Combination of 5-FU and IFNalpha enhances IFN signaling pathway and caspase-8 activity, resulting in marked apoptosis in hepatoma cell lines.
Interferon (IFN) combined with 5-Fluorouracil (5-FU) treatment has recently been reported to show beneficial effects in patients with advanced hepatocellular carcinoma. IFNalpha is usually provided for this combination therapy. In this study, we investigated the molecular mechanisms of apoptosis induction in hepatoma cell lines with IFNalpha and 5-FU combination therapy from the view point of 5-FU's additive effect on interferon-related signaling pathways. Five hepatoma cell lines (Hep3B, Huh7, HLE, PLC/PRF/5, and HepG2) were tested for apoptosis inducibility by IFNalpha in the absence or presence of 5-FU. Hep3B was the most apoptosis sensitive to IFN plus 5-FU treatment. The JAK/STAT pathway transcriptional factor ISRE was activated more synergistically when 5-FU was added to IFNalpha treatments. Caspase-3, -9, and especially caspase-8 activity was higher with IFN alpha plus 5-FU than IFN or 5-FU alone. Inhibition of caspase-8, -9, c-Jun N-terminal kinase (JNK), phosphatidylinositide 3-kinase (PI3K), and p38 mitogen-activated protein kinase (p38 MAPK) revealed that caspase-8 inhibition was the most effective at decreasing the apoptotic effects of IFN and/or 5-FU. In JAK1 and ISGF3gamma-silenced Hep3B cells, the apoptosis induction and caspase-8 activation levels by IFN, even in combination with 5-FU, were abrogated. In conclusion, caspase-8 is the most important factor that controls IFN and 5-FU-induced apoptosis in hepatoma cell lines.
Koike
Kazuko
K
Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
Takaki
Akinobu
A
Tatsukawa
Masashi
M
Suzuki
Mayumi
M
Shiraha
Hidenori
H
Iwasaki
Yoshiaki
Y
Sakaguchi
Kohsaku
K
Shiratori
Yasushi
Y
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit / Q000037:antagonists & inhibitors / Q000235:genetics; D016898:Interferon-alpha / Q000494:pharmacology*; D053613:Janus Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D053613:Janus Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D053181:Caspase 8; D005472:Fluorouracil