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.
Suk
K
K
Clinical Research Center, Samsung Biomedical Research Institute and Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea.
Chang
I
I
Kim
Y H
YH
Kim
S
S
Kim
J Y
JY
Kim
H
H
Lee
M S
MS
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