Mefenamic acid exhibits antitumor activity against osteosarcoma by impeding cell growth and prompting apoptosis in human osteosarcoma cells and xenograft mice model

The study investigates the anticancer activity of mefenamic acid against osteosarcoma, shedding light on its underlying mechanisms and therapeutic potential. Mefenamic acid exhibited robust inhibitory effects on the proliferation of MG-63, HOS, and H2OS osteosarcoma cells in a dose-dependent manner. Moreover, mefenamic acid induced cellular toxicity in MG63 cells, as evidenced by LDH leakage, reflecting its cytotoxic impact. Furthermore, mefenamic acid effectively suppressed the migration and invasion of MG-63 cells. Mechanistically, mefenamic acid induced apoptosis in MG-63 cells through mitochondrial depolarization, activation of caspase-dependent pathways, and modulation of the Bcl-2/Bax axis. Additionally, mefenamic acid promoted autophagy and inhibited the PI3K/Akt/mTOR pathway, further contributing to its antitumor effects. The molecular docking studies provide compelling evidence that mefenamic acid interacts specifically and strongly with key proteins in the PI3K/AKT/mTOR pathway, suggesting a novel mechanism by which mefenamic acid could exert anti-osteosarcoma effects. In vivo studies using a xenograft mouse model demonstrated significant inhibition of MG-63 tumor growth without adverse effects, supporting the translational potential of mefenamic acid as a safe and effective therapeutic agent against osteosarcoma. Immunohistochemistry staining corroborated the in vivo findings, highlighting mefenamic acid's ability to suppress tumor proliferation and inhibit the PI3K/AKT/mTOR pathway within the tumor microenvironment. Collectively, these results underscore the promising therapeutic implications of mefenamic acid in combating osteosarcoma, warranting further investigation for clinical translation and development.

Doxorubicin loaded octacalcium phosphate particles as controlled release drug delivery systems: Physico-chemical characterization, in vitro drug release and evaluation of cell death pathway

Mastering new and efficient ways to obtain successful drug delivery systems (DDS) with controlled release became a paramount quest in the scientific community. Increase of malignant bone tumors and the necessity to optimize an approach of localized drug delivery require research to be even more intensified. Octacalcium phosphate (OCP), with a number of advantages over current counterparts is extensively used in bone engineering. The aim of the present research was to synthesize bioactive and biocompatible doxorubicin (DOX) containing OCP particles. DOX-OCP was successfully obtained in situ in an exhaustive range of added drug (1-20 wt%, theoretical loading). Based on XRD, above 10 wt% of DOX, OCP formation was inhibited and the obtained product was low crystalline α-TCP. In-vitro drug release was performed in pH 7.4 and 6.0. In both pH environments DOX had a continuous release over six weeks. However, the initial drug burst for pH 7.4, in the first 24 h, ranged from 15.9 ± 1.3 % to 33.5 ± 12 % and for pH 6.0 23.7 ± 1.5 % to 36.2 ± 12 %.The DOX-OCP exhibited an inhibitory effect on viability of osteosarcoma cell lines MG63, U2OS and HOS. In contrast, MC3T3-E1 cells (IC50 > 0.062 µM) displayed increased viability and proliferation from 3rd to 7th day. Testing of the DDS on ferroptotic markers (CHAC1, ACSL4 and PTGS2) showed that OCP-DOX does not induce ferroptotic cell death. Moreover, the evaluation of protein levels of cleaved PARP, by western blotting analysis, corroborated that apoptosis is the main pathway of programmed cell death in osteosarcoma cells induced by DOX-OCP.

Cell migration induces apoptosis in osteosarcoma cell via inhibition of Wnt-β-catenin signaling pathway

The current design scheme on anti-cancer materials is mainly through tuning the mechanical properties of the materials to induce apoptosis in cancer cells, with the involvement of Rho/ROCK signaling pathway. We hypothesize that tuning the motility is another potential important approach to modifying the tumor microenvironment and inducing tumor apoptosis. To this aim, we have prepared RGD-modified substrates to regulate cell motility through modification of RGD with different concentrations, and systematically examined the effect of motility on the apoptosis of tumor cells, and the potential involvement of Wnt signaling pathway. Our studies indicated that RGD modification could be readily used to tune the motility of cancer cells. High RGD concentration significantly suppressed the migration of cancer cells, leading to significantly increased apoptosis rate, about three times of that of the unmodified samples. Western-blot analysis also showed that cell with low motility expressed more caspase-3 and PARP proteins. Further RNA sequence study strongly suggested that low motility inhibited the canonical Wnt signaling pathway, which in turn led to the activation of the mitochondria-associated caspase signaling pathway, and ultimately to the apoptosis of osteosarcoma cells. Activation of the Wnt-β-catenin pathway through HLY78 significantly suppressed the apoptosis of MG-63 cells, further suggesting the critical role of Wnt pathway in motility-regulated-apoptosis of tumor cells. Our findings shed insights to understand the underlying mechanisms that induced the tumor cell apoptosis, and might provide new strategy for designing the novel anti-tumor materials.

DEPDC1 and KIF4A synergistically inhibit the malignant biological behavior of osteosarcoma cells through Hippo signaling pathway

The treatment of osteosarcoma (OS) is still mainly surgery combined with systematic chemotherapy, and gene therapy is expected to improve the survival rate of patients. This study aimed to explore the effect of DEP domain 1 protein (DEPDC1) and kinesin super-family protein 4A (KIF4A) in OS and understand its mechanism. Th expression of DEPDC1 and KIF4A in OS cells was detected by RT-PCR and western blot. The viability, proliferation, invasion and migration of OS cells and tube formation of human umbilical vein endothelial cells (HUVECs) after indicated treatment were in turn detected by CCK-8 assay, EdU staining, wound healing assay, transwell assay and tube formation assay. The interaction between DEPDC1 and KIF4A was predicted by STRING and confirmed by co-immunoprecipitation. The expression of epithelial-mesenchymal transition (EMT)-related proteins, tube formation-related proteins and Hippo signaling pathway proteins was detected by western blot. As a result, the expression of DEPDC1 and KIF4A was all increased in U2OS cells. Down-regulation of DEPDC1 suppressed the viability, proliferation, invasion and migration of U2OS cells and tube formation of HUVECs, accompanied by the increased expression of E-cadherin and decreased expression of N-cadherin, Vimentin and VEGF. DEPDC1 was confirmed to be interacted with KIF4A. Upregulation of KIF4A partially reversed the effect of DEPDC1 interference on the above biological behaviors of U2OS cells. Down-regulation of DEPDC1 promoted the expression of p-LATS1 and p-YAP in Hippo signaling pathway, which was reversed by upregulation of KIF4A. In conclusion, down-regulation of DEPDC1 inhibited the malignant biological behavior of OS cells through the activation of Hippo signaling pathway, which could be reversed by upregulation of KIF4A.

Effects of free fatty acid receptor-2 (FFAR2)-mediated signaling on the regulation of cellular functions in osteosarcoma cells

G protein coupled free fatty acid receptors (FFARs) are involved in the pathogenesis of several human diseases. FFAR2 and FFAR3 are activated by the binding of short-chain fatty acids (SCFAs). This study aimed to evaluate the roles of FFAR2 in the regulation of cellular functions in osteosarcoma HOS cells, using acetic acid and propanoic acid as FFAR2 and FFAR3 agonists. FFAR2 and FFAR3 genes were expressed in HOS cells. The cell motile activity of HOS cells was significantly stimulated by acetic acid and propanoic acid. In contrast, acetic acid and propanoic acid had no impact on the activation of matrix metalloproteinase-2 (MMP-2) and MMP-9. In cell survival assay, the cell survival rate to cisplatin (CDDP) of HOS cells was elevated by acetic acid and propanoic acid. To assess the effects of FFAR2 on cellular functions, FFAR2 knockdown (HOS-FFAR2) cells were generated from HOS cells. The cell motile activity of HOS-FFAR2 cells was enhanced by acetic acid and propanoic acid. In the presence of acetic acid and propanoic acid, MMP-2 and MMP-9 activities were reduced in HOS-FFAR2 cells, compared with control cells. When cells were treated with acetic acid and propanoic acid, the cell survival rate to CDDP of HOS-FFAR2 cells was significantly lower than that of control cells. These results suggest that activation of FFAR2-mediated signaling is involved in the modulation of cellular functions in HOS cells.

Effects of lysophosphatidic acid (LPA) signaling via LPA receptors on cellular functions associated with ATP reduction in osteosarcoma cells treated with ethidium bromide

Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA₁ to LPA₆) exhibits a variety of malignant properties in cancer cells. Intracellular ATP depletion leads to the development of necrosis and apoptosis. The present study aimed to evaluate the effects of LPA receptor-mediated signaling on the regulation of cancer cell functions associated with ATP reduction. Long-term ethidium bromide (EtBr) treated (MG63-EtBr) cells were established from osteosarcoma MG-63 cells. The intracellular ATP levels of MG63-EtBr cells were significantly lower than that of MG-63 cells. LPAR2, LPAR3, LPAR4 and LPAR6 gene expressions were elevated in MG63-EtBr cells. The cell motile and invasive activities of MG63-EtBr cells were markedly higher than those of MG-63 cells. The cell motile activity of MG-63 cells was increased by LPA₄ and LPA₆ knockdowns. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 3 days. The cell survival to CDDP of MG63-EtBr cells was lower than that of MG-63 cells. LPA₂ knockdown decreased the cell survival to CDDP of MG-63 cells. The cell survival to CDDP of MG-63 cells was inhibited by (2 S)-OMPT (LPA₃ agonist). Moreover, the cell survival to CDDP of MG-63 cells was enhanced by LPA₄ and LPA₆ knockdowns. These results indicate that LPA signaling via LPA receptors is involved in the regulation of cellular functions associated with ATP reduction in MG-63 cells treated with EtBr.

A bone implant with NIR-responsiveness for eliminating osteosarcoma cells and promoting osteogenic differentiation of BMSCs

Incomplete removal of tumor cells and insufficient osseointegration are the main causes of bone tumor recurrence and implantation failure. In the present study, a multifunctional titanium-based bioactive implant for near-infrared-triggered synergy therapy to overcome these hurdles is engineered, composed of titanium dioxide (TiO₂) nanoparticles doped with fluorine (F)/dopamine (PDA)/collagen. The TiO₂ nanoparticles designed in this work can simultaneously exhibit excellent near-infrared-activated photothermal and photocatalytic properties. Besides, the layer designed in this work show excellent anti-tumor activity under irradiation with 808 nm light due to the synergetic effect of hyperthermia and reactive oxygen species (ROS), and Saos-2 cells can be eradicated within 10 min. Moreover, modification of PDA and collagen endue the Ti alloy excellent osteogenic activity.

Roles of endothelial cells in the regulation of cell motility via lysophosphatidic acid receptor-2 (LPA2) and LPA3 in osteosarcoma cells

Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA₁ to LPA₆) exhibits a variety of biological responses. In tumor microenvironment, endothelial cells promote cancer cell functions. In this study, we investigated the roles of endothelial cells in the regulation of cell motile activity via LPA₂ and LPA₃ in human osteosarcoma MG-63 cells. In cell motility assay, the cell motile activity of MG-63 cells was markedly increased by the supernatants of endothelial F2 cells. MG-63 cell motility elevated by the supernatants was enhanced by GRI-977143 (LPA₂ agonist) and reduced by (2S)-OMPT (LPA₃ agonist). LPAR2 and LPAR3 expressions were increased in highly migratory MG63-CR7(F2) cells, which were generated from MG-63 cells by co-culture with F2 cell supernatants. MG63-CR7(F2) cell motility was stimulated by LPA treatment. In the presence of F2 cell supernatants, MG63-CR7(F2) cell motility was markedly enhanced by GRI-977143 and suppressed by (2S)-OMPT. Autotaxin (ATX) enzymatically converts lysophosphatidylcholine (LPC) to LPA. ATX expression was higher in MG63-CR(F2) cells than in MG-63 cells. MG63-CR7(F2) cell motility was markedly increased by LPC in comparison with MG-63 cells. In addition, MG63-CR(F2) cell motility was significantly stimulated by the supernatants of LPC treated F2 cells. The present results suggest that the activation of LPA signaling via LPA₂ and LPA₃ by endothelial cells is involved in the modulation of cell motile activity of MG-63 cells.

MicroRNA-221 Promotes Cell Proliferation and Inhibits Apoptosis in Osteosarcoma Cells by Directly Targeting FBXW11 and Regulating Wnt Signaling

BACKGROUND AND OBJECTIVES

MicroRNAs play a crucial role in the progression of various cancers, and microRNA-221 (miR-221) has been observed to be significantly overexpressed in osteosarcoma (OS) cells. FBXW11, a vital F-box protein of the ubiquitin-proteasome system, mediates the proliferation and survival of cancer cells by targeting multiple substrates for degradation. FBXW11 inhibits OS growth and metastasis by antagonizing the β-catenin/Wnt signaling pathway. Therefore, we hypothesized that miR-221 targets FBXW11 to mediate Wnt signaling and promote OS proliferation.

METHODS

In this study, we demonstrated the increased expression of miR-221 and FBXW11 in OS tissues and cell lines by real-time polymerase chain reaction (RT-PCR). Moreover, to elucidate the regulatory mechanism(s) of miR-221 and FBXW11 in progression, cell viability and apoptosis were analyzed by the MTT assay and flow cytometry, respectively.

RESULTS

The results showed that the overexpression of miR-221 in OS cells dramatically promoted cell growth and cell cycle progression, and inhibited apoptosis, whereas miR-221 inhibitors conversely inhibited proliferation and promoted apoptosis in OS cells. The data also showed that FBXW11 directly targeted miR-221 and miR-221 regulated OS cell proliferation and apoptosis by binding to FBXW11. We further confirmed that miR-221 targeted FBXW11 to promote proliferation and inhibit apoptosis in OS cell lines by inhibiting Wnt signaling.

INTERPRETATION AND CONCLUSIONS

Overall, our study revealed a functional mechanism for miR-221 in OS. Further studies will elucidate its role in the progression of OS and inhibiting miR-221 may represent a useful treatment strategy.

Confocal Raman microspectroscopic analysis on the time-dependent impact of DAPT, a γ-secretase inhibitor, to osteosarcoma cells

Confocal Raman microspectroscopy (CRM) analysis provides subcellular compositional and morphology related information. In this study, we used CRM in conjunction with multivariate statistical analysis to elucidate the time-dependent impact of the γ-secretase inhibitor, DAPT (N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester) of osteosarcoma (OS) cells. The interactions of DAPT (20 μM) with a murine OS cell line K7M2 at 24 and 48 h were monitored. The spectral characteristics of drug action were identified to illustrate the cellular compositional alterations, showing that DAPT induced apoptosis by reducing the protein, lipid and nucleic acid content and structural changes. Multivariate algorithms, principal component analysis (PCA) and linear discriminant analysis (LDA) revealed a clear separation among cells in the untreated control (UT), 24H (DAPT-treated for 24 h), and 48H (DAPT-treated for 48 h) groups, achieving sensitivities of 100%, 96%, 100% and specificities of 98%, 100%, 100%, respectively. After point-scanned spectral imaging, K-means clustering analysis (KCA) was further used to visualize sub-cellular morphological changes and the underlying spectral characteristics in a temporal sequence. Compared with the UT group, Raman imaging results exhibited gradually increased nuclear division of OS cells with DAPT treatment duration extension, along with changes in the physiology of other organelles within the cell. By providing a unique perspective for understanding the temporary cellular responses to DAPT at molecular level, the achieved results form the foundation of strategies for the application of CRM and other Raman-based techniques for studying the therapeutic responses of other anticancer agents in cancer model systems.

Confocal Raman Spectral Imaging Study of DAPT, a γ-secretase Inhibitor, Induced Physiological and Biochemical Reponses in Osteosarcoma Cells

Confocal Raman microspectral imaging was adopted to elucidate the cellular drug responses of osteosarcoma cells (OC) to N-[N-(3, 5-difluorophenyl acetyl)-L-alanyl]-sphenylglycine butyl ester (DAPT), a γ-secretase inhibitor, by identifying the drug induced subcellular compositional and structural changes. Methods: Spectral information were acquired from cultured osteosarcoma cells treated with 0 (Untreated Group, UT), 10 (10 μM DAPT treated, 10T), 20 μM (20 μM DAPT treated, 20T) DAPT for 24 hours. A one-way ANOVA and Tukey's honest significant difference (HSD) post hoc multiple test were sequentially applied to address spectral features among three groups. Multivariate algorithms such as K-means clustering analysis (KCA) and Principal component analysis (PCA) were used to highlight the structural and compositional differences, while, univariate imaging was applied to illustrate the distribution pattern of certain cellular components after drug treatment. Results: Major biochemical changes in DAPT-induced apoptosis came from changes in the content and structure of proteins, lipids, and nucleic acids. By adopted multivariate algorithms, the drug induced cellular changes was identified by the morphology and spectral characteristics between untreated cells and treated cells, testified that DAPT mainly acted in the nuclear region. With the increase of the drug concentration, the content of main subcellular compositions, such nucleic acid, protein, and lipid decreased. In an addition, DAPT-induced nuclear fragmentation and apoptosis was depicted by the univariate Raman image of major cellular components (nucleic acids, proteins and lipids). Conclusions: The achieved Raman spectral and imaging results illustrated detailed DAPT-induced subcellular compositional and structural variations as a function of drug dose. Such observations can not only explain drug therapeutic mechanisms of OC DAPT treatment, and also provide new insights for accessing the medicine curative efficacy and predicting prognosis.

Human adipose-derived stem cells loaded with drug-coated magnetic nanoparticles for in-vitro tumor cells targeting

Magnetic nanoparticles (MNPs) functionalized with different therapeutics delivered by mesenchymal stem cells represent a promising approach to improve the typical drug delivery methods. This innovative method, based on the "Trojan horse" principle, faces however important challenges related to the viability of the MNPs-loaded cells and drug stability. In the present study we report about an in vitro model of adipose-derived stem cells (ADSCs) loaded with palmitate-coated MNPs (MNPsPA) as antitumor drug carriers targeting a 3D tissue-like osteosarcoma cells. Cell viability, MNPsPA-drug loading capacity, cell speed, drug release rate, magnetization and zeta potential were determined and analysed. The results revealed that ADSCs loaded with MNPsPA-drug complexes retained their viability at relatively high drug concentrations (up to 1.22 pg antitumor drug/cell for 100% cell viability) and displayed higher speed compared to the targeted tumor cells in vitro. The magnetization of the sterilized MNPsPA complexes was 67 emu/g within a magnetic field corresponding to induction values of clinical MRI devices. ADSCs payload was around 9 pg magnetic material/cell, with an uptake rate of 6.25 fg magnetic material/min/cell. The presented model is a proof-of-concept platform for stem cells-mediated MNPs-drug delivery to solid tumors that could be further correlated with MRI tracking and magnetic hyperthermia for theranostic applications.

Involvement of LPA signaling via LPA receptor-2 in the promotion of malignant properties in osteosarcoma cells

Lysophosphatidic acid (LPA) signaling via G protein-coupled LPA receptors mediates various biological effects in cancer cells. This study aimed to investigate the roles of LPA receptors in the regulation of cellular functions during tumor progression in osteosarcoma cells. Long-term cisplatin (CDDP)-treated MG63-C and MG63-R7-C cells were generated from osteosarcoma MG-63 and highly-migratory MG63-R7 cells, respectively. LPAR2 and LPAR3 expression levels were significantly higher in MG63-C cells than in MG-63 cells, while LPAR1 expression was reduced. MG63-C cells were highly motile, compared with MG-63 cells. MG63-C cell motility was suppressed by LPA₂ knockdown and enhanced by the LPA₁/LPA₃ antagonist, dioctanoylglycerol pyrophosphate. LPAR2 and LPAR3 expression levels were significantly elevated in MG63-R7-C cells in comparison with MG63-R7 cells. MG63-R7-C cells were found to be highly invasive, correlating with metalloproteinase-2 activation. MG63-R7-C cells formed large colonies, whereas colony formation was absent from MG63-R7 cells. Notably, MG63-R7-C cell activities were inhibited by LPA₂ knockdown. These results suggest that LPA signaling via LPA₂ plays an important role in the acquisition of malignant properties during tumor progression in MG-63 cells.

JPH203, a selective L-type amino acid transporter 1 inhibitor, induces mitochondria-dependent apoptosis in Saos2 human osteosarcoma cells

Most normal cells express L-type amino acid transporter 2 (LAT2). However, L-type amino acid transporter 1 (LAT1) is highly expressed in many tumor cells and presumed to support their increased growth and proliferation. This study examined the effects of JPH203, a selective LAT1 inhibitor, on cell growth and its mechanism for cell death in Saos2 human osteosarcoma cells. FOB human osteoblastic cells and Saos2 cells expressed LAT1 and LAT2 together with their associating protein 4F2 heavy chain, but the expression of LAT2 in the Saos2 cells was especially weak. JPH203 and BCH, a non-selective L-type amino acid transporter inhibitor, potently inhibited L-leucine uptake in Saos2 cells. As expected, the intrinsic ability of JPH203 to inhibit L-leucine uptake was far more efficient than that of BCH in Saos2 cells. Likewise, JPH203 and BCH inhibited Saos2 cell growth with JPH203 being superior to BCH in this regard. Furthermore, JPH203 increased apoptosis rates and formed DNA ladder in Saos2 cells. Moreover, JPH203 activated the mitochondria-dependent apoptotic signaling pathway by upregulating pro-apoptotic factors, such as Bad, Bax, and Bak, and the active form of caspase-9, and downregulating anti-apoptotic factors, such as Bcl-2 and Bcl-xL. These results suggest that the inhibition of LAT1 activity via JPH203, which may act as a potential novel anti-cancer agent, leads to apoptosis mediated by the mitochondria-dependent intrinsic apoptotic signaling pathway by inducing the intracellular depletion of neutral amino acids essential for cell growth in Saos2 human osteosarcoma cells.

miR-214 modulates cisplatin sensitivity of osteosarcoma cells through regulation of anaerobic glycolysis

Osteosarcoma is the most frequent primary bone tumor originating from adolescents and young adults. Despite improvements in the chemo- or radio- therapy of osteosarcoma patients, survival rate has not increased and drug resistance becomes a major factor that limits the effectiveness. Therefore, investigation of new treatment modalities is urgently required to optimize therapeutic options. Our previous study described an oncogenic role of miR-214 through promotion of osteosarcoma cells proliferation. In this study, we report miR-214 contributes to cisplatin resistance in osteosarcoma cells. Overexpression of miR-214 decreased the cisplatin sensitivity. By establishing an osteosarcoma cisplatin resistant cell line, we find miR-214 is significantly upregulated in cisplatin resistant cells. Moreover, we show miR-214 promotes anaerobic glycolysis rates of osteosarcoma cells but suppresses mitochondrial oxidative phosphorylation. Consistently, cisplatin resistant cells exhibit upregulated glycolysis but decreased mitochondrial oxidative phosphorylation, a phenotype called "Warburg effect". Finally, we demonstrate inhibition of glycolysis by either glycolysis inhibitor or miR-214 inhibition significantly re-sensitizes cisplatin resistant osteosarcoma cells. In summary, this study illustrates a miRNA-involved chemosensitivity of osteosarcoma and will contribute to the developments of therapeutic agents for the anti-chemoresistance treatments.

Combining 2D angiogenesis and 3D osteosarcoma microtissues to improve vascularization

Angiogenesis is now well known for being involved in tumor progression, aggressiveness, emergence of metastases, and also resistance to cancer therapies. In this study, to better mimic tumor angiogenesis encountered in vivo, we used 3D culture of osteosarcoma cells (MG-63) that we deposited on 2D endothelial cells (HUVEC) grown in monolayer. We report that endothelial cells combined with tumor cells were able to form a well-organized network, and that tubule-like structures corresponding to new vessels infiltrate tumor spheroids. These vessels presented a lumen and expressed specific markers as CD31 and collagen IV. The combination of 2D endothelial cells and 3D microtissues of tumor cells also increased expression of angiogenic factors as VEGF, CXCR4 and ICAM1. The cell environment is the key point to develop tumor vascularization in vitro and to be closer to tumor encountered in vivo.

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.

Characterization and cytotoxic effect of aqua-(2,2',2''-nitrilotriacetato)-oxo-vanadium salts on human osteosarcoma cells

The use of protonated N-heterocyclic compound, i.e. 2,2'-bipyridinium cation, [bpyH+], enabled to obtain the new nitrilotriacetate oxidovanadium(IV) salt of the stoichiometry [bpyH][VO(nta)(H2O)]H2O. The X-ray measurements have revealed that the compound comprises the discrete mononuclear [VO(nta)(H2O)]- coordination ion that can be rarely found among other known compounds containing nitrilotriacetate oxidovanadium(IV) moieties. The antitumor activity of [bpyH][VO(nta)(H2O)]H2O and its phenanthroline analogue, [phenH][VO(nta)(H2O)](H2O)0.5, towards human osteosarcoma cell lines (MG-63 and HOS) has been assessed (the LDH and BrdU tests) and referred to cis-Pt(NH3)2Cl2 (used as a positive control). The compounds exert a stronger cytotoxic effect on MG-63 and HOS cells than in untransformed human osteoblast cell line. Thus, the [VO(nta)(H2O)]- containing coordination compounds can be considered as possible antitumor agents in the osteosarcoma model of bone-related cells in culture.

Prevention of tumour cell apoptosis associated with sustained protein kinase B phosphorylation is more sensitive to regulation by insulin signalling than stimulation of proliferation and extracellular signal-regulated kinase

Insulin controls blood glucose while insulin-like growth factor (IGF) 1 is an important growth factor. Interestingly, both hormones have overlapping bioactivities and can activate the same intracellular signal transduction cascades. Growth control (mainly by IGF1) and metabolic function (predominantly by insulin) are believed to depend on activation of extracellular signal-regulated kinases (ERKs) 1/2 and protein kinase B (Akt/PKB), respectively. Therefore, insulin analogues that are used to normalize blood glucose are tested for their ability to preferentially activate Akt/PKB but not ERK1/2 and mitogenesis. Growth hormone, IGF1, and hyperinsulinemia are associated with increased risk of growth progression of some cancer types. To test if continuous exposure to insulin can favour tumour growth, we studied insulin/IGF1-dependent activation of ERK1/2 and Akt/PKB by Western blotting, inhibition of apoptosis by ELISA, and induction of proliferation by [³H]-thymidine incorporation in Saos-2/B10 osteosarcoma cells. IGF1 and insulin both induced proliferation and prevented apoptosis effectively. Regulation of apoptosis was far more sensitive than regulation of proliferation. IGF1 and insulin activated PKB (Akt/PKB) rapidly and consistently maintained its phosphorylation. Activation of ERK1/2 was only observed in response to IGF1. Loss of p-Akt/PKB (but not of p-ERK1/2) was associated with increased apoptosis, and protection from apoptosis was lost when activation of Akt/PKB was inhibited. These findings in Saos-2/B10 cells were also replicated in the A549 cell line, originally derived from a human lung carcinoma. Therefore, IGF1 and insulin more likely (at lower concentrations) enhance tumour cell survival than proliferation, via activation and maintenance of phosphatidylinositol 3-kinase activity and p-Akt/PKB.

The effect and mechanism of dopamine D1 receptors on the proliferation of osteosarcoma cells

The physiological and pathological roles of dopamine D1 receptors (DR1) in the regulation of functions in tissues and organs have been recognized. However, whether DR1 are expressed in the osteosarcoma cells and inhibit the proliferation of these cells is unknown. In the present study, we found that DR1 were expressed in the osteosarcoma cells (OS732 cells). SKF-38393 (DR1 agonist) and the overexpression of DR1 decreased the proliferation of OS732 cells; SCH-23390 (DR1 antagonist) and the knockdown of DR1 increased the proliferation of OS732 cells, and both SCH-23390 and the knockdown of DR1 abolished the effect of SKF-38393 on the proliferation of OS732 cells. In addition, SKF-38393 down-regulated the phosphorylation of ERK1/2, PI3K, and Akt; SCH-23390 up-regulated the phosphorylation of ERK1/2, PI3K, and Akt, and SCH-23390 cancelled the effect of SKF-38393. The effect of SKF-38393 on the phosphorylation of ERK1/2, PI3K, and Akt and the proliferation of OS732 cells was similar to PD98059 (an ERK inhibitor) or LY294002 (a PI3K inhibitor), respectively. In conclusion, our results suggest that DR1 are expressed in the osteosarcoma cells and inhibit the proliferation of osteosarcoma cells by the down-regulation of the ERK1/2 and PI3K-Akt pathways. These findings provide a novel target for the treatment of the osteosarcoma.

Different effects of G-protein-coupled receptor 120 (GPR120) and GPR40 on cell motile activity of highly migratory osteosarcoma cells

G-protein-coupled receptor 120 (GPR120) and GPR40 are members of free fatty acid (FFA) receptors and mediate a variety of biological responses through binding of medium- and long-chain FFAs. Recently, it has been reported that GPR120 and GPR40 regulated cellular functions of cancer cells. In the present study, to assess whether GPR120 and GPR40 are involved in the enhancement of cell motile activity of osteosarcoma cells, we established highly migratory (MG63-R7) cells from osteosarcoma MG-63 cells. The expression level of GPR120 gene was significantly higher in MG63-R7 cells than in MG-63 cells, while no change of GPR40 expression was observed. In cell motility assay, the cell motile activity of MG63-R7 cells was approximately 200 times higher than that of MG-63 cells. The cell motile activity of MG63-R7 cells was stimulated by GW9508, which is an agonist of GPR120 and GPR40. Moreover, a GPR40 antagonist GW1100 elevated the cell motile activity of MG63-R7 cells in the presence of GW9508. To confirm the effects of GPR120 and GPR40 on the cell motile activity of MG63-R7 cells, GPR120 knockdown cells were generated from MG63-R7 cells. The cell motile activity of MG63-R7 cells was markedly suppressed by GPR120 knockdown. These results indicated that GPR120 enhanced and GPR40 inhibited the cell motile activity of highly migratory osteosarcoma cells.

WT1 is involved in the Akt-JNK pathway dependent autophagy through directly regulating Gas1 expression in human osteosarcoma cells

Macroautophagy (herein termed autophagy) works as a protective mechanism in tumorigenesis and development under metabolic stress condition. Multitudes of genes have been found involved in this process during past decades. In the present study, we report that Wilm's tumor suppressor1 (WT1) is involved in autophagy in osteosarcoma (OS) cells. WT1, a transcription factor with multitude of target genes, expresses in a majority of cancer types. Though wide-ranging effect of WT1 is now well documented, the function of WT1 in tumors remains poorly defined. In this chapter, it is found that high expression of WT1 positively correlates with active autophagy in human osteosarcoma cells. And further study on cell signaling pathway illustrates that Akt/JNK pathway acts as a positive regulator of autophagy induced by WT1. Here, we present evidence that WT1 modulates Akt/JNK signaling pathway mediated autophagy by controlling the expression of growth arrest-specific 1 (Gas1). We show that WT1 is required for Gas1 transcription in osteosarcoma cells. And Gas1 is upregulated followed WT1 overexpression in a time-dependent manner. Loss of Gas1 results in a reduction of WT1-induced autophagy.

Prednisolone inhibits SaOS2 osteosarcoma cell proliferation by activating inducible nitric oxide synthase

AIM: To investigate the effect of prednisolone, a synthetic glucocorticoid used in inflammatory diseases, on the growth of cultured osteosarcoma cells.

METHODS: Two osteosarcoma cell lines with different degree of differentiation were used. SaOS2 show a rather mature phenotype, while U2OS are negative for almost all osteoblastic markers. The cells were exposed to different concentrations of prednisolone (1-9 μmol/L) with or without antioxidants or the inhibitor of inducible nitric oxide synthase (iNOS) l-N⁶-(iminoethyl)-lysine-HCl (L-NIL). Cell growth was assessed by counting viable cells. The production of nitric oxide (NO) was measured in the conditioned media by the Griess method. The production of reactive oxygen species was quantified using 2’-7’-dichlorofluorescein diacetate. Western blot with specific antibodies against NOSs was performed on cell extracts.

RESULTS: Prednisolone inhibited SaOS2 cell growth in a dose dependent manner. No significant effects were observed in U2OS. The inhibition of SaOS2 growth is not due to oxidative stress, because antioxidants do not rescue cell proliferation. Since high concentrations of NO inhibit bone formation, we also measured NO and found it induced in SaOS2, but not in U2OS, exposed to prednisolone, because of the upregulation of iNOS as detected by western blot. Therefore, we treated SaOS2 with prednisolone in the presence or in the absence of L-NIL. L-NIL prevented NO release induced by prednisolone at all the concentrations apart from 9 μmol/L. At the same concentrations, we found that L-NIL rescued SaOS2 growth after exposure to prednisolone. In U2OS cells, prednisolone did not induce NO production nor affected cell growth. All together, these data indicate that a link exists between increased amounts of NO and growth inhibition in response to prednisolone in SaOS2.

CONCLUSION: Prednisolone inhibited SaOS2 proliferation by increasing the release of NO through the upregulation of iNOS, while no effect was exerted on U2OS.

Hypoxia promotes drug resistance in osteosarcoma cells via activating AMP-activated protein kinase (AMPK) signaling

Purpose

Drug resistance has been recognized to be a major obstacle to the chemotherapy for osteosarcoma. And the potential importance of hypoxia as a target to reverse drug resistance in osteosarcoma has been indicated, though the mechanism underlining such role is not clarified. The present study aims to investigate the role of hypoxia in the drug resistance in osteosarcoma cells via activating AMP-activated protein kinase (AMPK) signaling.

Experimental design

We investigated the promotion of the resistance to doxorubicin of osteosarcoma MG-63 and U2-os cells in vitro, and then determined the role of hypoxia-inducible factor-1 (HIF-1)α and HIF-1β, the activation and regulatory role of AMPK in the osteosarcoma U2-os cells which were treated with doxorubicin under hypoxia.

Results

It was demonstrated that hypoxia significantly reduced the sensitivity of MG-63 and U2-os cells to doxorubicin, indicating an inhibited viability reduction and a reduced apoptosis promotion. And such reduced sensitivity was not associated with HIF-1α, though it was promoted by hypoxia in U2-os cells. Interestingly, the AMPK signaling was significantly promoted by hypoxia in the doxorubicin-treated U2-os cells, with a marked upregulation of phosphorylated AMPK (Thr 172) and phosphorylated acetyl-CoA carboxylase (ACC) (Ser 79), which were sensitive to the AMPK activator, AICAR and the AMPK inhibitor, Compound C. Moreover, the promoted AMPK activity by AICAR or the downregulated AMPK activity by Compound C significantly reduced or promoted the sensitivity of U2-os cells to doxorubicin.

Conclusion

The present study confirmed the AMPK signaling activation in the doxorubicin-treated osteosarcoma cells, in response to hypoxia, and the chemical upregulation or downregulation of AMPK signaling reduced or increased the chemo-sensitivity of osteosarcoma U2-os cells in vitro. Our study implies that AMPK inhibition might be a effective strategy to sensitize osteocarcoma cells to chemotherapy.

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AMPK signaling is activated by hypoxia in the doxorubicin-treated osteosarcoma cells.

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Chemical upregulation of AMPK desensitizes osteosarcoma U2-os cells to doxorubicin.

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AMPK inhibition sensitizes osteosarcoma U2-os cells to doxorubicin.

Genome-wide gene expression profiling of low-dose, long-term exposure of human osteosarcoma cells to bisphenol A and its analogs bisphenols AF and S

The bisphenols AF (BPAF) and S (BPS) are structural analogs of the endocrine disruptor bisphenol A (BPA), and are used in common products as a replacement for BPA. To elucidate genome-wide gene expression responses, estrogen-dependent osteosarcoma cells were cultured with 10 nM BPA, BPAF, or BPS, for 8 h and 3 months. Genome-wide gene expression was analyzed using the Illumina Expression BeadChip. Three months exposure had significant effects on gene expression, particularly for BPS, followed by BPAF and BPA, according to the number of differentially expressed genes (1980, 778, 60, respectively), the magnitude of changes in gene expression, and the number of enriched biological processes (800, 415, 33, respectively) and pathways (77, 52, 6, respectively). 'Embryonic skeletal system development' was the most enriched bone-related process, which was affected only by BPAF and BPS. Interestingly, all three bisphenols showed highest down-regulation of genes related to the cardiovascular system (e.g., NPPB, NPR3, TXNIP). BPA only and BPA/BPAF/BPS also affected genes related to the immune system and fetal development, respectively. For BPAF and BPS, the 'isoprenoid biosynthetic process' was enriched (up-regulated genes: HMGCS1, PDSS1, ACAT2, RCE1, DHDDS). Compared to BPA, BPAF and BPS had more effects on gene expression after long-term exposure. These findings stress the need for careful toxicological characterization of BPA analogs in the future.

Molecular mechanisms of luteolin induced growth inhibition and apoptosis of human osteosarcoma cells

Luteolin is a flavone in medicinal plants as well as some vegetables and spices. It is a natural anti-oxidant with less pro-oxidant potential but apparently with a better safety profile. The purpose of this study was to investigate the molecular mechanism of luteolin-mediated apoptosis of MG-63 human osteosarcoma cells. MTT assay kit was employed to evaluate the effects of luteolin on MG-63 cells proliferation. Then, we performed Annexin V-FITC/PI to analyze the apoptotic rate of the cells. Furthermore, the inhibitory effects of luteolin on the expressions of BCL-2, BAX, Caspase-3 and Survivin were detected by Western blotting. As expected, luteolin (0.5, 2.5, 12.5 µg/mL) inhibited the growth of MG-63 cells by inhibiting cell proliferation and inducing cell apoptosis. Western blotting demonstrated that luteolin (0.5, 2.5, 12.5 µg/mL) inhibited the expressions of BCL-2, Caspase-3 and Survivin, and promoted the expression of BAX in MG-63 cells with a concentration dependent way. Luteolin can inhibit osteosarcoma cell proliferation and induce apoptosis effectively in a dose dependent manner through down-regulating the expression of BCL-2, Caspase-3 and Survivin proteins levels and up-regulating the expression of BAX protein level. These findings indicated that luteolin may be used as a novel herbal medicine for the treatment of osteosarcoma.

Exosome-formed synthetic microRNA-143 is transferred to osteosarcoma cells and inhibits their migration

MicroRNAs (miRNAs) have emerged as potential anticancer agents, but their clinical application is limited by the lack of an effective delivery system to tumors. Exosomes are small vesicles that play important roles in intercellular communication. Here, we show that synthetic miR-143 introduced into cells is released enveloped in exosomes and that the secreted exosome-formed miR-143 is transferred to osteosarcoma cells. The delivery of exosome-formed miR-143 significantly reduced the migration of osteosarcoma cells. The delivery efficiency of exosome-formed miR-143 was less than that achieved with lipofection, but the migratory potential of osteosarcoma cells was similarly inhibited after both strategies. Our results suggest that exosomes can deliver synthetic miR-143 and are a potentially efficient and functional delivery system.

A study on anticancer activity of Caulis Spatholobi extract on human osteosarcoma Saos-2 cells

The objective of the present study was to investigate the anticancer activity of Chinese medicine Caulis Spatholobi extract on multicentric osteosarcoma cells. Ultraviolet spectrophotometry was used to determine the total flavonoid content in each sample; vanillin sulphuric acid assay was used to determine the condensed tannin content in each sample; and the varying degrees of inhibitory activities of ethanol, ethyl acetate and n-butanol extracts of Caulis Spatholobi on human osteosarcoma Saos-2 cells were studied. The results showed that the inhibitory activity of ethyl acetate extract was the highest among the four extracts. The condensed tannin contents of 1.2 mg/mL Caulis Spatholobi water extract, ethanol extract, ethyl acetate extract and petroleum ether extract were 26.23%, 48.36%, 70.18% and 40.51% respectively; and condensed tannin content of 1.5 mg/mL Caulis Spatholobi water extract, ethanol extract, ethyl acetate extract and petroleum ether extract were 4.15%, 5.81%, 8.76% and 7.30% respectively.