Myeloma Bone Disease: Update on Pathogenesis and Novel Treatment Strategies

Mixed-Methods Study of End-of-Life Experiences of Patients With Hematologic Malignancies in Social Hospice Residential Home Care Settings

PURPOSE

Hospice is underutilized by patients with hematologic malignancies (HM), and when patients are referred, they are typically more ill, hospitalized, and with shorter length of stay (LOS) than patients with solid tumors (ST), limiting research about home hospice care experiences of patients with HM. In this mixed-methods study, we examined the hospice experiences of patients with HM who died at residential care homes (RCHs), home-based settings in which volunteer caregivers and hospice staff provide end-of-life (EOL) care under the social hospice model.

METHODS

We queried a registry of 535 hospice patients who died at RCHs between 2005 and 2020 that included quantitative medication administration data as well as qualitative data from hospice intake forms and written volunteer caregiver narratives. Qualitative data were analyzed by collective case study methodology. Quantitative comparisons of LOS and liquid morphine use were performed with matched patients with ST.

RESULTS

The registry yielded 29 patients with HM, of whom qualitative data were available for 18 patients. Patients with HM exhibited common EOL symptoms (pain, dyspnea, and agitation). Instances of bleeding were low (22%), and notable HM-specific care concerns were described regarding bone fractures, skin integrity, and delirium. Most (78%) experienced good symptom management and peaceful or comfortable deaths. In only one case were symptoms described as severe and poorly managed. Patients with HM had comparable LOS on hospice and at the RCHs to patients with ST, with no group differences in liquid morphine use.

CONCLUSION

In this registry cohort, most patients with HM achieved good symptom management in home care settings with volunteer caregivers and hospice support. Caregivers may require additional counseling and palliative medications for HM-specific EOL symptoms.

Transcription of WNT Genes in Hematopoietic Niche's Mesenchymal Stem Cells in Multiple Myeloma Patients with Different Responses to Treatment

Mesenchymal stromal cells (MSCs) are involved in bone tissue remodeling due to their ability to differentiate into osteoblasts and to influence osteoclasts' activity. Multiple myeloma (MM) is associated with bone resorption. During disease progression, MSCs acquire a tumor-associated phenotype, losing their osteogenic potential. The process is associated with impaired osteoblasts/osteoclasts balance. The WNT signaling pathway plays a major role in maintaining the balance. In MM, it functions in an aberrant way. It is not known yet whether the WNT pathway is restored in patients' bone narrow after treatment. The aim of the study was to compare the level of WNT family gene transcription in the bone marrow MSCs of healthy donors and MM patients before and after therapy. The study included healthy donors (n = 3), primary patients (n = 3) and patients with different response status to therapy (bortezomib-containing induction regimens) (n = 12). The transcription of the WNT and CTNNB1 (encoding β-catenin) genes was accessed using qPCR. The mRNA quantity of ten WNT genes, as well as CTNNB1 mRNA encoding β-catenin, a key mediator in canonical signaling, was evaluated. The observed differences between the groups of patients indicated that aberrant functioning of the WNT pathway was retained after treatment. The differences that we detected for WNT2B, WNT9B and CTNNB1 suggested their possible application as prognostic molecular markers.

Risk-benefit ratio of percutaneous kyphoplasty and percutaneous vertebroplasty in patients with newly diagnosed multiple myeloma with vertebral fracture: a single-center retrospective study

The indications for percutaneous kyphoplasty (PKP) and percutaneous vertebroplasty (PVP) are painful vertebral compression fractures. Our study is to assess the risk-benefit ratio of PKP/PVP surgery in the patients with newly diagnosed multiple myeloma (NDMM) without receiving antimyeloma therapy. The clinical data of 426 consecutive patients with NDMM admitted to our center from February 2012 to April 2022 were retrospectively analyzed. The baseline data, postoperative pain relief, the proportion of recurrent vertebral fractures, and survival time were compared between the PKP/PVP surgical group and the nonsurgical group in the NDMM patients. Of the 426 patients with NDMM, 206 patients had vertebral fractures (206/426, 48.4%). Of these, 32 (32/206, 15.5%) underwent PKP/PVP surgery for misdiagnosis of simple osteoporosis prior to diagnosis of MM (surgical group), and the other 174 (174/206, 84.5%) did not undergo surgical treatment prior to definitive diagnosis of MM (non-surgical group). The median age of patients in the surgical and nonsurgical groups was 66 and 62 years, respectively (p = 0.01). The proportion of patients with advanced ISS and RISS stages was higher in the surgical group (ISS stage II + III 96.9% vs. 71.8%, p = 0.03; RISS stage III 96.9% vs. 71%, p = 0.01). Postoperatively, 10 patients (31.3%) never experienced pain relief and 20 patients (62.5%) experienced short-term pain relief with a median duration of relief of 2.6 months (0.2-24.1 months). Postoperative fractures of vertebrae other than the surgical site occurred in 24 patients (75%) in the surgical group, with a median time of 4.4 months postoperatively (0.4-86.8 months). Vertebral fractures other than the fracture site at the first visit occurred in 5 patients (2.9%) in the nonoperative group at the time of diagnosis of MM, with a median time of 11.9 months after the first visit (3.5-12.6 months). The incidence of secondary fractures was significantly higher in the surgical group than in the nonsurgical group (75% vs. 2.9%, p = 0.001). The time interval between the first visit and definitive diagnosis of MM was longer in the surgical group than in the nonsurgical group (6.1 months vs. 1.6 months, p = 0.01). At a median follow-up of 32 months (0.3-123 months), median overall survival (OS) was significantly shorter in the surgical group than in the nonsurgical group (48.2 months vs. 66 months, p = 0.04). Application of PKP/PVP surgery for pain relief in NDMM patients without antimyeloma therapy has a limited effect and a high risk of new vertebral fractures after surgery. Therefore, patients with NDMM may need to have their disease controlled with antimyeloma therapy prior to any consideration for PKP/PVP surgery.

In vivo antitumor efficacy of 17-AAG loaded PMMA in a human multiple myeloma xenograft mouse model

Multiple myeloma (MM) is a monoclonal malignancy characterized by abnormal proliferation of plasma cells. The disease clinically manifests as anemia, hypercalcemia, renal insufficiencies, and osteolytic damage. Osteolytic damage goes with severe bone pain, spinal instability, and pathological fracture, symptoms that are collectively referred to as multiple myeloma bone disease (MMBD). Polymethylmethacrylate (PMMA) bone cement is widely used for bone repair after MMBD surgery, owing to its excellent biomechanical properties and fast curing. To date, however, efficacy of drug-loading PMMA in inhibition of tumor growth and angiogenesis remains unknown. Here, we report that 17-AAG-loaded PMMA bone cement inhibits MM growth in vivo and suppresses tumor diffusion to peripheral tissues. In addition, 17-AAG-loaded PMMA promotes MM apoptosis by downregulating Bax and active Caspase-3.

Circular RNA in multiple myeloma: A new target for therapeutic intervention

Circular RNAs (circRNAs) are RNA molecules with a stable closed-loop structure that are found in a variety of organisms. CircRNAs are highly stable and conserved, and they play important roles in transcriptional regulation and splicing. Multiple Myeloma (MM) is a malignant proliferative disease for which there are currently no effective and comprehensive treatments. Numerous circRNAs may contribute to the development and progression of MM by acting as oncogenes or regulators. Due to the unique function of circRNAs, they have a high potential for regulating the biological functions (including proliferation and apoptosis) of MM cells, and their expression levels and molecular mechanism are closely related to their diagnostic value, therapeutic sensitivity, and clinical prognosis of MM patients. In this review, we aim to provide a detailed overview of the structure and function of circRNAs and demonstrate the potential therapeutic value and potential mechanism of circRNAs in MM via experiments and clinical trials.

Secondary Osteoporosis

Osteoporosis is a global public health problem, with fractures contributing to significant morbidity and mortality. Although postmenopausal osteoporosis is most common, up to 30% of postmenopausal women, > 50% of premenopausal women, and between 50% and 80% of men have secondary osteoporosis. Exclusion of secondary causes is important, as treatment of such patients often commences by treating the underlying condition. These are varied but often neglected, ranging from endocrine to chronic inflammatory and genetic conditions. General screening is recommended for all patients with osteoporosis, with advanced investigations reserved for premenopausal women and men aged < 50 years, for older patients in whom classical risk factors for osteoporosis are absent, and for all patients with the lowest bone mass (Z-score ≤ -2). The response of secondary osteoporosis to conventional anti-osteoporosis therapy may be inadequate if the underlying condition is unrecognized and untreated. Bone densitometry, using dual-energy x-ray absorptiometry, may underestimate fracture risk in some chronic diseases, including glucocorticoid-induced osteoporosis, type 2 diabetes, and obesity, and may overestimate fracture risk in others (eg, Turner syndrome). FRAX and trabecular bone score may provide additional information regarding fracture risk in secondary osteoporosis, but their use is limited to adults aged ≥ 40 years and ≥ 50 years, respectively. In addition, FRAX requires adjustment in some chronic conditions, such as glucocorticoid use, type 2 diabetes, and HIV. In most conditions, evidence for antiresorptive or anabolic therapy is limited to increases in bone mass. Current osteoporosis management guidelines also neglect secondary osteoporosis and these existing evidence gaps are discussed.

A functional three-dimensional microphysiological human model of myeloma bone disease

Human myeloma bone disease (MBD) occurs when malignant plasma cells migrate to the bone marrow and commence inimical interactions with stromal cells, disrupting the skeletal remodeling process. The myeloma cells simultaneously suppress osteoblastic bone formation while promoting excessive osteoclastic resorption. This bone metabolism imbalance produces osteolytic lesions that cause chronic bone pain and reduce trabecular and cortical bone structural integrity, and often culminate in pathological fractures. Few bone models exist that enable scientists to study MBD and the effect therapies have on restoring the bone metabolism imbalance. The purpose of this research was to develop a well characterized three-dimensional (3D) bone organoid that could be used to study MBD and current or potential treatment options. First, bone marrow stromal cell-derived osteoblasts (OBs) mineralized an endosteal-like extracellular matrix (ECM) over 21 days. Multiple analyses confirmed the generation of hydroxyapatite (HA)-rich bone-like tissue fragments that were abundant in alkaline phosphatase, calcium, and markers of osteoblastic gene expression. On day 22, bone marrow macrophage (BMM)-derived osteoclasts (OCs) were introduced to enhance the resorptive capability of the model and recapitulate the balanced homeostatic nature of skeletal remodeling. Tartrate-resistant acid phosphatase 5b (TRAcP-5b), type I collagen C-telopeptide (CTX-1), and gene expression analysis confirmed OC activity in the normal 3D organoid (3D in vitro model of normal bonelike fragments [3D-NBF]). On day 30, a human multiple myeloma (MM)-derived plasmacytoma cell line was introduced to the 3D-NBF to generate the 3D-myeloma bone disease organoid (3D-MBD). After 12 days, the 3D-MBD had significantly reduced total HA, increased TRAcP-5b levels, increases levels of CTX-1, and decreased expression of osteoblastic genes. Therapeutic intervention with pharmaceutical agents including an immunomodulatory drug, a bisphosphonate, and monoclonal restored HA content and reduced free CTX-1 in a dose-dependent manner. This osteogenically functional model of MBD provides a novel tool to study biological mechanisms guiding the disease and to screen potential therapeutics. © 2021 American Society for Bone and Mineral Research (ASBMR).

The role of bone-modifying agents in myeloma bone disease

Bone disease is common in patients with multiple myeloma (MM), which manifests as bone pain and skeletal-related events (SREs) such as pathological fractures and spinal cord compression. Myeloma bone disease (MBD) can adversely affect the quality of life of patients and have negative effects on morbidity and mortality. The pathogenesis of MBD is complex, and several factors are involved in the dysregulation of bone metabolism and uncoupling of bone remodeling, which result in net bone loss and devastating SREs. Broadly speaking, elevated osteoclast activity, suppressed osteoblast activity, and an aberrant marrow microenvironment play a role in MBD. Interaction of MM cells with the main bone cell osteocytes also promote further bone destruction. This review focuses on the role of bone-modifying agents in the prevention and treatment of MBD. The mainstay of MBD prevention are antiresorptive agents, bisphosphonates and denosumab. However, these agents do not play a direct role in bone formation and repair of existing MBD. Newer agents with anabolic effects such as anti-sclerostin antibodies, parathyroid hormone, anti-Dickkopf-1 antibodies, and others have shown potential in repair of MBD lesions. With the development of several new agents, the treatment landscape of MBD is likely to evolve in the coming years. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Management of Myeloma Bone Lesions

Multiple myeloma (MM) is a B-cell neoplasm characterized by clonal plasma-cell proliferation. The survival and prognosis of this condition have been significantly improved by treatment with active anti-MM drugs such as bortezomib or lenalidomide. Further, the discovery of novel agents has recently paved the way for new areas of investigation. However, MM, including myeloma-related bone diseases, remains fatal. Bone disease or bone destruction in MM is a consequence of skeletal involvement with bone pain, spinal cord compression, and bone fracture resulting from osteolytic lesions. These consequences affect disease outcomes, including patients' quality of life and survival. Several studies have sought to better understand MM bone disease (MBD) through the classification of its molecular mechanisms, including osteoclast activation and osteoblast inhibition. Bisphosphonates and the receptor activator of the nuclear factor-kappa B (NF-κB) ligand (RANKL) inhibitor, denosumab, prevent skeletal-related events in MM. In addition, several other bone-targeting agents, including bone-anabolic drugs, are currently used in preclinical and early clinical evaluations. This review summarizes the current knowledge of the pathogenesis of MBD and discusses novel agents that appear very promising and will soon enter clinical development.

The status of jaw lesions and medication-related osteonecrosis of jaw in patients with multiple myeloma

BACKGROUND/PURPOSE

Myeloma jaw lesions are not uncommon. The study aimed to investigate the status of jaw lesions and medication-related osteonecrosis of jaw (MRONJ) in multiple myeloma (MM) patients.

METHODS

One hundred and twenty-two consecutive newly-diagnosed MM patients seeking dental care at a hospital of southern Taiwan was examined according to jaw lesions with complete follow-up data.

RESULTS

Median age of the patients was 67.8 years, and 88.5% of patients were of DS stage III and 41.0% were of ISS stage III at diagnosis. Median survival was 37.9 months for 43 (35.2%) patients with jaw lesions and 57.4 months for 79 patients without jaw lesions. 1-year, 5-year and >7-year overall survival rates for patients with jaw lesions versus patients without jaw lesions were 94.9%, 67.2%, 56.7% vs 83.7%, 51.8%, 26.8% respectively. Patients with jaw lesions had the worse survival (P = 0.03). Neither age nor stage affected survival. Jaw lesions involved the mandible more often than the maxilla and stopped progressing during remission, but did not repair. Jaw lesions were the first evidence or recurrent sign of MM in six (4.9%) patients. Long-term monthly antiresorptive therapy changed the radiographic patterns of jawbones and induced MRONJ developing in 16.7% (8/48) of patients. Five (62.5%) MRONJ sites spontaneously occurred without local risk factors.

CONCLUSION

Nearly one-third of MM patients develop osteolytic jaw lesions that seem to be associated with poorer survival. Jaw lesion is an independent prognostic predictor of survival in myeloma. Antiresorptive drugs at less frequent dosing regimen are crucial to minimize spontaneous MRONJ.

Everyday living with pain - reported by patients with multiple myeloma

OBJECTIVES

The prevalence and impact of pain among patients with multiple myeloma (MM) in their everyday life require renewed attention. MM patients' survival has increased considerably over the last decades and active disease episodes are interrupted by longer periods with disease inactivity. The aim with this study is to explore pain intensity and pain interference with daily activities during periods of stable or inactive MM disease.

METHODS

In a cross-sectional study from September 2017 to May 2019, self-reliant MM patients in stable disease filled a comprehensive selection of validated questionnaires regarding pain, other symptoms and quality of life, which they experienced in their daily living. Patient reported pain intensity and interference with daily activities were analyzed for associations with several clinical and demographic factors and discussed from a total pain perspective. The two outcomes, pain intensity and pain interfering with daily activities, were analyzed in two age groups (<65 years or ≥65 years).

RESULTS

Among 92 participants, 80% experienced pain to interfere with their daily activities (equal in both age groups), and 63% reported moderate to severe pain intensity; (75% ≥65 years, and 49% <65 years). Pain intensity was significantly associated with signs of depression (OR 4.0 [95% CI: 1.2-13.9]) and age ≥65 years (OR 3.3 [95% CI: 1.2-9.2]). Pain interfering with daily activities was nearly significantly associated with bone involvement (OR 3.4 [95% CI: 1.0-11.6]) and signs of depression (OR 5.9 [95% CI: 1.0-36.3]). The patients were bothered with many problems in addition to pain; fatigue (91%), bone involvement (74%), signs of depression (41%), signs of anxiety (32%), comorbidity (29%) and uncertainty in relation to employment or pension (25%). Neuropathic pain was more prevalent in the feet (33% [95% CI: 23%, 43%]) compared with pain in the hands (13% [95% CI: 7%, 22%]).

CONCLUSIONS

In periods of stable disease, many MM patients continue to live with intense pain interfering with their daily activities. Additional or associated problems are the presence of bone involvement, neuropathic pain, older age, uncertainty in relation to employment or pension, comorbidity, signs of depression, anxiety and fatigue. This highlights the importance of health professionals being receptive to the patients' experience of pain throughout their trajectories, to assess pain systematically and to interpret this experience from a total pain perspective. While pain problems in relation to diagnosing and treating MM is well known, this study brings the message that even during periods of stable or inactive MM disease, the patients experience pain with a moderate to severe intensity, that interferes with their everyday living. The improved survival and the consequential long trajectories make coherence in the pain treatment even more important for the patients, who may see different professionals in different health care settings for different reasons. The patient group requires a coordinated, holistic patient-centered pain treatment throughout the disease trajectory.

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

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

Pathogenic Mechanisms of Myeloma Bone Disease and Possible Roles for NRF2

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

Multiple Myeloma Associated Bone Disease

The lytic bone disease is a hallmark of multiple myeloma, being present in about 80% of patients with newly diagnosed MM, and in more during the disease course. The myeloma associated bone disease (MBD) severely affects the morbidity and quality of life of the patients. MBD defines treatment demanding MM. In recent years, knowledge of the underlying pathophysiology has increased, and novel imaging technologies, medical and non-pharmaceutical treatments have improved. In this review, we highlight the major achievements in understanding, diagnosing and treating MBD. For diagnosing MBD, low-dose whole-body CT is now recommended over conventional skeletal survey, but also more advanced functional imaging modalities, such as diffusion-weighted MRI and PET/CT are increasingly important in the assessment and monitoring of MBD. Bisphosphonates have, for many years, played a key role in management of MBD, but denosumab is now an alternative to bisphosphonates, especially in patients with renal impairment. Radiotherapy is used for uncontrolled pain, for impeding fractures and in treatment of impeding or symptomatic spinal cord compression. Cement augmentation has been shown to reduce pain from vertebral compression fractures. Cautious exercise programs are safe and feasible and may have the potential to improve the status of patients with MM.

The effective role of sodium copper chlorophyllin on the dysfunction of bone marrow mesenchymal stem cells in multiple myeloma via regulating TGF-β1

BACKGROUND

The osteoblast differentiation of bone marrow-derived stem cells (BMSCs) is impaired in multiple myeloma (MM). We investigated the effects of sodium copper chlorophyllin (SCC) on osteoblast differentiation ability of BMSCs from MM.

METHODS

Clinical bone marrow samples were collected. Fluorescence Activated Cell Sorter (FACS) was used to identify surface markers of BMSCs. BMSCs were treated with different concentrations of SCC and cell viability was detected by MTT assay. Relative mRNA and protein expressions of transforming growth factor-β1 (TGF-β1), SMAD2/3, osteogenic differentiation indicators (RUNX2 and OCN) were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Alkaline phosphatase (ALP) was stained for activity detection. Formation of calcium nodus of BMSCs was examined by Alizarin Red S staining.

RESULTS

CD90 and CD105 were high-expressed, but CD34 and CD45 were not expressed in BMSCs. BMSCs in MM group showed a lower expression of TGF-β1 and a lower degree of osteogenic differentiation. SCC enhanced activities of BMSCs, ALP activity, and formation of calcium nodus, activated TGF-β1, SMAD2/3 pathway and increased RUNX2 and OCN expressions in BMSCs. Silencing TGF-β1 reversed the effects of SCC on BMSCs in MM.

CONCLUSION

SCC could effectively improve the proliferation and osteogenic differentiation of BMSCs in MM through regulating TGF-β1.

Identification of MicroRNAs With In Vivo Efficacy in Multiple Myeloma-related Xenograft Models

BACKGROUND/AIM

Multiple myeloma is a B-cell neoplasm, which can spread within the marrow of the bones forming many small tumors. In advanced disease, multiple myeloma can spread to the blood as plasma cell leukemia. In some cases, a localized tumor known as plasmacytoma is found within a single bone. Despite the approval of several agents such as melphalan, corticosteroids, proteasome inhibitors, thalidomide-based immuno-modulatory agents, histone deacetylase inhibitors, a nuclear export inhibitor and monoclonal antibodies daratuzumab and elatuzumab, the disease presently remains uncurable.

MATERIALS AND METHODS

In order to define new targets and treatment modalities we searched the literature for microRNAs, which increase or inhibit in vivo efficacy in multiple-myeloma-related xenograft models.

RESULTS AND CONCLUSION

We identified six up-regulated and twelve down-regulated miRs, which deserve further preclinical validation.

Myeloma cells shift osteoblastogenesis to adipogenesis by inhibiting the ubiquitin ligase MURF1 in mesenchymal stem cells

The suppression of bone formation is a hallmark of multiple myeloma. Myeloma cells inhibit osteoblastogenesis from mesenchymal stem cells (MSCs), which can also differentiate into adipocytes. We investigated myeloma-MSC interactions and the effects of such interactions on the differentiation of MSCs into adipocytes or osteoblasts using single-cell RNA sequencing, in vitro coculture, and subcutaneous injection of MSCs and myeloma cells into mice. Our results revealed that the α₄ integrin subunit on myeloma cells stimulated vascular cell adhesion molecule-1 (VCAM1) on MSCs, leading to the activation of protein kinase C β1 (PKCβ1) signaling and repression of the muscle ring-finger protein-1 (MURF1)-mediated ubiquitylation of peroxisome proliferator-activated receptor γ2 (PPARγ2). Stabilized PPARγ2 proteins enhanced adipogenesis and consequently reduced osteoblastogenesis from MSCs, thus suppressing bone formation in vitro and in vivo. These findings reveal that suppressed bone formation is a direct consequence of myeloma-MSC contact that promotes the differentiation of MSCs into adipocytes at the expense of osteoblasts. Thus, this study provides a potential strategy for treating bone resorption in patients with myeloma by counteracting tumor-MSC interactions.

Hematological Diseases and Osteoporosis

Secondary osteoporosis is a common clinical problem faced by bone specialists, with a higher frequency in men than in women. One of several causes of secondary osteoporosis is hematological disease. There are numerous hematological diseases that can have a deleterious impact on bone health. In the literature, there is an abundance of evidence of bone involvement in patients affected by multiple myeloma, systemic mastocytosis, thalassemia, and hemophilia; some skeletal disorders are also reported in sickle cell disease. Recently, monoclonal gammopathy of undetermined significance appears to increase fracture risk, predominantly in male subjects. The pathogenetic mechanisms responsible for these bone loss effects have not yet been completely clarified. Many soluble factors, in particular cytokines that regulate bone metabolism, appear to play an important role. An integrated approach to these hematological diseases, with the help of a bone specialist, could reduce the bone fracture rate and improve the quality of life of these patients.

Harnessing the versatile role of OPG in bone oncology: counterbalancing RANKL and TRAIL signaling and beyond

More than 2 decades ago, the discovery of osteoprotegerin (OPG) as inhibitor of the receptor of activator of nuclear factor Kb (RANK) ligand (RANKL) revolutionized our understanding of bone biology and oncology. Besides acting as decoy receptor for RANKL, OPG acts as decoy receptor for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). OPG, RANKL, and TRAIL are ubiquitously expressed, stimulating per se pivotal signaling cascades implicated in cancer. In the context of cancer cell-bone cell interactions, cancer cells skew the OPG/RANKL/RANK (RANKL cognate receptor) balance towards bone destruction and tumor growth through favoring the RANKL/RANK interface, circumventing OPG. Numerous preclinical and clinical studies demonstrate the dual role of OPG in cancer: antitumor and tumor-promoting. OPG potentially conveys an antitumor signal through inhibiting the tumor-promoting RANKL signaling-both the osteoclast-dependent and the osteoclast-independent-and the tumor-promoting TRAIL signaling. On the other hand, the presumed tumor-promoting functions of OPG are: (i) abrogation of TRAIL-induced apoptosis of cancer cells; (ii) abrogation of RANKL-induced antitumor immunity; and (iii) stimulation of oncogenic and prometastatic signaling cascades downstream of the interaction of OPG with diverse proteins. The present review dissects the role of OPG in bone oncology. It presents the available preclinical and clinical data sustaining the dual role of OPG in cancer and focuses on the imbalanced RANKL/RANK/OPG interplay in the landmark "vicious cycle" of skeletal metastatic disease, osteosarcoma, and multiple myeloma. Finally, current challenges and future perspectives in exploiting OPG signaling in bone oncology therapeutics are discussed.

Osteocyte-Mediated Translation of Mechanical Stimuli to Cellular Signaling and Its Role in Bone and Non-bone-Related Clinical Complications

PURPOSE OF REVIEW

Osteocytes comprise > 95% of the cellular component in bone tissue and produce a wide range of cytokines and cellular signaling molecules in response to mechanical stimuli. In this review, we aimed to summarize the molecular mechanisms involved in the osteocyte-mediated translation of mechanical stimuli to cellular signaling, and discuss their role in skeletal (bone) diseases and extra-skeletal (non-bone) clinical complications.

RECENT FINDINGS

Two decades before, osteocytes were assumed as a dormant cells buried in bone matrix. In recent years, emerging evidences have shown that osteocytes are pivotal not only for bone homeostasis but also for vital organ functions such as muscle, kidney, and heart. Osteocyte mechanotransduction regulates osteoblast and osteoclast function and maintains bone homeostasis. Mechanical stimuli modulate the release of osteocyte-derived cytokines, signaling molecules, and extracellular cellular vesicles that regulate not only the surrounding bone cell function and bone homeostasis but also the distant organ function in a paracrine and endocrine fashion. Mechanical loading and unloading modulate the osteocytic release of NO, PGE₂, and ATPs that regulates multiple cellular signaling such as Wnt/β-catenin, RANKL/OPG, BMPs, PTH, IGF1, VEGF, sclerostin, and others. Therefore, the in-depth study of the molecular mechanism of osteocyte mechanotransduction could unravel therapeutic targets for various bone and non-bone-related clinical complications such as osteoporosis, sarcopenia, and cancer metastasis to bone.

Persistent Increase in Serum Alkaline Phosphatase in a Patient with Monoclonal Gammopathy of Undefined Significance

We report the finding of alkaline phosphatase-immunoglobulin complex (macro-alkaline phosphatase (macro-ALP)) in a patient with persistently increased ALP activity. The identification of macro-ALP is important to rule out pathological causes of increased ALP activity and to avoid unnecessary diagnostic investigation. The patient was subsequently diagnosed with vitamin D deficiency, gallstone pancreatitis, and monoclonal gammopathy of undefined significance (MGUS). Macro-ALP can coexist with disease that can increase serum ALP activity. We report, for the first time, a case of macro-ALP in a patient with a monoclonal protein (M-protein).

Bisphosphonates-much more than only drugs for bone diseases

α,α-Bisphosphonates (BPs) are well established in the treatment of bone diseases such as osteoporosis and Paget's disease. Their successful application originates from their high affinity to hydroxyapatite. While the initially appreciated features of BPs are already beneficial to many patients, recent developments have further expanded their pleiotropic applications. This review describes the background of the interactions of BPs with bone cells that form the basis of the classical treatment. A better understanding of the mechanism behind their interactions allows for the parallel application of BPs against bone cancer and metastases followed by palliative pain relief. Targeted therapy with bone-seeking BPs coupled with a diagnostic agent in one particle resulted in theranostics which is also described here. For example, in such a system, BP moieties are bound to contrast agents used in magnetic resonance imaging or radionuclides used in positron emission tomography. In addition, another example of the pleiotropic function of BPs which involves targeting the imaging agents to bone tissues accompanied by pain reduction is presented in this work.

Multiple myeloma: an overview of management

Multiple myeloma represents 2% of all new cancer diagnoses in the United Kingdom and accounts for 2% of all cancer deaths. In the past few decades, there have been huge improvements in life expectancy which have been driven by novel therapeutic agents, autologous stem cell transplants and intensified supportive care. This review will discuss the pathogenesis of multiple myeloma, current management approaches and the direction of future treatments. In addition, this review will highlight the high burden of symptoms that patients experience and therefore the great benefits that can be gained from specialist palliative care input.

Hyaluronan hydrogels delivering BMP-6 for local targeting of malignant plasma cells and osteogenic differentiation of mesenchymal stromal cells

Multiple myeloma is a malignant disease characterized by accumulation of clonal plasma cells in the bone marrow. Uncoupling of bone formation and resorption by myeloma cells leads to osteolytic lesions. These are prone to fracture and represent a possible survival space for myeloma cells under treatment causing disease relapse. Here we report on a novel approach suitable for local treatment of multiple myeloma based on hyaluronic acid (HA) hydrogels mimicking the physical properties of the bone marrow. The HA hydrogels are complexed with heparin to achieve sustained presentation and controlled release of bone morphogenetic protein 6 (BMP-6). Others and we have shown that BMP-6 induces myeloma cell apoptosis and bone formation. Using quartz crystal microbalance and enzyme-linked immunosorbent assay, we measured an initial surface density of 400 ng BMP6/cm², corresponding to two BMP-6 per heparin molecule, with 50% release within two weeks. HA-hydrogels presenting BMP-6 enhanced the phosphorylation of Smad 1/5 while reducing the activity of BMP-6 antagonist sclerostin. These materials induced osteogenic differentiation of mesenchymal stromal cells and decreased the viability of myeloma cell lines and primary myeloma cells. BMP-6 functionalized HA-hydrogels represent a promising material for local treatment of myeloma-induced bone disease and residual myeloma cells within lesions to minimize disease relapse or fractures. STATEMENT OF SIGNIFICANCE: Multiple myeloma is a hematological cancer characterized by the accumulation of clonal plasma cells in the bone marrow and local suppression of bone formation, resulting in osteolytic lesions and fractures. Despite recent advances in systemic treatment of multiple myeloma, it is rare to achieve a targeted suppression of myeloma cells and healing of bone lesions. Here we present hydrogels which mimic the physico-chemical properties of the bone marrow, consisting of hyaluronic acid with crosslinked heparin for the controlled presentation of bioactive BMP-6. The hydrogels decrease the viability of myeloma cell lines and primary myeloma cells and induces osteogenic differentiation of mesenchymal stromal cells. The presentation of BMP-6 in the hyaluronan hydrogels enhances the phosphorylation of Smad1/5 while reducing the activity of the BMP-6 antagonist sclerostin. As such, BMP-6 functionalized hyaluronan hydrogels represent a promising material for the localized eradication of myeloma cells.

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.

Coordination between Rac1 and Rab Proteins: Functional Implications in Health and Disease

The small GTPases of the Rho family regulate many aspects of actin dynamics, but are functionally connected to many other cellular processes. Rac1, a member of this family, besides its known function in the regulation of actin cytoskeleton, plays a key role in the production of reactive oxygen species, in gene transcription, in DNA repair, and also has been proven to have specific roles in neurons. This review focuses on the cooperation between Rac1 and Rab proteins, analyzing how the coordination between these GTPases impact on cells and how alterations of their functions lead to disease.