Inactive Wnt/beta-catenin pathway in conventional high-grade osteosarcoma

Cinobufacini from the Skin of Bufo bufo gargarizans Induces Apoptosis, Possibly via Activation of the Wnt/β-Catenin Pathway, in Human Osteosarcoma Cells

Cinobufacini (huachansu) is a traditional Chinese medicine extracted from the skin of Bufo bufo gargarizans, which is used in clinical cancer therapy. The purpose of this study was to investigate the signaling pathways regulating cinobufacini-induced apoptosis in the osteosarcoma cell line, U2OS. We used 3-[4,5-dimethylthiazol- 2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay to evaluate the effects of cinobufacini on cell proliferation in U2OS cells. Changes in cell morphology and apoptosis were detected by TUNEL staining. The expression of apoptosis-related and Wnt/β-catenin pathway proteins was detected by immunofluorescence, RT-PCR, and western blot analysis. Our data indicated that cinobufacini significantly inhibited cell proliferation in a dose- and time-dependent manner. Marked changes in cell morphology and apoptosis rate were clearly observed after cinobufacini treatment. The Wnt/β-catenin pathway was activated, and β-catenin expression was positive in cells after treatment. Further, protein expression of bax was increased, whereas bcl-2 was decreased, resulting in an increased bax/bcl-2 ratio. Moreover, after cinobufacini treatment, the expression of Wnt/β-catenin pathway-related proteins was similar to controls. Taken together, our study indicates that cinobufacini can induce apoptosis in U2OS cells, likely through activating the Wnt/β-catenin pathway.

SPARCL1 suppresses osteosarcoma metastasis and recruits macrophages by activation of canonical WNT/β-catenin signaling through stabilization of the WNT-receptor complex

Metastasis significantly reduces the survival rate of osteosarcoma (OS) patients. Therefore, identification of novel targets remains extremely important to prevent metastasis and treat OS. In this report, we show that SPARCL1 is downregulated in OS by epigenetic methylation of promoter DNA. In vitro and in vivo experiments revealed that SPARCL1 inhibits OS metastasis. We further demonstrated that SPARCL1-activated WNT/β-catenin signaling by physical interaction with various frizzled receptors and lipoprotein receptor-related protein 5/6, leading to WNT–receptor complex stabilization. Activation of WNT/β-catenin signaling contributes to the SPARCL1-mediated inhibitory effects on OS metastasis. Furthermore, we uncovered a paracrine effect of SPARCL1 on macrophage recruitment through activated WNT/β-catenin signaling-mediated secretion of chemokine ligand5 from OS cells. These findings suggest that the targeting of SPARCL1 as a new anti-metastatic strategy for OS patients.

MicroRNA-182 downregulates Wnt/β-catenin signaling, inhibits proliferation, and promotes apoptosis in human osteosarcoma cells by targeting HOXA9

We investigated the mechanisms by which microRNA (miR)-182 promotes apoptosis and inhibits proliferation in human osteosarcoma (OS) cells. Levels of miR-182 and Homeobox A9 (HOXA9) expression were compared between human OS and normal cells. Subjects were divided into OS and normal groups. We analyzed the target relationship of miR-182 and Homeobox A9 (HOXA9). Cells were then assigned into blank, negative control, miR-182 mimics, miR-182 inhibitors, siRNA-HOXA9, or and miR-182 inhibitors + siRNA-HOXA9 groups. Cell function was assayed by CCK-8, flow cytometry and wound healing assay. Additionally, we analyzed OS tumor growth in a xenograft mouse model. Dual-luciferase reporter assays indicated miR-182 directly targets HOXA9. Reverse transcription quantitative PCR and western blotting revealed elevated expression of miR-182, WIF-1, BIM, and Bax, and reduced expression of HOXA9, Wnt, β-catenin, Survivin, Cyclin D1, c-Myc, Mcl-1, Bcl-xL, and Snail in osteosarcoma cells treated with miR-182 mimic or siRNA-HOXA9 as compared to controls. Osteosarcoma cells also exhibited decreased cell proliferation, migration, and tumor growth, and increased apoptosis when treated with miR-182 mimic or siRNA-HOXA9. Correspondingly, in a xenograft mouse model, osteosarcoma tumor volume and growth were increased when cells were treated with miR-182 inhibitor and decreased by miR-182 mimic or siRNA-HOXA9. These results indicate that miR-182 downregulates Wnt/β-catenin signaling, inhibits cell proliferation, and promotes apoptosis in osteosarcoma cells by suppressing HOXA9 expression.

Small molecule inhibitors of the Dishevelled-CXXC5 interaction are new drug candidates for bone anabolic osteoporosis therapy

Bone anabolic agents promoting bone formation and rebuilding damaged bones would ideally overcome the limitations of anti‐resorptive therapy, the current standard prescription for osteoporosis. However, the currently prescribed parathyroid hormone (PTH)‐based anabolic drugs present limitations and adverse effects including osteosarcoma during long‐term use. Also, the antibody‐based anabolic drugs that are currently being developed present the potential limits in clinical application typical of macromolecule drugs. We previously identified that CXXC5 is a negative feedback regulator of the Wnt/β‐catenin pathway via its interaction with Dishevelled (Dvl) and suggested the Dvl–CXXC5 interaction as a potential target for anabolic therapy of osteoporosis. Here, we screened small‐molecule inhibitors of the Dvl–CXXC5 interaction via a newly established in vitro assay system. The screened compounds were found to activate the Wnt/β‐catenin pathway and enhance osteoblast differentiation in primary osteoblasts. The bone anabolic effects of the compounds were shown using ex vivo‐cultured calvaria. Nuclear magnetic resonance (NMR) titration analysis confirmed interaction between Dvl PDZ domain and KY‐02061, a representative of the screened compounds. Oral administration of KY‐02327, one of 55 newly synthesized KY‐02061 analogs, successfully rescued bone loss in the ovariectomized (OVX) mouse model. In conclusion, small‐molecule inhibitors of the Dvl–CXXC5 interaction that block negative feedback regulation of Wnt/β‐catenin signaling are potential candidates for the development of bone anabolic anti‐osteoporosis drugs.

Tetrahydrocurcumin induces mesenchymal-epithelial transition and suppresses angiogenesis by targeting HIF-1α and autophagy in human osteosarcoma

Human osteosarcoma is considered a malignant tumor with poor prognosis that readily metastasizes. Tetrahydrocurcumin (THC) has been reported to have anti-tumor activity in numerous tumors. In addition, hypoxia-inducible factor-1α (HIF-1α) has been demonstrated to be associated with tumor metastasis by regulating epithelial-mesenchymal transition (EMT). However, the role of THC in osteosarcoma remains uncertain. Therefore, this study aimed to elucidate the potential mechanisms. We found that THC significantly reduced the growth of osteosarcoma cells and suppressed migration and invasion, as tested in a nude mouse lung metastasis model. Additionally, the mesenchymal-epithelial transition (MET) process was facilitated by THC. Mechanistically, our study showed that HIF-1α had a pivotal role in the anti-metastatic effect of THC. Importantly, HIF-1α expression was downregulated by THC by inhibiting Akt/mTOR and p38 MAPK pathways. Moreover, THC exhibited a remarkable inhibitory effect on HIF-1α expression and angiogenesis under hypoxic conditions. Furthermore, THC activated autophagy and induced MET and suppressed angiogenesis in a HIF-1α-related manner. Taken together, our findings suggest that THC suppresses metastasis and invasion and this may be associated with HIF-1α and autophagy, which would potentially provide therapeutic strategies for human osteosarcoma.

Effects of SOST Gene Silencing on Proliferation, Apoptosis, Invasion, and Migration of Human Osteosarcoma Cells Through the Wnt/β-Catenin Signaling Pathway

Our study explored the effects of SOST gene silencing on the proliferation, apoptosis, invasion, and migration of human osteosarcoma cells through Wnt/β-catenin signaling pathway. Fresh tissues were obtained from 108 patients with osteosarcoma and 46 patients with osteochondroma. Human osteosarcoma cells (MG-63, U2-OS, HOS, and Saos-2) and normal osteoblast (hFoB1.19) were selected and cultured. Osteosarcoma cells were grouped randomly into the blank group, the scrambled control group, and the SOST-siRNA group. Cell proliferation was determined by MTT assay. Cell cycle and apoptosis were tested by flow cytometry. Transwell and scratch test were performed to determine cell invasion and migration. The qRT-PCR and Western blotting were used to detect mRNA and protein expression level of sclerostin, Wnt1, β-catenin, C-Myc, Cyclin D1, and MMP-7. The activity of caspase-3 was assessed by immunocytochemistry. Alkaline phosphatase (ALP) activity was measured using P-nitrophenylphosphate as a substrate. Low SOST mRNA and sclerostin protein expression levels were observed in osteosarcoma tissues and cells. Compared with the blank and scrambled control groups, sclerostin expression, apoptotic cells, ALP activity, and caspase-3 activity were down-regulated, while the proliferation, invasion, and migration abilities of osteosarcoma cells were evidently enhanced in the SOST-siRNA group. After SOST gene silencing, the mRNA and protein expression levels of Wnt1, β-catenin, C-Myc, Cyclin D1, and MMP-7 in osteosarcoma cells and β-catenin protein expression levels in the nucleus and cytoplasm were significantly elevated. SOST gene silencing promotes the proliferation, invasion, and migration, and inhibits apoptosis of osteosarcoma cells by activating Wnt/β-catenin signaling pathway.

Hypoxia-related microRNA-210 is a diagnostic marker for discriminating osteoblastoma and osteosarcoma

Osteoblastoma is a benign bone tumor that can often be difficult to distinguish from malignant osteosarcoma. Because misdiagnosis can result in unfavorable clinical outcomes, we have investigated microRNAs as potential diagnostic biomarkers for distinguishing between these two tumor types. Next generation RNA sequencing was used as an expression screen to evaluate >2,000 microRNAs present in tissue derived from rare formalin fixed paraffin embedded (FFPE) archival tumor specimens. MicroRNAs displaying the greatest ability to discriminate between these two tumors were validated on an independent tumor set, using qPCR assays. Initial screening by RNA-seq identified four microRNA biomarker candidates. Expression of three miRNAs (miR-451a, miR-144-3p, miR-486-5p) was higher in osteoblastoma, while the miR-210 was elevated in osteosarcoma. Validation of these microRNAs on an independent data set of 22 tumor specimens by qPCR revealed that miR-210 is the most discriminating marker. This microRNA displays low levels of expression across all of the osteoblastoma specimens and robust expression in the majority of the osteosarcoma specimens. Application of these biomarkers to a clinical test case showed that these microRNA biomarkers permit re-classification of a misdiagnosed FFPE tumor sample from osteoblastoma to osteosarcoma. Our findings establish that the hypoxia-related miR-210 is a discriminatory marker that distinguishes between osteoblastoma and osteosarcoma. This discovery provides a complementary molecular approach to support pathological classification of two diagnostically challenging musculoskeletal tumors. Because miR-210 is linked to the cellular hypoxia response, its detection may be linked to well-established pro-angiogenic and metastatic roles of hypoxia in osteosarcomas and other tumor cell types. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1137-1146, 2017.

Silencing Transmembrane Protein 45B (TNEM45B) Inhibits Proliferation, Invasion, and Tumorigenesis in Osteosarcoma Cells

Transmembrane protein 45B (TMEM45B) is a member of the TMEM family of proteins and has been reported to be expressed abnormally in different kinds of human tumors. However, the biological function of TMEM45B in osteosarcoma remains unclear. The objective of this study was to investigate the role of TMEM45B in regulating the biological behavior of osteosarcoma cells. Our results demonstrated that the expression of TMEM45B at both the protein and mRNA levels was dramatically upregulated in human osteosarcoma cell lines. Knockdown of TMEM45B significantly suppressed the proliferation, migration, and invasion of U2OS cells in vitro. Mechanistically, knockdown of TMEM45B sharply downregulated the expression level of β-catenin, cyclin D1, and c-Myc in U2OS cells. Finally, knockdown of TMEM45B attenuated tumor growth in transplanted U2OS-derived tumors in nude mice. Taken together, our results demonstrated that TMEM45B plays an important role in regulating the proliferation, migration, and invasion of osteosarcoma cells and that its effects on proliferation and invasion were mediated partially through the Wnt/β-catenin signaling pathway. These observations support our belief that TMEM45B may serve as an oncogene in the development and progression of osteosarcoma.

Sclerostin expression in skeletal sarcomas

Sclerostin (SOST) is an extracellular Wnt signaling antagonist which negatively regulates bone mass. Despite this, the expression and function of SOST in skeletal tumors remain poorly described. Here, we first describe the immunohistochemical staining pattern of SOST across benign and malignant skeletal tumors with bone or cartilage matrix (n=68 primary tumors). Next, relative SOST expression was compared to markers of Wnt signaling activity and osteogenic differentiation across human osteosarcoma (OS) cell lines (n=7 cell lines examined). Results showed immunohistochemical detection of SOST in most bone-forming tumors (90.2%; 46/51) and all cartilage-forming tumors (100%; 17/17). Among OSs, variable intensity and distribution of SOST expression were observed, which highly correlated with the presence and degree of neoplastic bone. Patchy SOST expression was observed in cartilage-forming tumors, which did not distinguish between benign and malignant tumors or correlate with regional morphologic characteristics. Finally, SOST expression varied widely between OS cell lines, with more than 97-fold variation. Among OS cell lines, SOST expression positively correlated with the marker of osteogenic differentiation alkaline phosphatase and did not correlate well with markers of Wnt/β-catenin signaling activity. In summary, SOST is frequently expressed in skeletal bone- and cartilage-forming tumors. The strong spatial correlation with bone formation and the in vitro expression patterns are in line with the known functions of SOST in nonneoplastic bone, as a feedback inhibitor on osteogenic differentiation. With anti-SOST as a potential therapy for osteoporosis in the near future, its basic biologic and phenotypic consequences in skeletal tumors should not be overlooked.

Mesenchymal Tumors Can Derive from Ng2/Cspg4-Expressing Pericytes with β-Catenin Modulating the Neoplastic Phenotype

The cell of origin for most mesenchymal tumors is unclear. One cell type that contributes to this lineages is the pericyte, a cell expressing Ng2/Cspg4. Using lineage tracing, we demonstrated that bone and soft tissue sarcomas driven by the deletion of the Trp53 tumor suppressor, or desmoid tumors driven by a mutation in Apc, can derive from cells expressing Ng2/Cspg4. Deletion of the Trp53 tumor suppressor gene in these cells resulted in the bone and soft tissue sarcomas that closely resemble human sarcomas, while stabilizing β-catenin in this same cell type caused desmoid tumors. Comparing expression between Ng2/Cspg4-expressing pericytes lacking Trp53 and sarcomas that arose from deletion of Trp53 showed inhibition of β-catenin signaling in the sarcomas. Activation of β-catenin inhibited the formation and growth of sarcomas. Thus, pericytes can be a cell of origin for mesenchymal tumors, and β-catenin dysregulation plays an important role in the neoplastic phenotype.

Overexpression of KH-type splicing regulatory protein regulates proliferation, migration, and implantation ability of osteosarcoma

Osteosarcoma is a common malignant bone tumor in children and adolescents. The current 5-year survival rate is ~60% and that seems to be reaching a plateau. In order to improve treatment outcomes of osteosarcoma, a better understanding of tumorigenesis and underlying molecular mechanisms is required for searching out possible new treatment targets. This study aimed to identify the potential proteins involving the pathogenesis of osteosarcoma using a proteomics approach. Proteins extracted from primary cell culture of osteosarcoma (n=7) and osteoblasts of cancellous bone (n=7) were studied. Using 2-DE based proteomics and LC-MS/MS analysis, we successfully determined seven differentially expressed protein spots. Four upregulated proteins and three downregulated proteins were observed in this study in which KH-type splicing regulatory protein (KSRP) was selected for further exploration. KSRP was significantly upregulated in osteosarcoma cells compared to osteoblasts using western blot assay. In addition, immunohistochemistry demonstrated that KSRP was also highly expressed in osteosarcoma tissue of independent cases from the experimental group. More importantly, KSRP silencing of osteosarcoma cell lines significantly decreased cell proliferation, migration ability, as well as implantation and growth ability in chick chorioallantoic membrane assay. Taken together, these findings demonstrate, that KSRP plays important roles in regulatory controls of osteosarcoma pathogenesis and serves as a potentially therapeutic target of osteosarcoma.

Aberrant activation of Wnt/β-catenin signaling drives proliferation of bone sarcoma cells

Bone sarcomas such as osteosarcoma and chondrosarcoma are frequently refractory to conventional chemotherapy and radiotherapy that exhibit poor prognosis. The Wnt signaling are evolutionarily conserved and implicated in cell proliferation and sarcomagenesis. However, the potential role of the Wnt signaling in bone sarcomas is still unclear. Here we demonstrate aberrant activation of Wnt/β-catenin signaling in bone sarcoma cells, involving an autocrine Wnt signaling loop with upregulation of specific Wnt ligands and receptors. Activation of Wnt/β-catenin signaling with Wnt3a or GSK-3β inhibitor drives the proliferation of bone sarcoma cells, whereas downregulation of activated Wnt signaling with dnTCF4 or siLEF1 suppresses bone sarcoma proliferation and induces cell cycle arrest. Taken together, our findings establish the evidence that aberrant activation of Wnt/β-catenin pathway involving an autocrine Wnt singaling drives the proliferation of bone sarcoma cells, and identify the autocrine activation of the Wnt/β-catenin signaling as a potential novel therapeutic target for bone sarcomas.

Over-expression of Sox4 and β-catenin is associated with a less favorable prognosis of osteosarcoma

The purpose of this study was to examine the association of the expression of Sox4 and β-catenin with the prognosis of osteosarcoma. A total of 108 cases of conventional osteosarcoma were involved in this study and 28 cases of osteochondroma served as controls. The expression of Sox4 and β-catenin was detected by using immunohistochemical staining and Western blotting. The results showed that Sox4 and β-catenin were over-expressed in 67 (62.03%) and 62 (57.41%) of 108 osteosarcoma cases, while in only 3 (10.71%) and 5 (17.86%) of 28 controls, respectively (P<0.05 for all). The expression of Sox4 and β-catenin was associated with the distant metastasis, pathological grade and Enneking stage of patients with osteosarcoma (P<0.05 for all). The mean overall survival time and the 5-year-survival rate in osteosarcoma patients with Sox4 and β-catenin over-expressed were significantly reduced as compared with those in Sox4 and β-catenin low-expression group (P<0.05 for all). Cox multifactor regression analysis revealed that the distant metastasis, Enneking stage, and the expression of Sox4 and β-catenin were independent risk factors of patients with osteosarcoma (P<0.05 for all). The findings indicated that overexpression of Sox4 and β-catenin is associated with a poor prognosis of osteosarcoma.

Genetic factors conferring metastasis in osteosarcoma

Osteosarcoma (OS) is a deadly bone malignancy affecting mostly children and adolescents. OS has outstandingly complex genetic alterations likely due to p53-independent genomic instability. Based on analysis of recent published research we claim existence of various genetic mechanisms of osteosarcomagenesis conferring great variability to different OS properties including metastatic potential. We also propose a model explaining how diverse genetic mechanisms occur and providing a framework for future research. P53-independent preexisting genomic instability, which precedes and frequently causes TP53 genetic alterations, is central in our model. In addition, our analyses reveal a possible cooperation between aberrantly activated HIF-1α and AP-1 genetic pathways in OS metastasis. We also review the involvement of noncoding RNA genes in OS metastasis.

Armadillo Repeat-Containing Protein 8 (ARMC8) Silencing Inhibits Proliferation and Invasion in Osteosarcoma Cells

Armadillo repeat-containing protein 8 (ARMC8) plays an important role in regulating cell migration, proliferation, tissue maintenance, signal transduction, and tumorigenesis. However, the expression pattern and role of ARMC8 in osteosarcoma are still unclear. In this study, our aims were to examine the effects of ARMC8 on osteosarcoma and to explore its underlying mechanism. Our results demonstrated that ARMC8 was overexpressed in osteosarcoma cell lines. Knockdown of ARMC8 significantly inhibited osteosarcoma cell proliferation in vitro and markedly inhibited xenograft tumor growth in vivo. ARMC8 silencing also suppressed the epithelial-mesenchymal transition (EMT) phenotype, as well as inhibited the migration and invasion of osteosarcoma cells. Furthermore, knockdown of ARMC8 obviously inhibited the expression of β-catenin, c-Myc, and cyclin D1 in MG-63 cells. In conclusion, this report demonstrates that ARMC8 silencing inhibits proliferation and invasion of osteosarcoma cells. Therefore, ARMC8 may play an important role in the development and progression of human osteosarcoma and may represent a novel therapeutic target in the treatment of osteosarcoma.

Valproic acid improves second-line regimen of small cell lung carcinoma in preclinical models

With 5-year survival rates below 5%, small cell lung carcinoma (SCLC) has very poor prognosis and requires improved therapies. Despite an excellent overall response to first-line therapy, relapses are frequent and further treatments are disappointing. The goal of the study was to improve second-line therapy of SCLC.

The effect of chemotherapeutic agents was evaluated in cell lines (apoptosis, reactive oxygen species, and RNA and protein expression) and in mouse models (tumour development).

We demonstrate here that valproic acid, a histone deacetylase inhibitor, improves the efficacy of a second-line regimen (vindesine, doxorubicin and cyclophosphamide) in SCLC cells and in mouse models.

Transcriptomic profiling integrating microRNA and mRNA data identifies key signalling pathways in the response of SCLC cells to valproic acid, opening new prospects for improved therapies.

Valproic acid improves second-line regimen of SCLC response in preclinical modelshttp://ow.ly/Rsyd8

Inhibition of oleandrin on the proliferation show and invasion of osteosarcoma cells in vitro by suppressing Wnt/β-catenin signaling pathway

Background

Osteosarcoma (OS) is a high-grade bone sarcoma with early metastasis potential, and the clinical chemotherapy drugs that are currently used for its treatment have some limitations. Recently, several studies have reported the selective antitumor effect of oleandrin on various tumor cells. In this study, we aimed to evaluate the effects and underlying mechanisms of oleandrin on OS cells.

Methods

The effect of oleandrin on the proliferation, morphology, and apoptosis of U2OS and SaOS-2 cells were analyzed in vitro. The activity of the Wnt/β-catenin signaling pathway was determined using a dual luciferase assay. Semi-quantitative RT-PCR and western blot assays were performed to evaluate the mRNA and total protein expression of the downstream target genes. Changes of β-catenin in intracellular localization were also explored using a western blot after separating the nucleus and cytoplasm proteins. The MMP-2 and MMP-9 enzymatic activities were determined using gelatin zymography.

Results

Oleandrin significantly inhibited the proliferation and invasion of OS cells in vitro, and induced their apoptosis. After treatment with oleandrin, the TOP/FOP flash ratio in OS cells was noticeably decreased, which indicated that the Wnt/β-catenin signaling pathway was repressed. The expression of related Wnt target genes and total β-catenin was downregulated, and a reduced nuclear β-catenin level by oleandrin was observed as well. In addition, oleandrin suppressed the activities of MMP-2 and MMP-9.

Conclusions

Oleandrin, in vitro, exerted a strong antitumor effect on human OS cells by suppressing the Wnt/β-catenin signaling pathway, which interfered with the proliferation and invasion of OS cells, as well as induced cells apoptosis. Moreover, the expression and activities of MMP-2 and MMP-9 were downregulated by oleandrin, which contributed to the cells’ lower invasiveness.

Targeted Chemotherapy in Bone and Soft-Tissue Sarcoma

Historically surgical intervention has been the mainstay of therapy for bone and soft-tissue sarcomas, augmented with adjuvant radiation for local control. Although cytotoxic chemotherapy revolutionized the treatment of many sarcomas, classic treatment regimens are fraught with side effects while outcomes have plateaued. However, since the approval of imatinib in 2002, research into targeted chemotherapy has increased exponentially. With targeted therapies comes the potential for decreased side effects and more potent, personalized treatment options. This article reviews the evolution of medical knowledge regarding sarcoma, the basic science of sarcomatogenesis, and the major targets and pathways now being studied.

Enhancer of zeste homolog 2 silencing inhibits tumor growth and lung metastasis in osteosarcoma

The enhancer of zeste homolog 2 (EZH2) methyltransferase is the catalytic subunit of polycomb repressive complex 2 (PRC2), which acts as a transcription repressor via the trimethylation of lysine 27 of histone 3 (H3K27me3). EZH2 has been recognised as an oncogene in several types of tumors; however, its role in osteosarcoma has not been fully elucidated. Herein, we show that EZH2 silencing inhibits tumor growth and lung metastasis in osteosarcoma by facilitating re-expression of the imprinting gene tumor-suppressing STF cDNA 3 (TSSC3). Our previous study showed that TSSC3 acts as a tumor suppressor in osteosarcoma. In this study, we found that EZH2 was abnormally elevated in osteosarcoma, and its overexpression was associated with poor prognosis in osteosarcoma. Silencing of EZH2 resulted in tumor growth inhibition, apoptosis and chemosensitivity enhancement. Moreover, suppression of EZH2 markedly inhibited tumor growth and lung metastasis in vivo. Furthermore, EZH2 knockdown facilitated the re-expression of TSSC3 by reducing H3K27me3 in the promoter region. Cotransfection with siEZH2 and siTSSC3 could partially reverse the ability of siEZH2 alone. We have demonstrated that EZH2 plays a crucial role in tumor growth and distant metastasis in osteosarcoma; its oncogenic role is related to its regulation of the expression of TSSC3.

Bone microenvironment signals in osteosarcoma development

The bone is a complex connective tissue composed of many different cell types such as osteoblasts, osteoclasts, chondrocytes, mesenchymal stem/progenitor cells, hematopoietic cells and endothelial cells, among others. The interaction between them is finely balanced through the processes of bone formation and bone remodeling, which regulates the production and biological activity of many soluble factors and extracellular matrix components needed to maintain the bone homeostasis in terms of cell proliferation, differentiation and apoptosis. Osteosarcoma (OS) emerges in this complex environment as a result of poorly defined oncogenic events arising in osteogenic lineage precursors. Increasing evidence supports that similar to normal development, the bone microenvironment (BME) underlies OS initiation and progression. Here, we recapitulate the physiological processes that regulate bone homeostasis and review the current knowledge about how OS cells and BME communicate and interact, describing how these interactions affect OS cell growth, metastasis, cancer stem cell fate and therapy outcome.

Integrated approaches to miRNAs target definition: time-series analysis in an osteosarcoma differentiative model

Background

microRNAs (miRs) are small non-coding RNAs involved in the fine regulation of several cellular processes by inhibiting their target genes at post-transcriptional level. Osteosarcoma (OS) is a tumor thought to be related to a molecular blockade of the normal process of osteoblast differentiation. The current paper explores temporal transcriptional modifications comparing an osteosarcoma cell line, Saos-2, and clones stably transfected with CD99, a molecule which was found to drive OS cells to terminally differentiate.

Methods

Parental cell line and CD99 transfectants were cultured up to 14 days in differentiating medium. In this setting, OS cells were profiled by gene and miRNA expression arrays. Integration of gene and miRNA profiling was performed by both sequence complementarity and expression correlation. Further enrichment and network analyses were carried out to focus on the modulated pathways and on the interactions between transcriptome and miRNome. To track the temporal transcriptional modification, a PCA analysis with differentiated human MSC was performed.

Results

We identified a strong (about 80 %) gene down-modulation where reversion towards the osteoblast-like phenotype matches significant enrichment in TGFbeta signaling players like AKT1 and SMADs. In parallel, we observed the modulation of several cancer-related microRNAs like miR-34a, miR-26b or miR-378. To decipher their impact on the modified transcriptional program in CD99 cells, we correlated gene and microRNA time-series data miR-34a, in particular, was found to regulate a distinct subnetwork of genes with respect to the rest of the other differentially expressed miRs and it appeared to be the main mediator of several TGFbeta signaling genes at initial and middle phases of differentiation. Integration studies further highlighted the involvement of TGFbeta pathway in the differentiation of OS cells towards osteoblasts and its regulation by microRNAs.

Conclusions

These data underline that the expression of miR-34a and down-modulation of TGFbeta signaling emerge as pivotal events to drive CD99-mediated reversal of malignancy and activation of differentiation in OS cells. Our results describe crucial and specific interacting actors providing and supporting their relevance as potential targets for therapeutic differentiative strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0106-0) contains supplementary material, which is available to authorized users.

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.

Euodia sutchuenensis Dode extract stimulates osteoblast differentiation via Wnt/β-catenin pathway activation

The Wnt/β-catenin pathway has a role in osteoblast differentiation and bone formation. We screened 100 plant extracts and identified an extract from Euodia sutchuenensis Dode (ESD) leaf and young branch as an effective activator of the Wnt/β-catenin pathway. ESD extract increased β-catenin levels and β-catenin nuclear accumulation in murine primary osteoblasts. The ESD extract also increased mRNA levels of osteoblast markers, including RUNX2, BMP2 and COL1A1, and enhanced alkaline phosphatase (ALP) activity in murine primary osteoblasts. Both ESD extract-induced β-catenin increment and ALP activation were abolished by β-catenin knockdown, confirming that the Wnt/β-catenin pathway functions in osteoblast differentiation. ESD extract enhanced terminal osteoblast differentiation as shown by staining with Alizarin Red S and significantly increased murine calvarial bone thickness. This study shows that ESD extract stimulates osteoblast differentiation via the Wnt/β-catenin pathway and enhances murine calvarial bone formation ex vivo.

Alteration of WWOX in human cancer: a clinical view

WWOX gene is located in FRA16D, the highly affected chromosomal fragile site. Its tumor suppressor activity has been proposed on a basis of numerous genomic alterations reported in chromosome 16q23.3-24.1 locus. WWOX is affected in many cancers, showing as high as 80% loss of heterozygosity in breast tumors. Unlike most tumor suppressors impairing of both alleles of WWOX is very rare. Despite cellular and animal models information on a WWOX role in cancer tissue is limited and sometimes confusing. This review summarizes information on WWOX in human tumors.

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.

Whole exome sequencing of a single osteosarcoma case--integrative analysis with whole transcriptome RNA-seq data

BACKGROUND

Osteosarcoma (OS) is a prevalent primary malignant bone tumour with unknown etiology. These highly metastasizing tumours are among the most frequent causes of cancer-related deaths. Thus, there is an urgent need for different markers, and with our study, we were aiming towards finding novel biomarkers for OS.

METHODS

For that, we analysed the whole exome of the tumorous and non-tumour bone tissue from the same patient with OS applying next-generation sequencing. For data analysis, we used several softwares and combined the exome data with RNA-seq data from our previous study.

RESULTS

In the tumour exome, we found wide genomic rearrangements, which should qualify as chromotripsis-we detected almost 3,000 somatic single nucleotide variants (SNVs) and small indels and more than 2,000 copy number variants (CNVs) in different chromosomes. Furthermore, the somatic changes seem to be associated to bone tumours, whereas germline mutations to cancer in general. We confirmed the previous findings that the most significant pathway involved in OS pathogenesis is probably the WNT/β-catenin signalling pathway. Also, the IGF1/IGF2 and IGF1R homodimer signalling and TP53 (including downstream tumour suppressor gene EI24) pathways may have a role. Additionally, the mucin family genes, especially MUC4 and cell cycle controlling gene CDC27 may be considered as potential biomarkers for OS.

CONCLUSIONS

The genes, in which the mutations were detected, may be considered as targets for finding biomarkers for OS. As the study is based on a single case and only DNA and RNA analysis, further confirmative studies are required.

Evaluation of NIN/RPN12 binding protein inhibits proliferation and growth in human renal cancer cells

The targeted delivery of small interfering RNA (siRNA) to specific tumor tissues and tumor cells remains as one of the key challenges in the development of RNA interference as a therapeutic application. The ribosome assembly factor NIN/RPN12 binding protein (NOB1) has been suggested to be essential for processing of the 20S pre-rRNA to the mature 18S rRNA, and is also reported to participate in proteasome biogenesis. However, it is unclear whether NOB1 is involved in tumor cells growth. The aim of this study was to determine whether the suppression of lentivirus mediated NOB1 siRNA inhibits the growth of human clean cell carcinoma (ccRCC) cells, further focused on NOB1 as a possible therapeutic target for renal cell carcinoma treatment. NOB1 deletion that caused significant decline in cell proliferation was observed in both 786-O and ACHN cell lines as investigated by MTT assay. Further, the number and size of the colonies formed were also significantly reduced in the absence of NOB1. Moreover, NOB1 gene knockdown arrested the cell cycle and inhibited cell cycle-related protein expression. The Kaplan-Meier survival curves revealed that low NOB1 expression was associated with poor prognosis in ccRCC patients. Collectively, these results indicate that NOB1 plays an essential role in renal cell cancer cell proliferation, and its gene expression could be a therapeutic target.

Investigation of osteosarcoma genomics and its impact on targeted therapy: an international collaboration to conquer human osteosarcoma

Osteosarcoma is a genetically unstable malignancy that most frequently occurs in children and young adults. The lack of progress in managing this devastating disease in the clinic has prompted international researchers to collaborate to profile key genomic alterations that define osteosarcoma. A team of researchers and clinicians from China, Finland, and the United States investigated human osteosarcoma by integrating transcriptome sequencing (RNA-seq), high-density genome-wide array comparative genomic hybridization (aCGH), fluorescence in situ hybridization (FISH), reverse transcription-polymerase chain reaction (RT-PCR), Sanger sequencing, cell culture, and molecular biological approaches. Systematic analysis of genetic/genomic alterations and further functional studies have led to several important findings, including novel rearrangement hotspots, osteosarcoma-specific LRP1-SNRNP25 and KCNMB4-CCND3 fusion genes, VEGF and Wnt signaling pathway alterations, deletion of the WWOX gene, and amplification of the APEX1 and RUNX2 genes. Importantly, these genetic events associate significantly with pathogenesis, prognosis, progression, and therapeutic activity in osteosarcoma, suggesting their potential impact on improved managements of human osteosarcoma. This international initiative provides opportunities for developing new treatment modalities to conquer osteosarcoma.

Down regulation of Wnt signaling mitigates hypoxia-induced chemoresistance in human osteosarcoma cells

Osteosarcoma (OS) is the most common type of solid bone cancer and remains the second leading cause of cancer-related death for children and young adults. Hypoxia is an element intrinsic to most solid-tumor microenvironments, including that of OS, and is associated with resistance to therapy, poor survival, and a malignant phenotype. Cells respond to hypoxia through alterations in gene expression, mediated most notably through the hypoxia-inducible factor (HIF) class of transcription factors. Here we investigate hypoxia-induced changes in the Wnt/β-catenin signaling pathway, a key signaling cascade involved in OS pathogenesis. We show that hypoxia results in increased expression and signaling activation of HIF proteins in human osteosarcoma cells. Wnt/β-catenin signaling is down-regulated by hypoxia in human OS cells, as demonstrated by decreased active β-catenin protein levels and axin2 mRNA expression (p<0.05). This down-regulation appears to rely on both HIF-independent and HIF-dependent mechanisms, with HIF-1α standing out as an important regulator. Finally, we show that hypoxia results in resistance of human OS cells to doxorubicin-mediated toxicity (6–13 fold increase, p<0.01). These hypoxic OS cells can be sensitized to doxorubicin treatment by further inhibition of the Wnt/β-catenin signaling pathway (p<0.05). These data support the conclusion that Wnt/β-catenin signaling is down-regulated in human OS cells under hypoxia and that this signaling alteration may represent a viable target to combat chemoresistant OS subpopulations in a hypoxic niche.

Notch activation as a driver of osteogenic sarcoma

Osteogenic sarcoma (OS) is a deadly skeletal malignancy whose cause is unknown. We report here a mouse model of OS based on conditional expression of the intracellular domain of Notch1 (NICD). Expression of the NICD in immature osteoblasts was sufficient to drive the formation of bone tumors, including OS, with complete penetrance. These tumors display features of human OS; namely, histopathology, cytogenetic complexity, and metastatic potential. We show that Notch activation combined with loss of p53 synergistically accelerates OS development in mice, although p53-driven OS is not Rbpj dependent, which demonstrates a dual dominance of the Notch oncogene and p53 mutation in the development of OS. Using this model, we also reveal the osteoblasts as the potential sources of OS.

Wnt/β-catenin pathway in bone cancers

The Wnt signaling pathway regulates some of the crucial aspects of cellular processes. The beta-catenin dependent Wnt signaling (Wnt/β-catenin) pathway controls the expression of key developmental genes, and acts as an intracellular signal transducer. The association of Wnt/β-catenin pathway is often reported with different cancers. In this study, we have reviewed the association of Wnt/β-catenin pathway with bone cancers, focusing on carcinogenesis and therapeutic aspects. Wnt/β-catenin pathway is a highly complex and unique signaling pathway, which has ability to regulate gene expression, cell invasion, migration, proliferation, and differentiation for the initiation and progression of bone cancers, especially osteosarcoma. Association of Wnt/β-catenin pathway with chondrosarcoma, Ewing's sarcoma and chondroma is also documented. Recently, targeting Wnt/β-catenin pathway has gained significant interests as a potential therapeutic application for the treatment of bone cancers. Small RNA technology to knockdown aberrant Wnt/β-catenin or inhibition of β-catenin expression by natural component has shown promising effects against bone cancers. Advances in understanding the mechanisms of Wnt signaling and new technologies have facilitated the discovery of agents that can target and regulate Wnt/β-catenin signaling pathway, and these may provide a basement for the innovative therapeutic approaches in the treatment of bone cancers.

The genetic basis for inactivation of Wnt pathway in human osteosarcoma

BACKGROUND

Osteosarcoma is a highly genetically unstable tumor with poor prognosis. We performed microarray-based comparative genomic hybridization (aCGH), transcriptome sequencing (RNA-seq), and pathway analysis to gain a systemic view of the pathway alterations of osteosarcoma.

METHODS

aCGH experiments were carried out on 10 fresh osteosarcoma samples. The output data (Gene Expression Omnibus Series accession number GSE19180) were pooled with published aCGH raw data (GSE9654) to determine recurrent copy number changes. These were analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to identify altered pathways in osteosarcoma. Transcriptome sequencing of six osteosarcomas was performed to detect the expression profile of Wnt signaling pathway genes. Protein expression of WNT1, β-catenin, c-myc, and cyclin D1 in the Wnt pathway was detected by immunohistochemistry (IHC) in an independent group of 46 osteosarcoma samples.

RESULTS

KEGG pathway analysis identified frequent deletions of Wnt and other Wnt signaling pathway genes. At the mRNA level, transcriptome sequencing found reduced levels of mRNA expression of Wnt signaling pathway transcripts. While WNT1 protein expression was detected by IHC in 69.6% (32/46) of the osteosarcomas, no β-catenin protein was detected in the nucleus. β-catenin protein expression was, however, detected in the membrane and cytoplasm of 69.6% (32/46) of the osteosarcomas. c-myc protein expression was detected in only 47.8% (22/46) and cyclin D1 protein expression in 52.2% (24/46) of osteosarcoma samples. Kaplan-Meier survival analysis showed that WNT1-negative patients had a trend towards longer disease free survival than WNT1-positive patients. Interestingly, in WNT1-negative patients, those who were also cyclin D1-negative had significantly longer disease free survival than cyclin D1-positive patients. However, there was no significant association between any of the investigated proteins and overall survival of human osteosarcoma patients.

CONCLUSIONS

Frequent deletions of Wnt and other Wnt signaling pathway genes suggest that the Wnt signaling pathway is genetically inactivated in human osteosarcoma.

Oridonin inhibits the proliferation of human osteosarcoma cells by suppressing Wnt/β-catenin signaling

It has been reported that oridonin (ORI) can inhibit proliferation and induce apoptosis in various types of cancer cell lines. However, the exact mechanism for this function remains unclear. In this study, we investigated the proliferation inhibitory effect of ORI on human osteosarcoma (OS) 143B cells and dissected the possible molecular mechanism(s) underlying this effect. We demonstrated that ORI can inhibit proliferation, induce apoptosis and arrest the cell cycle in 143B cells. Using luciferase reporter assay, we found that the Wnt/β-catenin signaling was inhibited in 143B cells by ORI. Accordingly, the total protein levels and nuclear translocation of β-catenin were reduced by ORI treatment. ORI increased glycogen synthase kinase 3β (GSK3β) activity and upregulated Dickkopf-1 (Dkk-1) expression. We found that Dkk-1 overexpression or β-catenin knockdown can potentiate the proliferation inhibitory effect of ORI in 143B cells, while β-catenin overexpression attenuated this effect. Using the xenograft tumor model of human OS, we demonstrated that ORI effectively inhibited the growth of tumors. Histological examination showed that ORI inhibited cancer cell proliferation, decreased the expression of PNCA and β-catenin. Our findings suggest that ORI can inhibit 143B OS cell proliferation by downregulating Wnt/β-catenin signal transduction, which may be mediated by upregulating the Dkk-1 expression and/or enhancing the function of GSK3β. Therefore, ORI can be potentially used as an effective adjuvant agent for the clinical management of OS.

Gene silencing of NOB1 by lentivirus suppresses growth and migration of human osteosarcoma cells

NIN1/RPN12 binding protein 1 homolog (Saccharomyces cerevisiae) (NOB1) encodes a chaperone protein that joins the 20S proteasome with the 19S regulatory particle in the nucleus and facilitates the biogenesis of the 26S proteasome, which plays a role in maintaining cellular homeostasis by controlling protein degradation. In order to investigate the role of NOB1 in osteosarcoma, NOB1 protein expression in human osteosarcoma cell lines was assessed using western blot analysis. Lentivirus-mediated short hairpin RNA was employed to knock down NOB1, and the effects of NOB1 silencing on cell growth were assessed using MTT, colony formation and cell cycle assays. Cell migration was observed using the Transwell assay. In addition, the expression levels of E-cadherin and β-catenin were examined by western blot analysis. Functional analysis indicated that NOB1-knockdown markedly inhibited cell growth and caused G2/M-phase arrest in human osteosarcoma cells. Furthermore, NOB1 inhibition decreased cell migration and increased E-cadherin and β-catenin expression in U2OS cells. In conclusion, the present study suggested that NOB1 depletion may inhibit osteosarcoma development by increasing E-cadherin and β-catenin expression and, for the first time, indicated the potential of NOB1 as a target in osteosarcoma treatment.

Senescence bypass in mesenchymal stem cells: a potential pathogenesis and implications of pro-senescence therapy in sarcomas

Cellular senescence is a mechanism that limits the lifespan of somatic cells as the results of replicative proliferation and response to stresses, and that prevents undesired oncogenic changes constituting a barrier against immortalization and tumorigenesis. Mesenchymal stem cells (MSCs) reside in a variety of tissues, and participates in tissue maintenance with their multipotent differentiation ability. MSCs are also considered to be as cells of origin for certain type of sarcomas. We reviewed the mechanisms of cellular senescence in MSCs and hypothesized senescence bypass as the potential pathogenesis for sarcoma development, and proposed the possibility of senescence induction therapy for an alternative treatment strategy against sarcomas, especially cells with the resistance to conventional chemo and radiotherapy including sarcoma stem cells.

β-catenin is a valuable marker for differential diagnosis of osteoblastoma and osteosarcoma

Osteoblastoma (OB) and osteosarcoma (OS) are 2 bone tumors that predominantly affect young adults. The clinical management of OS differs significantly from that of OB, and thus, accurate diagnosis of OB and OS is critical in determining appropriate treatment modality. However, in certain cases, OS significantly overlaps with OB in clinical and radiographic characteristics, and therefore, the differential diagnosis of OB and OS can be difficult, especially when biopsy material is insufficient. To date, there have been few reports on markers for differential diagnosis of OB and OS. We have previously shown that the Wnt/β-catenin pathway is inactivated in OS. In this study, we aimed to investigate whether the cellular distribution pattern of β-catenin is a potential marker for the differential diagnosis of OB and OS. Immunohistochemical staining was studied in 17 OB samples (21 biopsies; 17 primary and 4 recurrent) and 37 OS samples with complete follow-up information. Moderate-to-strong nuclear β-catenin staining was found in all OB specimens (17/17). In contrast, positive staining of β-catenin was found in the cytoplasm and/or membrane but not the nucleus in all 32 cases of nonchondroblastic OS (32/32) and the classic OS component in chondroblastic OS (5/5). The only positive nuclear β-catenin staining detected in OS biopsies was in chondroblastic OS cells (5/5). In summary, our results indicate that, in addition to conventional histopathologic evaluation, cellular distribution of β-catenin may be used as a valuable marker in the differential diagnosis of OB and OS. Nuclear β-catenin staining strongly suggests OB, whereas cytoplasmic/membranous staining of β-catenin suggests OS.

An unexpected role for a Wnt-inhibitor: Dickkopf-1 triggers a novel cancer survival mechanism through modulation of aldehyde-dehydrogenase-1 activity

It is widely accepted that canonical Wnt (cWnt) signaling is required for the differentiation of osteoprogenitors into osteoblasts. Furthermore, tumor-derived secretion of the cWnt-antagonist Dickkopf-1 (Dkk-1) is known to cause bone destruction, inhibition of repair and metastasis in many bone malignancies, but its role in osteosarcoma (OS) is still under debate. In this study, we examined the role of Dkk-1in OS by engineering its overexpression in the osteochondral sarcoma line MOS-J. Consistent with the known role of Dkk-1 in osteoblast differentiation, Dkk-1 inhibited osteogenesis by the MOSJ cells themselves and also in surrounding tissue when implanted in vivo. Surprisingly, Dkk-1 also had unexpected effects on MOSJ cells in that it increased proliferation and resistance to metabolic stress in vitro and caused the formation of larger and more destructive tumors than controls upon orthotopic implantation. These effects were attributed in part to upregulation of the stress response enzyme and cancer stem cell marker aldehyde-dehydrogenase-1 (ALDH1). Direct inhibition of ALDH1 reduced viability under stressful culture conditions, whereas pharmacological inhibition of cWnt or overexpression of ALDH1 had a protective effect. Furthermore, we observed that ALDH1 was transcriptionally activated in a c-Jun-dependent manner through a pathway consisting of RhoA, MAP-kinase-kinase-4 and Jun N-terminal Kinase (JNK), indicating that noncanonical planar cell polarity-like Wnt signaling was the mechanism responsible. Together, our results therefore demonstrate that Dkk-1 enhances resistance of OS cells to stress by tipping the balance of Wnt signaling in favor of the non-canonical Jun-mediated Wnt pathways. In turn, this results in transcriptional activation of ALDH1 through Jun-responsive promoter elements. This is the first report linking Dkk-1 to tumor stress resistance, further supporting the targeting of Dkk-1 not only to prevent and treat osteolytic bone lesions but also to reduce numbers of stress-resistant tumor cells.

Hovenia dulcis Thunb extract and its ingredient methyl vanillate activate Wnt/β-catenin pathway and increase bone mass in growing or ovariectomized mice

The Wnt/β-catenin pathway is a potential target for development of anabolic agents to treat osteoporosis because of its role in osteoblast differentiation and bone formation. However, there is no clinically available anti-osteoporosis drug that targets this Wnt/β-catenin pathway. In this study, we screened a library of aqueous extracts of 350 plants and identified Hovenia dulcis Thunb (HDT) extract as a Wnt/β-catenin pathway activator. HDT extract induced osteogenic differentiation of calvarial osteoblasts without cytotoxicity. In addition, HDT extract increased femoral bone mass without inducing significant weight changes in normal mice. In addition, thickness and area of femoral cortical bone were also significantly increased by the HDT extract. Methyl vanillate (MV), one of the ingredients in HDT, also activated the Wnt/β-catenin pathway and induced osteoblast differentiation in vitro. MV rescued trabecular or cortical femoral bone loss in the ovariectomized mice without inducing any significant weight changes or abnormality in liver tissue when administrated orally. Thus, natural HDT extract and its ingredient MV are potential anabolic agents for treating osteoporosis.

Wnt signaling in osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy diagnosed in children and adolescents with a high propensity for local invasion and distant metastasis. Despite current multidisciplinary treatments, there has not been a drastic change in overall prognosis within the last two decades. With current treatments, 60-70 % of patients with localized disease survive. Given a propensity of Wnt signaling to control multiple cellular processes, including proliferation, cell fate determination, and differentiation, it is a critical pathway in OS disease progression. At the same time, this pathway is extremely complex with vast arrays of cross-talk. Even though decades of research have linked the role of Wnt to tumorigenesis, there are still outstanding areas that remain poorly understood and even controversial. The canonical Wnt pathway functions to regulate the levels of the transcriptional co-activator β-catenin, which ultimately controls key developmental gene expressions. Given the central role of this mediator, inhibition of Wnt/β-catenin signaling has been investigated as a potential strategy for cancer control. In OS, several secreted protein families modulate the Wnt/β-catenin signaling, including secreted Frizzled-related proteins (sFRPs), Wnt inhibitory protein (WIF), Dickkopf proteins (DKK-1,2,3), sclerostin, and small molecules. This chapter focuses on our current understanding of Wnt/β-catenin signaling in OS, based on recent in vitro and in vivo data. Wnt activates noncanonical signaling pathways as well that are independent of β-catenin which will be discussed. In addition, stem cells and their association with Wnt/β-catenin are important factors to consider. Ultimately, the multiple canonical and noncanonical Wnt/β-catenin agonists and antagonists need to be further explored for potential targeted therapies.

Indirubin-3'-oxime reverses bone loss in ovariectomized and hindlimb-unloaded mice via activation of the Wnt/β-catenin signaling

Osteoporosis is a major global health issue in elderly people. Because Wnt/β-catenin signaling plays a key role in bone homeostasis, we screened activators of this pathway through cell-based screening, and investigated indirubin-3'-oxime (I3O), one of the positive compounds known to inhibit GSK3β, as a potential anti-osteoporotic agent. Here, we show that I3O activated Wnt/β-catenin signaling via inhibition of the interaction of GSK3β with β-catenin, and induced osteoblast differentiation in vitro and increased calvarial bone thickness ex vivo. Intraperitoneal injection of I3O increased bone mass and improved microarchitecture in normal mice and reversed bone loss in an ovariectomized mouse model of age-related osteoporosis. I3O also increased thickness and area of cortical bone, indicating improved bone strength. Enhanced bone mass and strength correlated with activated Wnt/β-catenin signaling, as shown by histological analyses of both trabecular and cortical bones. I3O also restored mass and density of bone in hindlimb-unloaded mice compared with control, suspended mice, demonstrating bone-restoration effects of I3O in non-aged-related osteoporosis as well. Overall, I3O, a pharmacologically active small molecule, could be a potential therapeutic agent for the treatment and prevention of osteoporosis.

β-Catenin transcriptional activity is minimal in canine osteosarcoma and its targeted inhibition results in minimal changes to cell line behaviour

Canine osteosarcoma (OS) is an aggressive malignancy associated with poor outcomes. Therapeutic improvements are likely to develop from an improved understanding of signalling pathways contributing to OS development and progression. The Wnt signalling pathway is of interest for its role in osteoblast differentiation, its dysregulation in numerous cancer types, and the relative frequency of cytoplasmic accumulation of β-catenin in canine OS. This study aimed to determine the biological impact of inhibiting canonical Wnt signalling in canine OS, by utilizing either β-catenin siRNA or a dominant-negative T-cell factor (TCF) construct. There were no consistent, significant changes in cell line behaviour with either method compared to parental cell lines. Interestingly, β-catenin transcriptional activity was three-fold higher in normal canine primary osteoblasts compared to canine OS cell lines. These results suggest canonical Wnt signalling is minimally active in canine OS and its targeted inhibition is not a relevant therapeutic strategy.

Recurrent chromosome 22 deletions in osteoblastoma affect inhibitors of the Wnt/beta-catenin signaling pathway

Osteoblastoma is a bone forming tumor with histological features highly similar to osteoid osteoma; the discrimination between the tumor types is based on size and growth pattern. The vast majority of osteoblastomas are benign but there is a group of so-called aggressive osteoblastomas that can be diagnostically challenging at the histopathological level. The genetic aberrations required for osteoblastoma development are not known and no genetic difference between conventional and aggressive osteoblastoma has been reported. In order to identify recurrent genomic aberrations of importance for tumor development we applied cytogenetic and/or SNP array analyses on nine conventional and two aggressive osteoblastomas. The conventional osteoblastomas showed few or no acquired genetic aberrations while the aggressive tumors displayed heavily rearranged genomes. In one of the aggressive osteoblastomas, three neighboring regions in chromosome band 22q12 were homozygously deleted. Hemizygous deletions of these regions were found in two additional cases, one aggressive and one conventional. In total, 10 genes were recurrently and homozygously lost in osteoblastoma. Four of them are functionally involved in regulating osteogenesis and/or tumorigenesis. MN1 and NF2 have previously been implicated in the development of leukemia and solid tumors, and ZNRF3 and KREMEN1 are inhibitors of the Wnt/beta-catenin signaling pathway. In line with deletions of the latter two genes, high beta-catenin protein expression has previously been reported in osteoblastoma and aberrations affecting the Wnt/beta-catenin pathway have been found in other bone lesions, including osteoma and osteosarcoma.

Surface proteomic analysis of osteosarcoma identifies EPHA2 as receptor for targeted drug delivery

BACKGROUND

Osteosarcoma (OS) is the most common bone tumour in children and adolescents. Despite aggressive therapy regimens, treatment outcomes are unsatisfactory. Targeted delivery of drugs can provide higher effective doses at the site of the tumour, ultimately improving the efficacy of existing therapy. Identification of suitable receptors for drug targeting is an essential step in the design of targeted therapy for OS.

METHODS

We conducted a comparative analysis of the surface proteome of human OS cells and osteoblasts using cell surface biotinylation combined with nano-liquid chromatography - tandem mass spectrometry-based proteomics to identify surface proteins specifically upregulated on OS cells. This approach generated an extensive data set from which we selected a candidate to study for its suitability as receptor for targeted treatment delivery to OS. First, surface expression of the ephrin type-A receptor 2 (EPHA2) receptor was confirmed using FACS analysis. Ephrin type-A receptor 2 expression in human tumour tissue was tested using immunohistochemistry. Receptor targeting and internalisation studies were conducted to assess intracellular uptake of targeted modalities via EPHA2. Finally, tissue micro arrays containing cores of human OS tissue were stained using immunohistochemistry and EPHA2 staining was correlated to clinical outcome measures.

RESULTS

Using mass spectrometry, a total of 2841 proteins were identified of which 156 were surface proteins significantly upregulated on OS cells compared with human primary osteoblasts. Ephrin type-A receptor 2 was highly upregulated and the most abundant surface protein on OS cells. In addition, EPHA2 was expressed in a vast majority of human OS samples. Ephrin type-A receptor 2 effectively mediates internalisation of targeted adenoviral vectors into OS cells. Patients with EPHA2-positive tumours showed a trend toward inferior overall survival.

CONCLUSION

The results presented here suggest that the EPHA2 receptor can be considered an attractive candidate receptor for targeted delivery of therapeutics to OS.

The prognostic significance of CD44V6, CDH11, and β-catenin expression in patients with osteosarcoma

This study aimed to examine the expression of and the relationship between CD44V6, CDH11, and β-catenin. The expression of these cell adhesion molecules was detected in 90 osteosarcoma and 20 osteochondroma specimens using immunohistochemistry. Associations between these parameters and clinicopathological data were also examined. The expression rates of CD44V6, CDH11, and β-catenin were 25.0% (5/20), 70.0% (14/20), and 20.0% (4/20) in osteochondroma specimens, respectively. Compared to osteochondromas, the proportions of expression of CD44V6 and β-catenin in osteosarcoma specimens increased to 65.6% (59/90) and 60.0% (54/90), respectively. However, the expression rate of CDH11 in osteosarcomas was reduced to 40.0% (36/90). The expression of these markers was significantly associated with metastasis and overall survival (P < 0.05). Survival analysis revealed that patients with increased expression of CD44V6 and β-catenin as well as decreased expression of CDH11 were correlated with a shorter survival time. Multivariate analysis indicated that clinical stage, metastasis status, and the expression of CD44V6, CDH11, and β-catenin were found to be associated with overall survival. Further, the expression of β -catenin and that of CD44V6 were positively correlated with each other. Thus, our results indicated abnormal expression of CD44V6, CDH11, and β-catenin in osteosarcomas and osteochondromas, which may provide important indicators for further research.

IR/IGF1R signaling as potential target for treatment of high-grade osteosarcoma

BACKGROUND

High-grade osteosarcoma is an aggressive tumor most often developing in the long bones of adolescents, with a second peak in the 5th decade of life. Better knowledge on cellular signaling in this tumor may identify new possibilities for targeted treatment.

METHODS

We performed gene set analysis on previously published genome-wide gene expression data of osteosarcoma cell lines (n=19) and pretreatment biopsies (n=84). We characterized overexpression of the insulin-like growth factor receptor (IGF1R) signaling pathways in human osteosarcoma as compared with osteoblasts and with the hypothesized progenitor cells of osteosarcoma - mesenchymal stem cells. This pathway plays a key role in the growth and development of bone. Since most profound differences in mRNA expression were found at and upstream of the receptor of this pathway, we set out to inhibit IR/IGF1R using OSI-906, a dual inhibitor for IR/IGF1R, on four osteosarcoma cell lines. Inhibitory effects of this drug were measured by Western blotting and cell proliferation assays.

RESULTS

OSI-906 had a strong inhibitory effect on proliferation of 3 of 4 osteosarcoma cell lines, with IC₅₀s below 100 nM at 72 hrs of treatment. Phosphorylation of IRS-1, a direct downstream target of IGF1R signaling, was inhibited in the responsive osteosarcoma cell lines.

CONCLUSIONS

This study provides an in vitro rationale for using IR/IGF1R inhibitors in preclinical studies of osteosarcoma.