u-0126 and Osteosarcoma

The mechanism for icaritin to improve postmenopausal osteoporosis (PMOP) has not been clarified. The aim of this study was to investigate the role of estrogen receptor α36 (ERα36) in the proliferation promotion and anti-apoptosis effects of icaritin on osteoblasts and the underlying mechanism of downstream signal transduction. The ERα36 knockdown human osteosarcoma MG63 cell model was constructed by transfection of shRNA vector. Cell proliferation was detected by CCK-8, the apoptosis was detected by flow cytometry, and the activation of ERK and AKT signaling pathways was detected by Western blot. The results showed that the effects of icaritin on the proliferation and apoptosis of MG63 cells were significantly decreased after ERα36 knockdown, and icaritin could up-regulate the levels of ERK and AKT phosphorylation in MG63 cells, which could be reduced by ERα36 knockdown. The effect of icaritin on the proliferation of MG63 cells was significantly decreased by pretreating the cells with U0126 (an ERK signaling pathway blocker) and LY294002 (an AKT signaling pathway blocker), respectively. Furthermore, anti-apoptotic effect of icaritin on MG63 cells was significantly decreased after the cells were pretreated with U0126, but not with LY294002. These results suggest that icaritin exerts proliferation promotion and anti-apoptosis effects on osteoblasts through ERα36 and its downstream ERK and AKT signaling pathways.

Topics: Apoptosis; Butadienes; Cell Line, Tumor; Cell Proliferation; Chromones; Flavonoids; Humans; Morpholines; Nitriles; Osteosarcoma; Phosphorylation; Receptors, Estrogen; Signal Transduction; Up-Regulation

Nutlin-3 is a small-molecule antagonist of murine double minute 2 (MDM2) that blocks its binding to p53, leading to an increase in p53 protein levels. The tumor suppressor p53 induces growth arrest or apoptosis in response to genotoxic stress. Along with its growth-suppressive effect, it has been reported that p53 stimulates the mitogen-activated protein kinase (MAPK) pathway via the upregulation of heparin- binding epidermal growth factor-like growth factor (HB-EGF), an epidermal growth factor receptor (EGFR) ligand, and discoidin domain receptor 1 (DDR1), a tyrosine kinase receptor, at the transcription level. In this study, we propose a novel mechanism involved in the p53-induced MAPK activation. Nutlin-3 induced the phosphorylation of EGFR, MAPK/ERK kinase (MEK)1/2 and extracellular signal-regulated kinase (ERK)1/2 in U2OS human osteosarcoma cells harboring wild-type p53. This phosphorylation was completely inhibited by p53 siRNA, but not by pifithrin (PFT)-α, an inhibitor of the trans-criptional activity of p53. While the nutlin-3-induced EGFR phosphorylation was prevented by the inactivation of ERK1/2, the nutlin-3-induced MEK1/2-ERK1/2 phosphorylation was still observed in the cells in which EGFR phosphorylation was inhibited using EGFR siRNA and AG1478, an inhibitor of EGFR tyrosine kinase. Of note, nutlin-3 caused the accumulation of mitochondrial reactive oxygen species (ROS) and this correlated with the mitochondrial translocation of p53. 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO), a ROS scavenger, prevented the phosphorylation of ERK1/2. PFT-μ, which prevented the mitochondrial localization of p53, suppressed ERK1/2 phosphorylation, as well as ROS accumulation. Finally, we analyzed the effect of ERK1/2 activation on nutlin-3-induced apoptosis. The knockdown of MEK1/2 and ERK1/2 activity using U0126, a MEK inhibitor, or siRNAs, resulted in the enhancement of nutlin-3-induced apoptosis. In addition, TEMPO and PFT-μ also promoted nutlin-3-induced apoptosis. Taking the above findings into account, it can be concluded that nutlin-3 activates ERK1/2 prior to EGFR phosphorylation via ROS generation following the mitochondrial translocation of p53 and that nutlin-3-induced ERK1/2 activation may play a role in protecting U2OS cells from p53-dependent apoptosis, constituting a negative feedback loop for p53-induced apoptosis.

Topics: Antioxidants; Apoptosis; Benzothiazoles; Butadienes; Cell Line, Tumor; Cyclic N-Oxides; Enzyme Activation; Enzyme Inhibitors; ErbB Receptors; Humans; Imidazoles; MAP Kinase Kinase 1; MAP Kinase Kinase 2; Mitochondria; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Osteosarcoma; Phosphorylation; Piperazines; Protein Transport; Quinazolines; Reactive Oxygen Species; RNA Interference; RNA, Small Interfering; Toluene; Tumor Suppressor Protein p53; Tyrphostins

Expression of mitogen-activated protein kinase (MAPK) signaling and its role in cell proliferation of the bone malignancies, osteosarcoma (OS) and malignant fibrous histiocytoma (MFH) were investigated.. Gene expression and protein levels of RAF1 and MEK1/2 in 6 human sarcoma cell lines and 7 surgically obtained OS specimens were assessed by RT-PCR and immunohistochemistry, respectively. MEK inhibitor, U0126 [1,4-diamino-2,3-dicyano-1,4-bis (2-aminophynyltio) butadiene], was used for cell proliferation assays.. RAF1 and MEK 1/2 mRNA was detected in all cell lines and OS specimens. RAF1, MEK 1/2 and p-MEK protein was also expressed in the cells, as was MEK1/2 in OS specimens. Treatment with U0126 resulted in dose- and time-dependent inhibition of cell proliferation and suppression of p-ERK expression, opposite to promotion of p-MEK.. U0126 blocks MAPK signaling and decreases cell proliferation in OS and MFH. Thus, selective MAPK inhibitors might be therapeutically advantageous in the treatment of bone and soft tissue sarcomas.

Topics: Blotting, Western; Bone Neoplasms; Butadienes; Cell Growth Processes; Cell Line, Tumor; Dose-Response Relationship, Drug; Histiocytoma, Malignant Fibrous; Humans; Immunohistochemistry; MAP Kinase Kinase 1; MAP Kinase Kinase 2; MAP Kinase Signaling System; Nitriles; Osteosarcoma; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-raf; RNA, Messenger

Inducible nitric oxide synthase (NOS2) is over-expressed in a number of tumors and implicated in tumor growth and metastasis. Murine FBJ osteosarcoma-derived FBJ-S1 cells are poorly metastatic and express the ganglioside GD1a, whereas highly metastatic FBJ-LL cells only slightly express this ganglioside. The present study demonstrates that NOS2 is more highly expressed in FBJ-LL cells compared to FBJ-S1 cells. By manipulating GM2/GD2 synthase expression or adding exogenous GD1a, GD1a inversely regulated NOS2 at the transcriptional level. GT1b suppressed NOS2 to the same extent as GD1a. Silencing NOS2 inhibited proliferation, migration, and anchorage-independent growth of FBJ-LL cells, suggesting that the metastatic properties of FBJ-LL cells are associated with NOS2. MEK1/2 inhibitor (U0126) increased NOS2 expression, whereas GD1a treatment decreased it. Co-treating the cells with GD1a and U0126 blocked the inhibition of NOS2 expression, suggesting that the GD1a signal is mediated by ERK1/2. NOS2 expression increased when ERK1, but not ERK2, was silenced, and GD1a did not suppress NOS2 expression in cells treated with another MEK1/2 inhibitor PD98059, suggesting that ERK1 phosphorylation is indispensable for the GD1a signal suppressing NOS2.

Topics: Animals; Blotting, Western; Butadienes; Cell Line, Tumor; Cell Movement; Cell Proliferation; Enzyme Inhibitors; Flavonoids; Gangliosides; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Mice; Mice, Inbred BALB C; Mitogen-Activated Protein Kinase 3; Nitric Oxide Synthase Type II; Nitriles; Osteosarcoma; Phosphorylation; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Signal Transduction

Insulin-like growth factor-I (IGF-I) promotes bone formation by stimulating proliferation and differentiation of osteoblasts. Bone sialoprotein (BSP), is thought to function in the initial mineralization of bone, is selectively expressed by differentiated osteoblast. To determine the molecular mechanism of IGF-I regulation of osteogenesis, we analyzed the effects of IGF-I on the expression of BSP in osteoblast-like Saos2 and in rat stromal bone marrow (RBMC-D8) cells. IGF-I (50 ng/ml) increased BSP mRNA levels at 12 h in Saos2 cells. In RBMC-D8 cells, IGF-I increased BSP mRNA levels at 3 h. From transient transfection assays, a twofold increase in transcription by IGF-I was observed at 12 h in pLUC3 construct that included the promoter sequence from -116 to +60. Effect of IGF-I was abrogated by 2-bp mutations in either the FGF2 response element (FRE) or homeodomain protein-binding site (HOX). Gel shift analyses showed that IGF-I increased binding of nuclear proteins to the FRE and HOX elements. Notably, the HOX-protein complex was supershifted by Smad1 antibody, while the FRE-protein complex was shifted by Smad1 and Cbfa1 antibodies. Dlx2 and Dlx5 antibodies disrupted the formation of the FRE- and HOX-protein complexes. The IGF-I effects on the formation of FRE-protein complexes were abolished by tyrosine kinase inhibitor herbimycin A (HA), PI3-kinase/Akt inhibitor LY249002, and MAP kinase kinase inhibitor U0126, while IGF-I effects on HOX-protein complexes were abolished by HA and LY249002. These studies demonstrate that IGF-I stimulates BSP transcription by targeting the FRE and HOX elements in the proximal promoter of BSP gene.

Topics: Animals; Benzoquinones; Binding Sites; Bone Marrow Cells; Butadienes; Cell Culture Techniques; Cell Line, Tumor; Clone Cells; Enzyme Inhibitors; Fibroblast Growth Factor 2; Homeodomain Proteins; Humans; Insulin-Like Growth Factor I; Integrin-Binding Sialoprotein; Lactams, Macrocyclic; Mutation; Nitriles; Osteosarcoma; Promoter Regions, Genetic; Quinones; Rats; Response Elements; Rifabutin; RNA, Messenger; Sialoglycoproteins; Transcription, Genetic

Recently, evidences have shown that tissue type plasminogen activator (t-PA) may play an important role in the pathogenesis of periodontal diseases. However, the mechanisms and signal transduction pathways involved in the production of t-PA in human osteosarcoma cells are not fully understood.. The purpose of this study was to investigate the caseinolytic activity in human osteosarcoma cell line U2OS cells stimulated with interleukin-1alpha (IL-1alpha) or Porphyromonas gingivalis in the absence or presence of p38 inhibitor SB203580, mitogen-activated protein kinase kinase (MEK) inhibitor U0126, and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002.. IL-1alpha and the supernatants of P. gingivalis were used to evaluate the caseinolytic activity in U2OS cells by using casein zymography and enzyme-linked immunosorbent assay (ELISA). Furthermore, to search possible signal transduction pathways, SB203580, U0126, and LY294002 were added to test how they modulated the caseinolytic activity.. Casein zymography exhibited a caseinolytic band with a molecular weight of approximately 70 kDa, suggestive of the presence of t-PA. Secretion of t-PA was found to be stimulated with IL-1alpha and P. gingivalis during a 2-day culture period (p < 0.05). From the results of casein zymography and ELISA, SB203580, U0126, and LY294002 significantly reduced the IL-1alpha or P. gingivalis-stimulated t-PA production, respectively (p < 0.05).. Our findings demonstrated that IL-1alpha and P. gingivalis enhance t-PA production in human osteosarcoma cells, and that the signal transduction pathways p38, MEK, and PI3K are involved in the inhibition of t-PA. SB203580, U0126, and LY294002 suppress t-PA production and/or activity and may therefore be valuable therapeutics in t-PA-mediated periodontal destruction, and might be proved clinically useful agents, in combination with standard treatment modalities, in the treatment of periodontitis.

Topics: Butadienes; Caseins; Cell Line, Tumor; Chromones; Culture Media, Conditioned; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Humans; Imidazoles; Interleukin-1alpha; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; Morpholines; Nitriles; Osteosarcoma; p38 Mitogen-Activated Protein Kinases; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Porphyromonas gingivalis; Pyridines; Tissue Plasminogen Activator; Up-Regulation

The effects of OSM on proliferation and differentiation of osteosarcoma and nontransformed osteoblasts were analyzed. OSM downregulates osteoblast markers but induces the glial fibrillary acidic protein by the combined activation of PKCdelta and STAT3, offering new lines of therapeutic investigations.. Oncostatin M (OSM) is a multifunctional cytokine of the interleukin-6 family implicated in embryonic development, differentiation, inflammation, and regeneration of various tissues, mainly the liver, bone, and the central nervous and hematopoietic systems. One particularity of OSM relies on its growth inhibitory and pro-differentiating effects on a variety of tumor cell lines such as melanoma, providing arguments for a therapeutic application of OSM. The objective of this study was to analyze the effects of OSM on osteosarcoma cell lines proliferation and differentiation.. Proliferation was analyzed by 3H thymidine incorporation. Differentiation was analyzed by semiquantitative RT-PCR and immunocytochemistry for various markers. Alizarin red S staining was used to evaluate bone nodule formation. Morphological changes were studied by confocal and electron microscopy. Western blotting, kinases inhibitors, and dominant negative STAT3 were used to identified the signaling pathways implicated.. OSM inhibits the growth of rat osteosarcoma cell lines as well as normal osteoblasts, in correlation with induction of the cyclin-dependent kinases inhibitor p21WAF1. However, OSM reduces osteoblast markers such as alkaline phosphatase, osteocalcin, and bone sialoprotein, leading to strong inhibition of mineralized nodule formation. This inhibitory effect is restricted to mature osteoblasts and differentiated osteosarcoma because OSM effectively stimulates osteoblast markers and bone nodule formation in early, but not late, bone marrow mesenchymal stem cell (BMSC) cultures. In osteosarcoma cells or BMSC, OSM induces expression of the glial fibrillary acidic protein (GFAP) as well as morphological and ultrastructural changes, for example, elongated shape and bundles of microfilaments in cell processes. Rottlerin (PKCdelta inhibitor), and to a lesser degree UO126 (MEK/ERK inhibitor), prevents the loss of osteoblastic markers by OSM, whereas dominant negative STAT3 prevents GFAP induction.. These results highlight the particular gene expression profile of OSM-treated osteosarcoma cells and BMSCs, suggesting either a osteocytic or a glial-like phenotype. Together with the implication of PKCdelta, ERK1/2, and STAT3, these results offer new lines of investigations for neural cell transplantation and osteosarcoma therapy.

Topics: Alkaline Phosphatase; Animals; Anthraquinones; Blotting, Western; Bone and Bones; Bone Marrow Cells; Butadienes; Cell Cycle Proteins; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p21; DNA; DNA-Binding Proteins; Dose-Response Relationship, Drug; Down-Regulation; Enzyme Inhibitors; Glial Fibrillary Acidic Protein; Immunohistochemistry; Inflammation; Integrin-Binding Sialoprotein; Interleukin-6; Mesoderm; Microscopy, Confocal; Microscopy, Electron; Models, Biological; Nitriles; Osteoblasts; Osteocalcin; Osteosarcoma; Protein Kinase C; Protein Kinase C-delta; Rats; Regeneration; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sialoglycoproteins; Signal Transduction; STAT3 Transcription Factor; Stem Cells; Thymidine; Time Factors; Trans-Activators; Transfection

Activation of the mitogen-activated protein kinases ERK1/2 by the chemotherapeutic agent cisplatin has been shown to result in either survival or cell death. The downstream mediators of these opposing effects are unknown, as are the upstream signaling molecules. Activation of ERK is required for accumulation and phosphorylation of p53 following cisplatin treatment. We studied the role of ERK activation after cisplatin treatment under p53-negative and p53-positive conditions using a tetracycline-dependent expression vector in Saos-2 osteosarcoma cells. Dose-dependent activation of ERK first occurred 3-6 h after a 2-h cisplatin incubation and declined after 12-24 h in several tumor cell lines. Incubation of cell lines with the MEK1 inhibitors PD98059 or UO126 after, but not during, cisplatin treatment completely inhibited cisplatin-induced activation of ERK. The activation of ERK by cisplatin was inhibited by transient transfection with dominant-negative Ras-N17 in Saos-2 cells. Treatment of cells with PD98059 or UO126 after cisplatin incubation or inhibition of signaling through ERK by tetracycline-regulated expression of dominant-inhibitory ERK enhanced resistance to cisplatin in p53-negative osteosarcoma cells and reduced cisplatin-induced apoptosis. P53 was stabilized and phosphorylated in a MEK1-dependent manner after cisplatin incubation in Kelly neuroblastoma cells. Inhibition of signaling through ERK increased cell survival after cisplatin treatment in these cells as well. Expression of functional p53 did not change the proapoptotic effects of ERK activation in response to cisplatin in Saos-2 cells. Our results suggest that cisplatin-induced activation of ERK is mediated by Ras. ERK activation increased cisplatin-induced cell death independently of p53 in osteosarcoma and neuroblastoma cell lines.

Topics: Antineoplastic Agents; Apoptosis; Bone Neoplasms; Butadienes; Cisplatin; Drug Resistance, Neoplasm; Enzyme Activation; Enzyme Inhibitors; Flavonoids; Genes, p53; Genes, ras; Humans; MAP Kinase Kinase 1; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase Kinases; Neoplasm Proteins; Neuroblastoma; Nitriles; Osteosarcoma; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins p21(ras); Recombinant Fusion Proteins; Tumor Cells, Cultured