Insulin-like growth factor II blocks apoptosis of N-myc2-expressing woodchuck liver epithelial cells.
N-myc2 and insulin-like growth factor II (IGF-II) are coordinately overexpressed in the great majority of altered hepatic foci, which are the earliest precancerous lesions observed in the liver of woodchuck hepatitis virus carrier woodchucks, and these genes continue to be overexpressed in hepatocellular carcinomas (HCCs). We have investigated the function of these genes in woodchuck hepatocarcinogenesis by using a woodchuck liver epithelial cell line (WC-3). WC-3 cells react positively with a monoclonal antibody (12.8.5) against woodchuck oval cells, suggesting a lineage relationship with oval cells. Overexpression of N-myc2 in three WC-3 cell lines caused their morphological transformation and increased their growth rate and saturation density in medium containing 10% serum. Removal of serum from the medium increased cell death of the N-myc2-expressing lines, whereas cell death in control lines was minimal. The death of N-myc2-expressing WC-3 cells was accompanied by nucleosomal fragmentation of cellular DNA, and DAPI (4',6-diamidino-2-phenylindole) staining revealed condensation and fragmentation of the nuclei, suggesting that N-myc2-expressing WC-3 cells undergo apoptosis in the absence of serum. In colony regression assays, conducted in the absence of serum, control colonies were stable, while N-myc2-expressing colonies regressed to various degrees. Addition of recombinant human IGF-II to the serum-free medium blocked both cell death and colony regression in all the N-myc2-expressing lines. Therefore, coordinate overexpression of N-myc2 and IGF-II in woodchuck altered hepatic foci may allow cells which otherwise might die to survive and progress to hepatocellular carcinoma.
Yang
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Marion Bessin Liver Research Center, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Faris
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Hixson
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Affigne
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Rogler
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CE
D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular; D002455:Cell Division; D002460:Cell Line; D016895:Culture Media, Serum-Free; D004247:DNA / Q000032:analysis / Q000187:drug effects; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000166:cytology* / Q000502:physiology; D008113:Liver Neoplasms; D008392:Marmota; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D014162:Transfection
D016895:Culture Media, Serum-Free; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D007335:Insulin-Like Growth Factor II; D004247:DNA