Cancer and bone

Bone damage and health-related quality of life in Hodgkin lymphoma survivors: closing the gaps

In the recent decades, remarkable successes have been recorded in the treatment of Hodgkin's lymphoma to the point that today it represents one of the neoplasms with the highest rates of cure and with the highest life expectancy. Nonetheless, this raises the concern for the health of long- term survivors. Late side effects of treatments in synergy with other risk factors expose survivors to increased morbidity and impaired quality of life. In the complexity of the topics concerning these last aspects, an area of growing interest is that of bone damage that follows Hodgkin Lymphoma and its treatments. In this narrative review, we conducted our work through assessment of available evidence focusing on several aspects linking bone damage and quality of life with Hodgkin lymphoma and its treatments. At present, the problem of osteopenia and osteoporosis in Hodgkin lymphoma survivors is a theme for which awareness and knowledge need to be implemented.

IFN-β mediates the anti-osteoclastic effect of bisphosphonates and dexamethasone

Zoledronic acid (Zol) is a potent bisphosphonate that inhibits the differentiation of monocytes into osteoclasts. It is often used in combination with dexamethasone (Dex), a glucocorticoid that promotes the resolution of inflammation, to treat malignant diseases, such as multiple myeloma. This treatment can result in bone pathologies, namely medication related osteonecrosis of the jaw, with a poor understanding of the molecular mechanism on monocyte differentiation. IFN-β is a pro-resolving cytokine well-known as an osteoclast differentiation inhibitor. Here, we explored whether Zol and/or Dex regulate macrophage osteoclastic differentiation via IFN-β. RAW 264.7 and peritoneal macrophages were treated with Zol and/or Dex for 4-24 h, and IFN-β secretion was examined by ELISA, while the IFN stimulated gene (ISG) 15 expression was evaluated by Western blotting. RANKL-induced osteoclastogenesis of RAW 264.7 cells was determined by TRAP staining following treatment with Zol+Dex or IFN-β and anti-IFN-β antibodies. We found only the combination of Zol and Dex increased IFN-β secretion by RAW 264.7 macrophages at 4 h and, correspondingly, ISG15 expression in these cells at 24 h. Moreover, Zol+Dex blocked osteoclast differentiation to a similar extent as recombinant IFN-β. Neutralizing anti-IFN-β antibodies reversed the effect of Zol+Dex on ISG15 expression and partially recovered osteoclastic differentiation induced by each drug alone or in combination. Finally, we found Zol+Dex also induced IFN-β expression in peritoneal resolution phase macrophages, suggesting these drugs might be used to enhance the resolution of acute inflammation. Altogether, our findings suggest Zol+Dex block the differentiation of osteoclasts through the expression of IFN-β. Revealing the molecular pathway behind this regulation may lead to the development of IFN-β-based therapy to inhibit osteoclastogenesis in multiple myeloma patients.

The Effect of a Histone Deacetylase Inhibitor (AR-42) and Zoledronic Acid on Adult T-Cell Leukemia/Lymphoma Osteolytic Bone Tumors

Simple Summary

Adult T-cell leukemia (ATL) Leukemia is an aggressive, peripheral blood (T-cell) neoplasm associated with human T-cell leukemia virus type 1 (HTLV-1) infection. Recent studies have implicated dysregulated histone deacetylases in ATL pathogenesis. ATL modulates the bone microenvironment of patients and activates osteoclasts (bone resorbing cells) that cause severe bone loss. The objective of this study was to assess the individual and dual effects of AR-42 (HDACi) and zoledronic acid (Zol) on the growth of ATL cells in vitro and in vivo. AR-42 and Zol reduced the viability of ATL cells in vitro. Additionally, Zol and Zol/AR-42 decreased ATL tumor growth and halted osteolysis in bone tumor xenografts in immunodeficient mice in vivo. Our study suggests that dual targeting of ATL cells (using HDACi) and bone osteoclasts (using bisphosphonates) may be exploited as a valuable approach to reduce bone tumor burden and improve the life quality of ATL patients.

Abstract

Adult T-cell leukemia/lymphoma (ATL) is an intractable disease affecting nearly 4% of Human T-cell Leukemia Virus Type 1 (HTLV-1) carriers. Acute ATL has a unique interaction with bone characterized by aggressive bone invasion, osteolytic metastasis, and hypercalcemia. We hypothesized that dual tumor and bone-targeted therapies would decrease tumor burden in bone, the incidence of metastasis, and ATL-associated osteolysis. Our goal was to evaluate dual targeting of both ATL bone tumors and the bone microenvironment using an anti-tumor HDACi (AR-42) and an osteoclast inhibitor (zoledronic acid, Zol), alone and in combination. Our results showed that AR-42, Zol, and AR-42/Zol significantly decreased the viability of multiple ATL cancer cell lines in vitro. Zol and AR-42/Zol decreased tumor growth in vivo. Zol ± AR-42 significantly decreased ATL-associated bone resorption and promoted new bone formation. AR-42-treated ATL cells had increased mRNA levels of PTHrP, ENPP2 (autotaxin) and MIP-1α, and TAX viral gene expression. AR-42 alone had no significant effect on tumor growth or osteolysis in mice. These findings indicate that Zol adjuvant therapy has the potential to reduce growth of ATL in bone and its associated osteolysis.

3D Printing and Bioprinting to Model Bone Cancer: The Role of Materials and Nanoscale Cues in Directing Cell Behavior

Bone cancer, both primary and metastatic, is characterized by a low survival rate. Currently, available models lack in mimicking the complexity of bone, of cancer, and of their microenvironment, leading to poor predictivity. Three-dimensional technologies can help address this need, by developing predictive models that can recapitulate the conditions for cancer development and progression. Among the existing tools to obtain suitable 3D models of bone cancer, 3D printing and bioprinting appear very promising, as they enable combining cells, biomolecules, and biomaterials into organized and complex structures that can reproduce the main characteristic of bone. The challenge is to recapitulate a bone-like microenvironment for analysis of stromal-cancer cell interactions and biological mechanics leading to tumor progression. In this review, existing approaches to obtain in vitro 3D-printed and -bioprinted bone models are discussed, with a focus on the role of biomaterials selection in determining the behavior of the models and its degree of customization. To obtain a reliable 3D bone model, the evaluation of different polymeric matrices and the inclusion of ceramic fillers is of paramount importance, as they help reproduce the behavior of both normal and cancer cells in the bone microenvironment. Open challenges and future perspectives are discussed to solve existing shortcomings and to pave the way for potential development strategies.

Mechanisms Supporting the Use of Beta-Blockers for the Management of Breast Cancer Bone Metastasis

Simple Summary

Bone represents the most common site of metastasis for breast cancer and the establishment and growth of metastatic cancer cells within the skeleton significantly reduces the quality of life of patients and their survival. The interplay between sympathetic nerves and bone cells, and its influence on the process of breast cancer bone metastasis is increasingly being recognized. Several mechanisms, all dependent on β-adrenergic receptor signaling in stromal bone cells, were shown to promote the establishment of disseminated cancer cells into the skeleton. This review provides a summary of these mechanisms in support of the therapeutic potential of β-blockers for the early management of breast cancer metastasis.

Abstract

The skeleton is heavily innervated by sympathetic nerves and represents a common site for breast cancer metastases, the latter being the main cause of morbidity and mortality in breast cancer patients. Progression and recurrence of breast cancer, as well as decreased overall survival in breast cancer patients, are associated with chronic stress, a condition known to stimulate sympathetic nerve outflow. Preclinical studies have demonstrated that sympathetic stimulation of β-adrenergic receptors in osteoblasts increases bone vascular density, adhesion of metastatic cancer cells to blood vessels, and their colonization of the bone microenvironment, whereas β-blockade prevented these events in mice with high endogenous sympathetic activity. These findings in preclinical models, along with clinical data from breast cancer patients receiving β-blockers, support the pathophysiological role of excess sympathetic nervous system activity in the formation of bone metastases, and the potential of commonly used, safe, and low-cost β-blockers as adjuvant therapy to improve the prognosis of bone metastases.

Interleukin 11 (IL-11): Role(s) in Breast Cancer Bone Metastases

Bone metastases represent the main problem related to the progression of breast cancer, as they are the main cause of death for these patients. Unfortunately, to date, bone metastases are incurable and represent the main challenge for the researcher. Chemokines and cytokines affect different stages of the metastatic process, and in bone metastases, interleukin (IL) -6, IL-8, IL-1β, and IL-11 participate in the interaction between cancer cells and bone cells. This review focuses on IL-11, a pleiotropic cytokine that, in addition to its well-known effects on several tissues, also mediates certain signals in cancer cells. In particular, as IL-11 works on bone remodeling, it plays a relevant role in the osteolytic vicious cycle of bone resorption and tumour growth, which characterizes bone metastasis. IL-11 appears as a candidate for anti-metastatic therapy. Even if different therapeutic approaches have considered IL-11 and the downstream-activated gp130 signaling pathways activated downstream of gp130, further studies are needed to decipher the contribution of the different cytokines and their mechanisms of action in breast cancer progression to define therapeutic strategies.

Progress in Targeted Alpha-Particle-Emitting Radiopharmaceuticals as Treatments for Prostate Cancer Patients with Bone Metastases

Bone metastasis remains a major cause of death in cancer patients, and current therapies for bone metastatic disease are mainly palliative. Bone metastases arise after cancer cells have colonized the bone and co-opted the normal bone remodeling process. In addition to bone-targeted therapies (e.g., bisphosphonate and denosumab), hormone therapy, chemotherapy, external beam radiation therapy, and surgical intervention, attempts have been made to use systemic radiotherapy as a means of delivering cytocidal radiation to every bone metastatic lesion. Initially, several bone-seeking beta-minus-particle-emitting radiopharmaceuticals were incorporated into the treatment for bone metastases, but they failed to extend the overall survival in patients. However, recent clinical trials indicate that radium-223 dichloride (223RaCl2), an alpha-particle-emitting radiopharmaceutical, improves the overall survival of prostate cancer patients with bone metastases. This success has renewed interest in targeted alpha-particle therapy development for visceral and bone metastasis. This review will discuss (i) the biology of bone metastasis, especially focusing on the vicious cycle of bone metastasis, (ii) how bone remodeling has been exploited to administer systemic radiotherapies, and (iii) targeted radiotherapy development and progress in the development of targeted alpha-particle therapy for the treatment of prostate cancer bone metastasis.

Inhibition of furin by bone targeting superparamagnetic iron oxide nanoparticles alleviated breast cancer bone metastasis

Breast cancer bone metastasis poses significant challenge for therapeutic strategies. Inside the metastatic environment, osteoclasts and tumor cells interact synergistically to promote cancer progression. In this study, the proprotein convertase furin is targeted due to its critical roles in both tumor cell invasion and osteoclast function. Importantly, the furin inhibitor is specifically delivered by bone targeting superparamagnetic iron oxide (SPIO) nanoparticles. Our in vitro and in vivo data demonstrate that this system can effectively inhibit both osteoclastic bone resorption and breast cancer invastion, leading to alleviated osteolysis. Therefore, the bone targeting & furin inhibition nanoparticle system is a promising therapeutic and diagnostic strategy for breast cancer bone metastasis.

Better pain control with 8-gray single fraction palliative radiotherapy for skeletal metastases: a Bayesian network meta-analysis

External Beam Radiotherapy (EBRT) allows remarkable pain control in patients with skeletal metastases. We performed a Bayesian network meta-analysis comparing the most commonly used radiotherapy regimens for palliative management in patients with skeletal metastases. The main online databases were accessed in October 2020. All randomized clinical trials evaluating the irradiation of painful bone metastases were considered. The following irradiation patterns were analysed and included in the present network meta-analysis: 8 Gy- and 10 Gy/single fraction, 20 Gy/5 fractions, 30 Gy/10 fractions. The Bayesian hierarchical random-effect model analysis was adopted in all comparisons. The Log Odds-Ratio (LOR) statistical method for dichotomic data was adopted for analysis. Data from 3595 patients were analysed. The mean follow-up was 9.5 (1 to 28) months. The cumulative mean age was 63.3 ± 2.9. 40.61% (1461 of 3595 patients) were female. The 8Gy/single fraction protocol detected reduced rate of “no pain response” (LOR 3.39), greater rate of “pain response” (LOR-5.88) and complete pain remission (LOR-7.05) compared to the other dose patterns. The 8Gy group detected a lower rate of pathological fractures (LOR 1.16), spinal cord compression (LOR 1.31) and re-irradiation (LOR 2.97) compared to the other dose patterns. Palliative 8Gy/single fraction radiotherapy for skeletal metastases shows outstanding results in terms of pain control, re-irradiations, pathological fractures and spinal cord compression, with no differences in terms of survivorship compared to the other multiple dose patterns.

Level of evidence: I, Bayesian network meta-analysis of RCTs.

Printing the Pathway Forward in Bone Metastatic Cancer Research: Applications of 3D Engineered Models and Bioprinted Scaffolds to Recapitulate the Bone-Tumor Niche

Breast cancer commonly metastasizes to bone, resulting in osteolytic lesions and poor patient quality of life. The bone extracellular matrix (ECM) plays a critical role in cancer cell metastasis by means of the physical and biochemical cues it provides to support cellular crosstalk. Current two-dimensional in-vitro models lack the spatial and biochemical complexities of the native ECM and do not fully recapitulate crosstalk that occurs between the tumor and endogenous stromal cells. Engineered models such as bone-on-a-chip, extramedullary bone, and bioreactors are presently used to model cellular crosstalk and bone-tumor cell interactions, but fall short of providing a bone-biomimetic microenvironment. Three-dimensional bioprinting allows for the deposition of biocompatible materials and living cells in complex architectures, as well as provides a means to better replicate biological tissue niches in-vitro. In cancer research specifically, 3D constructs have been instrumental in seminal work modeling cancer cell dissemination to bone and bone-tumor cell crosstalk in the skeleton. Furthermore, the use of biocompatible materials, such as hydroxyapatite, allows for printing of bone-like microenvironments with the ability to be implanted and studied in in-vivo animal models. Moreover, the use of bioprinted models could drive the development of novel cancer therapies and drug delivery vehicles.

'Educated' Osteoblasts Reduce Osteoclastogenesis in a Bone-Tumor Mimetic Microenvironment

Breast cancer (BC) metastases to bone disrupt the balance between osteoblasts and osteoclasts, leading to excessive bone resorption. We identified a novel subpopulation of osteoblasts with tumor-inhibitory properties, called educated osteoblasts (EOs). Here we sought to examine the effect of EOs on osteoclastogenesis during tumor progression. We hypothesized that EOs affect osteoclast development in the bone-tumor niche, leading to suppressed pre-osteoclast fusion and bone resorption. Conditioned media (CM) was analyzed for protein expression of osteoclast factors receptor activator of nuclear factor kappa-β ligand (RANKL), osteoprotegerin (OPG), and tumor necrosis factor alpha (TNFα) via ELISA. EOs were co-cultured with pre-osteoclasts on a bone mimetic matrix to assess osteoclast resorption. Pre-osteoclasts were tri-cultured with EOs plus metastatic BC cells and assessed for tartrate-resistance acid phosphatase (TRAP)-positive, multinucleated (≥3 nuclei), mature osteoclasts. Tumor-bearing murine tibias were stained for TRAP to determine osteoclast number in-vivo. EO CM expressed reduced amounts of soluble TNFα and OPG compared to naïve osteoblast CM. Osteoclasts formed in the presence of EOs were smaller and less in number. Upon co-culture on a mimetic bone matrix, a 50% reduction in the number of TRAP-positive osteoclasts formed in the presence of EOs was observed. The tibia of mice inoculated with BC cells had less osteoclasts per bone surface in bones with increased numbers of EO cells. These data suggest EOs reduce osteoclastogenesis and bone resorption. The data imply EOs provide a protective effect against bone resorption in bone metastatic BC.

Abscisic acid regulates dormancy of prostate cancer disseminated tumor cells in the bone marrow

Prostate cancer (PCa) commonly metastasizes to the bone where the cells frequently undergo dormancy. The escape of disseminated tumor cells from cellular dormancy is a major cause of recurrence in marrow. Abscisic acid (ABA), a phytohormone, is known to regulate dormancy of plant seeds and to regulate other stress responses in plants. Recently, ABA was found to be synthesized by mammals cells and has been linked to human disease. Yet the role of ABA in regulating tumor dormancy or reactivation is unknown. We found that ABA is produced by human marrow cells, and exogenous ABA inhibits PCa cell proliferation while increasing the expression of p27, p21, and p16 and decreasing the expression of the proliferation marker, Ki67. Further, ABA significantly increased the percentage of PCa cells in the G₀ phase of the cell cycle as well as the duration the cells were arrested in G₀. We found that ABA regulates an increase of PPARγ receptor expression and suppressed phosphorylation of mTOR/p70S6K signaling and resulting in the induction of the cellular dormancy. We then confirmed that ABA regulates G₀ cell cycle arrest through PPARγ receptor signaling in vitro and under co-culture conditions with osteoblasts. Finally, we demonstrate that ABA regulates PCa dormancy in vivo following intratibial injection in an animal model. Together these data suggest that the ABA and PPARγ signaling pathways contribute to the establishment of PCa cellular dormancy in the bone marrow microenvironment. These findings may suggest critical pathways for targeting metastatic disease.

Whole Genome DNA Methylation and Gene Expression Profiling of Oropharyngeal Cancer Patients in North-Eastern India: Identification of Epigenetically Altered Gene Expression Reveals Potential Biomarkers

Oropharyngeal cancer is a subtype of head and neck squamous cell carcinoma that is associated with unique risk exposures like consumption of smokeless tobacco and areca nut and is highly prevalent in the northeastern region of India, especially Meghalaya. However, the underlying epigenetic and transcriptomic changes in this cancer type is yet to be delineated. We have undertaken a study on genome wide somatic alterations in the DNA methylation and transcriptome in oropharyngeal cancer patients from this region using genome wide techniques in paired tumors and adjacent normal tissues. By using integrative approaches, we have identified 194 epigenetically silenced and 241 epigenetically overexpressed genes in the tumor tissue of these patients. Pathways that are significantly enriched by these genes include the pathways of immune systems, such as the interleukin signaling pathways and Toll-like receptor signaling pathway. Also, osteoclast differentiation pathway was found to be epigenetically upregulated. The pathways enriched by the epigenetically downregulated genes were found to be predominantly those involved in xenobiotic metabolism and keratinization. Two major transcription factors - SPI1 and RUNX1 were identified as epigenetically dysregulated, which further modulates 129 downstream genes. Comparison of our observations with the head and neck cancer data from TCGA revealed distinct DNA methylation and gene expression landscapes which might be specific for oropharyngeal cancer. HPV DNA sequences were not detected in any of the tumor samples in RNA-Seq data. The results obtained in this study might provide improved understanding of the disease.

Does vitamin D deficiency predict tumour malignancy in patients with bone tumours? Data from a multi-center cohort analysis

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Vitamin D deficiency is common in patients with bone tumours.

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Potential association between pre-diagnostic vitamin D status and tumour malignancy in patients with bone tumours.

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25(OH)D status should routinely be assessed and monitored in patients with bone tumours.

Vitamin D deficiency is a global health concern that is estimated to afflict over one billion people globally. The major role of vitamin D is that of a regulator of calcium and phosphate metabolism, thus, being essential for proper bone mineralisation. Concomitantly, vitamin D is known to exert numerous extra-skeletal actions. For example, it has become evident that vitamin D has direct anti-proliferative, pro-differentiation and pro-apoptotic actions on cancer cells. Hence, vitamin D deficiency has been associated with increased cancer risk and worse prognosis in several malignancies. We have recently demonstrated that vitamin D deficiency promotes secondary cancer growth in bone. These findings were partly attributable to an increase in bone remodelling but also through direct effects of vitamin D on cancer cells. To date, very little is known about vitamin D status of patients with bone tumours in general. Thus, the objective of this study was to assess vitamin D status of patients with diverse bone tumours. Moreover, the aim was to elucidate whether or not there is an association between pre-diagnostic vitamin D status and tumour malignancy in patients with bone tumours.

In a multi-center analysis, 25(OH)D, PTH and calcium levels of 225 patients that presented with various bone tumours between 2017 and 2018 were assessed. Collectively, 76% of all patients had insufficient vitamin D levels with a total mean 25(OH)D level of 21.43 ng/ml (53.58 nmol/L). In particular, 52% (117/225) of patients were identified as vitamin D deficient and further 24% of patients (55/225) were vitamin D insufficient. Notably, patients diagnosed with malignant bone tumours had significantly lower 25(OH)D levels than patients diagnosed with benign bone tumours [19.3 vs. 22.75 ng/ml (48.25 vs. 56.86 nmol/L); p = 0.04).

In conclusion, we found a widespread and distressing rate of vitamin D deficiency and insufficiency in patients with bone tumours. However, especially for patients with bone tumours sufficient vitamin D levels seem to be of great importance. Thus, we believe that 25(OH)D status should routinely be monitored in these patients. Collectively, there should be an increased awareness for physicians to assess and if necessary correct vitamin D status of patients with bone tumours in general or of those at great risk of developing bone tumours.

Bone metastases: a comprehensive review of the literature

The last report of the World Health Organization (WHO) stated that approximately four million people experience bone pain due to malignant diseases. Among them, metastatic bone pain is one of the most important sources of complaint. The estimated median survival in the presence of bone metastases ranks from 10 to 12 weeks. Bone represents a potential target of distant metastases for the majority of malignant tumours. However, the exact incidence of bone metastases is unknown. Bone metastases have an important socio-economic impact, and due to the enhancement of the overall survivorship, their incidence is increasing. Malignant neoplasms such as lung, thyroid, renal cancer, multiple myeloma, and melanoma often metastasize to the bone. Bone metastases commonly localize to the spinal column, pelvis, shoulder, and distal femur. The proper treatment for painful skeletal metastases is still unknown. Hence, the purpose of this review of the literature was to update current evidence concerning the aetiogenesis, biological behaviour, and treatment algorithms for painful skeletal metastases.

A case of ROS1-rearranged lung adenocarcinoma with osteoblastic bone metastasis

A 53-year-old woman was referred to our hospital for detailed examination of abnormal chest shadows recognized on CT imaging. Transbronchial lung biopsy of a right S6 nodular shadow led to a diagnosis of lung adenocarcinoma. FDG-PET-CT showed FDG accumulation in the Th11 and L2 vertebral bodies and osteoblastic bone lesions. Since osteoblastic bone metastasis in lung cancer is extremely rare, CT-guided bone biopsy was performed. The tumor was diagnosed as ROS1-rearranged lung adenocarcinoma, for which crizotinib was administered, which led to improvement of both the primary and metastatic lesions. We report here a rare case of ROS1-rearranged lung adenocarcinoma with osteoblastic bone metastasis of lung cancer.

Zoledronate Inhibits Osteoclast Differentiation via Suppressing Vascular Endothelial Growth Factor Receptor 2 Expression

Bisphosphonate-related osteonecrosis of the jaw (ONJ) is a major oral complication; however, its pathogenesis remains unclear. Impairment of osteoclast differentiation by bisphosphonates may be associated with the pathogenesis of ONJ. In our previous study, we reported that the expression of the gene encoding nuclear factor of activated T cells c1 (NFATc1), a known osteoclast differentiation marker, was significantly silenced by zoledronate, a bisphosphonate, in mouse osteoclast precursor cells (mOCPCs) using cDNA microarray. In the present study, the expression value of the NFATc1 gene was regarded as a cut-off and genes whose expression value was significantly decreased compared with that of the NFATc1 gene were extracted in mOCPCs. For validation, CD11b-positive (CD11b+) cells were used, which were purified from human peripheral blood mononuclear cells as human OCPCs. A total of 19 genes were identified; sequential expression analysis revealed that the gene encoding vascular endothelial growth factor receptor 2 (VEGFR2) was frequently silenced by zoledronate in CD11b+ cells. Furthermore, the number of tartrate-resistant acid phosphatase-positive multinucleated cells was decreased by VEGFR2 suppression using a VEGFR2 neutralizing antibody. Zoledronate inhibits human osteoclast differentiation via suppressing VEGFR2 expression. These results suggest that low expression of VEGFR2 in OCPCs may be involved in the pathogenesis of zoledronate-induced ONJ. The understanding of the role of VEGFR2 on bone remodeling is important to elucidate the pathogenesis of bisphosphonate-related ONJ.

Metal-Organic Framework Nanoparticles for Ameliorating Breast Cancer-Associated Osteolysis

Breast cancer metastases to bone poses a significant challenge for the administration of treatment strategies. The bone microenvironment, metastatic tumor cells, osteoclasts, and tumor-associated macrophages (TAMs) all play crucial and synergistic roles in creating a favorable environment for the proliferation, progression, and survival of the metastatic tumor, which in turn induces osteoclast-mediated bone destruction. In this study, we functionalized immunostimulatory cytosine-phosphate-guanosine (CpG)-loaded metal-organic framework (MOF) nanoparticles with bone targeting capabilities by surface modification with FDA approved antiresorptive bisphosphonate, zoledronic acid (ZOL). The functionalized bone targeting immunostimulatory MOF (BT-isMOF) nanoparticles demonstrates strong binding to calcium phosphate in vitro and exhibits specific targeting and accumulation in bone tissues in vivo. In vitro cellular and biochemical analyses demonstrated that the BT-isMOF nanoparticles could potently inhibit osteoclast formation and concomitantly induce macrophages polarization toward the M1 pro-inflammatory phenotype. Finally, using the intratibial murine model of breast cancer bone metastasis, we showed that the administration of BT-isMOF nanoparticles significantly suppressed osteoclast-mediated bone destruction and enhanced polarization of tumor-resident macrophages to M1 phenotype. Together, our data provides promising evidence for the potential therapeutic application of the BT-isMOF nanoparticles in the treatment of breast cancer bone metastases.

Elevated Expression of Lumican in Lung Cancer Cells Promotes Bone Metastasis through an Autocrine Regulatory Mechanism

Background: The microarray analysis of whole-genome expression indicated that the gene encoding the protein lumican, which is associated with extracellular matrix (ECM) interaction, was highly expressed in osteotropic lung cancer cell lines with an enhanced capacity of bone metastasis. Methods: The expression of lumican in the osteotropic lung cancer cells was downregulated, and the in vitro migration, invasion, and adhesion of cancer cells to ECM components, and the in vivo bone metastasis capacity of these cells were examined. Exogenous lumican was provided to study the autocrine regulation mechanism of lumican in the bone metastasis of lung cancer cells. Results: Transfection with lumican-specific short hairpin RNA (shRNA) in the osteotropic lung cancer cells reduced the establishment of in vivo bone metastasis, but not lung metastasis. Reduction in the expression of lumican also decreased the attachment of lung osteotropic cancer cells to several components of the ECM and suppressed cell migration and invasion in vitro. Exogenous lumican restored these reduced capacities of lumican knockdown cells and promoted the seeding of lung cancer cells in the bone microenvironment. Conclusions: These results suggested that lumican promotes the metastasis of lung cancer cells to the bones via an autocrine regulatory mechanism, and blocking this interaction may provide a new therapeutic approach to reduce bone metastasis in cases of lung cancer.

A Novel, Tumor-Induced Osteoclastogenesis Pathway Insensitive to Denosumab but Interfered by Cannabidiol

Bone metabolism is strictly regulated, and impaired regulation caused by hormonal imbalances induces systemic bone loss. Local bone loss caused by tumor invasion into bone is suggested to be induced by the generation of cytokines, which affect bone metabolism, by tumor cells. The major cause of systemic and local bone losses is excess bone resorption by osteoclasts, which differentiate from macrophages by receptor activator of nuclear factor kappa-B ligand (RANKL) or tumor necrosis factor-alpha (TNF-α). We previously found a novel pathway for tumor-induced osteoclastogenesis targeting osteoclast precursor cells (OPCs). Tumor-induced osteoclastogenesis was resistant to RANKL and TNF-α inhibitors. In the present study, we confirmed that exosomes derived from oral squamous cell carcinoma (OSCC) cells induced osteoclasts from OPCs. We also showed that the depletion of exosomes from culture supernatants of OSCC cells partially interfered with osteoclastogenesis, and cannabidiol, an innoxious cannabinoid without psychotropic effects, almost completely suppressed tumor-induced osteoclastogenesis. Osteoclastogenesis and its interference by cannabidiol were independent of the expression of nuclear factor of T cell c1 (NFATc1). These results show that osteoclastogenesis induced by OSCC cells targeting OPCs is a novel osteoclastogenic pathway independent of NFATc1 expression that is partially caused by tumor-derived exosomes and suppressed by cannabidiol.

A Diet Rich in Fish Oil and Leucine Ameliorates Hypercalcemia in Tumour-Induced Cachectic Mice

Background: Dietary supplementation with leucine and fish oil rich in omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) has previously been shown to reduce cachexia-related outcomes in C26 tumour-bearing mice. To further explore associated processes and mechanisms we investigated changes in plasma Ca²⁺ levels, the involvement of parathyroid hormone related protein (PTHrP), and its possible interactions with cyclooxygenase 2 (COX-2). Methods: CD2F1 mice were subcutaneously inoculated with C26 adenocarcinoma cells or sham treated and divided in: (1) controls, (2) tumour-bearing controls, and (3) tumour-bearing receiving experimental diets. After 20 days, body and organ masses and total plasma Ca²⁺ levels were determined. Furthermore, effects of DHA, EPA and leucine on production of PTHrP were studied in cultured C26 cells. Results: The combination of leucine and fish oil reduced tumour-associated hypercalcemia. Plasma Ca²⁺ levels negatively correlated with carcass mass and multiple organ masses. DHA was able to reduce PTHrP production by C26 cells in vitro. Results indicate that this effect occurred independently of COX-2 inhibition. Conclusion: Our results suggest that cancer-related hypercalcemia may be ameliorated by a nutritional intervention rich in leucine and fish oil. The effect of fish oil possibly relates to a DHA-induced reduction of PTHrP excretion by the tumour.

Strontium enhances proliferation and osteogenic behavior of bone marrow stromal cells of mesenchymal and ectomesenchymal origins in vitro

Obejective

To investigate the effect of increasing Strontium (Sr) concentrations on the growth and osteogenic behavior of human bone marrow stromal cells (BMSCs) from mesenchymal (i.e., fibula) and ectomesenchymal (i.e., mandible) embryonic origins.

Materials and methods

Fibula and mandible BMSCs were cultured in media without (Ctrl) or with Sr in four diverse concentrations: Sr1, 11.3 × 10⁻³ mg/L, human seric physiological level; Sr2, 13 mg/L, human seric level after strontium ranelate treatment; Sr3, 130 mg/L, and Sr4, 360 mg/L. Proliferation rate (1, 3, and 7 days), osteogenic behavior (alkaline phosphatase [ALP] activity, 7 and 14 days; expression of osteogenic genes (ALP, osteopontin, and osteocalcin at 7, 14, and 21 days), and formation of mineralized nodules (14 and 21 days) of the BMSCs were assessed. Data was compared group‐ and period‐wise using analysis of variance tests.

Results

Fibula and mandible BMSCs cultured with Sr4 showed increased proliferation rate, and osteocalcin and osteopontin gene expression together with more evident formation of mineralized nodules, compared all other Sr concentrations. For both cell populations, Sr4 led to lower ALP activity, and ALP gene expression, compared with the other Sr concentrations.

Conclusion

BMSCs from mesenchymal (i.e., fibula) and ectomesenchymal (i.e., mandible) embryonic origins showed increased cellular proliferation and osteogenic behavior when cultured with Sr4, in vitro.

Diffuse osteosclerosis as a presentation of recurrent breast cancer: role of endothelin 1

We report a 46-yr-old woman with a history of breast cancer who presented with diffuse myalgias, bone pain, and osteosclerosis. She was found to have recurrent breast cancer producing endothelin-1.

INTRODUCTION

Acquired osteosclerosis can be caused by various disorders. Endothelin -1 is believed to contribute to osteosclerosis caused by breast cancer.

METHODS

Although the bone marrow biopsy did not reveal breast cancer, she developed skin lesions consistent with metastatic breast cancer. She ultimately died from progressive disease. At autopsy immunohistochemistry for endothelin-1 was performed on a section from the L5 vertebral body.

RESULTS

The section from the L5 vertebral body showed small foci of cells consistent with metastatic carcinoma and a prominent sclerotic response. Immunohistochemistry for endothelin-1 was strongly positive.

CONCLUSIONS

Recurrent breast cancer may present with diffuse osteosclerosis. Endothelin-1 may be a paracrine factor responsible for increased bone formation and osteosclerosis.

The Bone Extracellular Matrix as an Ideal Milieu for Cancer Cell Metastases

Bone is a preferential site for cancer metastases, including multiple myeloma, prostate, and breast cancers.The composition of bone, especially the extracellular matrix (ECM), make it an attractive site for cancer cell colonization and survival. The bone ECM is composed of living cells embedded within a matrix composed of both organic and inorganic components. Among the organic components, type I collagen provides the tensile strength of bone. Inorganic components, including hydroxyapatite crystals, are an integral component of bone and provide bone with its rigidity. Under normal circumstances, two of the main cell types in bone, the osteoblasts and osteoclasts, help to maintain bone homeostasis and remodeling through cellular communication and response to biophysical signals from the ECM. However, under pathological conditions, including osteoporosis and cancer, bone remodeling is dysregulated. Once in the bone matrix, disseminated tumor cells utilize normal products of bone remodeling, such as collagen type I, to fuel cancer cell proliferation and lesion outgrowth. Models to study the complex interactions between the bone matrix and metastatic cancer cells are limited. Advances in understanding the interactions between the bone ECM and bone metastatic cancer cells are necessary in order to both regulate and prevent metastatic cancer cell growth in bone.

A Selective FGFR inhibitor AZD4547 suppresses RANKL/M-CSF/OPG-dependent ostoclastogenesis and breast cancer growth in the metastatic bone microenvironment

Aberrant activation of fibroblast growth factor receptor (FGFR) signalling contributes to progression and metastasis of many types of cancers including breast cancer. Accordingly, FGFR targeted tyrosine kinase inhibitors (TKIs) are currently under development. However, the efficacy of FGFR TKIs in the bone microenvironment where breast cancer cells most frequently metastasize and also where FGFR is biologically active, has not been clearly investigated. We investigated the FGFR-mediated interactions among cancer and the bone microenvironment stromal cells (osteoblasts and osteoclasts), and also the effects of FGFR inhibition in bone metastasis. We showed that addition of culture supernatant from the MDA-MB-134-VI FGFR-amplified breast cancer cells-activated FGFR siganalling in osteoblasts, including increased expression of RANKL, M-CSF, and osteoprotegerin (OPG). Further in vitro analyses showed that AZD4547, an FGFR TKI currently in clinical trials for breast cancer, decreased RANKL and M-CSF, and subsequently RANKL and M-CSF-dependent osteoclastogenesis of murine bone marrow monocytes. Moreover, AZD4547 suppressed osteoclastogenesis and tumor-induced osteolysis in an orthotopic breast cancer bone metastasis mouse model using FGFR non-amplified MDA-MB-231 cells. Collectively, our results support that FGFR inhibitors inhibit the bone microenvironment stromal cells including osteoblasts and osteoclasts, and effectively suppress both tumor and stromal compartments of bone metastasis.

The Emerging Role of Osteocytes in Cancer in Bone

Advances in the last decade have established the osteocyte, the most abundant cell in bone, as a dynamic and multifunctional cell capable of controlling bone homeostasis by regulating the function of both osteoblasts and osteoclasts. In addition, accumulating evidence demonstrates that osteocyte function is altered in several skeletal disorders, and targeting osteocytes and their derived factors improves skeletal health. Despite the remarkable progress in our understanding of osteocyte biology, there has been a paucity of information regarding the role of osteocytes in the progression of cancer in bone. Exciting, recent discoveries suggest that tumor cells communicate with osteocytes to generate a microenvironment that supports the growth and survival of cancer cells and stimulates bone destruction. This review features these novel findings and discussions regarding the impact of chemotherapy on osteocyte function and the potential of targeting osteocytes for the treatment of cancer in bone. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Prostate Osteoblast-Like Cells: A Reliable Prognostic Marker of Bone Metastasis in Prostate Cancer Patients

The main aim of this study was to investigate the putative association among the presence of prostate cancer cells, defined as prostate osteoblast-like cells (POLCs), and showing the expression of typical morphological and molecular characteristics of osteoblasts, the development of bone metastasis within 5 years of diagnosis, and the uptake of 18F-choline evaluated by PET/CT analysis. To this end, prostate biopsies (n = 110) were collected comprising 44 benign lesions and 66 malignant lesions. Malignant lesions were further subdivided into two groups: biopsies from patients that had clinical evidence of bone metastasis (BM+, n = 23) and biopsies from patients that did not have clinical evidence of bone metastasis within 5 years (BM-, n = 43). Paraffin serial sections were obtained from each specimen to perform histological classifications and immunohistochemical (IHC) analysis. Small fragments of tissue were used to perform ultrastructural and microanalytical investigations. IHC demonstrated the expression of markers of epithelial-to-mesenchymal transition (VIM), bone mineralization, and osteoblastic differentiation (BMP-2, PTX-3, RUNX2, RANKL, and VDR) in prostate lesions characterized by the presence of calcium-phosphate microcalcifications and high metastatic potential. Ultrastructural studies revealed the presence of prostate cancer cells with osteoblast phenotype close to microcalcifications. Noteworthy, PET/CT analysis showed higher uptake of 18F-choline in BM+ lesions with high positivity (≥300/500 cells) for RUNX2 and/or RANKL immunostaining. Although these data require further investigations about the molecular mechanisms of POLCs generation and role in bone metastasis, our study can open new and interesting prospective in the management of prostate cancer patients. The presence of POLCs along with prostate microcalcifications may become negative prognostic markers of the occurrence of bone metastases.

Cancer Metastases to Bone: Concepts, Mechanisms, and Interactions with Bone Osteoblasts

The skeleton is a unique structure capable of providing support for the body. Bone resorption and deposition are controlled in a tightly regulated balance between osteoblasts and osteoclasts with no net bone gain or loss. However, under conditions of disease, the balance between bone resorption and deposition is upset. Osteoblasts play an important role in bone homeostasis by depositing new bone osteoid into resorption pits. It is becoming increasingly evident that osteoblasts additionally play key roles in cancer cell dissemination to bone and subsequent metastasis. Our laboratory has evidence that when osteoblasts come into contact with disseminated breast cancer cells, the osteoblasts produce factors that initially reduce breast cancer cell proliferation, yet promote cancer cell survival in bone. Other laboratories have demonstrated that osteoblasts both directly and indirectly contribute to dormant cancer cell reactivation in bone. Moreover, we have demonstrated that osteoblasts undergo an inflammatory stress response in late stages of breast cancer, and produce inflammatory cytokines that are maintenance and survival factors for breast cancer cells and osteoclasts. Advances in understanding interactions between osteoblasts, osteoclasts, and bone metastatic cancer cells will aid in controlling and ultimately preventing cancer cell metastasis to bone.

Autoregulation of RANK ligand in oral squamous cell carcinoma tumor cells

Oral squamous cell carcinoma (OSCC) is the most common malignancy among oral cancers and shows potent activity for local bone invasion. Receptor activator of nuclear factor κB (RANK) ligand (RANKL) is critical for bone-resorbing osteoclast formation. We previously demonstrated that OSCC tumor cells express high levels of RANKL. In this study, confocal microscopy demonstrated RANKL specific receptor, RANK expression in OSCC tumor cell lines (SCC1, SCC12, and SCC14a). We also confirmed the expression of RANK and RANKL in primary human OSCC tumor specimens. However, regulatory mechanisms of RANKL expression and a functional role in OSCC tumor progression are unclear. Interestingly, we identified that RANKL expression is autoregulated in OSCC tumor cells. The RANKL specific inhibitor osteoprotegerin (OPG) treatment to OSCC cells inhibits autoregulation of RANKL expression. Further, we showed conditioned media from RANKL CRISPR-Cas9 knockout OSCC cells significantly decreased osteoclast formation and bone resorption activity. In addition, RANKL increases OSCC tumor cell proliferation. RANKL treatment to OSCC cells demonstrated a dose-dependent increase in RANK intracellular adaptor protein, TRAF6 expression, and activation of IKK and IκB signaling molecules. We further identified that transcription factor NFATc2 mediates autoregulation of RANKL expression in OSCC cells. Thus, our results implicate RANKL autoregulation as a novel mechanism that facilitates OSCC tumor cell growth and osteoclast differentiation/bone destruction.

Loss of RUNX3 expression inhibits bone invasion of oral squamous cell carcinoma

High recurrence and lower survival rates in patients with oral squamous cell carcinoma (OSCC) are associated with its bone invasion. We identified the oncogenic role of RUNX3 during bone invasion by OSCC. Tumor growth and the generation of osteolytic lesions were significantly inhibited in mice that were subcutaneously inoculated with RUNX3-knockdown human OSCC cells. RUNX3 knockdown enhanced TGF-β-induced growth arrest and inhibited OSCC cell migration and invasion in the absence or presence of transforming growth factor-β (TGF-β), a major growth factor abundant in the bone microenvironment. RUNX3 knockdown induced cell cycle arrest at the G1 and G2 phases and promoted G2 arrest by TGF-β in Ca9.22 OSCC cells. RUNX3 knockdown also inhibited both the basal and TGF-β-induced epithelial-to-mesenchymal transition by increasing E-cadherin expression and suppressing the nuclear translocation of β-catenin. In addition, the expression and TGF-β-mediated induction of parathyroid hormone-related protein (PTHrP), one of key osteolytic factors, was blocked in RUNX3-knockdown OSCC cells. Furthermore, treating human osteoblastic cells with conditioned medium derived from RUNX3-knockdown OSCC cells reduced the receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin ratio compared with treatment with conditioned medium from RUNX3-expressing cells. These findings indicate that RUNX3 expression in OSCC cells contributes to their bone invasion and the resulting osteolysis by inducing their malignant behaviors and production of osteolytic factors. RUNX3 alone or in combination with TGF-β and PTHrP may be a useful predictive biomarker and therapeutic target for bone invasion by oral cancer.

RON kinase: A target for treatment of cancer-induced bone destruction and osteoporosis

Bone destruction occurs in aging and numerous diseases, including osteoporosis and cancer. Many cancer patients have bone osteolysis that is refractory to state-of-the-art treatments, which block osteoclast activity with bisphosphonates or by inhibiting the receptor activator of nuclear factor κB ligand (RANKL) pathway. We previously showed that macrophage-stimulating protein (MSP) signaling, which is elevated in about 40% of breast cancers, promotes osteolytic bone metastasis by activation of the MSP signaling pathway in tumor cells or in the bone microenvironment. We show that MSP signals through its receptor, RON tyrosine kinase, expressed on host cells, to activate osteoclasts directly by a previously undescribed pathway that is complementary to RANKL signaling and converges on proto-oncogene, non-receptor tyrosine kinase SRC (SRC). Genetic or pharmacologic inhibition of RON kinase blocked cancer-mediated bone destruction and osteoporosis in several mouse models. Furthermore, the RON kinase inhibitor BMS-777607/ASLAN002 altered markers of bone turnover in a first-in-human clinical cancer study, indicating the inhibitor's potential for normalizing bone loss in patients. These findings uncover a new therapeutic target for pathogenic bone loss and provide a rationale for treatment of bone destruction in various diseases with RON inhibitors.

Understanding the Progression of Bone Metastases to Identify Novel Therapeutic Targets

Bone is one of the most preferential target site for cancer metastases, particularly for prostate, breast, kidney, lung and thyroid primary tumours. Indeed, numerous chemical signals and growth factors produced by the bone microenvironment constitute factors promoting cancer cell invasion and aggression. After reviewing the different theories proposed to provide mechanism for metastatic progression, we report on the gene expression profile of bone-seeking cancer cells. We also discuss the cross-talk between the bone microenvironment and invading cells, which impacts on the tumour actions on surrounding bone tissue. Lastly, we detail therapies for bone metastases. Due to poor prognosis for patients, the strategies mainly aim at reducing the impact of skeletal-related events on patients' quality of life. However, recent advances have led to a better understanding of molecular mechanisms underlying bone metastases progression, and therefore of novel therapeutic targets.

CT evaluation of underlying bone sclerosis in patients with oral squamous cell carcinoma: A preliminary retrospective study

Purpose

Underlying bone sclerosis is frequently observed in clinical settings when oral squamous cell carcinoma (OSCC) invades the jaw bone. The aim of this study was to assess the prevalence and characteristics of underlying bone sclerosis in patients with OSCC.

Materials and Methods

We retrospectively reviewed the computed tomographic (CT) images of 131 patients who underwent mandibulectomy between January 2012 and December 2015 to treat OSCC. The presence, degree, and extent of underlying bone sclerosis were assessed on CT images and correlated with the following imaging patterns of bone invasion: cortical invasion, medullary invasion with a smooth margin, and medullary invasion with an irregular margin. The chi-square test was used to determine the relationships between the variables.

Results

The prevalence of underlying bone sclerosis on CT images was 70.1% (47 of 67). The prevalence was 85.7% (42 of 49) in patients with medullary invasion, but it was 27.8% (5 of 18) in patients with only cortical invasion, indicating a significant increase in the prevalence of underlying bone sclerosis in patients with medullary invasion (P<.05). Aggressive patterns of bone invasion were associated with increases in the degree and extent of the underlying bone sclerosis (P<.05).

Conclusion

More than two-thirds of OSCC cases with bone invasion showed underlying bone sclerosis. On CT images, reactive sclerosis in the remaining margin of the alveolar bone should not be used as the primary means to differentiate periodontal inflammatory lesions from those resulting from OSCC.

Roles of VEGF-Flt-1 signaling in malignant behaviors of oral squamous cell carcinoma

Background

Vascular endothelial growth factor (VEGF) is a highly specific signaling protein for vascular endothelial cells that plays a critical role in tumor growth and invasion through angiogenesis, and may contribute to cell migration and activation of pre-osteoclasts, osteoclasts and some tumor cells.

Objectives

We aimed to clarify the detailed roles of VEGF-Flt-1 signaling in bone invasion of oral squamous cell carcinoma (OSCC) cells.

Results

Forty-two (42) of 54 cases with gingival SCC (77.8%) strongly expressed VEGF, and had a significantly increased number of Flt-1+ osteoclasts (p<0.01) and more aggressive bone invasion (p<0.05). PlGF, a ligand of Flt-1, induced osteoclastogenesis in single culture of bone marrow cells (BMCs), and inhibition of Flt-1-signaling by VEGF tyrosine kinase inhibitor and It’s down stream (Akt and ERK1/2) inhibitos reduced osteoclastogenesis in PlGF-stimulated BMCs (p<0.01). In molecular level, PlGF stimulation significantly upregulated RANKL expression in Flt-1-expressing HSC2 cells via phosphorylation of Akt and ERK1/2. In the co-culture of VEGF-producing HSC2 cells and BMCs, number of TRAP-positive osteoclasts markedly increased (p<0.01). The osteoclastogenesis was significantly inhibited by RANKL-neutralizing antibody (p<0.01) as well as by VEGF tyrosine kinase inhibitor (p<0.01) and it’s downstream (Akt and ERK1/2) inhibitors (p<0.01, p<0.05, respectively).

Conclusion

VEGF-Flt-1 signaling induces osteoclastogenesis in OSCC through two possible ways: 1) VEGF produced from OSCC cells can directly stimulate the Flt-1 pathway in preosteoclasts to induce migration to future bone resorbing area and differentiation into osteoclasts, and 2) VEGF-Flt-1 signaling upregulates RANKL expression in OSCC cells, which indirectly leads to osteoclast differentiation. Therefore, blocking of the VEGF-Flt-1 signaling may help inhibit bone invasion of OSCC.

Diagnostic methods for detection of bone metastases

Skeletal metastases are severe complications in the course of cancer, and they indicate a worse prognosis. The use of modern imaging techniques allows rapid diagnosis of bone metastases. Properly selected diagnostic imaging (scintigraphy, positron emission tomography, whole body MRI) allows us to evaluate the number of metastatic foci in the skeletal system. Complementary imaging examinations (X-ray, computed tomography, magnetic resonance imaging) determine the extent of metastasis and its character: osteolytic, osteoblast, mixed). Hypercalcaemia is a symptom of low specificity for metastatic bone disease (a result of osteolysis); nevertheless, it is a significant complication in oncological treatment and worsens the prognosis of the patient. A biopsy is the final stage of the diagnostic process, which allows us to assess cell and tissue changes. Guided biopsies are performed under the control of musculoskeletal imaging methods (CT, MRI) and they are the most promising tools in bone metastases diagnosis. The development of guided biopsy techniques has led to the conclusion that they should be standard in diagnosing bone metastases. Liquid biopsy (LB) seems to be the most promising diagnostic method for detection of bone metastases. LB based on tumour-specific DNA mutation gives an opportunity for early detection and assessment of the molecular heterogeneity of the overall disease.

Design of polyaspartic acid peptide-poly (ethylene glycol)-poly (ε-caprolactone) nanoparticles as a carrier of hydrophobic drugs targeting cancer metastasized to bone

Treatment of cancer metastasized to bone is still a challenge due to hydrophobicity, instability, and lack of target specificity of anticancer drugs. Poly (ethylene glycol)-poly (ε-caprolactone) polymer (PEG-PCL) is an effective, biodegradable, and biocompatible hydrophobic drug carrier, but lacks bone specificity. Polyaspartic acid with eight peptide sequences, that is, (Asp)₈, has a strong affinity to bone surface. The aim of this study was to synthesize (Asp)₈-PEG-PCL nanoparticles as a bone-specific carrier of hydrophobic drugs to treat cancer metastasized to bone. ¹H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and transmission electron microscopy data showed that (Asp)₈-PEG-PCL nanoparticles (size 100 nm) were synthesized successfully. (Asp)₈-PEG-PCL nanoparticles did not promote erythrocyte aggregation. Fluorescence microscopy showed clear uptake of Nile red-loaded (Asp)₈-PEG-PCL nanoparticles by cancer cells. (Asp)₈-PEG-PCL nanoparticles did not show cytotoxic effect on MG63 and human umbilical vein endothelial cells at the concentration of 10-800 μg/mL. (Asp)₈-PEG-PCL nanoparticles bound with hydroxyapatite 2-fold more than PEG-PCL. Intravenously injected (Asp)₈-PEG-PCL nanoparticles accumulated 2.7-fold more on mice tibial bone, in comparison to PEG-PCL. Curcumin is a hydrophobic anticancer drug with bone anabolic properties. Curcumin was loaded in the (Asp)₈-PEG-PCL. (Asp)₈-PEG-PCL showed 11.07% loading capacity and 95.91% encapsulation efficiency of curcumin. The curcumin-loaded (Asp)₈-PEG-PCL nanoparticles gave sustained release of curcumin in high dose for >8 days. The curcumin-loaded (Asp)₈-PEG-PCL nanoparticles showed strong antitumorigenic effect on MG63, MCF7, and HeLa cancer cells. In conclusion, (Asp)₈-PEG-PCL nanoparticles were biocompatible, permeable in cells, a potent carrier, and an efficient releaser of hydrophobic anticancer drug and were bone specific. The curcumin-loaded (Asp)₈-PEG-PCL nanoparticles showed strong antitumorigenic ability in vitro. Therefore, (Asp)₈-PEG-PCL nanoparticles could be a potent carrier of hydrophobic anticancer drugs to treat the cancer metastasized to bone.

Hypercalcemia of Malignancy in Thymic Carcinoma: Evolving Mechanisms of Hypercalcemia and Targeted Therapies

Here we describe, to our knowledge, the first case where an evolution of mechanisms responsible for hypercalcemia occurred in undifferentiated thymic carcinoma and discuss specific management strategies for hypercalcemia of malignancy (HCM). Case Description. We report a 26-year-old male with newly diagnosed undifferentiated thymic carcinoma associated with HCM. Osteolytic metastasis-related hypercalcemia was presumed to be the etiology of hypercalcemia that responded to intravenous hydration and bisphosphonate therapy. Subsequently, refractory hypercalcemia persisted despite the administration of bisphosphonates and denosumab indicative of refractory hypercalcemia. Elevated 1,25-dihydroxyvitamin D was noted from the second admission with hypercalcemia responding to glucocorticoid administration. A subsequent PTHrP was also elevated, further supporting multiple mechanistic evolution of HCM. The different mechanisms of HCM are summarized with the role of tailoring therapies based on the particular mechanism underlying hypercalcemia discussed. Conclusion. Our case illustrates the importance of a comprehensive initial evaluation and reevaluation of all identifiable mechanisms of HCM, especially in the setting of recurrent and refractory hypercalcemia. Knowledge of the known and possible evolution of the underlying mechanisms for HCM is important for application of specific therapies that target those mechanisms. Specific targeting therapies to the underlying mechanisms for HCM could positively affect patient outcomes.

The Bone Microenvironment: a Fertile Soil for Tumor Growth

Bone metastatic disease remains a significant and frequent problem for cancer patients that can lead to increased morbidity and mortality. Unfortunately, despite decades of research, bone metastases remain incurable. Current studies have demonstrated that many properties and cell types within the bone and bone marrow microenvironment contribute to tumor-induced bone disease. Furthermore, they have pointed to the importance of understanding how tumor cells interact with their microenvironment in order to help improve both the development of new therapeutics and the prediction of response to therapy.

Three-Dimensional Mechanical Loading Modulates the Osteogenic Response of Mesenchymal Stem Cells to Tumor-Derived Soluble Signals

Dynamic mechanical loading is a strong anabolic signal in the skeleton, increasing osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs) and increasing the bone-forming activity of osteoblasts, but its role in bone metastatic cancer is relatively unknown. In this study, we integrated a hydroxyapatite-containing three-dimensional (3D) scaffold platform with controlled mechanical stimulation to investigate the effects of cyclic compression on the interplay between breast cancer cells and BM-MSCs as it pertains to bone metastasis. BM-MSCs cultured within mineral-containing 3D poly(lactide-co-glycolide) (PLG) scaffolds differentiated into mature osteoblasts, and exposure to tumor-derived soluble factors promoted this process. When BM-MSCs undergoing osteogenic differentiation were exposed to conditioned media collected from mechanically loaded breast cancer cells, their gene expression of osteopontin was increased. This was further enhanced when mechanical compression was simultaneously applied to BM-MSCs, leading to more uniformly deposited osteopontin within scaffold pores. These results suggest that mechanical loading of 3D scaffold-based culture models may be utilized to evaluate the role of physiologically relevant physical cues on bone metastatic breast cancer. Furthermore, our data imply that cyclic mechanical stimuli within the bone microenvironment modulate interactions between tumor cells and BM-MSCs that are relevant to bone metastasis.

Prostate cancer metastasis: roles of recruitment and reprogramming, cell signal network and three-dimensional growth characteristics

Prostate cancer (PCa) metastasizes to bone and soft tissues, greatly decreasing quality of life, causing bone pain, skeletal complications, and mortality in PCa patients. While new treatment strategies are being developed, the molecular and cellular basis of PCa metastasis and the “cross-talk” between cancer cells and their microenvironment and crucial cell signaling pathways need to be successfully dissected for intervention. In this review, we introduce a new concept of the mechanism of PCa metastasis, the recruitment and reprogramming of bystander and dormant cells (DCs) by a population of metastasis-initiating cells (MICs). We provide evidence that recruited and reprogrammed DCs gain MICs phenotypes and can subsequently metastasize to bone and soft tissues. We show that MICs can also recruit and reprogram circulating tumor cells (CTCs) and this could contribute to cancer cell evolution and the acquisition of therapeutic resistance. We summarize relevant molecular signaling pathways, including androgen receptors (ARs) and their variants and growth factors (GFs) and cytokines that could contribute to the predilection of PCa for homing to bone and soft tissues. To understand the etiology and the biology of PCa and the effectiveness of therapeutic targeting, we briefly summarize the animal and cell models that have been employed. We also report our experience in the use of three-dimensional (3-D) culture and co-culture models to understand cell signaling networks and the use of these attractive tools to conduct drug screening exercises against already-identified molecular targets. Further research into PCa growth and metastasis will improve our ability to target cancer metastasis more effectively and provide better rationales for personalized oncology.

Macrophages: Their Emerging Roles in Bone

Macrophages are present in nearly all tissues and are critical for development, homeostasis, and regeneration. Resident tissue macrophages of bone, termed osteal macrophages, are recently classified myeloid cells that are distinct from osteoclasts. Osteal macrophages are located immediately adjacent to osteoblasts, regulate bone formation, and play diverse roles in skeletal homeostasis. Genetic or pharmacological modulation of macrophages in vivo results in significant bone phenotypes, and these phenotypes depend on which macrophage subsets are altered. Macrophages are also key mediators of osseous wound healing and fracture repair, with distinct roles at various stages of the repair process. A central function of macrophages is their phagocytic ability. Each day, billions of cells die in the body and efferocytosis (phagocytosis of apoptotic cells) is a critical process in both clearing dead cells and recruitment of replacement progenitor cells to maintain homeostasis. Recent data suggest a role for efferocytosis in bone biology and these new mechanisms are outlined. Finally, although macrophages have an established role in primary tumors, emerging evidence suggests that macrophages in bone support cancers which preferentially metastasize to the skeleton. Collectively, this developing area of osteoimmunology raises new questions and promises to provide novel insights into pathophysiologic conditions as well as therapeutic and regenerative approaches vital for skeletal health.

IRE1α/XBP1-mediated branch of the unfolded protein response regulates osteoclastogenesis

The unfolded protein response (UPR) is a cellular adaptive mechanism that is activated in response to the accumulation of unfolded proteins in the endoplasmic reticulum. The inositol-requiring protein-1α/X-box-binding protein-mediated (IRE1α/XBP1-mediated) branch of the UPR is highly conserved and has also been shown to regulate various cell-fate decisions. Herein, we have demonstrated a crucial role for the IREα/XBP1-mediated arm of the UPR in osteoclast differentiation. Using murine models, we found that the conditional abrogation of IRE1α in bone marrow cells increases bone mass as the result of defective osteoclastic bone resorption. In osteoclast precursors, IRE1α was transiently activated during osteoclastogenesis, and suppression of the IRE1α/XBP1 pathway in these cells substantially inhibited the formation of multinucleated osteoclasts in vitro. We determined that XBP1 directly binds the promoter and induces transcription of the gene encoding the master regulator of osteoclastogenesis nuclear factor of activated T cells cytoplasmic 1 (NFATc1). Moreover, activation of IRE1α was partially dependent on Ca2+ oscillation mediated by inositol 1,4,5-trisphosphate receptors 2 and 3 (ITPR2 and ITPR3) in the endoplasmic reticulum, as pharmacological inhibition or deletion of these receptors markedly decreased Xbp1 mRNA processing. The present study thus reveals an intracellular pathway that integrates the UPR and osteoclast differentiation through activation of the IRE1α/XBP1 pathway.

Interaction between bone marrow stromal cells and neuroblastoma cells leads to a VEGFA-mediated osteoblastogenesis

The potential role of osteoblasts in bone and bone marrow (BM) metastases in neuroblastoma (NBL) remains unclear. In this study, we examined the effect of NBL cells on the osteoblastic differentiation of BM-derived mesenchymal stromal cells (BMMSC). We show that the presence of NBL cells enhanced the osteoblastic differentiation of BMMSC driven by bone morphogenetic protein (BMP)-4, in the absence of any effect on NBL cell proliferation. Expression profiles of BMMSC driven toward osteoblastic differentiation revealed an increase in vascular endothelial growth factor A (Vegfa) expression in the presence of NBL cells. We demonstrated that NBL cells increased BMMSC-derived VEGFA mRNA and protein and that this was enhanced by BMP-4. However, in similar conditions, neither the addition of an mVEGFA blocking antibody nor exogenous recombinant (r) mVEGFA affected osteoblastic differentiation. In contrast, siRNA- mediated knock-down of VEGFA in BMMSC prevented osteoblastic differentiation in BMP-4-treated cocultures, an effect that was not reversed in the presence of rmVEGFA. An analysis of murine bones injected with hNBL cells revealed an increase of mVEGFA producing cells near tumor cells concomitantly with an increase in Vegfa and Runx2 mRNA. This coincided with an increase in osteoclasts, in Rankl/Opg mRNA ratio and with the formation of osteolytic lesions. Thus NBL cells promote osteoblastogenesis in the BM by increasing VEGFA expression in BMMSC. Our study provides a new insight into the role of VEGFA in NBL metastases by pointing to the role of stroma-derived intracrine VEGFA in osteoblastogenesis.

The novel IκB kinase β inhibitor IMD-0560 prevents bone invasion by oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) cells display significantly augmented nuclear factor-κB (NF-κB) activity, and inhibiting this activity suppresses malignant tumor characteristics. Thus, we evaluated the effect of IMD-0560, a novel inhibitor of IκB kinase (IKK) β that is under assessment in a clinical trial of rheumatoid arthritis, on bone invasion by the mouse OSCC cell line SCCVII. We examined the inhibitory effects of IMD-0560 on NF-κB activity and tumor invasion using human OSCC cell lines and SCCVII cells in vitro. Using a mouse model of jaw bone invasion by SCCVII cells, we assessed the inhibitory effect of IMD-0560 on jaw bone invasion, tumor growth, and matrix degradation in vivo. IMD-0560 suppressed the nuclear translocation of NF-κB and the degradation of IκBα in OSCC cells. IMD-0560 also inhibited invasion by suppressing matrix metalloproteinase-9 (MMP-9) production in OSCC cells. IMD-0560 protected against zygoma and mandible destruction by SCCVII cells, reduced the number of osteoclasts by inhibiting receptor activator of NF-κB ligand (RANKL) expression in osteoblastic cells and SCCVII cells, increased SCCVII cell death and suppressed cell proliferation and MMP-9 production in SCCVII cells. Based on these results, IMD-0560 may represent a new therapeutic agent for bone invasion by OSCC cells.

Dissecting the role of bone marrow stromal cells on bone metastases

Tumor-induced bone disease is a dynamic process that involves interactions with many cell types. Once metastatic cancer cells reach the bone, they are in contact with many different cell types that are present in the cell-rich bone marrow. These cells include the immune cells, myeloid cells, fibroblasts, osteoblasts, osteoclasts, and mesenchymal stem cells. Each of these cell populations can influence the behavior or gene expression of both the tumor cells and the bone microenvironment. Additionally, the tumor itself can alter the behavior of these bone marrow cells which further alters both the microenvironment and the tumor cells. While many groups focus on studying these interactions, much remains unknown. A better understanding of the interactions between the tumor cells and the bone microenvironment will improve our knowledge on how tumors establish in bone and may lead to improvements in diagnosing and treating bone metastases. This review details our current knowledge on the interactions between tumor cells that reside in bone and their microenvironment.

Tumor signatures of PTHLH overexpression, high serum calcium, and poor prognosis were observed exclusively in clear cell but not non clear cell renal carcinomas

High serum calcium (Ca) due to aberrant secretion of tumor parathyroid hormone-like hormone (PTHLH) is a well-known paraneoplastic sign and is associated with poor prognosis in patients with renal cell carcinoma (RCC). However, the status of serum Ca and tumor PTHLH expression have not been verified using the 2004 World Health Organization (WHO) renal tumor classification. We retrospectively reviewed corrected serum Ca levels at initial onset (n = 683) and/or as of recurrence (n = 71) in patients with RCC. We also examined a total of 623 renal parenchymal tumor samples for PTHLH mRNA expressions by quantitative real-time PCR. High serum Ca concomitant with PTHLH overexpression in tumors was observed exclusively in clear cell RCC but not in other non clear cell subtype tumors, including papillary, chromophobe, collecting-duct, unclassified, and other rare subtype RCCs or in benign oncocytomas and angiomyolipomas. In clear cell RCC, PTHLH expression was significantly high in male patients, and was associated with a symptomatic presentation, higher grade, and higher stage cases, whereas it was not associated with VHL gene status. Univariate analyses demonstrated that high PTHLH expression was strongly associated with poor outcome both in overall survival (OS) and disease-free survival (DFS) for patients who underwent standard nephrectomy. Further multivariate Cox analyses revealed that the PTHLH expressions remained as independent prognostic parameters for OS but not for DFS. These data suggest that the previously characterized tumor signatures of high serum Ca due to high PTHLH expression and poor prognosis are clear cell RCC-specific features, whereas these characteristics are rare in non clear cell RCCs.

Chaperonin CCT-mediated AIB1 folding promotes the growth of ERα-positive breast cancer cells on hard substrates

Clinical observations have revealed a strong association between estrogen receptor alpha (ERα)-positive tumors and the development of bone metastases, however, the mechanism underlying this association remains unknown. We cultured MCF-7 (ERα-positive) on different rigidity substrates. Compared with cells grown on more rigid substrates (100 kPa), cells grown on soft substrates (10 kPa) exhibited reduced spreading ability, a lower ratio of cells in the S and G2/M cell cycle phases, and a decreased proliferation rate. Using stable isotope labeling by amino acids (SILAC), we further compared the whole proteome of MCF-7 cells grown on substrates of different rigidity (10 and 100 kPa), and found that the expression of eight members of chaperonin CCT increased by at least 2-fold in the harder substrate. CCT folding activity was increased in the hard substrate compared with the soft substrates. Amplified in breast cancer 1 (AIB1), was identified in CCT immunoprecipitates. CCT folding ability of AIB1 increased on 100-kPa substrate compared with 10- and 30-kPa substrates. Moreover, using mammalian two-hybrid protein-protein interaction assays, we found that the polyglutamine repeat sequence of the AIB1 protein was essential for interaction between CCTζ and AIB1. CCTζ-mediated AIB1 folding affects the cell area spreading, growth rate, and cell cycle. The expressions of the c-myc, cyclin D1, and PgR genes were higher on hard substrates than on soft substrate in both MCF-7 and T47D cells. ERα and AIB1 could up-regulate the mRNA and protein expression levels of the c-myc, cyclin D1, and PgR genes, and that 17 β-estradiol could enhance this effects. Conversely, 4-hydroxytamoxifen, could inhibit these effects. Taken together, our studies demonstrate that some ERα-positive breast cancer cells preferentially grow on more rigid substrates. CCT-mediated AIB1 folding appears to be involved in the rigidity response of breast cancer cells, which provides novel insight into the mechanisms of bone metastasis.

Bone-targeted therapy for metastatic breast cancer-Where do we go from here? A commentary from the BONUS 8 meeting

The annual Bone and The Oncologist New Updates (BONUS 8) conference focuses on the current understanding and dilemmas in the treatment and prevention of bone metastasis in cancer, as well as novel research on bone homeostasis and cancer-induced bone loss. We present commentaries from experts for their own take on where they feel the field of bone-targeted therapies for metastatic breast cancer is moving, or needs to move, if we are to make further progress.

Cancer-associated bone disease

Bone is commonly affected in cancer. Cancer-induced bone disease results from the primary disease, or from therapies against the primary condition, causing bone fragility. Bone-modifying agents, such as bisphosphonates and denosumab, are efficacious in preventing and delaying cancer-related bone disease. With evidence-based care pathways, guidelines assist physicians in clinical decision-making. Of the 57 million deaths in 2008 worldwide, almost two thirds were due to non-communicable diseases, led by cardiovascular diseases and cancers. Bone is a commonly affected organ in cancer, and although the incidence of metastatic bone disease is not well defined, it is estimated that around half of patients who die from cancer in the USA each year have bone involvement. Furthermore, cancer-induced bone disease can result from the primary disease itself, either due to circulating bone resorbing substances or metastatic bone disease, such as commonly occurs with breast, lung and prostate cancer, or from therapies administered to treat the primary condition thus causing bone loss and fractures. Treatment-induced osteoporosis may occur in the setting of glucocorticoid therapy or oestrogen deprivation therapy, chemotherapy-induced ovarian failure and androgen deprivation therapy. Tumour skeletal-related events include pathologic fractures, spinal cord compression, surgery and radiotherapy to bone and may or may not include hypercalcaemia of malignancy while skeletal complication refers to pain and other symptoms. Some evidence demonstrates the efficacy of various interventions including bone-modifying agents, such as bisphosphonates and denosumab, in preventing or delaying cancer-related bone disease. The latter includes treatment of patients with metastatic skeletal lesions in general, adjuvant treatment of breast and prostate cancer in particular, and the prevention of cancer-associated bone disease. This has led to the development of guidelines by several societies and working groups to assist physicians in clinical decision making, providing them with evidence-based care pathways to prevent skeletal-related events and bone loss. The goal of this paper is to put forth an IOF position paper addressing bone diseases and cancer and summarizing the position papers of other organizations.

Bisphosphonates in the adjuvant treatment of young women with breast cancer: the estrogen rich is a poor candidate!

During the last 2 decades the role of bisphosphonates (BPs) to reduce skeletal-related events from bone metastases in breast cancer has been well defined. Several preclinical studies have strongly suggested that BPs may also provide an anti-cancer effect in early breast cancer. Indeed, the use of adjuvant BPs represents a unique approach that attempts at eradicating occult tumor micro-metastases residing in the bone marrow via targeting the bone microenvironment to render it less favorable for cancer cell growth. Although, this concept has been tested clinically for more than 15 years, no final consensus has been reached as for the routine use of BPs in the adjuvant phase of breast cancer, owing to conflicting results of randomized studies. Nevertheless, accumulating evidence from recent trials has indicated a therapeutic benefit of adjuvant BPs-particularly zoledronic acid-in women with established menopause, with no or perhaps detrimental effects in premenopausal women. Indeed, this hypothesis has opened a new chapter on the role of estrogen-poor microenvironment as a potential pre-requisite for the anti-tumor effects of BPs in the adjuvant phase of breast cancer. In this review, we will emphasize the biological rational of using BPs to target bone microenvironment in patients with early breast cancer and we will explore mechanistic differences; related to bisphosphonates effects in premenopausal versus postmenopausal women and how the endocrine environment would influence the anticancer potential of these compounds.