Wnt pathway in osteosarcoma, from oncogenic to therapeutic

Wnt signaling: Modulating tumor-associated macrophages and related immunotherapeutic insights

Wnt signaling pathways are highly conserved cascades that mediate multiple biological processes through canonical or noncanonical pathways, from embryonic development to tissue maintenance, but they also contribute to the pathogenesis of numerous cancers. Recent studies have revealed that Wnt signaling pathways critically control the interplay between cancer cells and tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) and potentially impact the efficacy of cancer immunotherapy. In this review, we summarize the evidence that Wnt signaling pathways boost the maturation and infiltration of macrophages for immune surveillance in the steady state but also polarize TAMs toward immunosuppressive M2-like phenotypes for immune escape in the TME. Both cancer cells and TAMs utilize Wnt signaling to transmit signals, and this interaction is crucial for the carcinogenesis and progression of common solid cancers, such as colorectal, gastric, hepatocellular, breast, thyroid, prostate, kidney, and lung cancers; osteosarcoma; and glioma. Specifically, compared with those in solid cancers, Wnt signaling pathways play a distinct role in the pathogenesis of leukemia. Efforts to develop Wnt-based drugs for cancer treatment are still ongoing, and some indeed enhance the anticancer immune response. We believe that the combination of Wnt signaling-based therapy with conventional or immune therapies is a promising therapeutic approach and can facilitate personalized treatment for most cancers.

Osteoblast-derived exosomes promote osteogenic differentiation of osteosarcoma cells via URG4/Wnt signaling pathway

Osteosarcoma is a primary malignant bone tumor. Although surgery and chemotherapy are the main treatment methods, the overall curative effect remains unsatisfactory. Therefore, there is an urgent need to develop new therapeutic options for osteosarcoma. In this study, the effect and molecular mechanism of osteoblast-derived exosomes on the treatment of osteosarcoma were evaluated. Human primary osteoblasts were cultured to observe the effects of osteoblast-derived exosomes on the osteogenic differentiation of osteosarcoma cells both in vitro and in vivo. Alizarin red staining and alkaline phosphatase detection were used to evaluate the degree of osteogenic differentiation, and immunofluorescence and Western blotting were used to detect protein expression. The results showed that osteoblast-derived exosomes effectively inhibited the proliferation of osteosarcoma cells and promoted their mineralization in vitro. The exosomes also significantly inhibited tumor growth and promoted tumor tissue mineralization in vivo. Osteoblast-derived exosomes upregulated the expression of bone sialoprotein, osteonectin, osteopontin, runt-related transcription factor 2, and Wnt inhibitory factor 1, downregulated the expression of cyclin D1, and suppressed the nuclear accumulation of β-catenin and promoted its phosphorylation in vitro and in vivo. However, these effects were significantly reversed by upregulated gene (URG) 4 overexpression. These findings suggest that osteoblast-derived exosomes could activate the osteogenic differentiation process in osteosarcoma cells and promote their differentiation by targeting the URG4/Wnt signaling pathway.

Clinicopathological significance of SOX9 and β-catenin expression in pre-neoadjuvant chemotherapy cases of osteosarcoma: molecular and immunohistochemical study

The molecular pathogenesis of osteosarcoma (OS), the most frequent primary malignant bone tumor of all age groups, is still obscure. Since multidrug chemotherapeutic regimens were introduced in the 1970s, survival rates have been stationary. The Wnt-β-catenin signaling cascade and SOX9 have a significant contribution to skeletal growth, development, and tumorigenesis. In the present work, an attempt was made to examine the role and clinicopathological significance of β-catenin and SOX9 in 46 cases of pre-neoadjuvant chemotherapy OS tissues compared to 10 cases of non-neoplastic bone. The mRNA levels of both markers were assessed by qRT-PCR, and protein levels of β-catenin were analyzed by immunohistochemistry. The results were correlated with different clinicopathological parameters. SOX9 mRNA levels were significantly elevated in OS compared to non-neoplastic bone, and higher levels were significantly associated with the occurrence of fluid-fluid levels (indicating blood-containing cystic spaces) and osteolytic radiological pattern. Although β-catenin mRNA and protein levels were higher in OS compared to non-neoplastic bone, only the protein levels reached statistical significance. Higher β-catenin mRNA levels were significantly associated with tumor size, while higher protein levels were significantly associated with the histologic subtype, mitotic count, and radiological pattern. No significant association was noted with any of the other evaluated parameters. OS showing higher SOX9 mRNA expression and lower β-catenin mRNA and protein expression exhibited longer estimated overall survival times approaching statistical significance. To conclude, while high expression of β-catenin and SOX9 suggests their possible involvement in OS development, their prognostic role may need further research.

Gallic acid mediates tumor-suppressive effects on osteosarcoma through the H19-Wnt/β-catenin regulatory axis

Background

Osteosarcoma (OS) is the most common primary malignancy in bone tissues, and effective therapeutics remain absent in clinical practice. Traditional Chinese medicines (TCM) have been used for thousands of years, which provide great insights into OS management. Gallic acid (GA) is a natural phenolic acid enriched in various foods and herbs. Several pharmacological activities of GA such as anti-oxidation and anti-inflammation have been well-established. However, its biological function in OS remains not fully understood.

Methods

The potential anti-cancer properties of GA were evaluated in 143 ​B, U2OS and MG63 ​cells. Its effects on cell growth, cell cycle, apoptosis and migration were examined in these OS cells. The lncRNA H19 and Wnt/β-catenin signaling were detected by qPCR, luciferase activity and Western blotting assays. The in vivo effect of GA on tumor growth was investigated using an orthotopic mouse model.

Results

In the present study, GA was found to suppress the tumor growth in vitro via inducing cell cycle arrest and apoptosis in OS cells, and inhibit the invasion and metastasis as well. Using the orthotopic animal model, GA was also found to suppress tumorigenesis in vivo. Long noncoding RNA (lncRNA) H19 was demonstrated to be down-regulated by GA, and thus disrupted the canonical Wnt/β-catenin signaling in OS cells. Furthermore, the ectopic expression of H19 rescued the GA-induced suppressive effects on tumor growth and metastasis, and partially reversed the inactivation of Wnt/β-catenin signaling.

Conclusions

Taken together, our results indicated that GA inhibited tumor growth through an H19-mediated Wnt/β-catenin signaling regulatory axis in OS cells.

The translational potential of this article

The information gained from this study provides a novel underlying mechanism of GA mediated anti-OS activity, suggesting that GA may be a promising drug candidate for OS patients.

Zinc oxide nanoparticles inhibit osteosarcoma metastasis by downregulating β-catenin via HIF-1α/BNIP3/LC3B-mediated mitophagy pathway

Osteosarcoma (OS) therapy faces many challenges, especially the poor survival rate once metastasis occurs. Therefore, it is crucial to explore new OS treatment strategies that can efficiently inhibit OS metastasis. Bioactive nanoparticles such as zinc oxide nanoparticles (ZnO NPs) can efficiently inhibit OS growth, however, the effect and mechanisms of them on tumor metastasis are still not clear. In this study, we firstly prepared well-dispersed ZnO NPs and proved that ZnO NPs can inhibit OS metastasis-related malignant behaviors including migration, invasion, and epithelial-mesenchymal transition (EMT). RNA-Seqs found that differentially expressed genes (DEGs) in ZnO NP-treated OS cells were enriched in wingless/integrated (Wnt) and hypoxia-inducible factor-1 (HIF-1) signaling pathway. We further proved that Zn²⁺ released from ZnO NPs induced downregulation of β-catenin expression via HIF-1α/BNIP3/LC3B-mediated mitophagy pathway. ZnO NPs combined with ICG-001, a β-catenin inhibitor, showed a synergistic inhibitory effect on OS lung metastasis and a longer survival time. In addition, tissue microarray (TMA) of OS patients also detected much higher β-catenin expression which indicated the role of β-catenin in OS development. In summary, our current study not only proved that ZnO NPs can inhibit OS metastasis by degrading β-catenin in HIF-1α/BNIP3/LC3B-mediated mitophagy pathway, but also provided a far-reaching potential of ZnO NPs in clinical OS treatment with metastasis.

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Zn²⁺ released from bioactive ZnO NPs trigger OS metastasis inhibition.

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ZnO NPs inhibit OS metastasis through degrading β-catenin expression via HIF-1α/BNIP3/LC3B-mediated mitophagy pathway.

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Tissue microarray of OS patients detected higher β-catenin expression which confirmed the potential of ZnO NPs in clinical.

Targeting Signaling Pathway by Curcumin in Osteosarcoma

The most prevalent primary bone malignancy among children and adolescents is osteosarcoma. The high mortality rate of osteosarcoma is due to lung metastasis. Despite the development of multi-agent chemotherapy and surgical resection, patients with osteosarcoma have a high metastasis rate and poor prognosis. Thus, it is necessary to identify novel therapeutic agents to improve the 5-year survival rate of these patients. Curcumin, a phytochemical compound derived from Curcuma longa, has been employed in treating several types of cancers through various mechanisms. Also, in vitro studies have demonstrated that curcumin could inhibit cell proliferation and induce apoptosis in osteosarcoma cells. Development in identifying signaling pathways involved in the pathogenesis of osteosarcoma has provided insight into finding new therapeutic targets for the treatment of this cancer. Targeting MAPK/ERK, PI3k/AKT, Wnt/β-catenin, Notch, and MircoRNA by curcumin has been evaluated to improve outcomes in patients with osteosarcoma. Although curcumin is a potent anti-cancer compound, it has rarely been studied in clinical settings due to its congenital properties such as hydrophobicity and poor bioavailability. In this review, we recapitulate and describe the effect of curcumin in regulating signaling pathways involved in osteosarcoma.

Wnt Signaling in the Development of Bone Metastasis

Wnt signaling occurs through evolutionarily conserved pathways that affect cellular proliferation and fate decisions during development and tissue maintenance. Alterations in these highly regulated pathways, however, play pivotal roles in various malignancies, promoting cancer initiation, growth and metastasis and the development of drug resistance. The ability of cancer cells to metastasize is the primary cause of cancer mortality. Bone is one of the most frequent sites of metastases that generally arise from breast, prostate, lung, melanoma or kidney cancer. Upon their arrival to the bone, cancer cells can enter a long-term dormancy period, from which they can be reactivated, but can rarely be cured. The activation of Wnt signaling during the bone metastasis process was found to enhance proliferation, induce the epithelial-to-mesenchymal transition, promote the modulation of the extracellular matrix, enhance angiogenesis and immune tolerance and metastasize and thrive in the bone. Due to the complexity of Wnt pathways and of the landscape of this mineralized tissue, Wnt function during metastatic progression within bone is not yet fully understood. Therefore, we believe that a better understanding of these pathways and their roles in the development of bone metastasis could improve our understanding of the disease and may constitute fertile ground for potential therapeutics.

Rapamycin-induced autophagy in osteosarcoma cells is mediated via the biglycan/Wnt/β-catenin signaling axis

Biglycan is a class I secreted small leucine-rich proteoglycan (SLRP), which regulates signaling pathways connected to bone pathologies. Autophagy is a vital catabolic process with a dual role in cancer progression. Here, we show that biglycan inhibits autophagy in two osteosarcoma cell lines (P ≤ 0.001), while rapamycin-induced autophagy decreases biglycan expression in MG63 osteosarcoma cells and abrogates the biglycan-induced cell growth increase (P ≤ 0.001). Rapamycin also inhibits β-catenin translocation to the nucleus, inhibiting the Wnt pathway (P ≤ 0.001) and reducing biglycan's colocalization with the Wnt coreceptor LRP6 (P ≤ 0.05). Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug doxorubicin in MG63 OS cells through an autophagy-dependent manner (P ≤ 0.05). Cotreatment of these cells with rapamycin and doxorubicin enhances cells response to doxorubicin by decreasing biglycan (P ≤ 0.001) and β-catenin (P ≤ 0.05) expression. Biglycan deficiency leads to increased caspase-3 activation (P ≤ 0.05), suggesting increased apoptosis of biglycan-deficient cells treated with doxorubicin. Computational models of LRP6 and biglycan complexes suggest that biglycan changes the receptor's ability to interact with other signaling molecules by affecting the interdomain bending angles in the receptor structure. Biglycan binding to LRP6 activates the Wnt pathway and β-catenin nuclear translocation by disrupting β-catenin degradation complex (P ≤ 0.01 and P ≤ 0.05). Interestingly, this mechanism is not followed in moderately differentiated, biglycan-nonexpressing U-2OS OS cells. To sum up, biglycan exhibits protective effects against the doxorubicin in MG63 OS cells by activating the Wnt signaling pathway and inhibiting autophagy.

Sesamol inhibits proliferation, migration and invasion of triple negative breast cancer via inactivating Wnt/β-catenin signaling

Triple negative breast cancer (TNBC), a particularly aggressive breast cancer subtype without estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor 2 (HER2) expression, possesses highly invasive capacity, uncontrolled proliferative phenotype and poor clinical prognosis. Sesamol enriched in sesame seeds has been widely reported as a metabolic modulator due to its anti-aging, anti-hepatotoxic and cardio-protective properties. In this study, we found that sesamol significantly inhibited proliferation, migration and invasion of TNBC cells via attenuating PCNA, CyclinD1 expression and reversion of epithelial-mesenchymal transition (EMT) characterized by increased epithelial marker E-cadherin and decreased mesenchymal marker N-cadherin, Vimentin, Snail expression. Moreover, sesamol inactivated Wnt/β-catenin signaling and Wnt agonist 1 AMBMP application reversed the inhibition of proliferation, migration and invasion of TNBC by sesamol administration. Subsequently, our data showed that sesamol induced Wnt inhibitory factor 1 (WIF1), an endogenous inhibitor of Wnt/β-catenin pathway, expression and WIF1 artificial knockdown abrogated the inactivation of Wnt/β-catenin signaling by sesamol exposure in TNBC cells. And we found that promoter region de-methylation was responsible for WIF1 up-regulation by sesamol administration. Finally, with the xenograft assay using nude mice, we also found that sesamol inhibited proliferation and metastasis of TNBC via WIF1-induced inactivation of Wnt/β-catenin signaling in vivo. Collectively, these data added novel understandings and evidences to the anti-cancer properties of sesamol.

The Role of Sclerostin in Bone Diseases

Sclerostin has been identified as an important regulator of bone homeostasis through inhibition of the canonical Wnt-signaling pathway, and it is involved in the pathogenesis of many different skeletal diseases. Many studies have been published in the last few years regarding sclerostin's origin, regulation, and mechanism of action. The ongoing research emphasizes the potential therapeutic implications of sclerostin in many pathological conditions with or without skeletal involvement. Antisclerostin antibodies have recently been approved for the treatment of osteoporosis, and several animal studies and clinical trials are currently under way to evaluate the effectiveness of antisclerostin antibodies in the treatment of other than osteoporosis skeletal disorders and cancer with promising results. Understanding the exact role of sclerostin may lead to new therapeutic approaches for the treatment of skeletal disorders.

Schisandrin B suppresses osteosarcoma lung metastasis in vivo by inhibiting the activation of the Wnt/β‑catenin and PI3K/Akt signaling pathways

Osteosarcoma (OS) is the most common malignant bone tumor worldwide and is associated with a poor prognosis, often being accompanied by lung metastasis at an early stage. At present, there are several side-effects associated with the OS clinical treatment of OS, with the treatment effects often being unsatisfactory. Thus, there is an urgent need for the development of safe and effective novel drugs for the treatment of OS. Schisandrin B (Sch B) has been previously demonstrated to exhibit antitumor properties. The present study was focused on the effects of Sch B on OS cells (143B, MG63, Saos2 and U2OS) in vitro and in vivo, and also on its possible antitumor mechanisms. In cell experiments, it was revealed that Sch B inhibited OS cell proliferation, migration and invasion, and increased OS cell apoptosis. As regards its biosafety, no notable effects of Sch B on the vitality of normal cells were observed. Mechanistically, it was demonstrated that Sch B blocked OS cell proliferation in the G₁ phase. Subsequently, by using established animal models, it was revealed that Sch B significantly inhibited OS growth and lung metastasis in vivo. In summary, the results of the present study revealed that Sch B inhibited OS cell proliferation, migration and invasion, and promoted apoptosis via the inhibition of the Wnt/β-catenin and PI3K/Akt signaling pathways, without causing any noticeable toxic effects on healthy cells at the therapeutic concentrations used. These findings suggest that Sch B has potential for use as a novel agent for the clinical treatment of OS.

Potential of natural products in osteosarcoma treatment: Focus on molecular mechanisms

Osteosarcoma is the most frequent type of bone cancer found in children and adolescents, and commonly arises in the metaphyseal region of tubular long bones. Standard therapeutic approaches, such as surgery, chemotherapy, and radiation therapy, are used in the management of osteosarcoma. In recent years, the mortality rate of osteosarcoma has decreased due to advances in treatment methods. Today, the scientific community is investigating the use of different naturally derived active principles against various types of cancer. Natural bioactive compounds can function against cancer cells in two ways. Firstly they can act as classical cytotoxic compounds by non-specifically affecting macromolecules, such as DNA, enzymes, and microtubules, which are also expressed in normal proliferating cells, but to a greater extent by cancer cells. Secondly, they can act against oncogenic signal transduction pathways, many of which are activated in cancer cells. Some bioactive plant-derived agents are gaining increasing attention because of their anti-cancer properties. Moreover, some naturally-derived compounds can significantly promote the effectiveness of standard chemotherapy drugs, and in certain cases are able to ameliorate drug-induced adverse effects caused by chemotherapy. In the present review we summarize the effects of various naturally-occurring bioactive compounds against osteosarcoma.

Osteosarcoma mechanobiology and therapeutic targets

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

Niclosamide and Pyrvinium Are Both Potential Therapeutics for Osteosarcoma, Inhibiting Wnt-Axin2-Snail Cascade

Simple Summary

Epithelial–mesenchymal transition (EMT) regulated by Wnt signaling is known as a key mechanism of cancer progression. Although evidence has suggested that the oncogenic Wnt signaling pathway and EMT program are important in the progression of osteosarcoma, there is no known therapeutic drug targeting EMT for osteosarcoma. We investigated whether Axin2, an important EMT target, could be a suitable molecular target and biomarker for osteosarcoma. Furthermore, we showed that both niclosamide and pyrvinium target Axin2, and effectively induce EMT reversion in osteosarcoma cell lines. Our findings suggest an effective biomarker and potential EMT therapeutics for osteosarcoma patients.

Abstract

Osteosarcoma, the most common primary bone malignancy, is typically related to growth spurts during adolescence. Prognosis is very poor for patients with metastatic or recurrent osteosarcoma, with survival rates of only 20–30%. Epithelial–mesenchymal transition (EMT) is a cellular mechanism that contributes to the invasion and metastasis of cancer cells, and Wnt signaling activates the EMT program by stabilizing Snail and β-catenin in tandem. Although the Wnt/Snail axis is known to play significant roles in the progression of osteosarcoma, and the anthelmintic agents, niclosamide and pyrvinium, have been studied as inhibitors of the Wnt pathway, their therapeutic effects and regulatory mechanisms in osteosarcoma remain unidentified. In this study, we show that both niclosamide and pyrvinium target Axin2, resulting in the suppression of EMT by the inhibition of the Wnt/Snail axis in osteosarcoma cells. Axin2 and Snail are abundant in patient samples and cell lines of osteosarcoma. The treatment of niclosamide and pyrvinium inhibits the migration of osteosarcoma cells at nanomolar concentrations. These results suggest that Axin2 and Snail are candidate therapeutic targets in osteosarcoma, and that anthelminthic agents, niclosamide and pyrvinium, may be effective for osteosarcoma patients.

Investigation of anticancer activities of STA-9090 (ganetespib) as a second generation HSP90 inhibitor in Saos-2 osteosarcoma cells

Osteosarcoma is common childhood tumour type of the bone. Chemotherapy is the most important step in treatment of osteosarcoma. Despite advanced diagnosis methods and target specific cancer therapeutics, osteosarcoma has still a high mortality rate and a tendency to metastasize. Therefore, new therapeutic strategies are evaluated in osteosarcoma treatment in pre-clinical and clinical studies. In the last ten years, heat shock protein 90 (HSP90) has been important biological target to design target specific cancer drugs. HSP90 play vital roles in proper folding, stabilization and maintenance of oncogenic client proteins in tumorigenesis. Therefore, inhibition of HSP90 has been significant therapeutic aspects in cancer drug design. STA-9090 (ganetespib) is a second generation small molecule HSP90 inhibitor which blocks tumurogenesis in cancer cells. STA-9090 inhibited ATP hydrolysis and protein folding process of HSP90. In this study, STA-9090 decreased Saos-2 cell proliferation and IC₅₀ dose of STA-9090 was found out as 18.71 µM and 10.25 µM at 24 h and 48 h, respectively. STA-9090 inhibited HSP90 ATPase function and disrupted oncogenic client protein folding activity. Also, STA-9090 decreased protein level of the HSP90 in osteosarcoma cells. Expression analysis of osteosarcoma and bone metabolism related genes was performed by RT² Profiler PCR Array. This study has found the down-regulation of the expression levels of oncogenic genes: DKK1, TWIST1, WNT10B, WNT3A, RANK, RANKL, PTH, FGFR1, FGFR2, LTBP2, IL6, TGFβ1, MMP2 and SPARC genes, in STA-9090 treated Saso-2 cells. Furthermore, expression levels of osteosarcoma related genes, OPG, ERα, ERβ, IL15, BMP2 and BMP7, were found to have increased significantly. Biological activities of STA-9090 on Saos-2 cell line show its potential as a target specific drug to inhibit osteosarcoma and its metastasis.

Mechanisms of Resistance to Conventional Therapies for Osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor, mainly occurring in children and adolescents. Current standard therapy includes tumor resection associated with multidrug chemotherapy. However, patient survival has not evolved for the past decades. Since the 1970s, the 5-year survival rate is around 75% for patients with localized OS but dramatically drops to 20% for bad responders to chemotherapy or patients with metastases. Resistance is one of the biological processes at the origin of therapeutic failure. Therefore, it is necessary to better understand and decipher molecular mechanisms of resistance to conventional chemotherapy in order to develop new strategies and to adapt treatments for patients, thus improving the survival rate. This review will describe most of the molecular mechanisms involved in OS chemoresistance, such as a decrease in intracellular accumulation of drugs, inactivation of drugs, improved DNA repair, modulations of signaling pathways, resistance linked to autophagy, disruption in genes expression linked to the cell cycle, or even implication of the micro-environment. We will also give an overview of potential therapeutic strategies to circumvent resistance development.

Direct conversion of osteosarcoma to adipocytes by targeting TNIK

Osteosarcoma (OS) is an aggressive mesenchymal tumor for which no molecularly targeted therapies are available. We have previously identified TRAF2- and NCK-interacting protein kinase (TNIK) as an essential factor for the transactivation of Wnt signal target genes and shown that its inhibition leads to eradication of colorectal cancer stem cells. The involvement of Wnt signaling in the pathogenesis of OS has been implicated. The aim of the present study was to examine the potential of TNIK as a therapeutic target in OS. RNA interference or pharmacological inhibition of TNIK suppressed the proliferation of OS cells. Transcriptome analysis suggested that a small-molecule inhibitor of TNIK upregulated the expression of genes involved in OS cell metabolism and downregulated transcription factors essential for maintaining the stem cell phenotype. Metabolome analysis revealed that this TNIK inhibitor redirected the metabolic network from carbon flux toward lipid accumulation in OS cells. Using in vitro and in vivo OS models, we confirmed that TNIK inhibition abrogated the OS stem cell phenotype, simultaneously driving conversion of OS cells to adipocyte-like cells through induction of PPARγ. In relation to potential therapeutic targeting in clinical practice, TNIK was confirmed to be in an active state in OS cell lines and clinical specimens. From these findings, we conclude that TNIK is applicable as a potential target for treatment of OS, affecting cell fate determination.

Circ_0105346 Knockdown Inhibits Osteosarcoma Development via Regulating miR-1182/WNT7B Axis

Background

Osteosarcoma (OS) is a common bone malignancy in children and adolescents. Circular RNAs (circRNAs) have been reported to affect OS progression. This paper mainly delineated the role of circRNA circ_0105346 in OS development and the potential mechanism.

Methods

Quantitative reverse transcription PCR (qRT-PCR) and Western blot assays were applied to detect the expression of circ_0105346, microRNA (miR)-1182 and wingless-type MMTV integration site family 7B (WNT7B). 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was conducted to evaluate cell viability, and flow cytometry was performed to monitor cell apoptosis and cycle. In addition, cell migration and invasion were determined via transwell assay. Wound healing assay was also employed to evaluate the migrated capacity of OS cells. Western blot assay was also employed to examine the levels of protein markers. Additionally, the interaction between miR-1182 and circ_0105346 or WNT7B was confirmed by the dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays. Mouse xenograft model was constructed to clarify the effect of circ_0105346 on tumor growth in vivo.

Results

Circ_0105346 and WNT7B were upregulated, while miR-1182 was downregulated in OS tissues and cells. Circ_0105346 knockdown suppressed OS cell proliferation, cell cycle, migration, invasion and glycolysis, as well as accelerated apoptosis, which was attenuated by miR-1182 inhibition. Interestingly, circ_0105346 targeted miR-1182, and miR-1182 interacted with WNT7B. Circ_0105346 could upregulate WNT7B by downregulating miR-1182 expression. Furthermore, circ_0105346 knockdown blocked tumor growth in vivo.

Conclusion

Circ_0105346 knockdown repressed OS progression by regulating miR-1182/WNT7B axis, at least in part.

Role of microRNAs in the crosstalk between osteosarcoma cells and the tumour microenvironment

Osteosarcoma (OS) is the most common primary bone tumour, with a peak incidence in adolescents, and the five-year survival rate of patients with metastasis or recurrence is much lower than that of patients without metastasis and recurrence. OS is initiated and develops in a complex tumour microenvironment (TME) that contains many different components, such as osteoblasts, osteoclasts, mesenchymal stem cells, fibroblasts, immune cells, extracellular matrix (ECM), extracellular vesicles, and cytokines. The extensive interaction between OS and the TME underlies OS progression. Therefore, rather than targeting OS cells, targeting the key factors in the TME may yield novel therapeutic approaches. MicroRNAs (miRNAs) play multiple roles in the biological behaviours of OS, and recent studies have implied that miRNAs are involved in mediating the communication between OS cells and the surrounding TME. Here, we review the TME landscape and the miRNA dysregulation of OS, describe the role of the altered TME in OS development and highlight the role of miRNA in the crosstalk between OS cells and the TME.

Targeting Molecular Mechanisms Underlying Treatment Efficacy and Resistance in Osteosarcoma: A Review of Current and Future Strategies

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Due to micrometastatic spread, radical surgery alone rarely results in cure. Introduction of combination chemotherapy in the 1970s, however, dramatically increased overall survival rates from 20% to approximately 70%. Unfortunately, large clinical trials aiming to intensify treatment in the past decades have failed to achieve higher cure rates. In this review, we revisit how the heterogenous nature of osteosarcoma as well as acquired and intrinsic resistance to chemotherapy can account for stagnation in therapy improvement. We summarise current osteosarcoma treatment strategies focusing on molecular determinants of treatment susceptibility and resistance. Understanding therapy susceptibility and resistance provides a basis for rational therapy betterment for both identifying patients that might be cured with less toxic interventions and targeting resistance mechanisms to sensitise resistant osteosarcoma to conventional therapies.

A Novel Peptide, CK2.3, Improved Bone Formation in Ovariectomized Sprague Dawley Rats

Osteoporosis is a bone disease that has no definite cure. Current treatments for osteoporosis are divided into two categories: anti-resorptive and anabolic. However, these treatments are not perfect and have considerable risks. In addition, bone quality often declines over time with these treatments. We designed a peptide, CK2.3, that has both anabolic and anti-resorptive effects on bone. We reported that CK2.3 induced osteoblastic mineralization, promoted bone formation, and suppressed osteoclastogenesis in vivo. The effect of CK2.3 to rescue an osteoporosis phenotype model has never been shown. In this study, we demonstrated the effect of CK2.3 in ovariectomized rats, a standard model of osteoporosis. We systemically injected CK2.3 at 2.3 µg/kg each day for five consecutive days. Micro-computed tomography indicated that CK2.3 increased bone mineral density, (bone volume/tissue volume) BV/TV and (trabecular number) TbN, and decreased (trabecular space) TbSp in the femoral head. Similarly, single photon absorptiometry showed that treatment with CK2.3 increased bone mineral density in the lumbar spine and the pelvis. Additionally, we observed increased femoral shaft stiffness with ovariectomized rats treated with CK2.3. We also detected no significant changes in the weight of organs such as the heart, lung, liver, kidney, and spleen. An advantage of CK2.3 over current treatments was that it not only promoted bone formation but also improved fracture resistance. In conclusion, we demonstrated CK2.3 as a new anabolic treatment for osteoporosis.

URG4 mediates cell proliferation and cell cycle in osteosarcoma via GSK3β/β-catenin/cyclin D1 signaling pathway

BACKGROUND

Osteosarcoma is one of the most common malignant bone tumors with the annual global incidence of approximately four per million. Upregulated gene 4 (URG4) expression in the osteosarcoma tissue is closely associated with recurrence, metastasis, and poor prognosis of osteosarcoma. However, the biological function and underlying mechanisms of URG4 in osteosarcoma have not been elucidated. This study aimed to explore the expression and underlying mechanism of URG4 in osteosarcoma.

METHODS

The expression level of URG4 in osteosarcoma and normal tissues was compared using immunohistochemistry (IHC). PCR and western blotting (WB) techniques are used to detect URG4 mRNA and protein levels. Wound healing and Transwell analysis to assess the effect of URG4 on osteosarcoma cell migration and invasion. Cell Counting Kit-8 assay and colony proliferation assay were performed to evaluate the effects of silencing URG4 on the inhibition of cell proliferation. The cell cycle distribution was detected by flow cytometry, and a xenograft mouse model was used to verify the function of URG4 in vivo.

RESULTS

URG4 was found to be highly expressed in osteosarcoma tissues and cells, and its high expression was correlated with advanced Enneking stage, large tumor size, and tumor metastasis in osteosarcoma patients. The proliferation in osteosarcoma cell lines and cell cycle in the S phase was suppressed when siRNA was used to downregulate URG4. URG4 promoted cell proliferation and tumorigenesis in vitro and in vivo. WB verified that URG4 promotes cell proliferation in osteosarcoma via pGSK3β/β-catenin/cyclinD1 signaling.

CONCLUSION

URG4, which is high-expressed in osteosarcoma, promotes cell cycle progression via GSK3β/β-catenin/cyclin D1 signaling pathway and may be a novel biomarker and potential target for the treatment of osteosarcoma.

Tegavivint and the β-Catenin/ALDH Axis in Chemotherapy-Resistant and Metastatic Osteosarcoma

BACKGROUND

The Wnt/β-catenin pathway is closely associated with osteosarcoma (OS) development and metastatic progression. We investigated the antitumor activity of Tegavivint, a novel β-catenin/transducin β-like protein 1 (TBL1) inhibitor, against OS employing in vitro, ex vivo, and in vivo cell line and patient-derived xenograft (PDX) models that recapitulate high risk disease.

METHODS

The antitumor efficacy of Tegavivint was evaluated in vitro using established OS and PDX-derived cell lines. Use of an ex vivo three-dimensional pulmonary metastasis assay assessed targeting of β-catenin activity during micro- and macrometastatic development. The in vivo activity of Tegavivint was evaluated using chemoresistant and metastatic OS PDX models. Gene and protein expression were quantified by quantitative Reverse transcription polymerase chain reaction or immunoblot analysis. Bone integrity was determined via microCT. All statistical tests were two-sided.

RESULTS

Tegavivint exhibited antiproliferative activity against OS cells in vitro and actively reduced micro- and macrometastatic development ex vivo. Multiple OS PDX tumors (n = 3), including paired patient primary and lung metastatic tumors with inherent chemoresistance, were suppressed by Tegavivint in vivo. We identified that metastatic lung OS cell lines (n = 2) exhibited increased stem cell signatures, including enhanced concomitant aldehyde dehydrogenase (ALDH1) and β-catenin expression and downstream activity, which were suppressed by Tegavivint (ALDH1: control group, mean relative mRNA expression = 1.00, 95% confidence interval [CI] = 0.68 to 1.22 vs Tegavivint group, mean = 0.011, 95% CI = 0.0012 to 0.056, P < .001; β-catenin: control group, mean relative mRNA expression = 1.00, 95% CI = 0.71 to 1.36 vs Tegavivint group, mean = 0.45, 95% CI = 0.36 to 0.52, P < .001). ALDH1high PDX-derived lung OS cells, which demonstrated enhanced metastatic potential compared with ALDHlow cells in vivo, were sensitive to Tegavivint. Toxicity studies revealed decreased bone density in male Tegavivint-treated mice (n = 4 mice per group).

CONCLUSIONS

Tegavivint is a promising therapeutic agent for advanced stages of OS via its targeting of the β-catenin/ALDH1 axis.

The PI3K/AKT pathway promotes fracture healing through its crosstalk with Wnt/β-catenin

PI3K/AKT is one of the key pathways that regulate cell behaviors including apoptosis, proliferation, and differentiation. Although previous studies have demonstrated that this pathway is a crucial regulator of osteoblasts, the role of PI3K/AKT in fracture healing remains unclear. It is well known that the Wnt/β-catenin pathway plays an essential role in bone regeneration. However, whether there exists crosstalk between Wnt/β-catenin and PI3K/AKT in regulating osteoblasts and bone repair has not been reported. To address these issues, we establish a stabilized fracture model in mice and show that PI3K inhibitor LY294002 substantially inhibits the bone healing process, suggesting that PI3K/AKT promotes fracture repair. More importantly, we report that PI3K/AKT increases phosphorylation of GSK-3β at Ser9 and phosphorylation of β-catenin at Ser552 in fracture callus and murine osteoblastic MC3T3-E1 cells, both of which lead to β-catenin stabilization, nuclear translocation, as well as β-catenin-mediated TCF-dependent transcription, suggesting that β-catenin is activated downstream of PI3K/AKT. Furthermore, we show that ICG001, the inhibitor of β-catenin transcriptional activity, attenuates PI3K/AKT-induced osteoblast proliferation, differentiation, and mineralization, indicating that the PI3K/AKT/β-catenin axis is functional in regulating osteoblasts. Notably, the PI3K/AKT pathway is also activated by Wnt3a and is involved in Wnt3a-induced osteoblast proliferation and differentiation. Hence, our results reveal the existence of a Wnt/PI3K/AKT/β-catenin signaling nexus in osteoblasts, highlighting complex crosstalk between PI3K/AKT and Wnt/β-catenin pathways that are critically implicated in fracture healing.

Longitudinal evaluation of Wnt inhibitors and comparison with others serum osteoimmunological biomarkers in osteolytic bone metastasis

Bone and the immune system are closely linked: bone regulates the hematopoietic stem cells, which are precursors of immune cells, and several immunoregulatory cytokines influence the differentiation of bone cells, thus defining the osteoimmunological system. Cytokines and growth factors produced by immune and bone cells promote tumors in bone, supporting the vicious cycle of bone metastasis. Therefore osteoimmunological molecules linking the immune and bone systems could have diagnostic and prognostic potential for bone metastases. The osteoimmunologic Wnt pathway has been recently described as an important pathway with a vital role in bone carcinogenesis and metastatic progression. We examined the Wnt inhibitor DKK-1, sclerostin and several other osteoimmunological biomarkers involved in bone metastatic progression: RANKL, OPG, OPN, matrix metalloproteinase MMP-3 and the Receptor of Advanced Glycosylated End-products sRAGE. OPN and sclerostin proved good biomarkers of metastatic bone progression; the RANKL/OPG ratio was a good indicator of bone erosion in the metastatic process, while sRAGE had a protective role against metastatic progression in bone. These results serve to define a panel of new osteoimmunological biomarkers that could be useful in assessing the progress of osteolytic bone metastases.

Nanomedicine in osteosarcoma therapy: Micelleplexes for delivery of nucleic acids and drugs toward osteosarcoma-targeted therapies

Osteosarcoma(OS) represents the main cancer affecting bone tissue, and one of the most frequent in children. In this review we discuss the major pathological hallmarks of this pathology, its current therapeutics, new active biomolecules, as well as the nanotechnology outbreak applied to the development of innovative strategies for selective OS targeting. Small RNA molecules play a role as key-regulator molecules capable of orchestrate different responses in what concerns cancer initiation, proliferation, migration and invasiveness. Frequently associated with lung metastasis, new strategies are urgent to upgrade the therapeutic outcomes and the life-expectancy prospects. Hence, the prominent rise of micelleplexes as multifaceted and efficient structures for nucleic acid delivery and selective drug targeting is revisited here with special emphasis on ligand-mediated active targeting. Future landmarks toward the development of novel nanostrategies for both OS diagnosis and OS therapy improvements are also discussed.

FGF-induced LHX9 regulates the progression and metastasis of osteosarcoma via FRS2/TGF-β/β-catenin pathway

Background

Fibroblast growth factor (FGF) and tumor growth factor-β (TGFβ) have emerged as pivotal regulators during the progression of osteosarcoma (OS). LHX9 is one crucial transcription factor controlled by FGF, however, its function in OS has not been investigated yet.

Methods

The expression of LHX9, FRS2, BMP4, TGF-beta R1, SMAD2, beta-catenin and metastasis-related proteins was measured by real-time quantitative PCR (RT-qPCR) and Western blot. CCK-8 assay and colony formation assay were employed to determine the proliferation of OS cells, while scratch wound healing assay and transwell assay were used to evaluate their migration and invasion, respectively. In vivo tumor growth and metastasis were determined by subcutaneous or intravenous injection of OS cells into nude mice.

Results

LHX9 expression was evidently up-regulated in OS tumor tissues and cell lines. Knockdown of LHX9 impaired the proliferation, migration, invasion and metastasis of OS cells. Mechanistically, LHX9 silencing led to the down-regulation of BMP-4, β-catenin and metastasis-related proteins, which was also observed in beta-catenin knockdown OS cells. By contrast, FRS2 knockdown conduced to the up-regulation of LHX9, BMP4, β-catenin and TGF-βR1, while TGF-beta inhibition repressed the expression of LHX9 and metastasis-related proteins. Additionally, let-7c modulates LHX9 and metastasis-related proteins by suppressing TGF-beta R1 expression on transcriptional level.

Conclusions

This study revealed LHX9 was essential for the proliferation, migration, invasion, and metastasis of OS cells via FGF and TGF-β/β-catenin signaling pathways.

Carboxypeptidase E-ΔN promotes migration, invasiveness, and epithelial–mesenchymal transition of human osteosarcoma cells via the Wnt–β-catenin pathway

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents, and metastatic OS is the major cause of OS-related death. Carboxypeptidase E (CPE) is known to be highly expressed in some cancer types, and its N-terminal truncated form, CPE-ΔN, is implicated in tumor metastasis and poor prognosis. In this study, we investigated the effect of CPE-ΔN on cell migration, invasiveness, and the epithelial–mesenchymal transition (EMT) of OS cells, and illustrated the molecular mechanisms. We first constructed CPE-ΔN overexpressing human OS cell lines (143B and U2OS cells), and found that ectopic CPE-ΔN expression in OS cells enhanced cell migration and invasiveness, and promoted the EMT process. Further, overexpression of CPE-ΔN increased the levels of c-myc and nuclear β-catenin in OS cells, which suggested the CPE-ΔN promotes activation of the Wnt–β-catenin pathway in OS cells. Treatment with β-catenin small interfering RNA (siRNA) inhibited the migration and invasiveness of CPE-ΔN-overexpressing cells, and reduced the expression of E-cadherin. Together, these results suggest that CPE-ΔN promotes migration, invasiveness, and the EMT of OS cells via the Wnt–β-catenin signaling pathway.

miR-425-5p decreases LncRNA MALAT1 and TUG1 expressions and suppresses tumorigenesis in osteosarcoma via Wnt/β-catenin signaling pathway

Multiple miRNAs have been recognized as critical regulators in osteosarcoma (OS) carcinogenesis. miR-425-5p was demonstrated to be downregulated in the serum of OS patients. However, the detailed roles of miR-425-5p in OS progression and its underlying molecular mechanism are far from being addressed. In our study, the reduced expression of miR-425-5p was observed in OS tissues and cells. Functional analyses showed that miR-425-5p overexpression suppressed OS cell proliferation, invasion and migration in vitro. Moreover, miR-425-5p upregulation decreased the expressions of MALAT1 and TUG1 in OS cells via directly binding them. miR-425-5p upregulation strikingly abrogated the activation of Wnt/β-catenin signaling pathway induced by MALAT1 and TUG1 overexpression in OS cells. Finally, we validated that miR-425-5p hindered OS tumor growth, and suppressed MALAT1 and TUG1 expressions and the Wnt/β-catenin signaling pathway in vivo. Our findings concluded that miR-425-5p suppressed the tumorigenesis of OS via decreasing MALAT1 and TUG1 expressions through inactivation of the Wnt/β-catenin signaling pathway, contributing to a better understanding of the molecular mechanism of the tumorigenesis of OS.

Genome-wide DNA-methylation profiles in human bone marrow mesenchymal stem cells on titanium surfaces

The characteristics of titanium (Ti) have been shown to influence dental implant fixation. Treatment of surfaces using the sandblasted, large-grit, acid-etched (SLA) method is widely used to provide effective osseointegration. However, the DNA methylation-associated mechanism by which SLA surface treatment affects osseointegration of human bone marrow mesenchymal stem cells (hBMSCs) remains elusive. Genome-wide methylation profiling of hBMSCs on SLA-treated and machined smooth Ti was performed using Illumina Infinium Methylation EPIC BeadChip at day 7 of osteogenic induction. In total, 2,846 CpG sites were differentially methylated in the SLA group compared with the machined group. Of these sites, 1,651 (covering 1,066 genes) were significantly hypermethylated and 1,195 (covering 775 genes) were significantly hypomethylated. Thirty significant enrichment pathways were observed, with Wnt signaling being the most significant. mRNA expression was identified by microarray and combined with DNA-methylation profiles. Thirty-seven genes displayed negative association between mRNA expression and DNA-methylation level, with the osteogenesis-related genes insulin-like growth factor 2 (IGF2) and carboxypeptidase X, M14 Family Member 2 (CPXM2) showing significant up-regulation and down-regulation, respectively. In summary, our results demonstrate differences between SLA-treated and machined surfaces in their effects on genome-wide DNA methylation and enrichment of osteogenic pathways in hBMSCs. We provide novel insights into genes and pathways affected by SLA treatment in hBMSCs at the molecular level.

Ganoderma lucidum Exerts an Anticancer Effect on Human Osteosarcoma Cells via Suppressing the Wnt/β-Catenin Signaling Pathway

Background: Current treatment of osteosarcoma is limited in part by side effects and low tolerability, problems generally avoided with traditional Chinese medicine. Ganoderma lucidum, a traditional Chinese medicine with antitumor effects, offers a potential alternative, but little is known about its molecular mechanisms in osteosarcoma cells. Objective: To investigate the effect of G lucidum on osteosarcoma cells and its mechanism. Methods: Osteosarcoma MG63 and U2-OS cells were treated with G lucidum, followed by assays for cell proliferation (Cell Counting Kit-8), colony formation, and apoptosis (Alexa Fluor 647-Annexin V/propidium iodide, flow cytometry). Migration and invasion of cells were assessed by wound healing and Transwell invasion assays, and the effect of G lucidum on Wnt/β-catenin signal transduction was studied by real-time quantitative polymerase chain reaction, western blot, and dual-luciferase assay. Results:G lucidum inhibited the proliferation, migration, and invasion, and induced apoptosis of human osteosarcoma MG63 and U2-OS cells. Dual-luciferase assay showed that G lucidum suppressed the transcriptional activity of T-cell factor/lymphocyte enhancer factor in the Wnt/β-catenin signaling pathway. Moreover, G lucidum blocked Wnt/β-catenin signaling by inhibiting the Wnt co-receptor LRP5 and Wnt-related target genes, such as β-catenin, cyclin D1, C-Myc, MMP-2, and MMP-9. At the same time, when Wnt/β-catenin was inhibited, the expression of E-cadherin was upregulated. Conclusions: Our results suggest that G lucidum broadly suppresses osteosarcoma cell growth by inhibiting Wnt/β-catenin signaling.

miR-885-5p suppresses osteosarcoma proliferation, migration and invasion through regulation of β-catenin

MicroRNAs (miRs) have been reported to serve key roles in cancer. To investigate the function of miR-885-5p in osteosarcoma, the expression levels of miR-885-5p were analyzed in 85 osteosarcoma tissue samples and adjacent non-cancerous tissue samples, using reverse transcription-quantitative polymerase chain reaction analysis. It was demonstrated that miR-885-5p was downregulated in osteosarcoma tissues and cell lines. Notably, the expression level of miR-885-5p was closely associated with tumor size, Tumor-Node-Metastasis stage and lymph node metastasis. Additionally, low expression levels of miR-885-5p also predicted a poor prognosis of osteosarcoma. To further decipher the roles of miR-885-5p in osteosarcoma, it was determined that β-catenin, a key component of the Wnt signaling pathway, was a target of miR-885-5p. Furthermore, several functional experiments, including a colony formation assay, CCK-8 assay, wound healing assay and Transwell invasion assay, revealed that miR-885-5p suppressed cell proliferation, migration and invasion through inhibition of β-catenin. The results of the present study provide a novel insight into the molecular roles of miR-885-5p in osteosarcoma.

Biglycan Regulates MG63 Osteosarcoma Cell Growth Through a LPR6/β-Catenin/IGFR-IR Signaling Axis

Biglycan, a small leucine rich proteoglycan (SLRP), is an important participant in bone homeostasis and development as well as in bone pathology. In the present study biglycan was identified as a positive regulator of MG63 osteosarcoma cell growth (p ≤ 0.001). IGF-I was shown to increase biglycan expression (p ≤ 0.01), whereas biglycan-deficiency attenuated significantly both basal and IGF-I induced cell proliferation of MG63 cells (p ≤ 0.001; p ≤ 0.01, respectively). These effects were executed through the IGF-IR receptor whose activation was strongly attenuated (p ≤ 0.01) in biglycan-deficient MG63 cells. Biglycan, previously shown to regulate Wnt/β-catenin pathway, was demonstrated to induce a significant increase in β-catenin protein expression evident at cytoplasmic (p ≤ 0.01), membrane (p ≤ 0.01), and nucleus fractions in MG63 cells (p ≤ 0.05). As demonstrated by immunofluorescence, increase in β-catenin expression is attributed to co-localization of biglycan with the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) resulting in attenuated β-catenin degradation. Furthermore, applying anti-β-catenin and anti-pIGF-IR antibodies to MG-63 cells demonstrated a cytoplasmic and to the membrane interaction between these molecules that increased upon exogenous biglycan treatment. In parallel, the downregulation of biglycan significantly inhibited both basal and IGF-I-dependent ERK1/2 activation, (p ≤ 0.001). In summary, we report a novel mechanism where biglycan through a LRP6/β-catenin/IGF-IR signaling axis enhances osteosarcoma cell growth.

TRIM2 regulates the development and metastasis of tumorous cells of osteosarcoma

The present study aimed to investigate candidate genes involved in the development and metastasis of osteosarcoma. Candidate genes were screened preliminarily from the Gene Expression Omnibus database and then validated using actual tumor tissues collected from patients with osteosarcoma. The cells were prepared and transfected with specific gene-targeted small interfering RNA followed by an MTS assay for cell viability detection and Transwell assays for cell migration and invasion capacity detection. The cell apoptosis was determined by flow cytometry and the protein level of the genes was detected by western blot analysis. An in vivo nude model was used and injected with cells to detect the functions of the genes. Transcriptome sequencing was performed to verify the regulation network, followed by reverse transcription-quantitative polymerase chain reaction and western blot analyses for validation. Increased tripartite motif-containing protein 2 (TRIM2) was detected in the osteosarcoma tumor tissues compared with normal tissues. The inhibition of TRIM2 induced lower cell viability and cell invasion capacity, and increased the rate of cell apoptosis. Decreased TRIM2 also inhibited the development and metastasis of osteosarcoma in the nude mouse models. The transcriptome sequencing revealed that the regulation of TRIM2 may be correlated with genes, Sirtuin 4, DNA damage inducible transcript 3, cAMP responsive element binding protein 5, G protein-coupled receptor 65 (GPR65) and ADP-ribosyltransferase 5. Western blot analysis indicated that TRIM2 regulated the development and metastasis of osteosarcoma via the phosphoinositide 3-kinase/protein kinase B signaling pathway. Therefore, TRIM2 performs important functions in regulating the development and metastasis of osteosarcoma.

Analyzing the disease module associated with osteosarcoma via a network- and pathway-based approach

Osteosarcoma is the most common type of primary malignant bone tumor observed in children and adolescents. The aim of the present study was to identify an osteosarcoma-related gene module (OSM) by looking for a dense module following the integration of signals from genome-wide association studies (GWAS) into the human protein-protein interaction (PPI) network. A dataset of somatic mutations in osteosarcoma was obtained from the dbGaP database and their testing P-values were incorporated into the PPI network from a recent study using the dmGWAS bioconductor package. An OSM containing 201 genes (OS genes) and 268 interactions, which were closely associated with immune response, intracellular signal transduction and cell activity was identified. Topological analysis of the OSM identified 11 genes, including APP, APPBP2, ATXN1, HSP90B1, IKZF1, KRTAP10-1, PAK1, PDPK1, SMAD4, SUZ12 and TP53 as potential diagnostic biomarkers for osteosarcoma. The overall survival analysis of osteosarcoma for those 11 genes based on a dataset from the Cancer Genome Atlas, identified APP, HSP90B1, SUZ12 and IKZF1 as osteosarcoma survival-related genes. The results of the present study should be helpful in understanding the diagnosis and treatment of osteosarcoma and its underlying mechanisms. In addition, the methodology used in the present study may be suitable for the analysis of other types of disease.

The nuclear-cytoplasmic trafficking of a chromatin-modifying and remodelling protein (KMT2C), in osteosarcoma

Osteosarcoma is the most common paediatric primary non-hematopoietic bone tumor; the survival is related to the response to chemotherapy and development of metastases. KMT2C is a chromatin-modifying and remodelling protein and its expression has never been studied in osteosarcoma. The aim of this study was to understand the role of KMT2C in the osteosarcoma carcinogenesis and metastatic progression to identify a new molecular target and to provide new therapeutic approach.

We performed the immunohistochemical and gene expression analysis of KMT2C in 32 samples of patients with diagnosis of osteosarcoma with known clinic-pathological data and we analysed the expression of genes involved in the metastatic pathway in four osteosarcoma cell lines by blocking the KMT2C expression using siRNA.

We found a nuclear-cytoplamic trafficking of KMT2C and the cytoplasmic localization was higher than the nuclear localization (p < 0.0001). Moreover, the percentage of cells with cytoplasmic positivity increased from low grade primary tissue to metastatic tissues. The cytoplasmic localization of KMT2C could lead to a change in its function supporting osteosarcoma carcinogenesis and progression. Our hypothesis is that KMT2C could affect the enhancer activity of genes influencing the invasive properties and metastatic potential of 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.

A monoclonal antibody against the Wnt signaling inhibitor dickkopf-1 inhibits osteosarcoma metastasis in a preclinical model

The outcome of patients with metastatic osteosarcoma has not improved since the introduction of chemotherapy in the 1970s. Development of therapies targeting the metastatic cascade is a tremendous unmet medical need. The Wnt signaling pathway has been the focus of intense investigation in osteosarcoma because of its role in normal bone development. Although the role of Wnt signaling in the pathogenesis of osteosarcoma is controversial, there are several reports of dickkopf-1 (DKK-1), a Wnt signaling antagonist, possibly playing a pro-tumorigenic role. In this work we investigated the effect of anti-DKK-1 antibodies on the growth and metastasis of patient-derived osteosarcoma xenografts. We were able to detect human DKK-1 in the blood of tumor-bearing mice and found a correlation between DKK-1 level and tumor proliferation. Treatment with the anti-DKK-1 antibody, BHQ880, slowed the growth of orthotopically implanted patient-derived osteosarcoma xenografts and inhibited metastasis. This effect was correlated with increased nuclear beta-catenin staining and increased expression of the bone differentiation marker osteopontin. These findings suggest that Wnt signaling is anti-tumorigenic in osteosarcoma, and support the targeting of DKK-1 as an anti-metastatic strategy for patients with osteosarcoma.

Logistic regression analysis for the identification of the metastasis-associated signaling pathways of osteosarcoma

Osteosarcoma (OS) is the most common histological type of primary bone cancer. The present study was designed to identify the key genes and signaling pathways involved in the metastasis of OS. Microarray data of GSE39055 were downloaded from the Gene Expression Omnibus database, which included 19 OS biopsy specimens before metastasis (control group) and 18 OS biopsy specimens after metastasis (case group). After the differentially expressed genes (DEGs) were identified using the Linear Models for Microarray Analysis package, hierarchical clustering analysis and unsupervised clustering analysis were performed separately, using orange software and the self-organization map method. Based upon the Database for Annotation, Visualization and Integrated Discovery tool and Cytoscape software, enrichment analysis and protein-protein interaction (PPI) network analysis were conducted, respectively. After function deviation scores were calculated for the significantly enriched terms, hierarchical clustering analysis was performed using Cluster 3.0 software. Furthermore, logistic regression analysis was used to identify the terms that were significantly different. Those terms that were significantly different were validated using other independent datasets. There were 840 DEGs in the case group. There were various interactions in the PPI network [including intercellular adhesion molecule-1 (ICAM1), transforming growth factor β1 (TGFB1), TGFB1-platelet-derived growth factor subunit B (PDGFB) and PDGFB-platelet-derived growth factor receptor-β (PDGFRB)]. Regulation of cell migration, nucleotide excision repair, the Wnt signaling pathway and cell migration were identified as the terms that were significantly different. ICAM1, PDGFB, PDGFRB and TGFB1 were identified to be enriched in cell migration and regulation of cell migration. Nucleotide excision repair and the Wnt signaling pathway were the metastasis-associated pathways of OS. In addition, ICAM1, PDGFB, PDGFRB and TGFB1, which were involved in cell migration and regulation of cell migration may affect the metastasis of OS.

Antitumor activity of resveratrol against human osteosarcoma cells: a key role of Cx43 and Wnt/β-catenin signaling pathway

Osteosarcoma is a high-grade bone sarcoma with strong invasive ability. However, treatment with traditional chemotherapeutic drugs is limited by low tolerability and side effects. Resveratrol has been reported previously to have selective antitumor effect on various tumor cells while little is known about its effects and underlying mechanism in osteosarcoma biology. In this study, we found that resveratrol inhibits proliferation and glycolysis, induces apoptosis and reduces the invasiveness of U2-OS cells in vitro. After treatment with resveratrol, the expression of related Wnt/β-catenin signaling pathway target genes, such as β-catenin, c-myc, cyclin D1, MMP-2 and MMP-9, was downregulated and an increased E-cadherin level was observed as well. Additionally, the dual luciferase assay results also indicated that resveratrol suppressed the activity of Wnt/β-catenin signaling pathway. Interestingly, we noticed that the expression of connexin 43 (Cx43) increased with the prolongation of resveratrol treatment time. To further investigate the relationship between Cx43 and the Wnt/β-catenin signaling pathway in osteosarcoma, we used lentiviral-mediated shRNA to knockdown the expression of Cx43. Knockdown of Cx43 activated the Wnt/β-catenin signaling pathway, promoted proliferation and invasion, and inhibited apoptosis of U2-OS cells. Taken together, our results demonstrate that the antitumor activity of resveratrol against U2-OS cells in vitro occurs through up-regulating Cx43 and E-cadherin, and suppressing the Wnt/β-catenin signaling pathway. Moreover, Cx43 expression is negatively related to the activity of the Wnt/β-catenin pathway in U2-OS cells.

TRIM37 promotes tumor cell proliferation and drug resistance in pediatric osteosarcoma

Osteosarcoma (OS) is among the most frequently occurring bone tumors, particularly in children. Clinical treatment of OS is limited due to several factors including resistance to chemotherapy drugs and metastasis, and the underlying molecular mechanisms remain unclear. In the present study, tripartite motif containing 37 (TRIM37) expression levels were upregulated in tumor samples and associated with the development of drug resistance in OS. Furthermore, chemotherapy drug treatment (doxorubicin, cisplatin and methotrexate) induced TRIM37 expression in OS cells in vitro. TRIM37 mRNA and protein were upregulated in 41 pediatric osteosarcoma clinical specimens. To further elucidate the effect of TRIM37, gain and loss-of-function analysis was performed. Overexpression of TRIM37 induced cell proliferation and drug resistance ability of OS cells, whilst TRIM37 knockdown suppressed cell growth rate and restored chemosensitivity. TRIM37-regulated genes were subsequently analyzed by expression microarray and gene set enrichment analysis. Using the Wnt/β-catenin inhibitor XAV-939, the present study demonstrated that TRIM37-induced chemoresistance is partially dependent on the activation of the Wnt/β-catenin signaling pathway. Collectively, the results of the present study suggest that TRIM37 may have a key role in the development of OS and in the ability for the cells to acquire drug resistance, thus it may be a novel target for the treatment of OS.

Baicalein inhibits progression of osteosarcoma cells through inactivation of the Wnt/β-catenin signaling pathway

Osteosarcoma is a very common type of malignant bone tumor in children and young adults and aberrant activation of Wnt/β-catenin signaling pathway has been discovered in osteosarcoma. The traditional Chinese medicine baicalein was proved to have anti-proliferative and anti-metastatic properties in osteosarcoma, but the mechanism remained poorly understood. In the present study, we assessed the effects of baicalein on osteosarcoma and detected the potential molecular mechanism. We found that baicalein significantly suppressed the proliferation of osteosarcoma cells in a concentration- and time-dependent manner. In additional, baicalein could induce apoptosis and cell cycle arrest and reduce cell motility. Moreover, the level of β-catenin and its target genes, including c-myc, cyclinD1, and survivin significantly decreased in baicalein-treated osteosarcoma cells, whereas exogenous expression of β-catenin could reverse the anti-proliferative and anti-metastatic effects of baicalein. Subsequently, we established a 143B xenograft tumor model and found that baicalein treatment significantly inhibited tumor growth accompanied with inhibiting Wnt/β-catenin pathway. Thus, these findings suggest that baicalein may be a potentially effective Chinese herbal medicine for therapeutics of osteosarcoma and Wnt/β-catenin signaling pathway may serve as an efficient molecular marker or predictive target for osteosarcoma.

Gene expression profile comparison between colorectal cancer and adjacent normal tissues

The present study aimed to compare gene expression profiles between colorectal cancer and adjacent normal tissues, and to perform a preliminarily analysis of the key genes and underlying molecular mechanisms implicated in colorectal cancer development. Gene expression microarray chips were used to screen genes that were differently expressed between colorectal cancer and adjacent normal tissues. Approximately 1,183 genes were differentially expressed in cancer tissues compared with adjacent normal tissues (P≤0.05; fold difference, >2.0), of which 570 genes were upregulated and 613 genes were downregulated. In total, 6 upregulated genes, including keratin 23, collagen type X α1, collagen type XI α1, cell migration-inducing hyaluronan-binding protein, transforming growth factor-β1 and V-Myc avian myelocytomatosis viral oncogene homolog, and 2 downregulated genes, including channel α subunit 7 and EPH receptor A7, were selected and validated using reverse transcription-quantitative polymerase chain reaction, which exhibited results that were consistent with the microarray analysis. These 1,183 differentially expressed genes were further classified into 71 groups based on their functions using gene ontology and pathway analyses. Kyoto Encyclopedia of Genes and Genomes analysis of these upregulated or downregulated genes suggested that 23 signaling pathways were involved. The present study preliminarily screened for and identified key genes and signaling pathways that may be closely associated with colorectal cancer development. However, subsequent gene function studies are required to verify these findings.

Molecular genetics of osteosarcoma

Osteosarcoma is the predominant form of bone cancer, affecting mostly adolescents. Recent progress made in molecular genetic studies of osteosarcoma has changed our view on the cause of the disease and ongoing therapeutic approaches for patients. As we draw closer to gaining more complete catalogs of candidate cancer driver genes in common forms of cancer, the landscape of somatic mutations in osteosarcoma is emerging from its first phase. In this review, we summarize recent whole genome and/or whole exome genomic studies, and then put these findings in the context of genetic hallmarks of somatic mutations and mutational processes in human osteosarcoma. One of the lessons learned here is that the extent of somatic mutations and complexity of the osteosarcoma genome are similar to that of common forms of adult cancer. Thus, a much higher number of samples than those currently obtained are needed to complete the catalog of driver mutations in human osteosarcoma. In parallel, genetic studies in other species have revealed candidate driver genes and their roles in the genesis of osteosarcoma. This review also summarizes newly identified drivers in genetically engineered mouse models (GEMMs) and discusses our understanding of the impact of nature and number of drivers on tumor latency, subtypes, and metastatic potentials of osteosarcoma. It is becoming apparent that a synergistic team composed of three drivers (one 'first driver' and two 'synergistic drivers') may be required to generate an animal model that recapitulates aggressive osteosarcoma with a short latency. Finally, new cancer therapies are urgently needed to improve survival rate and quality of life for osteosarcoma patients. Several vulnerabilities in osteosarcoma are illustrated in this review to exemplify the opportunities for next generation molecularly targeted therapies. However, much work remains in order to complete our understanding of the somatic mutation basis of osteosarcoma, to develop reliable animal models of human disease, and to apply this information to guide new therapeutic approaches for reducing morbidity and mortality of this rare disease.

Germline and somatic genetics of osteosarcoma - connecting aetiology, biology and therapy

Clinical outcomes and treatment modalities for osteosarcoma, the most common primary cancer of bone, have changed very little over the past 30 years. The peak incidence of osteosarcoma occurs during the adolescent growth spurt, which suggests that bone growth and pubertal hormones are important in the aetiology of the disease. Tall stature, high birth weight and certain inherited cancer predisposition syndromes are well-described risk factors for osteosarcoma. Common genetic variants are also associated with osteosarcoma. The somatic genome of osteosarcoma is highly aneuploid, exhibits extensive intratumoural heterogeneity and has a higher mutation rate than most other paediatric cancers. Complex pathways related to bone growth and development and tumorigenesis are also important in osteosarcoma biology. In this Review, we discuss the contributions of germline and somatic genetics, tumour biology and animal models in improving our understanding of osteosarcoma aetiology, and their potential to identify novel therapeutic targets and thus improve the lives of patients with osteosarcoma.

The Overexpression of CARM1 Promotes Human Osteosarcoma Cell Proliferation through the pGSK3β/β-Catenin/cyclinD1 Signaling Pathway

Osteosarcoma (OS) is a kind of malignant bone tumor that occurs frequently in the region surrounding the knee joint and poses a threat to the health of teenagers. Since the application of chemotherapy to treat OS, 5-year survival rate in patients has improved from 10% to 70%, but patient survival has not changed over the past four decades. Coactivator-associated arginine methyltransferase 1 (CARM1) is a member of the PRMT protein family; it acts as an oncogene in many cancers, but its function in OS is still unknown. In this study, we found that CARM1 is overexpressed in OS and its expression is correlated with the Enneking stage. CCK-8 and colony forming assays showed that proliferation in OS cell lines was downregulated when siRNA was used to knockdown CARM1 expression. The cell cycle was inhibited in S phase after si-CARM1 transfection in OS cell lines. An antibody array indicated that Erk1/2 (Thr202/Tyr204), PARS40 (Thr246), and GSK3β (Ser9) expression are affected by CARM1, and western blotting verified that CARM1 promotes OS cell proliferation via pGSK3β/β-catenin/cyclinD1 signaling. Accordingly, CARM1 is a crucial gene in OS and is a potential new treatment target.