Current treatment of osteosarcoma

The role of the MTHFR C677T polymorphism in methotrexate-induced toxicity in pediatric osteosarcoma patients

AIM

Osteosarcoma patients receive high doses of methotrexate (MTX). However, pharmacogenetic information remains limited and has mainly been investigated in leukemia so far.

PATIENTS & METHODS

We investigated the link between the MTHFR C677T genotype, toxicity levels (mucositis, MTX plasma level, hematological toxicity and hepatotoxicity) and survival of 48 pediatric osteosarcoma patients.

RESULTS

The TT genotype did not show more toxicity compared with the CC/CT genotype. However, plasma MTX levels were related with mucositis, but not with hematological toxicity, nor hepatotoxicity. Survival rates did not differ between homozygous and non-homozygous patients. Yet, homozygous patients had higher relapse risk.

CONCLUSION

The MTHFR C667T polymorphism is not predictive for toxicity or overall survival, but could be used for relapse risk stratification.

All-Trans Retinoic Acid Prevents Osteosarcoma Metastasis by Inhibiting M2 Polarization of Tumor-Associated Macrophages

M2-polarized tumor-associated macrophages (TAM) play a critical role in cancer invasion and metastasis. Here, we report that M2 macrophages enhanced metastasis of K7M2 WT osteosarcoma cells to the lungs in mice, thus establishing M2 TAMs as a therapeutic target for blocking osteosarcoma metastasis. We found that all-trans retinoic acid (ATRA) inhibited osteosarcoma metastasis via inhibiting the M2 polarization of TAMs. ATRA suppressed IL13- or IL4-induced M2-type macrophages, and then inhibited migration of osteosarcoma cells as promoted by M2-type macrophages in vitro ATRA reduced the number of pulmonary metastatic nodes of osteosarcoma and decreased expression of M2-type macrophages in metastatic nodes both in intravenous injection and orthotopic transplantation models. ATRA's effect was independent of conventional STAT3/6 or C/EBPβ signaling, which regulate M2-like polarization of macrophages. Quantitative genomic and functional analyses revealed that MMP12, a macrophage-secreted elastase, was elevated in IL13-skewed TAM polarization, whereas ATRA treatment downregulated IL13-induced secretion of MMP12. This downregulation correlates with the antimetastasis effect of ATRA. Our results show the role of TAM polarization in osteosarcoma metastasis, identify a therapeutic opportunity for antimetastasis treatment, and indicate ATRA treatment as an approach for preventing osteosarcoma metastasis via M2-type polarization intervention. Cancer Immunol Res; 5(7); 547-59. ©2017 AACR.

Mir-150 Up-Regulates Glut1 and Increases Glycolysis in Osteosarcoma Cells

Objective:

Osteosarcoma (OS) is the most common malignant bone tumor in children and young adults. Many studies have shown that microRNAs play a critical role in proliferation and metastasis with this tumour type. However, whether aberrant expression might contribute to a metabolism switch in osteosarcoma cases is not clearly understood. In this study, we explored expression and function of miR-150 in osteosarcoma cells.

Materials and methods:

Expression of miR-150 was assessed by real-time PCR in cell lines and human patient tissues. Scramble siRNA, miR-150 inhibitor, and miR-150 mimics were transfected into osteosarcoma cells to determine their effects on proliferation rate, glucose uptake and lactate secretion. Finally, the relationship between Glut1 and the miR-150 level was explored by luciferase reporter assay and western blotting.

Result:

miR-150 was consistently decreased in cell lines and osteosarcoma tissues as compared to osteoblast cells and normal bone. Ectopic overexpression of miR-150 inhibited osteosarcoma cell proliferation and suppressed glucose uptake and lactate secretion. Loss of function of miR-150, on the other hand, enhanced osteosarcoma cell proliferation and increased glucose uptake and lactate secretion. Western blot and luciferase reporter assays showed that miR-150 may function by regulating Glut1 expression.

Conclusion:

These data suggest that miR-150 is involved in regulation of glycolysis in osteosarcoma cells by influencing Glut1 expression.

Galangin inhibits human osteosarcoma cells growth by inducing transforming growth factor-β1-dependent osteogenic differentiation

Osteosarcoma is the most common primary malignancy of the musculoskeletal system, and is associated with excessive proliferation and poor differentiation of osteoblasts. Currently, despite the use of traditional chemotherapy and radiotherapy, no satisfactory and effective agent has been developed to treat the disease. Herein, we found that a flavonoid natural product, galangin, could significantly attenuate human osteosarcoma cells proliferation, without causing obvious cell apoptosis. Moreover, galangin enhanced the expression of osteoblast differentiation markers (collagen type I, alkaline phosphatase, osteocalcin and osteopontin) remarkably and elevated the alkaline phosphatase activity in human osteosarcoma cells. And galangin could also attenuated osteosarcoma growth in vivo. These bioactivities of galangin resulted from its selective activation of the transforming growth factor (TGF)-β1/Smad2/3 signaling pathway, which was demonstrated by pathway blocking experiments. These findings suggested that galangin could be a promising agent to treat osteosarcoma. In addition, targeting TGF-β1 to induce osteogenic differentiation might represent a novel therapeutic strategy to treat osteosarcoma with minimal side effects.

What Is New in the miRNA World Regarding Osteosarcoma and Chondrosarcoma?

Despite the availability of multimodal and aggressive therapies, currently patients with skeletal sarcomas, including osteosarcoma and chondrosarcoma, often have a poor prognosis. In recent decades, advances in sequencing technology have revealed the presence of RNAs without coding potential known as non-coding RNAs (ncRNAs), which provides evidence that protein-coding genes account for only a small percentage of the entire genome. This has suggested the influence of ncRNAs during development, apoptosis and cell proliferation. The discovery of microRNAs (miRNAs) in 1993 underscored the importance of these molecules in pathological diseases such as cancer. Increasing interest in this field has allowed researchers to study the role of miRNAs in cancer progression. Regarding skeletal sarcomas, the research surrounding which miRNAs are involved in the tumourigenesis of osteosarcoma and chondrosarcoma has rapidly gained traction, including the identification of which miRNAs act as tumour suppressors and which act as oncogenes. In this review, we will summarize what is new regarding the roles of miRNAs in chondrosarcoma as well as the latest discoveries of identified miRNAs in osteosarcoma.

PLA2G16 promotes osteosarcoma metastasis and drug resistance via the MAPK pathway

The prognosis of metastatic osteosarcoma is dismal and a better understanding of the mechanisms underlying disease progression is essential to improve treatment options and patient outcomes. We previously demonstrated Pla2g16 overexpression in mouse osteosarcoma contributes to metastasis phenotypes and increased expression of PLA2G16 is associated with metastasis and poor prognosis in human tumors. To further examine the mechanisms through which PLA2G16 contributes to human osteosarcoma metastasis and explore the potential of PLA2G16 as a therapeutic target in osteosarcoma, we generated a panel of human osteosarcoma cell lines expressing different levels of PLA2G16. The functional analyses of these cell lines demonstrated high levels of PLA2G16 expression increased osteosarcoma cell migration, invasion, clonogenic survival, and anchorage-independent colony formation. Importantly, this activity was dependent on the phospholipase activity of PLA2G16. Additionally, PLA2G16 overexpression decreased the sensitivity of cells to a panel of chemotherapeutic agents. Analysis of downstream pathways revealed the pro-metastasis functions of PLA2G16 were mediated through the MAPK pathway, as knockdown of PLA2G16 decreased ERK1/2 phosphorylation and pharmacological inhibition of MEK significantly repressed PLA2G16 mediated cell migration and clonogenic survival. Furthermore, PLA2G16 overexpression promoted xenograft tumor growth in vivo, and these tumors exhibit increased ERK1/2 phosphorylation. Lastly, the expression of PLA2G16 is strongly correlated with the increased ERK1/2 phosphorylation in human osteosarcoma samples, and the combined lesions are associated with reduced overall and metastasis-free survival. Collectively, these results demonstrate increased PLA2G16 expression activates the MAPK pathway to enhance osteosarcoma metastasis and may be a novel therapeutic target for these cancers.

Overcoming Therapeutic Resistance of Bone Sarcomas: Overview of the Molecular Mechanisms and Therapeutic Targets for Bone Sarcoma Stem Cells

Bone sarcomas are heterogeneous malignant tumors that exhibit clinical, histological, and molecular heterogeneity. Recent progress in their multimodal treatment has gradually improved patient prognosis; however, drug resistance and distant metastasis remain unresolved clinical problems. Recent investigations have suggested the existence of cancer stem-like cells (CSCs) in bone sarcomas, which represent a subpopulation of tumor cells with high tumor-forming ability. The hallmarks of CSCs include tumor- and metastasis-forming potential and drug resistance, which are responsible for poor prognoses of bone sarcoma patients. Therefore, elucidation of the molecular mechanisms of CSCs and identification of therapeutic targets could contribute to novel treatment strategies for bone sarcomas and improve patient prognosis. This paper provides an overview of the accumulating knowledge on bone sarcoma stem cells and preclinical analyses to overcome their lethal phenotypes, in addition to a discussion of their potential for novel therapeutics for bone sarcomas.

Serum microRNA-17 functions as a prognostic biomarker in osteosarcoma

MicroRNAs (miRNAs/miRs) are a class of small noncoding RNA molecules that have important roles in regulating the expression of target genes associated with the development and progression of cancer. The majority of miRNAs are expressed in a highly tissue- and region-specific manner, and released into the bloodstream as a consequences of different diseases. Furthermore, altered levels of miRNAs have been observed in several diseases, including cancer. In the present study, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) demonstrated that circulating miR-17 levels were significantly upregulated in patients with osteosarcoma (OS) compared with healthy subjects. RT-qPCR also revealed that high levels of circulating miR-17 expression were inversely correlated with phosphatase and tensin homolog expression, which was identified as a target gene of miR-17 in OS tissues. Furthermore, the overall survival of patients with OS was shorter in those with high miR-17 expression compared with moderate and low expression. Taken together, these findings indicate that miR-17 may function as a useful diagnostic and prognosis biomarker or therapeutic target of OS.

Downregulation of microRNA-497 is associated with upregulation of synuclein γ in patients with osteosarcoma

The present study aimed to investigate the effects of microRNA (miRNA/miR)-497 expression levels on the expression levels of synuclein γ (SNCG) in serum samples, as well as osteosarcoma and lung-metastatic tissue samples, from patients with osteosarcoma. Between December 2010 and August 2013, fasting peripheral blood was collected from 36 patients with osteosarcoma for serum separation. In addition, osteosarcoma and lung metastatic tissues were resected from 15 osteosarcoma patients with lung metastasis by surgery. Bioinformatics was employed to predict the amount miRNA that binds to SNCG. Reverse transcription-quantitative polymerase chain reaction was used to determine the expression levels of SNCG and miR-497, and western blotting was performed to determine protein expression levels. It was observed that SNCG mRNA and protein expression levels were significantly upregulated in osteosarcoma tissues (P<0.01). Additionally, SNCG mRNA (P<0.01) and protein (P<0.05) expression levels were significantly upregulated in the blood of patients with osteosarcoma. SNCG mRNA and protein expression levels were also significantly upregulated in lung metastatic tissues (P<0.01). miR-497 was significantly downregulated in all three samples; therefore downregulation of miR-497 may lead to the occurrence, development and metastasis of osteosarcoma through the upregulation of SNCG mRNA. In summary, the upregulation of SNCG in blood, osteosarcoma tissue and lung metastatic tissue samples is associated with the dowregulation of miR-497, suggesting that miR-497 may be a potential marker and therapeutic target for the treatment of osteosarcoma.

Protein phosphatase 2A Cα regulates proliferation, migration, and metastasis of osteosarcoma cells

Osteosarcoma is the most frequent primary bone tumor. Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes, such as cell cycle, growth, apoptosis, and signal transduction. In this study, we examined the expression and function of PP2A Cα in osteosarcoma cells. PP2A Cα expression was expected to be higher in malignant osteosarcoma tissues. PP2A Cα expression level and PP2A activity was higher in malignant osteosarcoma LM8 cells compared with that in primary osteoblasts and in the osteoblast-like cell line MC3T3-E1. Okadaic acid, an inhibitor of PP2A, reduced cell viability and induced apoptosis in LM8 cells. PP2A Cα-knockdown LM8 cells (shPP2A) exhibited less striking filopodial and lamellipodial structures than that in original LM8 cells. Focal adhesion kinase phosphorylation and NF-κB activity decreased in shPP2A-treated cells. Sensitivity to serum deprivation-induced apoptosis increased in shPP2A-treated cells, accompanied by a lower expression level of anti-apoptotic BCL-2 in these cells. Reduction of PP2A Cα resulted in a decrease in the migration ability of LM8 cells in vitro. Reduction in PP2A Cα levels in vivo suppressed proliferation and metastasis in LM8 cells. PP2A Cα expression was also higher in human osteosarcoma MG63 and SaOS-2 cells than that in primary osteoblasts and MC3T3-E1 cells, and reduction in PP2A Cα levels suppressed the cell proliferation rate and migration ability of MG63 cells. These results indicate that PP2A Cα has a critical role in the proliferation and metastasis of osteosarcoma cells; therefore, its inhibition could potentially suppress the malignancy of osteosarcoma cells.

Increased expression of microRNA-148a in osteosarcoma promotes cancer cell growth by targeting PTEN

Osteosarcoma is the most common type of primary malignant bone tumor, and deregulated microRNAs (miRNAs or miRs) in osteosarcoma have attracted great attention. In the present study, through miRNA microarray analysis, it was identified that miR-148a expression was significantly increased in osteosarcoma tissues. Increased miR-148a expression was significantly correlated with tumor progression and prognosis. Furthermore, increased miR-148a expression could promote osteosarcoma growth in vitro and in vivo, and the tumor-promoting effect was due to enhanced activation of the phosphoinositide 3-kinase signaling pathway caused by miR-148a-mediated inhibition of phosphatase and tensin homolog expression. Together, the present results suggest a role for miR-148a in osteosarcoma development and its potential use in prognosis prediction and cancer therapy.

In vitro antitumor activity of the ethyl acetate extract of Potentilla chinensis in osteosarcoma cancer cells

The aim of the current study was to evaluate the anticancer effect of the ethanol extract of Potentilla chinensis, a Chinese medicinal plant. An MTT assay was used to evaluate the cell viability of MG-63 human osteosarcoma cancer cells and fR-2 cells. Furthermore, the effect of the extract on apoptosis induction, cell cycle phase distribution and inhibition of cell migration in the MG63 human osteosarcoma cancer cell line was evaluated. The effect of the extract on cell cycle phase distribution was assessed by flow cytometry using propidium iodide (PI). Phase contrast microscopy detected the morphological changes in MG63 cancer cells following extract treatment. The results of the study demonstrated that the extract was cytotoxic to MG63 cancer cells, while the normal cell line (epithelial cell line) showed lower susceptibility. Phase contrast microscopy showed distinguishing morphological features, such as cell shrinkage and blebbing induced by the extract treatment in osteosarcoma cancer cells. The average proportion of Annexin V-positive cells (total apoptotic cells) significantly increased from 5.6% in the control to 24.2, 38.8 and 55.7% in the 40, 80 and 150 µg/ml groups, respectively. The extract induced early and late apoptosis in the cancer cells. Flow cytometric analysis revealed that the extract induced G0/G1-cell cycle arrest, which also showed significant dose-dependence. The extract induced a significant and concentration-dependent reduction in cell migration. Moreover, DNA fragmentation was also examined by observation of the formation of DNA ladders. It was demonstrated that DNA fragmentation was increased with extract concentration compared with that in the control. Taken together, EEPC may serve as potential therapeutic agent against osteosarcoma, provided that the toxicity profile and in vivo investigations demonstrate that it is safe.

Hypoxia-inducible microRNA-488 regulates apoptosis by targeting Bim in osteosarcoma

BACKGROUND

Osteosarcoma is a malignant bone cancer of which the survival rate is still low. One reason for this low survival rate is drug resistance. In the past, it has been shown that microRNAs may play critical roles in osteosarcoma development and drug resistance. The mechanisms by which osteosarcoma cells acquire this resistance have, however, remained largely unknown. Here, we aimed at assessing the role of microRNA-488 in the acquisition of drug resistance by osteosarcoma cells.

METHODS

Quantitative RT-PCR was used to measure the expression of microRNA-488 in primary osteosarcoma samples and in osteosarcoma-derived cells, whereas microRNA-488 mimics and inhibitors were used to modify its expression in these cells. Luciferase reporter, Western blotting, cell viability, apoptosis and ChIP assays were used to assess the various effects of modified microRNA-488 expression in osteosarcoma-derived cells.

RESULTS

We found that microRNA-488 is over-expressed in primary osteosarcoma tissues and osteosarcoma-derived cells and that hypoxia can induce microRNA-488 expression via binding to the hypoxia response element (HRE) in its promoter. We also found that exogenous over-expression of microRNA-488 promotes the proliferation, reduces the apoptosis and decreases the sensitivity to chemotherapy (doxorubicin) of osteosarcoma cells via direct targeting of the tumor suppressor Bim, which is a mediator of apoptosis. In contrast, we found that transfection of a microRNA-488 inhibitor resulted in an increase in both apoptosis and drug sensitivity, and a decrease in proliferation.

CONCLUSIONS

Our data suggest that miRNA-488 may serve as a predictor of response to chemotherapy and as a therapeutic target in human osteosarcomas.

Comparative proteomics analysis of human osteosarcoma by 2D DIGE with MALDI-TOF/TOF MS

Osteosarcoma (OS) is the most common primary malignant tumor of bone and the third most common cancer in childhood and adolescence. However, controversy concerning the ideal combination of chemotherapy agents ensued throughout the last quarter of the 20th century because of conflicting and often nonrandomized data. Collaborative efforts to increase understanding of the biology of osteosarcoma and the use of preclinical models to test novel protein targets will be critical to identify the path toward improving outcomes for patients. We attempted to identify potential protein markers or therapy targets of osteosarcoma and give a glance at tumorigenesis of osteosarcoma. A sensitive and accurate method was employed in comparative proteomic analysis between benign tumor and osteosarcoma. Tumor tissues obtained by open biopsy before induction chemotherapy were investigated With 2D DIGE and MALDI-TOF/TOF MS, 22 differentially expressed proteins were identified after database searching, including 8 up-regulated and 14 down-regulated proteins. We also validated the expression levels of interesting proteins(have higher Ratios(tumor/normal)) by Western blotting assay. Annotating by bioinformatic tools, we found structural and signal transduction associated proteins were in large percentage among altered level proteins. In particular, some low abundant proteins involving translation and transcription, such as EEF2(Elongation Factor 2), LUM Lumican 23 kDa Protein) and GTF2A2(Transcription Initiation Factor Iia Gamma Chain.), were firstly reported by our study comparing to previous observations. Our findings suggest that these differential proteins may be potential biomarkers for diagnosis or molecules for understanding of osteosarcoma tumorigenesis, coming with biologic, preclinical, and clinical trial efforts being described to improve outcomes for patients.

Methotrexate selectively targets human proinflammatory macrophages through a thymidylate synthase/p53 axis

OBJECTIVES

Methotrexate (MTX) functions as an antiproliferative agent in cancer and an anti-inflammatory drug in rheumatoid arthritis (RA). Although macrophages critically contribute to RA pathology, their response to MTX remains unknown. As a means to identify MTX response markers, we have explored its transcriptional effect on macrophages polarised by GM-CSF (GM-MØ) or M-CSF (M-MØ), which resemble proinflammatory and anti-inflammatory macrophages found in RA and normal joints, respectively.

METHODS

The transcriptomic profile of both human macrophage subtypes exposed to 50 nM of MTX under long-term and short-term schedules were determined using gene expression microarrays, and validated through quantitative real time PCR and ELISA. The molecular pathway involved in macrophage MTX-responsiveness was determined through pharmacological, siRNA-mediated knockdown approaches, metabolomics for polyglutamylated-MTX detection, western blot, and immunofluorescence on RA and normal joints.

RESULTS

MTX exclusively modulated gene expression in proinflammatory GM-MØ, where it influenced the expression of 757 genes and induced CCL20 and LIF at the mRNA and protein levels. Pharmacological and siRNA-mediated approaches indicated that macrophage subset-specific MTX responsiveness correlates with thymidylate synthase (TS) expression, as proinflammatory TS⁺ GM-MØ are susceptible to MTX, whereas anti-inflammatory TS^low/- M-MØ and monocytes are refractory to MTX. Furthermore, p53 activity was found to mediate the TS-dependent MTX-responsiveness of proinflammatory TS⁺ GM-MØ. Importantly, TS and p53 were found to be expressed by CD163⁺/TNFα⁺ GM-CSF-polarised macrophages from RA joints but not from normal synovium.

CONCLUSIONS

Macrophage response to MTX is polarisation-dependent and determined by the TS-p53 axis. CCL20 and LIF constitute novel macrophage markers for MTX responsiveness in vitro.

Let-7d miRNA Shows Both Antioncogenic and Oncogenic Functions in Osteosarcoma-Derived 3AB-OS Cancer Stem Cells

Osteosarcoma (OS), an aggressive highly invasive and metastatic bone-malignancy, shows therapy resistance and recurrence, two features that likely depend on cancer stem cells (CSCs), which hold both self-renewing and malignant potential. So, effective anticancer therapies against OS should specifically target and destroy CSCs. We previously found that the let-7d microRNA was downregulated in the 3AB-OS-CSCs, derived from the human OS-MG63 cells. Here, we aimed to assess whether let-7d modulation affected tumorigenic and stemness properties of these OS-CSCs. We found that let-7d-overexpression reduced cell proliferation by decreasing CCND2 and E2F2 cell-cycle-activators and increasing p21 and p27 CDK-inhibitors. Let-7d also decreased sarcosphere-and-colony forming ability, two features associated with self-renewing, and it reduced the expression of stemness genes, including Oct3/4, Sox2, Nanog, Lin28B, and HMGA2. Moreover, let-7d induced mesenchymal-to-epithelial-transition, as shown by both N-Cadherin-E-cadherin-switch and decrease in vimentin. Surprisingly, such switch was accompanied by enhanced migratory/invasive capacities, with a strong increase in MMP9, CXCR4 and VersicanV1. Let-7d- overexpression also reduced cell sensitivity to apoptosis induced by both serum-starvation and various chemotherapy drugs, concomitant with decrease in caspase-3 and increase in BCL2 expression. Our data suggest that let-7d in 3AB-OS-CSCs could induce plastic-transitions from CSCs-to-non-CSCs and vice-versa. To our knowledge this is the first study to comprehensively examine the expression and functions of let-7d in OS-CSCs. By showing that let-7d has both tumor suppressor and oncogenic functions in this context, our findings suggest that, before prospecting new therapeutic strategies based on let-7d modulation, it is urgent to better define its multiple functions. J. Cell. Physiol. 231: 1832-1841, 2016. © 2015 Wiley Periodicals, Inc.

MicroRNA-154 functions as a tumor suppressor in osteosarcoma by targeting Wnt5a

MicroRNAs (miRNAs) are small non-coding RNAs that are involved in tumor initiation and development by suppressing target gene expression. miRNA-154 has been shown to be important in tumorigenesis in many types of cancers. However, its role in osteosarcoma (OS) remains unknown. In the present study, we focused on the roles and mechanisms of miR‑154 in OS development. The results of quantitative RT‑PCR showed that miR‑154 expression was decreased in primary OS tumor samples and cell lines compared to levels in the matched adjacent normal tissues and human normal osteoblast cells (NHOst). Restoration of expression in U2OS cells inhibited cell proliferation, colony formation, migration and invasion, as well as induced cell cycle arrest at the G1 stage. Bioinformatic prediction suggested that Wnt5a is a target gene of miR‑154. It was further verified that Wnt5a is a target gene of miR‑150 in OS cells using luciferase assay, mRNA and protein expression analysis. Wnt5a was upregulated in OS cell lines and primary tumor samples, and its mRNA expression level was negatively correlated with the miR‑154 level in the OS tissues. Restored expression of Wnt5a weakened miR‑154‑mediated suppression of tumor progression. Taken together, these findings suggest that miR‑154 functions as a tumor suppressor in OS by partially suppressing Wnt5a expression.

JNK pathway in osteosarcoma: pathogenesis and therapeutics

CONTEXT

The c-Jun NH2-terminal kinase (JNK) is a member of the mitogen-activated protein kinase super family. JNK can phosphorylate a number of activator protein-1 components, activating several transcription factors, and thus, JNK signaling pathway is being involved in several carcinogenic mechanisms.

OBJECTIVE

In this study, we have reviewed the recent updates of the association of JNK pathway with osteosarcoma (OS), which is one of the most common and aggressive bone malignancies.

METHODS

In this review, we have explored the databases like PubMed, Google Scholar, MEDLINE, etc., and collected the most relevant papers of JNK signaling pathway involved in the pathogenesis and therapeutics of OS.

RESULTS

Evidence showed that JNK is a master protein kinase that plays an important role in osteoblast proliferation, differentiation and apoptosis. Interesting reports showed that chemical JNK inhibitors reduce OS cell proliferation and metastasis. Many of the components of this pathway have now been identified and the application of JNK inhibitors has been proven to work in vivo in human and in animal models; however, JNK pathway has not been translated into clinical use.

CONCLUSION

Therapeutic interventions of potent and selective inhibitors of JNK might provide promising therapeutic approaches for the treatment of OS, and could improve the survival rate and quality of life of OS patients.

miR-874 suppresses the proliferation and metastasis of osteosarcoma by targeting E2F3

Increasing evidence indicates that microRNAs (miRNAs) play critical roles in osteosarcoma (OS) occurrence and development. MicroRNA-874 (miR-874) has proven to be dysregulated in several human cancers. However, the biological function and underlying molecular mechanism of miR-874 in OS remain unclear. In this study, we aimed to investigate the biological role and potential mechanism of miR-874 in OS. Here, we found that miR-874 expression was significantly decreased in OS cell lines and tissues by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), and its expression was correlated with tumor-node-metastasis (TNM) stage, tumor size, and lymph node metastasis (all P < 0.01). Functional study revealed that overexpression of miR-874 in OS cells could remarkably inhibit proliferation, migration, and invasion and induce cell apoptosis. In addition, E2F transcription factor 3 (E2F3) was confirmed as a target of miR-874 in OS cells. E2F3 mRNA expression was upregulated and was inversely correlated with the level of miR-874 in OS tissues. Importantly, downregulation of E2F3 mimicked the effect of overexpression miR-874 in OS cells, and E2F3 overexpression partially attenuated the tumor-suppressive effects of miR-874 in OS cells. Taken together, these findings suggested that miR-874 might suppress the growth and metastasis of OS cells partially by targeting E2F3.

The Clinical Significance of Initial Pulmonary Micronodules in Young Sarcoma Patients

BACKGROUND

The clinical significance of subcentimeter nodules identified on staging chest computed tomography (CT) for sarcoma remains unknown. Our goal was to evaluate the effect of initial pulmonary nodule size and number on survival rates in young, newly diagnosed sarcoma patients.

METHODS

Medical records were reviewed for all patients ≤50 years of age with primary, high-grade bone or soft tissue sarcoma at our institution over a 10-year period. This population was divided into patients with no nodules (group 1); 1 nodule <5 mm (group 2);>1 nodule <5 mm (group 3); and ≥1 nodule ≥5 mm (group 4). Kaplan-Meier analyses with log rank tests were performed to compare overall and disease-free survival between these 4 groups, as well as between patients with unilateral and bilateral nodules.

RESULTS

There were 74 patients in group 1 (59.2%), 26 in group 2 (21%), 11 in group 3 (9%), and 13 in group 4 (10%). Mean follow-up was 74 (range, 6 to 191 mo) months. Survival was only slightly worse with larger nodules but significantly worse with multiple nodules. In addition, patients with bilateral nodules had a significantly worse prognosis than those with multiple unilateral nodules.

CONCLUSIONS

These data suggest that in young patients with high-grade sarcoma, the number and distribution of subcentimeter pulmonary nodules are an important prognostic factor, whereas nodule size may be less relevant.

CXCR1 knockdown improves the sensitivity of osteosarcoma to cisplatin

Chemotherapy resistance is a major cause of poor prognoses for osteosarcoma patients. This study aimed to determine whether CXCR1 gene knockdown improves the sensitivity of osteosarcomas to chemotherapy. Both CXCR1 expression and cisplatin sensitivity were investigated and compared in two osteosarcoma cell lines. Sensitivity to the chemotherapy drug cisplatin and apoptosis were investigated with or without stimulation via Interleukin-8 (IL-8), which is a ligand of CXCR1. Furthermore, activation of the Akt signaling pathway was determined. Finally, luciferase-labeled CXCR1-knockdown Saos2-lung cells were injected into the tibiae of nude mice that were treated with cisplatin thereafter. We found that CXCR1 expression and cisplatin sensitivity were negatively correlated in osteosarcoma cell lines. IL-8-induced reduction in sensitivity could be blocked by silencing CXCR1, and CXCR1 knockdown suppressed the Akt signaling pathway. Moreover, CXCR1-knockdown tumors were significantly smaller than control tumors, which was consistent with the luciferase intensity results. The expression levels of IL-8, CXCR1 and p-Akt were suppressed in CXCR1-knockdown cells. Taken together, these data indicate that CXCR1 gene knockdown in osteosarcoma cells improved the sensitivity to chemotherapy and that this process might be regulated in part by the IL-8/CXCR1/Akt signaling pathway.

miR-205 suppresses the proliferative and migratory capacity of human osteosarcoma Mg-63 cells by targeting VEGFA

BACKGROUND

Osteosarcoma (OS) is the most common primary bone malignancy in children and young adults. MiR-205 has been reported to be negatively correlated with the proliferation and metastasis of many types of cancer, while its effects on the malignant phenotype of OS are unclear.

METHODS

Using TaqMan RT polymerase chain reaction analysis, we firstly explored the expression of miR-205 in a panel of OS cell lines. As the expression of miR-205 was significantly decreased in these cell lines, we sought to compensate for its loss by transfection of exogenous miR-205 mimic into MG-63 cells. To further understand the role of miR-205 in OS, we investigated the effects of miR-205 on the proliferation, migration, and invasion of MG-63 cells, and further explored the mechanisms that might be involved.

RESULTS

We found that miR-205 was consistently suppressed in OS cells when compared with the normal human osteoblast (NHOst) cell line. Restored expression of miR-205 in the OS (MG-63) cell line significantly inhibited cell proliferation, migration, and invasion. Moreover, bioinformatic prediction suggested that vascular endothelial growth factor A (VEGFA) was the target oncogene for miR-205 in OS cells. Further quantitative RT polymerase chain reaction and Western blot assays identified that overexpression of miR-205 suppressed expression of VEGFA mRNA and protein. Restored expression of VEGFA in MG-63 cells previously treated with miR-205 mimic could partially abolish miR-205-mediated suppression of proliferation and invasion of these cells.

CONCLUSION

Collectively, these data suggest that miR-205 might function as a tumor suppressor in OS by, at least partially, targeting VEGFA.

RNAi-mediated silencing of AQP1 expression inhibited the proliferation, invasion and tumorigenesis of osteosarcoma cells

Aquaporin 1 (AQP1), a member of water channel proteins, functions as a water-selective transporting protein in cell membranes. In recent years, AQP1 has been found to be overexpressed in various tumors. However, the molecular mechanism underlying the biological function of AQP1 in osteosarcoma is still unclear. This study was aimed at elucidating the roles of AQP1 in regulating the biological behavior of osteosarcoma cells. In this study, we found that AQP1 mRNA was elevated in osteosarcoma tissue. High level of AQP1 was associated with poor prognosis in osteosarcoma. Then, we found that knockdown of AQP1 in osteosarcoma cells, U2OS or MG63 cells inhibited cell proliferation and significantly increased cells population in G1 phase. Additionally, suppressing AQP1 expression in osteosarcoma cells dramatically induced cell apoptosis. We also found that down-regulation of AQP1 significantly inhibited cell adhesion and invasion. More importantly, AQP1 knockdown inhibited tumor growth in vivo and prolonged the survival time of nude mice. Gene set enrichment analysis (GSEA) showed that transforming growth factor-β (TGF-β) signaling pathway and focal adhesion genes was correlatively with AQP1 expression. In addition, real time PCR and western blot analysis revealed that expression of TGF-β1/TGF-β2, RhoA and laminin β 2 (LAMB2) was remarkably impaired by AQP1 silencing. In conclusion, AQP1 may be a useful diagnosis and prognosis marker for osteosarcoma. AQP1 knockdown can effectively inhibit cell proliferation, adhesion, invasion and tumorigenesis by targeting TGF-β signaling pathway and focal adhesion genes, which may serve a promising therapeutic strategy for osteosarcoma.

Pericytes in sarcomas of bone

Pericytes are mesenchymal cells that closely enwrap small blood vessels, lying in intimate association with the endothelium. Pericytes have recently gained attention as an important mediator of vascular biology and angiogenesis in cancer. Although better studied in carcinoma, pericytes have known interaction with sarcomas of bone, including Ewing's sarcoma, osteosarcoma, and chondrosarcoma. Best studied is Ewing's sarcoma (ES), which displays a prominent perivascular growth pattern. Signaling pathways of known importance in intratumoral pericytes in ES include Notch, PDGF/PDGFR-β, and VEGF signaling. In summary, pericytes serve important functions in the tumor microenvironment. Improved understanding of pericyte biology may hold significant implications for the development of new therapies in sarcoma.

SDF-1/CXCR4 promotes F5M2 osteosarcoma cell migration by activating the Wnt/β-catenin signaling pathway

Osteosarcoma (OS), the most common primary malignant bone tumor in children and adolescents, lacks an effective therapy. Stromal cell-derived factor (SDF-1) and its receptor, CXCR4, play multiple roles in migration, proliferation, and survival of different tumor cells. This study aimed to investigate whether the functional SDF-1/CXCR4 signaling mediates chemotaxis in F5M2 OS cells as well as the underlying mechanisms. Immunohistochemistry and immunofluorescence microscopy were used. RNA expression was detected by real-time quantitative polymerase chain reaction, and protein expression was examined by Western blotting. Migration assays were carried out in F5M2 cells. The results showed that the expression of CXCR4 and β-catenin mRNA and protein was significantly higher in OS tissues compared to the surrounding non-neoplastic tissues. SDF-1 promoted F5M2 cell migration by activating the AKT and Wnt/β-catenin signaling pathway, which was abrogated by preincubation with AMD3100 and LY294002. In conclusion, SDF-1/CXCR4 axis-promoted F5M2 cell migration was regulated by the Wnt/β-catenin signaling pathway.

PLA2G16 Expression in Human Osteosarcoma Is Associated with Pulmonary Metastasis and Poor Prognosis

Background

Osteosarcoma is the most frequent type of malignant bone tumor in children and adolescents and is associated with a high propensity for lung metastasis. Recent experiments have indicated that PLA2G16 contributes to osteosarcoma progression and metastasis in both mouse and human osteosarcoma cell lines. The aim of this study was to compare the expression of PLA2G16 in non-metastatic and metastatic osteosarcomas to determine whether PLA2G16 expression can serve as a biomarker of osteosarcoma prognosis and metastasis.

Methods

Quantitative real-time PCR was used to examine PLA2G16 mRNA in primary osteosarcoma patients (18 patients without metastases and 17 patients with metastases), and immunohistochemistry (IHC) staining of PLA2G16 was performed on tissue microarrays from 119 osteosarcoma patients. Tumor metastatic behavior and survival of the patients were followed up for a minimum of 36 months and a maximum of 171 months. The prognostic value of PLA2G16 expression was evaluated by the Kaplan–Meier method and a log-rank test. Multivariate Cox regression analysis was used to identify significant independent prognostic factors.

Results

Osteosarcoma patients with metastasis showed a higher expression of PLA2G16 at both the mRNA and protein levels (both at P values< 0.05) than did patients without metastasis. Osteosarcoma patients with positive IHC staining of PLA2G16 expression at primary sites had shorter overall survival and metastasis-free survival (both at P values <0.02). Moreover, multivariate Cox analysis identified PLA2G16 expression as an independent prognostic factor to predict poor overall survival and metastasis-free survival (both P values < 0.03).

Conclusions

This study indicated that PLA2G16 expression is a significant prognostic factor in primary osteosarcoma patients for predicting the development of metastases and poor survival.

Review of microRNA in osteosarcoma and chondrosarcoma

MicroRNAs (miRNAs) are small noncoding RNAs, which play a complex role in posttranscriptional gene expression and can theoretically be used as a diagnostic or prognostic tool, or therapeutic target for neoplasia. Despite advances in the diagnosis and treatment of skeletal sarcomas, including osteosarcoma and chondrosarcoma, much remains unknown regarding their underpinning molecular mechanisms. Given the recent increasing knowledge base of miRNA roles in neoplasia, both as oncogenes and tumor suppressor genes, this review will focus on the available literature regarding the expression profiles and potential roles of miRNA in skeletal sarcomas. Although this is an emerging field, miRNA profiling may be of use in clarifying competing diagnoses of skeletal sarcomas and possibly indicate patient risk of resistance to traditional chemotherapeutic agents. While detecting and targeting miRNAs is currently limited to experimental investigations, miRNA may be utilized for future clinical management of skeletal sarcomas.

Pro-apoptotic and pro-autophagic effects of the Aurora kinase A inhibitor alisertib (MLN8237) on human osteosarcoma U-2 OS and MG-63 cells through the activation of mitochondria-mediated pathway and inhibition of p38 MAPK/PI3K/Akt/mTOR signaling pathway

Osteosarcoma (OS) is the most common malignant bone tumor occurring mostly in children and adolescents between 10 and 20 years of age with poor response to current therapeutics. Alisertib (ALS, MLN8237) is a selective Aurora kinase A inhibitor that displays anticancer effects on several types of cancer. However, the role of ALS in the treatment of OS remains unknown. This study aimed to investigate the effects of ALS on the cell growth, apoptosis, autophagy, and epithelial to mesenchymal transition (EMT) and the underlying mechanisms in two human OS cell lines U-2 OS and MG-63. The results showed that ALS had potent growth inhibitory, pro-apoptotic, pro-autophagic, and EMT inhibitory effects on U-2 OS and MG-63 cells. ALS remarkably induced G₂/M arrest and down-regulated the expression levels of cyclin-dependent kinases 1 and 2 and cyclin B1 in both U-2 OS and MG-63 cells. ALS markedly induced mitochondria-mediated apoptosis with a significant increase in the expression of key pro-apoptotic proteins and a decrease in main anti-apoptotic proteins. Furthermore, ALS promoted autophagic cell death via the inhibition of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways, and activation of 5′-AMP-dependent kinase (AMPK) signaling pathway. Inducers or inhibitors of apoptosis or autophagy simultaneously altered ALS-induced apoptotic and autophagic death in both U-2 OS and MG-63 cells, suggesting a crosstalk between these two primary modes of programmed cell death. Moreover, ALS suppressed EMT-like phenotypes with a marked increase in the expression of E-cadherin but a decrease in N-cadherin in U-2 OS and MG-63 cells. ALS treatment also induced reactive oxygen species (ROS) generation but inhibited the expression levels of sirtuin 1 and nuclear factor-erythroid-2-related factor 2 (Nrf2) in both cell lines. Taken together, these findings show that ALS promotes apoptosis and autophagy but inhibits EMT via PI3K/Akt/mTOR, p38 MAPK, and AMPK signaling pathways with involvement of ROS- and sirtuin 1-associated pathways in U-2 OS and MG-63 cells. ALS is a promising anticancer agent in OS treatment and further studies are needed to confirm its efficacy and safety in OS chemotherapy.

S-adenosylmethionine blocks osteosarcoma cells proliferation and invasion in vitro and tumor metastasis in vivo: therapeutic and diagnostic clinical applications

Osteosarcoma (OS) is an aggressive and highly metastatic form of primary bone cancer affecting young children and adults. Previous studies have shown that hypomethylation of critical genes is driving metastasis. Here, we examine whether hypermethylation treatment can block OS growth and pulmonary metastasis. Human OS cells LM-7 and MG-63 were treated with the ubiquitous methyl donor S-adenosylmethionine (SAM) or its inactive analog S-adenosylhomocystine (SAH) as control. Treatment with SAM resulted in a dose-dependent inhibition of tumor cell proliferation, invasion, cell migration, and cell cycle characteristics. Inoculation of cells treated with 150 μmol/L SAM for 6 days into tibia or via intravenous route into Fox Chase severe combined immune deficient (SCID) mice resulted in the development of significantly smaller skeletal lesions and a marked reduction in pulmonary metastasis as compared to control groups. Epigenome wide association studies (EWAS) showed differential methylation of several genes involved in OS progression and prominent signaling pathways implicated in bone formation, wound healing, and tumor progression in SAM-treated LM-7 cells. Real-time polymerase chain reaction (qPCR) analysis confirmed that SAM treatment blocked the expression of several prometastatic genes and additional genes identified by EWAS analysis. Immunohistochemical analysis of normal human bone and tissue array from OS patients showed significantly high levels of expression of one of the identified gene platelet-derived growth factor alpha (PDGFA). These studies provide a possible mechanism for the role of DNA demethylation in the development and metastasis of OS to provide a rationale for the use of hypermethylation therapy for OS patients and identify new targets for monitoring OS development and progression.

Focal chromosomal copy number aberrations identify CMTM8 and GPR177 as new candidate driver genes in osteosarcoma

Osteosarcoma is an aggressive bone tumor that preferentially develops in adolescents. The tumor is characterized by an abundance of genomic aberrations, which hampers the identification of the driver genes involved in osteosarcoma tumorigenesis. Our study aims to identify these genes by the investigation of focal copy number aberrations (CNAs, <3 Mb). For this purpose, we subjected 26 primary tumors of osteosarcoma patients to high-resolution single nucleotide polymorphism array analyses and identified 139 somatic focal CNAs. Of these, 72 had at least one gene located within or overlapping the focal CNA, with a total of 94 genes. For 84 of these genes, the expression status in 31 osteosarcoma samples was determined by expression microarray analysis. This enabled us to identify the genes of which the over- or underexpression was in more than 35% of cases in accordance to their copy number status (gain or loss). These candidate genes were subsequently validated in an independent set and furthermore corroborated as driver genes by verifying their role in other tumor types. We identified CMTM8 as a new candidate tumor suppressor gene and GPR177 as a new candidate oncogene in osteosarcoma. In osteosarcoma, CMTM8 has been shown to suppress EGFR signaling. In other tumor types, CMTM8 is known to suppress the activity of the oncogenic protein c-Met and GPR177 is known as an overexpressed upstream regulator of the Wnt-pathway. Further studies are needed to determine whether these proteins also exert the latter functions in osteosarcoma tumorigenesis.

Role of osteopontin in osteosarcoma

The primary bone malignancy osteosarcoma (OS) is a painful health burden, of which treatment remains a challenging problem. Identification of specific tumor biomarkers may help to investigate and develop the novel effective therapeutic approaches that have specific molecular target for the treatment of patients with OS. Osteopontin (OPN), a phosphorylated glycoprotein, is involved in many biological processes, such as biomineralization, bone remodeling and immune responses and has recently been reported to be associated with OS pathogenesis. Interestingly, both of the up- and down-regulation of OPN are involved in OS. During OS development, genetic or epigenetic disruption causes reduced expression of RUNX2 and OPN through the up-regulation of notch signaling pathway, leading to the development of OS. On the other hand, during hypoxic condition, upregulation of OPN induces the glucose uptake into hypoxic OS cells which is responsible for the OS cell proliferation and drug resistance. Recent evidences show that targeting OPN might be an important tool in OS therapeutics. This review has focused on the association of abnormal OPN expression with the pathogenesis of OS, the efficiency of OPN as a diagnostic tool for OS and the therapeutic aspects of OS by targeting OPN.

Propofol inhibits proliferation and invasion of osteosarcoma cells by regulation of microRNA-143 expression

Propofol is one of the extensively commonly used intravenous anesthetic agents. Previous studies have indicated that propofol has the ability to influence the biological behavior of several human cancer cells. However, the effect of propofol on osteosarcoma and its related molecular mechanisms are still not clear. Here we found that propofol significantly elevated the expression of miR-143, inhibited cell proliferation and invasion, and promoted apoptosis in osteosarcoma cell line MG63. Propofol also efficiently decreased protein expression of matrix metalloproteinase 13 (MMP-13). Moreover, the overexpression of miR-143 decreased MMP-13 protein level. Finally, the neutralization of miR-143 by anti-miR-143 antibody reversed the effect of propofol on cell proliferation, apoptosis, and invasion and upregulated MMP-13 expression in MG63 cells. Taken together, propofol may have antitumor potential in osteosarcoma, which is partly due to the downregulation of MMP-13 expression by miR-143.

Pirarubicin versus doxorubicin in neoadjuvant/adjuvant chemotherapy for stage IIB limb high-grade osteosarcoma: does the analog matter?

Pirarubicin (THP), a novel anthracycline derivative of doxorubicin (ADM), is effective in treating patients with advanced, relapsed or recurrent high-grade osteosarcoma. But its role in neoadjuvant/adjuvant chemotherapy of osteosarcoma is still not defined. We conducted a retrospective evaluation of THP-containing chemotherapy for osteosarcoma in comparison with ADM-containing chemotherapy to determine differences in efficacy and toxicities between THP- and ADM-containing regimens. From January 2008 to May 2011, 112 stage IIB limb high-grade osteosarcoma patients were treated in our institute. Fifty-four patients received a median 6 cycles of neoadjuvant/adjuvant chemotherapy consisted of THP (pirarubicin), DDP (cisplatin), IFO (ifosfamide) and MTX (methotrexate), while 58 patients received a median 6 cycles of neoadjuvant/adjuvant chemotherapy consisted of ADM (doxorubicin), DDP (cisplatin), IFO (ifosfamide) and MTX (methotrexate). Efficacy and toxicity of the 2 anthracyclines given as combination chemotherapy were assessed in these patients. The limb salvage rate, histologic response rate, 2-year recurrence rate, 2-year metastasis rate, 2-year disease-free survival rate, 2-year overall survival rate, median disease-free survival time (DFS) and median overall survival time (OS) in THP-containing group were similar to that in ADM-containing group. Toxicities were well balanced in two groups. No death related to chemotherapy was observed. Left ventricular ejection fraction was unchanged 1 and 2 years after chemotherapy in two groups. Efficacy and toxicity of THP-containing combination are similar to those of ADM-containing combination in neoadjuvant/adjuvant chemotherapy for stage IIB limb high-grade osteosarcoma.

MicroRNA-101 inhibits the metastasis of osteosarcoma cells by downregulation of EZH2 expression

MicroRNAs (miRNAs) are a class of small non‑coding RNA molecules, which play regulatory roles at the post-transcriptional level by suppressing the translation of protein‑coding genes or inducing mRNA cleavage. Dysregulated expression of miRNAs is involved in multiple types of cancers and plays important roles in regulating various biological processes including metastasis. miR-101 is downregulated in various types of cancer and functions as a suppressor of cell migration and invasion. Meanwhile, enhancer of zeste homolog 2 (EZH2) is associated with the metastatic potential of several aggressive tumors. In the present study, we reported that ectopic overexpression of miR-101 downregulated the expression level of EZH2 and significantly inhibited migration and invasion of osteosarcoma cells. In addition, knockdown of EZH2 by siRNA showed the same effect of miR-101 on migration and invasion. To conclude, these results indicate that miR-101 may act as a tumor suppressor in osteosarcoma, as it has a suppressive role in cell migration and invasion by targeting EZH2.

RPN2 Gene Confers Osteosarcoma Cell Malignant Phenotypes and Determines Clinical Prognosis

Drug resistance and metastasis are lethal characteristics of tumors. We previously demonstrated that silencing of ribophorin II (RPN2), which is part of the N-oligosaccharyl transferase complex, efficiently induced apoptosis and reduced resistance to docetaxel in human breast cancer cells. Here, we report the clinical and functional correlations of RPN2 expression in osteosarcoma. Immunohistochemical evaluation of 35 osteosarcoma patient biopsies revealed that RPN2 was moderately to highly expressed in all specimens, and higher RPN2 mRNA expression was significantly correlated with poor prognosis. To investigate whether lethal phenotypes of osteosarcoma could be reduced by regulating the expression of RPN2, we conducted a study of RNAi-induced RPN2 knockdown in highly metastatic human osteosarcoma cells. The results indicated that RPN2 silencing reduced cell proliferation, sphere formation, cell invasion, and sensitized drug response in vitro. Mice bearing RPN2-silenced highly metastatic osteosarcoma xenografts showed reduced tumor growth and lung metastasis, and survived longer than mice bearing control tumor xenografts. Taken together, our data suggest that RPN2 silencing contributes to regulation of lethal osteosarcoma phenotypes and could be a novel target for RNAi-based therapeutics against osteosarcoma.

MicroRNA-199a-3p and microRNA-34a regulate apoptosis in human osteosarcoma cells

miRNAs (microRNAs) are small non-coding RNAs [18–25 nt (nucleotides)] that regulate gene expression mainly through affecting post-transcriptional modification. Osteosarcoma is an aggressive sarcoma of the bone characterized by a high level of genetic instability and recurrent DNA deletions and amplifications. miRNAs play an important role in cancer cell growth and migration; however, the potential roles of miRNAs in osteosarcoma remain largely uncharacterized. In this paper, miR-199a and miR-34a were discussed the mechanisms of apoptosis using miRNA mimics in human osteosarcoma cells. The results demonstrated that miR-199a and miR-34a could induce the apoptosis of human osteosarcoma cells via p53 signalling pathway.

Hyperoside, a flavonoid compound, inhibits proliferation and stimulates osteogenic differentiation of human osteosarcoma cells

Osteosarcoma, one of the most common malignant bone tumours, is generally considered a differentiation disease caused by genetic and epigenetic disruptions in the terminal differentiation of osteoblasts. Novel therapies based on the non-cytotoxic induction of cell differentiation-responsive pathways could represent a significant advance in treating osteosarcoma; however, effective pharmaceuticals to induce differentiation are lacking. In the present study, we investigated the effect of hyperoside, a flavonoid compound, on the osteoblastic differentiation of U2OS and MG63 osteosarcoma cells in vitro. Our results demonstrated that hyperoside inhibits the proliferation of osteosarcoma cells by inducing G₀/G₁ arrest in the cell cycle, without causing obvious cell death. Cell migration assay further suggested that hyperoside could inhibit the invasion potential of osteosarcoma cells. Additionally, osteopontin and runt-related transcription factor 2 protein levels and osteocalcin activation were upregulated dramatically in hyperoside-treated osteosarcoma cells, suggesting that hyperoside may stimulates osteoblastic differentiation in osteosarcoma cells. This differentiation was accompanied by the activation of transforming growth factor (TGF)-β and bone morphogenetic protein-2, suggesting that the hyperoside-induced differentiation involves the TGF-β signalling pathway. To our knowledge, this study is the first to evaluate the differentiation effect of hyperoside in osteosarcoma cells and assess the possible potential for hyperoside treatment as a future therapeutic approach for osteosarcoma differentiation therapy.

MicroRNA-1 functions as a potential tumor suppressor in osteosarcoma by targeting Med1 and Med31

MicroRNA-1 (miR-1) has been shown to function as a critical gene regulator in multiple types of cancers. However, the role of miR-1 in osteosarcoma has not been totally clarified. In the present study, we investigated the effects of miR-1 on osteosarcoma and the underlying mechanism. We found that miR-1 was downregulated in osteosarcoma tissues and osteosarcoma cell lines. Restoration of miR-1 significantly suppressed osteosarcoma cell proliferation by inhibiting cell cycle progression. Mediator complex subunit 1 (Med1) and 31 (Med31) were validated as targets of miR-1 in osteosarcoma by luciferase reporter assay. Downregulation of Med1 and Med31 suppressed the proliferation of osteosarcoma cells, and overexpression of Med1 and Med31 abrogated the effects of miR-1 on cell proliferation. Furthermore, both miR-1 and knockdown of Med1 or Med31 reduced the expression of met proto-oncogene (MET) and blocked the downstream signaling of MET responding to hepatocyte growth factor (HGF). Taken together, the findings of this study suggest that Med1 and Med31 serve as potential gene therapeutic targets in osteosarcoma and miR-1 may prove to be a promising agent.

Targeting Notch1 signaling pathway positively affects the sensitivity of osteosarcoma to cisplatin by regulating the expression and/or activity of Caspase family

Background

The introduction of cisplatin has improved the long-term survival rate in osteosarcoma patients. However, some patients are intrinsically resistant to cisplatin. This study reported that the activation of Notch1 is positively correlated with cisplatin sensitivity, evidenced by both clinical and in vitro data.

Results

In this study, a total 8 osteosarcoma specimens were enrolled and divided into two groups according to their cancer chemotherapeutic drugs sensitivity examination results. The relationship between Notch1 expression and cisplatin sensitivity of osteosarcoma patients was detected by immunohistochemistry and semi-quantitative analysis. Subsequently, two typical osteosarcoma cell lines, Saos-2 and MG63, were selected to study the changes of cisplatin sensitivity by up-regulating (NICD1 plasmid transfeciton) or decreasing (gamma-secretase complex inhibitor DAPT) the activation state of Notch1 signaling pathway. Our results showed a significant correlation between the expression of Notch1 and cisplatin sensitivity in patient specimens. In vitro, Saos-2 with higher expression of Notch1 had significantly better cisplatin sensitivity than MG63 whose Notch1 level was relatively lower. By targeting regulation in vitro, the cisplatin sensitivity of Saos-2 and MG63 had significantly increased after the activation of Notch1 signaling pathway, and vice versa. Further mechanism investigation revealed that activation/inhibition of Notch1 sensitized/desensitized cisplatin-induced apoptosis, which probably depended on the changes in the activity of Caspase family, including Caspase 3, Caspase 8 and Caspase 9 in these cells.

Conclusions

Our data clearly demonstrated that Notch1 is critical for cisplatin sensitivity in osteosarcoma. It can be used as a molecular marker and regulator for cisplatin sensitivity in osteosarcoma patients.

Human Sarcoma growth is sensitive to small-molecule mediated AXIN stabilization

Sarcomas are mesenchymal tumors showing high molecular heterogeneity, reflected at the histological level by the existence of more than fifty different subtypes. Genetic and epigenetic evidences link aberrant activation of the Wnt signaling to growth and progression of human sarcomas. This phenomenon, mainly accomplished by autocrine loop activity, is sustained by gene amplification, over-expression of Wnt ligands and co-receptors or epigenetic silencing of endogenous Wnt antagonists. We previously showed that pharmacological inhibition of Wnt signaling mediated by Axin stabilization produced in vitro and in vivo antitumor activity in glioblastoma tumors. Here, we report that targeting different sarcoma cell lines with the Wnt inhibitor/Axin stabilizer SEN461 produces a less transformed phenotype, as supported by modulation of anchorage-independent growth in vitro. At the molecular level, SEN461 treatment enhanced the stability of the scaffold protein Axin1, a key negative regulator of the Wnt signaling with tumor suppressor function, resulting in downstream effects coherent with inhibition of canonical Wnt signaling. Genetic phenocopy of small molecule Axin stabilization, through Axin1 over-expression, coherently resulted in strong impairment of soft-agar growth. Importantly, sarcoma growth inhibition through pharmacological Axin stabilization was also observed in a xenograft model in vivo in female CD-1 nude mice. Our findings suggest the usefulness of Wnt inhibitors with Axin stabilization activity as a potentialyl clinical relevant strategy for certain types of sarcomas.

C-reactive protein as a prognostic factor for human osteosarcoma: a meta-analysis and literature review

Background

Osteosarcoma is the most common primary bone cancer in growing adolescents and young adults. The prognostic role of C-reactive protein (CRP) in patients with osteosarcoma is not fully investigated. The purpose of this study is to perform a meta-analysis and literature review on the role of CRP in osteosarcoma and to assess the potential role of serum CRP as a prognostic factor for patients with osteosarcoma.

Methods

A detailed literature search was made in Medline for related research publications written in English. Methodological quality of the studies was also evaluated. The data were extracted and assessed by two reviewers independently. Analysis of pooled data were performed, risk ratio (RR) and corresponding confidence intervals (CIs) were calculated and summarized respectively.

Results

Final analysis of 397 patients from 2 eligible studies was performed. Combined RR of CRP expression suggested that the raised serum CRP level had an adverse prognostic effect on overall survival of patients with osteosarcoma (n = 397 in 2 studies; RR = 0.35; 95% CI: 0.18–0.68; p = 0.002). In the uni- and multivariate survival analysis, response rate and CRP levels were the only independent prognostic variables.

Conclusions

The results of this meta-analysis suggest that CRP expression confers a worse prognosis in patients with osteosarcoma. Large prospective studies are necessary to provide solid data to confirm the prognostic significance of CRP.

Transcription factor Snai1-1 induces osteosarcoma invasion and metastasis by inhibiting E-cadherin expression

Osteosarcoma (OS) is a type of primary malignant bone tumor with a high propensity for local recurrence and distant metastasis. A previous study showed Snail-1 is highly expressed in OS cells. The present study aimed to investigate the association between the transcription factor Snai1 and E-cadherin in OS. SaOS₂ OS cells were transfected either with a plasmid expressing short hairpin RNA (shRNA) specific for the Snai1-1 gene (SaOS₂-shRNA) or a negative control plasmid (SaOS₂-Mock). The expression levels of E-cadherin and Snai1-1 in the transfected and control cells were determined by quantitative polymerase chain reaction and western blot analysis. In addition, the study was extended to evaluate the migratory and invasive properties of the cells through a Transwell experiment. The results show that E-cadherin was expressed at a high level in the SaOS₂-shRNA cells, which were much less migratory and invasive than the control cells. Overexpression of Snai1-1 in OS is associated with tumor progression, possibly through the suppression of E-cadherin expression and induction of the process of epithelial-mesenchymal transition, which contributes to the proceeding invasion and metastasis of OS cells.