Interferon gamma (IFNgamma ) and tumor necrosis factor alpha synergism in ME-180 cervical cancer cell apoptosis and necrosis. IFNgamma inhibits cytoprotective NF-kappa B through STAT1/IRF-1 pathways.
We investigated the molecular mechanism of the synergism between interferon gamma (IFNgamma) and tumor necrosis factor alpha (TNFalpha) documented in a variety of biological occasions such as tumor cell death and inflammatory responses. IFNgamma/TNFalpha synergistically induced apoptosis of ME-180 cervical cancer cells. IFNgamma induced STAT1 phosphorylation and interferon regulatory factor 1 (IRF-1) expression. Transfection of phosphorylation-defective STAT1 inhibited IFNgamma/TNFalpha-induced apoptosis, whereas IRF-1 transfection induced susceptibility to TNFalpha. Dominant-negative IkappaBalpha transfection sensitized ME-180 cells to TNFalpha. IFNgamma pretreatment attenuated TNFalpha- or p65-induced NF-kappaB reporter activity, whereas it did not inhibit p65 translocation or DNA binding of NF-kappaB. IRF-1 transfection alone inhibited TNFalpha-induced NF-kappaB activity, which was reversed by coactivator p300 overexpression. Caspases were activated by IFNgamma/TNFalpha combination; however, caspase inhibition did not abrogate IFNgamma/TNFalpha-induced cell death. Instead, caspase inhibitors directed IFNgamma/TNFalpha-treated ME-180 cells to undergo necrosis, as demonstrated by Hoechst 33258/propidium iodide staining and electron microscopy. Taken together, our results indicate that IFNgamma and TNFalpha synergistically act to destroy ME-180 tumor cells by either apoptosis or necrosis, depending on caspase activation, and STAT1/IRF-1 pathways initiated by IFNgamma play a critical role in IFNgamma/TNFalpha synergism by inhibiting cytoprotective NF-kappaB. IFNgamma/TNFalpha synergism appears to activate cell death machinery independently of caspase activation, and caspase activation seems to merely determine the mode of cell death.
Clinical Research Center, Samsung Biomedical Research Institute and Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea.
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Suk
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Chang
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Kim
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Kim
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Kim
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Kim
M S
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Lee
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004357:Drug Synergism; D005260:Female; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000633:toxicity*; D016328:NF-kappa B / Q000378:metabolism*; D009336:Necrosis; D010750:Phosphoproteins / Q000378:metabolism*; D011003:Ploidies; D011994:Recombinant Proteins / Q000378:metabolism / Q000633:toxicity; D050794:STAT1 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*; D002583:Uterine Cervical Neoplasms / Q000473:pathology
D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D016328:NF-kappa B; D010750:Phosphoproteins; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases