Methyltransferase inhibitor S-adenosyl-L-homocysteine sensitizes human breast carcinoma MCF7 cells and related TNF-resistant derivatives to TNF-mediated cytotoxicity via the ceramide-independent pathway.
In this study we investigated the signalling requirements for TNF-induced cytotoxicity modulated by the methyltransferase inhibitor S-adenosyl-L-homocysteine (AdoHcy) using the TNF-sensitive human breast carcinoma MCF7 cells and its established TNF-resistant clones (R-A1 and clone 1001). Our data indicate that inhibition of methylation reactions by adenosine plus homocysteine, which are known to condense within cells to AdoHcy, markedly potentiated TNF-induced cytotoxicity in MCF7 cells and rendered related TNF-resistant variants, TNF-sensitive by a mechanism independent from the ceramide pathway. We demonstrated that the dominant-negative derivative of FADD (FADD-DN) blocked methylation inhibition/TNF-induced cell death. Moreover, TNF-mediated cytotoxicity modulated by AdoHcy was blocked by the ICE-inhibiting peptide z-VAD-fmk, suggesting that an ICE-like protease is required for the methylation inhibition/TNF-inducible death pathway. In conclusion, these results suggest that the methyltransferase inhibitor AdoHcy potentiates TNF-induced cytotoxicity in MCF7 cells and renders TNF-resistant MCF7 clones, TNF-sensitive via the ceramide independent pathway and that FADD and the ICE-like protease are likely necessary components in transducing methylation inhibition/TNF signals for cell death.
INSERM U. 487, Institut Gustave-Roussy, 39, rue Camille-Desmoulins, 94805 Villejuif, France.
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Shatrov
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Ameyar
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Cai
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Bettaieb
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Chouaib
D000230:Adenocarcinoma / Q000473:pathology*; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D029681:Arabidopsis Proteins; D001943:Breast Neoplasms / Q000473:pathology*; D061945:Caspase Inhibitors; D002518:Ceramides / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors*; D019175:DNA Methylation / Q000187:drug effects*; D004351:Drug Resistance; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D012435:S-Adenosylhomocysteine / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*
D000590:Amino Acid Chloromethyl Ketones; D029681:Arabidopsis Proteins; D061945:Caspase Inhibitors; D002518:Ceramides; D015853:Cysteine Proteinase Inhibitors; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D012435:S-Adenosylhomocysteine; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis; D004248:DNA (Cytosine-5-)-Methyltransferases