Molecular biology and therapeutics in musculoskeletal oncology

Bone Biopsies: What Radiologists Need to Know

OBJECTIVE. The purpose of this article is to provide a step-by-step guide for bone imaging-guided percutaneous core needle biopsy, including the armamentarium available and the most recent advances. CONCLUSION. Bone imaging-guided percutaneous core needle biopsies are well-established, minimally invasive, cost-effective interventions for histologic characterization of bone lesions with an excellent safety profile and diagnostic outcomes; they play a crucial role in management of patients. Radiologists involved in the care of patients with bone lesions must be familiar with the various steps involved in such procedures and their role in patient management.

Potential Molecular Mechanisms of AURKB in the Oncogenesis and Progression of Osteosarcoma Cells: A Label-Free Quantitative Proteomics Analysis

Our previous study indicated that knockdown of Aurora-B inhibit the proliferation of osteosarcoma cells. But the function and molecular mechanisms of Aurora-B in osteosarcoma cells growth and metastasis remains unclear. The aim of this study was to investigate the molecular mechanisms of Aurora-B in the progression of osteosarcoma. Osteosarcoma cells (U2-OS and 143B) were treated with specific Lentivirus-Vectors (up or downregulation Aurora-B). The ability of cells proliferation, migration, and invasion was measured using Cell-Counting Kit-8, wound healing and transwell invasion assays. Furthermore, based on label-free quantitative proteomic analysis of potential molecular mechanisms of Aurora-B in human 143B cells. A total of 25 downregulated and 76 upregulated differentially expressed proteins were screened in terms of the change in their expression abundance. We performed functional annotation and functional enrichment analyses. Gene ontology enrichment, KEGG analysis, and protein-protein interaction networks were constructed and analyzed. We found that the PTK2 may play an important role in the progression of osteosarcoma cells. Finally, Western blot revealed that expression of PTK2, AKT, PI3K, and nuclear factor-kappaB increased after over expression of Aurora-B. Overall, these data highlight that Aurora-B may promote the malignant phenotype of osteosarcoma cells by activating the PTK2/PI3K/AKt/nuclear factor-KappaB pathway.

Construction of microRNA-messenger networks for human osteosarcoma

Osteosarcoma is the most common bone tumor in children and young adults. Although the microRNAs (miRNA) expression analyses of osteosarcoma have been performed previously, the construction of miRNA-messenger RNA (mRNA) networks for osteosarcoma is needed. This study aimed to identify osteosarcoma-related miRNAs through analyzing the microarray datasets and to construct the regulatory network of miRNA-mRNA for human osteosarcoma. The datasets were extracted from the Gene Expression Omnibus and the differentially expressed miRNAs were screened through the limma package in Bioconductor. Genes targeted by the differentially expressed miRNAs were screened out by using the Miranda, MirTarget2, PicTar, PITA, and TargetScan databases. The predicted target genes were further analyzed by Gene Ontology and pathway enrichment analysis and a regulatory network of differentially expressed miRNAs and their target osteosarcoma-associated genes was constructed. A total of 36 downregulated miRNAs and 182 upregulated miRNAs were identified in osteosarcoma samples compared with normal samples and 397 target genes for upregulated miRNAs and 222 target genes for downregulated miRNAs were obtained. The enriched pathways for target genes of differentially expressed miRNAs included transcriptional misregulation in cancer, the AMPK signaling pathway, and MAPK signaling pathway. In the regulatory network, has-miR-199a-5p targeted the highest number of genes and nemo-like kinase (NLK) was targeted by five miRNAs (hsa-miR-140-5p, hsa-miR-107, hsa-miR-324-5p, hsa-miR-199a-5p, and hsa-miR-28-5p). The has-miR-324-5p targets NLK, TGFB2, and PPARG. These miRNAs and their target genes may serve as potential therapeutic targets of osteosarcoma.

STK39, overexpressed in osteosarcoma, regulates osteosarcoma cell invasion and proliferation

Serine/threonine kinase 39 (STK39) is associated with hypertension, autism, Parkinson's disease and various types of cancer in recent years. This study investigated STK39 expression and possible roles in osteosarcoma using qPCR and western blot analysis. Compared to normal bone tissues, the mRNA and protein expression of STK39 was found to be upregulated in osteosarcoma. Using small interfering RNA transfection, STK39 was knocked down into two cell lines of osteosarcoma, U2OS and MG63, and the effects exerted on cell functioning were examined. The results showed that STK39 downregulation inhibited ostesarcoma cell proliferation and invasion. Moreover, STK39 knockdown in osteosarcoma cells significantly affected the expression of proteins connected to cell proliferation (proliferating cell nuclear antigen and p21) and invasion [Twist1, matrix metalloproteinase (MMP)2 and MMP9]. Phosphorylation of Smad2/3 was reduced by STK39 knock down. In conclusion, our data provide evidence that STK39 was overexpressed in osteosarcoma. STK39 may serve as an oncogene by adjusting the proliferation and invasion of osteosarcoma cells.

Upregulation and biological function of transmembrane protein 119 in osteosarcoma

Osteosarcoma is suggested to be caused by genetic and molecular alterations that disrupt osteoblast differentiation. Recent studies have reported that transmembrane protein 119 (TMEM119) contributes to osteoblast differentiation and bone development. However, the level of TMEM119 expression and its roles in osteosarcoma have not yet been elucidated. In the present study, TMEM119 mRNA and protein expression was found to be up-regulated in osteosarcoma compared with normal bone cyst tissues. The level of TMEM119 protein expression was strongly associated with tumor size, clinical stage, distant metastasis and overall survival time. Moreover, gene set enrichment analysis (GSEA) of the Gene Expression Omnibus (GEO) GSE42352 dataset revealed TMEM119 expression in osteosarcoma tissues to be positively correlated with cell cycle, apoptosis, metastasis and TGF-β signaling. We then knocked down TMEM119 expression in U2OS and MG63 cells using small interfering RNA, which revealed that downregulation of TMEM119 could inhibit the proliferation of osteosarcoma cells by inducing cell cycle arrest in G0/G1 phase and apoptosis. We also found that TMEM119 knockdown significantly inhibited cell migration and invasion, and decreased the expression of TGF-β pathway-related factors (BMP2, BMP7 and TGF-β). TGF-β application rescued the inhibitory effects of TMEM119 knockdown on osteosarcoma cell migration and invasion. Further in vitro experiments with a TGF-β inhibitor (SB431542) or BMP inhibitor (dorsomorphin) suggested that TMEM119 significantly promotes cell migration and invasion, partly through TGF-β/BMP signaling. In conclusion, our data support the notion that TMEM119 contributes to the proliferation, migration and invasion of osteosarcoma cells, and functions as an oncogene in osteosarcoma.

MicroRNA-137 is downregulated in human osteosarcoma and regulates cell proliferation and migration through targeting FXYD6

BACKGROUND

In this work, we investigated the functional role of microRNA 137 (miR-137) in regulating osteosarcoma both in vitro and in vivo.

METHODS

Quantitative RT-PCR was used to examine the gene expressions of miR-137 in osteosarcoma cell lines and osteosarcoma tumors. 143B and Saos-2 cells were infected with lentivirus expressing miR-137 mimics (miR-137-mimic) to ectopically upregulate miR-137. In vitro cancer proliferation and migration were examined by MTT assay and transwell assay, respectively. Viral infected Saos-2 cells were also subcutaneously inoculated into null mice to evaluate the effect of miR-137 upregulation on in vivo tumor growth. The interaction between miR-137 and its downstream target, FXYD6, was evaluated by dual-luciferase reporter assay and quantitative real-time PCR. FXYD6 was then subsequently upregulated in osteosarcoma cells to evaluate its effect on miR-137 regulation in osteosarcoma.

RESULTS

We found that miR-137 was significantly downregulated in both osteosarcoma cell lines and osteosarcoma tumors. Lentiviral infection of miR-137-mimic upregulated miR-137 gene expression, reduced in vitro proliferation and migration and inhibited in vivo osteosarcoma tumor growth. FXYD6 was verified to be directly interacting with miR-137, and its subsequent upregulation reversed the inhibitory effect of miR-137 upregulation in osteosarcoma.

CONCLUSION

We revealed novel functional role of miR-137 in osteosarcoma regulation, likely through FXYD6 binding.

Celastrol negatively regulates cell invasion and migration ability of human osteosarcoma via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro

Osteosarcoma (OS) is a primary malignant tumor of the bone, with a tendency to metastasize early. Despite the advances in treatment options, more than 30% of patients develop distant metastases, and the prognosis of these patients with metastases is extremely poor. Celastrol has been demonstrated to manifest multiple pharmacological activities, including induction of apoptosis in numerous types of cancer cell lines. Our previous studies have also suggested that Celastrol is capable of inducing apoptosis of human osteosarcoma cells via the mitochondrial-dependent pathway. The purpose of this study was to investigate the effects of Celastrol on the migration and invasion of human osteosarcoma U-2OS cells in vitro. Cell migration and invasion were investigated using wound healing and Boyden chamber Transwell assays. We observed that Celastrol suppressed cell invasion and migration in human osteosarcoma U-2OS cells. Furthermore, protein expression levels of phosphorylated phosphatidylinositol 3-kinase (PI3K), Akt, inhibitor of κB kinase α/β, inhibitor of κB α, nuclear factor-κB (NF-κB subunit p65) and matrix metalloproteinase (MMP)-2 and -9 were measured by western blot analysis. We observed that the PI3K/Akt/NF-κB signaling pathway was inhibited following Celastrol treatment. In addition, the expression levels of MMP-2 and -9 proteins were also reduced significantly following Celastrol treatment. Therefore, we confirmed that Celastrol suppressed osteosarcoma U-2OS cell metastasis via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro.

Silencing of Eag1 Gene Inhibits Osteosarcoma Proliferation and Migration by Targeting STAT3-VEGF Pathway

So far, the role of Ether à go-go 1 (Eag1) potassium channels in migration and invasion progression of cancers remains elusive. In the present study, the effects of Eag1 knockdown on osteosarcoma cell proliferation, growth, and apoptosis were examined. Then, we evaluated the effects of Eag1 silencing on osteosarcoma cell migration and invasion. In addition, we detected the expression of vascular endothelial growth factor (VEGF) and signal transducer and activator of transcription 3 (STAT3) in osteosarcoma cell treated with Eag1 small interfering RNAs (siRNAs). Finally, STAT3 siRNA was employed to determine the influence of downregulation of STAT3 on cell proliferation and migration. The results showed that knockdown of Eag1 significantly suppressed osteosarcoma cell proliferation and osteosarcoma xenografts growth. However, Eag1 silencing had little effect on cell apoptosis. Additionally, osteosarcoma cell adhesion, migration, and invasion were also potently attenuated. Notably, the expression levels of VEGF decreased evidently upon Eag1 siRNAs treatment, paralleled with reductions in the expression levels of STAT3. Moreover, a similar pattern was observed in osteosarcoma cell proliferation and migration suppression between STAT3 siRNA and Eag1 siRNAs groups. Our data indicated that Eag1 promotes osteosarcoma proliferation and migration, at least in part, by targeting STAT3-VEGF pathway.

A polymorphism site in the pre‑miR‑34a coding region reduces miR‑34a expression and promotes osteosarcoma cell proliferation and migration

Osteosarcoma (OS) is the most prevalent primary malignant bone tumor in children and young adults, its complex etiology involving a combination of environmental and genetic factors. MicroRNA (miRNA) is a short, non-coding regulatory RNA molecule that represses gene expression by imperfectly base-pairing to the 3′ untranslated region of target mRNAs. Evidence has shown that alterations in the expression of miRNA are involved in the initiation, progression, and metastasis of human cancers. It is believed that miRNAs function both as tumor suppressors and oncogenes during cancer development. In the present study, three tumor-associated miRNAs (miR-21, miR-34a and miR-146a) coding regions were screened in Chinese-Han OS patients. A G>A variation in the pre-miR-34a coding region was found to be associated with higher OS morbidity. By detecting the mature miR-34a expression in cells transfected with pre-miR-34a expression vectors of different genotypes using quantitative polymerase chain reaction, it was demonstrated that the G>A variation reduced miR-34a expression in vitro. This was in accordance with the data collected from tumor tissue and patient serum samples. Subsequently, a dual-luciferase reporter assay and western blot analysis were used to detect the site variation effect on the expression of c-Met, a target gene of miR-34a. The G>A variation downregulated the suppression of c-Met in two OS cell lines. Furthermore, it was found that reduced miR-34a expression decreased the suppression of OS cell proliferation in vitro. In conclusion, the present study established the association between miR-34a and the risk of suffering OS in a Chinese Han population by identifying one functional single nucleotide polymorphism site in pre-miR-34a. These findings may give insight into the mechanism of OS development and create an opportunity to approach the diagnosis and treatment of OS.

Knockdown of Aurora-B inhibits osteosarcoma cell invasion and migration via modulating PI3K/Akt/NF-κB signaling pathway

Increasing evidences reveal that Aurora-B may be involved in metastasis of malignant tumor. In this study, we investigated the inhibitory effect of Aurora-B on invasion and migration of OS cells and the activity of PI3K/Akt/NF-κB signaling pathway in vitro. The expression of Aurora-B and p-Akt (Ser473) proteins was detected by immunohistochemistry in OS tissues from 24 patients with pulmonary metastatic disease, and the relationship between Aurora-B and p-Akt was investigated. The results showed that there was a positive correlation between Aurora-B and p-Akt protein expression. Furthermore, we down-regulated the expression of Aurora-B through a recombinant lentivirus (Lv-shAURKB). Migration and invasion of cells were investigated by wound healing and transwell invasion assays. Results showed that silencing Aurora-B inhibited cell migratory and invasive ability of OS cells in vitro. Finally, knockdown of Aurora-B suppresses the activity of PI3K/Akt/NF-κB signaling pathway in OS cells. Our results indicated that knockdown of Aurora-B suppresses OS cells migratory and invasive ability via modulating the "PI3K/Akt/NF-κB" signaling pathway in vitro. The Aurora-B blocker may be a new therapeutic strategy in OS management.

The role of the bone microenvironment in skeletal metastasis

The bone microenvironment provides a fertile soil for cancer cells. It is therefore not surprising that the skeleton is a frequent site of cancer metastasis. It is believed that reciprocal interactions between tumour and bone cells, known as the “vicious cycle of bone metastasis” support the establishment and orchestrate the expansion of malignant cancers in bone. While the full range of molecular mechanisms of cancer metastasis to bone remain to be elucidated, recent research has deepened our understanding of the cell-mediated processes that may be involved in cancer cell survival and growth in bone. This review aims to address the importance of the bone microenvironment in skeletal cancer metastasis and discusses potential therapeutic implications of novel insights.

rAAV Vectors as Safe and Efficient Tools for the Stable Delivery of Genes to Primary Human Chondrosarcoma Cells In Vitro and In Situ

Treatment of chondrosarcoma remains a major challenge in orthopaedic oncology. Gene transfer strategies based on recombinant adenoassociated viral (rAAV) vectors may provide powerful tools to develop new, efficient therapeutic options against these tumors. In the present study, we tested the hypothesis that rAAV is adapted for a stable and safe delivery of foreign sequences in human chondrosarcoma tissue by transducing primary human chondrosarcoma cells in vitro and in situ with different reporter genes (E. coli lacZ, firefly luc, Discosoma sp. RFP). The effects of rAAV administration upon cell survival and metabolic activities were also evaluated to monitor possibly detrimental effects of the gene transfer method. Remarkably, we provide evidence that efficient and prolonged expression of transgene sequences via rAAV can be safely achieved in all the systems investigated, demonstrating the potential of the approach of direct application of therapeutic gene vectors as a means to treat chondrosarcoma.

MicroRNA-34a inhibits the proliferation and metastasis of osteosarcoma cells both in vitro and in vivo

Background

MicroRNAs (miRNAs) are a class of endogenously expressed, small noncoding RNAs, which suppress its target mRNAs at the post-transcriptional level. Studies have demonstrated that miR-34a, which is a direct target of the p53 tumor suppressor gene, functions as a tumor suppressor and is associated with the tumor growth and metastasis of various human malignances. However, the role of miR-34a in osteosarcoma has not been totally elucidated. In the present study, the effects of miR-34a on osteosarcoma and the possible mechanism by which miR-34a affected the tumor growth and metastasis of osteosarcoma were investigated.

Methodology/Principal Finding

Over-expression of miR-34a partially inhibited proliferation, migration and invasion of osteosarcoma cells in vitro, as well as the tumor growth and pulmonary metastasis of osteosarcoma cells in vivo. c-Met is a target of miR-34a, and regulates the migration and invasion of osteosarcoma cells. Osteosarcoma cells over-expressing miR-34a exhibited a significant decrease in the expression levels of c-Met mRNA and protein simultaneously. Finally, the results from bioinformatics analysis demonstrated that there were multiple putative targets of miR-34a that may be associated with the proliferation and metastasis of osteosarcoma, including factors in Wnt and Notch signaling pathways.

Conclusion/Significance

The results presented in this study demonstrated that over-expression of miR-34a could inhibit the tumor growth and metastasis of osteosarcoma probably through down regulating c-Met. And there are other putative miR-34a target genes beside c-Met which could potentially be key players in the development of osteosarcoma. Since pulmonary metastases are responsible for mortality of patient carrying osteosarcoma, miR-34a may prove to be a promising gene therapeutic agent. It will be interesting to further investigate the mechanism by which miR-34a functions as a tumor suppressor gene in osteosarcoma.

Systemically administered PEDF against primary and secondary tumours in a clinically relevant osteosarcoma model

Background:

Pigment epithelium-derived factor (PEDF) is an endogenous glycoprotein with a potential role as a therapeutic for osteosarcoma. Animal studies have demonstrated the biological effects of PEDF on osteosarcoma; however, these results are difficult to extrapolate for human use due to the chosen study design and drug delivery methods.

Methods:

In this study we have attempted to replicate the human presentation and treatment of osteosarcoma using a murine orthotopic model of osteosarcoma. The effects of PEDF on osteosarcoma cell lines were evaluated in vitro prior to animal experimentation. Orthotopic tumours were induced by intra-tibial injection of SaOS-2 osteosarcoma cells. Treatment with PEDF was delayed until after the macroscopic appearance of primary tumours. Pigment epithelium-derived factor was administered systemically via an implanted intraperitoneal micro-osmotic pump.

Results:

In vitro, PEDF inhibited proliferation, induced apoptosis and inhibited cell cycling of osteosarcoma cells. Pigment epithelium-derived factor promoted adhesion to Collagen I and inhibited invasion through Collagen I. In vivo, treatment with PEDF caused a reduction in both primary tumour volume and burden of pulmonary metastases. Systemic administration of PEDF did not cause toxic effects on normal tissues.

Conclusion:

Systemically delivered PEDF is effective in suppressing the size of primary and secondary tumours in an orthotopic murine model of osteosarcoma.

The molecular pathogenesis of osteosarcoma: a review

Osteosarcoma is the most common primary malignancy of bone. It arises in bone during periods of rapid growth and primarily affects adolescents and young adults. The 5-year survival rate for osteosarcoma is 60%-70%, with no significant improvements in prognosis since the advent of multiagent chemotherapy. Diagnosis, staging, and surgical management of osteosarcoma remain focused on our anatomical understanding of the disease. As our knowledge of the molecular pathogenesis of osteosarcoma expands, potential therapeutic targets are being identified. A comprehensive understanding of these mechanisms is essential if we are to improve the prognosis of patients with osteosarcoma through tumour-targeted therapies. This paper will outline the pathogenic mechanisms of osteosarcoma oncogenesis and progression and will discuss some of the more frontline translational studies performed to date in search of novel, safer, and more targeted drugs for disease management.