Management of bone metastasis and cancer treatment-induced bone loss during the COVID-19 pandemic: An international perspective and recommendations.

Optimum management of patients with cancer during the COVID-19 pandemic has proved extremely challenging. Patients, clinicians and hospital authorities have had to balance the risks to patients of attending hospital, many of whom are especially vulnerable, with the risks of delaying or modifying cancer treatment. Those whose care has been significantly impacted include patients suffering from the effects of cancer on bone, where delivering the usual standard of care for bone support has often not been possible and clinicians have been forced to seek alternative options for adequate management. At a virtual meeting of the Cancer and Bone Society in July 2020, an expert group shared experiences and solutions to this challenge, following which a questionnaire was sent internationally to the symposium's participants, to explore the issues faced and solutions offered. 70 respondents, from 9 countries (majority USA, 39%, followed by UK, 19%) included 50 clinicians, spread across a diverse range of specialties (but with a high proportion, 64%, of medical oncologists) and 20 who classified themselves as non-clinical (solely lab-based). Spread of clinician specialty across tumour types was breast (65%), prostate (27%), followed by renal, myeloma and melanoma. Analysis showed that management of metastatic bone disease in all solid tumour types and myeloma, adjuvant bisphosphonate breast cancer therapy and cancer treatment induced bone loss, was substantially impacted. Respondents reported delays to routine CT scans (58%), standard bone scans (48%) and MRI scans (46%), though emergency scans were less affected. Delays in palliative radiotherapy for bone pain were reported by 31% of respondents with treatments often involving only a single dose without fractionation. Delays to, or cancellation of, prophylactic surgery for bone pain were reported by 35% of respondents. Access to treatments with intravenous bisphosphonates and subcutaneous denosumab was a major problem, mitigated by provision of drug administration at home or in a local clinic, reduced frequency of administration or switching to oral bisphosphonates taken at home. The questionnaire also revealed damaging delays or complete stopping of both clinical and laboratory research. In addition to an analysis of the questionnaire, this paper presents a rationale and recommendations for adaptation of the normal guidelines for protection of bone health during the pandemic.

Sostdc1: A soluble BMP and Wnt antagonist that is induced by the interaction between myeloma cells and osteoblast lineage cells.

Multiple myeloma (MM) is characterised by destructive lytic bone disease, caused by induction of bone resorption and impaired bone formation. Our understanding of the molecular mechanisms responsible for osteoblast suppression, are limited. Using the 5T2MM murine model of MM we have previously shown that suppression of the activity of a known inhibitor of bone formation Dikkopf-1 (Dkk1) prevents the development of lytic bone disease. Here we have demonstrated that another potential inhibitor of bone formation, sclerostin domain containing 1 (Sostdc1) is expressed at low levels in MM and osteoblast lineage cells when these cells are grown separately in cell culture but its expression is significantly induced in both cell types when these cells are in contact. The distribution of Sostdc1 staining in bones infiltrated with 5TGM1 myeloma cells in vivo suggested its presence in both myeloma and osteoblast lineage populations when in close proximity. We have also shown that recombinant Sostdc1 inhibits both bone morphogenic proteins (BMP2 and 7) and Wnt signalling in primary osteoblasts and suppresses differentiation of these cells. Together, these findings suggest that Sostdc1 expression in 5TGM1-infiltrated bones as a result of the interaction between myeloma and osteoblast lineage populations, could result in suppression of osteoblast differentiation.

Population genetic analyses provide insights on the introduction pathway and spread patterns of the North American forest pathogen Heterobasidion irregulare in Italy.

A population genetics approach is used to identify the most likely introduction site and introduction pathway for the North American forest pathogen Heterobasidion irregulare using 101 isolates from six sites in Italy and 34 isolates from five sites in North America. Diversity indices based on sequences from ten loci indicate the highest diversity in Italy is found in Castelfusano/Castelporziano and that diversity progressively decreases with increasing distance from that site. AMOVA, Bayesian clustering and principal coordinates analyses based on 12 SSR loci indicate high levels of gene flow among sites, high frequency of admixing, and fail to identify groups of genotypes exclusive to single locations. Cumulatively, these analyses suggest the current infestation is the result of multiple genotypes expanding their range from a single site. Based on two sequenced loci, a single source site in North America could provide enough variability to explain the variability observed in Italy. These results support the notion that H. irregulare was introduced originally in Castelporziano: because Castelporziano has been sealed off from the rest of the world for centuries except for a camp set up by the US military in 1944, we conclude the fungus may have been transported in infected wood used by the military. Finally, spatial autocorrelation analyses using SSR data indicate a significant under-dispersion of alleles up to 0.5-10 km, while a significant overdispersion of alleles was detected at distances over 80 km: these ranges can be used to make predictions on the likely dispersal potential of the invasive pathogen.

Bisphosphonate therapy in the treatment of multiple myeloma.

Multiple myeloma is an incurable B cell neoplasm caused by the monoclonal expansion of malignant plasma cells in the bone marrow, often resulting in devastating bone disease. For over 2 decades bisphosphonates have been successfully used to treat the tumour-induced bone disease associated with multiple myeloma. This review will focus on preclinical studies and investigations in patients with multiple myeloma that have led to our current understanding of the mechanisms of action of bisphosphonates in myeloma bone disease. Major advances in the use of bisphosphonates, including findings that they may have additional benefits such as anti-tumour effects and promoting patient survival will be discussed.

Targeting RANK/RANKL in the treatment of solid tumours and myeloma.

Cancers which damage the human skeleton include multiple myeloma, where the primary tumour colonises bone directly, or breast and prostate cancer, where malignant cells travel from the primary tumour to form clonal outgrowths within the bone. Owing to the interaction of tumour cells with those normally found in the bone microenvironment, such as osteoclasts and osteoblasts, these cancers affect the closely linked processes of bone formation and resorption. As a result, these twin processes contribute to the clinical manifestations of cancer metastasis, including bone pain and pathological fractures. A critical component of physiologically normal bone remodelling, the RANK/RANKL/OPG pathway, has been implicated in the formation of osteolytic, and possibly osteoblastic, lesions, which characterise the bone disease associated with these malignancies. In these cancers that affect the skeleton in this way the abnormally regulated RANK/RANKL system appears to be the final effector pathway. As a result, there has been much research focused upon targeting these molecules using OPG constructs, peptidomimetics, soluble receptor constructs and antibodies to RANKL, in pre-clinical studies. The success of these studies has paved the way for a clinical programme, the success of which is likely to lead to a new therapeutic approach to treating cancers that develop in the skeleton.

Genetic epidemiology of the sudden oak death pathogen Phytophthora ramorum in California.

A total of 669 isolates of Phytophthora ramorum, the pathogen responsible for Sudden Oak Death, were collected from 34 Californian forests and from the ornamental plant-trade. Seven microsatellite markers revealed 82 multilocus genotypes (MGs) of which only three were abundant (>10%). Iteratively collapsing based upon minimum Phi(ST), yielded five meta-samples and five singleton populations. Populations in the same meta-sample were geographically contiguous, with one exception, possibly explained by the trade of infected plants from the same source into different locations. Multidimensional scaling corroborated this clustering and identified nursery populations as genetically most distant from the most recent outbreaks. A minimum-spanning network illustrated the evolutionary relationships among MGs, with common genotypes at the centre and singletons at the extremities; consistent with colonization by a few common genotypes followed by local evolution. Coalescent migration analyses used the original data set and a data set in which local genotypes were collapsed into common ancestral genotypes. Both analyses suggested that meta-samples 1 (Santa Cruz County) and 3 (Sonoma and Marin Counties), act as sources for most of the other forests. The untransformed data set best explains the first phases of the invasion, when the role of novel genotypes may have been minimal, whereas the second analysis best explains migration patterns in later phases of the invasion, when prevalence of novel genotypes was likely to have become more significant. Using this combined approach, we discuss possible migration routes based on our analyses, and compare them to historical and field observations from several case studies.

The effects of JNJ-26481585, a novel hydroxamate-based histone deacetylase inhibitor, on the development of multiple myeloma in the 5T2MM and 5T33MM murine models.

Multiple myeloma (MM) is a B-cell malignancy, which often remains incurable because of the development of drug resistance governed by the bone marrow (BM) microenvironment. Novel treatment strategies are therefore urgently needed. In this study, we evaluated the anti-MM activity of JNJ-26481585, a novel 'second-generation' pyrimidyl-hydroxamic acid-based histone deacetylase inhibitor, using the syngeneic murine 5TMM model of MM. In vitro, JNJ-26481585 induced caspase cascade activation and upregulation of p21, resulting in apoptosis and cell cycle arrest in the myeloma cells at low nanomolar concentrations. Similar results could be observed in BM endothelial cells using higher concentrations, indicating the selectivity of JNJ-26481585 toward cancer cells. In a prophylactic and therapeutic setting, treatment with JNJ-26481585 resulted in an almost complete reduction of the tumor load and a significant decrease in angiogenesis. 5T2MM-bearing mice also developed a MM-related bone disease, characterized by increased osteoclast number, development of osteolytic lesions and a reduction in cancellous bone. Treatment of these mice with JNJ-264815 significantly reduced the development of bone disease. These data suggest that JNJ-26481585 has a potent anti-MM activity that can overcome the stimulatory effect of the BM microenvironment in vivo making this drug a promising new anti-MM agent.

The use of bisphosphonates in multiple myeloma: recommendations of an expert panel on behalf of the European Myeloma Network.

BACKGROUND: Bisphosphonates (BPs) prevent, reduce, and delay multiple myeloma (MM)-related skeletal complications. Intravenous pamidronate and zoledronic acid, and oral clodronate are used for the management of MM bone disease. The purpose of this paper is to review the current evidence for the use of BPs in MM and provide European Union-specific recommendations to support the clinical practice of treating myeloma bone disease. DESIGN AND METHODS: An interdisciplinary, expert panel of specialists on MM and myeloma-related bone disease convened for a face-to-face meeting to review and assess the evidence and develop the recommendations. The panel reviewed and graded the evidence available from randomized clinical trials, clinical practice guidelines, and the body of published literature. Where published data were weak or unavailable, the panel used their own clinical experience to put forward recommendations based solely on their expert opinions. RESULTS: The panel recommends the use of BPs in MM patients suffering from lytic bone disease or severe osteoporosis. Intravenous administration may be preferable; however, oral administration can be considered for patients unable to make hospital visits. Dosing should follow approved indications with adjustments if necessary. In general, BPs are well tolerated, but preventive steps should be taken to avoid renal impairment and osteonecrosis of the jaw (ONJ). The panel agrees that BPs should be given for 2 years, but this may be extended if there is evidence of active myeloma bone disease. Initial therapy of ONJ should include discontinuation of BPs until healing occurs. BPs should be restarted if there is disease progression. CONCLUSIONS: BPs are an essential component of MM therapy for minimizing skeletal morbidity. Recent retrospective data indicate that a modified dosing regimen and preventive measures can greatly reduce the incidence of ONJ.

The combination of bortezomib, melphalan, dexamethasone and intermittent thalidomide is an effective regimen for relapsed/refractory myeloma and is associated with improvement of abnormal bone metabolism and angiogenesis.

This phase 2 study aimed to determine the efficacy and safety of the combination of bortezomib, melphalan, dexamethasone and intermittent thalidomide (VMDT) and its effect on bone remodeling and angiogenesis in relapsed/refractory myeloma. Bortezomib (1.0 mg/m(2)) was given on days 1, 4, 8, 11, oral melphalan (0.15 mg/kg) on days 1-4, whereas thalidomide (100 mg per day) and dexamethasone (12 mg/m(2)) were administered on days 1-4 and 17-20 of a 28-day cycle, for four cycles. Patients without disease progression continued for up to eight cycles. VMDT effect on bone remodeling was evaluated by measuring osteoclast regulators (soluble receptor activator of nuclear factor-kappa B ligand/osteoprotegerin ratio, osteopontin, macrophage inflammatory protein-1alpha), dickkopf-1 protein, bone resorption and formation markers, whereas its effect on angiogenesis was assessed by measuring serum vascular endothelial growth factor, angiogenin, angiopoietin-2 and basic fibroblast growth factor, after four cycles and at the study end. A total of 62 patients were enrolled. The overall response rate was 66%: CR 13%, vgPR 27% and PR 26%. Median time to response was 35 days and median time to progression was 9.3 months. Common adverse events included cytopenias, peripheral neuropathy and infections. No patient experienced deep-vein thrombosis. VMDT reduced angiogenic cytokines, osteoclast regulators, dickkopf-1 and bone resorption. We conclude that VMDT with intermittent thalidomide is an active and well-tolerated regimen for relapsed/refractory myeloma, affecting abnormal bone remodeling and angiogenesis.

Reconstruction of the Sudden Oak Death epidemic in California through microsatellite analysis of the pathogen Phytophthora ramorum.

The genetic structure of the clonally reproducing Sudden Oak Death (SOD) pathogen in California was investigated using seven variable microsatellites. A total of 35 multilocus genotypes were identified among 292 samples representative of populations from 14 forest sites and of the nursery trade. amova indicated significant genetic variability both within (44.34%) and among populations (55.66%). Spatial autocorrelation analyses indicated that Moran's index of similarity reached a minimum of 0.1 at 350 m, increased to 0.4 at 1500 m and then decreased to zero at 10 km. These results suggest a bimodal pattern of spread, with medium range dispersal (1500-10,000 m) putatively attributed to the presence of strong winds. Lack of genetic structure was identified for three groups of populations. One group notably included the nurseries' population and two forest populations, both linked to early reports of the pathogen. A neighbour-joining analysis based on pairwise Phi(ST) values indicated that the clade inclusive of the nurseries' populations is basal to all California populations. A network analysis identified three common genotypes as the likely founders of the California infestation and proposes a stepwise model for local evolution of novel genotypes. This was supported by the identification in the same locations of novel genotypes and of their 1- or 2-step parents. We hypothesize that the few undifferentiated population groups indicate historical human spread of the pathogen, while the general presence of genetically structured populations indicates that new infestations are currently generated by rare medium or long-range natural movement of the pathogen, followed by local generation of new genotypes.

A new xenograft model of myeloma bone disease demonstrating the efficacy of human mesenchymal stem cells expressing osteoprotegerin by lentiviral gene transfer.

We describe a new model of myeloma bone disease in which beta2m NOD/SCID mice injected with KMS-12-BM cells develop medullary disease after tail vein administration. Micro-computed tomography analysis demonstrated significant bone loss in the tibiae and vertebrae of diseased animals compared to controls, with loss of cortical bone (P<0.01), as well as trabecular bone volume, thickness and number (P<0.05 for all). Bone marrow of diseased animals demonstrated an increase in osteoclasts (P<0.01) and reduction in osteoblasts (P<0.01) compared to control animals. Both bone loss and osteoclast increase correlated with the degree of disease involvement. Mesenchymal stem cells (MSCs) were lentivirally transduced to express human osteoprotegerin (hOPG). Systemic administration of OPG expressing MSC reduced osteoclast activation (P<0.01) and trabecular bone loss in the vertebrae (P<0.05) and tibiae of diseased animals, to levels comparable to non-diseased controls. Because of its predominantly medullary involvement and quantifiable parameters of bone disease, the KMS-12-BM xenogeneic model provides unique opportunities to test therapies targeted at the bone marrow microenvironment.

Agonists of TRAIL death receptors induce myeloma cell apoptosis that is not prevented by cells of the bone marrow microenvironment.

The growth and survival of myeloma cells is critically regulated by cells of the bone marrow microenvironment, including osteoblasts. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of myeloma cell apoptosis, however, this antimyeloma activity is inhibited by osteoprotegerin (OPG) released from osteoblasts. Therefore, we hypothesized that specific agonists of TRAIL death receptors would not be inhibited by OPG released from osteoblasts and thus may represent a novel therapeutic approach in multiple myeloma. In the present study, TRAIL-induced apoptosis was demonstrated to be mediated through both DR4 and DR5. Specific agonist antibodies to DR4 or DR5 dose-dependently induced myeloma cell apoptosis, which was not prevented by OPG or by medium conditioned by osteoblasts. Co-culture of myeloma cells with osteoblasts protected against TRAIL-induced apoptosis of myeloma cells, and this protective effect was due to OPG. In contrast, the co-culture of myeloma cells with osteoblasts had no protective effect on apoptosis induced by specific agonists of DR4 or DR5. TRAIL has been proposed as a potential antitumour therapy, but within the bone marrow microenvironment OPG may interfere with the action of TRAIL. Specific agonists of TRAIL death receptors would not be subject to this inhibition and thus may provide an alternative specific antimyeloma therapy.

The anti-tumor potential of zoledronic acid.

Bone is a favorable microenvironment for tumor cell colonization because of abundant growth factors released during active bone resorption. Bisphosphonates can dramatically affect the ability of tumor cells to grow in bone by inhibiting osteoclast-mediated bone resorption and by depriving tumors of growth-promoting signals. Moreover, bisphosphonates have direct anti-tumor effects in vitro via induction of apoptosis. Zoledronic acid is a nitrogen-containing bisphosphonate that has demonstrated potent anti-tumor activity in vitro and in vivo. In vitro studies have provided important clues as to the molecular mechanisms by which zoledronic acid induces apoptosis of human breast cancer cell lines. Studies in multiple myeloma and breast cancer models have shed further light on the possible mechanisms underlying the in vivo anti-tumor effects of zoledronic acid. These studies have led to the development of novel strategies to target specific molecular pathways involved in osteoclast maturation and activity, tumor cell metastasis, and tumor growth and survival. The clinical application of these strategies may ultimately prevent bone metastasis.

Colonic dendritic cells, intestinal inflammation, and T cell-mediated bone destruction are modulated by recombinant osteoprotegerin.

Autoimmune associated bone disease and intestinal inflammation are closely linked with deregulation and hyperactivation of autoreactive CD4 T cells. How these T cells are activated and mediate disease is not clear. Here we show that in the Interleukin 2-deficient mouse model of autoimmunity spontaneous osteopenia and colitis are caused by increased production of the ligand for receptor activator of NFkappaB (RANKL). RANKL acting via its receptor, receptor activator of NFkappaB (RANK), increases bone turnover and promotes intestinal dendritic cell (DC) survival in vivo. Modulation of RANKL-RANK interactions with exogenous recombinant osteoprotegerin (Fc-OPG) reverses skeletal abnormalities and reduces colitis by decreasing colonic DC numbers. This study identifies a common causal link between bone disease and intestinal inflammation and establishes the importance of DC in mediating colonic inflammation in vivo.

Osteoprotegerin inhibits the development of osteolytic bone disease in multiple myeloma.

Multiple myeloma is a B-cell malignancy characterized by the accumulation of plasma cells in the bone marrow and the development of osteolytic bone disease. The present study demonstrates that myeloma cells express the critical osteoclastogenic factor RANKL (the ligand for receptor activator of NF-kappa B). Injection of 5T2MM myeloma cells into C57BL/KaLwRij mice resulted in the development of bone disease characterized by a significant decrease in cancellous bone volume in the tibial and femoral metaphyses, an increase in osteoclast formation, and radiologic evidence of osteolytic bone lesions. Dual-energy x-ray absorptiometry demonstrated a decrease in bone mineral density (BMD) at each of these sites. Treatment of mice with established myeloma with recombinant osteoprotegerin (OPG) protein, the soluble decoy receptor for RANKL, prevented the development of lytic bone lesions. OPG treatment was associated with preservation of cancellous bone volume and inhibition of osteoclast formation. OPG also promoted an increase in femoral, tibial, and vertebral BMD. These data suggest that the RANKL/RANK/OPG system may play a critical role in the development of osteolytic bone disease in multiple myeloma and that targeting this system may have therapeutic potential.

Evidence of a role for a non-matrix-type metalloproteinase activity in the shedding of syndecan-1 from human myeloma cells.

Syndecan-1 is a cell surface proteoglycan that is expressed on human myeloma cells and is thought to act as a co-receptor for certain extracellular matrix proteins and growth factors. The ectodomain of syndecan-1 is thought to be shed from the surface of myeloma cells, although the exact mechanism of release remains unclear. In this study, we used a panel of inhibitors to identify the class of proteinase responsible for shedding the soluble syndecan-1 ectodomain from human myeloma cells. Using enzyme-linked immunosorbent assay, flow cytometry and immunocytochemistry, we demonstrated that myeloma cell lines expressed syndecan-1 on their surface and that this was shed constitutively, but to a varying extent. In addition, phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, stimulated a marked loss of cell surface syndecan-1 from each of the cell lines and this was associated with a corresponding increase in soluble syndecan-1. Inhibitors of serine and cysteine proteinases, and matrix-type metalloproteinases, did not inhibit constitutive or PMA-stimulated syndecan-1 shedding from JJN3 and RPMI 8226 cells. However, BB-94, a hydroxamate-based, broad-spectrum, metalloproteinase inhibitor, substantially suppressed constitutive and PMA-stimulated syndecan-1 loss from myeloma cells. These data indicate that a non-matrix-type metalloproteinase is responsible for syndecan-1 shedding from the surface of myeloma cells.