Zoledronic acid as a new adjuvant therapeutic strategy for Ewing's sarcoma patients

Current use of Molecular Mechanisms and Signaling Pathways in Targeted Therapy of Prostate Cancer

Prostate cancer (PC) is identified as a heterogeneous disease. About 20 to 30% of PC patients experience cancer recurrence, characterized by an increase in the antigen termed serum prostate-specific antigen (PSA). Clinical recurrence of PC commonly occurs after five years. Metastatic castration-resistant prostate cancer (mCRPC) has an intricate genomic background. Therapies that target genomic changes in DNA repair signaling pathways have been progressively approved in the clinic. Innovative therapies like targeting signaling pathways, bone niche, immune checkpoint, and epigenetic marks have been gaining promising results for better management of PC cases with bone metastasis. This review article summarizes the recent consideration of the molecular mechanisms and signaling pathways involved in local and metastatic prostate cancer, highlighting the clinical insinuations of the novel understanding.

Pseudomyogenic hemangioendothelioma with bone and soft tissue involvement with favorable response to pamidronate: a case report and systematic review of the literature

Pseudomyogenic hemangioendothelioma (PMH) can be a challenge for diagnosis and might be confused with other tumors, such as epithelioid sarcoma. Here we present a case and a systematic review of the literature to identify and discuss PMH treatment in primary bone involvement. A 25-year-old woman was referred for bone pain (10/10) in the left lower limb. Magnetic resonance imaging (MRI) showed multiple bone lesions (left femur, tibia, patella, ankle, and foot) with well-defined borders without signs of local aggressiveness. Positron Emission Tomography-Computed Tomography (PET-CT) showed multiple metabolic musculoskeletal lesions in the left lower limb. A CT scan-guided biopsy was performed. Histological and immunohistochemical findings confirmed the diagnosis of PMH. After treatment with intravenous pamidronate (90 mg/monthly), the patient had clinical improvement, mild pain 2/10 without the use of non-steroidal anti-inflammatory drugs or opiates. Follow-up was assessed by MRI and PET-CT. PET-CT showed metabolic resolution of most of the bone and muscular lesions and a significant improvement of the femoral lesion. MRI showed that the lesions in the left femur, tibia, and foot had a marked decrease in size without intravenous post-contrast enhancement and smaller lesions had disappeared. After a 3-year follow-up, PET-CT showed no metabolically active images. Literature review identified 31 records including 58 clinical cases of PMH with primary bone involvement and treatment description for qualitative analysis. Most lesions (69%) were treated by local excision or curettage. In addition, amputations were performed in a significant percentage of cases (20.7%). In the last years, mTOR inhibitors (n = 7) and anti-resorptive treatments (n = 4) were considered as alternative treatment options, especially in multifocal lesions.

Human Serum Enhances Biomimicry of Engineered Tissue Models of Bone and Cancer

For decades, fetal bovine serum (FBS) has been used routinely for culturing many cell types, based on its empirically demonstrated effects on cell growth, and the lack of suitable non-xenogeneic alternatives. The FBS-based culture media do not represent the human physiological conditions, and can compromise biomimicry of preclinical models. To recapitulate in vitro the features of human bone and bone cancer, we investigated the effects of human serum and human platelet lysate on modeling osteogenesis, osteoclastogenesis, and bone cancer in two-dimensional (2D) and three-dimensional (3D) settings. For monitoring tumor growth within tissue-engineered bone in a non-destructive fashion, we generated cancer cell lines expressing and secreting luciferase. Culture media containing human serum enhanced osteogenesis and osteoclasts differentiation, and provided a more realistic in vitro mimic of human cancer cell proliferation. When human serum was used for building 3D engineered bone, the tissue recapitulated bone homeostasis and response to bisphosphonates observed in native bone. We found disparities in cell behavior and drug responses between the metastatic and primary cancer cells cultured in the bone niche, with the effectiveness of bisphosphonates observed only in metastatic models. Overall, these data support the utility of human serum for bioengineering of bone and bone cancers.

Ewing Sarcoma-Diagnosis, Treatment, Clinical Challenges and Future Perspectives

Ewing sarcoma, a highly aggressive bone and soft-tissue cancer, is considered a prime example of the paradigms of a translocation-positive sarcoma: a genetically rather simple disease with a specific and neomorphic-potential therapeutic target, whose oncogenic role was irrefutably defined decades ago. This is a disease that by definition has micrometastatic disease at diagnosis and a dismal prognosis for patients with macrometastatic or recurrent disease. International collaborations have defined the current standard of care in prospective studies, delivering multiple cycles of systemic therapy combined with local treatment; both are associated with significant morbidity that may result in strong psychological and physical burden for survivors. Nevertheless, the combination of non-directed chemotherapeutics and ever-evolving local modalities nowadays achieve a realistic chance of cure for the majority of patients with Ewing sarcoma. In this review, we focus on the current standard of diagnosis and treatment while attempting to answer some of the most pressing questions in clinical practice. In addition, this review provides scientific answers to clinical phenomena and occasionally defines the resulting translational studies needed to overcome the hurdle of treatment-associated morbidities and, most importantly, non-survival.

Targeting Tumor-Associated Macrophages in the Pediatric Sarcoma Tumor Microenvironment

For many pediatric sarcoma patients, multi-modal therapy including chemotherapy, radiation, and surgery is sufficient to cure their disease. However, event-free and overall survival rates for patients with more advanced disease are grim, necessitating the development of novel therapeutic approaches. Within many pediatric sarcomas, the normal immune response, including recognition and destruction of cancer cells, is lost due to the highly immune suppressive tumor microenvironment (TME). In this setting, tumor cells evade immune detection and capitalize on the immune suppressed microenvironment, leading to unchecked proliferation and metastasis. Recent preclinical and clinical approaches are aimed at understanding this immune suppressive microenvironment and employing cancer immunotherapy in an attempt to overcome this, by renewing the ability of the immune system to recognize and destroy cancer cells. While there are several factors that drive the attenuation of immune responses in the sarcoma TME, one of the most remarkable are tumor associated macrophage (TAMs). TAMs suppress immune cytolytic function, promote tumor growth and metastases, and are generally associated with a poor prognosis in most pediatric sarcoma subtypes. In this review, we summarize the mechanisms underlying TAM-facilitated immune evasion and tumorigenesis and discuss the potential therapeutic application of TAM-focused drugs in the treatment of pediatric sarcomas.

Bisphosphonates in common pediatric and adult bone sarcomas

The therapeutic strategies proposed currently for bone sarcomas are based on neo-adjuvant chemotherapy, delayed en-bloc wide resection, and adjuvant chemotherapy. Unfortunately, bone sarcomas are characterized by high rates of poor drug response, with a high risk of drug resistance, local recurrence and/or a high propensity for induced metastases. The pathogenesis of bone sarcomas is strongly associated with dysregulation of local bone remodeling and increased osteolysis that plays a part in tumor development. In this context, bisphosphonates (BPs) have been proposed as a single agent or in combination with conventional drugs to block bone resorption and the vicious cycle established between bone and sarcoma cells. Pre-clinical in vitro studies revealed the potential "anti-tumor" activities of nitrogen-bisphosphonates (N-BPs). In pre-clinical models, N-BPs reduced significantly primary tumor growth in osteosarcoma and Ewing sarcoma, and the installation of lung metastases. In chondrosarcoma, N-BPs reduced the recurrence of local tumors after intralesional curettage, and increased overall survival. In pediatric and adult osteosarcoma patients, N-BPs have been assessed in combination with conventional chemotherapy and surgery in randomized phase 3 studies with no improvement in clinical outcome. The lack of benefit may potentially be explained by the biological impact of N-BPs on macrophage differentiation/recruitment which may alter CD8⁺-T lymphocyte infiltration. Thanks to their considerable affinity for the mineralized extracellular matrix, BPs are an excellent platform for drug delivery in malignant bone sites with reduced systemic toxicity, which opens up new opportunities for their future use.

Immune system and bone microenvironment: rationale for targeted cancer therapies

Osteoimmunology was coined about twenty years ago to identify a strict cross talk between bone niche and immune system both in physiological and pathological activities, including cancer. Several molecules are involved in the complex interaction between bone niche, immune and cancer cells. The Receptor Activator of NF-kB (RANK)/RANK Ligand (RANKL/Osteoprotegerin (OPG) pathway plays a crucial role in bone cells/cancer interactions with subsequently immune system control failure, bone destruction, inhibition of effect and metastasis outcome. The bidirectional cross talk between bone and immune system could became a potential target for anticancer drugs. Several studies evidenced a direct anticancer role with improved survival of bone-targeted therapies such as bisphosphonates and RANKL antagonist Denosumab. Conversely, initial data evidenced a possible anti-bone resorption effect of systemic anticancer drugs through and immunomodulation activity, i.e. new generation antiandrogens (Abiraterone) in prostate cancer. All data could open a future rationale of combined bone, immunologic and targeted therapies in cancer treatment.

International randomised controlled trial for the treatment of newly diagnosed EWING sarcoma family of tumours - EURO EWING 2012 Protocol

BACKGROUND

Although there have been multiple randomised trials in newly diagnosed Ewing sarcoma family of tumours (ESFT) and these have been conducted over many years and involved many international cooperative groups, the outcomes for all stages of disease have plateaued. Internationally, the standard treatment of ESFT is not defined, and there is a need to add new agents other than conventional chemotherapy to improve outcomes. This trial will compare two different induction/consolidation chemotherapy regimens: (1) vincristine, ifosfamide, doxorubicin and etoposide (VIDE) induction and vincristine, actinomycin D, ifosfamide or cyclophosphamide, or busulfan and mephalan (VAI/VAC/BuMel) consolidation and (2) vincristine, doxorubicin, cyclophosphamide, ifosfamide and etoposide (VDC/IE) induction and ifosfamide and etoposide, vincristine and cyclophosphamide, vincristine, actinomycin D and ifosfamide, or busulfan and mephalan (IE/VC/VAI/BuMel) consolidation (randomisation 1, or R1). A second randomisation (R2) will determine whether the addition of zoledronic acid to consolidation chemotherapy, as assigned at R1, is associated with improved clinical outcome.

METHODS

EURO EWING 2012 is an international, multicentre, phase III, open-label randomised controlled trial. There are two randomisations: R1 and R2. Patients are randomly assigned at two different time points: at entry to the trial (R1) and following local control therapy (R2). The primary outcome measure is event-free survival. The secondary outcome measures include overall survival, adverse events and toxicity, histological response of the primary tumour, response of the primary tumour, regional lymph nodes or metastases (or both), and achievement of local control at the end of treatment.

DISCUSSION

This study will establish which is the "standard regimen" of chemotherapy, taking into account both clinical outcomes and toxicity. This will form the chemotherapy backbone for future interventional studies where we may want to add new targeted agents. It will also determine the role of zoledronic acid in conjunction with the separate EE2008 trial. Any trial in ESFT needs to take into account the rarity of the tumour and consider that international cooperation is needed to provide answers in a timely manner.

TRIAL REGISTRATION

Registered with EudraCT number 2012-002107-17 on 26 February 2012. Registered with ISRCTN number 54540667 on 4 November 2013.

New Insights about the Wnt/β-Catenin Signaling Pathway in Primary Bone Tumors and Their Microenvironment: A Promising Target to Develop Therapeutic Strategies?

Osteosarcoma and Ewing sarcoma are the most common malignant primary bone tumors mainly occurring in children, adolescents and young adults. Current standard therapy includes multidrug chemotherapy and/or radiation specifically for Ewing sarcoma, associated with tumor resection. However, patient survival has not evolved for the past decade and remains closely related to the response of tumor cells to chemotherapy, reaching around 75% at 5 years for patients with localized forms of osteosarcoma or Ewing sarcoma but less than 30% in metastatic diseases and patients resistant to initial chemotherapy. Despite Ewing sarcoma being characterized by specific EWSR1-ETS gene fusions resulting in oncogenic transcription factors, currently, no targeted therapy could be implemented. It seems even more difficult to develop a targeted therapeutic strategy in osteosarcoma which is characterized by high complexity and heterogeneity in genomic alterations. Nevertheless, the common point between these different bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Therefore, targeting different actors of the bone tumor microenvironment has been hypothesized to develop new therapeutic strategies. In this context, it is well known that the Wnt/β-catenin signaling pathway plays a key role in cancer development, including osteosarcoma and Ewing sarcoma as well as in bone remodeling. Moreover, recent studies highlight the implication of the Wnt/β-catenin pathway in angiogenesis and immuno-surveillance, two key mechanisms involved in metastatic dissemination. This review focuses on the role played by this signaling pathway in the development of primary bone tumors and the modulation of their specific microenvironment.

Effective Use of Sirolimus and Zoledronic Acid for Multiosteotic Pseudomyogenic Hemangioendothelioma of the Bone in a Child: Case Report and Review of Literature

Pseudomyogenic hemangioendothelioma (PMH) is a rare neoplasm with vascular and sarcomatous elements, unpredictable course, and uncommon metastatic or fatal potential. Although systemic chemotherapy has been reported with variable success, generally accepted treatment is aggressive surgery with wide margins. Evidence-based treatment options are lacking, and lack of clear prognostic features poses a risk of undertreatment or overtreatment with associated morbidity and mortality. We report the use of initial systemic therapy with oral sirolimus (SIR) and IV zoledronic acid (ZA) to induce a sustained clinical response and avoidance of amputation in a 6-year-old boy. At 37 months after diagnosis, our patient remains in sustained clinical remission as documented by x-ray, MRI, and PET-CT with return of normal mobility/activity and resolution of swelling and pain. Literature review identified 20 cases of pediatric and young adult patients with PMH, of which 7 received some form of systemic therapy. To the best of our knowledge, our patient represents the youngest reported case of PMH and the first successful and limb-sparing utilization of systemic chemotherapy as primary treatment for PMH.

Murine Models of Bone Sarcomas

This chapter describes the procedures for inducing bone sarcoma in mice. Two models based on inoculation of cancer cells in paraosseous and intraosseous site will be described. In addition to providing technical aspects of anesthesia and surgical options, key information of cell preparation and postoperative follow-up will be discussed.

Isolation of circulating tumor cells in a preclinical model of osteosarcoma: Effect of chemotherapy

Osteosarcoma is a rare primary bone tumor, which mainly affects children and adolescents and has a poor prognosis, especially for patients with metastatic disease. A poor therapeutic response to the conventional chemotherapy is observed with the development of lung metastases, highlighting the need for improving the current regimens and the identification of early markers of the recurrent and metastatic disease. Circulating Tumour Cells (CTCs) play a key role in the metastatic process and could be powerful biomarkers of the progressive disease. The present study aimed to isolate CTCs by using a pre-clinical model of human osteosarcoma and to monitor their kinetic of release and their modulation by ifosfamide. CTCs were detectable into the bloodstream before any palpable primary tumors. Ifosfamide increased CTCs count and in contrast decreased the number of lung tumor nodules. On established tumors, ifosfamide slowed down the tumour growth and did not modulate CTC count that could be explained by a release of cancer cells from the primary tumour with reduced properties for inducing lung metastases. This report highlights the biological interest of CTCs in osteosarcoma.

Ewing sarcoma

Ewing sarcoma is the second most frequent bone tumour of childhood and adolescence that can also arise in soft tissue. Ewing sarcoma is a highly aggressive cancer, with a survival of 70-80% for patients with standard-risk and localized disease and ~30% for those with metastatic disease. Treatment comprises local surgery, radiotherapy and polychemotherapy, which are associated with acute and chronic adverse effects that may compromise quality of life in survivors. Histologically, Ewing sarcomas are composed of small round cells expressing high levels of CD99. Genetically, they are characterized by balanced chromosomal translocations in which a member of the FET gene family is fused with an ETS transcription factor, with the most common fusion being EWSR1-FLI1 (85% of cases). Ewing sarcoma breakpoint region 1 protein (EWSR1)-Friend leukaemia integration 1 transcription factor (FLI1) is a tumour-specific chimeric transcription factor (EWSR1-FLI1) with neomorphic effects that massively rewires the transcriptome. Additionally, EWSR1-FLI1 reprogrammes the epigenome by inducing de novo enhancers at GGAA microsatellites and by altering the state of gene regulatory elements, creating a unique epigenetic signature. Additional mutations at diagnosis are rare and mainly involve STAG2, TP53 and CDKN2A deletions. Emerging studies on the molecular mechanisms of Ewing sarcoma hold promise for improvements in early detection, disease monitoring, lower treatment-related toxicity, overall survival and quality of life.

Bisphosphonate conjugation for bone specific drug targeting

Bones provide essential functions and are sites of unique biochemistry and specialized cells, but can also be sites of disease. The treatment of bone disorders and neoplasia has presented difficulties in the past, and improved delivery of drugs to bone remains an important goal for achieving effective treatments. Drug targeting strategies have improved drug localization to bone by taking advantage of the high mineral concentration unique to the bone hydroxyapatite matrix, as well as tissue-specific cell types. The bisphosphonate molecule class binds specifically to hydroxyapatite and inhibits osteoclast resorption of bone, providing direct treatment for degenerative bone disorders, and as emerging evidence suggests, cancer. These bone-binding molecules also provide the opportunity to deliver other drugs specifically to bone by bisphosphonate conjugation. Bisphosphonate bone-targeted therapies have been successful in treatment of osteoporosis, primary and metastatic neoplasms of the bone, and other bone disorders, as well as refining bone imaging. In this review, we focus upon the use of bisphosphonate conjugates with antineoplastic agents, and overview bisphosphonate based imaging agents, nanoparticles, and other drugs. We also discuss linker design potential and the current state of bisphosphonate conjugate research progress. Ongoing investigations continue to expand the possibilities for bone-targeted therapeutics and for extending their reach into clinical practice.

Small animal models for the study of bone sarcoma pathogenesis:characteristics, therapeutic interests and limitations

Osteosarcoma, Ewing sarcoma and chondrosarcoma are the three main entities of bone sarcoma which collectively encompass more than 50 heterogeneous entities of rare malignancies. In contrast to osteosarcoma and Ewing sarcoma which mainly affect adolescents and young adults and exhibit a high propensity to metastasise to the lungs, chondrosarcoma is more frequently observed after 40 years of age and is characterised by a high frequency of local recurrence. The combination of chemotherapy, surgical resection and radiotherapy has contributed to an improved outcome for these patients. However, a large number of patients still suffer significant therapy related toxicities or die of refractory and metastatic disease. To better delineate the pathogenesis of bone sarcomas and to identify and test new therapeutic options, major efforts have been invested over the past decades in the development of relevant pre-clinical animal models. Nowadays, in vivo models aspire to mimic all the steps and the clinical features of the human disease as accurately as possible and should ideally be manipulable. Considering these features and given their small size, their conduciveness to experiments, their affordability as well as their human-like bone-microenvironment and immunity, murine pre-clinical models are interesting in the context of these pathologies. This chapter will provide an overview of the murine models of bone sarcomas, paying specific attention for the models induced by inoculation of tumour cells. The genetically-engineered mouse models of bone sarcoma will also be summarized.

Biology of Bone Sarcomas and New Therapeutic Developments

Bone sarcomas are tumours belonging to the family of mesenchymal tumours and constitute a highly heterogeneous tumour group. The three main bone sarcomas are osteosarcoma, Ewing sarcoma and chondrosarcoma each subdivided in diverse histological entities. They are clinically characterised by a relatively high morbidity and mortality, especially in children and adolescents. Although these tumours are histologically, molecularly and genetically heterogeneous, they share a common involvement of the local microenvironment in their pathogenesis. This review gives a brief overview of their specificities and summarises the main therapeutic advances in the field of bone sarcoma.

Tissue-Engineered Model of Human Osteolytic Bone Tumor

Ewing's sarcoma (ES) is a poorly differentiated pediatric tumor of aggressive behavior characterized by propensity to metastasize to bone. Interactions between the tumor and bone cells orchestrate a vicious cycle in which tumor cells induce osteoclast differentiation and activation to cause osteolytic lesions, broken bones, pain, and hypercalcemia. The lack of controllable models that can recapitulate osteolysis in ES impedes the development of new therapies and limits our understanding of how tumor cells invade bone. In response to this need, tissue-engineered models are now being developed to enable quantitative, predictive studies of human tumors. In this study, we report a novel bioengineered model of ES that incorporates the osteolytic process. Our strategy is based on engineering human bone containing both osteoclasts and osteoblasts within three-dimensional mineralized bone matrix. We show that the bone matrix is resorbed by mature osteoclasts while the new bone matrix is formed by osteoblasts, leading to calcium release and bone remodeling. Introduction of ES cell aggregates into the bone niche induced decreases in bone density, connectivity, and matrix deposition. Additionally, therapeutic reagents, such as zoledronic acid, which have demonstrated efficacy in ES treatment, inhibited bone resorption mediated by osteoclasts in the tumor model.

In Vivo Model for Testing Effect of Hypoxia on Tumor Metastasis

Hypoxia has been implicated in the metastasis of Ewing sarcoma (ES) by clinical observations and in vitro data, yet direct evidence for its pro-metastatic effect is lacking and the exact mechanisms of its action are unclear. Here, we report an animal model that allows for direct testing of the effects of tumor hypoxia on ES dissemination and investigation into the underlying pathways involved. This approach combines two well-established experimental strategies, orthotopic xenografting of ES cells and femoral artery ligation (FAL), which induces hindlimb ischemia. Human ES cells were injected into the gastrocnemius muscles of SCID/beige mice and the primary tumors were allowed to grow to a size of 250 mm³. At this stage either the tumors were excised (control group) or the animals were subjected to FAL to create tumor hypoxia, followed by tumor excision 3 days later. The efficiency of FAL was confirmed by a significant increase in binding of hypoxyprobe-1 in the tumor tissue, severe tumor necrosis and complete inhibition of primary tumor growth. Importantly, despite these direct effects of ischemia, an enhanced dissemination of tumor cells from the hypoxic tumors was observed. This experimental strategy enables comparative analysis of the metastatic properties of primary tumors of the same size, yet significantly different levels of hypoxia. It also provides a new platform to further assess the mechanistic basis for the hypoxia-induced alterations that occur during metastatic tumor progression in vivo. In addition, while this model was established using ES cells, we anticipate that this experimental strategy can be used to test the effect of hypoxia in other sarcomas, as well as tumors orthotopically implanted in sites with a well-defined blood supply route.

RANKL blockade prevents and treats aggressive osteosarcomas

Osteosarcoma (OS) is the most common primary bone cancer, which occurs primarily in children and adolescents, severely affecting survivors' quality of life. Despite its chemosensitivity and treatment advances, long-term survival rates for OS patients have stagnated over the last 20 years. Thus, it is necessary to develop new molecularly targeted therapies for this metastatic bone cancer. Mutations in TP53 and RB are linked to OS predisposition and to the evolution of spontaneous OS. We established receptor activator of nuclear factor κB ligand (RANKL) as a therapeutic target for suppression and prevention of OS. Combined conditional osteoblast-specific deletions of Rb, p53, and the protein kinase A (PKA) regulatory subunit Prkar1α genes in genetically engineered mouse models (GEMMs) generate aggressive osteosarcomas, characterized by PKA, RANKL, and osteoclast hyperactivity. Whole-body Rankl deletion completely abrogates tumorigenesis. Although osteoblastic Rank deletion has little effect, osteoclastic Rank deletion delays tumorigenesis and prolongs life span. The latter is associated with inactivation of osteoclastogenesis and up-regulation of the tumor suppressor phosphatase and tensin homolog (PTEN). Further, we use these GEMMs as preclinical platforms to show that RANKL blockade with RANK-Fc arrests tumor progression and improves survival and also inhibits lung metastasis. Moreover, preemptive administration of RANK-Fc completely prevents tumorigenesis in mice highly predisposed to this aggressive cancer. Denosumab, a fully human monoclonal antibody against RANKL, is currently used to treat patients with osteoporosis or bone metastases. Our studies provide a strong rationale to consider RANKL blockade for the treatment and prevention of aggressive RANKL-overexpressing OS in humans.

Management of Ewing sarcoma family of tumors: Current scenario and unmet need

Ewing sarcoma family tumors (ESFT) are heterogeneous, aggressive group of disease with peak incidence in adolescent and young adults. The outcome has been improved dramatically from 10% with surgery and radiotherapy alone to 65%-70% now, in localized disease, with the introduction of chemotherapy. Chemotherapy regimen evolved from single agent to multiagent with effort of many cooperative clinical trials over decades. The usual treatment protocol include introduction of multi-agent chemotherapy in neoadjuvant setting to eradicate systemic disease with timely incorporation of surgery and/or radiotherapy as local treatment modality and further adjuvant chemotherapy to prevent recurrence. Risk adapted chemotherapy in neoadjuvant and adjuvant setting along with radiotherapy has been used in many international collaborative trials and has resulted in improved outcome, more so in patients with localized disease. The role of high dose chemotherapy with stem cell rescue is still debatable. The outcome of patients with metastatic disease is dismal with long term outcome ranges from 20%-40% depending on the sites of metastasis and intensity of treatment. There is a huge unmet need to improve outcome further, more so in metastatic setting. Novel therapy targeting the molecular pathways and pathogenesis of ESFT is very much required. Here we have discussed the current standard of management in patients with ESFT, investigational targeted or novel therapies along with future promises.

Bone Tumor Environment as a Potential Therapeutic Target in Ewing Sarcoma

Ewing sarcoma is the second most common pediatric bone tumor, with three cases per million worldwide. In clinical terms, Ewing sarcoma is an aggressive, rapidly fatal malignancy that mainly develops not only in osseous sites (85%) but also in extra-skeletal soft tissue. It spreads naturally to the lungs, bones, and bone marrow with poor prognosis in the two latter cases. Bone lesions from primary or secondary (metastases) tumors are characterized by extensive bone remodeling, more often due to osteolysis. Osteoclast activation and subsequent bone resorption are responsible for the clinical features of bone tumors, including pain, vertebral collapse, and spinal cord compression. Based on the “vicious cycle” concept of tumor cells and bone resorbing cells, drugs, which target osteoclasts, may be promising agents as adjuvant setting for treating bone tumors, including Ewing sarcoma. There is also increasing evidence that cellular and molecular protagonists present in the bone microenvironment play a part in establishing a favorable “niche” for tumor initiation and progression. The purpose of this review is to discuss the potential therapeutic value of drugs targeting the bone tumor microenvironment in Ewing sarcoma. The first part of the review will focus on targeting the bone resorbing function of osteoclasts by means of bisphosphonates or drugs blocking the pro-resorbing cytokine receptor activator of NF-kappa B ligand. Second, the role of this peculiar hypoxic microenvironment will be discussed in the context of resistance to chemotherapy, escape from the immune system, or neo-angiogenesis. Therapeutic interventions based on these specificities could be then proposed in the context of Ewing sarcoma.

Bisphosphonates for cancer treatment: Mechanisms of action and lessons from clinical trials

A growing body of evidence points toward an important anti-cancer effect of bisphosphonates, a group of inexpensive, safe, potent, and long-term stable pharmacologicals that are widely used as osteoporosis drugs. To date, they are already used in the prevention of complications of bone metastases. Because the bisphosphonates can also reduce mortality in among other multiple myeloma, breast, and prostate cancer patients, they are now thoroughly studied in oncology. In particular, the more potent nitrogen-containing bisphosphonates have the potential to improve prognosis. The first part of this review will elaborate on the direct and indirect anti-tumoral effects of bisphosphonates, including induction of tumor cell apoptosis, inhibition of tumor cell adhesion and invasion, anti-angiogenesis, synergism with anti-neoplastic drugs, and enhancement of immune surveillance (e.g., through activation of γδ T cells and targeting macrophages). In the second part, we shed light on the current clinical position of bisphosphonates in the treatment of hematological and solid malignancies, as well as on ongoing and completed clinical trials investigating the therapeutic effect of bisphosphonates in cancer. Based on these recent data, the role of bisphosphonates is expected to further expand in the near future outside the field of osteoporosis and to open up new avenues in the treatment of malignancies.

Ewing Sarcoma: Current Management and Future Approaches Through Collaboration

Ewing sarcoma (ES) is an aggressive sarcoma of bone and soft tissue occurring at any age with a peak incidence in adolescents and young adults. The treatment of ES relies on a multidisciplinary approach, coupling risk-adapted intensive neoadjuvant and adjuvant chemotherapies with surgery and/or radiotherapy for control of the primary site and possible metastatic disease. The optimization of ES multimodality therapeutic strategies has resulted from the efforts of several national and international groups in Europe and North America and from cooperation between pediatric and medical oncologists. Successive first-line trials addressed the efficacy of various cyclic combinations of drugs incorporating doxorubicin, vincristine, cyclophosphamide, ifosfamide, etoposide, and dactinomycin and identified prognostic factors now used to tailor therapies. The role of high-dose chemotherapy is still debated. Current 5-year overall survival for patients with localized disease is 65% to 75%. Patients with metastases have a 5-year overall survival < 30%, except for those with isolated pulmonary metastasis (approximately 50%). Patients with recurrence have a dismal prognosis. The many insights into the biology of the EWS-FLI1 protein in the initiation and progression of ES remain to be translated into novel therapeutic strategies. Current options and future approaches will be discussed.

Bone Sarcomas in Pediatrics: Progress in Our Understanding of Tumor Biology and Implications for Therapy

The pediatric bone sarcomas osteosarcoma and Ewing sarcoma represent a tremendous challenge for the clinician. Though less common than acute lymphoblastic leukemia or brain tumors, these aggressive cancers account for a disproportionate amount of the cancer morbidity and mortality in children, and have seen few advances in survival in the past decade, despite many large, complicated, and expensive trials of various chemotherapy combinations. To improve the outcomes of children with bone sarcomas, a better understanding of the biology of these cancers is needed, together with informed use of targeted therapies that exploit the unique biology of each disease. Here we summarize the current state of knowledge regarding the contribution of receptor tyrosine kinases, intracellular signaling pathways, bone biology and physiology, the immune system, and the tumor microenvironment in promoting and maintaining the malignant phenotype. These observations are coupled with a review of the therapies that target each of these mechanisms, focusing on recent or ongoing clinical trials if such information is available. It is our hope that, by better understanding the biology of osteosarcoma and Ewing sarcoma, rational combination therapies can be designed and systematically tested, leading to improved outcomes for a group of children who desperately need them.

[Ewing sarcoma located in the mandible: A case report]

Ewing sarcoma is the second most common primary malignant bone cancer in children and adolescents. Clinical presentation is usually dominated by local pain and a palpable mass. These symptoms justify imaging investigations: the first one, when an osseous lesion is suspected, is usually a conventional radiograph in two planes. Ewing sarcoma appears as a poorly defined osteolytic lesion that may frequently be associated with cortical erosion or laminar periosteal response ("onion skin"). However, this aspect is not pathognomonic and the definitive diagnosis is made by biopsy. Absence of pain or an unusual localization can lead to misdiagnosis. We report the case of a 7-year-old boy with Ewing sarcoma located in the mandible with a clinical picture including progressive mandibular swelling but no pain.

Skeletal consequences of RANKL-blocking antibody (IK22-5) injections during growth: mouse strain disparities and synergic effect with zoledronic acid

High doses of bone resorption inhibitors are currently under evaluation in pediatric oncology. Previous works have evidenced transient arrest in long bone and skull bone growth and tooth eruption blockage when mice were treated with zoledronic acid (ZOL). The question of potential similar effects with a RANKL-blocking antibody (IK22.5) was raised. Sensitivity disparities in these inhibitors between mouse strains and synergic effects of zoledronic acid and a RANKL-blocking antibody were subsidiary questions. In order to answer these questions, newborn C57BL/6J and CD1 mice were injected every two or three days (4 injections in total so 7 or 10 days of treatment length) with high doses of a RANKL-blocking antibody. The consequences on the tibia, craniofacial bones and teeth were analyzed by μCT and histology at the end of the treatment and one, two and three months later. The results obtained showed that RANKL-blocking antibody injections induced a transient arrest of tibia and skull bone growth and an irreversible blockage of tooth eruption in C57BL/6J mice. In CD1 mice, tooth eruption defects were also present but only at much higher doses. Similar mouse strain differences were obtained with zoledronic acid. Finally, a synergic effect of the two inhibitors was evidenced. In conclusion as previously observed for bisphosphonates (ZOL), a RANKL-blocking antibody induced a transient arrest in long bone and skull bone growth and a blockage of tooth eruption with however disparities between mouse strains with regard to this last effect. A synergic effect of both bone resorption inhibitors was also demonstrated.

Cellular immunotherapy strategies for Ewing sarcoma

Ewing sarcoma is a rare cancer of bone and soft tissues defined by a specific chromosomal rearrangement. Preclinical development of immunological treatment strategies includes expansion of T cells with native or grafted T-cell receptor specificities for Ewing sarcoma-associated intracellular antigens, and T-cell engineering with chimeric antigen receptors targeting surface antigens. In vitro preactivated NK cells may also have activity in this cancer. Major challenges are the heterogeneity of antigen expression in individual Ewing sarcomas, and the coexpression of most candidate targets on normal cells. Moreover, homing of therapeutic effector cells to both primary and metastatic tumor sites and adequate function within the immunosuppressive tumor microenvironment will have to be ensured to allow for effective immune targeting of this cancer.

Inhibition of osteolysis and increase of bone formation after local administration of siRNA-targeting RANK in a polyethylene particle-induced osteolysis model

Receptor activator of nuclear factor kappa-B (RANK) and RANK-ligand are relevant targets for the treatment of polyethylene particle-induced osteolysis. This study assessed the local administration of siRNA, targeting both human RANK and mouse Rank transcripts in a mouse model. Four groups of mice were implanted with polyethylene (PE) particles in the calvaria and treated locally with 2.5, 5 and 10 μg of RANK siRNA or a control siRNA delivered by the cationic liposome DMAPAP/DOPE. The tissues were harvested at day 9 after surgery and evaluated by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) immunohistochemistry for macrophages and osteoblasts, and gene relative expression of inflammatory and osteolytic markers. 10 μg of RANK siRNA exerted a protective effect against PE particle-induced osteolysis, decreasing the bone loss and the osteoclastogenesis, demonstrated by the significant increase in the bone volume (P<0.001) and by the reduction in both the number of TRAP(+) cells and osteoclast activity (P<0.01). A bone anabolic effect demonstrated by the formation of new trabecular bone was confirmed by the increased immunopositive staining for osteoblast-specific proteins. In addition, 5 and 10 μg of RANK siRNA downregulated the expression of pro-inflammatory cytokines (P<0.01) without depletion of macrophages. Our findings show that RANK siRNA delivered locally by a synthetic vector may be an effective approach for reducing osteolysis and may even stimulate bone formation in aseptic loosening of prosthetic implants.

Bisphosphonate therapy in pediatric patients

Although for many decades bisphosphonates were used for adult bone loss, bisphosphonate administration in pediatric patients is new and was initiated in the past 15-year. The indications for pediatric bisphosphonates was extended to childhood malignancies with bone involvement, after additional effects were unveiled for bisphosphonates with recent research. In this article we review childhood bone loss and conditions with bone involvement in which bisphosphonate therapy have been used. We also review mechanisms of action of bisphosphonates, and present indications of bisphosphonate therapy in pediatric patients based on results of clinical trials.

The off-label use of targeted therapies in sarcomas: the OUTC'S program

Background

Few targeted therapies (TTs) are registered for sarcoma treatment despite numerous phase II studies and yet there are potential treatment options for patients after standard treatment escape. The French Sarcoma Group - Bone Tumor Study Group (GSF-GETO) created a national registry to evaluate the outcome of patients treated with off-label TTs.

Methods

Every consecutive sarcoma-patient receiving an off-label TT outside a clinical trial was included. The objective was to describe this patient efficacy and safety data in routine practice.

Results

From October 2008 to October 2011, 249 patients in 24 centers received 278 treatment lines with TTs. Twenty-five histological subtypes were included: most frequent were leiomyosarcoma (n = 48, receiving sorafenib in 63%, and sunitinib in 27%), GIST (n = 39, receiving sorafenib in 79%), and angiosarcoma (n =18, receiving sorafenib in 78%). The overall response rate to TTs was 15% (95% CI [10,6-20,2]), the disease control rate at 2 months was 59%. The median progression-free survival was 4,1 months (IC 95% [3,2-4,8]). Three complete responses were observed. No toxic death occurred, grade 3 and 4 toxicities were reported in 74 (27%) and 14 patients (5%) respectively.

Conclusion

Off-label TTs can be used for sarcoma patients in routine practice with an acceptable toxicity profile and efficacy similar to that reported in non-randomized clinical trials.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-870) contains supplementary material, which is available to authorized users.

Preclinical evidence of potential craniofacial adverse effect of zoledronic acid in pediatric patients with bone malignancies

High doses of zoledronic acid (ZOL), one of the most potent inhibitors of bone resorption, are currently evaluated in phase III clinical trials in Europe for the treatment of malignant pediatric primary bone tumors. The impact of such an intensive treatment on the craniofacial skeleton growth is a critical question in the context of patients with actively growing skeleton; in particular, in light of our previous studies evidencing that endochondral bone formation was transiently disturbed by high doses of ZOL. Two protocols adapted from pediatric treatments were developed for newborn mice (a total of 5 or 10 injections of ZOL 50μg/kg every two days). Their impact on skull bones and teeth growth was analyzed by X-rays, microCT and histology up to 3months after the last injection. ZOL administrations induced a transient delay of skull bone growth and an irreversible delay in incisor, first molar eruption and root elongation. Other teeth were affected, but most were erupted by 3months. Root histogenesis was severely impacted for all molars and massive odontogenic tumor-like structures were observed in all mandibular incisors. High doses of ZOL irreversibly disturbed teeth eruption and elongation, and delayed skull bone formation. These preclinical observations are essential for the follow-up of onco-pediatric patients treated with ZOL.

Pleiotropic effects of bisphosphonates on osteosarcoma

Osteosarcoma is the most common primary malignant tumor of bone and accounts for half of all primary skeletal malignancies in children and teenagers. The prognosis for patients who fail or progress on first-line chemotherapy protocols is poor, therefore, additional adjuvant therapeutic strategies are needed. A recent feasibility study has demonstrated that the nitrogen-containing bisphosphonate zoledronic acid (ZOL) can be combined safely with conventional chemotherapy. However, the pharmacodynamics of bisphosphonate therapy is not well characterized. Osteosarcoma is a highly angiogenic tumor. Recent reports of the anti-angiogenic effects of bisphosphonates prompted us to determine whether nitrogen-containing bisphosphonate (ZOL and alendronate) treatment attenuates osteosarcoma growth by inhibition of osteoclast activity, tumor-mediated angiogenesis, or direct inhibitory effects on osteosarcoma. Here, we demonstrate that bisphosphonates directly inhibit VEGFR2 expression in endothelial cells, as well as endothelial cell proliferation and migration. Additionally, bisphosphonates also decrease VEGF-A expression in osteosarcoma (K7M3) cells, resulting in reduced stimulation of endothelial cell migration in co-culture assays. ZOL also decreases VEGFR1 expression in aggressive osteosarcoma cell lines (K7M3, 143B) and induces apoptosis of these cells, but has negligible effects on less aggressive osteosarcoma cell lines (K12 and TE85). In vivo ZOL treatment results in significant reduction in osteosarcoma-initiated angiogenesis and tumor growth in a murine model of osteosarcoma. In conclusion, bisphosphonates have diverse growth inhibitory effects on osteosarcoma through: (1) activation of apoptosis and inhibition of cell proliferation, (2) inhibition of VEGF-A and VEGFR1 expression by tumor cells, (3) inhibition of tumor-induced angiogenesis, and (4) direct inhibitory actions on endothelial cells.

Bisphosphonates inhibit osteosarcoma-mediated osteolysis via attenuation of tumor expression of MCP-1 and RANKL

Osteosarcoma is the most common primary malignant tumor of bone and accounts for around 50% of all primary skeletal malignancies. In addition to novel chemotherapies, there is a need for adjuvant therapies designed to inhibit osteosarcoma proliferation and tumor-induced osteolysis to attenuate tumor expansion and metastasis. As such, studies on the efficacy of bisphosphonates on human osteosarcoma are planned after feasibility studies determined that the bisphosphonate zoledronic acid (ZOL) can be safely combined with conventional chemotherapy. However, the molecular mechanisms responsible for, and means of inhibiting, osteosarcoma-induced osteolysis are largely unknown. We establish that osteosarcoma growth directly correlates with tumor-induced osteolysis and activation of osteoclasts in vivo. In vitro, tumor cells were determined to expresses surface, but not soluble, receptor activator of NF-κB ligand (RANKL) and stimulated osteoclastogenesis in a manner directly proportional to their malignant potential. In addition, an aggressive osteosarcoma cell line was shown to secrete monocyte chemoattractant protein-1 (MCP-1), resulting in robust monocyte migration. Because MCP-1 is a key cytokine for monocyte recruitment and surface-bound RANKL strongly supports local osteoclastogenesis, we suggest that high levels of these signaling molecules are associated with the aggressive potential of osteosarcoma. Consistent with these findings, abundant expression of RANKL/MCP-1 was observed in tumor in vivo, and MCP-1 plasma levels strongly correlated with tumor progression and osteolysis. ZOL administration directly attenuates osteosarcoma production of RANKL/MCP-1, reducing tumor-induced bone destruction. In vivo, these findings also correlated with significant reduction in osteosarcoma growth. ZOL attenuates tumor-induced osteolysis, not only through direct inhibition of osteoclasts, but also through direct actions on tumor expression of osteoclast activators. These data provide insight regarding the effect of ZOL on osteosarcoma essential for designing the planned upcoming prospective randomized trials to determine the efficacy of bisphosphonates on osteosarcoma in humans.

Zoledronic acid inhibits pulmonary metastasis dissemination in a preclinical model of Ewing's sarcoma via inhibition of cell migration

Background

Ewing’s sarcoma (ES) is the second most frequent primitive malignant bone tumor in adolescents with a very poor prognosis for high risk patients, mainly when lung metastases are detected (overall survival <15% at 5 years). Zoledronic acid (ZA) is a potent inhibitor of bone resorption which induces osteoclast apoptosis. Our previous studies showed a strong therapeutic potential of ZA as it inhibits ES cell growth in vitro and ES primary tumor growth in vivo in a mouse model developed in bone site. However, no data are available on lung metastasis. Therefore, the aim of this study was to determine the effect of ZA on ES cell invasion and metastatic properties.

Methods

Invasion assays were performed in vitro in Boyden’s chambers covered with Matrigel. Matrix Metalloproteinase (MMP) activity was analyzed by zymography in ES cell culture supernatant. In vivo, a relevant model of spontaneous lung metastases which disseminate from primary ES tumor was induced by the orthotopic injection of 10⁶ human ES cells in the tibia medullar cavity of nude mice. The effect of ZA (50 μg/kg, 3x/week) was studied over a 4-week period. Lung metastases were observed macroscopically at autopsy and analysed by histology.

Results

ZA induced a strong inhibition of ES cell invasion, probably due to down regulation of MMP-2 and −9 activities as analyzed by zymography. In vivo, ZA inhibits the dissemination of spontaneous lung metastases from a primary ES tumor but had no effect on the growth of established lung metastases.

Conclusion

These results suggest that ZA could be used early in the treatment of ES to inhibit bone tumor growth but also to prevent the early metastatic events to the lungs.

Development of a preclinical orthotopic xenograft model of ewing sarcoma and other human malignant bone disease using advanced in vivo imaging

Ewing sarcoma and osteosarcoma represent the two most common primary bone tumours in childhood and adolescence, with bone metastases being the most adverse prognostic factor. In prostate cancer, osseous metastasis poses a major clinical challenge. We developed a preclinical orthotopic model of Ewing sarcoma, reflecting the biology of the tumour-bone interactions in human disease and allowing in vivo monitoring of disease progression, and compared this with models of osteosarcoma and prostate carcinoma. Human tumour cell lines were transplanted into non-obese diabetic/severe combined immunodeficient (NSG) and Rag2^−/−/γc^−/− mice by intrafemoral injection. For Ewing sarcoma, minimal cell numbers (1000–5000) injected in small volumes were able to induce orthotopic tumour growth. Tumour progression was studied using positron emission tomography, computed tomography, magnetic resonance imaging and bioluminescent imaging. Tumours and their interactions with bones were examined by histology. Each tumour induced bone destruction and outgrowth of extramedullary tumour masses, together with characteristic changes in bone that were well visualised by computed tomography, which correlated with post-mortem histology. Ewing sarcoma and, to a lesser extent, osteosarcoma cells induced prominent reactive new bone formation. Osteosarcoma cells produced osteoid and mineralised “malignant” bone within the tumour mass itself. Injection of prostate carcinoma cells led to osteoclast-driven osteolytic lesions. Bioluminescent imaging of Ewing sarcoma xenografts allowed easy and rapid monitoring of tumour growth and detection of tumour dissemination to lungs, liver and bone. Magnetic resonance imaging proved useful for monitoring soft tissue tumour growth and volume. Positron emission tomography proved to be of limited use in this model. Overall, we have developed an orthotopic in vivo model for Ewing sarcoma and other primary and secondary human bone malignancies, which resemble the human disease. We have shown the utility of small animal bioimaging for tracking disease progression, making this model a useful assay for preclinical drug testing.

In vitro antitumor effect of sodium butyrate and zoledronic acid combined with traditional chemotherapeutic drugs: a paradigm of synergistic molecular targeting in the treatment of Ewing sarcoma

Histone deacetylase inhibitors and bisphosphonates have a promising future in the treatment of cancer as targeted anticancer drugs, particularly when used together or in combination with other cytotoxic agents. However, the effects of these combined treatments have not yet been systematically evaluated in Ewing sarcoma. The in vitro effects on cellular proliferation, viability and survival were investigated in two Ewing sarcoma cell lines, SK-ES-1 and RD-ES. The cell lines were treated with sodium butyrate, a histone deacetylase inhibitor and zoledronic acid, a bisphosphonate, alone, together or in combination with chemotherapeutic drugs recommended for clinical treatment of Ewing sarcoma. The data demonstrated that the combination of sodium butyrate and zoledronic acid had a synergistic cytotoxic effect at 72 h following treatment, persisting for 10-14 days post-treatment, in both cell lines tested. All combinations between sodium butyrate or zoledronic acid and the traditional antineoplastic drugs (doxorubicin, etoposide and vincristine) demonstrated a synergistic cytotoxic effect at 72 h in SK-ES-1 and RD-ES cells, except for the combinations of sodium butyrate with vincristine and of zoledronic acid with doxorubicin, which showed only an additive effect in RD-ES cell lines as compared to each agent alone. These acute effects observed in both Ewing sarcoma cell lines were confirmed by the clonogenic assay. The present data suggest that combining histone deacetylase inhibitors and bisphosphonates with traditional chemotherapeutic drugs is a promising therapeutic strategy for the treatment of Ewing sarcoma, and provides a basis for further studies in this field.

The adolescent and young adult with cancer: state of the art -- bone tumors

Primary malignant bone tumors in the pediatric to young adult populations are relatively uncommon and account for about 6 % of all cancers in those less than 20 years old [1] and 3 % of all cancers in adolescents and young adults (AYA) within the age range of 15 to 29 years [2]. Osteosarcoma (OS) and Ewing's sarcoma (ES) comprise the majority of malignant bone tumors. The approach to treatment for both tumors consists of local control measures (surgery or radiation) as well as systemic therapy with high-dose chemotherapy. Despite earlier advances, there have been no substantial improvements in outcomes over the past several decades, particularly for patients with metastatic disease. This review summarizes the major advances in the treatment of OS and ES and the standard therapies available today, current active clinical trials, and areas of investigation into molecularly targeted therapies.

Chemotherapeutic and antiresorptive combination therapy suppressed lymphangiogenesis and induced osteonecrosis of the jaw-like lesions in mice

Osteonecrosis of the jaw (ONJ) is a serious adverse event that occurs predominantly in patients on both antiresorptive and antineoplastic therapies. However, how these combination therapies are connected to the high frequency of ONJ in this particular patient population is unclear. This study's aim was to determine a mechanism of ONJ associated with the combination therapy of antiresorptives and chemotherapeutics. Mice received zoledronic acid (ZA) in conjunction with melphalan or dexamethasone. The maxillary first molars were extracted 3 weeks after the initiation of treatment and wound healing assessed at 4 weeks post-extractions using microcomputed tomography and immunohistochemistry. Mice receiving the combination treatment of ZA and melphalan developed ONJ-like lesions, while ONJ-like lesions were not found in mice on ZA or melphalan monotherapy, or the combination treatment of ZA and dexamethasone. ONJ lesions were characterized by a lack of epithelium, exposed necrotic bone, severe inflammatory cell infiltration, and minimal bone formation. Fluorescent immunohistochemistry showed that lymphatic vessel formation was significantly suppressed in ONJ-like lesions with a concomitant decrease in F4/80(+) macrophages expressing vascular endothelial growth factor C (VEGFC). Interestingly, significantly suppressed lymphatics were also found in the draining lymph nodes of mice on the combination treatment of ZA and melphalan. Thus, suppressed lymphangiogenesis was strongly associated with the development of ONJ-like lesions in the current study. Since lymphangiogenesis is critical in the resolution of inflammation during wound healing, inflammation control may serve as a potential strategy to prevent ONJ.

Drugs targeting the bone microenvironment: new therapeutic tools in Ewing's sarcoma?

INTRODUCTION

Ewing's sarcoma (ES) is the second most frequent malignant primary bone tumour in children, adolescents and young adults. The overall survival is 60 - 70% at 5 years but still very poor for patients with metastases, disease relapse or for those not responding to chemotherapy. For these high risk patients, new therapeutic approaches are needed beyond conventional therapies (chemotherapy, surgery and radiation) such as targeted therapies.

AREAS COVERED

Transcriptomic and genomic analyses in ES have revealed alterations in genes that control signalling pathways involved in many other cancer types. To set up more specific approaches, it is reasonable to think that the particular microenvironment of these bone tumours is essential for their initiation and progression, including in ES. To support this hypothesis, preclinical studies using drugs targeting bone cells (bisphosphonate zoledronate, anti-receptor activator of NF-κB ligand strategies) showed promising results in animal models. This review will discuss the new targeted therapeutic options in ES, focusing more particularly on the ones modulating the bone microenvironment.

EXPERT OPINION

Targeting the microenvironment represents a new option for patients with ES. The proof-of-concept has been demonstrated in preclinical studies using relevant animal models, especially for zoledronate, which induced a strong inhibition of tumour progression in an orthotopic bone model.

Targeted therapies for bone sarcomas

Bone sarcomas include a very large number of tumour subtypes, which originate form bone and more particularly from mesenchymal stem cell lineage. Osteosarcoma, Ewing's sarcoma and chondrosarcoma, the three main bone sarcoma entities develop in a favourable microenvironment composed by bone cells, blood vessels, immune cells, based on the 'seed and soil theory'. Current therapy associates surgery and chemotherapy, however, bone sarcomas remain diseases with high morbidity and mortality especially in children and adolescents. In the past decade, various new therapeutic approaches emerged and target the tumour niche or/and directly the tumour cells by acting on signalling/metabolic pathways involved in cell proliferation, apoptosis or drug resistance. The present review gives a brief overview from basic to clinical assessment of the main targeted therapies of bone sarcoma cells.

Osteoprotegerin inhibits bone resorption and prevents tumor development in a xenogenic model of Ewing's sarcoma by inhibiting RANKL

Ewing's sarcoma (ES) associated with high osyeolytic lesions typically arises in the bones of children and adolescents. The development of multi-disciplinary therapy has increased current long-term survival rates to greater than 50% but only 20% for high risk group patients (relapse, metastases, etc.). Among new therapeutic approaches, osteoprotegerin (OPG), an anti-bone resorption molecule may represent a promising candidate to inhibit RANKL-mediated osteolytic component of ES and consequently to limit the tumor development. Xenogenic orthotopic models of Ewing's sarcoma were induced by intra-osseous injection of human TC-71 ES cells. OPG was administered in vivo by non-viral gene transfer using an amphiphilic non ionic block copolymer. ES bearing mice were assigned to controls (no treatment, synthetic vector alone or F68/empty pcDNA3.1 plasmid) and hOPG treated groups. A substantial but not significant inhibition of tumor development was observed in the hOPG group as compared to control groups. Marked bone lesions were revealed by micro-computed tomography analyses in control groups whereas a normal bone micro-architecture was preserved in the hOPG treated group. RANKL over-expressed in ES animal model was expressed by tumor cells rather than by host cells. However, TRAIL present in the tumor microenvironment may interfere with OPG effect on tumor development and bone remodeling via RANKL inhibition. In conclusion, the use of a xenogenic model of Ewing's sarcoma allowed discriminating between the tumor and host cells responsible for the elevation of RANKL production observed in this tumor and demonstrated the relevance of blocking RANKL by OPG as a promising therapy in ES.

99mTc-NTP 15-5 assessment of the early therapeutic response of chondrosarcoma to zoledronic acid in the Swarm rat orthotopic model

Background

Since proteoglycans (PGs) appear as key partners in chondrosarcoma biology, PG-targeted imaging using the radiotracer ^99mTc-N-(triethylammonium)-3-propyl-[15]ane-N5 (^99mTc-NTP 15-5) developed by our group was previously demonstrated to be a good single-photon emission computed tomography tracer for cartilage neoplasms. We therefore initiated this new preclinical study to evaluate the relevance of ^99mTc-NTP 15-5 imaging for the in vivo monitoring and quantitative assessment of chondrosarcoma response to zoledronic acid (ZOL) in the Swarm rat orthotopic model.

Findings

Rats bearing chondrosarcoma in the orthotopic paratibial location were treated by ZOL (100 μg/kg, subcutaneously) or phosphate-buffered saline, twice a week, from day 4 to day 48 post-tumor implantation. ^99mTc-NTP 15-5 imaging was performed at regular intervals with the target-to-background ratio (TBR) determined. Tumor volume was monitored using a calliper, and histology was performed at the end of the study. From day 11 to day 48, mean TBR values ranged from 1.7 ± 0.6 to 2.3 ± 0.6 in ZOL-treated rats and from 2.1 ± 1.0 to 4.9 ± 0.9 in controls. Tumor growth inhibition was evidenced using a calliper from day 24 and associated to a decrease in PG content in treated tumor tissues (confirmed by histology).

Conclusions

This work demonstrated two proofs of concept: (1) biphosphonate therapy could be a promising therapeutic approach for chondrosarcoma; (2) ^99mTc-NTP 15-5 is expected to offer a novel imaging modality for the in vivo evaluation of the extracellular matrix features of chondrosarcoma, which could be useful for the follow-up and quantitative assessment of proteoglycan ‘downregulation’ associated to the response to therapeutic attempts.

Distinctive tooth-extraction socket healing: bisphosphonate versus parathyroid hormone therapy

BACKGROUND

Patients with osteoporosis who receive tooth extractions are typically on either oral bisphosphonate or parathyroid hormone (PTH) therapy. Currently, the consequence of these therapies on hard- and soft-tissue healing in the oral cavity is not clearly defined. The aim of this study is to determine the differences in the therapeutic effect on tooth-extraction wound healing between bisphosphonate and PTH therapies.

METHODS

Maxillary second molars were extracted in Sprague Dawley rats (n = 30), and either bisphosphonate (zoledronate [Zol]), PTH, or saline (vehicle control [VC]) was administered for 10 days (n = 10 per group). Hard-tissue healing was evaluated by microcomputed tomography and histomorphometric analyses. Collagen, blood vessels, inflammatory cell infiltration, and cathepsin K expression were assessed in soft tissue using immunohistochemistry, quantitative polymerase chain reaction, and immunoblotting.

RESULTS

Both therapies significantly increased bone fill and suppressed vertical bone loss. However, considerably more devital bone was observed in the sockets of rats on Zol versus VC. Although Zol increased the numbers of blood vessels, the total blood vessel area in soft tissue was significantly smaller than in VC. PTH therapy increased osteoblastic bone formation and suppressed osteoclasts. PTH therapy promoted soft-tissue maturation by suppressing inflammation and stimulating collagen deposition.

CONCLUSION

Zoledronate therapy deters whereas PTH therapy promotes hard- and soft-tissue healing in the oral cavity, and both therapies prevent vertical bone loss.

Bone sarcomas: from biology to targeted therapies

Primary malignant bone tumours, osteosarcomas, and Ewing sarcomas are rare diseases which occur mainly in adolescents and young adults. With the current therapies, some patients remain very difficult to treat, such as tumour with poor histological response to preoperative CT (or large initial tumour volume for Ewing sarcomas not operated), patients with multiple metastases at or those who relapsed. In order to develop new therapies against these rare tumours, we need to unveil the key driving factors and molecular abnormalities behind the malignant characteristics and to broaden our understanding of the phenomena sustaining the metastatic phenotype and treatment resistance in these tumours. In this paper, starting with the biology of these tumours, we will discuss potential therapeutic targets aimed at increasing local tumour control, limiting metastatic spread, and finally improving patient survival.

The first European interdisciplinary ewing sarcoma research summit

The European Network for Cancer Research in Children and Adolescents (ENCCA) provides an interaction platform for stakeholders in research and care of children with cancer. Among ENCCA objectives is the establishment of biology-based prioritization mechanisms for the selection of innovative targets, drugs, and prognostic markers for validation in clinical trials. Specifically for sarcomas, there is a burning need for novel treatment options, since current chemotherapeutic treatment protocols have met their limits. This is most obvious for metastatic Ewing sarcoma (ES), where long term survival rates are still below 20%. Despite significant progress in our understanding of ES biology, clinical translation of promising laboratory results has not yet taken place due to fragmentation of research and lack of an institutionalized discussion forum. To fill this gap, ENCCA assembled 30 European expert scientists and five North American opinion leaders in December 2011 to exchange thoughts and discuss the state of the art in ES research and latest results from the bench, and to propose biological studies and novel promising therapeutics for the upcoming European EWING2008 and EWING2012 clinical trials.