. Finally, these responses are evaluated by quantifying the bone volume, bone turnover, and MM-cell density. This evaluation identifies four denosumab regimes that potentially produce an overall improved bone-related response compared with the recommended pamidronate regime. This in silico investigation supports the idea that denosumab represents an appropriate alternative to pamidronate in the treatment of MM-induced bone disease.

Detection of Skeletal Lesions by Whole Body Multidetector Computed Tomography in Multiple Myeloma has no Impact on Long-Term Outcomes Post Autologous Hematopoietic Cell Transplantation

BACKGROUND

Multiple myeloma (MM), a plasma cell malignancy, is the most common cancer to involve the skeleton. Skeletal related events such as pathologic fractures and lytic bone lesions have been associated with poor prognosis. Whole body multidetector computed tomography (WBCT) has been shown to be the most sensitive imaging modality in detecting small osteolytic lesions (< 5 mm) in the spine. The significance of lytic lesions detected only by CT is unknown as is their impact on overall survival of MM. The aim of this study was to evaluate the impact of lytic bone lesions seen only by WBCT on progression free survival (PFS) and overall survival (OS) in MM patients after hematopoietic cell transplantation (HCT).

METHODS

We evaluated 72 patients who had WBCT and conventional radiographic skeletal survey (CSS) after initial or salvage chemotherapy prior to HCT.

RESULTS

Forty-one patients (57%) had more findings on WBCT than CSS, 31 patients (43%) had no differences in the two imaging techniques, 9 patients had no bone lesions on either modality, and 5 patients had lesions only identified by WBCT and not on CSS. PFS and OS were similar in patients with lesions seen by CSS irrespective of whether additional lesions were noted by WBCT; similarly, in patients without lesions on CSS, OS and PFS were better than patients with lytic lesions, but detection of occult lesions by WBCT did not adversely affect PFS or OS.

CONCLUSIONS

Our study shows that although WBCT is more sensitive in defining existing myelomatous bony disease in MM, these additional findings may not have any impact on PFS and OS of MM patients. Only patients without any bone lesions on conventional skeletal survey had significantly better PFS and OS. This suggests CSS remains the gold standard for evaluating myeloma bone disease.

Dual inhibition of canonical and noncanonical NF-κB pathways demonstrates significant antitumor activities in multiple myeloma

PURPOSE

NF-κB transcription factor plays a key role in the pathogenesis of multiple myeloma in the context of the bone marrow microenvironment. Both canonical and noncanonical pathways contribute to total NF-κB activity. Recent studies have shown a critical role for the noncanonical pathway: selective inhibitors of the canonical pathway present a limited activity, mutations of the noncanonical pathway are frequent, and bortezomib-induced cytotoxicity cannot be fully attributed to inhibition of canonical NF-κB activity.

EXPERIMENTAL DESIGN

Multiple myeloma cell lines, primary patient cells, and the human multiple myeloma xenograft murine model were used to examine the biologic impact of dual inhibition of both canonical and noncanonical NF-κB pathways.

RESULTS

We show that PBS-1086 induces potent cytotoxicity in multiple myeloma cells but not in peripheral blood mononuclear cells. PBS-1086 overcomes the proliferative and antiapoptotic effects of the bone marrow milieu, associated with inhibition of NF-κB activity. Moreover, PBS-1086 strongly enhances the cytotoxicity of bortezomib in bortezomib-resistant multiple myeloma cell lines and patient multiple myeloma cells. PBS-1086 also inhibits osteoclastogenesis through an inhibition of RANK ligand (RANKL)-induced NF-κB activation. Finally, in a xenograft model of human multiple myeloma in the bone marrow milieu, PBS-1086 shows significant in vivo anti-multiple myeloma activity and prolongs host survival, associated with apoptosis and inhibition of both NF-κB pathways in tumor cells.

CONCLUSIONS

Our data show that PBS-1086 is a promising dual inhibitor of the canonical and noncanonical NF-κB pathways. Our preclinical study therefore provides the framework for clinical evaluation of PBS-1086 in combination with bortezomib for the treatment of multiple myeloma and related bone lesions.

Abdominal manifestations of extraosseous myeloma: cross-sectional imaging spectrum

Extraosseous myeloma, defined as the myelomatous involvement outside the skeleton system, is rare and often associated with advanced multiple myeloma. There has been a recent increase in the clinicoradiological incidence of this entity, possibly secondary to increased survival of patients and frequent use of imaging. This has led to the development of new clinical staging guidelines for multiple myeloma, which include the use of imaging modalities positron emission tomography/computed tomography and magnetic resonance imaging for accurate detection and optimal management. The aims of this review were to discuss the significance of identification of extraosseous disease, to describe the spectrum and common sites of extraosseous involvement in the abdomen, and to review the imaging findings of extraosseous myeloma in the abdomen.

Dasatinib as a bone-modifying agent: anabolic and anti-resorptive effects

BACKGROUND

Bone loss, in malignant or non-malignant diseases, is caused by increased osteoclast resorption and/or reduced osteoblast bone formation, and is commonly associated with skeletal complications. Thus, there is a need to identify new agents capable of influencing bone remodeling. We aimed to further pre-clinically evaluate the effects of dasatinib (BMS-354825), a multitargeted tyrosine kinase inhibitor, on osteoblast and osteoclast differentiation and function.

METHODS

For studies on osteoblasts, primary human bone marrow mensenchymal stem cells (hMSCs) together with the hMSC-TERT and the MG-63 cell lines were employed. Osteoclasts were generated from peripheral blood mononuclear cells (PBMC) of healthy volunteers. Skeletally-immature CD1 mice were used in the in vivo model.

RESULTS

Dasatinib inhibited the platelet derived growth factor receptor-β (PDGFR-β), c-Src and c-Kit phosphorylation in hMSC-TERT and MG-63 cell lines, which was associated with decreased cell proliferation and activation of canonical Wnt signaling. Treatment of MSCs from healthy donors, but also from multiple myeloma patients with low doses of dasatinib (2-5 nM), promoted its osteogenic differentiation and matrix mineralization. The bone anabolic effect of dasatinib was also observed in vivo by targeting endogenous osteoprogenitors, as assessed by elevated serum levels of bone formation markers, and increased trabecular microarchitecture and number of osteoblast-like cells. By in vitro exposure of hemopoietic progenitors to a similar range of dasatinib concentrations (1-2 nM), novel biological sequelae relative to inhibition of osteoclast formation and resorptive function were identified, including F-actin ring disruption, reduced levels of c-Fos and of nuclear factor of activated T cells 1 (NFATc1) in the nucleus, together with lowered cathepsin K, αVβ3 integrin and CCR1 expression.

CONCLUSIONS

Low dasatinib concentrations show convergent bone anabolic and reduced bone resorption effects, which suggests its potential use for the treatment of bone diseases such as osteoporosis, osteolytic bone metastasis and myeloma bone disease.

Bisphosphonate therapy in multiple myeloma in preventing vertebral collapses: preliminary report

PURPOSE

The aim of the study was to report and discuss the preliminary data obtained in a homogeneous series of 50 patients affected by multiple myeloma treated with bisphosphonates.

METHODS

Patients were followed for a minimum of 1 year. Main orthopaedic data were recorded. Visual Analogue Score and QLQ-C30 and MY 20 were used to assess the quality of life.

RESULTS

Statistical analysis showed less lytic lesions in the group with zoledronate therapy and stable primary disease compared with a greater number of lesions in the non-treated group. Results regarding VAS score and QLQ-C30 and MY were statistically better in the first group than in the second.

CONCLUSIONS

Our results confirm the efficacy of zoledronate in ensuring an acceptable quality of life restraining the aggressiveness of the myeloma on bone tissue, especially in spine although further prospective studies have to be conducted to determine its correct use in myeloma patients.

Constitutive activation of p38 MAPK in tumor cells contributes to osteolytic bone lesions in multiple myeloma

Bone destruction is a hallmark of multiple myeloma and affects more than 80% of patients. However, current therapy is unable to completely cure and/or prevent bone lesions. Although it is accepted that myeloma cells mediate bone destruction by inhibition of osteoblasts and activation of osteoclasts, the underlying mechanism is still poorly understood. This study demonstrates that constitutive activation of p38 mitogen-activated protein kinase in myeloma cells is responsible for myeloma-induced osteolysis. Our results show that p38 is constitutively activated in most myeloma cell lines and primary myeloma cells from patients. Myeloma cells with high/detectable p38 activity, but not those with low/undetectable p38 activity, injected into SCID or SCID-hu mice caused bone destruction. Inhibition or knockdown of p38 in human myeloma reduced or prevented myeloma-induced osteolytic bone lesions without affecting tumor growth, survival, or homing to bone. Mechanistic studies showed that myeloma cell p38 activity inhibited osteoblastogenesis and bone formation and activated osteoclastogenesis and bone resorption in myeloma-bearing SCID mice. This study elucidates a novel molecular mechanism—sactivation of p38 signaling in myeloma cells—by which myeloma cells induce osteolytic bone lesions and indicates that targeting myeloma cell p38 may be a viable approach to treating or preventing myeloma bone disease.

Novel therapies in benign and malignant bone diseases

With an ageing population and improving cancer therapies, the two most common benign and malignant bone diseases, osteoporosis and bone metastases, will continue to affect an increasing number of patients. Our expanding knowledge of the molecular processes underlying these conditions has resulted in novel bone targets that are currently being explored in clinical trials. Clearly, the approval of denosumab, a monoclonal antibody directed against RANKL, has just marked the beginning of a new era for bone therapy with several additional new therapies lining up for clinical approval in the coming years. Potential agents targeting the osteoclast include cathepsin K, currently in phase 3 trials, and src inhibitors. Amongst anabolic agents, inhibitors of the Wnt-inhibitor sclerostin and dickkopf-1 are promising in clinical trials. Here, we will provide a comprehensive overview of the most promising agents currently explored for the treatment of bone diseases.

Challenging the current approaches to multiple myeloma- and other cancer-related bone diseases: from bisphosphonates to targeted therapy

An international myeloma meeting entitled "Challenging the current approaches to multiple myeloma- and other cancer-related bone diseases: from bisphosphonates to targeted therapy" was held in Freiburg, Germany in July 2011 to discuss novel insights into and approaches to myeloma bone disease and other bone-seeking tumors. This review briefly summarizes the most prominent data of the meeting and current literature on our understanding of bone disease, the role of imaging techniques, operative interventions and systemic bone-seeking treatment, all of which should further improve our future therapeutic choices.

Increased osteocyte death in multiple myeloma patients: role in myeloma-induced osteoclast formation

The involvement of osteocytes in multiple myeloma (MM)-induced osteoclast (OCL) formation and bone lesions is still unknown. Osteocytes regulate bone remodelling at least partially, as a result of their cell death triggering OCL recruitment. In this study, we found that the number of viable osteocytes was significantly smaller in MM patients than in healthy controls, and negatively correlated with the number of OCLs. Moreover, the MM patients with bone lesions had a significantly smaller number of viable osteocytes than those without, partly because of increased apoptosis. These findings were further confirmed by ultrastructural in vitro analyses of human preosteocyte cells cocultured with MM cells, which showed that MM cells increased preosteocyte death and apoptosis. A micro-array analysis showed that MM cells affect the transcriptional profiles of preosteocytes by upregulating the production of osteoclastogenic cytokines such as interleukin (IL)-11, and increasing their pro-osteoclastogenic properties. Finally, the osteocyte expression of IL-11 was higher in the MM patients with than in those without bone lesions. Our data suggest that MM patients are characterized by a reduced number of viable osteocytes related to the presence of bone lesions, and that this is involved in MM-induced OCL formation.

Multiple myeloma: 2012 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Multiple myeloma accounts for ∼10% of all hematologic malignancies.

DIAGNOSIS

The diagnosis requires 10% or more clonal plasma cells on bone marrow examination or a biopsy proven plasmacytoma plus evidence of end-organ damage felt to be related to the underlying plasma-cell disorder.

RISK STRATIFICATION

Patients with 17p deletion, t(14;16), t(14;20), or high-risk gene expression profiling signature have high-risk myeloma. Patients with t(4;14) translocation, karyotypic deletion 13, or hypodiploidy are considered to have intermediate-risk disease. All others are considered to have standard-risk myeloma.

RISK-ADAPTED THERAPY

Standard-risk patients are treated with nonalkylator-based therapy such as lenalidomide plus low-dose dexamethasone (Rd) followed by autologous stem-cell transplantation (ASCT). An alternative strategy is to continue initial therapy after stem-cell collection, reserving ASCT for first relapse. Intermediate-risk and high-risk patients are treated with a bortezomib-based induction followed by ASCT and then bortezomib-based maintenance. Patients not eligible for ASCT can be treated with Rd for standard risk disease, or with a bortezomib-based regimen if intermediate-risk or high-risk features are present. To reduce toxicity, when using bortezomib, the once-weekly subcutaneous dose is preferred; similarly, when using dexamethasone, the low-dose approach (40 mg once a week) is preferred, unless there is a need for rapid disease control.

MANAGEMENT OF REFRACTORY DISEASE

Patients with indolent relapse can be treated first with two-drug or three-drug combinations. Patients with more aggressive relapse often require therapy with a combination of multiple active agents. The most promising new agents in development are pomalidomide and carfilizomib.

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.

Novel insights into the role of interleukin-27 and interleukin-23 in human malignant and normal plasma cells

Multiple myeloma is a monoclonal postgerminal center tumor that has phenotypic features of plasmablasts and/or plasma cells and usually localizes at multiple sites in the bone marrow. The pathogenesis of multiple myeloma is complex and dependent on the interactions between tumor cells and their microenvironment. Different cytokines, chemokines, and proangiogenic factors released in the tumor microenvironment are known to promote multiple myeloma cell growth. Here, we report recent advances on the role of 2 strictly related immunomodulatory cytokines, interleukin-27 (IL-27) and IL-23, in human normal and neoplastic plasma cells, highlighting their ability to (i) act directly against multiple myeloma cells, (ii) influence the multiple myeloma microenvironment by targeting osteoclast and osteoblast cells, and (iii) modulate normal plasma cell function. Finally, the therapeutic implication of these studies is discussed.

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.

Brain-derived neurotrophic factor is a potential osteoclast stimulating factor in multiple myeloma

Multiple myeloma (MM) is characterized by accumulation of monoclonal plasma cells in the bone marrow and progression of lytic bone lesions. The mechanisms of enhanced bone resorption in patients with myeloma are not fully defined. We have previously identified the role of brain-derived neurotrophic factor (BDNF) in proliferation and migration of MM cells. In our study, we investigated whether BDNF was possibly involved in MM cell-induced osteolysis. We showed that BDNF was elevated in MM patients and the bone marrow plasma levels of BDNF positively correlated with extent of bone disease. In osteoclast formation assay, bone marrow plasma from patients with MM increased osteoclast formation and the effect was significantly blocked by neutralizing antibody to BDNF, suggesting a critical role for BDNF in osteoclast activation. Furthermore, the direct effects of recombinant BDNF on osteoclast formation and bone resorption support the potential role of BDNF in the MM bone disease. BDNF receptor TrkB was expressed by human osteoclast precursors and a Trk inhibitor K252a markedly inhibited osteoclast formation stimulated with BDNF, demonstrating that BDNF used TrkB for its effects on osteoclast. Finally, bone marrow plasma BDNF level positively correlated with macrophage inflammatory protein-1α and receptor activator of nuclear factor-κB ligand, two major osteoclast stimulatory factors in MM. These results support an important role for BDNF in the development of myeloma bone disease.

Pain in malignant hematology

Pain is frequently experienced by patients with hematological malignancies, although it often receives little attention. Different underlying causes and mechanisms may sustain several pain syndromes in hematological malignant patients. Pain may be due to disease itself, to disease-related complications, to iatrogenic causes or may be associated with unrelated medical conditions. The management of pain in this setting requires a multidisciplinary approach, integrating analgesics and causal interventions. An accurate diagnostic assessment and the identification of the underlying causes and pathogenetic mechanisms may dictate the treatment approach. For most pain patients, the WHO's three-step analgesic scale for cancer pain relief can provide adequate relief with oral options, although difficult-to-treat pain syndromes, requiring a more complex treatment approach, may also be observed.

The role of bisphosphonates in multiple myeloma: mechanisms, side effects, and the future

Zoledronic acid and pamidronate are two potent anticatabolic nitrogen-containing bisphosphonates (BPs) used extensively in diseases with high bone turnover such as multiple myeloma (MM). In this review we focus on their biology and their current and future use in MM, and highlight some of the most common and emerging side effects. Although the primary target cells for BPs are osteoclasts, new insights suggest other cell types of the bone microenvironment as possible targets, including osteoblasts, endothelial cells, immune cells, and cancer cells. Here, we focus on the current guidelines for the use of BPs in MM and address side effects such as renal toxicity, osteonecrosis of the jaw, and low-energy fractures. Finally, we approach the future of BP use in MM in the context of other bone-targeted agents, evaluating ongoing clinical trials addressing alternate dosing and schedules of BP administration in MM patients.

Fewer bone disease events, improvement in bone remodeling, and evidence of bone healing with bortezomib plus melphalan-prednisone vs. melphalan-prednisone in the phase III VISTA trial in multiple myeloma

OBJECTIVES

  Bone disease is a key presenting feature of myeloma. This post hoc analysis of the phase III VISTA trial of bortezomib plus melphalan-prednisone (VMP) vs. MP in previously untreated myeloma patients assessed clinical bone disease events and changes in alkaline phosphatase (ALP), a marker for osteoblast activation, and serum Dickkopf-1 (DKK-1), an inhibitor of osteoblast differentiation, during treatment.

METHODS

  Patients received nine 6-wk cycles of VMP (bortezomib 1.3 mg/m(2) , days 1, 4, 8, 11, 22, 25, 29, 32, cycles 1-4, days 1, 8, 22, 29, cycles 5-9, plus melphalan 9mg/m(2) and prednisone 60mg/m(2) , days 1-4, cycles 1-9; N=344) or MP alone (N=338).

RESULTS

  Rates of bisphosphonates use during treatment (73% vs. 82%), progression because of worsening bone disease (3% vs. 11%), and requirement for subsequent radiotherapy (3% vs. 8%) were lower with VMP vs. MP. Median maximum ALP increase was significantly higher with VMP vs. MP overall (49.7% vs. 30.3%, P=0.029), and higher by response group (complete response [CR]: 68.7% vs. 43.9%; partial response [PR]: 41.5% vs. 31.2%). Greater maximum ALP increase was strongly associated with achievement of CR (P≤0.0001) and CR/PR (P≤0.01). Median DKK-1 decreased with VMP by 694.4pg/mL and increased with MP by 1273.3pg/mL from baseline to day 4 (P=0.0069). Available radiologic data revealed evidence of bone healing in 6/11 VMP-treated patients, who achieved best responses of three CR, one PR, and two stable disease.

CONCLUSIONS

  These results suggest a positive effect of bortezomib on bone metabolism and potentially bone healing in myeloma.

The histone deacetylase inhibitor, vorinostat, reduces tumor growth at the metastatic bone site and associated osteolysis, but promotes normal bone loss

Vorinostat, an oral histone deacetylase inhibitor with antitumor activity, is in clinical trials for hematologic and solid tumors that metastasize and compromise bone structure. Consequently, there is a requirement to establish the effects of vorinostat on tumor growth within bone. Breast (MDA-231) and prostate (PC3) cancer cells were injected into tibias of SCID/NCr mice and the effects of vorinostat on tumor growth and osteolytic disease were assessed by radiography, micro-computed tomography, and histologic and molecular analyses. Vorinostat-treated and control mice without tumors were also examined. Tumor growth in bone was reduced ∼33% by vorinostat with inhibited osteolysis in the first few weeks of the experiment. However, osteolysis became more severe in both the vehicle and vorinostat-treated groups. Vorinostat increased the expression of tumor-derived factors promoting bone resorption, including PTHrP, IL-8, and osteopontin. After 4 weeks of vorinostat therapy, the non-tumor-bearing contralateral femurs and limbs from vorinostat-treated tumor-free SCID mice showed significant bone loss (50% volume density of controls). Thus, our studies indicate that vorinostat effectively inhibits tumor growth in bone, but has a negative systemic effect reducing normal trabecular bone mass. Vorinostat treatment reduces tumor growth in bone and accompanying osteolytic disease as a result of decreased tumor burden in bone. However, vorinostat can promote osteopenia throughout the skeleton independent of tumor cell activity.

Pomalidomide therapy for myeloma

INTRODUCTION

The Office of National Statistics (London, UK) has reported 4040 new patients in the year 2007, with an annual age standardized incidence rate of 4.8 per 100,000 population (range 4.7 - 5.0). Overall survival (OS) in the last decade has improved from 2 - 3 years to 7 - 8 years in the UK. The introduction of IMids for the treatment of myeloma has had a significant impact on outcomes in this life-threatening disease.

AREAS COVERED

Pomalidomide, a thalidomide analogue, is a promising anti-myeloma agent with encouraging responses in relapsed/refractory myeloma patients. Pomalidomide has a potent anti-myeloma activity in vitro and in vivo, acting both directly on myeloma cells and on the cells in the bone marrow microenvironment. We have reviewed the chemistry and mechanisms of action of pomalidomide and the literature on pre-clinical and early Phase I and II clinical trials that demonstrates significant clinical efficacy in the relapsed setting and in lenalidomide refractory myeloma patients.

EXPERT OPINION

Pomalidomide has shown significant activity in relapsed/refractory disease and is now being taken into Phase III trials in combination with dexamethasone. The exact place of pomalidomide in the management of myeloma, however, is evolving as more clinical experience is gained with this agent and further data published from clinical trials.

The first Tianjin, China forum on tumor microenvironment

Although it is well recognized that the tumor microenvironment plays a key role in regulating tumor progression, the mechanisms through which this occurs need to be defined. Current international research activities toward defining the role of the tumor microenvironment in cancer progression were the subject of the first Tianjin Forum on Tumor Microenvironment held at Nankai University in Tianjin, China, July 2 to 4, 2010. The importance of variety of processes, such as inflammation and angiogenesis, in the role of tumor progression was described for multiple tumor types including breast, prostate, and hepatic cancers, as well as the process of bone metastasis. Identification of novel signaling pathways that impact both angiogenesis and bone remodeling were presented. Several themes emerged from this meeting, such as: (i) tumor cells modify the microenvironment to enhance their own survival and progression; (ii) targeting host factors, in addition to targeting tumor cells, will have important therapeutic effects; and (iii) host cells distribution within the tumor has both prognostic and therapeutic significance. Several priorities for future research were defined including use of a systems biology approach to define the role of host factors in tumor progression, to define the importance of targeting both arms of the bone remodeling process for therapy of bone metastasis, and to determine how different cell subsets contribute to microenvironment-mediated regulation of tumor progression.

Multiple myeloma: 2011 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Multiple myeloma is malignant plasma-cell disorder that accounts for ∼10% of all hematologic malignancies.

DIAGNOSIS

The diagnosis requires (1) 10% or more clonal plasma cells on bone marrow examination or a biopsy-proven plasmacytoma plus (2) evidence of end-organ damage felt to be related to the underlying plasma cell disorder.

RISK STRATIFICATION

Patients with 17p deletion, t(4;14), t(14;16), t(14;20), and karyotypic deletion 13 or hypodiploidy are considered to have high-risk myeloma. All others are considered to have standard-risk disease.

RISK-ADAPTED THERAPY

Standard-risk patients are treated with nonalkylator-based therapy such as lenalidomide plus low-dose dexamethasone (Rd) followed by autologous stem-cell transplantation (ASCT). If patients are tolerating the induction regimen treatment well, an alternative strategy is to continue initial therapy after stem-cell collection, reserving ASCT for first relapse. High-risk patients are treated with a bortezomib-based induction followed by ASCT and then bortezomib-based maintenance. Patients not eligible for ASCT can be treated with Rd for standard risk disease or a bortezomib-based regimen if high-risk features are present. To reduce toxicity, when using bortezomib, the once-weekly dose is preferred; similarly, when using dexamethasone, the low-dose approach (40 mg once a week) is preferred, unless there is a need for rapid disease control.

MANAGEMENT OF REFRACTORY DISEASE

Patients with indolent relapse can be treated first with lenalidomide, bortezomib, or alkylators plus low-dose corticosteroids. Patients with more aggressive relapse often require therapy with a combination of multiple active agents. The most promising new agents in development are pomalidomide and carfilizomib.

Bone disease from monoclonal gammopathy of undetermined significance to multiple myeloma: pathogenesis, interventions, and future opportunities

Manifestations of bone disease-osteopenia, osteolytic lesions, and fractures-are the hallmark of multiple myeloma (MM) and occur clinically in the vast majority of patients. These abnormalities can have devastating clinical effects by increasing both the morbidity and mortality of patients. Bone disease is usually found when patients are diagnosed with active MM; however, recent data suggest that it is present in early myelomagenesis, including patients with myeloma precursor disease, monoclonal gammopathy of undetermined significance (MGUS). The primary mechanisms of abnormal bone remodeling are increased osteoclastic activity, which occurs in close proximity to active myeloma cells, and decreased activity of the surrounding osteoblasts. Better understanding of the pathogenesis of bone disease in MM will allow us to enhance our current therapeutic options in the treatment of bone disease. In patients with active MM and at least one lytic lesion, intravenous bisphosphonates have been shown to decrease skeletal-related events and pain, improve performance status, and maintain quality of life. Emerging evidence suggests that intervention at earlier stages of disease may prevent skeletal-related events at time of progression, but there is no evidence that bisphosphonates in this setting change the natural history of the disease.

Successful treatment with a modified bortezomib schedule of weekly and longer intervals for patients with refractory/resistance multiple myeloma

Bortezomib is a potent agent for multiple myeloma (MM); however, severe treatment-related toxicities such as peripheral neuropathy have been observed in conjunction with its use. In this study, we present the cases of 9 patients with refractory MM whose administration schedule was modified from twice weekly to an interval of once weekly or longer mainly due to adverse events. The average duration from diagnosis to the time of bortezomib induction was 56 months. The schedule was changed to the modified administration according to the physician's discretion. The average duration of modified treatment was 16 months. Six patients with IgG or IgA subtype showed more than a minor response. One patient with BJP had stable disease for 3 years, and the other BJP-type patient with extramedullary plasmacytomas showed remarkable tumor regression. The treatment-related toxicities of this strategy were mild and tolerable. To our knowledge, this is the first report of the administration of bortezomib at intervals longer than once weekly.

Examining the metastatic niche: targeting the microenvironment

Some of the most common cancer types, including breast cancer, prostate cancer, and lung cancer, show a predilection to metastasize to bone. The molecular basis of this preferential growth of cancer cells in the bone microenvironment has been an area of active investigation. Although the precise molecular mechanisms underlying this process remain to be elucidated, it is now increasingly being recognized that the unique characteristics of the bone niche provide homing signals to cancer cells, and create a microenvironment conducive for the cancer cells to colonize. Concomitantly, cancer cells release several regulatory factors that result in abnormal bone destruction and/or formation. This complex bidirectional interplay between tumor cells and bone microenvironment establishes a "vicious cycle" that leads to a selective growth advantage for the cancer cells. The molecular insights gained on the underpinnings of bone metastasis in recent years have also provided us with avenues to devise innovative approaches for therapeutic intervention. The goal of this review is to describe our current understanding of molecular pathophysiology of cancer metastases to bone, as well as its therapeutic implications.

Heparanase enhances local and systemic osteolysis in multiple myeloma by upregulating the expression and secretion of RANKL

Excessive bone destruction is a major cause of morbidity in myeloma patients. However, the biological mechanisms involved in the pathogenesis of myeloma-induced bone disease are not fully understood. Heparanase, an enzyme that cleaves the heparan sulfate chains of proteoglycans, is upregulated in a variety of human tumors, including multiple myeloma. We previously showed that heparanase promotes robust myeloma tumor growth and supports spontaneous metastasis of tumor cells to bone. In the present study, we show, for the first time, that the expression of heparanase by myeloma tumor cells remarkably enhances bone destruction locally within the tumor microenvironment. In addition, enhanced heparanase expression in the primary tumor also stimulated systemic osteoclastogenesis and osteolysis, thus mimicking the systemic osteoporosis often seen in myeloma patients. These effects occur, at least in part, as the result of a significant elevation in the expression and secretion of receptor activator of NF-κB ligand (RANKL) by heparanase-expressing myeloma cells. Moreover, analysis of bone marrow biopsies from myeloma patients reveals a positive correlation between the level of expression of heparanase and RANKL. Together, these discoveries reveal a novel and key role for heparanase in promoting tumor osteolysis and show that RANKL is central to the mechanism of heparanase-mediated osteolysis in myeloma.

Pasteurella multocida toxin-stimulated osteoclast differentiation is B cell dependent

Pasteurella multocida is a Gram-negative bacillus that infects a number of wild and domestic animals, causing respiratory diseases. Toxigenic Pasteurella multocida strains produce a protein toxin (PMT) that leads to atrophic rhinitis in swine due to enhanced osteoclastogenesis and the inhibition of osteoblast function. We show that PMT-induced osteoclastogenesis is promoted by an as-yet-uncharacterized B-cell population. The toxin, however, is not acting at the level of hematopoietic stem cells, since purified CD117(+) cells from murine hematopoietic progenitor cells cultivated with PMT did not mature into osteoclasts. The early macrophages contained within this cell population (CD117(+)/CD11b(+)) did not further differentiate into osteoclasts but survived and were able to phagocytose. Within the CD117(-) population, however, we detected PMT-induced generation of a B220(+)/CD19(+) and B220(+)/IgM(+) B-cell population that was able to take up fluorescently labeled PMT. Using purified B-cell and macrophage populations, we show that these B cells are needed to efficiently generate osteoclasts from macrophages. Cells of the immune system are thought to affect osteoclast formation and function by secreting cytokines and growth factors. We show here that PMT-stimulated B cells produce elevated levels of the osteoclastogenic factors interleukin-1β (IL-1β), IL-6, tumor necrosis factor alpha, and receptor activator of nuclear factor receptor ligand (RANKL) compared to B cells generated through incubation with IL-7. These results suggest that the osteoclastic properties characteristic for PMT may result from a cross talk between bone cells and lymphoid cells and that B cells might be an important target of Pasteurella multocida.

Differential expression of DKK-1 binding receptors on stromal cells and myeloma cells results in their distinct response to secreted DKK-1 in myeloma

Background

The canonical Wnt signaling is concurrently important for osteoblast differentiation and myeloma cell proliferation. Its activation in myeloma cells and its inhibition in osteoblasts and their progenitors have been identified in the previous studies. Osteoblast progenitors and myeloma cells from a myeloma patient share the same bone marrow (BM) microenvironment, but respond differently to DKK-1 secreted by myeloma cells. The mechanisms remain unclear.

Methods

Primary multiple myeloma (MM) cells were isolated from BM mononuclear cells of 12 MM patients. Human bone marrow stromal cells (SCs) were obtained from BM adherent cells of these MM patients and 10 healthy donors. The mRNA expression levels of DKK-1 binding receptor LRP5/6 and Kremen1/2 (Krm1/2) were analyzed by Real-time PCR in human myeloma cell line (HMCL) RPMI-8226, NCI-H929, U266, LP-1, CZ-1, KM-3, Sko-007, primary myeloma cells and SCs from 12 MM patients and SCs from 10 healthy donors. The binding capability of DKK-1 binding receptors to DKK-1 on primary myeloma cells and SCs was detected by flow cytometry assay.

Results

The mRNA expression levels of DKK-1 binding receptor LRP5/6 and Krm1/2 in SCs from patients with MM were significantly higher than those in myeloma cells and in SCs from healthy donors. The binding capability to DKK-1of DKK-1 binding receptors on SCs from MM patients was obviously higher than those on myeloma cells and SCs from healthy donors by flow cytometry assay. Similar to the effects of coculture with rhDKK1, coculture of SCs from healthy donors with myeloma cells in the presence or absence of a Transwell insert did up-regulate SCs' mRNA levels of LRP5/6 and Krm1/2, and down-regulate their mRNA levels of β-catenin.

Conclusion

Compared with myeloma cells, the SCs from MM patients overexpress DKK-1 binding receptors LRP5/6 and Krm1/2 in response to DKK-1 secreted by myeloma cells, which results in intracellular Wnt signaling inhibition. Our study provides a novel insight into mechanisms of myeloma associated osteolytic lesions.

A proteasome inhibitor, bortezomib, inhibits breast cancer growth and reduces osteolysis by downregulating metastatic genes

PURPOSE

The incidence of bone metastasis in advanced breast cancer (BrCa) exceeds 70%. Bortezomib, a proteasome inhibitor used for the treatment of multiple myeloma, also promotes bone formation. We tested the hypothesis that proteasome inhibitors can ameliorate BrCa osteolytic disease.

EXPERIMENTAL DESIGN

To address the potentially beneficial effect of bortezomib in reducing tumor growth in the skeleton and counteracting bone osteolysis, human MDA-MB-231 BrCa cells were injected into the tibia of mice to model bone tumor growth for in vivo assessment of treatment regimens before and after tumor growth.

RESULTS

Controls exhibited tumor growth, destroying trabecular and cortical bone and invading muscle. Bortezomib treatment initiated following inoculation of tumor cells strikingly reduced tumor growth, restricted tumor cells mainly to the marrow cavity, and almost completely inhibited osteolysis in the bone microenvironment over a 3- to 4-week period as shown by [(18)F]fluorodeoxyglucose positron emission tomography, micro-computed tomography scanning, radiography, and histology. Thus, proteasome inhibition is effective in killing tumor cells within the bone. Pretreatment with bortezomib for 3 weeks before inoculation of tumor cells was also effective in reducing osteolysis. Our in vitro and in vivo studies indicate that mechanisms by which bortezomib inhibits tumor growth and reduces osteolysis result from inhibited cell proliferation, necrosis, and decreased expression of factors that promote BrCa tumor progression in bone.

CONCLUSION

These findings provide a basis for a novel strategy to treat patients with BrCa osteolytic lesions, and represent an approach for protecting the entire skeleton from metastatic bone disease.

Bone morphogenic protein 2 directly enhances differentiation of murine osteoclast precursors

Previous studies found that bone morphogenic proteins (BMPs) support osteoclast formation, but it is not clear whether this is a direct effect on osteoclasts or mediated indirectly through osteoblasts. We have shown that a mouse deficient for the BMP antagonist Twisted gastrulation suggested a direct positive role for BMPs on osteoclastogenesis. In this report, we further determine the significance of BMP signaling on osteoclast formation in vitro. We find that BMP2 synergizes with suboptimal levels of receptor activator of NF-kappaB ligand (RANKL) to enhance in vitro differentiation of osteoclast-like cells. The enhancement by BMP2 is not a result of changes in the rate of proliferation or survival of the bone marrow-derived cultures, but is accompanied by an increase in expression of genes involved in osteoclast differentiation and fusion. Treatment with BMP2 did not significantly alter expression of RANKL or OPG in our osteoclast cultures, suggesting that the enhancement of osteoclastogenesis is not mediated indirectly through osteoblasts or stromal cells. Consistent with this, we detected phosphorylated SMAD1,5,8 (p-SMAD) in the nuclei of mononuclear and multinucleated cells in osteoclast cultures. Levels of p-SMAD, BMP2, and BMP receptors increased during differentiation. RNAi suppression of Type II BMP receptor inhibited RANKL-stimulated formation of multinuclear TRAP-positive cells. The BMP antagonist noggin inhibited RANKL-mediated osteoclast differentiation when added prior to day 3, while addition of noggin on day 3 or later failed to inhibit their differentiation. Taken together, these data indicate that osteoclasts express BMP2 and BMP receptors, and that autocrine BMP signaling directly promotes the differentiation of osteoclasts-like cells.

Bone continuum of cancer

Many patients with solid tumors, especially breast and prostate cancers, and with multiple myeloma will develop bone metastases or other skeletal complications. The management of bone loss and symptomatic bone metastases is an important issue in the care and maintenance of quality of life for these patients. Morbidity caused by skeletal complications include pain (bone metastases are known as the most common cause of cancer-related pain), hypercalcemia, pathologic fracture, compression of the spinal cord or cauda equine, and spinal instability. Currently, the only Food and Drug Administration-approved therapy for metastatic bone disease is bisphosphonate therapy. A greater understanding of the biomolecular pathways that govern the bone continuum of cancer has helped identify novel targets for drug development. New therapeutic options are currently being investigated for the treatments of bone loss and symptomatic bone metastases. Some of these new drugs and modalities are in advanced stages of clinical development and may soon reach the clinic.

Osteoblastogenesis and tumor growth in myeloma

Myeloma is associated with suppression of osteoblastogenesis, consequentially resulting in increased osteoclast activity and induction of typical osteolytic bone disease. The molecular mechanisms by which myeloma cells suppress osteoblastogenesis and the consequences of increased osteoblast activity on myeloma cell growth have been partially delineated only recently. Reduced osteoblastogenesis is a consequence of abnormal properties and impaired osteogenic potential of osteoprogenitor cells from myeloma patients and is also the result of production of multiple osteoblastogenesis inhibitors by myeloma cells and by microenvironmental cells within the myelomatous bone. Nevertheless, novel osteoblast-activating agents (e.g. proteasome inhibitor bortezomib) are capable of inducing bone formation in myeloma animal models and clinically. These agents induce increased osteoblast activity, often coupled with a concomitant reduction in osteoclastogenesis, that is strongly associated with reduced myeloma tumor burden. In vitro, osteoblasts, in contrast to osteoclasts, attenuate the growth of myeloma cells from a large subset of patients; potential molecular mechanisms are discussed. These studies suggest that myeloma cells suppress osteoblastogenesis to their advantage and that increased osteoblast activity is a promising approach to treat myeloma bone disease and simultaneously control myeloma development and progression.

Haematological emergencies managing hypercalcaemia in adults and children with haematological disorders

Hypercalcaemia is a common metabolic complication of malignant disease often requiring emergency intervention. Although it is more frequently associated with solid tumours, malignancy-associated hypercalcaemia (MAH) is seen in a significant number of patients with blood diseases. Its association with myeloma and adult T-cell leukaemia/lymphoma is well recognized but the incidence of hypercalcaemia in other haematological neoplasms, affecting adults and children, is less clearly defined. Haematologists need to be familiar with the clinical manifestations of, the differential diagnosis to be considered and the most effective management strategies that are currently available for MAH. The key components of management of MAH include aggressive rehydration, specific therapy to inhibit bone resorption and, crucially, treatment of the underlying malignancy. Bisphosphonates have revolutionized the management of MAH over the last 20 years, however the elucidation of molecular pathways implicated in MAH is facilitating the development of more targeted approaches to treatment.

Systemic therapy of disseminated myeloma in passively immunized mice using measles virus-infected cell carriers

Multiple myeloma (MM) is bone marrow plasma cell malignancy. A clinical trial utilizing intravenous administration of oncolytic measles virus (MV) encoding the human sodium-iodide symporter (MV-NIS) is ongoing in myeloma patients. However, intravenously administered MV-NIS is rapidly neutralized by antiviral antibodies. Because myeloma cell lines retain bone marrow tropism, they may be ideal as carriers for delivery of MV-NIS to myeloma deposits. A disseminated human myeloma (KAS 6/1) model was established. Biodistribution of MM1, a myeloma cell line, was determined after intravenous infusion. MM1 cells were found in the spine, femurs, and mandibles of tumor-bearing mice. Lethally irradiated MM1 cells remained susceptible to measles infection and transferred MV to KAS 6/1 cells in the presence of measles immune sera. Mice-bearing disseminated myeloma and passively immunized with measles immune serum were given MV-NIS or lethally irradiated MV-NIS-infected MM1 carriers. The antitumor activity of MV-NIS was evident only in measles naive mice and not in passively immunized mice. In contrast, survivals of both measles naive and immune mice were extended using MV-NIS-infected MM1 cell carriers. Hence, we demonstrate for the first time that systemically administered cells can serve as MV carriers and prolonged survival of mice with pre-existing antimeasles antibodies.

Advances in the understanding of myeloma bone disease and tumour growth

Advances in multiple myeloma support the notion that the associated bone disease, characterized by increased osteoclastogenesis and suppressed osteoblastogenesis, is both a consequence and necessity of tumour progression. Osteoblastogenesis is suppressed by secreted inhibitors and dysregulation of cell-surface 'coupling' factors on osteogenic cells. Osteoclastogenesis is increased as a consequence of osteoblast deactivation and of production of osteoclast-activating factors. Osteoclasts express soluble and cell-surface factors that stimulate myeloma growth, while osteoblasts produce bone-building factors that restrain growth of myeloma cells that are dependent on the microenvironment; detailed molecular mechanisms are discussed. Experimental and clinical findings indicate that pharmacological and experimental osteoblast-activating agents that effectively promote bone formation also reduce growth of myeloma cells within bone, seemingly by simultaneously stimulating osteoblastogenesis and restraining osteoclastogenesis. Unravelling mechanisms of myeloma bone disease expands horizons for developing novel interventions and also facilitates better understanding of the association between induction of osteolysis and disease progression.