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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a previous study, osteosarcoma cells expressing both 5-lipoxygenase (5-LO) and 5 lipoxygenase-activating protein (FLAP) synthesized leukotrienes upon A23187 stimulation (Dixon, R. A. F., R. E. Diehl, E. Opas, E. Rands, P. J. Vickers, J. F. Evans, J. W. Gillard, and D. K. Miller. 1990. Nature (Lond.). 343:282-284). Osteosarcoma cells expressing 5-LO but not expressing FLAP were unable to synthesize leukotrienes. Thus, it was determined that FLAP was required for the cellular synthesis of leukotrienes. To examine the role of FLAP in A23187-induced translocation of 5-LO to a membrane fraction, we have studied the A23187-stimulated translocation of 5-LO in osteosarcoma cells expressing both 5-LO and FLAP, and in osteosarcoma cells expressing 5-LO only. We demonstrate that in cells expressing both 5-LO and FLAP, 5-LO translocates to membranes in response to A23187 stimulation. This 5-LO translocation is inhibited when cells are stimulated in the presence of MK-886. In osteosarcoma cells expressing 5-LO but not expressing FLAP, 5-LO is able to associate with membranes following A23187 stimulation. In contrast to the cells containing both 5-LO and FLAP, MK-886 is unable to prevent 5-LO membrane association in cells transfected with 5-LO alone. Therefore, we have demonstrated that in this cell system, 5-LO membrane association and activation can be separated into at least two distinct steps: (1) calcium-dependent movement of 5-LO to membranes without product formation, which can occur in the absence of FLAP (membrane association), and (2) activation of 5-LO with product formation, which is FLAP dependent and inhibited by MK-886 (enzyme activation).
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PMID:A23187-induced translocation of 5-lipoxygenase in osteosarcoma cells. 146 57

Previous studies involving transfection of cDNAs for 5-lipoxygenase-activating protein (FLAP) and 5-lipoxygenase into osteosarcoma cells have shown that both these proteins are essential for leukotriene synthesis (Dixon, R. A. F., Diehl, R. E., Opas, E., Rands, E., Vickers, P. J., Evans, J. F., Gillard, J. W., and Miller, D. K. (1990) Nature 343, 282-284). In the present study we show that FLAP is present in a variety of cells known to produce leukotrienes, but is absent from a number of cells which do not synthesize leukotrienes. Furthermore, differentiation of the human promyelocytic HL-60 cell line towards granulocytic cells following exposure to dimethylsulfoxide is associated with the concurrent induction of both FLAP and 5-lipoxygenase and an increased capacity to synthesize leukotrienes. Cellular leukotriene synthesis in this system is functionally dependent on FLAP as shown by its inhibition by the leukotriene biosynthesis inhibitor MK-886, a compound which specifically binds to FLAP.
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PMID:Correlation between expression of 5-lipoxygenase-activating protein, 5-lipoxygenase, and cellular leukotriene synthesis. 217 53

Several inflammatory diseases, including asthma, arthritis and psoriasis are associated with the production of leukotrienes by neutrophils, mast cells and macrophages. The initial enzymatic step in the formation of leukotrienes is the oxidation of arachidonic acid by 5-lipoxygenase (5-LO) to leukotriene A4. Osteosarcoma cells transfected with 5-LO express active enzyme in broken cell preparations, but no leukotriene metabolites are produced by these cells when stimulated with the calcium ionophore A23187, indicating that an additional component is necessary for cellular 5-LO activity. A new class of indole leukotriene inhibitor has been described that inhibits the formation of cellular leukotrienes but has no direct inhibitory effect on soluble 5-LO activity. We have now used these potent agents to identify and isolate a novel membrane protein of relative molecular mass 18,000 which is necessary for cellular leukotriene synthesis.
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PMID:Identification and isolation of a membrane protein necessary for leukotriene production. 230 Jan 72

Cloned 15-lipoxygenase has been expressed for the first time in eukaryotic and prokaryotic cells. Transfection of osteosarcoma cells with a mammalian expression plasmid containing the cDNA for human reticulocyte 15-lipoxygenase resulted in cell lines that were capable of oxidizing body arachidonic acid and linoleic acid. The lipoxygenase metabolites were identified by reverse-phase and straight-phase high pressure liquid chromatography, ultraviolet spectroscopy, and direct mass spectrometry, verifying that the cDNA for 15-lipoxygenase encodes an enzyme with authentic 15-lipoxygenase activity. Incubation of the transformed cells with arachidonic acid generated 15-hydroxyeicosatetraenoic acid (HETE) and 12-HETE in a ratio of 8.6 to 1, demonstrating that 15-lipoxygenase can also perform 12-lipoxygenation. Lesser amounts of 15-keto-ETE, four isomers of 8,15-diHETE, and one isomer of 14,15-diHETE were observed. Incubation with linoleic acid generated predominantly 13-hydroxy linoleic acid. The reaction was inhibited by eicosatetraynoic acid but not by indomethacin. Antibodies to a peptide corresponding to a unique region of the predicted amino acid sequence were generated and shown to react with one major band of 70 kDa on immunoblots of human leukocyte 15-lipoxygenase. To obtain antibodies to the full length enzyme, the cDNA was subcloned into a bacterial expression vector and was expressed as a fusion with the CheY protein. The overexpressed protein was readily purified from bacteria and was shown to be immunoreactive to the peptide-derived antibody. Antibodies raised to this recombinant enzyme did not cross-react with human leukocyte 5-lipoxygenase but did identify 15-lipoxygenase in rabbit reticulocytes, human leukocytes, and tracheal epithelial cells, suggesting that the 15-lipoxygenases from these different cell types are structurally related.
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PMID:Expression of cloned human reticulocyte 15-lipoxygenase and immunological evidence that 15-lipoxygenases of different cell types are related. 231 85

5-Lipoxygenase has been expressed in a mammalian osteosarcoma cell line transfected with the cloned cDNA for human leukocyte 5-lipoxygenase. Two clonal cell lines derived from the transfected cells expressed the enzymatic activity. When incubated with arachidonic acid (100 microM), the major 5-lipoxygenase products of 10,000 X g supernatants from these cells were 5-hydroxyeicosatetraenoic acid (5-HETE), and the nonenzymatic hydrolysis products of leukotriene (LT)A4. The ratio of 5-HETE to LT (between 6:1 and 9:1) was similar to that observed in leukocyte supernatants. Furthermore, incubation of 10,000 X g supernatants from the transfected cells with 5-hydroperoxyeicosatetraenoic acid (5-HPETE) (75 microM) resulted in the synthesis of LTA4 hydrolysis products. Control osteosarcoma cell supernatants produced no 5-HETE or LT from arachidonic acid or 5-HPETE. Maximal activity of the expressed enzyme required Ca2+, ATP, and two cellular stimulatory factors prepared from human leukocytes. Immunoblot analysis of supernatants from the osteosarcoma cell clones revealed an immunoreactive 80,000-dalton band that was indistinguishable from the band observed in leukocyte supernatants. Therefore, the expressed enzyme was functional and exhibited characteristics that were identical to those of human leukocyte 5-lipoxygenase. When intact transfected osteosarcoma cells were challenged with ionophore A 23187, no 5-lipoxygenase products were formed. If arachidonic acid was added along with the ionophore, the cells synthesized 5-HETE and the nonenzymatic hydrolysis products of LTA4. These results verify that the cDNA used to transfect the osteosarcoma cells encodes for 5-lipoxygenase. Furthermore, these studies offer independent evidence that this single protein possesses both 5-lipoxygenase and LTA4 synthase activity, as has been reported previously from enzyme purification data.
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PMID:Characterization of cloned human leukocyte 5-lipoxygenase expressed in mammalian cells. 316 19

The triterpenes, alpha-amyrin (AA) and its palmitate (AAP) and linoleate esters (AAL), were tested on models of inflammatory and destructive arthritic processes and their effects were compared with the clinical antiarthritic drugs indomethacin (IN) and methotrexate (MTX). The triterpenes had no effect on the prostaglandin phase of carrageenin pedal edema in rats, which was reduced 28% by 100 microM IN. AAL caused a considerable reduction in the synthesis by human neutrophils of 5-lipoxygenase products--5-HETE (IC50 = 70 microM), LTB4, (62 microM), isomer I (30 microM) and isomer II (24 microM). Rat osteosarcoma cell growth was inhibited by all triterpenes with IC50's (microM) of < 10 (AAP), 14 (AA) and 27 (AAL) and were more effective than IN (35). MTX caused 100% inhibition at a concentration of 10 microM compared with 64% inhibition by AAP. Tadpole collagenase digestion of type I (bone) native collagen was completely inhibited by all the triterpenes as well as IN and MTX at 100 microM. The results indicate that the principal point of antiarthritic intervention by amyrin triterpenes lies in their local inhibition of joint destruction.
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PMID:Antiarthritic mechanisms of amyrin triterpenes. 795 94

A mixed extract containing two naturally occurring flavonoids, baicalin from Scutellaria baicalensis and catechin from Acacia catechu, was tested for cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) inhibition via enzyme, cellular, and in vivo models. The 50% inhibitory concentration for inhibition of both ovine COX-1 and COX-2 peroxidase enzyme activities was 15 microg/mL, while the mixed extract showed a value for potato 5-LOX enzyme activity of 25 microg/mL. Prostaglandin E2 generation was inhibited by the mixed extract in human osteosarcoma cells expressing COX-2, while leukotriene production was inhibited in both human cell lines, immortalized THP-1 monocyte and HT-29 colorectal adenocarcinoma. In an arachidonic acid-induced mouse ear swelling model, the extract decreased edema in a dose-dependent manner. When arachidonic acid was injected directly into the intra-articular space of mouse ankle joints, the mixed extract abated the swelling and restored function in a rotary drum walking model. These results suggest that this natural, flavonoid mixture acts via "dual inhibition" of COX and LOX enzymes to reduce production of pro-inflammatory eicosanoids and attenuate edema in an in vivo model of inflammation.
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PMID:A medicinal extract of Scutellaria baicalensis and Acacia catechu acts as a dual inhibitor of cyclooxygenase and 5-lipoxygenase to reduce inflammation. 1788 37

The immunoregulatory cytokine IL-10 plays an essential role in down-modulating adaptive and innate immune responses leading to chronic inflammatory diseases. In contrast, cysteinyl leukotrienes (cysLTs), important proinflammatory mediators of cell trafficking and innate immune responses, are thought to enhance immune reactions in the pathogenesis of diseases, such as bronchial asthma, atherosclerosis, and pulmonary fibrosis. The aim of this study was to determine the IL-10 regulatory role in cysLT-induced activation of human monocytes and monocyte-derived dendritic cells. Herein we show that cysLT-induced activation and chemotaxis of human monocytes and monocyte-derived immature dendritic cells (iDC) are inhibited by IL-10 pretreatment. IL-10 down-regulated cysLT type 1 and 2 receptors' mRNA in a time- and concentration-dependent fashion. cysLT-induced activation of monocytes and iDCs measured by intracellular calcium flux and immediate-early gene expression (FBJ murine osteosarcoma viral oncogen homolog B and early growth response-2) was potently decreased by IL-10 and by the cysLT antagonist MK571. Chemotaxis of monocytes and iDCs to increasing concentrations of leukotriene D(4) (LTD(4)) was also inhibited by IL-10. LTD(4) enhanced iDC migration in response to CCL5. IL-10 selectively inhibited LTD(4)-induced chemotaxis without affecting migration to CCL5. These data indicate that cysLT-induced activation of human monocytes and dendritic cells may be specifically inhibited by IL-10, suggesting a direct link between the 5-lipoxygenase proinflammatory pathway and IL-10 regulatory mechanisms. Antileukotriene therapies may reproduce some regulatory mechanisms played by IL-10 in inflammatory processes.
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PMID:IL-10 inhibits cysteinyl leukotriene-induced activation of human monocytes and monocyte-derived dendritic cells. 1849 Jul 62

Canine osteosarcoma is an insidious disease with few effective treatment modalities; therefore, use of pharmacologic intervention to improve mortality or morbidity is constantly sought. The use of cyclooxygenase enzyme inhibitors has been an area of interest with limited efficacy based on retrospective examination of tumor expression and in vivo cell proliferation models. Recently, examination of dual cyclooxygenase and 5-lipoxygenase inhibitors in human and canine oncology suggests that 5-lipoxygenase inhibitors may be an effective approach in vitro and during tumor induction in rodent models. Therefore, the authors decided to examine 5-lipoxygenase expression in primary canine osteosarcoma samples and have shown that approximately 65% of osteosarcomas label positive for cytoplasmic 5-lipoxygenase. Further examination of a cell culture and xenograft model shows similar 5-lipoxygenase expression. Surprisingly, a canine 5-lipoxygenase inhibitor (tepoxalin) significantly reduced cell proliferation at physiologic doses in vitro and diminished xenograft tumor growth in nude mice, suggesting that further investigation is needed. Traditionally, 5-lipoxygense leads to production of lipid mediators, such as leukotriene B(4) and 5-oxo-eicosatetraenoic acid, which, when added back to the media of tepoxalin-treated cells, did not recover cell proliferation. The lack of nuclear staining in primary and xenografted tumors and the lack of response to eicoasanoids suggest that lipid mediator production is not the primary means by which tepoxalin acts to alter proliferation. Regardless of the mechanisms involved in retarding cell proliferation, future investigation is warranted.
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PMID:Prevalence of 5-lipoxygenase expression in canine osteosarcoma and the effects of a dual 5-lipoxygenase/cyclooxygenase inhibitor on osteosarcoma cells in vitro and in vivo. 2228 49

The induced differentiation of tumor cells into mature phenotypes is a promising strategy in cancer therapy. In this study, the effects of combined treatment with all-trans retinoic acid (ATRA) and lipoxygenase/cyclooxygenase inhibitors were examined in two osteosarcoma cell lines, Saos-2 and OSA-01. Caffeic acid and celecoxib were used as inhibitors of 5-lipoxygenase and of cyclooxygenase-2, respectively. Changes in the cell proliferation, matrix mineralization, and occurrence of differentiation markers were evaluated in treated cell populations at intervals. The results confirmed the capability of caffeic acid to enhance the antiproliferative effect of ATRA in both cell lines. In contrast, celecoxib showed the same effect in Saos-2 cells only. Furthermore, the extension of matrix mineralization was observed after combined treatment with ATRA and celecoxib or caffeic acid. The increased expression of osteogenic differentiation markers was observed in both cell lines after the combined application of ATRA and inhibitors. The obtained results clearly demonstrate the capability of lipoxygenase/cyclooxygenase inhibitors to enhance the antiproliferative and differentiating effect of ATRA in osteosarcoma cells, although some of these effects are specific and depend on the biological features of the respective tumor or cell line.
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PMID:LOX/COX inhibitors enhance the antineoplastic effects of all-trans retinoic acid in osteosarcoma cell lines. 2479 77


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