Abstract
Tumor necrosis factor (TNF) induces cel death in several tumor cell lines by undefined mechanisms. Using a cDNA expression cloning strategy we identified two cDNAs that completely inhibit the TNF-induced death pathway in MCF7 breast carcinoma cells. These cDNAs encoded for Bcl-2 and Bcl-x. To compare the cytotoxic signal transduction pathway induced by the TNF receptor versus that induced by Fas, we transfected MCF7 cells with a Fas expression construct. The resulting cell line, MCF-Fas, was highly sensitive to cytotoxicity induced by TNF or anti-Fas. Expression of either bcl-2 or bcl-x in these cells rendered them completely resistant to lysis induced by either TNF or Fas. Interestingly, exposure of MCF-Fas cells to anti-Fas or TNF induced activation of phospholipase A2 (PLA2), while only TNF activated NF-kappa B. Activation of PLA2 was completely blocked whereas activation of NF-kappa B was unaffected by overexpression of either bcl-x or bcl-2. Moreover, PLA2-inhibitors, quinacrine and dexamethasone, partially inhibited cytotoxicity induced by either TNF or anti-Fas. These data suggest an involvement of PLA2 in both TNF- and Fas-mediated cytotoxicity and a novel mechanism of action for bcl-2 and bcl-x, i.e. inhibition of arachidonic acid metabolism, by which they may, in addition of apoptosis, modulate inflammation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Antigens, Surface / genetics
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Antigens, Surface / metabolism*
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Apoptosis* / genetics
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Apoptosis* / physiology
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Base Sequence
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Breast Neoplasms / enzymology
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Breast Neoplasms / genetics
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Breast Neoplasms / metabolism*
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Breast Neoplasms / pathology
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Cell Division / drug effects
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Ceramides / metabolism
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Dexamethasone / pharmacology
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Drug Resistance / genetics
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Enzyme Activation / drug effects
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Female
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Humans
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Luciferases / biosynthesis
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Molecular Sequence Data
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NF-kappa B / drug effects
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NF-kappa B / metabolism*
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Phospholipases A / biosynthesis*
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Phospholipases A2
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-bcl-2
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Quinacrine / pharmacology
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Signal Transduction
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Sphingomyelin Phosphodiesterase / pharmacology
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Sphingosine / analogs & derivatives
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Sphingosine / pharmacology
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Tumor Cells, Cultured
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Tumor Necrosis Factor-alpha / antagonists & inhibitors*
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bcl-X Protein
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fas Receptor
Substances
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Antigens, Surface
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BCL2L1 protein, human
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Ceramides
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N-acetylsphingosine
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NF-kappa B
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Tumor Necrosis Factor-alpha
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bcl-X Protein
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fas Receptor
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Dexamethasone
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Luciferases
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Phospholipases A
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Phospholipases A2
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Sphingomyelin Phosphodiesterase
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Quinacrine
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Sphingosine