Targeted therapies for bone sarcomas

Exosomes in Bone Cancer: Unveiling their Vital Role in Diagnosis, Prognosis, and Therapeutic Advancements

Bone cancer among adolescents and children exhibits varying survival outcomes based on disease state. While localized bone cancer cases have a survival rate exceeding 70%, metastatic, refractory, and recurrent forms are associated with significantly poorer prognoses. Initially believed to be mere vehicles for cellular waste disposal, exosomes are now recognized as extracellular vesicles facilitating intercellular communication. These vesicles influence cellular behaviors by transporting various biomolecules, such as proteins, DNA, RNA, and lipids, among cells. The role of exosomes in regulating the progression of bone cancer is increasingly evident, impacting critical processes like tumorigenesis, proliferation, metastasis, angiogenesis, immune evasion, and drug resistance. Current research underscores the substantial potential of exosomes in promoting the progression and development of bone cancer. This review delves into the complex process of exosome biogenesis, the variety of cell-derived exosome sources, and their applications in drug delivery and therapeutics. It also examines ongoing clinical trials focused on exosome cargo levels and discusses the challenges and future directions in exosome research. Unlike costly and invasive traditional diagnostic methods, exosomal biomarkers offer a non-invasive, cost-effective, and readily accessible routine screening through simple fluid collection that aims to inspire researchers to investigate the potential of exosomes for cancer theragnostic. Through comprehensive exploration of these areas, the review seeks to enhance understanding and foster innovative solutions to cancer biology in the near future.

Glycan Structures in Osteosarcoma as Targets for Lectin-Based Chimeric Antigen Receptor Immunotherapy

Osteosarcoma is a type of bone cancer that primarily affects children and young adults. The overall 5-year survival rate for localized osteosarcoma is 70-75%, but it is only 20-30% for patients with relapsed or metastatic tumors. To investigate potential glycan-targeting structures for immunotherapy, we stained primary osteosarcomas with recombinant C-type lectin CD301 (MGL, CLEC10A) and observed moderate to strong staining on 26% of the tumors. NK92 cells expressing a CD301-CAR recognized and eliminated osteosarcoma cells in vitro. Cytotoxic activity assays correlated with degranulation and cytokine release assays. Combination with an inhibitory antibody against the immune checkpoint TIGIT (T-cell immunoreceptor with lg and ITIM domains) showed promising additional effects. Overall, this study showed, for the first time, the expression of CD301 ligands in osteosarcoma tissue and demonstrated their use as potential target structures for lectin-based immunotherapy.

Molecular mechanisms underpinning sarcomas and implications for current and future therapy

Sarcomas are complex mesenchymal neoplasms with a poor prognosis. Their clinical management is highly challenging due to their heterogeneity and insensitivity to current treatments. Although there have been advances in understanding specific genomic alterations and genetic mutations driving sarcomagenesis, the underlying molecular mechanisms, which are likely to be unique for each sarcoma subtype, are not fully understood. This is in part due to a lack of consensus on the cells of origin, but there is now mounting evidence that they originate from mesenchymal stromal/stem cells (MSCs). To identify novel treatment strategies for sarcomas, research in recent years has adopted a mechanism-based search for molecular markers for targeted therapy which has included recapitulating sarcomagenesis using in vitro and in vivo MSC models. This review provides a comprehensive up to date overview of the molecular mechanisms that underpin sarcomagenesis, the contribution of MSCs to modelling sarcomagenesis in vivo, as well as novel topics such as the role of epithelial-to-mesenchymal-transition (EMT)/mesenchymal-to-epithelial-transition (MET) plasticity, exosomes, and microRNAs in sarcomagenesis. It also reviews current therapeutic options including ongoing pre-clinical and clinical studies for targeted sarcoma therapy and discusses new therapeutic avenues such as targeting recently identified molecular pathways and key transcription factors.

Pictilisib Enhances the Antitumor Effect of Doxorubicin and Prevents Tumor-Mediated Bone Destruction by Blockade of PI3K/AKT Pathway

Despite advances in neoadjuvant chemotherapy, outcomes for patients with osteosarcoma resistant to first-line chemotherapy have been dismal for decades. There is thus an urgent need to develop novel targeted drugs to effectively treat refractory osteosarcoma. Dysregulation in the PI3K/AKT pathway has been observed during the development of osteosarcoma. Herein, we first evaluated p-AKT (Ser473) expression levels in osteosarcoma tissue using high-throughput tissue microarrays. Then, we demonstrated the role of pictilisib, a novel potent PI3K inhibitor, in osteosarcoma and related osteolysis. Functional studies of pictilisib in osteosarcoma cell lines and bone marrow-derived macrophages were performed in vitro. Patient-derived xenografts and orthotopic mouse models were used to assess the effects of pictilisib in vivo. The results showed that positive p-AKT expression levels after neoadjuvant chemotherapy were significantly associated with tumor cell necrosis rate. Pictilisib effectively inhibited the proliferation of osteosarcoma through G0/G1-S phase cell cycle arrest, and enhanced the sensitivity of osteosarcoma to doxorubicin, although it failed to induce cell apoptosis alone. In addition, pictilisib inhibited differentiation of osteoclasts and bone resorption in vitro and tumor-related osteolysis in vivo via inhibition of the PI3K/AKT/GSK3β and NF-κB pathways. Pictilisib combined with conventional chemotherapy drugs represents a potential treatment strategy to suppress tumor growth and bone destruction in p-AKT-positive patients.

Leucine and branched-chain amino acid metabolism contribute to the growth of bone sarcomas by regulating AMPK and mTORC1 signaling

Osteosarcoma and chondrosarcoma are sarcomas of the bone and the cartilage that are primarily treated by surgical intervention combined with high toxicity chemotherapy. In search of alternative metabolic approaches to address the challenges in treating bone sarcomas, we assessed the growth dependence of these cancers on leucine, one of the branched-chain amino acids (BCAAs), and BCAA metabolism. Tumor biopsies from bone sarcoma patients revealed differential expression of BCAA metabolic enzymes. The cytosolic branched-chain aminotransferase (BCATc) that is commonly overexpressed in cancer cells, was down-regulated in chondrosarcoma (SW1353) in contrast with osteosarcoma (143B) cells that expressed both BCATc and its mitochondrial isoform BCATm. Treating SW1353 cells with gabapentin, a selective inhibitor of BCATc, further revealed that these cells failed to respond to gabapentin. Application of the structural analog of leucine, N-acetyl-leucine amide (NALA) to disrupt leucine uptake, indicated that all bone sarcoma cells used leucine to support their energy metabolism and biosynthetic demands. This was evident from the increased activity of the energy sensor AMP-activated protein kinase (AMPK), down-regulation of complex 1 of the mammalian target of rapamycin (mTORC1), and reduced cell viability in response to NALA. The observed changes were most profound in the 143B cells, which appeared highly dependent on cytosolic and mitochondrial BCAA metabolism. This study thus demonstrates that bone sarcomas rely on leucine and BCAA metabolism for energy and growth; however, the differential expression of BCAA enzymes and the presence of other carbon sources may dictate how efficiently these cancer cells take advantage of BCAA metabolism.

New Chondrosarcoma Cell Lines with Preserved Stem Cell Properties to Study the Genomic Drift During In Vitro/In Vivo Growth

For the cancer genomics era, there is a need for clinically annotated close-to-patient cell lines suitable to investigate altered pathways and serve as high-throughput drug-screening platforms. This is particularly important for drug-resistant tumors like chondrosarcoma which has few models available. Here we established and characterized new cell lines derived from two secondary (CDS06 and CDS11) and one dedifferentiated (CDS-17) chondrosarcomas as well as another line derived from a CDS-17-generated xenograft (T-CDS17). These lines displayed cancer stem cell-related and invasive features and were able to initiate subcutaneous and/or orthotopic animal models. Different mutations in Isocitrate Dehydrogenase-1 (IDH1), Isocitrate Dehydrogenase-2 (IDH2), and Tumor Supressor P53 (TP53) and deletion of Cyclin Dependent Kinase Inhibitor 2A (CDKN2A) were detected both in cell lines and tumor samples. In addition, other mutations in TP53 and the amplification of Mouse Double Minute 2 homolog (MDM2) arose during cell culture in CDS17 cells. Whole exome sequencing analysis of CDS17, T-CDS17, and matched patient samples confirmed that cell lines kept the most relevant mutations of the tumor, uncovered new mutations and revealed structural variants that emerged during in vitro/in vivo growth. Altogether, this work expanded the panel of clinically and genetically-annotated chondrosarcoma lines amenable for in vivo studies and cancer stem cell (CSC) characterization. Moreover, it provided clues of the genetic drift of chondrosarcoma cells during the adaptation to grow conditions.

Long non-coding RNA EPIC1 inhibits viability and invasion of osteosarcoma cells by promoting MEF2D ubiquitylation

BACKGROUND

Long non-coding RNAs (lncRNAs) can modulate gene expression through different mechanisms, but the fundamental molecular mechanism behind EPIC1 and osteosarcoma (OS) was poorly understood.

METHODS

Bone tumor tissues and the matched normal tissues were obtained from 36 OS patients who received tumor resection from 2014 to 2018. The expression of EPIC1 and MEF2D was determined by quantitative real-Time PCR and western blotting. Cell viability and invasion were evaluated by MTT assay and transwell assay. The animal xenograft model was also established.

RESULTS

EPIC1 was down-regulated, but MEF2D was up-regulated in OS tissues and OS cell lines. Overexpression of EPIC1 inhibited cell viability and invasion of OS cells. Targeting relationship between EPIC1 and MEF2D was confirmed by RNA pull-down and RNA immunoprecipitation (RIP). The MEF2D protein binding to ubiquitin was significantly increased in OS cells overexpressing EPIC1. The co-transfection with pcDNA-EPIC1 and pcDNA-MEF2D rescued the inhibition of cell viability and invasion caused by the overexpression of EPIC1. Overexpression of EPIC1 suppressed tumor growth in the OS xenograft model.

CONCLUSION

Our findings indicated that overexpression of EPIC1 inhibited cell viability and invasion of OS cells by promoting MEF2D ubiquitylation, which provided innovative lncRNA and protein targets for treating OS.

Novel molecular insights and new therapeutic strategies in osteosarcoma

Osteosarcoma (OS) is one of the most prevalent malignant cancers with lower survival and poor overall prognosis mainly in children and adolescents. Identifying the molecular mechanisms and OS stem cells (OSCs) as new concepts involved in disease pathogenesis and progression may potentially lead to new therapeutic targets. Therefore, therapeutic targeting of OSCs can be one of the most important and effective strategies for the treatment of OS. This review describes the new molecular targets of OS as well as novel therapeutic approaches in the design of future investigations and treatment.

Chondrosarcoma: An overview of clinical behavior, molecular mechanisms mediated drug resistance and potential therapeutic targets

Sarcomas are known as a heterogeneous class of cancers arisen in the connective tissues and demonstrated various histological subtypes including both soft tissue and bone origin. Chondrosarcoma is one of the main types of bone sarcoma that shows a considerable deficiency in response to chemotherapy and radiotherapy. While conventional treatment based on surgery, chemo-and radiotherapy are used in this tumor, high rate of death especially among children and adolescents are reported. Due to high resistance to current conventional therapies in chondrosarcoma, there is an urgent requirement to recognize factors causing resistance and discover new strategies for optimal treatment. In the past decade, dysregulation of genes associated with tumor development and therapy resistance has been studied to find potential therapeutic targets to overcome resistance. In this review, clinical aspects of chondrosarcoma are summarized. Moreover, it gives a summary of gene dysregulation, mutation, histone modifications and non-coding RNAs associated with tumor development and therapeutic response modulation. Finally, the probable role of tumor microenvironment in chondrosarcoma drug resistance and targeted therapies as a promising molecular therapeutic approach are 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.

Integrated analysis of gene expression and copy number variations in MET proto‑oncogene‑transformed human primary osteoblasts

The aim of the present study was to screen the potential osteosarcoma (OS)‑associated genes and to obtain additional insight into the pathogenesis of OS. Transcriptional profile (ID: GSE28256) and copy number variations (CNV) profile were downloaded from Gene Expression Omnibus database. Differentially expressed genes (DEGs) between MET proto‑oncogene‑transformed human primary osteoblast (MET‑HOB) samples and the control samples were identified using the Linear Models for Microarray Data package. Subsequently, CNV areas and CNVs were identified using cut‑off criterion of >30%‑overlap within the cases using detect_cnv.pl in PennCNV. Genes shared in DEGs and CNVs were obtained and discussed. Additionally, the Database for Annotation, Visualization and Integrated Discovery was used to identify significant Gene Ontology (GO) functions and pathways in DEGs with P<0.05. A total of 1,601 DEGs were screened out in MET‑HOBs and compared with control samples, including 784 upregulated genes, such as E2F transcription factor 1 (E2F1) and 2 (E2F2) and 817 downregulated genes, such as retinoblastoma 1 (RB1) and cyclin D1 (CCND1). DEGs were enriched in 344 GO terms, such as extracellular region part and extracellular matrix and 14 pathways, including pathways in cancer and extracellular matrix‑receptor interaction. Additionally, 239 duplications and 439 deletions in 678 genes from 1,313 chromosome regions were detected. A total of 12 genes were identified to be CNV‑driven genes, including cadherin 18, laminin subunit α 1, spectrin β, erythrocytic, ciliary rootlet coiled‑coil, rootletin pseudogene 2, β‑1,4-N-acetyl-galactosaminyltransferase 1, G protein regulated inducer of neurite outgrowth 1, EH domain binding protein 1‑like 1, growth factor independent 1, cathepsin Z, WNK lysine deficient protein kinase 1, glutathione S‑transferase mu 2 and microsomal glutathione S‑transferase 1. Therefore, cell cycle‑associated genes including E2F1, E2F2, RB1 and CCND1, and cell adhesion‑associated genes, such as CDH18 and LAMA1 may be used as diagnosis and/or therapeutic markers for patients with OS.

Managing sarcoma: where have we come from and where are we going?

Sarcomas are a heterogeneous group of neoplasms of mesenchymal origin. Approximately 80% arise from soft tissue and 20% originate from bone. To date more than 100 sarcoma subtypes have been identified and they vary in molecular characteristics, pathology, clinical presentation and response to treatment. While sarcomas represent <1% of adult cancers, they account for approximately 21% of paediatric malignancies and thus pose some of the greatest risks of mortality and morbidity in children and young adults. Metastases occur in one-third of all patients and approximately 10-20% of sarcomas recur locally. Surgery in combination with preoperative and postoperative therapies is the primary treatment for localized sarcoma tumours and is the most promising curative possibility. Metastasized sarcomas, on the other hand, are treated primarily with single-agent or combination chemotherapy, but this rarely leads to a complete and robust response and often becomes a palliative form of treatment. The heterogeneity of sarcomas results in variable responses to current generalized treatment strategies. In light of this and the lack of curative strategies for metastatic and unresectable sarcomas, there is a need for novel subtype-specific treatment strategies. With the more recent understanding of the molecular mechanisms underlying the pathogenesis of some of these tumours, the treatment of sarcoma subtypes with targeted therapies is a rapidly evolving field. This review discusses the current management of sarcomas as well as promising new therapies that are currently underway in clinical trials.

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.

Description of the immune microenvironment of chondrosarcoma and contribution to progression

Chondrosarcoma (CHS) is a rare bone malignancy characterized by its resistance to conventional systemic and radiation therapies. Whether immunotherapy targeting immune checkpoints may be active in these tumors remains unknown. To explore the role of the immune system in this tumor, we analyzed the immune environment of chondrosarcomas both in human sample, and in a syngeneic rat model, and tested the contribution of T lymphocytes and macrophages in chondrosarcoma progression. Immunohistochemical stainings were performed on human chondrosarcoma samples and on Swarm rat chondrosarcoma (SRC) model. Selective immunodepletion assays were performed in SRC to evaluate immune population's involvement in tumor progression. In human and rat chondrosarcoma, immune infiltrates composed of lymphocytes and macrophages were identified in the peritumoral area. Immune infiltrates composition was found correlated with tumors characteristics and evolution (grade, invasiveness and size). In SRC, selective depletion of T lymphocytes resulted in an accelerated growth rates, whereas depletion of CD163⁺ macrophages slowed down tumor progression. Splenocytes isolated from CHS-bearing SRC showed a specific cytotoxicity directed against chondrosarcoma cells (27%), which significantly decreased in CD3-depleted SRC (11%). The immune environment contributes to CHS progression in both human and animal models, suggesting that immunomodulatory approaches could be tested in bone chondrosarcoma.

Dual modulation of MCL-1 and mTOR determines the response to sunitinib

Most patients who initially respond to treatment with the multi-tyrosine kinase inhibitor sunitinib eventually relapse. Therefore, developing a deeper understanding of the contribution of sunitinib's numerous targets to the clinical response or to resistance is crucial. Here, we have shown that cancer cells respond to clinically relevant doses of sunitinib by enhancing the stability of the antiapoptotic protein MCL-1 and inducing mTORC1 signaling, thus evoking little cytotoxicity. Inhibition of MCL-1 or mTORC1 signaling sensitized cells to clinically relevant doses of sunitinib in vitro and was synergistic with sunitinib in impairing tumor growth in vivo, indicating that these responses are triggered as prosurvival mechanisms that enable cells to tolerate the cytotoxic effects of sunitinib. Furthermore, higher doses of sunitinib were cytotoxic, triggered a decline in MCL-1 levels, and inhibited mTORC1 signaling. Mechanistically, we determined that sunitinib modulates MCL-1 stability by affecting its proteasomal degradation. Dual modulation of MCL-1 stability at different dose ranges of sunitinib was due to differential effects on ERK and GSK3β activity, and the latter also accounted for dual modulation of mTORC1 activity. Finally, comparison of patient samples prior to and following sunitinib treatment suggested that increases in MCL-1 levels and mTORC1 activity correlate with resistance to sunitinib in patients.

Review of Osteosarcoma and Current Management

Osteosarcoma is the most common primary malignancy of bone in children and young adults. This tumor has a very heterogeneous genetic profile and lacks any consistent unifying event that leads to the pathogenesis of osteosarcoma. In this review, some of the important genetic events involved in osteosarcoma will be highlighted. Additionally, the clinical diagnosis of osteosarcoma will be discussed, as well as contemporary chemotherapeutic and surgical management of this tumor. Finally, the review will discuss some of the novel approaches to treating this disease.

The role of pharmacogenetics in the treatment of osteosarcoma

In osteosarcoma, large variation is observed in the efficacy and toxicity of chemotherapeutic drugs among similarly treated patients. Treatment optimization using predictive factors or algorithms is of importance, because there has been a lack of improvement of treatment outcome and survival for decades. The outcome of cancer treatment is influenced by the genome, thus studying genetic variants involved in the efficacy and toxicity of the chemotherapeutic drugs used in the treatment of osteosarcoma could be an opportunity to optimize current treatments and improve our understanding of the individual's drug response in osteosarcoma patients. This review discusses the current insights in the pharmacogenetics of the treatment response of osteosarcoma patients regarding efficacy and toxicity, and implications for future research and treatment.

Osteosarcoma: Cells-of-Origin, Cancer Stem Cells, and Targeted Therapies

Osteosarcoma (OS) is the most common type of primary solid tumor that develops in bone. Although standard chemotherapy has significantly improved long-term survival over the past few decades, the outcome for those patients with metastatic or recurrent OS remains dismally poor and, therefore, novel agents and treatment regimens are urgently required. A hypothesis to explain the resistance of OS to chemotherapy is the existence of drug resistant CSCs with progenitor properties that are responsible of tumor relapses and metastasis. These subpopulations of CSCs commonly emerge during tumor evolution from the cell-of-origin, which are the normal cells that acquire the first cancer-promoting mutations to initiate tumor formation. In OS, several cell types along the osteogenic lineage have been proposed as cell-of-origin. Both the cell-of-origin and their derived CSC subpopulations are highly influenced by environmental and epigenetic factors and, therefore, targeting the OS-CSC environment and niche is the rationale for many recently postulated therapies. Likewise, some strategies for targeting CSC-associated signaling pathways have already been tested in both preclinical and clinical settings. This review recapitulates current OS cell-of-origin models, the properties of the OS-CSC and its niche, and potential new therapies able to target OS-CSCs.

The clinical pathological significance of Thy1 and CD49f expression in chondrosarcomas

OBJECTIVE

This study investigated the protein expression and clinicopathological significance of Thy1 and CD49f in chondrosarcomas.

METHODS

Thy1 and CD49f protein expression in 59 chondrosarcomas and 33 osteochondromas were measured by immunohistochemical staining.

RESULTS

The percentage of positive Thy1 and CD49f expression was significantly higher in patients with chondrosarcoma than in patients with osteochondroma (P<0.01). The percentage of positive Thy1 and CD49f expression was significantly lower in patients with histological grade I, Enneking stage I, AJCC stage I/II stage, non-metastatic and non-invasive chondrosarcoma than in patients with histological grade III, Enneking stage II+III, AJCC stage III/IV, metastatic and invasive chondrosarcoma (P<0.05 or P<0.01). Thy1 expression was positively correlated with CD49f expression in chondrosarcoma. Kaplan-Meier survival analysis showed that histological grade, AJCC stage, Enneking stage, metastasis, invasion, and Thy1 and CD49f expression significantly correlated with shorter mean survival time in chondrosarcoma patients (P<0.05 or P<0.01). Cox multivariate analysis showed that positive Thy1 and CD49f expression was an independent prognostic factor that negatively correlated with overall postoperative survival.

CONCLUSION

Positive Thy1 and CD49f expression is significantly associated with the progression and poor prognosis of chondrosarcoma.

MicroRNA-130a promotes the metastasis and epithelial-mesenchymal transition of osteosarcoma by targeting PTEN

MicroRNAs, which serve as post-transcriptional modulators of numerous genes, have been found to be important regulators during the pathogenesis of osteosarcoma. This study demonstrates for the first time that microRNA-130a (miR-130a) is significantly upregulated in osteosarcoma, and associated with the metastasis of osteosarcoma. Elevated level of miR-130a was closely correlated with poor clinical features and prognosis of osteosarcoma patients. In vitro assays revealed that miR-130a could potentiate the migration, invasion and the epithelial-mesenchymal transtion (EMT) of osteosarcoma cells. Moreover, phosphatase and tensin homolog (PTEN) was confirmed as not only a direct downstream target but also a functional mediator of miR-130a. MiR-130a exerted promoting effects on metastatic behavior and EMT of osteosarcoma cells through suppressing PTEN expression. Based on these findings, we conclude that miR-130a is a promising prognostic biomarker for osteosarcoma patients, and targeting miR-130a may be a potential treatment option for osteosarcoma patients with metastasis.

Chordoma: an update on the pathophysiology and molecular mechanisms

Chordoma is a rare low-grade primary malignant skeletal tumor, which is presumed to derive from notochord remnants. The pathogenesis of chordoma has not been fully elucidated. However, recent advances in the molecular biology studies have identified brachyury underlying the initiation and progression of chordoma cells. More efforts have been made on accumulating evidence of the notochordal origin of chordoma, discovering signaling pathways and identifying crucial targets in chordomagenesis. In this review, we summarize the most recent research findings and focus on the pathophysiology and molecular mechanisms of chordoma.

Blocking HSP90 Addiction Inhibits Tumor Cell Proliferation, Metastasis Development, and Synergistically Acts with Zoledronic Acid to Delay Osteosarcoma Progression

PURPOSE

Despite recent improvements in therapeutic management of osteosarcoma, ongoing challenges in improving the response to chemotherapy warrants the development of new strategies to improve overall patient survival. Among them, HSP90 is a molecular chaperone involved in the maturation and stability of various oncogenic proteins leading to tumor cells survival and disease progression. We assessed the antitumor properties of a synthetic HSP90 inhibitor, PF4942847, alone or in combination with zoledronic acid in osteosarcoma.

EXPERIMENTAL DESIGN

The effects of PF4942847 were evaluated on human osteosarcoma cells growth and apoptosis. Signaling pathways were analyzed by Western blotting. The consequence of HSP90 therapy combined or not with zoledronic acid was evaluated in mice bearing HOS-MNNG xenografts on tumor growth, associated bone lesions, and pulmonary metastasis. The effect of PF4942847 on osteoclastogenesis was assessed on human CD14(+) monocytes.

RESULTS

In osteosarcoma cell lines, PF4942847 inhibited cell growth in a dose-dependent manner (IC50 ±50 nmol/L) and induced apoptosis with an increase of sub-G1 fraction and cleaved PARP. These biologic events were accompanied by decreased expression of Akt, p-ERK, c-Met, and c-RAF1. When administered orally to mice bearing osteosarcoma tumors, PF4942847 significantly inhibited tumor growth by 80%, prolonged survival compared with controls, and inhibited pulmonary metastases by blocking c-Met, FAK, and MMP9 signaling. In contrast to 17-allylamino-17-demethoxygeldanamycin (17-AAG), PF4942847 did not induce osteoclast differentiation, and synergistically acted with zoledronic acid to delay osteosarcoma progression and prevent bone lesions.

CONCLUSIONS

All these data provide a strong rationale for clinical evaluation of PF4942847 alone or in combination with zoledronic acid in osteosarcoma. Clin Cancer Res; 22(10); 2520-33. ©2015 AACR.

Advances in emerging drugs for osteosarcoma

INTRODUCTION

Osteosarcoma (OS), the most common primary malignant bone tumor, is currently treated with pre- and postoperative chemotherapy in association with the surgical removal of the tumor. Conventional treatments allow to cure about 60 - 65% of patients with primary tumors and only 20 - 25% of patients with recurrent disease. New treatment approaches and drugs are therefore highly warranted to improve prognosis.

AREAS COVERED

This review focuses on the therapeutic approaches that are under development or clinical evaluation in OS. Information was obtained from different and continuously updated data bases, as well as from literature searches, in which particular relevance was given to reports and reviews on new targeted therapies under clinical investigation in high-grade OS.

EXPERT OPINION

OS is a heterogeneous tumor, with a great variability in treatment response between patients. It is therefore unlikely that a single therapeutic tool will be uniformly successful for all OS patients. This claims for the validation of new treatment approaches together with biologic/(pharmaco)genetic markers, which may select the most appropriate subgroup of patients for each treatment approach. Since some promising novel agents and treatment strategies are currently tested in Phase I/II/III clinical trials, we may hope that new therapies with superior efficacy and safety profiles will be identified in the next few years.

Therapeutic effect of lymphokine-activated killer cells treated with low-dose ionizing radiation on osteosarcoma

The aim of the present study was to investigate the effect of lymphokine-activated killer (LAK) cells, which received low-dose ionizing radiation, on the treatment of osteosarcoma in rats. The cultured UMR-106 cells were inoculated under the anterior chest skin of 24 rats to establish an osteosarcoma model. In addition, the LAK cells from 24 mice were exposed to doses of 0 (control group), 0.65 or 3.25 mGy X-ray radiation. The tritiated thymidine (³H-TdR) release method and Winn assay were performed to determine the antitumor effects of the LAK cells. The proliferation of the mouse LAK cells treated with 3.25 mGy radiation was significantly higher than that for those treated with 0 or 0.65 mGy radiation, which suggested that low-dose ionizing radiation stimulates the proliferation of LAK cells. The tumor-bearing rats were divided into three groups and injected with LAK cells that had already received 0, 0.65 or 3.25 mGy radiation. The mean survival time of the 3.25-mGy group was longer than that of the 0- and 0.65-mGy groups. After 30 days, tumors with weights of ~6.25 and 2.0 g were identified in the rats of the 0- and 0.65-mGy groups, respectively. However, tumor proliferation was not detectable in the rats of the 3.25-mGy radiation group. Therefore, low-dose ionizing radiation effectively kills osteosarcoma cells in rats by stimulating the proliferation and enhancing the cytotoxicity of LAK cells.

MEF2D overexpression contributes to the progression of osteosarcoma

The underlying molecular pathogenesis of osteosarcoma remains poorly understood. The transcription factor MEF2D promotes the survival of various types of cells and functions as an oncogene in liver cancer. However, its potential contribution to osteosarcoma has not been explored. In this study, we investigated MEF2D expression and function in osteosarcoma, finding that MEF2D elevation in osteosarcoma clinical specimens was associated with patients' poor prognosis. MEF2D suppression was shown to decrease the proliferation of osteosarcoma cells, while forced expression of MEF2D was able to promote the proliferation of normal bone fibroblast. Notably, MEF2D silencing abolished osteosarcoma tumorigenicity in an animal model. Mechanistic investigations revealed that MEF2D silencing triggered G2-M arrest in osteosarcoma cells by suppressing RPRM and CDKN1A. miR-144 was found to suppress the expression of MEF2D in osteosarcoma cells. Collectively, our results demonstrated that MEF2D is a candidate oncogene for osteosarcoma and a potential molecular target for cancer therapy.

Receptor tyrosine kinases: Characterisation, mechanism of action and therapeutic interests for bone cancers

Bone cancers are characterised by the development of tumour cells in bone sites, associated with a dysregulation of their environment. In the last two decades, numerous therapeutic strategies have been developed to target the cancer cells or tumour niche. As the crosstalk between these two entities is tightly controlled by the release of polypeptide mediators activating signalling pathways through several receptor tyrosine kinases (RTKs), RTK inhibitors have been designed. These inhibitors have shown exciting clinical impacts, such as imatinib mesylate, which has become a reference treatment for chronic myeloid leukaemia and gastrointestinal tumours. The present review gives an overview of the main molecular and functional characteristics of RTKs, and focuses on the clinical applications that are envisaged and already assessed for the treatment of bone sarcomas and bone metastases.

Delivery of inhibitor of growth 4 (ING4) gene significantly inhibits proliferation and invasion and promotes apoptosis of human osteosarcoma cells

Growing evidence has suggested that inhibitor of growth 4 (ING4), a novel member of ING family proteins, plays a critical role in the development and progression of different tumors via multiple pathways. However, the function of ING4 in human osteosarcoma remains unclear. To understand its potential roles and mechanisms in inhibiting osteosarcoma, we constructed an expression vector pEGFP-ING4 and transfected the human osteosarcoma cells using this vector. We then studied the effects of over-expressed ING4 in the transfected cells on the proliferation, apoptosis and invasion of the osteosarcoma cells. The up-regulation of ING4 in the osteosarcoma cells, arising from the stable pEGFP-ING4 gene transfection, was found to significantly inhibit the cell proliferation by the cell cycle alteration with S phase reduction and G0/G1 phase arrest, induce cell apoptosis via the activation of the mitochondria pathway, and suppress cell invasion through the down-regulation of the matrix metalloproteinase 2 (MMP-2) and MMP-9 expression. In addition, increased ING4 level evoked the blockade of NF-κB signaling pathway and down-regulation of its target proteins. Our work suggests that ING4 can suppress osteosarcoma progression through signaling pathways such as mitochondria pathway and NF-κB signaling pathway and ING4 gene therapy is a promising approach to treating osteosarcoma.

The clinical pathological significance of FRAT1 and ROR2 expression in cartilage tumors

PURPOSE

Chondrosarcoma is a malignant bone tumor with poor prognosis. Surgical treatment is the first choice for chondrosarcomas. Chondrosarcoma is not sensitive to chemotherapy and radiotherapy. Identification of biological markers is important for the early diagnosis and targeted treatment of chondrosarcoma. This study investigated the protein expression and clinicopathological significance of ROR2 and FRAT1 in 59 chondrosarcomas and 33 osteochondromas.

METHODS

ROR2 and FRAT1 protein expression in tissues was measured by immunohistochemistry.

RESULTS

The percentage of positive ROR2 and FRAT1 expression was significantly higher in patients with chondrosarcoma than in patients with osteochondroma (P < 0.01). The percentage of positive ROR2 and FRAT1 expression was significantly lower in patients with histological grade I, AJCC stage I/II stage, Enneking stage I, non-metastatic and invasive chondrosarcoma than patients with histological grade III, AJCC stage III/IV, Enneking stage II + III, metastatic and invasive chondrosarcoma (P < 0.05 or P < 0.01). ROR2 expression was positively correlated with FRAT1 expression in chondrosarcoma. Kaplan-Meier survival analysis demonstrated that histological grade, AJCC stage, Enneking stage, metastasis, invasion, and ROR2 and FRAT1 expression significantly correlated with a short mean survival time of patients with chondrosarcoma (P < 0.05 or P < 0.01). Cox multivariate analysis showed that positive ROR2 and FRAT1 expression was an independent prognostic factor that negatively correlated with postoperative survival and positively correlated with mortality.

CONCLUSION

Positive ROR2 and FRAT1 expression is associated with the progression and poor prognosis of chondrosarcoma.