Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The maintenance of cell volume involves transduction of a volume-sensing signal into effectors of volume-regulatory transporters. After exposure to anisotonic conditions, cells undergo compensatory volume changes that are mediated by active transport and passive movement of ions and solutes. Intracellular pH (pHi) homeostasis may be compromised during these processes. We have studied pHi and some of the signal transduction mechanisms involved in the regulatory volume decrease (RVD) that occurs after exposure to hypoosmolar conditions in rat osteosarcoma cells, ROS 17/2.8. Cells were loaded with BCECF; pHi and cell volume were estimated by dual excitation ratio fluorimetry. Swelling of cells in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffered hypotonic medium induced a rapid cell swelling followed by an incomplete RVD of approximately 30% in suspended (i.e., round) cells and approximately 60% in attached (i.e., spread) cells that was independent of subpassage number. RVD was inhibited by ouabain, valinomycin, and high external [K+], all of which should reduce the cell membrane electrochemical gradient for K+. Inhibition of RVD was induced also by decreasing intracellular [Ca2+] with BAPTA-AM and by depletion of Cl-, indicating the role of calcium-regulated K+ and Cl- efflux during RVD. Depolymerization of actin filaments by cytochalasin D prolonged the RVD three-fold and nonspecific activation of GTP-binding proteins up-regulated RVD. In attached cells the hypoosmolar-induced swelling caused a large reduction in pHi (approximately 0.7 units), which was sustained as long as cells were in hypoosmotic medium. The reduction of pHi induced by cell swelling was inhibited by Na(+)-free extracellular medium, ouabain, the tyrosine kinase inhibitor genistein, and to a lesser extent by Cl(-)-free medium. However, amiloride failed to inhibit the hypoosmolar-induced reduction of pHi. Collectively these data indicate that RVD of ROS 17/2.8 cells in HEPES-buffered medium is dependent on conductive efflux of K+ and Cl- that is regulated by cell shape, actin, and GTP-binding proteins. The sustained inhibition of pHi homeostasis induced by cell swelling may reflect the existence of cell volume sensing mechanisms that operate through tyrosine kinases to regulate pHi.
 ...
PMID:Regulation of cell volume and intracellular pH in hyposmotically swollen rat osteosarcoma cells. 870 24

Insulin-like growth factor I (IGF-I) stimulates multiplication of the human osteosarcoma cell line, MG-63, by acting through IGF-I receptor. We have characterized IGF-I stimulated phosphorylation of IRS-1, activation of Ras cycle and phosphorylation of c-Jun in this cell line. Serum starved MG-63 cells were (1) IGF-I stimulated and lysates were immunoprecipitated with polyclonal IRS-1 antibody or (2) metabolically labeled with [32P]orthophosphoric acid and then cells were treated with IGF-I. Cell lysates were immunoprecipitated with p21Ras antibody (Y13-259) and bound nucleotides were analysed by thin-layer chromatography. We demonstrated tyrosine phosphorylation of IRS-1/2 immunoprecipitated from MG-63 cells stimulated with IGF-I. We also showed an increased level of GTP in p21Ras immunoprecipitates from IGF-I treated cells. Nuclear extracts prepared from 32P-labeled cells before and after addition of IGF-I were immunoprecipitated with c-Jun antibody. After electrophoresis and autoradiography, phosphorylation of the c-Jun band was seen to be IGF-I independent. Phosphoamino acid analysis of the c-Jun band showed that phosphoserine was the major species.
 ...
PMID:Insulin-like growth factor I activates insulin receptor substrate 1 and Ras in human osteosarcoma cells. 1045 87

Rho, a member of the small GTP-binding proteins, and one of its downstream effectors ROCK (Rho-associated coiled-coil forming protein kinase) play an important role in the invasion of tumor cells. Lysophosphatidic acid (LPA) activates Rho and ROCK and promotes the organization of stress fibers and focal adhesions. However, the effect of LPA on tumor cell invasion is still controversial. In the present study, human osteosarcoma cells treated with a high concentration of LPA (high LPA) showed considerable formation of stress fibers and focal adhesions compared to the cells treated with a low concentration of LPA (low LPA). C3 (inhibitor of Rho) or Y27632 (an inhibitor of ROCK) inhibited the effects of LPA, indicating that LPA activates the Rho-ROCK pathway in the cells. In addition, Rho activation assay showed that the activation level of Rho can be altered by changing the concentration of LPA. Low LPA stimulated the motility and invasion of the cells, while high LPA reduced both. The disruption of extracellular matrix (ECM) by matrix metalloproteinase 2 (MMP2) is also critical for tumor cell invasion. MMP2 is activated by membranous type-1 MMP (MT1-MMP) and type-2 tissue inhibitor of MMP (TIMP2). High LPA suppressed the activation of MMP2 through down-regulation of MT1-MMP and TIMP2. C3 and Y27632 reversed the suppression of the activation of MMP2 and expression of MT1-MMP and TIMP2, suggesting the involvement of the Rho-ROCK pathway in ECM degradation. Tyrosine phosphorylation of focal adhesion kinase (FAK) was also required for the invasion of tumor cells to occur. Low LPA enhanced the tyrosine phosphorylation of FAK whereas high LPA reduced it. In conclusion, we suggest that Rho has a dual effect on the invasion of osteosarcoma cells by modulating the motility, the ability to degrade ECM and tyrosine phosphorylation of FAK.
 ...
PMID:Small GTP-binding protein, Rho, both increased and decreased cellular motility, activation of matrix metalloproteinase 2 and invasion of human osteosarcoma cells. 1134 66

Tissue inhibitors of metalloproteinases-1 (TIMP-1) and TIMP-2 have growth-stimulating activity for a wide range of cell types. Ras, which comprises a family of three members, i.e, Ha-Ras, Ki-Ras, and H-Ras, is known to participate in growth control in all its facets, including cell proliferation, transformation, differentiation, and apoptosis. In this study, we tested the hypothesis that Ras might be involved in the cell growth-promoting activity of TIMPs. Using MG-63 human osteosarcoma cells, we demonstrated that both TIMP-1 and TIMP-2 caused an increase in the Ras-GTP level in a dose-dependent manner. Our previous results indicated that TIMP-1 activity is mediated through the tyrosine kinase (TYK)/mitogen-activated protein kinase (MAPK) pathway. Here, we demonstrated that Ras activation by TIMP-1 was inhibited by a specific TYK inhibitor, herbimycin A, suggesting that the TYK/MAPK signaling pathway was involved in Ras activation by TIMP-1. However, the activation of Ras by TIMP-2 was inhibited by an inhibitor specific for cyclic AMP-dependent protein kinase (PKA), H89, suggesting the involvement of the PKA-mediated pathway. Furthermore, TIMP-2 promoted the formation of a complex between Ras-GTP and phosphoinositide 3-kinase.
 ...
PMID:Both tissue inhibitors of metalloproteinases-1 (TIMP-1) and TIMP-2 activate Ras but through different pathways. 1214 51

The adenylate cyclase (AC)/cyclic AMP (cAMP)/cAMP-dependent protein kinase pathway controls many biological phenomena. The ubiquitin/proteasome system, controlling the levels of many proteins, modulates important cellular processes such as cell cycle and cell growth. Here we describe a novel mechanism for AC regulation by proteasome pathway. Pharmacological inhibition of proteasome function in human osteosarcoma U2OS cells results in up-regulation of AC activity, increase of levels of alpha subunit of heterotrimeric stimulatory GTP-binding proteins (alphas) and, remarkably, also in preventing of beta-adrenergic receptor-mediated down-regulation of alphas protein levels. Accumulation of alphas protein is also accompanied by the appearance of polyubiquitinated alphas species. Our results: (1) identify alphas protein as a novel proteasome substrate in mammalian cells; (2) indicate that proteasome might play a physiological role in controlling AC/cAMP mediated pathways by modulating the levels of Galphas protein; (3) suggest a role for the proteasome also in controlling alphas-mediated signaling pathways other than those affecting AC complex.
 ...
PMID:Adenylate cyclase regulation via proteasome-mediated modulation of Galphas levels. 1533 22

Development of chemotherapy resistance and evasion from apoptosis in osteosarcoma, a primary malignant bone tumor, is often correlated with constitutive nuclear factor-kappaB (NF-kappaB) activation. Here, we investigated the ability of a polyphenolic fraction of green tea (GTP) that has been shown to have antitumor effects on various malignant cell lines to inhibit growth and induce apoptosis in human osteosarcoma SAOS-2 cells. Treatment of SAOS-2 cells with GTP (20-60 microg/ml) resulted in reduced cell proliferation and induction of apoptosis, which correlated with decreased nuclear DNA binding of NF-kappaB/p65 and lowering of NF-kappaB/p65 and p50 levels in the cytoplasm and nucleus. GTP treatment of cells reduced IkappaB-alpha phosphorylation but had no effect on its protein expression. Furthermore, GTP treatment resulted in the inhibition of IKK-alpha and IKK-beta, the upstream kinases that phosphorylate IkappaB-alpha. The increase in apoptosis in SAOS-2 cells was accompanied with decrease in the protein expression of Bcl-2 and concomitant increase in the levels of Bax. GTP treatment of SAOS-2 cells also resulted in significant activation of caspases as was evident by increased levels of cleaved caspase-3 and caspase-8 in these cells. Treatment of SAOS-2 cells with a specific caspase-3 inhibitor Ac-Asp-Glu-Val-Asp-CHO (Ac-DEVD-CHO) and general caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp (OMe)-fluoromethyl ketone (Z-VAD-FMK) rescued SAOS-2 cells from GTP-induced apoptosis. Taken together, these results indicate that GTP is a candidate therapeutic for osteosarcoma that mediates its antiproliferative and apoptotic effects via activation of caspases and inhibition of NF-kappaB.
 ...
PMID:Green tea polyphenols-induced apoptosis in human osteosarcoma SAOS-2 cells involves a caspase-dependent mechanism with downregulation of nuclear factor-kappaB. 1679 29

Osteosarcoma is the most frequent type of primary bone cancer in children and adolescents. These malignant osteoid forming tumors are characterized by their uncontrolled hyperproliferation. Here, we investigate the role of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in the growth of human osteosarcoma. We show that alpha-CaMKII is expressed in human osteosarcoma cell lines and in primary osteosarcoma tissue derived from patients. The pharmacologic inhibition of CaMKII in MG-63 and 143B human osteosarcoma cells by KN-93 resulted in an 80 and 70% decrease in proliferation, respectively, and induced cell cycle arrest in the G(0)/G(1) phase. The in vivo administration of KN-93 to mice xenografted with human osteosarcoma cells significantly decreased intratibial and subcutaneous tumor growth. Mechanistically, KN-93 and alpha-CaMKII siRNA increased p21((CIP/KIP)) gene expression, protein levels, and decreased the phosphorylation of retinoblastoma protein and E2F transactivation. Furthermore, the inhibition of CaMKII decreased membrane-bound Tiam1 and GTP-bound Rac1, which are known to be involved in p21 expression and tumor growth in a variety of solid malignant neoplasms. Our results suggest that CaMKII plays a critical role in the growth of osteosarcoma, and its inhibition could be an attractive therapeutic target to combat conventional high-grade osteosarcoma in children.
 ...
PMID:alpha-CaMKII controls the growth of human osteosarcoma by regulating cell cycle progression. 1763 40

Despite recent improvements in therapeutic management of osteosarcoma, ongoing challenges in improving the response to chemotherapy warrants new strategies still needed to improve overall patient survival. In this study, we investigated in vivo the effects of RAD001 (Everolimus), a new orally available mTOR inhibitor, on the growth of human and mouse osteosarcoma cells either alone or in combination with zoledronate (ZOL), an anti-osteoporotic drug used to treat bone metastases. RAD001 inhibited osteosarcoma cell proliferation in a dose- and time-dependent manner with no modification of cell-cycle distribution. Combination with ZOL augmented this inhibition of cell proliferation, decreasing PI3K/mTOR signaling compared with single treatments. Notably, in contrast to RAD001, ZOL downregulated isoprenylated membrane-bound Ras concomitantly with an increase of nonisoprenylated cytosolic Ras in sensitive and resistant osteosarcoma cell lines to both drugs. Moreover, ZOL and RAD001 synergized to decrease Ras isoprenylation and GTP-bound Ras levels. Further, the drug combination reduced tumor development in two murine models of osteoblastic or osteolytic osteosarcoma. We found that ZOL could reverse RAD001 resistance in osteosarcoma, limiting osteosarcoma cell growth in combination with RAD001. Our findings rationalize further study of the applications of mTOR and mevalonate pathway inhibitors that can limit protein prenylation pathways.
 ...
PMID:Zoledronic acid potentiates mTOR inhibition and abolishes the resistance of osteosarcoma cells to RAD001 (Everolimus): pivotal role of the prenylation process. 2097 12

Osteosarcoma is the most common malignant tumor of the bone. The major cause of death in osteosarcoma is the increase in metastatic potential, and the ezrin expression has been correlated with the metastasis development. Ezrin interacts with RhoGDI by dissociating it from RhoGTPases, which allow GTPases to load with GTP, activate RhoA to increase cell migration, and invasion. RhoGTPases have been found to contribute to pathologic processes including cancer cell migration, invasion, and metastasis and overexpression of either the GTPase itself or some elements of Rho signaling that have been detected in many human tumors, including Rac1 and RhoA. We have analyzed Rac1 and RhoA expression in the osteosarcoma tissues to understand the role of the ezrin-Rho family pathway in osteosarcoma metastatic progression. Moreover, we have blocked the ezrin expression using siRNA assay to investigate a possible correlation with RAC1 and RHOA expression in the osteosarcoma cell lines. Our immunohistochemical data showed that many osteosarcomas presented cytoplasmatic positivity for both Rac1 and RhoA and cases, both ezrin positive than ezrin negative, revealed the protein expression of Rac1 and RhoA. The results obtained by ezrin siRNA transfection showed that ezrin expression in the osteosarcoma cell lines might modulate, mainly, the Rac1 expression. It is possible that the mechanism of cell motility mediated by Rac1 and RhoA is maintained in osteosarcomas, and since the expression of ezrin, Rac1 and RhoA do not correlate with metastatic progression in osteosarcoma. However, osteosarcomas without metastasis displayed a positivity for Rac1 and RhoA expression compared with metastatic osteosarcomas and this could be a protective factor.
...
PMID:Correlation of the Rac1/RhoA pathway with ezrin expression in osteosarcoma. 2461 49

G protein-coupled receptor 56 (GPR56) is an atypical G protein-coupled receptor, with the long extracellular N-terminus. GPR56 can trigger various downstream signaling responsible for cell survival, proliferation, adhesion, and migration. Expression of GPR56 is associated with cell malignant transformation and tumor cell metastasis in several carcinomas such as melanoma and glioma. Osteosarcoma is the most common malignant bone tumor in adolescents and young adults with high metastasis tendency. The overall survival of osteosarcoma is unsatisfied, partially due to the lacking of predictive markers for metastasis and overall prognosis. This study aimed at figuring out whether expression of the GPR56 was associated with clinicopathological features of osteosarcoma. Eighty-nine patients who received osteosarcoma operation between March 2004 and February 2011 in Linyi People's Hospital were recruited. Immunohistochemical staining (IHC) was carried out to identify the expression of GPR56 in those osteosarcoma tissues, and our cohort was divided into higher-expression group and lower-expression group according to the cut-off of IHC score. Expression of GPR56 in osteosarcoma tissues was correlated with the TNM stage and overall survival. Univariate and multivariate analysis showed that GPR56 could act as an independent prognosis factor for osteosarcoma. Western blot results demonstrated that GPR56-siRNA down-regulated the expression of GTP-RhoA and Ki67. GTP-RhoA participates in the cell migration process, while Ki67 plays important roles in cell proliferation, indicating GPR56 may function in tumor development. Correspondingly, we show that GPR56 regulates the proliferation and invasion capacity of osteosarcoma cells. Our study has revealed the prognostic value of GPR56 expression in osteosarcoma.
...
PMID:Expression of G Protein-coupled Receptor 56 Is an Unfavorable Prognostic Factor in Osteosarcoma Patients. 2739 30


<< Previous 1 2 3 4 Next >>