IFNalpha sensitizes ME-180 human cervical cancer cells to TNFalpha-induced apoptosis by inhibiting cytoprotective NF-kappaB activation.
Tumor necrosis factor alpha (TNFalpha) induces apoptosis of a variety of tumor cell types. The anti-tumor effect of TNFalpha is often augmented by interferon (IFN) gamma. We hypothesized that IFNalpha, which shares many biological activities with IFNgamma, might also synergize with TNFalpha for the induction of tumor cell death. We tested our hypothesis using ME-180 human cervical cancer cells exposed to either IFNalpha or TNFalpha alone or both. We analyzed the death of ME-180 cells by biochemical and cytological means, and investigated the molecular mechanism underlying cytotoxic synergism between the two cytokines. We found that (i) IFNalpha/TNFalpha synergistically induced apoptosis of ME-180 cells, which was accompanied by activation of caspases-3 and -8; (ii) IFNalpha induced signal transducer and activator of transcription (STAT) 1 phosphorylation, and transfection of phosphorylation-defective STAT1 dominant-negative mutant inhibited IFNalpha/TNFalpha-induced apoptosis; (iii) inhibition of nuclear factor kappaB (NF-kappaB) by proteasome inhibitor MG-132 sensitized ME-180 cells to TNFalpha alone; (iv) IFNalpha treatment attenuated TNFalpha-induced NF-kappaB reporter activity, while it did not inhibit DNA binding of NF-kappaB. Taken collectively, our results indicate that IFNalpha sensitizes ME-180 cells to TNFalpha-induced apoptosis by inhibiting TNFalpha-mediated cytoprotective NF-kappaB activation, and this sensitizing effect of IFNalpha is mediated through a STAT1-dependent pathway.
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, South Korea.
Kim
Y H
YH
Chang
I
I
Kim
J Y
JY
Choi
Y H
YH
Lee
K Y
KY
Lee
M S
MS
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D019610:Cytoprotection / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004357:Drug Synergism; D005260:Female; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D016898:Interferon-alpha; D007976:Leupeptins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde