Role of osteoblast suppression in multiple myeloma

Roles of MicroRNAs in Osteogenesis or Adipogenesis Differentiation of Bone Marrow Stromal Progenitor Cells

Bone marrow stromal cells (BMSCs) are multipotent cells which can differentiate into chondrocytes, osteoblasts, and fat cells. Under pathological stress, reduced bone formation in favour of fat formation in the bone marrow has been observed through a switch in the differentiation of BMSCs. The bone/fat switch causes bone growth defects and disordered bone metabolism in bone marrow, for which the mechanisms remain unclear, and treatments are lacking. Studies suggest that small non-coding RNAs (microRNAs) could participate in regulating BMSC differentiation by disrupting the post-transcription of target genes, leading to bone/fat formation changes. This review presents an emerging concept of microRNA regulation in the bone/fat formation switch in bone marrow, the evidence for which is assembled mainly from in vivo and in vitro human or animal models. Characterization of changes to microRNAs reveals novel networks that mediate signalling and factors in regulating bone/fat switch and homeostasis. Recent advances in our understanding of microRNAs in their control in BMSC differentiation have provided valuable insights into underlying mechanisms and may have significant potential in development of new therapeutics.

Parathyroid hormone independent hypercalcemia in adults

Parathyroid independent hypercalcemia is characterized by suppressed parathyroid hormone (PTH) in the presence of hypercalcemia. Well known causes and mechanisms are redistribution of calcium from the skeleton, by malignant diseases; inadequately increased intestinal calcium uptake mediated by increased vitamin D activity, and reduced renal elimination due to medications. Frequent and infrequent causes are discussed, and more recent mechanistic models presented in this review. Most hypercalcemic conditions are stable and in equilibrium between the different organs, whereas the utmost severe cases are characterized by rapid rising calcium levels and renal failure, resulting in a vicious circle where a disequilibrium state is developed. Management and treatment depends on the underlying condition and severity. The aim of this review is to discuss non-parathyroid hypercalcemic conditions as seen in the modern clinic, with a focus on areas where recent gain of knowledge has been achieved.

Multiple Myeloma Exemplifies a Model of Cancer Based on Tissue Disruption as the Initiator Event

The standard model of multiple myeloma (MM) oncogenesis is based on the genetic instability of MM cells and presents its evolution as the emergence of clones with more and more aggressive genotypes, giving them surviving and proliferating advantage. The micro-environment has a passive role. In contrast, many works have shown that the progression of MM is also characterized by the selection of clones with extended phenotypes able to destroy bone trabeculae, suggesting a major role for early micro-environmental disruption. We present a model of MM oncogenesis in which genetic instability is the consequence of the disruption of normal interactions between plasma cells and their environment, the bone remodeling compartment. These interactions, which normally ensure the stability of the genotypes and phenotypes of normal plasma cells could be disrupted by many factors as soon as the early steps of the disease (MGUS, pre-MGUS states). Therapeutical implications of the model are presented.

New agents in the Treatment of Myeloma Bone Disease

Patients with multiple myeloma develop a devastating bone disease driven by the uncoupling of bone remodelling, excess osteoclastic bone resorption and diminished osteoblastic bone formation. The bone phenotype is typified by focal osteolytic lesions leading to pathological fractures, hypercalcaemia and other catastrophic bone events such as spinal cord compression. This causes bone pain, impaired functional status, decreased quality of life and increased mortality. Early in the disease, malignant plasma cells occupy a niche environment that encompasses their interaction with other key cellular components of the bone marrow microenvironment. Through these interactions, osteoclast-activating factors and osteoblast inhibitory factors are produced, which together uncouple the dynamic process of bone remodelling, leading to net bone loss and focal osteolytic lesions. Current management includes antiresorptive therapies, i.e. bisphosphonates, palliative support and orthopaedic interventions. Bisphosphonates are the mainstay of treatment for myeloma bone disease (MBD), but are only partially effective and do have some significant disadvantages; for example, they do not lead to the repair of existing bone destruction. Thus, newer agents to prevent bone destruction and also promote bone formation and repair existing lesions are warranted. This review summarises novel ways that MBD is being therapeutically targeted.

Mathematical modelling of the pathogenesis of multiple myeloma-induced bone disease

Multiple myeloma (MM) is the second most common haematological malignancy and results in destructive bone lesions. The interaction between MM cells and the bone microenvironment plays an important role in the development of the tumour cells and MM-induced bone disease and forms a 'vicious cycle' of tumour development and bone destruction, intensified by suppression of osteoblast activity and promotion of osteoclast activity. In this paper, a mathematical model is proposed to simulate how the interaction between MM cells and the bone microenvironment facilitates the development of the tumour cells and the resultant bone destruction. It includes both the roles of inhibited osteoblast activity and stimulated osteoclast activity. The model is able to mimic the temporal variation of bone cell concentrations and resultant bone volume after the invasion and then removal of the tumour cells and explains why MM-induced bone lesions rarely heal even after the complete removal of MM cells. The behaviour of the model compares well with published experimental data. The model serves as a first step to understand the development of MM-induced bone disease and could be applied further to evaluate the current therapies against MM-induced bone disease and even suggests new potential therapeutic targets.

A Phase IB multicentre dose-determination study of BHQ880 in combination with anti-myeloma therapy and zoledronic acid in patients with relapsed or refractory multiple myeloma and prior skeletal-related events

Dickkopf-1 (DKK1), expressed by myeloma cells, suppresses osteoblast function and plays a key role in bone disease in multiple myeloma. BHQ880, a human neutralizing IgG1 anti-DKK1 monoclonal antibody, is being investigated for its impact on multiple myeloma-related bone disease and as an agent with potential anti-myeloma activity. The primary objectives of this Phase IB study were to determine the maximum tolerated dose (MTD) of BHQ880 and to characterize the dose-limiting toxicity (DLT) of escalating doses in combination with anti-myeloma therapy and zoledronic acid. Twenty-eight patients were enrolled and received BHQ880 at doses of 3-40 mg/kg. No DLTs were reported, therefore, the MTD was not determined. The recommended Phase II dose was declared as 10 mg/kg, based mainly on saturation data. There was a general trend towards increased bone mineral density (BMD) observed over time; specific increases in spine BMD from Cycle 12 onwards irrespective of new skeletal-related events on study were observed, and increases in bone strength at the spine and hip were also demonstrated in some patients. BHQ880 in combination with zoledronic acid and anti-myeloma therapy was well tolerated and demonstrated potential clinical activity in patients with relapsed or refractory multiple myeloma.

Human placenta-derived adherent cells prevent bone loss, stimulate bone formation, and suppress growth of multiple myeloma in bone

Human placenta has emerged as a valuable source of transplantable cells of mesenchymal and hematopoietic origin for multiple cytotherapeutic purposes, including enhanced engraftment of hematopoietic stem cells, modulation of inflammation, bone repair, and cancer. Placenta-derived adherent cells (PDACs) are mesenchymal-like stem cells isolated from postpartum human placenta. Multiple myeloma is closely associated with induction of bone disease and large lytic lesions, which are often not repaired and are usually the sites of relapses. We evaluated the antimyeloma therapeutic potential, in vivo survival, and trafficking of PDACs in the severe combined immunodeficiency (SCID)-rab model of medullary myeloma-associated bone loss. Intrabone injection of PDACs into nonmyelomatous and myelomatous implanted bone in SCID-rab mice promoted bone formation by stimulating endogenous osteoblastogenesis, and most PDACs disappeared from bone within 4 weeks. PDACs inhibitory effects on myeloma bone disease and tumor growth were dose-dependent and comparable with those of fetal human mesenchymal stem cells (MSCs). Intrabone, but not subcutaneous, engraftment of PDACs inhibited bone disease and tumor growth in SCID-rab mice. Intratumor injection of PDACs had no effect on subcutaneous growth of myeloma cells. A small number of intravenously injected PDACs trafficked into myelomatous bone. Myeloma cell growth rate in vitro was lower in coculture with PDACs than with MSCs from human fetal bone or myeloma patients. PDACs also promoted apoptosis in osteoclast precursors and inhibited their differentiation. This study suggests that altering the bone marrow microenvironment with PDAC cytotherapy attenuates growth of myeloma and that PDAC cytotherapy is a promising therapeutic approach for myeloma osteolysis.

Open innovation for phenotypic drug discovery: The PD2 assay panel

Phenotypic lead generation strategies seek to identify compounds that modulate complex, physiologically relevant systems, an approach that is complementary to traditional, target-directed strategies. Unlike gene-specific assays, phenotypic assays interrogate multiple molecular targets and signaling pathways in a target "agnostic" fashion, which may reveal novel functions for well-studied proteins and discover new pathways of therapeutic value. Significantly, existing compound libraries may not have sufficient chemical diversity to fully leverage a phenotypic strategy. To address this issue, Eli Lilly and Company launched the Phenotypic Drug Discovery Initiative (PD(2)), a model of open innovation whereby external research groups can submit compounds for testing in a panel of Lilly phenotypic assays. This communication describes the statistical validation, operations, and initial screening results from the first PD(2) assay panel. Analysis of PD(2) submissions indicates that chemical diversity from open source collaborations complements internal sources. Screening results for the first 4691 compounds submitted to PD(2) have confirmed hit rates from 1.6% to 10%, with the majority of active compounds exhibiting acceptable potency and selectivity. Phenotypic lead generation strategies, in conjunction with novel chemical diversity obtained via open-source initiatives such as PD(2), may provide a means to identify compounds that modulate biology by novel mechanisms and expand the innovation potential of drug discovery.

Consequences of daily administered parathyroid hormone on myeloma growth, bone disease, and molecular profiling of whole myelomatous bone

BACKGROUND

Induction of osteolytic bone lesions in multiple myeloma is caused by an uncoupling of osteoclastic bone resorption and osteoblastic bone formation. Current management of myeloma bone disease is limited to the use of antiresorptive agents such as bisphosphonates.

METHODOLOGY/PRINCIPAL FINDINGS

We tested the effects of daily administered parathyroid hormone (PTH) on bone disease and myeloma growth, and we investigated molecular mechanisms by analyzing gene expression profiles of unique myeloma cell lines and primary myeloma cells engrafted in SCID-rab and SCID-hu mouse models. PTH resulted in increased bone mineral density of myelomatous bones and reduced tumor burden, which reflected the dependence of primary myeloma cells on the bone marrow microenvironment. Treatment with PTH also increased bone mineral density of uninvolved murine bones in myelomatous hosts and bone mineral density of implanted human bones in nonmyelomatous hosts. In myelomatous bone, PTH markedly increased the number of osteoblasts and bone-formation parameters, and the number of osteoclasts was unaffected or moderately reduced. Pretreatment with PTH before injecting myeloma cells increased bone mineral density of the implanted bone and delayed tumor progression. Human global gene expression profiling of myelomatous bones from SCID-hu mice treated with PTH or saline revealed activation of multiple distinct pathways involved in bone formation and coupling; involvement of Wnt signaling was prominent. Treatment with PTH also downregulated markers typically expressed by osteoclasts and myeloma cells, and altered expression of genes that control oxidative stress and inflammation. PTH receptors were not expressed by myeloma cells, and PTH had no effect on myeloma cell growth in vitro.

CONCLUSIONS/SIGNIFICANCE

We conclude that PTH-induced bone formation in myelomatous bones is mediated by activation of multiple signaling pathways involved in osteoblastogenesis and attenuated bone resorption and myeloma growth; mechanisms involve increased osteoblast production of anti-myeloma factors and minimized myeloma induction of inflammatory conditions.

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.

Multiple bone lesions and hypercalcemia presented in diffuse large B cell lymphoma: mimicking multiple myeloma?

We encountered a 58-year-old female patient who developed hypercalcemia and multiple bone lesions. She complained of lumbodorsal pain, nausea and vomiting on admission. Radiographic examination revealed multiple osteolytic lesions. She was diagnosed diffuse large B cell lymphoma (BLBCL) by bone marrow examination and biopsy of cervical lymph node. She underwent eight cycles of chemotherapy and is now in the stable stage. Osteogenic potential of mesenchymal stem cells from bone marrow was found to be correlated with the expression of Dickkopf1 (DKK-1) in the bone marrow plasma and lymphoma cells before and after treatment. PTH-related protein (PTHrP) expression was detectable in the lymphoma cells and was elevated in the serum. The receptor activator of nuclear factor kappaB ligand expression was found to be elevated in the bone marrow plasma and mesenchymal stem cells. These findings suggest that factors affecting the differentiation of both osteoblasts and osteoclasts involved in the pathogenesis of hypercalcemia and bone lesions of lymphoma. This was similar to that of multiple myeloma in which bone lesions and hypercalcemia are frequently observed.

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.

The ephrinB2/EphB4 axis is dysregulated in osteoprogenitors from myeloma patients and its activation affects myeloma bone disease and tumor growth

Myeloma bone disease is caused by uncoupling of osteoclastic bone resorption and osteoblastic bone formation. Bidirectional signaling between the cell-surface ligand ephrinB2 and its receptor, EphB4, is involved in the coupling of osteoblastogenesis and osteoclastogenesis and in angiogenesis. EphrinB2 and EphB4 expression in mesenchymal stem cells (MSCs) from myeloma patients and in bone cells in myelomatous bones was lower than in healthy counterparts. Wnt3a induced up-regulation of EphB4 in patient MSCs. Myeloma cells reduced expression of these genes in MSCs, whereas in vivo myeloma cell-conditioned media reduced EphB4 expression in bone. In osteoclast precursors, EphB4-Fc induced ephrinB2 phosphorylation with subsequent inhibition of NFATc1 and differentiation. In MSCs, EphB4-Fc did not induce ephrinB2 phosphorylation, whereas ephrinB2-Fc induced EphB4 phosphorylation and osteogenic differentiation. EphB4-Fc treatment of myelomatous SCID-hu mice inhibited myeloma growth, osteoclastosis, and angiogenesis and stimulated osteoblastogenesis and bone formation, whereas ephrinB2-Fc stimulated angiogenesis, osteoblastogenesis, and bone formation but had no effect on osteoclastogenesis and myeloma growth. These chimeric proteins had similar effects on normal bone. Myeloma cells expressed low to undetectable ephrinB2 and EphB4 and did not respond to the chimeric proteins. The ephrinB2/EphB4 axis is dysregulated in MM, and its activation by EphB4-Fc inhibits myeloma growth and bone disease.

Anti-DKK1 mAb (BHQ880) as a potential therapeutic agent for multiple myeloma

Decreased activity of osteoblasts (OBs) contributes to osteolytic lesions in multiple myeloma (MM). The production of the soluble Wnt inhibitor Dickkopf-1 (DKK1) by MM cells inhibits OB activity, and its serum level correlates with focal bone lesions in MM. Therefore, we have evaluated bone anabolic effects of a DKK1 neutralizing antibody (BHQ880) in MM. In vitro BHQ880 increased OB differentiation, neutralized the negative effect of MM cells on osteoblastogenesis, and reduced IL-6 secretion. In a severe combined immunodeficiency (SCID)-hu murine model of human MM, BHQ880 treatment led to a significant increase in OB number, serum human osteocalcin level, and trabecular bone. Although BHQ880 had no direct effect on MM cell growth, it significantly inhibited growth of MM cells in the presence of bone marrow stromal cells (BMSCs) in vitro. This effect was associated with inhibition of BMSC/MM cell adhesion and production of IL-6. In addition, BHQ880 up-regulated beta-catenin level while down-regulating nuclear factor-kappaB (NF-kappaB) activity in BMSC. Interestingly, we also observed in vivo inhibition of MM cell growth by BHQ880 treatment in the SCID-hu murine model. These results confirm DKK1 as an important therapeutic target in myeloma and provide the rationale for clinical evaluation of BHQ880 to improve bone disease and to inhibit MM growth.

The proteasome inhibitor, bortezomib suppresses primary myeloma and stimulates bone formation in myelomatous and nonmyelomatous bones in vivo

Multiple myeloma (MM), a hematologic malignancy of terminally differentiated plasma cells is closely associated with induction of osteolytic bone disease, induced by stimulation of osteoclastogenesis and suppression of osteoblastogenesis. The ubiquitin-proteasome pathway regulates differentiation of bone cells and MM cell growth. The proteasome inhibitor, bortezomib, is a clinical potent antimyeloma agent. The main goal of this study was to investigate the effect of bortezomib on myeloma-induced bone resorption and tumor growth in SCID-rab mice engrafted with MM cells from 16 patients. Antimyeloma response of bortezomib, which was evident in >50% of 16 experiments and resembled clinical response, was associated with significant increased bone mineral density (BMD) and osteoblast numbers, and reduced osteoclast numbers in myelomatous bones. This bone anabolic effect, which was also visualized on X-ray radiographs and confirmed by static and dynamic histomorphometric analyses, was unique to bortezomib and was not observed in hosts responding to melphalan, a chemotherapeutic drug widely used to treat MM. Bortezomib also increased BMD and osteoblasts number and reduced osteoclasts number in nonmyelomatous implanted bones. In vitro bortezomib directly suppressed human osteoclast formation and promoted maturation of osteoblasts. We conclude that bortezomib promotes bone formation in myelomatous and nonmyelomatous bones by simultaneously inhibiting osteoclastogenesis and stimulating osteoblastogenesis. As clinical and experimental studies indicate that bone disease is both a consequence and necessity of MM progression our results suggest and that bortezomib's effects on bone remodeling contribute to the antimyeloma efficacy of this drug.

Serum concentrations of DKK-1 decrease in patients with multiple myeloma responding to anti-myeloma treatment

Lytic bone destruction is a hallmark of multiple myeloma (MM) and is because of an uncoupling of bone remodeling. Secretion of Dickkopf (DKK)-1 by myeloma cells is a major factor which causes inhibition of osteoblast precursors. In this study, the effect of different treatment regimens for MM on serum DKK-1 was evaluated and correlated with the response to treatment in 101 myeloma patients receiving bortezomib, thalidomide, lenalidomide, adriamycin and dexamethasone (AD) or high-dose chemotherapy (HDCT) followed by autologous stem cell transplantation (ASCT). At baseline, myeloma patients had increased serum DKK-1 as compared with patients with MGUS (mean 3786 pg/mL vs. 1993 pg/mL). There was no difference between previously untreated MM patients and patients at relapse. A significant decrease of DKK-1 after therapy was seen in the following groups: Bortezomib (4059 pg/mL vs. 1862 pg/mL, P = 0.016), lenalidomide (11837 pg/mL vs. 4374 pg/mL, P = 0.039), AD (1668 pg/mL vs. 1241 pg/mL, P = 0.016), and AD + HDCT + ASCT (2446 pg/mL vs. 1082 pg/mL, P = 0.001). Thalidomide led to a non-significant decrease in DKK-1 (1705 pg/mL vs. 1269 pg/mL, P = 0.081). Within all groups, a significant decrease of DKK-1 was only seen in responders (i.e. patients achieving complete remission or partial remission), but not in non-responders. We show for the first time that serum DKK-1 levels decrease in myeloma patients responding to treatment, irrespective of the regimen chosen. These data suggest that myeloma cells are the main source of circulating DKK-1 protein and provide a framework for clinical trials on anti-DKK-1 treatment in MM.

Dkk1-induced inhibition of Wnt signaling in osteoblast differentiation is an underlying mechanism of bone loss in multiple myeloma

Expression of the Wnt signaling inhibitor, DKK1 by multiple myeloma cells is correlated with lytic bone disease in multiple myeloma. However, the mechanism(s) by which DKK1 contributes to this process is not clear. Herein, we analyzed the functional role of canonical Wnt signaling and Dkk1 inhibition of this pathway in bone morphogenic protein (BMP)-2-induced osteoblast differentiation. Osteoblast differentiation was measured by alkaline phosphatase (ALP) activity in murine (C2C12) and human pre-osteoblast (hFOB1.19) and osteoblast-like (Saos-2 and MG63) cell lines. Cytoplasmic beta-catenin protein was separated by E-cadherin-GST pull-down assay and analyzed by Western blotting. A dominant negative form of beta-catenin, Dkk1 and TCF reporter constructs were transfected into C2C12 cells. C2C12 cells were also transfected with siRNA specific to LRP5/6 to knockdown receptor expression. Canonical Wnt signaling was activated in these cell lines in response to Wnt3a as assessed by increased cytoplasmic, non-phosphorylated beta-catenin and TCF/LEF transcription activity. Recombinant Dkk1 and plasma from MM patients containing high levels of Dkk1 blocked Wnt3a-induced beta-catenin accumulation. Importantly, Dkk1 abrogated BMP-2 mediated osteoblast differentiation. The requirement for Wnt signaling in osteoblast differentiation was confirmed by the following observations: 1) overexpression of Dkk1 decreased endogenous beta-catenin and ALP activity; 2) silencing of Wnt receptor mRNAs blocked ALP activity; and 3) a dominant negative form of beta-catenin eliminated BMP-2-induced ALP activity. Furthermore, Wnt3a did not increase ALP activity nor did BMP-2 treatment result in beta-catenin stabilization indicating that cooperation between these two pathways is required, but they are not co-regulated by either ligand. These studies have revealed that autocrine Wnt signaling in osteoblasts is necessary to promote BMP-2-mediated differentiation of pre-osteoblast cells, while Wnt signaling alone is not capable of inducing such differentiation. Dkk1 inhibits this process and may be a key factor regulating pre-osteoblast differentiation and myeloma bone disease.

Wnt3a signaling within bone inhibits multiple myeloma bone disease and tumor growth

Canonical Wnt signaling is central to normal bone homeostasis, and secretion of Wnt signaling inhibitors by multiple myeloma (MM) cells contributes to MM-related bone resorption and disease progression. The aim of this study was to test the effect of Wnt3a on bone disease and growth of MM cells in vitro and in vivo. Although Wnt3a activated canonical signaling in the majority of MM cell lines and primary cells tested, Wnt3a had no effect on MM cell growth in vitro. Moreover, forced expression of Wnt3a in H929 MM cells conferred no growth advantage over empty vector-transfected cells in vitro or importantly when grown subcutaneously in severe combined immunodeficient (SCID) mice. Importantly, although H929 cells stably expressing an empty vector injected into human bone grew rapidly and induced a marked reduction in bone mineral density, bones engrafted with Wnt3a-expressing H929 cells were preserved, exhibited increased osteoblast-to-osteoclast ratios, and reduced tumor burden. Likewise, treatment of myelomatous SCID-hu mice, carrying primary disease, with recombinant Wnt3a stimulated bone formation and attenuated MM growth. These results provide further support of the potential anabolic and anti-MM effects of enhancing Wnt signaling in the bone.

Risks of cancer among a cohort of 23,935 men and women with osteoporosis

Low hormone levels among persons with osteoporosis may decrease risk of some cancers. Other osteoporosis risk factors, such as smoking and alcohol consumption, however, may increase risk. As these deleterious factors are more often associated with osteoporosis diagnosed prior to age 70 years, cancer risk may be higher in these younger persons than in the general population. To examine this hypothesis, a cohort study of 23,935 persons with osteoporosis was conducted in Denmark. Patients hospitalized with osteoporosis between 1978 and 1993 were identified in the Danish Inpatient Register. Linkage to the Danish Cancer Registry identified all cancer outcomes through 2003. Standardized incidence ratios (SIR) and 95% confidence intervals (95%CI) were calculated to compare cancer incidence in the cohort with that in the general population. Persons diagnosed prior to age 70 years were at increased cancer risk (women: SIR = 1.11, 95%CI = 1.04-1.19; men: SIR = 1.31, 95%CI = 1.13-1.50) due, in part, to increased risks of cancers of the buccal cavity, esophagus, liver, pancreas and lung. Persons diagnosed at ages 70 and older were at decreased risk (women: SIR = 0.91, 95%CI = 0.87-0.96; men: SIR = 0.89, 0.77-1.01) due, in part, to decreased risks of breast, endometrial, colon, rectal and brain cancers in women and prostate cancer in men. These results suggest that risk factors associated with earlier onset osteoporosis may be associated with increased risk of cancer. Conversely, factors associated with later onset osteoporosis may be related to a decreased risk of cancer.

Complications of myeloma therapy

The advent of new therapies for multiple myeloma brings new hope for patients but also new side effects. Emerging information about the risks of supportive care therapies, including long-term, high-intensity bisphosphonate use and erythropoiesis-stimulating agents, is examined. As the number of drugs in the myeloma armamentarium grows, so does the list of possible side effects and interactions. With current progress, not only are there more complications to consider but patients are also living longer and the risk for delayed complications is becoming more relevant. The author provides perspective about the risks for the most active and commonly used single-agent and combination myeloma therapies.

Antibody-based inhibition of DKK1 suppresses tumor-induced bone resorption and multiple myeloma growth in vivo

Dickkopf-1 (DKK1), a soluble inhibitor of Wnt signaling secreted by multiple myeloma (MM) cells contributes to osteolytic bone disease by inhibiting the differentiation of osteoblasts. In this study, we tested the effect of anti-DKK1 therapy on bone metabolism and tumor growth in a SCID-rab system. SCID-rab mice were engrafted with primary MM cells expressing varying levels of DKK1 from 11 patients and treated with control and DKK1-neutralizing antibodies for 4 to 6 weeks. Whereas bone mineral density (BMD) of the implanted myelomatous bone in control mice was reduced during the experimental period, the BMD in mice treated with anti-DKK1 increased from pretreatment levels (P < .001). Histologic examination revealed that myelomatous bones of anti-DKK1-treated mice had increased numbers of osteocalcin-expressing osteoblasts and reduced number of multinucleated TRAP-expressing osteoclasts. The bone anabolic effect of anti-DKK1 was associated with reduced MM burden (P < .04). Anti-DKK1 also significantly increased BMD of the implanted bone and murine femur in nonmyelomatous SCID-rab mice, suggesting that DKK1 is physiologically an important regulator of bone remodeling in adults. We conclude that DKK1 is a key player in MM bone disease and that blocking DKK1 activity in myelomatous bones reduces osteolytic bone resorption, increases bone formation, and helps control MM growth.

The molecular classification of multiple myeloma

To better define the molecular basis of multiple myeloma (MM), we performed unsupervised hierarchic clustering of mRNA expression profiles in CD138-enriched plasma cells from 414 newly diagnosed patients who went on to receive high-dose therapy and tandem stem cell transplants. Seven disease subtypes were validated that were strongly influenced by known genetic lesions, such as c-MAF- and MAFB-, CCND1- and CCND3-, and MMSET-activating translocations and hyperdiploidy. Indicative of the deregulation of common pathways by gene orthologs, common gene signatures were observed in cases with c-MAF and MAFB activation and CCND1 and CCND3 activation, the latter consisting of 2 subgroups, one characterized by expression of the early B-cell markers CD20 and PAX5. A low incidence of focal bone disease distinguished one and increased expression of proliferation-associated genes of another novel subgroup. Comprising varying fractions of each of the other 6 subgroups, the proliferation subgroup dominated at relapse, suggesting that this signature is linked to disease progression. Proliferation and MMSET-spike groups were characterized by significant overexpression of genes mapping to chromosome 1q, and both exhibited a poor prognosis relative to the other groups. A subset of cases with a predominating myeloid gene expression signature, excluded from the profiling analyses, had more favorable baseline characteristics and superior prognosis to those lacking this signature.