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

Advances in amelioration of plasma electrolytic oxidation coatings on biodegradable magnesium and alloys

Magnesium and its alloys are considered excellent materials for biodegradable implants because of their good biocompatibility and biodegradability as well as their mechanical properties. However, the rapid degradation rate severely limits their clinical applications. Plasma electrolytic oxidation (PEO), also known as micro-arc oxidation (MAO), is an effective surface modification technique. However, there are many pores and cracks on the coating surface under conventional PEO process. The corrosive products tend to penetrate deeply into the substrate, reducing its corrosion resistance and the biocompatibility, which makes PEO-coated Mg difficult to meet the long-term needs of in vivo implants. Hence, it is necessary to modify the PEO coating. This review discusses the formation mechanism and the influential parameters of PEO coatings on Mg. This is followed by a review of the latest research of the pretreatment and typical amelioration of PEO coating on biodegradable Mg alloys in the past 5 years, including calcium phosphate (Ca-P) coating, layered double hydroxide (LDH)-PEO coating, ZrO2 incorporated-PEO coating, antibacterial ingredients-PEO coating, drug-PEO coating, polymer-PEO composite coating, Plasma electrolytic fluorination (PEF) coating and self-healing coating. Meanwhile, the improvements of morphology, corrosion resistance, wear resistance, biocompatibility, antibacterial abilities, and drug loading abilities and the preparation methods of the modified PEO coatings are deeply discussed as well. Finally, the challenges and prospects of PEO coatings are discussed in detail for the purpose of promoting the clinical application of biodegradable Mg alloys.

Polymeric Nanoformulation of Zoledronic Acid Rescues Osteoblasts from the Harmful Effect of its Native Form: An In Vitro Investigation of Cytotoxic Potential on Osteoblasts and Osteosarcoma Cells

Osteosarcoma (OS) is a malignant tumor, fatal for pediatric patients who do not respond to chemotherapy, alternative therapies and drugs can provide better outcomes. Zoledronic acid (Zol) belonging to the class of bisphosphonates (BPs) has a direct antitumor ability to prevent Ras GTPases modification and stimulate apoptosis. Despite advances in maintaining balance in skeletal events and direct anticancer properties, Zol causes cytotoxicity to normal healthy pre-osteoblast cells, hampering mineralization and differentiation. The study reports the preparation and evaluation of a nanoformulation that can diminish the existing drawbacks of native Zol. The cytotoxic effect is evaluated on bone cancer cells and healthy bone cells with three different cell lines namely, K7M2 (mouse OS cell line), SaOS2 (human OS cell line), and MC3T3E1 (healthy cell counterpart). It is observed that Zol nanoformulation is uptaken more (95%) in K7M2 whereas in MC3T3E1, the percent population internalizing nanoparticles (NPs) is 45%. Zol has a sustained release of 15% after 96 h from the NP which leads to a rescuing effect on the normal pre-osteoblast cells. In conclusion, it can be stated that Zol nanoformulation can be used as a good platform for a sustained release system with minimum side effects to normal bone cells.

Transcriptional profiling of canine osteosarcoma identifies prognostic gene expression signatures with translational value for humans

Canine osteosarcoma is increasingly recognized as an informative model for human osteosarcoma. Here we show in one of the largest clinically annotated canine osteosarcoma transcriptional datasets that two previously reported, as well as de novo gene signatures devised through single sample Gene Set Enrichment Analysis (ssGSEA), have prognostic utility in both human and canine patients. Shared molecular pathway alterations are seen in immune cell signaling and activation including TH1 and TH2 signaling, interferon signaling, and inflammatory responses. Virtual cell sorting to estimate immune cell populations within canine and human tumors showed similar trends, predominantly for macrophages and CD8+ T cells. Immunohistochemical staining verified the increased presence of immune cells in tumors exhibiting immune gene enrichment. Collectively these findings further validate naturally occurring osteosarcoma of the pet dog as a translationally relevant patient model for humans and improve our understanding of the immunologic and genomic landscape of the disease in both species.

Analysis of intercellular communication in the osteosarcoma microenvironment based on single cell sequencing data

Osteosarcoma (OS) is the most common primary bone cancer in children and young adults, patient survival rates have not improved in recent decades. To further understand the interrelationship between different cell types in the tumor microenvironment of osteosarcoma, we comprehensively analyzed single-cell sequencing data from six patients with untreated osteosarcoma. Nine major cell types were identified from a total of 46,046 cells based on unbiased clustering of gene expression profiles and canonical markers. Osteosarcoma from different patients display heterogeneity in cellular composition. Myeloid cells were the most commonly represented cell type, followed by osteoblastic and TILs. Copy number variation (CNV) results identified amplifications and deletions in malignant osteoblastic cells and fibroblasts. Trajectory analysis based on RNA velocity showed that osteoclasts in the OS microenvironment could be differentiated from myeloid cells. Furthermore, we explored the intercellular communications in OS microenvironment and identified multiple ligand-receptor pairs between myeloid cells, osteoblastic cells and their cells, including 21 ligand-receptor pair genes that significantly associated with survival outcomes. Importantly, we found chemotherapy may have an effect on cellular communication in the OS microenvironment by analyzing single-cell sequencing data from seven primary osteosarcoma patients who received chemotherapy. We believe these observations will improve our understanding of potential mechanisms of microenvironment contributions to OS progression and help identify potential targets for new treatment development in the future.

Targeting strategies for bone diseases: signaling pathways and clinical studies

Since the proposal of Paul Ehrlich's magic bullet concept over 100 years ago, tremendous advances have occurred in targeted therapy. From the initial selective antibody, antitoxin to targeted drug delivery that emerged in the past decades, more precise therapeutic efficacy is realized in specific pathological sites of clinical diseases. As a highly pyknotic mineralized tissue with lessened blood flow, bone is characterized by a complex remodeling and homeostatic regulation mechanism, which makes drug therapy for skeletal diseases more challenging than other tissues. Bone-targeted therapy has been considered a promising therapeutic approach for handling such drawbacks. With the deepening understanding of bone biology, improvements in some established bone-targeted drugs and novel therapeutic targets for drugs and deliveries have emerged on the horizon. In this review, we provide a panoramic summary of recent advances in therapeutic strategies based on bone targeting. We highlight targeting strategies based on bone structure and remodeling biology. For bone-targeted therapeutic agents, in addition to improvements of the classic denosumab, romosozumab, and PTH1R ligands, potential regulation of the remodeling process targeting other key membrane expressions, cellular crosstalk, and gene expression, of all bone cells has been exploited. For bone-targeted drug delivery, different delivery strategies targeting bone matrix, bone marrow, and specific bone cells are summarized with a comparison between different targeting ligands. Ultimately, this review will summarize recent advances in the clinical translation of bone-targeted therapies and provide a perspective on the challenges for the application of bone-targeted therapy in the clinic and future trends in this area.

Osteoid cell-derived chemokines drive bone-metastatic prostate cancer

One of the greatest challenges in improving prostate cancer (PCa) survival is in designing new therapies to effectively target bone metastases. PCa regulation of the bone environment has been well characterized; however, bone-targeted therapies have little impact on patient survival, demonstrating a need for understanding the complexities of the tumor-bone environment. Many factors contribute to creating a favorable microenvironment for prostate tumors in bone, including cell signaling proteins produced by osteoid cells. Specifically, there has been extensive evidence from both past and recent studies that emphasize the importance of chemokine signaling in promoting PCa progression in the bone environment. Chemokine-focused strategies present promising therapeutic options for treating bone metastasis. These signaling pathways are complex, with many being produced by (and exerting effects on) a plethora of different cell types, including stromal and tumor cells of the prostate tumor-bone microenvironment. ​This review highlights an underappreciated molecular family that should be interrogated for treatment of bone metastatic prostate cancer (BM-PCa).

The interaction between osteosarcoma and other cells in the bone microenvironment: From mechanism to clinical applications

Osteosarcoma is a primary bone tumor with a high mortality rate. The event-free survival rate has not improved significantly in the past 30 years, which brings a heavy burden to patients and society. The high heterogeneity of osteosarcoma leads to the lack of specific targets and poor therapeutic effect. Tumor microenvironment is the focus of current research, and osteosarcoma is closely related to bone microenvironment. Many soluble factors and extracellular matrix secreted by many cells in the bone microenvironment have been shown to affect the occurrence, proliferation, invasion and metastasis of osteosarcoma through a variety of signaling pathways. Therefore, targeting other cells in the bone microenvironment may improve the prognosis of osteosarcoma. The mechanism by which osteosarcoma interacts with other cells in the bone microenvironment has been extensively investigated, but currently developed drugs targeting the bone microenvironment have poor efficacy. Therefore, we review the regulatory effects of major cells and physical and chemical properties in the bone microenvironment on osteosarcoma, focusing on their complex interactions, potential therapeutic strategies and clinical applications, to deepen our understanding of osteosarcoma and the bone microenvironment and provide reference for future treatment. Targeting other cells in the bone microenvironment may provide potential targets for the development of clinical drugs for osteosarcoma and may improve the prognosis of osteosarcoma.

Engineering Novel 3D Models to Recreate High-Grade Osteosarcoma and its Immune and Extracellular Matrix Microenvironment

Osteosarcoma (OS) is the most common primary bone cancer, where the overall 5-year surviving rate is below 20% in resistant forms. Accelerating cures for those poor outcome patients remains a challenge. Nevertheless, several studies of agents targeting abnormal cancerous pathways have yielded disappointing results when translated into clinic because of the lack of accurate OS preclinical modeling. So, any effort to design preclinical drug testing may consider all inter-, intra-, and extra-tumoral heterogeneities throughout models mimicking extracellular and immune microenvironment. Therefore, the bioengineering of patient-derived models reproducing the OS heterogeneity, the interaction with tumor-associated macrophages (TAMs), and the modulation of oxygen concentrations additionally to recreation of bone scaffold is proposed here. Eight 2D preclinical models mimicking several OS clinical situations and their TAMs in hypoxic conditions are developed first and, subsequently, the paired 3D models faithfully preserving histological and biological characteristics are generated. It is possible to shape reproducibly M2-like macrophages cultured with all OS patient-derived cell lines in both dimensions. The final 3D models pooling all heterogeneity features are providing accurate proliferation and migration data to understand the mechanisms involved in OS and immune cells/biomatrix interactions and sustained such that engineered 3D preclinical systems will improve personalized medicine.

Origin and Therapies of Osteosarcoma

Simple Summary

Osteosarcoma is the most common malignant bone tumor in children, with a 5-year survival rate ranging from 70% to 20% depending on the aggressiveness of the disease. The current treatments have not evolved over the past four decades due in part to the genetic complexity of the disease and its heterogeneity. This review will summarize the current knowledge of OS origin, diagnosis and therapies.

Abstract

Osteosarcoma (OS) is the most frequent primary bone tumor, mainly affecting children and young adults. Despite therapeutic advances, the 5-year survival rate is 70% but drastically decreases to 20–30% for poor responders to therapies or for patients with metastasis. No real evolution of the survival rates has been observed for four decades, explained by poor knowledge of the origin, difficulties related to diagnosis and the lack of targeted therapies for this pediatric tumor. This review will describe a non-exhaustive overview of osteosarcoma disease from a clinical and biological point of view, describing the origin, diagnosis and therapies.

PDCD10 promotes proliferation, migration, and invasion of osteosarcoma by inhibiting apoptosis and activating EMT pathway

BACKGROUND

Osteosarcoma, a common primary malignant tumor, occurs in children and adolescents with a poor prognosis. The current treatment methods are various, while the five-year survival rate of patients has not been significantly improved. As a member of the programmed death factor (PDCD) family, programmed death factor 10 (PDCD10) plays a role in regulating cell apoptosis. Several studies of PDCD10 in CCM and cancers have been reported before. However, there are no relevant research reports on the effects of PDCD10 on osteosarcoma.

METHODS

We used bioinformatics analysis, IHC, and clinical data to confirm the expression of PDCD10 and its correlation with prognosis in osteosarcoma. Then, we used shRNAs and cDNA to knock down or overexpress PDCD10 in U2OS and MG63 cell lines. A series of function assays such as CCK8, Wound healing test, Plate cloning formation assay, and Transwell were done to confirm how PDCD10 affects osteosarcoma. Animal assays were done to confirm the conclusions in cell lines. At last, WB was used to measure the protein expression levels of apoptosis and the EMT pathway.

RESULTS

PDCD10 was highly expressed in patients with osteosarcoma and correlated with prognosis; PDCD10 knockdown inhibited osteosarcoma growth, proliferation, migration, and invasion; PDCD10 overexpression promoted osteosarcoma growth, proliferation, migration, and invasion. In vivo experiments confirmed the conclusions in cell lines; PDCD10 inhibited apoptosis and activated the EMT pathway.

CONCLUSIONS

In this study, it was found that PDCD10 was highly expressed in patients with osteosarcoma, and it was closely related to patient prognosis. PDCD10 inhibited tumor cell apoptosis and promoted tumor progression by activating the EMT pathway. These findings may provide a potential target for gene therapy of osteosarcoma.

Identification of Small-Molecule Inhibitors for Osteosarcoma Targeted Therapy: Synchronizing In Silico, In Vitro, and In Vivo Analyses

Objective: The study aimed to explore a new approach for the treatment of osteosarcoma through combining biomaterials with next-generation small molecule–based targeted therapy.

Methods: The model of osteosarcoma was established by 4-hydroxyaminoquinoline 1-oxide (4-HAQO) in mice while the collagen-thermosensitive hydrogel–calcium phosphate (CTC) biocomposites were prepared, and the small molecule inhibitors were virtually screened and synthesized. Then, for the osteosarcoma cell line, MG-63 cells were used to validate our bioinformatic findings in vitro, and the mouse osteosarcoma models were treated by combing CTC composites and small-molecule inhibitors after debridement.

Results: Five compounds, namely, ZINC150338698, ZINC14768621, ZINC4217203, ZINC169291448, and ZINC85537017, were found in the ZINK database. Finally, ZINC150338698 was selected for chemical synthesis and experimental verification. The results of the MTT assay and Hoechst staining showed that the small-molecule inhibitor ZINC150338698 could significantly induce MG-63 cell death. Furthermore, CTC composites and ZINC150338698 could repair the bone defects well after the debridement of osteosarcoma. In addition, the biomaterials and small-molecule inhibitors have good biocompatibility and biosafety.

Conclusion: Our findings not only offer systems biology approach-based drug target identification but also provide new clues for developing novel treatment methods for future osteosarcoma research.

Single-cell RNA-seq identification of four differentially expressed survival-related genes by a TARGET: Osteosarcoma database analysis

Osteosarcoma (OS) differentially expressed genes (DEGs) have been predicted using the data portal of the Therapeutically Applicable Research to Generate Effective Treatments (TARGET). In this study, we sought to identify cell types that specially express key DEGs (MUC1, COL13A1, JAG2, and KAZALD1) in each of the nine identified cell populations derived from tissues of OS tumors with single-cell RNA-sequencing data. Gene expression levels were pairwise compared between cell clusters and a p value < 0.05 was considered differentially expressed. It was revealed that MUC1 is expressed at high levels in osteoblastic OS cells followed by carcinoma-associated fibroblasts (CAFs) and plasmocytes, respectively. COL13A1 is highly expressed in osteoblastic OS cells, CAFs, and endothelial cells (ECs), respectively. The KAZALD1 gene is expressed in CAFs and osteoblastic OS cells at high levels, but at very low levels in plasmocytes, osteoclasts, NK/T, myeloid cells 1, myeloid cells 2, ECs, and B cells. JAG2 is expressed at significantly high levels in ECs and osteoblastic OS cells, and at relatively lower levels in all other cell types. Interestingly, LSAMP, as an established gene in the development of OS shows high expression in osteoblastic OS cells and CAFs but low in other cells such as osteoclasts. Our findings here highlight the heterogeneity of OS cells and cell-type-dependent DEGs which have potential as therapeutic targets in OS.

Therapeutic Effects of Zoledronic Acid-Loaded Hyaluronic Acid/Polyethylene Glycol/Nano-Hydroxyapatite Nanoparticles on Osteosarcoma

Zoledronic acid (ZOL) has been approved as the only bisphosphonate for the prevention and treatment of metastatic bone diseases with acceptable safety and tolerability. However, systemic or direct injection of ZOL often causes severe side effects, which limits its clinical application. Here, an innovative nano-drug delivery system, ZOL-loaded hyaluronic acid/polyethylene glycol/nano-hydroxyapatite nanoparticles (HA-PEG-nHA-ZOL NPs), has been found to effectively inhibit the proliferation of three types of human osteosarcoma cell lines (143b, HOS, and MG63) at 1–10 μmol/L, while with low cell cytotoxicity on normal cells. The NPs significantly enhanced the apoptosis-related protein expression and tumor cell apoptosis rate. The NPs could also inhibit the proliferation of osteosarcoma cells by blocking the S phase of the cell cycle. In the orthotopic osteosarcoma nude mice model, local injection of the HA-PEG-nHA-ZOL NPs stimulated tumor necrosis, apoptosis, and granulocyte infiltration in the blood vessels. Altogether, the ZOL nano-delivery system possesses great potential for local treatment to prevent local tumor recurrence and can be applied in clinical osteosarcoma therapy.

Osteoclasts differential-related prognostic biomarker for osteosarcoma based on single cell, bulk cell and gene expression datasets

Osteosarcoma (OS) is one of the most common primary bone malignant tumors. Osteoclasts have been shown to have a valuable role in OS. In the present study, we analyzed the differentiation states of osteoclasts in OS and their prognostic significance based on integrated scRNA-seq and bulk RNA-seq data. Osteoclasts in distinct differentiation states were characterized, and 661 osteoclasts differentiation-related genes (ODRGs) were obtained. ORDGs in distinct differentiation states were enriched in distinct functions and pathways. TPM1, S100A13, LOXL1, PSMD10, ST3GAL4, PEF1, SERPINE2, TUBB, FAM207A, TUBA1A, and DCN were identified as the significant survival-predicting ODRGs. We successfully developed a risk score model based on these survival-predicting ODRGs. In addition, we generated a nomogram applicable for clinical with both ODRGs signatures and clinicopathological parameters, and validated in OS cohorts to predict OS patient outcome. This study proposed and verified the important roles of osteoclasts differentiation in the prognosis of patients with OS, suggesting promising therapeutic targets for OS.

Neurophysiological mechanisms of cancer-induced bone pain

Background

Cancer-induced Bone Pain (CIBP) is an important factor affecting their quality of life of cancer survivors. In addition, current clinical practice and scientific research suggest that neuropathic pain is a representative component of CIBP. However, given the variability of cancer conditions and the complexity of neuropathic pain, related mechanisms have been continuously supplemented but have not been perfected.

Aim of Review

Therefore, the current review highlights the latest progress in basic research on the field and proposes potential therapeutic targets, representative drugs and upcoming therapies.

Key Scientific Concepts of Review

Notably, factors such as central sensitization, neuroinflammation, glial cell activation and an acidic environment are considered to be related to neuropathic pain in CIBP. Nonetheless, further research is needed to ascertain the mechanism of CIBP in order to develop highly effective drugs. Moreover, more attention needs to be paid to the care of patients with advanced cancer.

Expression of immune-related genes as prognostic biomarkers for the assessment of osteosarcoma clinical outcomes

Cancer immunotherapy is a promising therapeutic approach, but the prognostic value of immune-related genes in osteosarcoma (OS) is unknown. Here, Target-OS RNA-seq data were analyzed to detect differentially expressed genes (DEGs) between OS subgroups, followed by functional enrichment analysis. Cox proportional risk regression was performed for each immune-related gene, and a risk score model to predict the prognosis of patients with OS was constructed. The risk scores were calculated using the risk signature to divide the training set into high-risk and low-risk groups, and validation was performed with GSE21257. We identified two immune-associated clusters, C1 and C2. C1 was closely related to immunity, and the immune score was significantly higher in C1 than in C2. Furthermore, we validated 6 immune cell hub genes related to the prognosis of OS: CD8A, KIR2DL1, CD79A, APBB1IP, GAL, and PLD3. Survival analysis revealed that the prognosis of the high-risk group was significantly worse than that of the low-risk group. We also explored whether the 6-gene prognostic risk model was effective for survival prediction. In conclusion, the constructed a risk score model based on immune-related genes and the survival of patients with OS could be a potential tool for targeted therapy.

Osteosarcoma mechanobiology and therapeutic targets

Osteosarcoma (OS) is the one of the most common primary tumors of bone with less than a 20% 5-year survival rate after the development of metastases. OS is highly predisposed in Paget's disease (PD) of bone, and both have common characteristic skeletal features due to rapid bone remodeling. OS prognosis is location dependent which further emphasizes the likely contribution of the bone microenvironment in its pathogenesis. Mechanobiology is the phenomenon when mechanical cues from the changing physical microenvironment of bone are transduced to biological pathways through mechanosensitive cellular components. Mechanobiology-driven therapies have been used for curbing tumor progression by direct alteration of the physical microenvironment or inhibition of metastasis-associated mechanosensitive proteins. This review emphasizes the contribution of mechanobiology to OS progression, and sheds light on current mechanobiology-based therapies and potential new targets for improving disease management. Additionally, the variety of 3D models currently used to study OS mechanobiology are summarized.

CoCrMo-Nanoparticles induced peri-implant osteolysis by promoting osteoblast ferroptosis via regulating Nrf2-ARE signalling pathway

Objectives

Aseptic loosening (AL) is the most common reason of total hip arthroplasty (THA) failure and revision surgery. Osteolysis, caused by wear particles released from implant surfaces, has a vital role in AL. Although previous studies suggest that wear particles always lead to osteoblast programmed death in the process of AL, the specific mechanism remains incompletely understood and osteoblast ferroptosis maybe a new mechanism of AL.

Materials and Methods

CoCrMo nanoparticles (CoNPs) were prepared to investigate the influence of ferroptosis in osteoblasts and calvaria resorption animal models. Periprosthetic osteolytic bone tissue was collected from patients who underwent AL after THA to verify osteoblast ferroptosis.

Results

Our study demonstrated that CoNPs induced significant ferroptosis in osteoblasts and particles induced osteolysis (PIO) animal models. Blocking ferroptosis with specific inhibitor Ferrostatin‐1 dramatically reduced particle‐induced ferroptosis in vitro. Moreover, in osteoblasts, CoNPs significantly downregulated the expression of Nrf2 (nuclear factor erythroid 2‐related factor 2), a core element in the antioxidant response. The overexpression of Nrf2 by siKeap1 or Nrf2 activator Oltipraz obviously upregulated antioxidant response elements (AREs) and suppressed ferroptosis in osteoblasts. Furthermore, in PIO animal models, the combined utilization of Ferrostatin‐1 and Oltipraz dramatically ameliorated ferroptosis and the severity of osteolysis.

Conclusions

These results indicate that CoNPs promote osteoblast ferroptosis by regulating the Nrf2‐ARE signalling pathway, which suggests a new mechanism underlying PIO and represents a potential therapeutic approach for AL.

The roles of metastasis-related proteins in the development of giant cell tumor of bone, osteosarcoma and Ewing's sarcoma

BACKGROUND:

Giant cell tumor of bone (GC), osteosarcoma (OS) and Ewing’s sarcoma (ES) are three different types of bone cancer with common and specific pathology features.

OBJECTIVE:

The purpose of the study was to examine the relationship and differences of the three bone tumors using clinical samples.

METHODS:

Through screening the profiles of clinical samples from GC, OS and ES patients using a humanoncology array, we found 26, 25 and 15 tumorigenesis factors significantly increased in GS, OS and ES tissues compared to normal individuals. eNOS, endostatin, HIF-1α, IL-6, CCL2/MCP-1, CCL8/MCP-2, CCL7/MCP-3, Tie and VEGF directly or indirectly involve in the metastasis Therefore, expression levels of the 6 factors were further determined by Western blot.

RESULTS:

The results showed levels of MCP1, MCP2, MCP3 or IL-6 in the GS, OS and ES significantly increased, and the expression levels of angiogenesis and anti-angiogenesis factors containing eNOS, endostatin, HIF-1α, Tie or VEGF were enhanced.

CONCLUSIONS:

Our results suggest that eNOS, endostatin, HIF-1α, IL-6, CCL2/MCP-1, CCL8/MCP-2, CCL7/MCP-3, Tie and VEGF may play important roles in tumorigenesis, reveal the expression differences of tumor-associated cytokines and angiogenesis related factors, and provide clinical evidence for studying the mechanisms on the metastasis in GC, OS and ES.

Single-Cell Transcriptomics Reveals the Complexity of the Tumor Microenvironment of Treatment-Naive Osteosarcoma

Osteosarcoma (OS), which occurs most commonly in adolescents, is associated with a high degree of malignancy and poor prognosis. In order to develop an accurate treatment for OS, a deeper understanding of its complex tumor microenvironment (TME) is required. In the present study, tissues were isolated from six patients with OS, and then subjected to single-cell RNA sequencing (scRNA-seq) using a 10× Genomics platform. Multiplex immunofluorescence staining was subsequently used to validate the subsets identified by scRNA-seq. ScRNA-seq of six patients with OS was performed prior to neoadjuvant chemotherapy, and data were obtained on 29,278 cells. A total of nine major cell types were identified, and the single-cell transcriptional map of OS was subsequently revealed. Identified osteoblastic OS cells were divided into five subsets, and the subsets of those osteoblastic OS cells with significant prognostic correlation were determined using a deconvolution algorithm. Thereby, different transcription patterns in the cellular subtypes of osteoblastic OS cells were reported, and key transcription factors associated with survival prognosis were identified. Furthermore, the regulation of osteolysis by osteoblastic OS cells via receptor activator of nuclear factor kappa-B ligand was revealed. Furthermore, the role of osteoblastic OS cells in regulating angiogenesis through vascular endothelial growth factor-A was revealed. C3_TXNIP⁺ macrophages and C5_IFIT1⁺ macrophages were found to regulate regulatory T cells and participate in CD8⁺ T cell exhaustion, illustrating the possibility of immunotherapy that could target CD8⁺ T cells and macrophages. Our findings here show that the role of C1_osteoblastic OS cells in OS is to promote osteolysis and angiogenesis, and this is associated with survival prognosis. In addition, T cell depletion is an important feature of OS. More importantly, the present study provided a valuable resource for the in-depth study of the heterogeneity of the OS TME.

Osteosarcoma and Metastasis Associated Bone Degradation-A Tale of Osteoclast and Malignant Cell Cooperativity

Cancer-induced bone degradation is part of the pathological process associated with both primary bone cancers, such as osteosarcoma, and bone metastases originating from, e.g., breast, prostate, and colon carcinomas. Typically, this includes a cancer-dependent hijacking of processes also occurring during physiological bone remodeling, including osteoclast-mediated disruption of the inorganic bone component and collagenolysis. Extensive research has revealed the significance of osteoclast-mediated bone resorption throughout the course of disease for both primary and secondary bone cancer. Nevertheless, cancer cells representing both primary bone cancer and bone metastasis have also been implicated directly in bone degradation. We will present and discuss observations on the contribution of osteoclasts and cancer cells in cancer-associated bone degradation and reciprocal modulatory actions between these cells. The focus of this review is osteosarcoma, but we will also include relevant observations from studies of bone metastasis. Additionally, we propose a model for cancer-associated bone degradation that involves a collaboration between osteoclasts and cancer cells and in which both cell types may directly participate in the degradation process.

A Targeted Erythrocyte Membrane-Encapsulated Drug-Delivery System with Anti-osteosarcoma and Anti-osteolytic Effects

Chemotherapy is one of the main treatment methods for osteosarcoma. However, conventional chemotherapy lacks targeting properties, and its long-term and extensive use will have serious side effects on patients. For this reason, a multifunctional nanodrug system (V-RZCD) targeting osteosarcoma was developed in this study. V-RZCD consists of two parts: (1) the core (ZCD), wherein calcium ions (Ca2+) and zoledronic acid (ZA) form a metal-organic framework for loading doxorubicin (DOX), and (2) the shell (V-R), a vascular endothelial growth factor (VEGF) ligand-modified red blood cell membrane nanovesicle. By targeting the VEGF, V-RZCD can specifically bind to the VEGF receptors that are highly expressed on the surface of osteosarcoma cells. Importantly, compared with free ZA and DOX, V-RZCD not only clearly inhibits the proliferation of osteosarcoma but also significantly inhibits osteolysis induced by osteosarcoma. In summary, V-RZCD represents a new way to treat osteosarcoma.

Bromodomain Inhibition Attenuates the Progression and Sensitizes the Chemosensitivity of Osteosarcoma by Repressing GP130/STAT3 Signaling

Osteosarcoma is the most common primary malignant bone tumor, and there are few ideal clinically available drugs. The bromodomain and extraterminal domain (BET) protein is an emerging target for aggressive cancer, but therapies targeting the BET in osteosarcoma have been unsuccessful in clinical trials to date, and further exploration of specific BET inhibitors is of great significance. In our study, we demonstrated that NHWD-870, a potent BET inhibitor in a phase I clinical trial, significantly inhibited tumor proliferation and promoted cell apoptosis by reversing the oncogenic signature in osteosarcoma. More importantly, we identified NHWD-870 impeded binding of BRD4 to the promoter of GP130 leading to diminished activation of JAK/STAT3 signaling pathway. Furthermore, GP130 knockdown significantly sensitizes the chemosensitivity in vitro. In OS cell-derived xenografts, NHWD-870 effectively inhibited the growth of osteosarcoma. Beyond that, NHWD-870 effectively inhibited the differentiation and maturation of precursor osteoclasts in vitro and attenuated osteoclast-mediated bone loss in vivo. Finally, we confirmed the efficacy of synthetic lethal effects of NHWD-870 and cisplatin in antagonizing osteosarcoma in a preclinical PDX model. Taken together, these findings demonstrate that NHWD-870, as an effective BET inhibitor, may be a potential candidate for osteosarcoma intervention linked to its STAT3 signaling inhibitory activity. In addition, NHWD-870 appears to be a promising therapeutic strategy for bone-associated tumors, as it interferes with the vicious cycle of tumor progression and bone destruction.

Nitrogen-containing bisphosphonate-loaded micro-arc oxidation coating for biodegradable magnesium alloy pellets inhibits osteosarcoma through targeting of the mevalonate pathway

Osteosarcoma (OS) remains one of the most threatening primary malignant human tumors of the bone, especially in the first or second decade of life. Unfortunately, the clinical therapeutic efficacy has not substantially improved over the past four decades. Therefore, to achieve efficient tumor eradication, a new approach to prevent tumor recurrence is urgently needed. Here, we develop a new bisphosphonate (BP)-loaded microarc oxidation (MAO) coated magnesium-strontium (Mg-Sr) alloy pellet that can inhibit OS, and we illuminate the cellular and molecular mechanisms of the inhibiting effect. To generate such pellets, nitrogen-containing BP is chemically conjugated with a MAO coating on hollow Mg-Sr alloys. We demonstrate that BP coated Mg pellet has multiple desired features for OS therapy through in vitro and in vivo studies. At the cellular level, BP coated Mg pellets not only induce apoptosis and necrosis, as well as antitumor invasion of OS cells in the two-dimensional (2D) cell culture environment, but also damage the formation of multicellular tumor spheroids by OS cell lines in the three-dimensional (3D) cell culture environment. At the in vivo level, BP coated Mg pellets can destroy tumors and prevent neoplasm recurrence via synergistic Mg degradation and drug release. It is further suggested that the superior inhibitory effect on OS of our pellet is achieved by inhibiting the mevalonate pathway at the molecular level. Hence, these results collectively show that the BP coated Mg pellet is a promising candidate for future applications in repairing defects after tumor removal in OS therapy.

Monocyte Chemoattractant Protein-1 promotes cancer cell migration via c-Raf/MAPK/AP-1 pathway and MMP-9 production in osteosarcoma

Background

Osteosarcoma is generally reported among younger individuals and has a very poor prognosis, particularly for the development of metastasis. However, more effective metastatic biomarkers and therapeutic methods are absent. Monocyte chemoattractant protein-1 (MCP-1) is involved in cancer progression and inflammatory recruitment. Although previous studies have reported higher serum MCP-1 levels in patients with osteosarcoma, the role of MCP-1 in osteosarcoma progression remains to be addressed.

Methods

The osteosarcoma cell migratory ability was assessed by transwell migration assay. The MCP-1 and MMP-9 expression levels were analyzed by Western blot and qPCR. The signal activation was conducted by Western blot. The in vivo mouse experiment and tumor tissue array were performed to confirm our findings in vitro.

Results

The present study demonstrates that MCP-1 regulates cell mobility through matrix metalloproteinase (MMP)-9 expression in osteosarcoma cells. Moreover, MCP-1 promotes MMP-9 expression, cell migration, and cell invasion by mediating CCR2, c-Raf, MAPK, and AP-1 signal transduction. Using MCP-1 knockdown stable cell lines, we found that MCP-1 knockdown reduces MMP-9 expression and cell mobility. Finally, we found high MCP-1 expression levels in osteosarcoma specimens.

Conclusions

Our results provide prognostic value of MCP-1 in osteosarcoma by promoting MMP-9 expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01756-y.

The Osteosarcoma Microenvironment: A Complex But Targetable Ecosystem

Osteosarcomas are the most frequent primary bone sarcomas, affecting mainly children, adolescents, and young adults, and with a second peak of incidence in elderly individuals. The current therapeutic management, a combined regimen of poly-chemotherapy and surgery, still remains largely insufficient, as patient survival has not improved in recent decades. Osteosarcomas are very heterogeneous tumors, both at the intra- and inter-tumor level, with no identified driver mutation. Consequently, efforts to improve treatments using targeted therapies have faced this lack of specific osteosarcoma targets. Nevertheless, these tumors are inextricably linked to their local microenvironment, composed of bone, stromal, vascular and immune cells and the osteosarcoma microenvironment is now considered to be essential and supportive for growth and dissemination. This review describes the different actors of the osteosarcoma microenvironment and gives an overview of the past, current, and future strategies of therapy targeting this complex ecosystem, with a focus on the role of extracellular vesicles and on the emergence of multi-kinase inhibitors.

Recent advances in bone-targeted therapy

The coordination between bone resorption and bone formation plays an essential role in keeping the mass and microstructure integrity of the bone in a steady state. However, this balance can be disturbed in many pathological conditions of the bone. Nowadays, the classical modalities for treating bone-related disorders are being challenged by severe obstacles owing to low tissue selectivity and considerable safety concerns. Moreover, as a highly mineralized tissue, the bone shows innate rigidity, low permeability, and reduced blood flow, features that further hinder the effective treatment of bone diseases. With the development of bone biology and precision medicine, one novel concept of bone-targeted therapy appears to be promising, with improved therapeutic efficacy and minimized systematic toxicity. Here we focus on the recent advances in bone-targeted treatment based on the unique biology of bone tissues. We summarize commonly used bone-targeting moieties, with an emphasis on bisphosphonates, tetracyclines, and biomimetic bone-targeting moieties. We also introduce potential bone-targeting strategies aimed at the bone matrix and major cell types in the bone. Based on these bone-targeting moieties and strategies, we discuss the potential applications of targeted therapy to treat bone diseases. We expect that this review will put together useful insights to help with the search for therapeutic efficacy in bone-related conditions.

CCL2 promotes macrophages-associated chemoresistance via MCPIP1 dual catalytic activities in multiple myeloma

We previously showed that the chemokine CCL2 can recruit macrophages (Mφs) to the bone marrow (BM) in multiple myeloma (MM) and that myeloma-associated Mφs are important in drug resistance. Here, we explore the role of increased CCL2 expression in the BM microenvironment of MM and elucidate the underlying mechanism. Our results show that CCL2 expression is associated with the treatment status of MM patients. Mφs interact with MM cells and further upregulate their expression of CCL2. These increased level of CCL2 polarizes Mφs toward the M2-like phenotype and promotes Mφs to protect MM cells from drug-induced apoptosis. Mechanistically, CCL2 upregulated the expression of the immunosuppressive molecular MCP-1-induced protein (MCPIP1) in Mφs. MCPIP1 mediates Mφs’ polarization and protection via dual catalytic activities. Additionally, we found that CCL2 induces MCPIP1 expression via the JAK2-STAT3 signaling pathway. Taken together, our results indicate that increased CCL2 expression in MM patients’ BM polarizes Mφs toward the M2-like phenotype and promotes the protective effect of Mφs through MCPIP1, providing novel insight into the mechanism of Mφs-mediated drug resistance in MM.

Osteomimetic matrix components alter cell migration and drug response in a 3D tumour-engineered osteosarcoma model

Osteosarcoma management continues to lack the appropriate prognostic tools to assign personalised treatment. This leaves non-responders to standard care vulnerable to recurring disease and pulmonary metastases. Developing 3D in vitro disease models to serve as a test bed for personalised treatment is a promising approach to address this issue. This study describes the generation of 3D osteosarcoma models termed "tumouroids", which are geometrically compartmentalised to reproduce the bone cancer mass and its surrounding. Although the tumour microenvironment impacts osteosarcoma in many ways, this model focussed on interrogating the influence of a biomimetic matrix on tumour cell behaviour. The 3D matrix was supplemented with the bone-marrow proteins laminin, fibronectin and NuOss® bone granules. This led to increased invasion of osteosarcoma cell aggregates from within the bone-like matrix into the surrounding acellular bone marrow-like ECM. The presence of bone granules also yielded an atypical molecular profile of osteosarcoma cells, suggesting malignant metabolic reprogramming. Changes include decreased MMP-9 (p < 0.05) and increased PTEN (p < 0.05), MCP-1 (p < 0.01) and MCT-4 (p < 0.05) gene expression. This complex 3D biomimetic composition also changed cellular responses to doxorubicin, a common chemotherapeutic agent used to treat osteosarcoma, and reproduced key issues of in vivo treatment like drug penetrance and doxorubicin-induced bone toxicity. This work highlights the importance of a biomimetic matrix in 3D osteosarcoma models for both basic and translational research. STATEMENT OF SIGNIFICANCE: This study describes the generation of 3D osteosarcoma models termed "tumouroids", which are geometrically compartmentalised to reproduce the bone cancer mass and its environment. Utilising this novel model, specific parameters of osteosarcoma growth and invasion were investigated. Osteosarcoma cell lines proliferate at a slower rate, exhibit malignant metabolic reprogramming, and respond to drug intervention at lower concentrations of doxorubicin hydrochloride in matrix-complex compared to basic tumouroids. As such, this study provides evidence that the tumour microenvironment impacts osteosarcoma in many ways. The osteosarcoma tumouroid described herein may form the basis of a personalised-medicine strategy, which will allow the testing of drug effectiveness similar to that used for antibiotic selection for pathogenic bacteria.

Effect of Thrombin-Induced MCP-1 and MMP-3 Production Via PAR1 Expression in Murine Intervertebral Discs

Structural changes in nucleus pulposus cells induce intervertebral disc (IVD) degeneration as a consequence of cytokine generation, biochemical products, and changes in the local environment. We have previously shown that inflammatory cytokines induce murine IVD (mIVD) angiogenesis and macrophage migration. Although the physiological roles of thrombin, a known proinflammatory factor, are documented, its relationship to IVD degeneration remains largely unexplored. Thrombin mediates cellular responses via the activation of protease-activated receptors such as PAR1 which has been studied in numerous cell types, but not extensively in IVD cells. This study was designed to investigate the endogenous expression of thrombin, tissue factor, and PAR1 in cultured coccygeal mIVDs. Thrombin exclusively induced MCP-1 via the MAPK-ERK and PI3K-AKT pathways. MCP-1 produced by mIVDs induced macrophage migration and thrombin treatment increased MMP-3 production to induce mIVD degeneration. These effects of thrombin on mIVDs were abrogated by a PAR1 inhibitor and suggest that thrombin may be a novel factor capable of stimulating cytokine activity implicated in the regulation several aspects of mIVDs. Mechanisms governing mIVDs, which are regulated by thrombin/PAR1 signaling, require elucidation if our understanding of IVD degenerative mechanisms is to advance.

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.

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

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

Angiopoietin-like 4 promotes osteosarcoma cell proliferation and migration and stimulates osteoclastogenesis

BACKGROUND

Osteosarcoma is the most common primary bone cancer in children and young adults. It is highly aggressive and patients that present with metastasis have a poor prognosis. Angiopoietin-like 4 (ANGPTL4) drives the progression and metastasis of many solid tumours, but has not been described in osteosarcoma tissue. ANGPTL4 also enhances osteoclast activity, which is required for osteosarcoma growth in bone. We therefore investigated the expression and function of ANGPTL4 in human osteosarcoma tissue and cell lines.

METHODS

Expression of ANGPTL4 in osteosarcoma tissue microarrays was determined by immunohistochemistry. Hypoxic secretion of ANGPTL4 was tested by ELISA and Western blot. Regulation of ANGPTL4 by hypoxia-inducible factor (HIF) was investigated using isoform specific HIF siRNA (HIF-1α, HIF-2α). Effects of ANGPTL4 on cell proliferation, migration (scratch wound assay), colony formation and osteoblastogenesis were assessed using exogenous ANGPTL4 or cells stably transfected with ANGPTL4. Osteoclastogenic differentiation of CD14+ monocytes was assessed by staining for tartrate-resistant acid phosphatase (TRAP), bone resorption was assessed by lacunar resorption of dentine.

RESULTS

ANGPTL4 was immunohistochemically detectable in 76/109 cases. ANGPTL4 was induced by hypoxia in 6 osteosarcoma cell lines, under the control of the HIF-1α transcription factor. MG-63 cells transfected with an ANGPTL4 over-expression plasmid exhibited increased proliferation and migration capacity and promoted osteoclastogenesis and osteoclast-mediated bone resorption. Individually the full-length form of ANGPTL4 could increase MG-63 cell proliferation, whereas N-terminal ANGPTL4 mediated the other pro-tumourigenic phenotypes.

CONCLUSIONS

This study describes a role(s) for ANGPTL4 in osteosarcoma and identifies ANGPTL4 as a treatment target that could potentially reduce tumour progression, inhibit angiogenesis, reduce bone destruction and prevent metastatic events.

Transforming Growth Factor-β Signaling Plays a Pivotal Role in the Interplay Between Osteosarcoma Cells and Their Microenvironment

Osteosarcomas are the most frequent form of primary bone tumors and mainly affect children, adolescents, and young adults. Despite encouraging progress in therapeutic management, including the advent of multidrug chemotherapy, the survival rates have remained unchanged for more than four decades: 75% at 5 years for localized disease, but two groups of patients are still at high risk: metastatic at diagnosis (overall survival around 40% at 5 years) and/or poor responders to chemotherapy (20% at 5 years). Because these tumors are classified as “complex genomic,” it is extremely difficult to determine the signaling pathways that might be targeted by specific therapies. A hypothesis has thus emerged, stating that the particular microenvironment of these tumors may interfere with the tumor cells that promote chemoresistance and the dissemination of metastases. The stroma is composed of a large number of cell types (immune cells, endothelial cells, mesenchymal stromal cells, etc.) which secrete growth factors, such as transforming growth factor-β (TGF-β), which favors the development of primary tumors and dissemination of metastases by constituting a permissive niche at primary and distant sites. Rather than targeting the tumor cells themselves, which are very heterogeneous in osteosarcoma, the hypothesis is instead to target the key actors secreted in the microenvironment, such as TGF-βs, which play a part in tumor progression. In the last decade, numerous studies have shown that overexpression of TGF-β is a hallmark of many cancers, including primary bone tumors. In this context, TGF-β signaling has emerged as a crucial factor in the cross talk between tumor cells and stroma cells in poor-prognosis cancers. Secretion of TGF-β by tumor cells or stroma cells can effectively act in a paracrine manner to regulate the phenotype and functions of the microenvironment to stimulate protumorigenic microenvironmental changes. TGF-β can thus exert its protumorigenic function in primary bone tumors by promoting angiogenesis, bone remodeling and cell migration, and by inhibiting immunosurveillance. This review focuses on the involvement of TGF-β signaling in primary bone tumor development, and the related therapeutic options that may be possible for these tumors.

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.

Role of Tumor-Derived Chemokines in Osteolytic Bone Metastasis

Metastasis is the primary cause of mortality and morbidity in cancer patients. The bone marrow is a common destination for many malignant cancers, including breast carcinoma (BC), prostate carcinoma, multiple myeloma, lung carcinoma, uterine cancer, thyroid cancer, bladder cancer, and neuroblastoma. The molecular mechanism by which metastatic cancer are able to recognize, infiltrate, and colonize bone are still unclear. Chemokines are small soluble proteins which under normal physiological conditions mediate chemotactic trafficking of leukocytes to specific tissues in the body. In the context of metastasis, the best characterized role for the chemokine system is in the regulation of primary tumor growth, survival, invasion, and homing to specific secondary sites. However, there is ample evidence that metastatic tumors exploit chemokines to modulate the metastatic niche within bone which ultimately results in osteolytic bone disease. In this review, we examine the role of chemokines in metastatic tumor growth within bone. In particular, the chemokines CCL2, CCL3, IL-8/CXCL8, and CXCL12 are consistently involved in promoting osteoclastogenesis and tumor growth. We will also evaluate the suitability of chemokines as targets for chemotherapy with the use of neutralizing antibodies and chemokine receptor-specific antagonists.

Angiotensin II induces monocyte chemoattractant protein‑1 expression by increasing reactive oxygen species‑mediated activation of the nuclear factor‑κB signaling pathway in osteoblasts

The present study investigated the effect of angiotensin II (Ang II) on monocyte chemoattractant protein‑1 (MCP‑1) expression and the underlying mechanism in osteoblasts. MCP‑1 expression levels were analyzed by ELISA and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Ang II type 1 receptor (AT1R) expression levels was examined by RT‑qPCR, western blotting and immunostaining. In addition, the nuclear factor (NF)‑κB signaling pathway was investigated via western blot analysis. Reactive oxygen species (ROS) were also detected by flow cytometry and fluorescent microscopy. The results of the present study ndicated that Ang II upregulated MCP‑1 expression in osteoblasts, which was mitigated by agonists of the AT1R, including olmesartan, a ROS scavenger N‑acetylcysteine (NAC), ammonium pyrrolidinethiocarbamate (PDTC) and nuclear factor (NF)‑κB, but not by the Ang II type 2 receptor antagonist, PD123319. Furthermore, Ang II increased the generation of ROS and activated the NF‑κB signaling pathway. These effects of Ang II were blocked by olmesartan, NAC and PDTC, but not by PD1123319 in osteoblasts. In conclusion, these data indicated that Ang II enhanced ROS production and activated NF‑κB signaling via AT1R, thus upregulating MCP‑1 expression in osteoblasts.

Role of zoledronic acid in oncolytic virotherapy: Promotion of antitumor effect and prevention of bone destruction

Osteosarcoma is an aggressive malignant bone tumor that causes bone destruction. Although tumor‐specific replicating oncolytic adenovirus OBP‐301 induces an antitumor effect in an osteosarcoma tumor, it cannot prevent bone destruction. Zoledronic acid (ZOL) is a clinically available agent that inhibits bone destruction. In this study, we investigated the potential of combination therapy with OBP‐301 and ZOL against osteosarcomas with bone destruction. The antitumor activity of OBP‐301 and ZOL in monotherapy or combination therapy was assessed using three human osteosarcoma cell lines (143B, MNNG/HOS, SaOS‐2). The cytotoxic effect of OBP‐301 and/or ZOL was measured by assay of cell apoptosis. The effect of OBP‐301 and ZOL on osteoclast activation was investigated. The potential of combination therapy against tumor growth and bone destruction was analyzed using an orthotopic 143B osteosarcoma xenograft tumor model. OBP‐301 and ZOL decreased the viability of human osteosarcoma cells. Combination therapy with OBP‐301 and ZOL displayed a synergistic antitumor effect, in which OBP‐301 promoted apoptosis through suppression of anti‐apoptotic myeloid cell leukemia 1 (MCL1). Combination therapy significantly inhibited tumor‐mediated osteoclast activation, tumor growth and bone destruction compared to monotherapy. These results suggest that combination therapy of OBP‐301 and ZOL suppresses osteosarcoma progression via suppression of MCL1 and osteoclast activation.

Mesenchymal stroma: Role in osteosarcoma progression

The initiation and progression of malignant tumors are supported by their microenvironment: cancer cells per se cannot explain growth and formation of the primary or metastasis, and a combination of proliferating tumor cells, cancer stem cells, immune cells mesenchymal stromal cells and/or cancer-associated fibroblasts all contribute to the tumor bulk. The interaction between these multiple players, under different microenvironmental conditions of biochemical and physical stimuli (i.e. oxygen tension, pH, matrix mechanics), regulates the production and biological activity of several soluble factors, extracellular matrix components, and extracellular vesicles that are needed for growth, maintenance, chemoresistance and metastatization of cancer. In osteosarcoma, a very aggressive cancer of young adults characterized by the extensive need for more effective therapies, this aspect has been only recently explored. In this view, we will discuss the role of stroma, with a particular focus on the mesenchymal stroma, contributing to osteosarcoma progression through inherent features for homing, neovascularization, paracrine cross-feeding, microvesicle secretion, and immune modulation, and also by responding to the changes of the microenvironment that are induced by tumor cells. The most recent advances in the molecular cues triggered by cytokines, soluble factors, and metabolites that are partially beginning to unravel the axis between stromal elements of mesenchymal origin and osteosarcoma cells, will be reviewed providing insights likely to be used for novel therapeutic approaches against sarcomas.

Evaluation of intraarterial and intravenous cisplatin chemotherapy in the treatment of metastatic osteosarcoma using an orthotopic xenograft mouse model

Background

Osteosarcoma is the most common primary malignancy of bone. Its treatment relies on the administration of neoadjuvant and adjuvant chemotherapy combined with surgery. Alternative to common intravenous (i.v.) administration of chemotherapeutic drugs, clinical studies also evaluated the benefit of intraarterial (i.a.) administrations. However, conflicting results were obtained when both routes of administration of cisplatin (CDDP), a gold standard drug in osteosarcoma treatment, were compared. In order to overcome clinical confounding factors, we evaluated both routes of drug administration in a mouse model of experimental osteosarcoma.

Methods

We directly compared i.v. versus i.a. drug infusions of cisplatin (CDDP), in an orthotopic xenograft mouse model of metastatic osteosarcoma. We performed tumor monitoring using caliper and micro computed tomography and measured tumor perfusion using laser speckle contrast imaging. Histopathological changes were evaluated using hematoxylin and eosin staining as well as immunohistochemistry (cleaved PARP-1, CD31, HIF-1α).

Results

First, an effective concentration of 4 mg/kg i.a. CDDP was determined that significantly reduced primary tumor volume. We used this concentration of i.a. CDDP and compared it to infusions of i.v. CDDP. Systemic (i.v.) CDDP only showed minor suppression of tumor growth whereas local (i.a.) CDDP strongly inhibited tumor growth and destruction of cortical bone in the tumor-bearing hind limb. Inhibition of tumor growth was linked to a reduced blood perfusion and resulted in increased amounts of tumor necrosis after i.a. CDDP. After treatment with i.a. CDDP, remaining viable tumor tissue responded by increasing expression of HIF-1α. Side effects due to administration of CDDP were minor, showing no differences in kidney damage between i.v. and i.a. CDDP. However, increased epidermal apoptosis in the foot was an indirect marker for locally increased concentrations of CDDP.

Conclusions

Our findings demonstrate the great potential of local administration of cytotoxic chemotherapeutics, such as CDDP. Consequently, we provide a preclinical basis for a renewed interest in the clinical use of i.a. chemotherapy in osteosarcoma therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0392-1) contains supplementary material, which is available to authorized users.

Deciphering signaling networks in osteosarcoma pathobiology

Osteosarcoma is the most frequent type of primary bone tumors among children and adolescents. During the past years, little progress has been made regarding prognosis of osteosarcoma patients, especially for those with metastatic disease. Genomic instability and gene alterations are common, but current data do not reveal a consistent and repeatable pattern of osteosarcoma development, thus paralleling the tumor's high heterogeneity. Critical signal transduction pathways have been implicated in osteosarcoma pathobiology and are being evaluated as therapeutic targets, including receptor activator for nuclear factor-κB (RANK), Wnt, Notch, phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin, and mechanotransduction pathways. Herein, we recapitulate and discuss recent advances in the context of molecular mechanisms and signaling networks that contribute to osteosarcoma progression and metastasis, towards patient-tailored and novel-targeted treatments.

The enhancing effect of a laser photochemotherapy with cisplatin or zolendronic acid in primary human osteoblasts and osteosarcoma cells in vitro

BACKGROUND

Photodynamic therapies (PDT) have become increasingly popular in the adjuvant treatment of different tumour entities. Chemotherapeutic agents, such as cisplatin may be used in combination with low-level laser therapy (LLLT) as laser photochemotherapy. The aim of this study was to investigate the effect of LLLT on cell bioviability of normal and malignant bone cells under chemotherapeutic conditions with either cisplatin or zolendronic acid in vitro.

METHODS

Primary human osteoblasts (HOB) and an osteosarcoma cell line (Saos-2) were treated with different concentrations of zolendronic acid or cisplatin and irradiated twice with a diode laser (wavelength 670 nm, 120 s, energy outputs of 100mW/cm² , continuous wave mode). Cell viability was tested by XTT-assay and via histomorphological analysis.

RESULTS

LLLT alone increased bioviability for both cell lines. LLLT lowered HOB viability at the three highest concentrations of cisplatin and zolendronic acid. For Saos-2, LLLT reduced cell viability at every concentration of cisplatin. In cases of incubation with zolendronic acid, similar to osteoblasts, LLLT lowered cell viability at the highest concentration only.

CONCLUSIONS

Based on the conditions of this study, laser photochemotherapy may be able to raise the cytotoxicity of cisplatin and zolendronic acid in benign and malignant bone cells. This could be of interest in the development of new therapeutic treatment modalities against neoplastic bone diseases like osteosarcoma.

Toward a noncytotoxic glioblastoma therapy: blocking MCP-1 with the MTZ Regimen

To improve the prognosis of glioblastoma, we developed an adjuvant treatment directed to a neglected aspect of glioblastoma growth, the contribution of nonmalignant monocyte lineage cells (MLCs) (monocyte, macrophage, microglia, dendritic cells) that infiltrated a main tumor mass. These nonmalignant cells contribute to glioblastoma growth and tumor homeostasis. MLCs comprise of approximately 10%-30% of glioblastoma by volume. After integration into the tumor mass, these become polarized toward an M2 immunosuppressive, pro-angiogenic phenotype that promotes continued tumor growth. Glioblastoma cells initiate and promote this process by synthesizing 13 kDa MCP-1 that attracts circulating monocytes to the tumor. Infiltrating monocytes, after polarizing toward an M2 phenotype, synthesize more MCP-1, forming an amplification loop. Three noncytotoxic drugs, an antibiotic - minocycline, an antihypertensive drug - telmisartan, and a bisphosphonate - zoledronic acid, have ancillary attributes of MCP-1 synthesis inhibition and could be re-purposed, singly or in combination, to inhibit or reverse MLC-mediated immunosuppression, angiogenesis, and other growth-enhancing aspects. Minocycline, telmisartan, and zoledronic acid - the MTZ Regimen - have low-toxicity profiles and could be added to standard radiotherapy and temozolomide. Re-purposing older drugs has advantages of established safety and low drug cost. Four core observations support this approach: 1) malignant glioblastoma cells require a reciprocal trophic relationship with nonmalignant macrophages or microglia to thrive; 2) glioblastoma cells secrete MCP-1 to start the cycle, attracting MLCs, which subsequently also secrete MCP-1 perpetuating the recruitment cycle; 3) increasing cytokine levels in the tumor environment generate further immunosuppression and tumor growth; and 4) MTZ regimen may impede MCP-1-driven processes, thereby interfering with glioblastoma growth.

Thrombin induced by the extrinsic pathway and PAR-1 regulated inflammation at the site of fracture repair

Thrombin (coagulation factor IIa) is a serine protease encoded by the F2 gene. Pro-thrombin (coagulation factor II) is cut to generate thrombin in the coagulation cascade that results in a reduction of blood loss. Procoagulant states that lead to activation of thrombin are common in bone fracture sites. However, its physiological roles and relationship with osteoblasts in bone fractures are largely unknown. We herein report various effects of thrombin on mouse osteoblastic MC3T3-E1 cells. MC3T3-E1 cells expressed proteinase-activated receptor 1 (PAR1), also known as the coagulation factor II receptor. They also produced monocyte chemoattractant protein (MCP-1), tissue factor (TF), MCSF and IL-6 upon thrombin stimulation through the PI3K-Akt and MEK-Erk1/2 pathways. Furthermore, MCP-1 obtained from thrombin-stimulated MC3T3-E1 cells induced migration by macrophage RAW264 cells. All these effects of thrombin on MC3T3-E1 cells were abolished by the selective non-peptide thrombin receptor inhibitor SCH79797. We also found that thrombin, PAR-1, MCP-1, TF as well as phosphorylated AKT and p42/44 were significantly expressed at the fracture site of mouse femoral bone. Collectively, thrombin/PAR-1 interaction regulated MCP-1, TF, MCSF and IL-6 production by MC3T3-E1 cells. Furthermore, MCP-1 induced RAW264 cell migration. Thrombin may thus be a novel cytokine that regulates several aspects of osteoblast function and fracture healing.

Targeting a novel bone degradation pathway in primary bone cancer by inactivation of the collagen receptor uPARAP/Endo180

In osteosarcoma, a primary mesenchymal bone cancer occurring predominantly in younger patients, invasive tumour growth leads to extensive bone destruction. This process is insufficiently understood, cannot be efficiently counteracted and calls for novel means of treatment. The endocytic collagen receptor, uPARAP/Endo180, is expressed on various mesenchymal cell types and is involved in bone matrix turnover during normal bone growth. Human osteosarcoma specimens showed strong expression of this receptor on tumour cells, along with the collagenolytic metalloprotease, MT1-MMP. In advanced tumours with ongoing bone degeneration, sarcoma cells positive for these proteins formed a contiguous layer aligned with the degradation zones. Remarkably, osteoclasts were scarce or absent from these regions and quantitative analysis revealed that this scarcity marked a strong contrast between osteosarcoma and bone metastases of carcinoma origin. This opened the possibility that sarcoma cells might directly mediate bone degeneration. To examine this question, we utilized a syngeneic, osteolytic bone tumour model with transplanted NCTC-2472 sarcoma cells in mice. When analysed in vitro, these cells were capable of degrading the protein component of surface-labelled bone slices in a process dependent on MMP activity and uPARAP/Endo180. Systemic treatment of the sarcoma-inoculated mice with a mouse monoclonal antibody that blocks murine uPARAP/Endo180 led to a strong reduction of bone destruction. Our findings identify sarcoma cell-resident uPARAP/Endo180 as a central player in the bone degeneration of advanced tumours, possibly following an osteoclast-mediated attack on bone in the early tumour stage. This points to uPARAP/Endo180 as a promising therapeutic target in osteosarcoma, with particular prospects for improved neoadjuvant therapy.

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.

Bisphosphonates in the Treatment of Patients With Metastatic Breast, Lung, and Prostate Cancer: A Meta-Analysis

The purpose of this meta-analysis was to investigate whether bisphosphonates are a key therapy for bone metastases in lung cancer, breast cancer, and prostate cancer by comparing all randomized controlled trials that appraised the effects of bisphosphonates on risk of skeletal-related events (SREs).PubMed, Embase, and Medline databases (up to December 2014) were used to search all related articles. Using the data from 19 available publications, the authors examined the efficacy in treating or reducing the risk of SREs in lung cancer, breast cancer, and prostate cancer by meta-analysis.Bisphosphonates have demonstrated efficacy in treating or reducing the risk of SREs in lung cancer [odds ratio (OR) = 0.81, 95% confidence interval (CI) = 0.69-0.95, P = 0.008], breast cancer (OR = 0.62, 95% CI = 0.54-0.71, P = 0.000), and prostate cancer (OR = 0.62, 95% CI = 0.45-0.86, P = 0.004).This meta-analysis suggests that bisphosphonates have demonstrated efficacy in treating or reducing the risk of SREs in lung cancer, breast cancer, and prostate cancer.

Rank ligand as a target in musculoskeletal neoplasms

Receptor activator of nuclear factor-κB ligand (RANKL) is a tumor necrosis factor (TNF) family member, which signals through the osteoclast surface RANK. As such, RANKL is required for osteoclast differentiation and function, namely bone resorption. There is now growing evidence that RANKL is a therapeutic target for musculoskeletal neoplasms, namely giant cell tumor of bone (GCTB) and osteosarcoma.

MicroRNA-126 enhances the sensitivity of osteosarcoma cells to cisplatin and methotrexate

The establishment of novel chemotherapy drugs for osteosarcoma is urgently required, and the mechanisms and effects of cisplatin (DDP) and methotrexate (MTX) in the current treatment of osteosarcoma have not been fully elucidated. The present study aimed to observe the effect of DDP, MTX and rapamycin on osteosarcoma cell proliferation and apoptosis, and to investigate the association between miR-126 and the effects of DDP and MTX in osteosarcoma cells. miR-126-overexpressing and -silencing lentiviral vectors were constructed, and MG63 and U-2 OS osteosarcoma cells were infected. An MTT assay was conducted to detect transfected cell proliferation, and the effects of the chemotherapy drugs on transfected cell apoptosis were detected by flow cytometry. The cell cycle of the transfected cells was analyzed via flow cytometry. As the miR-126-overexpressing and -silencing osteosarcoma cell lines were successfully constructed, it was observed that DDP and MTX inhibited osteosarcoma cell proliferation. With the decreased expression of miR-126, the sensitivity of osteosarcoma cells to DDP and MTX was reduced at the same concentration. The flow cytometry suggested that DDP and MTX could promote the apoptosis of osteosarcoma cells with overexpressed miR-126, whereas they could not significantly impact the apoptosis of the miR-126-silenced osteosarcoma cells. Meanwhile, DDP inhibited the cell cycle of the miR-126-overexpressing osteosarcoma cells. In conclusion, DDP and MTX inhibited the proliferation and promoted the apoptosis of the osteosarcoma cells, and these processes were dependent upon the expression of miR-126.