Modulation of TNF-mediated cell lysis in vitro: further analysis of intracellular signaling.
We have investigated the post-receptor events governing the Tumor Necrosis Factor (TNF)-mediated cytotoxicity in vitro. As calcium has been reported to be an essential mediator in the cell killing processes, we asked whether an early increase in intracellular calcium could be involved during TNF-induced cell death. Using the ACAS methodology (adherent cell analysis and sorting), we could not detect any significant increase in intracellular calcium following TNF treatment (40 s) within the TNF-sensitive human breast carcinoma MCF7 cell line. In addition, A23187 (0.1-0.4 microM) did neither enhance TNF-mediated MCF7 cell lysis, further confirming that TNF-mediated cell lysis can occur in the absence of an early calcium increase. Given the potentiating effect of cAMP-inducing agents, such as forskolin, on TNF-mediated cytotoxicity, we have investigated the relationship between cAMP accumulation and the TNF signaling pathway during cell death. Our results indicate that the potentiating effect of forskolin (50 microM) on TNF-mediated MCF7 cell lysis did not involve a modulation in the TNF-induced activation of the nuclear factor NF-kB but was associated with an increase in the DNA fragmenting capacity of TNF as assessed by agarose gel electrophoresis of target cell DNA.
Branellec
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Laboratoire de Biologie des Tumeurs Humaines, URA1156 CNRS, Institut Gustave-Roussy, Villejuif, France.
Mishal
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Chouaib
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D000230:Adenocarcinoma / Q000473:pathology; D001943:Breast Neoplasms / Q000473:pathology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002448:Cell Adhesion; D016923:Cell Death / Q000187:drug effects*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004273:DNA, Neoplasm; D016328:NF-kappa B; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D000001:Calcimycin; D000242:Cyclic AMP; D002118:Calcium