Future Treatment of Bone Metastases

Reclassified the phenotypes of cancer types and construct a nomogram for predicting bone metastasis risk: A pan-cancer analysis

BACKGROUND

Numerous of models have been developed to predict the bone metastasis (BM) risk; however, due to the variety of cancer types, it is difficult for clinicians to use these models efficiently. We aimed to perform the pan-cancer analysis to create the cancer classification system for BM, and construct the nomogram for predicting the BM risk.

METHODS

Cancer patients diagnosed between 2010 and 2018 in the Surveillance, Epidemiology, and End Results (SEER) database were included. Unsupervised hierarchical clustering analysis was performed to create the BM prevalence-based cancer classification system (BM-CCS). Multivariable logistic regression was applied to investigate the possible associated factors for BM and construct a nomogram for BM risk prediction. The patients diagnosed between 2017 and 2018 were selected for validating the performance of the BM-CCS and the nomogram, respectively.

RESULTS

A total of 50 cancer types with 2,438,680 patients were included in the construction model. Unsupervised hierarchical clustering analysis classified the 50 cancer types into three main phenotypes, namely, categories A, B, and C. The pooled BM prevalence in category A (17.7%; 95% CI: 17.5%-17.8%) was significantly higher than that in category B (5.0%; 95% CI: 4.5%-5.6%), and category C (1.2%; 95% CI: 1.1%-1.4%) (p < 0.001). Advanced age, male gender, race, poorly differentiated grade, higher T, N stage, and brain, lung, liver metastasis were significantly associated with BM risk, but the results were not consistent across all cancers. Based on these factors and BM-CCS, we constructed a nomogram for predicting the BM risk. The nomogram showed good calibration and discrimination ability (AUC in validation cohort = 88%,95% CI: 87.4%-88.5%; AUC in construction cohort = 86.9%,95% CI: 86.8%-87.1%). The decision curve analysis also demonstrated the clinical usefulness.

CONCLUSION

The classification system and prediction nomogram may guide the cancer management and individualized BM screening, thus allocating the medical resources to cancer patients. Moreover, it may also have important implications for studying the etiology of BM.

Pharmacologic management of metastatic bone disease

Bone is a common site of metastases, particularly in advanced breast and prostate cancer. Skeletal related events associated with bone metastases include pathologic fracture, need for surgery/radiation to bone and cord compression. These events cause significant morbidity and mortality. Bisphosphonates as well as denosumab act on the bone microenvironment and reduce the rate of skeletal related events by approximately 25%-40%. Hence, these therapies are an important adjunctive therapy in cancer care. Despite the established efficacy and recommendations for their use in many international guidelines, these bone modifying agents are underutilized. This review examines the currently available guidelines on bone modifying agents in metastatic bone disease and summarizes their efficacy, risk and comparative benefits.

A predictive biomarker panel for bone metastases: Liquid biopsy approach

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Data mining of published microarray datasets directed us to the identification of a multi gene panel involving of 15 genes that are particular to bone metastases.

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Serum exosomal markers HSP90AA1, SPP1, IL3, and PTK2 found in the present study might be useful in detecting the early spread of bone metastases leading to better clinical outcomes.

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This multi-gene panel and their related pathways may assist as promising conclusion predictors using novel approaches of exosome as liquid biopsy and their application in therapeutic targets in breast and lung cancer patients with bone metastases.

Bone metastases is one of the common metastatic site and leading cause of cancer-related mortality in progressive cancer patients. The purpose of the present study is to establish a liquid biopsy based multi-gene classifier and associated signalling pathways for early diagnosis of bone metastases. We used publically available microarray datasets and analysed them in a platform/chip-specific manner using GeneSpring software. Analyses of gene expression datasets identified 15 consistently over-expressed genes with statistical significance. Further, expression profile of same set of 15 genes were compared in breast and lung cancer exosome derived mRNA with (n = 10) and without (n = 10) bone metastases against healthy controls. ROC curve analysis performed individually for all the 15 genes shortlisted the 5 most relevant genes with significant sensitivity and specificity in both cancers. This liquid biopsy-based bone metastases predictor using multi-gene panel is a unique approach with potential clinical applications for effective management of aggressive cancers.

Small extracellular vesicles deliver osteolytic effectors and mediate cancer-induced osteolysis in bone metastatic niche

Extracellular vesicles (EVs) play critical roles in regulating bone metastatic microenvironment through mediating intercellular crosstalks. However, little is known about the contribution of EVs derived from cancer cells to the vicious cycle of bone metastasis. Here, we report a direct regulatory mode between tumour cells and osteoclasts in metastatic niche of prostate cancer via vesicular miRNAs transfer. Combined analysis of miRNAs profiles both in tumour‐derived small EVs (sEVs) and osteoclasts identified miR‐152‐3p as a potential osteolytic molecule. sEVs were enriched in miR‐152‐3p, which targets osteoclastogenic regulator MAFB. Blocking miR‐152‐3p in sEVs upregulated the expression of MAFB and impaired osteoclastogenesis in vitro. In vivo experiments of xenograft mouse model found that blocking of miR‐152‐3p in sEVs significantly slowed down the loss of trabecular architecture, while systemic inhibition of miR‐152‐3p using antagomir‐152‐3p reduced the osteolytic lesions of cortical bone while preserving basic trabecular architecture. Our findings suggest that miR‐152‐3p carried by prostate cancer‐derived sEVs deliver osteolytic signals from tumour cells to osteoclasts, facilitating osteolytic progression in bone metastasis.

Extracellular Vesicles in Tumors: A Potential Mediator of Bone Metastasis

As one of the most common metastatic sites, bone has a unique microenvironment for the growth and prosperity of metastatic tumor cells. Bone metastasis is a common complication for tumor patients and accounts for 15-20% of systemic metastasis, which is only secondary to lung and liver metastasis. Cancers prone to bone metastasis include lung, breast, and prostate cancer. Extracellular vesicles (EVs) are lipid membrane vesicles released from different cell types. It is clear that EVs are associated with multiple biological phenomena and are crucial for intracellular communication by transporting intracellular substances. Recent studies have implicated EVs in the development of cancer. However, the potential roles of EVs in the pathological exchange of bone cells between tumors and the bone microenvironment remain an emerging area. This review is focused on the role of tumor-derived EVs in bone metastasis and possible regulatory mechanisms.

Management of bone health in solid tumours: From bisphosphonates to a monoclonal antibody

Patients with solid tumours are at risk of impaired bone health from metastases and cancer therapy-induced bone loss (CTIBL). We review medical management of bone health in patients with solid tumours over the past 30 years, from first-generation bisphosphonates to the receptor activator of nuclear factor κB ligand (RANKL)-targeted monoclonal antibody, denosumab. In the 1980s, first-generation bisphosphonates were shown to reduce the incidence of skeletal-related events (SREs) in patients with breast cancer. Subsequently, more potent second- and third-generation bisphosphonates were developed, particularly zoledronic acid (ZA). Head-to-head studies showed that ZA was significantly more effective than pamidronate for reducing SREs in patients with breast and castrate-resistant prostate cancer (CRPC), becoming the standard of care for more than a decade. The RANKL inhibitor denosumab was licensed in 2010, and head-to-head studies and integrated analyses confirmed its superiority to ZA for preventing SREs, particularly in breast cancer and CRPC. Bisphosphonates and denosumab have also been investigated for prevention of CTIBL in patients receiving hormonal therapy for breast and prostate cancer, and denosumab is licensed in this indication. Despite advances in management of bone health, several issues remain, notably the optimal time to initiate therapy, duration of therapy, and dosing frequency, and how to avoid toxicity, particularly with long-term treatment. In summary, introduction of ZA and denosumab has protected patients with bone metastasis from serious bone complications and improved their quality of life. Ongoing research will hopefully guide the optimal use of these agents to help maintain bone health in patients with solid tumours.

The Contribution of the Immune System in Bone Metastasis Pathogenesis

Bone metastasis is associated with significant morbidity for cancer patients and results in a reduced quality of life. The bone marrow is a fertile soil containing a complex composition of immune cells that may actually provide an immune-privileged niche for disseminated tumor cells to colonize and proliferate. In this unique immune milieu, multiple immune cells including T cells, natural killer cells, macrophages, dendritic cells, myeloid-derived suppressor cells, and neutrophils are involved in the process of bone metastasis. In this review, we will discuss the crosstalk between immune cells in bone microenvironment and their involvement with cancer cell metastasis to the bone. Furthermore, we will highlight the anti-tumoral and pro-tumoral function of each immune cell type that contributes to bone metastasis. We will end with a discussion of current therapeutic strategies aimed at sensitizing immune cells.

Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer

BACKGROUND

High affinity androgen binding to the androgen receptor (AR) activates genes required for male sex differentiation and promotes the development and progression of prostate cancer. Human AR transcriptional activity involves interactions with coregulatory proteins that include primate-specific melanoma antigen-A11 (MAGE-A11), a coactivator that increases AR transcriptional activity during prostate cancer progression to castration-resistant/recurrent prostate cancer (CRPC).

METHODS

Microarray analysis and quantitative RT-PCR were performed to identify androgen-regulated MAGE-A11-dependent genes in LAPC-4 prostate cancer cells after lentivirus shRNA knockdown of MAGE-A11. Chromatin immunoprecipitation was used to assess androgen-dependent AR recruitment, and immunocytochemistry to localize an androgen-dependent protein in prostate cancer cells and tissue and in the CWR22 human prostate cancer xenograft.

RESULTS

Microarray analysis of androgen-treated LAPC-4 prostate cancer cells indicated follistatin-like 1 (FSTL1) is up-regulated by MAGE-A11. Androgen-dependent up-regulation of FSTL1 was inhibited in LAPC-4 cells by lentivirus shRNA knockdown of AR or MAGE-A11. Chromatin immunoprecipitation demonstrated AR recruitment to intron 10 of the FSTL1 gene that contains a classical consensus androgen response element. Increased levels of FSTL1 protein in LAPC-4 cells correlated with higher levels of MAGE-A11 relative to other prostate cancer cells. FSTL1 mRNA levels increased in CRPC and castration-recurrent CWR22 xenografts in association with predominantly nuclear FSTL1. Increased nuclear localization of FSTL1 in prostate cancer was suggested by predominantly cytoplasmic FSTL1 in benign prostate epithelial cells and predominantly nuclear FSTL1 in epithelial cells in CRPC tissue and the castration-recurrent CWR22 xenograft. AR expression studies showed nuclear colocalization of AR and endogenous FSTL1 in response to androgen.

CONCLUSION

AR and MAGE-A11 cooperate in the up-regulation of FSTL1 to promote growth and progression of CRPC. Prostate 77:505-516, 2017. © 2016 Wiley Periodicals, Inc.

Emerging therapeutic targets in cancer induced bone disease: A focus on the peripheral type 2 cannabinoid receptor

Skeletal complications are a common cause of morbidity in patients with primary bone cancer and bone metastases. The type 2 cannabinoid (Cnr2) receptor is implicated in cancer, bone metabolism and pain perception. Emerging data have uncovered the role of Cnr2 in the regulation of tumour-bone cell interactions and suggest that agents that target Cnr2 in the skeleton have potential efficacy in the reduction of skeletal complications associated with cancer. This review aims to provide an overview of findings relating to the role of Cnr2 receptor in the regulation of skeletal tumour growth, osteolysis and bone pain, and highlights the many unanswered questions and unmet needs. This review argues that development and testing of peripherally-acting, tumour-, Cnr2-selective ligands in preclinical models of metastatic cancer will pave the way for future research that will advance our knowledge about the basic mechanism(s) by which the endocannabinoid system regulate cancer metastasis, stimulate the development of a safer cannabis-based therapy for the treatment of cancer and provide policy makers with powerful tools to assess the science and therapeutic potential of cannabinoid-based therapy. Thus, offering the prospect of identifying selective Cnr2 ligands, as novel, alternative to cannabis herbal extracts for the treatment of advanced cancer patients.

A multi-targeted approach to treating bone metastases

The treatment of bone-metastatic cancer now takes advantage of the unique biology of this clinical state. The complex interplay between the cancer cells and the bone microenvironment leads to a host of therapeutic targets, with agents in various stages of clinical use or study. Targets include interactions between the cancer cells and osteoclasts, osteoblasts, endothelial cells, stromal cells, hematopoietic progenitor cells, cells of the immune system, and the bone matrix. Efforts at understanding specific mechanisms of drug resistance in the bone are also ongoing. Successful clinical outcomes will be the result of co-targeting and interrupting the various tumor-supportive elements and cooperating pathways at the level of the tumor cell, the primary and metastatic microenvironments, and systemic cancer effects, leading to a "scaled network disruption" to undermine the disease state.

Diagnosis and management of osteonecrosis of the jaw: a systematic review and international consensus

This work provides a systematic review of the literature from January 2003 to April 2014 pertaining to the incidence, pathophysiology, diagnosis, and treatment of osteonecrosis of the jaw (ONJ), and offers recommendations for its management based on multidisciplinary international consensus. ONJ is associated with oncology-dose parenteral antiresorptive therapy of bisphosphonates (BP) and denosumab (Dmab). The incidence of ONJ is greatest in the oncology patient population (1% to 15%), where high doses of these medications are used at frequent intervals. In the osteoporosis patient population, the incidence of ONJ is estimated at 0.001% to 0.01%, marginally higher than the incidence in the general population (<0.001%). New insights into the pathophysiology of ONJ include antiresorptive effects of BPs and Dmab, effects of BPs on gamma delta T-cells and on monocyte and macrophage function, as well as the role of local bacterial infection, inflammation, and necrosis. Advances in imaging include the use of cone beam computerized tomography assessing cortical and cancellous architecture with lower radiation exposure, magnetic resonance imaging, bone scanning, and positron emission tomography, although plain films often suffice. Other risk factors for ONJ include glucocorticoid use, maxillary or mandibular bone surgery, poor oral hygiene, chronic inflammation, diabetes mellitus, ill-fitting dentures, as well as other drugs, including antiangiogenic agents. Prevention strategies for ONJ include elimination or stabilization of oral disease prior to initiation of antiresorptive agents, as well as maintenance of good oral hygiene. In those patients at high risk for the development of ONJ, including cancer patients receiving high-dose BP or Dmab therapy, consideration should be given to withholding antiresorptive therapy following extensive oral surgery until the surgical site heals with mature mucosal coverage. Management of ONJ is based on the stage of the disease, size of the lesions, and the presence of contributing drug therapy and comorbidity. Conservative therapy includes topical antibiotic oral rinses and systemic antibiotic therapy. Localized surgical debridement is indicated in advanced nonresponsive disease and has been successful. Early data have suggested enhanced osseous wound healing with teriparatide in those without contraindications for its use. Experimental therapy includes bone marrow stem cell intralesional transplantation, low-level laser therapy, local platelet-derived growth factor application, hyperbaric oxygen, and tissue grafting.

The Roles of Epithelial-to-Mesenchymal Transition (EMT) and Mesenchymal-to-Epithelial Transition (MET) in Breast Cancer Bone Metastasis: Potential Targets for Prevention and Treatment

Many studies have revealed molecular connections between breast and bone. Genes, important in the control of bone remodeling, such as receptor activator of nuclear kappa (RANK), receptor activator of nuclear kappa ligand (RANKL), vitamin D, bone sialoprotein (BSP), osteopontin (OPN), and calcitonin, are expressed in breast cancer and lactating breast. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) effectors play critical roles during embryonic development, postnatal growth, and epithelial homeostasis, but also are involved in a number of pathological conditions, including wound repair, fibrosis, inflammation, as well as cancer progression and bone metastasis. Transforming growth factor β (TGFβ), insulin-like growth factor I & II (IGF I & II), platelet-derived growth factor (PDGF), parathyroid hormone-related protein (PTH(rP)), vascular endothelial growth factor (VEGF), epithelial growth factors II/I (ErbB/EGF), interleukin 6 (IL-6), IL-8, IL-11, IL-1, integrin αvβ3, matrix metalloproteinases (MMPs), catepsin K, hypoxia, notch, Wnt, bone morphogenetic proteins (BMP), and hedgehog signaling pathways are important EMT and MET effectors identified in the bone microenviroment facilitating bone metastasis formation. Recently, Runx2, an essential transcription factor in the regulation of mesenchymal cell differentiation into the osteoblast lineage and proper bone development, is also well-recognized for its expression in breast cancer cells promoting osteolytic bone metastasis. Understanding the precise mechanisms of EMT and MET in the pathogenesis of breast cancer bone metastasis can inform the direction of therapeutic intervention and possibly prevention.

Targeting FSTL1 prevents tumor bone metastasis and consequent immune dysfunction

Bone metastasis greatly deteriorates the quality of life in patients with cancer. Although mechanisms have been widely investigated, the relationship between cancer bone metastasis and antitumor immunity in the host has been much less studied. Here, we report a novel mechanism of bone metastasis mediated by FSTL1, a follistatin-like glycoprotein secreted by Snail(+) tumor cells, which metastasize frequently to bone. We found that FSTL1 plays a dual role in bone metastasis-in one way by mediating tumor cell invasion and bone tropism but also in a second way by expanding a population of pluripotent mesenchymal stem-like CD45(-)ALCAM(+) cells derived from bone marrow. CD45(-)ALCAM(+) cells induced bone metastasis de novo, but they also generated CD8(low) T cells with weak CTL activity in the periphery, which also promoted bone metastasis in an indirect manner. RNA interference-mediated attenuation of FSTL1 in tumor cells prevented bone metastasis along with the parallel increase in ALCAM(+) cells and CD8(low) T cells. These effects were accompanied by heightened antitumor immune responses in vitro and in vivo. In clinical specimens of advanced breast cancer, ALCAM(+) cells increased with FSTL1 positivity in tumor tissues, but not in adjacent normal tissues, consistent with a causal connection between these molecules. Our findings define FSTL1 as an attractive candidate therapeutic target to prevent or treat bone metastasis, which remains a major challenge in patients with cancer.

Bone-Targeted Agents for the Management of Breast Cancer Patients with Bone Metastases

Despite advances in adjuvant therapy for breast cancer, bone remains the most common site of recurrence. The goal of therapy for these patients is palliative and focused on maximizing the duration and quality of their life, while concurrently minimizing any disease or treatment-related complications. Bone metastases predispose patients to reduced survival, pain, impaired quality of life and the development of skeletal-related events. With an increased understanding of the pathophysiology of bone metastasis, effective treatments for their management have evolved and are now in widespread clinical use. This article will discuss the pathogenesis of bone metastases and review the key clinical evidence for the efficacy and safety of currently available systemic bone-targeted therapies in breast cancer patients with an emphasis on bisphosphonates and the receptor activator of nuclear factor kappa B ligand (RANKL) inhibitors. We will also discuss novel strategies and therapies currently in development.

Systemic Therapy for Bone Metastases

Background

Accelerated bone loss in patients with cancer is a frequent problem that may result from invasion of the cancer to bone, paraneoplastic tumor proteins, and/or hormonal therapies utilized for cancer treatment. Patients with osteolytic bone disease from multiple myeloma and bone metastases from solid tumors may develop a vicious cycle of bone destruction involving both osteolytic and osteoblastic effects. Consequently, a variety of skeletal-related events (SREs) may occur, including pathological fractures, hypercalcemia, spinal cord compression, and the need for surgical intervention and radiation therapy.

Methods

This article reviews the results of trials that investigated the safety and efficacy of pharmacologic agents, including bisphosphonates and denosumab, for treatment of bone metastases. This analysis is derived from an assessment of the medical literature.

Results

Beneficial systemic therapies for bone metastases have been developed to decrease SREs. Possible antitumor effects of the bisphosphonates are explored. In addition, the utility of markers of bone turnover in relation to response to therapy and survival, the safety and toxicity of bone-targeted therapies, treatment guidelines, and economic considerations are also discussed.

Conclusions

Effective systemic therapies for metastatic bone disease are available. Ongoing and future research projects in this field are also presented.

New developments for treatment and prevention of bone metastases

PURPOSE OF REVIEW

To provide a critical review of recent trials of bone resorption inhibitory drugs (bisphosphonates and denosumab) for the treatment and the prevention of bone metastases in solid tumors.

RECENT FINDINGS

The bisphosphonate zoledronic acid is now part of the standard treatment for metastatic bone disease. Comparative trials in this setting between zoledronic acid and denosumab have shown superior (in breast and in prostate cancer) or noninferior (in other solid tumors) skeletal-related event-prevention activity for denosumab. Osteonecrosis of the jaw is the most important side-effect of both compounds. Recent data also indicate the potential of zoledronic acid to reduce the recurrence rate in breast cancer.

SUMMARY

Much progress has been accomplished for the treatment of tumor bone disease with bone resorption inhibitory drugs. Advances are now awaited in the setting of prevention of bone metastases.

A primer of bone metastases management in breast cancer patients

Bone is the most common site for distant spread of breast cancer. Following a diagnosis of metastatic bone disease, patients can suffer from significant morbidity because of pain and skeletal related events (SRES). Bisphosphonates are potent inhibitors of osteoclastic function and the mainstay of bone-directed therapy for bone metastases. The aims of bisphosphonates are to prevent and delay SRES, to reduce bone pain, and to improve quality of life. Bisphosphonate therapy appears to have revolutionized treatment of bone metastases, but bisphosphonate use has several limitations. Those limitations include the high cost of the agents and the need for return trips to the clinic for intravenous treatment. Moreover, many uncertainties surround bisphosphonate use-for example, the timing of bisphosphonate initiation, the choice of bisphosphonate to use, the optimal duration of treatment, and the appropriate means to identify patients who will and will not benefit. In addition, potentially serious adverse effects have been associated with bisphosphonate use-for example, renal toxicity, gastrointestinal side effects, and osteonecrosis of the jaw. The present review is intended as a primer for oncology specialists who treat patients with bone metastases secondary to breast cancer. It focuses on bisphosphonate treatment guidelines, the evidence for those guidelines, and a discussion of new therapeutic agents. It also discusses the use of biochemical markers of bone metabolism, which show promise for predicting the risk of a patient's developing a SRE and of benefiting from bisphosphonate treatment.

TAK1-TAB2 signaling contributes to bone destruction by breast carcinoma cells

Advanced-stage breast cancers frequently metastasize to the bones and cause bone destruction, but the underlying mechanism is not fully understood. This study presents evidence that TGF-β-activated protein kinase 1 (TAK1) signaling in tumor cells promotes bone destruction by metastatic breast carcinoma cells, controlling expression of prometastatic factors including matrix metalloproteinase (MMP) 9 and COX2. Suppression of TAK1 signaling by dominant-negative TAK1 (dn-TAK1) in breast carcinoma MDA-MB-231 cells impairs bone colonization by carcinoma cells and bone osteolysis in the intracardiac injection model. Mechanistic studies showed that inhibition of TAK1 by dn-TAK1 or siRNA blocked expression of factors implicated in bone metastasis, such as MMP-9, COX2/PTGS2, parathyroid hormone-related protein (PTHrP) and interleukin 8 (IL-8), but did not affect activation of p38MAPK by TGF-β. TAK1 signaling is mediated by TAK1-binding partners TAB1, TAB2, and TAB3. Carcinoma cells express elevated mRNA levels of TAB2 and TAB3, whereas the TAB1 expression is noticeably low. Accordingly, depletion of TAB2 by siRNA reduced expression of MMP-9 and COX2. Together, these studies show that the TAK1-TAB2-TAB3 signaling axis is critical for carcinoma-induced bone lesions, mediating expression of proinvasive and osteolytic factors. These findings identify the TAK1-TAB2 axis as a potential therapeutic target in bone metastasis.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

Osteoclast activity and subtypes as a function of physiology and pathology--implications for future treatments of osteoporosis

Osteoclasts have traditionally been associated exclusively with catabolic functions that are a prerequisite for bone resorption. However, emerging data suggest that osteoclasts also carry out functions that are important for optimal bone formation and bone quality. Moreover, recent findings indicate that osteoclasts have different subtypes depending on their location, genotype, and possibly in response to drug intervention. The aim of the current review is to describe the subtypes of osteoclasts in four different settings: 1) physiological, in relation to turnover of different bone types; 2) pathological, as exemplified by monogenomic disorders; 3) pathological, as identified by different disorders; and 4) in drug-induced situations. The profiles of these subtypes strongly suggest that these osteoclasts belong to a heterogeneous cell population, namely, a diverse macrophage-associated cell type with bone catabolic and anabolic functions that are dependent on both local and systemic parameters. Further insight into these osteoclast subtypes may be important for understanding cell-cell communication in the bone microenvironment, treatment effects, and ultimately bone quality.

Breast cancer at bone metastatic sites: recent discoveries and treatment targets

Breast carcinoma is the most common cancer of women. Bones are often involved with breast carcinoma metastases with the resulting morbidity and reduced quality of life. Breast cancer cells arriving at bone tissues mount supportive microenvironment by recruiting and modulating the activity of several host tissue cell types including the specialized bone cells osteoblasts and osteoclasts. Pathologically activated osteoclasts produce osteolytic lesions associated with bone pain, pathological fractures, cord compression and other complications of metastatic breast carcinoma at bone. Over the last decade there has been enormous growth of knowledge in the field of osteoclasts biology both in the physiological state and in the tumor microenvironment. This knowledge allowed the development and implementation of several targeted therapeutics that expanded the armamentarium of the oncologists dealing with the metastases-associated osteolytic disease. While the interactions of cancer cells with resident bone cells at the established metastatic gross lesions are well-studied, the preclinical events that underlie the progression of disseminated tumor cells into micrometastases and then into clinically-overt macrometastases are just starting to be uncovered. In this review, we discuss the established information and the most recent discoveries in the pathogenesis of osteolytic metastases of breast cancer, as well as the corresponding investigational drugs that have been introduced into clinical development.

Bone cancer pain

In the United States, cancer is the second most common cause of death and it is expected that about 562,340 Americans will have died of cancer in 2009. Bone cancer pain is common in patients with advanced breast, prostate, and lung cancer as these tumors have a remarkable affinity to metastasize to bone. Once tumors metastasize to bone, they are a major cause of morbidity and mortality as the tumor induces significant skeletal remodeling, fractures, pain, and anemia. Currently, the factors that drive cancer pain are poorly understood. However, several recently introduced models of bone cancer pain, which closely mirror the human condition, are providing insight into the mechanisms that drive bone cancer pain and guide the development of mechanism-based therapies to treat the cancer pain. Several of these mechanism-based therapies have now entered human clinical trials. If successful, these therapies have the potential to significantly enlarge the repertoire of modalities that can be used to treat bone cancer pain and improve the quality of life, functional status, and survival of patients with bone cancer.

Managing cancer treatment-induced bone loss and osteoporosis in patients with breast or prostate cancer

PURPOSE

To discuss trends in breast and prostate cancer prevalence and survival; risk factors for bone loss, osteoporosis, and fractures and the approach to risk assessment in patients with these malignancies; established and investigational drug therapies for managing cancer treatment-induced bone loss and osteoporosis; and the role of health-system pharmacists in promoting bone health in patients with breast or prostate cancer.

SUMMARY

Breast cancer and prostate cancer are common, deadly diseases, but many survivors are alive today because of improvements in early detection and treatment over the past 10-15 years. Cancer chemotherapy, corticosteroids, hormone-ablation therapy, and other common risk factors place patients with breast or prostate cancer at high risk for bone loss, osteoporosis, and fractures. Most patients with breast or prostate cancer should undergo assessment of risk for bone loss and osteoporosis that involves a bone-related history and physical examination, dual-energy X-ray absorptiometry scanning, and the FRAX fracture risk assessment tool from the World Health Organization. A recent National Comprehensive Cancer Network task force report on bone health in cancer care provides recommendations for considering the use of pharmacologic therapy on the basis of the results of this assessment. Bisphosphonates are useful for slowing or preventing bone loss associated with hormone-ablation therapy in women with breast cancer and men with prostate cancer, although fracture data are limited in women and not available in men. The usefulness of other therapies (selective estrogen receptor modulators, teriparatide, calcitonin salmon, and estrogens) is limited by adverse effects, a lack of experience with the drugs in these patient populations, or both. Various drug therapies are in development for managing cancer treatment-induced bone loss and osteoporosis. The agent closest to approval by the Food and Drug Administration, denosumab, has been shown to improve bone mineral density in women and men receiving hormone-ablation therapy for breast or prostate cancer, but additional data are needed to dispel safety concerns that could limit the use of this drug in these patient populations. Health-system pharmacists play an important role in screening patients with a history of breast or prostate cancer for bone loss or osteoporosis, making drug therapy recommendations to address the problem, and counseling patients on modifiable risk factors for osteoporosis and proper use of drug therapies to improve bone health.

CONCLUSION

Health-system pharmacists can improve the detection and management of cancer treatment-induced bone loss and osteoporosis in patients receiving systemic therapy for breast or prostate cancer.

[Molecular basis of bone metastasis formation and its targeted therapy]

Formation of bone metastasis is a hallmark of the progression of several solid cancers, providing example for the organ specificity of the process. Bone metastasis may result in both venous and arterial dissemination. Though the molecular basis of the lytic and plastic bone metastasis formation is different, in reality these organ metastases represent a mixture of the two processes. The basis of bone metastasis formation is the activation of osteoclasts and the resulting bone resorption, initiating a vicious circle by activating the initiator cancer cell. The discovery of osteoclast-bone matrix interaction inhibitor bisphosphonates revolutionized the therapy of bone metastasis. Clarifying the molecular pathways involved in bone metastasis formation identified osteoclast differentiation as another feasible target. This process is under control of the TNF receptor family member RANK and its ligand RANKL. The feasibility of using this system to control bone resorption or cancer-induced skeletal events was proven clinically in trials using an anti-RANKL antibody. The clinical success of anti-RANKL antibody therapy provide further evidence that only precise identification of molecular pathways operational in cancers can lead to discovery of more effective (targeted) therapies.

Identification of EpCAM as a molecular target of prostate cancer stroma

To delineate the molecular changes that occur in the tumor microenvironment, we previously performed global transcript analysis of human prostate cancer specimens using tissue microdissection and expression microarrays. Epithelial and stromal compartments were individually studied in both tumor and normal fields. Tumor-associated stroma showed a distinctly different expression pattern compared with normal stroma, having 44 differentially expressed transcripts, the majority of which were up-regulated. In the present study, one of the up-regulated transcripts, epithelial cell adhesion activating molecule, was further evaluated at the protein level in 20 prostate cancer cases using immunohistochemistry and a histomathematical analysis strategy. The epithelial cell adhesion activating molecule showed a 76-fold expression increase in the tumor-associated stroma, as compared with matched normal stroma. Moreover, Gleason 4 or 5 tumor stroma was increased 170-fold relative to matched normal stroma, whereas the Gleason 3 tumor area showed only a 36-fold increase, indicating a positive correlation with Gleason tumor grade. Since the stromal compartment may be particularly accessible to vascular-delivered agents, epithelial cell adhesion activating molecule could become a valuable molecular target for imaging or treatment of prostate cancer.

State of the art management in spine oncology: a worldwide perspective on its evolution, current state, and future

STUDY DESIGN

A review of the past and current status of the evolving field of spine oncology.

OBJECTIVE

To provide a framework of reference for developments in the field, particularly the rapidly evolving field of molecular biology, as well as contemporary practice in the management of spine tumors.

METHODS

Literature review of the surgical treatment of spine tumors in the past and present, the emerging radiologic and biologic technologies, as well as the field of targeted therapy in cancer and the economic implications of technological advances.

RESULTS

A vast contemporary literature is currently available that provides a clear rational basis for treatment. Most treatment recommendations are currently based on retrospective data and small Phase II prospective studies. Treatment paradigms continue to evolve without their relative merits being evaluated by randomized controlled trials. The current lack of randomized trials in spine oncology reflect both the rarity of spine tumors and strongly held biases based on retrospective studies and institutional bias.

CONCLUSION

Spine oncology is a rapidly evolving field with contributions in surgery, radiation therapy, and targeted chemotherapy resulting in overall improvement in quality of life and survival in patients with spine tumors. However, the economic consequences of these improvements are substantial and need to be kept in proper perspective.

Validity of the recorded International Classification of Diseases, 10th edition diagnoses codes of bone metastases and skeletal-related events in breast and prostate cancer patients in the Danish National Registry of Patients

Objective:

The clinical history of bone metastases and skeletal-related events (SREs) secondary to cancers is not well understood. In support of studies of the natural history of bone metastases and SREs in Danish prostate and breast cancer patients, we estimated the sensitivity and specificity of hospital diagnoses for bone metastases and SREs (ie, radiation therapy to the bone, pathological or osteoporotic fractures, spinal cord compression and surgery to the bone) in a nationwide medical registry in Denmark.

Study design and setting:

In North Jutland County, Denmark, we randomly sampled 100 patients with primary prostate cancer and 100 patients with primary breast cancer diagnoses from the National Registry of Patients (NRP), during the period January 1st, 2000 to December 31st, 2000 and followed them for up to five years after their cancer diagnosis. We used information from medical chart reviews as the reference for estimating sensitivity, and specificity of the NRP International Classification of Diseases, 10th edition (ICD-10) coding for bone metastases and SRE diagnoses.

Results:

For prostate cancer, the overall sensitivity of bone metastases or SRE coding in the NRP was 0.54 (95% confidence interval [CI]: 0.39–0.69), and the specificity was 0.96 (95% CI: 0.87–1.00). For breast cancer, the overall sensitivity of bone metastases or SRE coding in the NRP was 0.58 (95% CI: 0.34–0.80), and the specificity was 0.95 (95% CI: 0.88–0.99).

Conclusion:

We measured the validity of ICD-10 coding in the Danish NRP for bone metastases and SREs in prostate and breast cancer patients and found it has adequate sensitivity and high specificity. The NRP remains a valuable tool for clinical epidemiological studies of bone metastases and SREs.

Sagopilone inhibits breast cancer bone metastasis and bone destruction due to simultaneous inhibition of both tumor growth and bone resorption

PURPOSE

Bone metastases have a considerable impact on quality of life in patients with breast and other cancers. Tumors produce osteoclast-activating factors, whereas bone resorption promotes the growth of tumor cells, thus leading to a "vicious cycle" of bone metastasis. Sagopilone, a novel, fully synthetic epothilone, inhibits the growth of breast cancer cells in vitro and in vivo, and here we report its activity in the MDA-MB-231(SA) breast cancer bone metastasis mouse model.

EXPERIMENTAL DESIGN

The potency of sagopilone was determined in treatment models simulating the adjuvant (preventive) and metastatic (therapeutic) settings in the clinic.

RESULTS

We showed that sagopilone inhibited tumor burden and bone destruction, in addition to reducing tumor-induced cachexia and paraplegia. The reduction in osteolytic lesions, tumor growth in bone, and weight loss was statistically significant in the preventive model compared with the vehicle group. In the therapeutic model, sagopilone treatment significantly lowered the number of activated osteoclasts and significantly reduced the osteolytic lesion area, bone volume loss, and bone resorption compared with vehicle treatment while simultaneously inhibiting tumor burden. An in vitro assay confirmed that sagopilone inhibited osteoclast activation without cytotoxic effects, whereas paclitaxel resulted in lower inhibition and high levels of cytotoxicity.

CONCLUSIONS

Sagopilone seems to inhibit the vicious cycle at both the tumor growth and bone resorption stages, suggesting the possibility for substantial benefit in the treatment of patients with breast cancer at risk from bone metastases or with bone lesions already present. Phase II clinical trials with sagopilone in patients with breast cancer are ongoing.

A novel third generation bisphosphonate, minodronate (YM529), prevented proliferation and migration of hepatocellular carcinoma cells through inhibition of mevalonate pathway

AIM

Skeletal metastases and bone metasitasis are a common occurrence in patients with advanced hepatocellular carcinoma (HCC). Bisphosphonates (BPs), which are used for the treatment of osteoporosis and tumor-associated hypercalcemia, have recently been reported to decrease skeletal morbidity in patients with metastatic bone disease. Several studies revealed that nitrogen-containing BPs (N-BPs) could inhibit tumor growth and migration, indicating the possibility that N-BPs have direct inhibitory effects. We aimed to determine the effects of novel a N-BP (YM529) on human HCC cells in vitro.

METHODS

HCC cells were treated with various concentrations of YM529 and the growth inhibition rate was determined. Apoptosis was evaluated by caspase-3/7 assay and caspase-9 cleavage detection. The effects of YM529 on the migration of HCC cells induced by hepatocyte growth factor (HGF) were determined by cell migration assay. To evaluate the involvement of the mevalonate pathway, farnesol (FOH) and geranylgeraniol (GGOH) were added.

RESULTS

YM529 inhibited the proliferation of HCC cells in a dose-dependent manner. The activation of caspase-3/7 and cleavage of caspase-9 demonstrated the involvement of apoptosis in cytotoxicity. GGOH reduced the growth inhibitory effect of YM529 and suppressed the induction of caspase-3/7 activities by YM529 on HCC cells. YM529 inhibited tumor cell migration induced by HGF and this effect was reduced by co-treatment with GGOH.

CONCLUSION

YM529 inhibited the cell proliferation and migration of HCC cells, implicating the involvement of the mevalonate pathway. These results suggest that N-BPs are potential agents for the treatment of HCC skeletal metastases.

RANK/RANKL: regulators of immune responses and bone physiology

Bone-related diseases, such as osteoporosis and rheumatoid arthritis, affect hundreds of millions of people worldwide and pose a tremendous burden to health care. By deepening our understanding of the molecular mechanisms of bone metabolism and bone turnover, it became possible over the past years to devise new and promising strategies for treating such diseases. In particular, three tumor necrosis factor (TNF) family molecules, the receptor activator of NF-kappaB (RANK), its ligand RANKL, and the decoy receptor of RANKL, osteoprotegerin (OPG), have attracted the attention of scientists and pharmaceutical companies alike. Genetic experiments revolving around these molecules established their pivotal role as central regulators of osteoclast development and osteoclast function. RANK-RANKL signaling not only activates a variety of downstream signaling pathways required for osteoclast development, but crosstalk with other signaling pathways also fine-tunes bone homeostasis both in normal physiology and disease. In addition, RANKL and RANK have essential roles in lymph node formation, establishment of the thymic microenvironment, and development of a lactating mammary gland during pregnancy. Consequently, novel drugs specifically targeting RANK, RANKL, and their signaling pathways in osteoclasts are expected to revolutionize the treatment of various ailments associated with bone loss, such as arthritis, periodontal disease, cancer metastases, and osteoporosis.

Docetaxel inhibits bone resorption through suppression of osteoclast formation and function in different manners

Osteoclasts are formed from the monocyte-macrophage lineage in response to receptor activator of nuclear factor kappaB ligand (RANKL) expressed by osteoblasts. Bone is the most common site of breast cancer metastasis, and osteoclasts play roles in the metastasis. The taxane-derived compounds paclitaxel and docetaxel are used for the treatment of malignant diseases, including breast cancer. Here we explored the effects of docetaxel on osteoclastic bone resorption in mouse culture systems. Osteoclasts were formed within 6 days in cocultures of osteoblasts and bone marrow cells treated with 1,25-dihydroxyvitamin D(3) plus prostaglandin E(2). Docetaxel at 10(-8) M inhibited osteoclast formation in the coculture when added for the entire culture period or for the first 3 days. Docetaxel, even at 10(-6) M added for the final 3 days, failed to inhibit osteoclast formation. Osteoprotegerin, a decoy receptor of RANKL, completely inhibited osteoclast formation when added for the final 3 days. Docetaxel at 10(-8) M inhibited the proliferation of osteoblasts and bone marrow cells. RANKL mRNA expression induced by 1,25-dihydroxyvitamin D(3) plus prostaglandin E(2) in osteoblasts was not affected by docetaxel even at 10(-6) M. Docetaxel at 10(-6) M, but not at 10(-8) M, inhibited pit-forming activity of osteoclasts cultured on dentine. Actin ring formation and L: -glutamate secretion by osteoclasts were also inhibited by docetaxel at 10(-6) M. Thus, docetaxel inhibits bone resorption in two different manners: inhibition of osteoclast formation at 10(-8) M and of osteoclast function at 10(-6) M. These results suggest that taxanes have beneficial effects in the treatment of bone metastatic cancers.

Influence of simultaneous targeting of the bone morphogenetic protein pathway and RANK/RANKL axis in osteolytic prostate cancer lesion in bone

Metastasis to bone is the leading cause of morbidity and mortality in advanced prostate cancer patients. Considering the complex reciprocal interactions between the tumor cells and the bone microenvironment, there is increasing interest in developing combination therapies targeting both the tumor growth and the bone microenvironment. In this study, we investigated the effect of simultaneous blockade of BMP pathway and RANK/RANKL axis in an osteolytic prostate cancer lesion in bone. We used a retroviral vector encoding noggin (RetroNoggin) to antagonize the effect of BMPs and RANK:Fc, which is a recombinant RANKL antagonist was used to inhibit RANK/RANKL axis. The tumor growth and bone loss were evaluated using plain radiographs, hind limb tumor measurements, micro PET/CT ((18)FDG and (18)F-fluoride tracer), and histology. Tibias implanted with PC-3 cells developed pure osteolytic lesions at 2-weeks with progressive increase in cortical bone destruction at successive time points. Tibias implanted with PC-3 cells over expressing noggin (RetroNoggin) resulted in reduced tumor size and decreased bone loss compared to the implanted tibias in untreated control animals. RANK:Fc administration inhibited the formation of osteoclasts, delayed the development of osteolytic lesions, decreased bone loss and reduced tumor size in tibias implanted with PC-3 cells. The combination therapy with RANK:Fc and noggin over expression effectively delayed the radiographic development of osteolytic lesions, and decreased the bone loss and tumor burden compared to implanted tibias treated with noggin over expression alone. Furthermore, the animals treated with the combination strategy exhibited decreased bone loss (micro CT) and lower tumor burden (FDG micro PET) compared to animals treated with RANK:Fc alone. Combined blockade of RANK/RANKL axis and BMP pathway resulted in reduced tumor burden and decreased bone loss compared to inhibition of either individual pathway alone in osteolytic prostate cancer lesion in bone. These results suggest that simultaneous targeting of tumor cells and osteoclasts may be the most effective method of inhibiting the progression of established osteolytic metastatic lesions in vivo.

Novel functions of RANK(L) signaling in the immune system

The TNF family members RANKL and its receptor RANK have initially been described as factors expressed on T cells and dendritic cells (DCs), respectively, and have been shown to augment the ability of DCs to stimulate naive T cell proliferation and enhance DC survival. Since another, yet soluble receptor for RANKL, namely OPG, was initially characterized as a factor inhibiting osteoclast development and bone resorption, it was somewhat enigmatic at first why one and the same genes would be essential both for the immune system and bone development - two processes that on first sight do not have much in common. However, in a series of experiments it was conclusively shown that RANKL-expressing T cells can also activate RANK-expressing osteoclasts, and thereby in principal mimicking RANKL-expressing osteoblasts. These findings lead to a paradigm shift and helped to coin the term osteoimmunology in order to account for the crosstalk of immune cells and bone. More importantly was that these findings also provided a rationale for the bone loss observed in patients with a chronically activated immune system such as in rheumatoid arthritis, leukemias, or the like, arguing that T cells, which were activated during the course of the disease to fight it off, also express RANKL, which induces osteoclastogenesis and thereby shifts the intricate balance of bone deposition and resorption in favor of the latter. Through knockout mice it became also clear that the RANKL-RANK-OPG system is involved in other processes such as in controlling autoimmunity or immune responses in the skin. We will briefly summarize the role of RANK(L) signaling in the immune system before we discuss some of the recent data we and others have obtained on the role of RANK(L) in controlling autoimmunity and immune responses in the skin.

Src as a therapeutic target in men with prostate cancer and bone metastases

While responsive to androgen ablation in its early stages, prostate cancer eventually becomes castration-resistant and metastasizes preferentially to bone. Once this happens, the disease carries considerable morbidity and is incurable. The process of bone metastasis involves a complex interplay between tumour and bone tissue. The eventual characteristic clinical presentation of disorganized osteoblastic bone lesions is preceded by a facilitatory osteoblastic phase; an osteoblastic component then continues to underlie the process. Increasing evidence has shown a ubiquitous role for Src (a proto-oncogene tyrosine-protein kinase) in multiple tumour and bone-signalling processes involved in prostate tumour progression, driving proliferation, survival, migration and transition to androgen-independent growth. It is also intimately involved in positively regulating osteoclast physiology. As such, this molecule represents an attractive target for managing progressing prostate cancer. Encouraging results have been obtained in preclinical and clinical studies using Src inhibitors like AZD0530 and dasatinib. Both compounds reduced markers of bone resorption, in patients with cancer and those with advanced castration-resistant prostate cancer, respectively. Moreover, because Src is central to many mechanisms thought to be responsible for the development of castration resistance, adding Src inhibitors to a treatment regimen might reverse this phenomenon. As a result, many Src inhibitors are in preclinical development. This review explores Src inhibition as a strategy for managing bone metastasis in prostate cancer, with a particular focus on targeting the critical osteoclastic response. Other emerging and novel approaches are also considered.

Induction of apoptosis of human primary osteoclasts treated with extracts from the medicinal plant Emblica officinalis

Background

Osteoclasts (OCs) are involved in rheumatoid arthritis and in several pathologies associated with bone loss. Recent results support the concept that some medicinal plants and derived natural products are of great interest for developing therapeutic strategies against bone disorders, including rheumatoid arthritis and osteoporosis. In this study we determined whether extracts of Emblica officinalis fruits display activity of possible interest for the treatment of rheumatoid arthritis and osteoporosis by activating programmed cell death of human primary osteoclasts.

Methods

The effects of extracts from Emblica officinalis on differentiation and survival of human primary OCs cultures obtained from peripheral blood were determined by tartrate-acid resistant acid phosphatase (TRAP)-positivity and colorimetric MTT assay. The effects of Emblica officinalis extracts on induction of OCs apoptosis were studied using TUNEL and immunocytochemical analysis of FAS receptor expression. Finally, in vitro effects of Emblica officinalis extracts on NF-kB transcription factor activity were determined by gel shift experiments.

Results

Extracts of Emblica officinalis were able to induce programmed cell death of mature OCs, without altering, at the concentrations employed in our study, the process of osteoclastogenesis. Emblica officinalis increased the expression levels of Fas, a critical member of the apoptotic pathway. Gel shift experiments demonstrated that Emblica officinalis extracts act by interfering with NF-kB activity, a transcription factor involved in osteoclast biology. The data obtained demonstrate that Emblica officinalis extracts selectively compete with the binding of transcription factor NF-kB to its specific target DNA sequences. This effect might explain the observed effects of Emblica officinalis on the expression levels of interleukin-6, a NF-kB specific target gene.

Conclusion

Induction of apoptosis of osteoclasts could be an important strategy both in interfering with rheumatoid arthritis complications of the bone skeleton leading to joint destruction, and preventing and reducing osteoporosis. Accordingly, we suggest the application of Emblica officinalis extracts as an alternative tool for therapy applied to bone diseases.

188Re-labelled gemcitabine/bisphosphonate (Gem/BP): a multi-functional, bone-specific agent as a potential treatment for bone metastases

PURPOSE

This study investigated the bone-binding affinity and biodistribution of a (188)Re-labelled gemcitabine/bisphosphonate (Gem/BP) conjugate, a multi-functional drug designed to deliver tumour-specific combined radiotherapy and chemotherapy to the bone using the high bone-binding affinity of the bisphosphonate group.

METHODS

The Gem/BP conjugate was labelled at high radiochemical purity with (188)Re. The bone-binding affinity of the (188)Re-Gem/BP was studied in vitro in purified hydroxyapatite emulsion and powdered bovine bone. In vivo biodistribution studies were carried out in normal BALB/c mice.

RESULTS

(188)Re-Gem/BP demonstrated strong and stable binding in both in vitro systems. In vivo (188)Re-Gem/BP showed bone uptake, rapid blood clearance and rapid elimination of unbound activity. The bone tissue demonstrated the highest concentration of bound radioactivity exempting the kidneys. Approximately 67% of retained whole-body activity was bound to the bone at 8 h after (188)Re-Gem/BP administration.

CONCLUSIONS

(188)Re-Gem/BP demonstrated high, selective and persistent bone binding and can be considered as a model compound for multi-functional bone-specific therapy for bone metastases.

Radioisotopes and vertebral augmentation: dosimetric analysis of a novel approach for the treatment of malignant compression fractures

PURPOSE

Vertebral compression fractures (VCFs), a major cause of morbidity and debilitating pain, often results from secondary tumor metastases to the skeleton. Vertebral augmentation is a palliative technique developed to treat VCFs and involves the injection of polymethyl methacrylate (PMMA) to augment the fractured vertebral body. The authors investigate the feasibility of radionuclide therapy coupled with vertebral augmentation to treat both the tumor metastases and VCFs. Six therapeutic radioisotopes, uniformly mixed in a PMMA bolus, were investigated for their dosimetric properties.

METHODS AND MATERIALS

The MCNP5 Monte Carlo computer code was used to characterize the therapeutic dosimetric distribution within a cortical bone phantom for a 1 mm radial bolus of isotope-infused PMMA. Based on these data, the minimum activity required for a therapeutic treatment was calculated.

RESULTS

The dosimetry from beta emitting Y-90, P-32, and Ho-166 decreased to 10% of its maximum therapeutic dose (R10%) after traveling 1.20 mm, 1.03 mm, and 0.97 mm, respectively, through cortical bone. Low photon energy I-125 had a slightly larger calculated R10% of 1.32 mm. Although F-18 and Tc-99m exhibited a more uniform distribution (R10%=1.72 mm and 1.94 mm, respectively), the lower dosimetric gradients resulted in significantly greater therapeutic implant activities relative to the other isotopes studied in this report.

CONCLUSIONS

Radionuclide therapy coupled with vertebral augmentation is shown to be a feasible technique for the treatment of secondary skeletal metastases and its resulting side effects. Future studies will include a full clinical investigation to determine optimal treatment isotope(s).

Transforming growth factor beta derived from bone matrix promotes cell proliferation of prostate cancer and osteoclast activation-associated osteolysis in the bone microenvironment

Metastatic prostate tumors in the bone microenvironment stimulate bone resorption, resulting in release of growth factors from the bone matrix that play important roles in tumor growth and osteoclast induction. Transforming growth factor beta (TGFbeta) is one of the most abundantly stored cytokines in bone matrix, regulating diverse biological activities. Here we evaluate its involvement in prostate tumor growth in the bone microenvironment, comparing with tumor growth in the subcutaneous microenvironment as a control. Rat prostate tumors were transplanted onto the cranial bone and into the subcutis of F344 male rats. Tumor cell proliferation, apoptosis, and TGFbeta signal transduction were compared between the tumor-bone interface and the tumor-subcutaneous interface. Effects of TGFbeta on osteoclast differentiation were also evaluated in vitro. Inhibitory effects of TGFbeta receptor 1 antisense oligonucleotide on TGFbeta signaling, osteolysis, osteoblasts, and tumor growth were examined in vivo. Osteolytic changes were extensively observed at the tumor-bone interface, where the TGFbeta level, TGFbeta signal transduction, and tumor cell proliferation were higher than at the tumor-subcutaneous interface. In vitro treatment with receptor activator of nuclear factor-kappaB ligand induced osteoclast differentiation of bone marrow stromal cells, and additional exposure to TGFbeta exerted promotive effects on osteoclast induction. Intratumoral injection of TGFbeta receptor 1 antisense oligonucleotide significantly reduced TGFbeta signal transduction, osteolysis, induction of osteoclast and osteoblast, and tumor cell proliferation. Thus, we experimentally show that TGFbeta derived from bone matrix promotes cell proliferation of rat prostate cancer and osteoclast activation-associated osteolysis in the bone microenvironment.

Evaluating distant metastases in breast cancer: from biology to outcomes

There is an urgent need to understand distant metastases in breast cancer as they are the most lethal form of recurrence and a major cause of mortality in patients. Some predictors for distant metastases, including nodal status, tumor grade, and hormonal status, are useful in identifying patients at increased risk for distant metastases. Adjuvant endocrine therapy has been the treatment of choice for postmenopausal women with hormone-sensitive breast cancer, and some therapies have shown significant reductions in the risk of distant metastases. Skeletal metastases in breast cancer are treated with bisphosphonates with a certain level of success. With more new agents undergoing clinical trials, a thorough review of the specific and long-term safety of these agents is essential, as is a better understanding of the deterioration in the quality of life and cost concerns of patients who develop distant metastases. Gene-expression profiling is a new entrant in the field of distant metastases diagnosis, which is largely successful in defining gene signatures that predict the development of distant metastases. This review will discuss the biology and the impact of distant metastases on outcomes for patients with breast cancer; it also encompasses the current status, emerging focus, and future perspectives in treatment of skeletal metastases in patients with breast cancer.

Molecular pathogenesis and its therapeutic modalities of lung cancer metastasis to bone

Bone metastasis is a critical problem of lung cancer patients. Reproducible animal models of lung cancer bone metastasis, like NK-cell depleted SCID mouse model with SCB-5 cells, are useful to explore the molecular mechanism and search of molecular targets. SBC-5 cells overexpressed PTHrP and that treatment with anti-PTHrP neutralizing antibody inhibited the production of bone metastases of SBC-5 cells in the NK-cell depleted SCID mouse model, indicating the critical role of PTHrP in bone metastasis in this model. In addition, we demonstrated that several compounds, including bisphosphonates and reveromycin A, potentially suppress osteoclast-activity were beneficial for the treatments of bone metastasis. Multi-modality therapy may be necessary for further augmenting the therapeutic efficacy against lung cancer bone metastasis.

Stress fractures of the second metatarsal base occur in nondancers

Stress fractures of the base of the second metatarsal are common in ballet dancers and essentially are unreported in nondancers. We presumed base of the second metatarsal stress fractures in nondancers occur in a wide variety of individuals regardless of demographics, are highly associated with athletic activities, and have specific examination findings and poor clinical outcomes. Using a retrospective chart review, we identified 12 stress fractures at the base of the second metatarsal (nine patients) in nondancers. Our review suggests second metatarsal base stress fractures occur in nondancers in a diverse population, and nonoperative treatment provides limited success. Advanced radiographic study, specifically MRI, is useful to assist the early diagnosis and prognostication. All of the stress fractures were treated nonoperatively; six fractures (50%) developed nonunion and five underwent subsequent surgery. The surgery for nonunion provided successful outcomes; however, risk factors such as low bone mass and comorbidities may have played important roles in the prognosis.