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

The Bone Niche of Chondrosarcoma: A Sanctuary for Drug Resistance, Tumour Growth and also a Source of New Therapeutic Targets

Chondrosarcomas are malignant cartilage-forming tumours representing around 20% of malignant primary tumours of bone and affect mainly adults in the third to sixth decade of life. Unfortunately, the molecular pathways controlling the genesis and the growth of chondrosarcoma cells are still not fully defined. It is well admitted that the invasion of bone by tumour cells affects the balance between early bone resorption and formation and induces an “inflammatory-like” environment which establishes a dialogue between tumour cells and their environment. The bone tumour microenvironment is then described as a sanctuary that contributes to the drug resistance patterns and may control at least in part the tumour growth. The concept of “niche” defined as a specialized microenvironment that can promote the emergence of tumour stem cells and provide all the required factors for their development recently emerges in the literature. The present paper aims to summarize the main evidence sustaining the existence of a specific bone niche in the pathogenesis of chondrosarcomas

Tc-99m-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

Unstable Attractors: Existence and Robustness in Networks of Oscillators With Delayed Pulse Coupling

We consider unstable attractors; Milnor attractors $A$ such that, for some neighbourhood $U$ of $A$, almost all initial conditions leave $U$. Previous research strongly suggests that unstable attractors exist and even occur robustly (i.e. for open sets of parameter values) in a system modelling biological phenomena, namely in globally coupled oscillators with delayed pulse interactions. In the first part of this paper we give a rigorous definition of unstable attractors for general dynamical systems. We classify unstable attractors into two types, depending on whether or not there is a neighbourhood of the attractor that intersects the basin in a set of positive measure. We give examples of both types of unstable attractor; these examples have non-invertible dynamics that collapse certain open sets onto stable manifolds of saddle orbits. In the second part we give the first rigorous demonstration of existence and robust occurrence of unstable attractors in a network of oscillators with delayed pulse coupling. Although such systems are technically hybrid systems of delay differential equations with discontinuous `firing' events, we show that their dynamics reduces to a finite dimensional hybrid system system after a finite time and hence we can discuss Milnor attractors for this reduced finite dimensional system. We prove that for an open set of phase resetting functions there are saddle periodic orbits that are unstable attractors.Comment: 29 pages, 8 figures,submitted to Nonlinearit

Receptor activator of nuclear factor-kappa B ligand (RANKL) directly modulates the gene expression profile of RANK-positive Saos-2 human osteosarcoma cells

Receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) are the key regulators of bone metabolism. Recent findings demonstrated a crucial role of RANK in several bone-associated tumors. Indeed, we have recently demonstrated functional RANK expression both in a mouse and several human osteosarcoma cell lines. However, RANKL effects on osteosarcoma cells remain to be determined. In this study, we determined RANKL effects on RANK-positive Saos-2 human osteosarcoma cells. cDNA microarray and quantitative RT-PCR analyses clearly demonstrated that RANK-positive osteosarcoma cells were the target of RANKL as well as osteoclasts/osteoclast precursors. Thus, we present for the first time that RANKL can directly and significantly modulate gene expression of RANK-expressing Saos-2 cells. RANKL-modulated genes included genes that were implicated in protein metabolism, nucleic acid metabolism, intracellular transport, cytoskeleton organization and biogenesis, apoptosis and signaling cascade. Our results strengthen the involvement of the RANK/RANKL/OPG axis in osteosarcoma biology and capability to identify novel therapeutic approaches targeting RANK-positive osteosarcomas

Roles of inflammatory cell infiltrate in periprosthetic osteolysis

Classically, particle-induced periprosthetic osteolysis at the implant–bone interface has explained the aseptic loosening of joint replacement. This response is preceded by triggering both the innate and acquired immune response with subsequent activation of osteoclasts, the bone-resorbing cells. Although particle-induced periprosthetic osteolysis has been considered a foreign body chronic inflammation mediated by myelomonocytic-derived cells, current reports describe wide heterogeneous inflammatory cells infiltrating the periprosthetic tissues. This review aims to discuss the role of those non-myelomonocytic cells in periprosthetic tissues exposed to wear particles by showing original data. Specifically, we discuss the role of T cells (CD3+, CD4+, and CD8+) and B cells (CD20+) coexisting with CD68+/TRAP− multinucleated giant cells associated with both polyethylene and metallic particles infiltrating retrieved periprosthetic membranes. This review contributes valuable insight to support the complex cell and molecular mechanisms behind the aseptic loosening theories of orthopedic implants

IL-1 beta and TNF alpha Promote Monocyte Viability through the Induction of GM-CSF Expression by Rheumatoid Arthritis Synovial Fibroblasts

Background. Macrophages and synovial fibroblasts (SF) are two major cells implicated in the pathogenesis of rheumatoid arthritis (RA). SF could be a source of cytokines and growth factors driving macrophages survival and activation. Here, we studied the effect of SF on monocyte viability and phenotype. Methods. SF were isolated from synovial tissue of RA patients and CD14+ cells were isolated from peripheral blood of healthy donors. SF conditioned media were collected after 24 hours of culture with or without stimulation with TNFα or IL-1β. Macrophages polarisation was studied by flow cytometry. Results. Conditioned medium from SF significantly increased monocytes viability by 60% compared to CD14+ cells cultured in medium alone . This effect was enhanced using conditioned media from IL-1β and TNFα stimulated SF. GM-CSF but not M-CSF nor IL34 blocking antibodies was able to significantly decrease monocyte viability by 30% when added to the conditioned media from IL-1β and TNFα stimulated SF . Finally, monocyte cultured in presence of SF conditioned media did not exhibit a specific M1 or M2 phenotype. Conclusion. Overall, rheumatoid arthritis synovial fibroblasts stimulated with proinflammatory cytokines (IL-1β and TNFα) promote monocyte viability via GM-CSF but do not induce a specific macrophage polarization

Osteoprotegerin: multiple partners for multiple functions.

Osteoprotegerin (OPG) is an essential secreted protein in bone turnover due to its role as a decoy receptor for the Receptor Activator of Nuclear Factor-kB ligand (RANKL) in the osteoclasts, thus inhibiting their differentiation. However, there are additional ligands of OPG that confer various biological functions. OPG can promote cell survival, cell proliferation and facilitates migration by binding TNF-related apoptosis inducing ligand (TRAIL), glycosaminoglycans or proteoglycans. A large number of in vitro, pre-clinical and clinical studies provide evidences of OPG involvement in vascular, bone, immune and tumor biology. This review describes an overview of the different OPG ligands regulating its biological functions

L-MTP-PE and zoledronic acid combination in osteosarcoma: pre-clinical evidence of positive therapeutic combination for clinical transfer

Osteosarcoma, the most frequent malignant primary bone tumor in pediatric patients is characterized by osteolysis promoting tumor growth. Lung metastasis is the major bad prognosis factor of this disease. Zoledronic Acid (ZA), a potent inhibitor of bone resorption is currently evaluated in phase III randomized studies in Europe for the treatment of osteosarcoma and Ewing sarcoma. The beneicial effect of the liposomal form of Muramyl-TriPeptide-Phosphatidyl Ethanolamine (L-mifamurtide, MEPACT®), an activator of macrophage populations has been demonstrated to eradicate lung metastatic foci in osteosarcoma. The objective of this study was to evaluate the potential therapeutic beneit and the safety of the ZA and L-mifamurtide combination in preclinical models of osteosarcoma, as a prerequisite before translation to patients. The effects of ZA (100 µg/kg) and L-mifamurtide (1 mg/kg) were investigated in vivo in xenogeneic and syngeneic mice models of osteosarcoma, at clinical (tumor proliferation, spontaneous lung metastases development), radiological (bone microarchitecture by microCT analysis), biological and histological levels. No interference between the two drugs could be observed on ZA-induced bone protection and on L-mifamurtide-induced inhibition of lung metastasis development. Unexpectedly, ZA and L-mifamurtide association induced an additional and in some cases synergistic inhibition of primary tumor progression. L-mifamurtide has no effect on tumor proliferation in vitro or in vivo, and macrophage population was not affected at the tumor site whatever the treatment. This study evidenced for the irst time a signiicant inhibition of primary osteosarcoma progression when both drugs are combined. This result constitutes a irst proof-of-principle for clinical application in osteosarcoma patients