Myeloma bone disease: pathogenesis, current treatments and future targets

A review of the current status and future prospects of the bone remodeling process: Biological and mathematical perspectives

This review dives into the complex dynamics of bone remodeling, combining biological insights with mathematical perspectives to better understand this fundamental aspect of skeletal health. Bone, being a crucial part of our body, constantly renews itself, and with the growing number of individuals facing bone-related issues, research in this field is vital. In this review, we categorized and classified most common mathematical models used to simulate the mechanical behavior of bone under different loading and health conditions, shedding light on the evolving landscape of bone biology. While current models have effectively captured the essence of healthy bone remodeling, the ever-expanding knowledge in bone biology suggests an update in mathematical methods. Knowing the role of the skeleton in whole-body physiology, and looking at the recent discoveries about activities of bone cells emphasize the urgency of refining our mathematical descriptions of the bone remodeling process. The underexplored impact of bone diseases like osteoporosis, Paget's disease, or breast cancer on bone remodeling also points to the need for intensified research into diverse disease types and their unique effects on bone health. By reviewing a range of bone remodeling models, we show the necessity for tailor-made mathematical models to decipher their roots and enhance patient treatment strategies. Collaboration among scientists from various domains is pivotal to surmount these challenges, ensuring improved accuracy and applicability of mathematical models. Ultimately, this effort aims to deepen our understanding of bone remodeling processes and their broader implications for diverse health conditions.

A novel role for the peptidyl-prolyl cis-trans isomerase Cyclophilin A in DNA-repair following replication fork stalling via the MRE11-RAD50-NBS1 complex

Cyclosporin A (CsA) induces DNA double-strand breaks in LIG4 syndrome fibroblasts, specifically upon transit through S-phase. The basis underlying this has not been described. CsA-induced genomic instability may reflect a direct role of Cyclophilin A (CYPA) in DNA repair. CYPA is a peptidyl-prolyl cis-trans isomerase (PPI). CsA inhibits the PPI activity of CYPA. Using an integrated approach involving CRISPR/Cas9-engineering, siRNA, BioID, co-immunoprecipitation, pathway-specific DNA repair investigations as well as protein expression interaction analysis, we describe novel impacts of CYPA loss and inhibition on DNA repair. We characterise a direct CYPA interaction with the NBS1 component of the MRE11-RAD50-NBS1 complex, providing evidence that CYPA influences DNA repair at the level of DNA end resection. We define a set of genetic vulnerabilities associated with CYPA loss and inhibition, identifying DNA replication fork protection as an important determinant of viability. We explore examples of how CYPA inhibition may be exploited to selectively kill cancers sharing characteristic genomic instability profiles, including MYCN-driven Neuroblastoma, Multiple Myeloma and Chronic Myelogenous Leukaemia. These findings propose a repurposing strategy for Cyclophilin inhibitors.

What Lies behind Paraneoplastic Hypercalcemia Secondary to Well-Differentiated Neuroendocrine Neoplasms? A Systematic Review of the Literature

BACKGROUND

Neuroendocrine neoplasms (NEN) originate from neuroendocrine cells ubiquitously spread throughout the body. Hypercalcemia associated with cancer is the most common life-threatening metabolic disorder in patients with advanced stage cancer. Paraneoplastic hypercalcemia is more commonly associated with hematological malignancies, renal and breast carcinomas, and squamous cell carcinomas, but it has also been described in patients with well-differentiated NEN, where it often remains undiagnosed. Among its causes, systemic secretion of parathyroid hormone-related protein (PTHrP) and ectopic production of 1,25-dihydroxyvitamin D and parathyroid hormone (PTH) may be considered paraneoplastic causes of hypercalcemia. In order to clarify the diagnostic work up of paraneoplastic hypercalcemia in patients with NEN, we perform a systematic review, which is lacking in the literature.

METHODS

We performed a data search using MEDLINE and SCOPUS including papers from 1961 to 2021. We selected articles on paraneoplastic hypercalcemia associated with well-differentiated NEN.

RESULTS

The search led to the selection of 78 publications for a total of 114 patients. Pooled data showed that the most frequent primary tumor site associated with paraneoplastic hypercalcemia was pancreatic NEN, followed by Pheochromocytoma. In most cases, paraneoplastic hypercalcemia was caused by PTHrP production and secretion. In more than two thirds of cases, paraneoplastic hypercalcemia was present at the time of NEN diagnosis and, in metachronous cases, was related to local recurrence, distant metastasis development, or tumor progression. In most patients, a combination of therapeutic approaches was employed, and reduction of the tumor burden was essential to control the paraneoplastic syndrome.

DISCUSSION

The onset of hypercalcemia associated with cancer in patients with well-differentiated NEN represents a major clinical challenge. The complex clinical and therapeutical management of paraneoplastic hypercalcemia implies the need for a multidisciplinary approach, aimed at controlling the clinical syndrome and tumor growth.

The role of the bone microenvironment in regulating myeloma residual disease and treatment

Multiple myeloma is an incurable haematological cancer. The increase in targeted therapies has improved the number of myeloma patients achieving a complete response and improved progression-free survival following therapy. However, a low level of disease or minimal residual disease (MRD) still persists which contributes to the inevitable relapse in myeloma patients. MRD has been attributed to the presence of dormant myeloma cells and their subsequent reactivation, which is controlled by the microenvironment and specialised niches within the bone marrow. This contributes to the evasion of the immune system and chemotherapy, eventually leading to relapse. The growth of myeloma tumours are heavily dependent on environmental stimuli from the bone marrow microenvironment, and this plays a key role in myeloma progression. The bone microenvironment also plays a critical role in myeloma bone disease and the development of skeletal-related events. This review focuses on the bone marrow microenvironment in relation to myeloma pathogenesis and cancer dormancy. Moreover, it reviews the current therapies targeting the bone microenvironment to treat myeloma and myeloma bone disease. Lastly, it identifies novel therapeutic targets for myeloma treatment and the associated bone disease.

Down-regulation of circ_0058058 suppresses proliferation, angiogenesis and metastasis in multiple myeloma through miR-338-3p/ATG14 pathway

Background

Multiple myeloma (MM) is one of the most frequently diagnosed hematological malignancy. Dysregulation of circular RNAs (circRNAs) has important impacts on MM process. Herein, this work aimed to investigate the role and mechanism of circ_0058058 in MM progression.

Methods

Levels of genes and proteins were detected by real-time reverse transcription PCR (RT-qPCR) and Western blot. CCK-8 assay, colony formation assay, EdU assay, flow cytometry, tube formation assay, transwell assay and Western blot were utilized to detect the proliferation, apoptosis, angiogenesis and metastasis of MM cells. The target relationship between miR-338-3p and circ_0058058 or ATG14 (autophagy related 14) was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. In vivo experiments were performed using Xenograft assay.

Results

Circ_0058058 was up-regulated in MM bone marrow aspirates and cells, knockdown of circ_0058058 reduced MM cell proliferation, angiogenesis and metastasis, but induced apoptosis in vitro. In a MM xenograft mouse model, circ_0058058 silencing reduced MM tumor growth and cell proliferation. Mechanistically, circ_0058058 acted as a sponge for miR-338-3p to up-regulate ATG14 expression, which was validated to be a target of miR-338-3p. Rescue assay showed that miR-338-3p inhibition reversed the antitumor effects of circ_0058058 knockdown on MM cell. Moreover, forced expression of miR-338-3p suppressed MM cell malignant phenotype, which was abolished by ATG14 up-regulation.

Conclusion

Circ_0058058 functions as a sponge for miR-338-3p to elevate ATG14 expression to promote MM cell proliferation, metastasis and angiogenesis, affording a potential therapeutic target for MM prevention.

Bone Pain in Multiple Myeloma (BPMM)-A Protocol for a Prospective, Longitudinal, Observational Study

Simple Summary

Multiple myeloma is a bone marrow cancer that often causes bone pain, but little is known about the pain characteristics and mechanisms in this condition. This clinical study aims to: 1. characterize the type, location and intensity of pain in myeloma patients, and its effect of quality of life, and 2. investigate whether the nerve fibers in the bone of myeloma patients are altered. We will also explore whether pain intensity is correlated to blood indicators of inflammation or bone damage. Study results will help identify the mechanisms of myeloma-induced bone pain, allowing the development of new analgesics for these patients.

Abstract

Multiple myeloma (MM) is a bone marrow neoplasia that causes bone pain in 70% patients. While preclinical models of MM have suggested that both nerve sprouting and nerve injury may be causative for the pain, there is a lack of clinical data. Thus, the primary aims of this clinical study are: (1) to provide a deep characterization of the subjective experience of pain and quality of life in MM patients; (2) to investigate disturbances in the bone innervation of MM patients. Secondary aims include exploring correlations between pain and serum inflammatory and bone turnover biomarkers. In a prospective, observational study (clinicaltrials.gov: NCT04273425), patients with suspected MM requiring a diagnostic iliac crest biopsy at Sheffield Teaching Hospital (UK) are invited to participate. Consenting patients answer seven standardized questionnaires assessing pain, quality of life and catastrophizing. Bone turnover biomarkers and inflammatory cytokines are measured in fasting serum samples, and bone innervation is evaluated in diagnostic biopsies. MM patients are invited to a follow-up upon completion of first line treatment. This will be the first deep characterization of pain in MM patients and its correlation with disturbances in bone innervation. Understanding how bone turnover and inflammation correlate to pain in MM is crucial to identify novel analgesic targets for this condition.

Sensory denervation increases potential of bisphosphonates to induce osteonecrosis via disproportionate expression of calcitonin gene-related peptide and substance P

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious side effect of systematic administration of bisphosphonates (BPs). Sensory innervation is crucial for bone healing. We established inferior alveolar nerve injury (IANI) and inferior alveolar nerve transection (IANT) models characterized by disorganized periosteum, increased osteoclasts, and unbalanced neuropeptide expression. Zoledronate injection disrupted neuropeptide expression in the IANI and IANT models by decreasing calcitonin gene-related peptide (CGRP) and increasing substance P (SP); associated with this, BRONJ prevalence was significantly higher in the IANT model, followed by the IANI model and the sham control. CGRP treatment significantly reduced BRONJ occurrence, whereas SP administration had the opposite effect. In vitro, RAW 264.7 cells were treated with BPs and then CGRP and/or SP to study changes in zoledronate toxicity; combined application of CGRP and SP decreased zoledronate toxicity, whereas CGRP or SP applied alone showed no effects. These results demonstrate that sensory denervation facilitates the occurrence of BRONJ and that CGRP used therapeutically may prevent BRONJ progression, provided that SP is also present. Further studies are necessary to determine the optimal ratio of CGRP to SP for promoting bone healing and to uncover the mechanism by which CGRP and SP cooperate.

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

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

Hypercalcemia caused by humoral effects and bone damage indicate poor outcomes in newly diagnosed multiple myeloma patients

BACKGROUND

Hypercalcemia of malignancy (HCM) is a serious metabolic complication, and the highest rates are in multiple myeloma (MM). The cause of hypercalcemia in newly diagnosed multiple myeloma (NDMM) remains unknown. We sought to evaluate the prognostic impact and mechanism of hypercalcemia in patients with symptomatic NDMM.

METHODS

We studied all consecutive MM patients who were initially diagnosed and followed up at Beijing Jishuitan Hospital between February 2013 and December 2019; 357 patients were included in the retrospective analysis.

RESULTS

A total of 16.8% of MM patients presented with hypercalcemia at the time of MM diagnosis. The presence of hypercalcemia was associated with higher serum levels of β2 microglobulin, creatinine, phosphorus, uric acid, procollagen I N-terminal peptide, β-carboxy-terminal cross-linking telopeptide of type I collagen and osteocalcin, lower serum levels of hemoglobin, parathyroid hormone (PTH), and advanced ISS and R-ISS stages. Multivariate analysis showed that serum PTH, hemoglobin, creatinine, and uric acid levels were the main factors affecting hypercalcemia. The presence of hypercalcemia was associated with significantly inferior survival (40 months vs 57 months, p < 0.05) based on univariate analysis, and it remained an independent poor prognostic factor (HR: 1.854, 95% CI: 1.006-3.415, adjusted p = 0.048) in a multivariate model that included age and R-ISS stage.

CONCLUSION

This study shows that hypercalcemia is associated with poor survival and is caused by manifold factors with humoral effects and local bone destruction.

Multiple myeloma-A painful disease of the bone marrow

Multiple myeloma is a bone marrow neoplasia with an incidence of 6/100,000/year in Europe. While the disease remains incurable, the development of novel treatments such as autologous stem cell transplantation, proteasome inhibitors and monoclonal antibodies has led to an increasing subset of patients living with long-term myeloma. However, more than two thirds of patients suffer from bone pain, often described as severe, and knowledge on the pain mechanisms and its effect on their health-related quality of life (HRQoL) is limited. In this review, we discuss the mechanisms of myeloma bone disease, the currently available anti-myeloma treatments and the lessons learnt from clinical studies regarding HRQoL in myeloma patients. Moreover, we discuss the mechanisms of cancer-induced bone pain and the knowledge that animal models of myeloma-induced bone pain can provide to identify novel analgesic targets. To date, information regarding bone pain and HRQoL in myeloma patients is still scarce and an effort should be made to use standardised questionnaires to assess patient-reported outcomes that allow inter-study comparisons of the available clinical data.

Toward a Mathematical Modeling of Diseases' Impact on Bone Remodeling: Technical Review

A wide variety of bone diseases have hitherto been discovered, such as osteoporosis, Paget's disease, osteopetrosis, and metastatic bone disease, which are not well defined in terms of changes in biochemical and mechanobiological regulatory factors. Some of these diseases are secondary to other pathologies, including cancer, or to some clinical treatments. To better understand bone behavior and prevent its deterioration, bone biomechanics have been the subject of mathematical modeling that exponentially increased over the last years. These models are becoming increasingly complex. The current paper provides a timely and critical analysis of previously developed bone remodeling mathematical models, particularly those addressing bone diseases. Besides, mechanistic pharmacokinetic/pharmacodynamic (PK/PD) models, which englobe bone disease and its treatment's effect on bone health. Therefore, the review starts by presenting bone remodeling cycle and mathematical models describing this process, followed by introducing some bone diseases and discussing models of pathological mechanisms affecting bone, and concludes with exhibiting the available bone treatment procedures considered in the PK/PD models.

Human P2X7 Receptor Causes Cycle Arrest in RPMI-8226 Myeloma Cells to Alter the Interaction with Osteoblasts and Osteoclasts

Multiple myeloma is a malignant expansion of plasma cells and aggressively affects bone health. We show that P2X7 receptor altered myeloma growth, which affects primary bone cells in vitro. Expression on six human myeloma cell lines confirmed the heterogeneity associated with P2X7 receptor. Pharmacology with 2′(3′)-O-(4-benzoylbenzoyl) adenosine 5′-triphosphate (BzATP) as agonist showed dose-dependent membranal pores on RPMI-8226 (p = 0.0027) and blockade with P2X7 receptor antagonists. Ca²⁺ influx with increasing doses of BzATP (p = 0.0040) was also inhibited with antagonists. Chronic P2X7 receptor activation reduced RPMI-8226 viability (p = 0.0208). No apoptosis or RPMI-8226 death was observed by annexin V/propidium iodide (PI) labeling and caspase-3 cleavage, respectively. However, bromodeoxyuridine (BrdU) labelling showed an accumulation of RPMI-8226 in the S phase of cell cycle progression (61.5%, p = 0.0114) with significant decline in G0/G1 (5.2%, p = 0.0086) and G2/M (23.5%, p = 0.0015) phases. As myeloma pathology depends on a positive and proximal interaction with bone, we show that P2X7 receptor on RPMI-8226 inhibited the myeloma-induced suppression on mineralization (p = 0.0286) and reversed the excessive osteoclastic resorption. Our results demonstrate a view of how myeloma cell growth is halted by P2X7 receptor and the consequences on myeloma–osteoblast and myeloma–osteoclast interaction in vitro.

Examining variation in skeletal tuberculosis in a late pre-contact population from the eastern mountains of Peru

OBJECTIVE AND MATERIALS

This research evaluates the presence and chronology of tuberculosis (TB) in the northeastern highlands of Peru (CE 800-1535) through the analysis of osseous lesions from Pre-Contact Kuelap, Chachapoyas.

METHODS

We examined macroscopic lesion morphology and distribution from the skeletal series (MNI = 207).

RESULTS

We determined that skeletal evidence was highly consistent with advanced multifocal and spinal tuberculosis in 13 individuals. Destructive lesions of the lower thoracic and/or lumbar vertebra bodies and sacroiliac joints are evident in most cases, but we also observed lesions within the manubriosternal, hip, and knee joints. Both adult males (n = 7) and females (n = 6) present skeletal lesions from young adult to older adults, but there is only one late adolescent. Only three individuals demonstrate similar lesion distributions.

CONCLUSIONS

Variation in lesion distribution in this population-based study shows the importance of identifying extra-vertebral tuberculosis and suggests that the disease may have manifested differently than at other coastal sites. These cases confirm the presence of tuberculosis both before and after Inca occupation across this central Andean highlands region.

SIGNIFICANCE

This evidence for the likely endemic presence of TB in the New World prior to European Contact furthers our understanding of the distribution of this infectious disease across the region as well as elucidating lesion distribution.

LIMITATIONS

The diagnosis of tuberculosis is based on skeletal lesions and it should be confirmed by molecular analysis.

FUTURE RESEARCH

Additional examination of vertebral bodies (including juvenile remains) for evidence of earlier manifestations of infection.

Circular RNAs in Blood Malignancies

Circular (circ)RNAs influence a wide range of biological processes at least in part by interacting with proteins and microRNAs. CircRNAs expressed in the hematopoietic compartment have been increasingly recognized as modulators of physiological and pathological features of hematopoetic stem cell (HSC)-derived populations. In particular, several circRNAs were found to enhance or suppress tumor progression in blood malignancies such as leukemias and lymphomas. Moreover, numerous circRNAs have been proposed to help confer resistance to the conventional treatments used in hematopoietic cancers. Here, we review the most important circRNAs described thus far in acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), lymphomas, and multiple myeloma (MM). We discuss the usefulness of circRNAs as diagnostic and prognostic markers and their potential value as therapeutic targets.

Comprehensive profiling of circular RNA expressions reveals potential diagnostic and prognostic biomarkers in multiple myeloma

Background

This study aimed to explore the heterogeneity of circRNA expression pattern via microarray, and further evaluate the potential of 10 specific circRNAs as diagnostic and prognostic biomarkers in multiple myeloma (MM).

Methods

In exploration stage (stage I), circRNA expression profiles were detected by the microarray in bone marrow plasma cells from 4 MM patients and 4 healthy controls (HCs), and bioinformatic analyses were performed. In validation stage (stage II), top 10 upregulated and top 10 downregulated circRNAs identified in stage I were detected in 60 MM patients and 30 HCs for further validation; the diagnostic and prognostic values of these circRNAs in MM patients were analyzed.

Results

In stage I, 122 upregulated and 260 downregulated circRNAs were identified in MM patients compared with HCs. GO, KEGG and pathway enrichment analyses revealed that these circRNAs were implicated in neoplastic pathways such as MAPK and VEGF signaling pathways. In stage II, circ-PTK2, circ-RNF217, circ-RERE, circ-NAGPA and circ-KCNQ5 were validated to be upregulated and circ-AFF2, circ-WWC3, circ-DNAJC5, circ-KLHL2, circ-IQGAP1 and circ-AL137655 were validated to be downregulated in MM compared with controls. Circ-PTK2 and circ-RNF217 were correlated with poor treatment response and survival, while circ-AFF2 predicted good treatment response and survival in MM patients.

Conclusions

This study provides valuable reference for profound understanding about circRNA expression patterns in MM, and validates that circ-PTK2, circ-RNF217 and circ-AFF2 might serve as potential prognostic biomarkers in MM.

Differential Pain-Related Behaviors and Bone Disease in Immunocompetent Mouse Models of Myeloma

Bone pain is a serious and debilitating symptom of multiple myeloma (MM) that impairs the quality of life of patients. The underlying mechanisms of the pain are unknown and understudied, and there is a need for immunocompetent preclinical models of myeloma-induced bone pain. The aim of this study was to provide the first in-depth behavioral characterization of an immunocompetent mouse model of MM presenting the clinical disease features: osteolytic bone disease and bone pain. We hypothesized that a widely used syngeneic model of MM, established by systemic inoculation of green fluorescent protein-tagged myeloma cells (5TGM1-GFP) in immunocompetent C57Bl/KaLwRijHsd (BKAL) mice, would present pain-related behaviors. Disease phenotype was confirmed by splenomegaly, high serum paraprotein, and tumor infiltration in the bone marrow of the hind limbs; however, myeloma-bearing mice did not present pain-related behaviors or substantial bone disease. Thus, we investigated an alternative model in which 5TGM1-GFP cells were directly inoculated into the intrafemoral medullary cavity. This localized myeloma model presented the hallmarks of the disease, including high serum paraprotein, tumor growth, and osteolytic bone lesions. Compared with control mice, myeloma-bearing mice presented myeloma-induced pain-related behaviors, a phenotype that was reversed by systemic morphine treatment. Micro-computed tomography analyses of the myeloma-inoculated femurs showed bone disease in cortical and trabecular bone. Repeated systemic bisphosphonate treatment induced an amelioration of the nociceptive phenotype, but did not completely reverse it. Furthermore, intrafemorally injected mice presented a profound denervation of the myeloma-bearing bones, a previously unknown feature of the disease. This study reports the intrafemoral inoculation of 5TGM1-GFP cells as a robust immunocompetent model of myeloma-induced bone pain, with consistent bone loss. Moreover, the data suggest that myeloma-induced bone pain is caused by a combinatorial mechanism including osteolysis and bone marrow denervation. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

STAT3 Activation and Oncogenesis in Lymphoma

Signal transducer and activator of transcription 3 (STAT3) is an important and the most studied transcription factor in the Janus kinase (JAK)/STAT signaling pathway. STAT3 mediates the expression of various genes that play a critical role in many cellular and biological processes, such as cell proliferation, survival, differentiation, migration, angiogenesis, and inflammation. STAT3 and associated JAKs are activated and tightly regulated by a variety of cytokines and growth factors and their receptors in normal immune responses. However, abnormal expression of STAT3 leads to its constitutive activation, which promotes malignant transformation and tumor progression through oncogenic gene expression in numerous human cancers. Human lymphoma is a heterogeneous malignancy of T and B lymphocytes. Constitutive signaling by STAT3 is an oncogenic driver in several types of B-cell lymphoma and most of T-cell lymphomas. Aberrant STAT3 activation can also induce inappropriate expression of genes involved in tumor immune evasion such as PD-L1. In this review, we focus on the oncogenic role of STAT3 in human lymphoma and highlight potential therapeutic intervention by targeting JAK/STAT3 signaling.

TGFβ Inhibition Stimulates Collagen Maturation to Enhance Bone Repair and Fracture Resistance in a Murine Myeloma Model

Multiple myeloma is a plasma cell malignancy that causes debilitating bone disease and fractures, in which TGFβ plays a central role. Current treatments do not repair existing damage and fractures remain a common occurrence. We developed a novel low tumor phase murine model mimicking the plateau phase in patients as we hypothesized this would be an ideal time to treat with a bone anabolic. Using in vivo μCT we show substantial and rapid bone lesion repair (and prevention) driven by SD-208 (TGFβ receptor I kinase inhibitor) and chemotherapy (bortezomib and lenalidomide) in mice with human U266-GFP-luc myeloma. We discovered that lesion repair occurred via an intramembranous fracture repair-like mechanism and that SD-208 enhanced collagen matrix maturation to significantly improve fracture resistance. Lesion healing was associated with VEGFA expression in woven bone, reduced osteocyte-derived PTHrP, increased osteoblasts, decreased osteoclasts, and lower serum tartrate-resistant acid phosphatase 5b (TRACP-5b). SD-208 also completely prevented bone lesion development in mice with aggressive JJN3 tumors, and was more effective than an anti-TGFβ neutralizing antibody (1D11). We also discovered that SD-208 promoted osteoblastic differentiation (and overcame the TGFβ-induced block in osteoblastogenesis) in myeloma patient bone marrow stromal cells in vitro, comparable to normal donors. The improved bone quality and fracture-resistance with SD-208 provides incentive for clinical translation to improve myeloma patient quality of life by reducing fracture risk and fatality. © 2019 American Society for Bone and Mineral Research.

Prevention Of Skeletal Related Events In Multiple Myeloma: Focus On The RANK-L Pathway In The Treatment Of Multiple Myeloma

More than 90% of patients with multiple myeloma (MM) have osteolytic bone lesions which increase the risk of skeletal-related events (SRE). The cytokine milieu in the bone marrow microenvironment (BMME) of MM plays a key role in myeloma bone disease by impairing the balance between osteoclastogenesis and osteoblastogenesis. This is orchestrated by the malignant plasma cell (MPC) with the ultimate outcome of MPC proliferation and survival at the expense of excess osteoclast activation resulting in osteolytic bone lesions. Prevention of SRE is currently accomplished by the inhibition of osteoclasts. Bisphosphonates (BPs) are pyrophosphate analogues that cause apoptosis of osteoclasts and have been proven to prevent and delay SRE. Denosumab, a fully humanized monoclonal antibody that binds and inhibits receptor activator of nuclear factor-ĸB ligand (RANKL), a key molecule in the BMME crucial for osteoclastogenesis, is also approved for the prevention of SRE in MM. The addition of BPs and denosumab to standard MM treatment affords a survival benefit for patients with MM. Specifically, the addition of denosumab to standard MM treatments results in superior PFS compared to BPs, highlighting the key role of the RANKL pathway in MM. This review focuses on the pathophysiology of myeloma bone disease as well as on the importance of targeting the RANK-L pathway for the treatment of MM and prevention of SRE.

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

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

CircRNA circ_0000190 inhibits the progression of multiple myeloma through modulating miR-767-5p/MAPK4 pathway

Background

Multiple myeloma (MM) accounts for 10% of all hematological malignancies. Dysregulation of microRNAs (miRNAs) or long non-coding RNAs (lncRNAs) has important impacts on progression of MM. Circular RNAs (circRNAs) are correlated with malignancy in the modulation of tumor progression. This study aims to investigate the effect of circ_0000190 on regulating the progression of MM.

Method

Microscopic examination via single molecule fluorescent in situ hybridization indicates the location of circ_0000190. qRT-PCR and Western blot were used to evaluate the expression of RNAs and proteins. Potential target of circ_0000190 was searched as miRNA, and examined by luciferase reporter assay. A computational screen was also conducted to search the potential target of miRNA. In vitro cell viability, proliferation, apoptosis assays and flow cytometric were performed to assess the effects of circ_0000190 and its target on MM. Mice model of human MM was established with subcutaneous xenograft tumor, qRT-PCR and western blot were performed to detect the underlying mechanisms of circ_0000190 on MM.

Results

Circ_0000190 was located in the cytoplasm, and down-regulated in both bone marrow tissue and peripheral blood, while the target of circ_0000190, miR-767-5p, was up-regulated, suggesting a negative correlation between them. The binding ability between circ_0000190 and miR-767-5p was confirmed by luciferase reporter assay. Moreover, circ_0000190 inhibited cell viability, proliferation and induced apoptosis of MM thus inhibiting cell progression, which is partially through the negative regulation of miR-767-5p. Mitogen-activated protein kinase 4 (MAPK4) is a direct target of miR-767-5p. In addition, over-expression of miR-767-5p promoted cell progression by directly targeting and regulating MAPK4. The MM model mice with administration of circ_0000190 suppressed tumor growth and progression.

Conclusion

Our results revealed that the ability of circ_0000190 to protect against MM was inherited through repression of miR-767-5p, and miR-767-5p might be a tumor drive through targeting MAPK4. Therefore, a novel role of circ_0000190 on regulating the progression of MM was found, and the clinical application of circRNAs might represent a strategy in MM.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1071-9) contains supplementary material, which is available to authorized users.

Mesenchymal lineage cells and their importance in B lymphocyte niches

Early B lymphopoiesis occurs in the bone marrow and is reliant on interactions with numerous cell types in the bone marrow microenvironment, particularly those of the mesenchymal lineage. Each cellular niche that supports the distinct stages of B lymphopoiesis is unique. Different cell types and signaling molecules are important for the progressive stages of B lymphocyte differentiation. Cells expressing CXCL12 and IL-7 have long been recognized as having essential roles in facilitating progression through stages of B lymphopoiesis. Recently, a number of other factors that extrinsically mediate B lymphopoiesis (positively or negatively) have been identified. In addition, the use of transgenic mouse models to delete specific genes in mesenchymal lineage cells has further contributed to our understanding of how B lymphopoiesis is regulated in the bone marrow. This review will cover the current understanding of B lymphocyte niches in the bone marrow and key extrinsic molecules and signaling pathways involved in these niches, with a focus on how mesenchymal lineage cells regulate B lymphopoiesis.

SLAMF receptors on normal and malignant B cells

The Signaling Lymphocyte Activation Molecule family (SLAMF) is a collection of nine surface receptors expressed mainly on hematopoietic cells, and was found to modulate the behavior of immune cells. SLAMF receptors are expressed on B cells in health and disease. Each SLAM receptor has a unique differential expression pattern during the development and activation of B cells. Furthermore, recent findings have revealed a principal role for this family of receptors in B cell malignancies, emphasizing their importance in the control of malignant cell survival, cell to cell communication within the tumor microenvironment, retention in the supporting niches and regulation of T cell anti-tumor response. This review summarizes the latest studies regarding SLAMF expression and behavior in B cells and in B cell pathologies, and discusses the therapeutic potential of these receptors.

Hypercalcemia and cancer: Differential diagnosis and treatment

Incidentally detected hypercalcemia usually presents in an indolent manner and is most likely caused by primary hyperparathyroidism. In contrast, hypercalcemia in the patient with a history of cancer presents in a wide range of clinical settings and may be severe enough to warrant hospitalization. This form of hypercalcemia is usually secondary to hypercalcemia of malignancy and can be fatal. Hypercalcemia of malignancy is most commonly mediated by tumoral production of parathyroid hormone-related protein or by cytokines activating osteoclast degradation of bone. The initial workup, differential diagnoses, confirmatory laboratory testing, imaging, and medical and surgical management of hypercalcemia are described in the patient with cancer.

A case of fatal osteolytic hypercalcemia complicated with IgG4-related ophthalmic disease leading to renal failure

A 40-year-old male was hospitalized with renal impairment and severe hypercalcemia. His concentration of serum IgG4 was high, but serum whole PTH, 1-25(OH)₂ vitamin D3 and PTHrP were not elevated. Computed tomography showed swelling of the bilateral lacrimal glands and systemic lymphadenopathy. The histological findings of lacrimal gland biopsy fulfilled the diagnostic criteria of IgG4-related ophthalmic disease (IgG4ROD). Bone scintigraphy showed increased ectopic uptake in the stomach, heart, lungs, and kidneys. He died on day 16 of admission, although the therapies for hypercalcemia were continued. Autopsy results showed an increase of osteoclasts in the bone marrow and metastatic calcification in multiple organs, and excluded from the differential diagnosis other disorders which present lymph-node swelling and hypercalcemia such as cancer, lymphoma, Castleman's disease, and sarcoidosis. He was given a diagnosis of IgG4ROD with osteolytic hypercalcemia.

Bone-targeted agents in multiple myeloma

Osteolytic bone disease, characterized by bone pain, increased risk of pathologic fractures, tumor-induced hypercalcemia known as skeletal-related events (SREs), is a frequent complication of patients with multiple myeloma (MM) and persists even in the absence of active disease, resulting in a major cause of morbidity and mortality. The interaction between myeloma cells and their surrounding cells in the bone marrow (BM) microenvironment promotes both myeloma cell growth and bone destruction and forms the vicious cycle of MM bone disease. Therefore, therapeutic strategies targeting the interaction between myeloma cells and cellular components including osteoclasts (OCs), stromal cells and osteoblasts (OBs) in the BM is crucial not only to attain tumor regression but also to prevent or delay the incidence of SREs, which leads to improve survival and quality of life in affected patients. Recently, several novel targets which act on components of the cycle for treating MM-associated bone disease have been identified in addition to current treatments including nitrogen-containing bisphosphonates. This review focuses on the overview of pathophysiology in MM-associated bone disease and summarizes its current clinical management. Several novel bone-targeted agents in preclinical setting will be also discussed.

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.

Monoclonal gammopathy of undetermined significance and bone health outcomes: a systematic review and exploratory meta-analysis

Monoclonal gammopathy of undetermined significance (MGUS) is a common condition in the elderly. A number of studies have investigated the relationship between MGUS and bone health outcomes including bone mineral density (BMD), osteoporosis and fractures, but no meta-analysis exists. We conducted a systematic review and exploratory meta-analysis comparing bone health outcomes in patients with MGUS. Two independent authors searched PubMed and Scopus from inception until 19 October 2016. A meta-analysis of cross-sectional and longitudinal studies investigating fractures and BMD was conducted. Standardised mean differences (SMD) ± 95% confidence intervals (CIs) were calculated for BMD, and risk ratios (RRs) were calculated for prevalent and incident fractures. Of 174 initial hits, 10 studies of moderate methodological quality were eligible, including 8711 individuals with MGUS vs. 52,865 controls. Compared to controls, subjects with MGUS showed significantly lower values for radial cortical volumetric BMD (1 study; SMD = -5.45, 95% CI: -7.24 to -3.66), but not at the lumbar spine, femoral neck or hip. The incidence of fractures was higher in people with MGUS (n = 7466) vs. controls (n = 52,304) (RR = 1.36, 95% CI 1.28-1.44, I ² = 0%) over a median of 12.5-year follow-up. The incidence of vertebral fractures was particularly elevated (RR = 2.50, 95% CI 1.53-4.06) although limited to two studies. In conclusion, although with limitations, our preliminary meta-analysis suggests that patients with MGUS are at higher risk of fractures despite evidence for differences in BMD being equivocal. Future longitudinal research is required to confirm our findings and determine if fracture prevention interventions are warranted in people with MGUS.

Ex vivo construction of human primary 3D-networked osteocytes

A human bone tissue model was developed by constructing ex vivo the 3D network of osteocytes via the biomimetic assembly of primary human osteoblastic cells with 20-25μm microbeads and subsequent microfluidic perfusion culture. The biomimetic assembly: (1) enabled 3D-constructed cells to form cellular network via processes with an average cell-to-cell distance of 20-25μm, and (2) inhibited cell proliferation within the interstitial confine between the microbeads while the confined cells produced extracellular matrix (ECM) to form a mechanically integrated structure. The mature osteocytic expressions of SOST and FGF23 genes became significantly higher, especially for SOST by 250 folds during 3D culture. The results validate that the bone tissue model: (1) consists of 3D cellular network of primary human osteocytes, (2) mitigates the osteoblastic differentiation and proliferation of primary osteoblast-like cells encountered in 2D culture, and (3) therefore reproduces ex vivo the phenotype of human 3D-networked osteocytes. The 3D tissue construction approach is expected to provide a clinically relevant and high-throughput means for evaluating drugs and treatments that target bone diseases with in vitro convenience.

The MIP-1α autocrine loop contributes to decreased sensitivity to anticancer drugs

Several autocrine soluble factors, including macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α, and hepatocyte growth factor, promote cell survival and growth in multiple myeloma (MM) cells. We hypothesized that inhibition of the MIP-1α autocrine loop may enhance the cytotoxic effect of anticancer drugs in MM cell lines. In the present study, an MIP-1α neutralizing antibody suppressed cell proliferation and enhanced the cytotoxic effect of melphalan or bortezomib on MM cells. In addition, melphalan resistance cells (RPMI8226/L-PAM and HS-sultan/L-PAM cells) secreted MIP-1α and neutralizing antibody of MIP-1α partially overcame melphalan resistance. Moreover, combination treatment with MIP-1α neutralizing antibody and melphalan or bortezomib inhibited extracellular signal regulated kinase 1/2 (ERK1/2), Akt, and mammalian target of rapamycin (mTOR) activation, Bcl-2, Bcl-xL, and Survivin expression, and upregulated the expression of Bim and cleaved Poly (ADP-ribose) polymerase (PARP). Treatment of IM9 cells with MIP-1α siRNA suppressed the activation of ERK1/2, Akt, and mTOR, and enhanced the cytotoxic effect of melphalan and bortezomib. These results indicate that MIP-1α neutralizing antibodies or MIP-1α siRNA enhance the cytotoxic effect of melphalan and bortezomib by suppressing the chemokine receptor/ERK and chemokine receptor/Akt/mTOR pathways. The inhibition of MIP-1α may thus provide a new therapeutic approach to control tumor progression and bone destruction in patients with MM.

A case of multiple myeloma with navicular bone involvement

Multiple myeloma is a haematological disease caused by proliferation of malignant plasma cells in bone marrow. It frequently has lytic bone lesions. However, involvement of the small bones of the hands and feet is extremely rare. We report a unique multiple myeloma patient with first recurrence in navicular bone after allogenic stem cell transplantation.

Endothelial progenitor cells in multiple myeloma neovascularization: a brick to the wall

Multiple myeloma (MM) is characterized by the clonal expansion of plasma cells in the bone marrow that leads to events such as bone destruction, anaemia and renal failure. Despite the several therapeutic options available, there is still no effective cure, and the standard survival is up to 4 years. The evolution from the asymptomatic stage of monoclonal gammopathy of undetermined significance to MM and the progression of the disease itself are related to cellular and molecular alterations in the bone marrow microenvironment, including the development of the vasculature. Post-natal vasculogenesis is characterized by the recruitment to the tumour vasculature of bone marrow progenitors, known as endothelial progenitor cells (EPCs), which incorporate newly forming blood vessels and differentiate into endothelial cells. Several processes related to EPCs, such as recruitment, mobilization, adhesion and differentiation, are tightly controlled by cells and molecules in the bone marrow microenvironment. In this review, the bone marrow microenvironment and the mechanisms associated to the development of the neovasculature promoted by EPCs are discussed in detail in both a non-pathological scenario and in MM. The latest developments in therapy targeting the vasculature and EPCs in MM are also highlighted. The identification and characterization of the pathways relevant to the complex setting of MM are of utter importance to identify not only biomarkers for an early diagnosis and disease progression monitoring, but also to reveal intervention targets for more effective therapy directed to cancer cells and the endothelial mediators relevant to neovasculature development.

Bone marrow myeloid cells in regulation of multiple myeloma progression

Survival, growth, and response to chemotherapy of cancer cells depends strongly on the interaction of cancer cells with the tumor microenvironment. In multiple myeloma, a cancer of plasma cells that localizes preferentially in the bone marrow, the microenvironment is highly enriched with myeloid cells. The majority of myeloid cells are represented by mature and immature neutrophils. The contribution of the different myeloid cell populations to tumor progression and chemoresistance in multiple myeloma is discussed.

Skeletal energy homeostasis: a paradigm of endocrine discovery

Throughout the last decade, significant developments in cellular, molecular and mouse models have revealed major endocrine functions of the skeleton. More recent studies have evolved the interplay between bone-specific hormones, the skeleton, marrow adipose tissue, muscle and the brain. This review focuses on literature from the last decade, addressing the endocrine regulation of global energy metabolism via the skeleton. In addition, we will highlight several recent studies that further our knowledge of new endocrine functions of some organs; explore remaining unanswered questions; and, finally, we will discuss future directions for this more complex era of bone biology research.

Molecular mechanisms, current management and next generation therapy in myeloma bone disease

Multiple myeloma (MM) bone disease is a major cause of morbidity and mortality in MM patients and persists even in patients in remission. This bone disease is caused by an uncoupling of bone remodeling, with increased osteoclast and decreased osteoblast activity and formation, culminating in lytic bone destruction. Bisphosphonates are the current standard of care but new therapies are needed. As the molecular mechanisms controlling MM bone disease are increasingly well understood, new therapeutic targets are extensively explored in the preclinical setting and initial clinical trials with novel compounds now show promising results. In this review, we will provide a comprehensive overview of the biology of MM bone disease, summarize its current clinical management and discuss preclinical and clinical data on next generation therapies.

Myeloma bone disease: Progress in pathogenesis

Myeloma bone disease (MBD) is one of the most serious complications of multiple myeloma (MM) and the most severe cause of MM morbidity. Dysregulation of osteoblast and osteoclast cells plays key roles in MBD. In the bone marrow microenvironment, myeloma cells, osteoblasts, osteoclasts and bone marrow stromal cells can secrete multiple cytokines, categorized as osteoclast cell activating factors (OAFs) and osteoblast cell inactivating factors, which have been discovered to participate in bone metabolism and contribute to the pathogenesis of MBD. Several signaling pathways related to these cytokines were also revealed in the MBD pathogenesis. To better understand the pathogenesis of MBD and therefore the potential therapeutic targets of this disease, we will summarize recent study progress in the factors and underlying signaling pathways involved in the occurrence and development of MBD.

Bone mineral density utilization in patients with newly diagnosed multiple myeloma

Bone disease is a major cause for morbidity in multiple myeloma (MM), with the main focus concerning the manifestation as osteolytic lesions. Bone mineral loss is another reflection of myeloma bone involvement. Recently, osteoporosis has been omitted as a defining criterion for symptomatic disease in MM. We conducted a retrospective study to evaluate the use of bone mineral density (BMD) exams by dual-energy X-ray absorptiometry (DXA) among MM patients in a tertiary medical care centre. One-hundred seventy three patients were included. The T-scores of lumbar spine (LS), left femur neck (FN) and left total hip (TH) were obtained and analysed. The extent of osteolytic disease was categorized based on six bony areas. There was a strong correlation between spine and femur's T-scores (r = 0.56-0.61, p < 0.0001), although different sets of variables were correlated with LS and femur's T-scores. There was no correlation between BMD measurements and osteolytic disease extent. Patients with vertebral fracture(s) had significant lower T-scores of the spine in comparison to patients without vertebral fractures. Sixty-three patients (36.4% of the cohort) had follow-up DXA exam. In general, there was an increase in the LS T-scores, while femoral values decreased. However, in patients who achieved complete response (CR) and in those who retained CR during follow-up, femoral BMD increased as well. Because correlation between BMD and the extent of osteolytic lesions was not seen, our data support the recent exclusion of BMD assessment from the definition of symptomatic myeloma. Still, its use should be considered for evaluation of age- or therapy-related osteoporosis. Copyright © 2016 John Wiley & Sons, Ltd.

Do Patients After Chondrosarcoma Treatment Have Age-appropriate Bone Mineral Density in the Long Term?

BACKGROUND

In long-term survivors of osteosarcoma and Ewing sarcoma treated with the addition of radio- and chemotherapy, low bone mineral density (BMD) and fractures have been observed, presumably resulting from these adjuvants. Because patients with chondrosarcoma usually are not treated with conventional adjuvant treatment, observation of low BMD in patients with chondrosarcoma presumably would be the result of other mechanisms. However, BMD in patients with a history of chondrosarcoma has not been well characterized.

QUESTIONS/PURPOSES

The aim of our study was to address the following questions: (1) Do long-term survivors of chondrosarcoma have normal BMD and, if not, which factors contribute to low BMD? (2) Is there a greater risk of fracture and does the Fracture Risk Assessment Tool (FRAX(®)) score reflect fracture likelihood?

METHODS

All known patients with a history of chondrosarcoma treated at our institution before 2006 were identified. Of 127 patients believed to be alive at the time of this study, 30 agreed to participate in this study (11 females, 19 males; mean age at surgery, 39 ± 12 years; mean followup, 12 ± 5 years). With the data available, the 30 participants were not different from the 97 nonparticipants in terms of age, sex, BMI, tumor grade, tumor location (axial versus appendicular, lower extremity versus elsewhere), and use of any treatment known to influence osteopenia (chemotherapy, lower extremity surgery). BMD was measured and history of fractures was assessed using a questionnaire. The patients´ BMD measurements in this study were sex- and age-matched with a normative sex- and age-categorized reference population reported by Kudlacek et al. Associations were tested by univariate regressions and ANOVAs of all measures of BMD and eligible oncologic and demographic factors.

RESULTS

Eighteen of 30 (60%) patients had a pathologic BMD according to the WHO dual-energy x-ray absorptiometry definition, 15 (50%) had osteopenia, and three (10%) had osteoporosis. T-scores in the study cohort were lower than reference values for the femur neck (mean difference, 0.64; 95% CI, 0.27-1.01; p < 0.0015), but not for the spine (mean difference, 0.39; 95% CI, -0.06 to 0.84; p = 0.09). Thirteen patients (45%) reported a history of fractures not distinguishing between low and high impact. The incidence of fractures was 2.8 greater than expected from a comparison with a published microcensus survey of the Austrian population. No effect of the FRAX(®) score on fracture risk could be identified (p = 0.057).

CONCLUSIONS

Long-term survivors of chondrosarcoma appear to be at greater risk for having low BMD develop than the healthy population. Although these results are preliminary and based on a very small sampling of patients, if they can be confirmed in larger studies, BMD assessment by dual-energy x-ray absorptiometry might be considered as these patients are followed posttreatment by sarcoma care units. The reasons for low BMD still must be elucidated.

LEVEL OF EVIDENCE

Level IV, prognostic study.

Bone pain: current and future treatments

Skeletal conditions are common causes of chronic pain and there is an unmet medical need for improved treatment options. Bone pain is currently managed with disease modifying agents and/or analgesics depending on the condition. Disease modifying agents affect the underlying pathophysiology of the disease and reduce as a secondary effect bone pain. Antiresorptive and anabolic agents, such as bisphosphonates and intermittent parathyroid hormone (1-34), respectively, have proven effective as pain relieving agents. Cathepsin K inhibitors and anti-sclerostin antibodies hold, due to their disease modifying effects, promise of a pain relieving effect. NSAIDs and opioids are widely employed in the treatment of bone pain. However, recent preclinical findings demonstrating a unique neuronal innervation of bone tissue and sprouting of sensory nerve fibers open for new treatment possibilities.

Hypercalcemia. Pathophysiological Aspects

The metabolic pathways that contribute to maintain serum calcium concentration in narrow physiological range include the bone remodeling process, intestinal absorption and renal tubule resorption. Dysbalance in these regulations may lead to hyper- or hypocalcemia. Hypercalcemia is a potentionally life-threatening and relatively common clinical problem, which is mostly associated with hyperparathyroidism and/or malignant diseases (90 %). Scarce causes of hypercalcemia involve renal failure, kidney transplantation, endocrinopathies, granulomatous diseases, and the long-term treatment with some pharmaceuticals (vitamin D, retinoic acid, lithium). Genetic causes of hypercalcemia involve familial hypocalciuric hypercalcemia associated with an inactivation mutation in the calcium sensing receptor gene and/or a mutation in the CYP24A1 gene. Furthermore, hypercalcemia accompanying primary hyperparathyroidism, which develops as part of multiple endocrine neoplasia (MEN1 and MEN2), is also genetically determined. In this review mechanisms of hypercalcemia are discussed. The objective of this article is a review of hypercalcemia obtained from a Medline bibliographic search.

Osteolytica: An automated image analysis software package that rapidly measures cancer-induced osteolytic lesions in in vivo models with greater reproducibility compared to other commonly used methods

Methods currently used to analyse osteolytic lesions caused by malignancies such as multiple myeloma and metastatic breast cancer vary from basic 2-D X-ray analysis to 2-D images of micro-CT datasets analysed with non-specialised image software such as ImageJ. However, these methods have significant limitations. They do not capture 3-D data, they are time-consuming and they often suffer from inter-user variability. We therefore sought to develop a rapid and reproducible method to analyse 3-D osteolytic lesions in mice with cancer-induced bone disease. To this end, we have developed Osteolytica, an image analysis software method featuring an easy to use, step-by-step interface to measure lytic bone lesions. Osteolytica utilises novel graphics card acceleration (parallel computing) and 3-D rendering to provide rapid reconstruction and analysis of osteolytic lesions. To evaluate the use of Osteolytica we analysed tibial micro-CT datasets from murine models of cancer-induced bone disease and compared the results to those obtained using a standard ImageJ analysis method. Firstly, to assess inter-user variability we deployed four independent researchers to analyse tibial datasets from the U266-NSG murine model of myeloma. Using ImageJ, inter-user variability between the bones was substantial (±19.6%), in contrast to using Osteolytica, which demonstrated minimal variability (±0.5%). Secondly, tibial datasets from U266-bearing NSG mice or BALB/c mice injected with the metastatic breast cancer cell line 4T1 were compared to tibial datasets from aged and sex-matched non-tumour control mice. Analyses by both Osteolytica and ImageJ showed significant increases in bone lesion area in tumour-bearing mice compared to control mice. These results confirm that Osteolytica performs as well as the current 2-D ImageJ osteolytic lesion analysis method. However, Osteolytica is advantageous in that it analyses over the entirety of the bone volume (as opposed to selected 2-D images), it is a more rapid method and it has less user variability.

Denosumab: a new agent in the management of hypercalcemia of malignancy

Hypercalcemia of malignancy is an oncologic emergency due to tumoral factors that stimulate osteoclast-mediated bone resorption. It requires a combination of recommended treatments (i.e., hydration, bisphosphonate and calcitonin), which may be deleterious in patients with compromised cardiac or renal function or may not control serum calcium levels long term. Recurrent or refractory hypercalcemia may preclude the use of chemotherapeutic agents needed to effectively treat the underlying cancer, which is the cause of hypercalcemia. Denosumab, a fully human monoclonal antibody against RANKL, inhibits the maturation, function and survival of osteoclasts. An open-label, single-arm study of denosumab in patients with hypercalcemia of malignancy despite recent bisphosphonate treatment revealed positive results. Thus, the US FDA recently approved denosumab for the indication of hypercalcemia of malignancy, increasing the options available for patients with this debilitating and life-threatening condition.

Dynamic interplay between bone and multiple myeloma: emerging roles of the osteoblast

Multiple myeloma is a B-cell malignancy characterized by the unrelenting proliferation of plasma cells. Multiple myeloma causes osteolytic lesions and fractures that do not heal due to decreased osteoblastic and increased osteoclastic activity. However, the exact relationship between osteoblasts and myeloma cells remains elusive. Understanding the interactions between these dynamic bone-forming cells and myeloma cells is crucial to understanding how osteolytic lesions form and persist and how tumors grow within the bone marrow. This review provides a comprehensive overview of basic and translational research focused on the role of osteoblasts in multiple myeloma progression and their relationship to osteolytic lesions. Importantly, current challenges for in vitro studies exploring direct osteoblastic effects on myeloma cells, and gaps in understanding the role of the osteoblast in myeloma progression are delineated. Finally, successes and challenges in myeloma treatment with osteoanabolic therapy (i.e., any treatment that induces increased osteoblastic number or activity) are enumerated. Our goal is to illuminate novel mechanisms by which osteoblasts may contribute to multiple myeloma disease progression and osteolysis to better direct research efforts. Ultimately, we hope this may provide a roadmap for new approaches to the pathogenesis and treatment of multiple myeloma with a particular focus on the osteoblast.

Hemin activation of innate cellular response blocks human immunodeficiency virus type-1-induced osteoclastogenesis

The normal skeletal developmental and homeostatic process termed osteoclastogenesis is exacerbated in numerous pathological conditions and causes excess bone loss. In cancer and HIV-1-infected patients, this disruption of homeostasis results in osteopenia and eventual osteoporesis. Counteracting the factors responsible for these metabolic disorders remains a challenge for preventing or minimizing this co-morbidity associated with these diseases. In this report, we demonstrate that a hemin-induced host protection mechanism not only suppresses HIV-1 associated osteoclastogenesis, but it also exhibits anti-osteoclastogenic activity for non-infected cells. Since the mode of action of hemin is both physiological and pharmacological through induction of heme oxygenase-1 (HO-1), an endogenous host protective response to an FDA-licensed therapeutic used to treat another disease, our study suggests an approach to developing novel, safe and effective therapeutic strategies for treating bone disorders, because hemin administration in humans has previously met required FDA safety standards.