TY - JOUR
T1 - Inhibition of c-Myc expression sensitizes hepatocytes to tumor necrosis factor-induced apoptosis and necrosis
AU - Liu, Hailing
AU - Lo, Chau R.
AU - Jones, Brett E.
AU - Pradhan, Zehra
AU - Srinivasan, Anu
AU - Valentino, Karen L.
AU - Stockert, Richard J.
AU - Czaja, Mark J.
PY - 2000/12/22
Y1 - 2000/12/22
N2 - The typical proliferative response of hepatocytes to tumor necrosis factor (TNF) can be converted to a cytotoxic one by transcriptional arrest. Although NF-κB activation is critical for hepatocyte resistance to TNF toxicity, the contribution of other TNF-inducible transcription factors remains unknown. To determine the function of c-Myc in hepatocyte sensitivity to TNF, stable transfectants of the rat hepatocyte cell line RALA255-10G containing sense and antisense c-myc expression vectors were isolated with increased (S-Myc cells) and decreased (AN-Myc cells) c-Myc transcriptional activity. While S-Myc cells proliferated in response to TNF treatment, AN-Myc cells underwent 32% cell death within 6 h. Fluorescent microscopic studies indicated that TNF induced apoptosis and necrosis in AN-Myc cells. Cell death was associated with DNA hypoploidy and poly(ADP-ribose) polymerase cleavage but occurred in the absence of detectable caspase-3, -7, or -8 activation. TNF-induced, AN-Myc cell death was dependent on Fas-associated protein with death domain and partially blocked by caspase inhibitors. AN-Myc cells had decreased levels of NF-κB transcriptional activity, but S-Myc cells maintained resistance to TNF despite NF-κB inactivation, suggesting that c-Myc and NF-κB independently mediate TNF resistance. Thus, in the absence of sufficient c-Myc expression, hepatocytes are sensitized to TNF-induced apoptosis and necrosis. These findings demonstrate that hepatocyte resistance to TNF is regulated by multiple transcriptional activators.
AB - The typical proliferative response of hepatocytes to tumor necrosis factor (TNF) can be converted to a cytotoxic one by transcriptional arrest. Although NF-κB activation is critical for hepatocyte resistance to TNF toxicity, the contribution of other TNF-inducible transcription factors remains unknown. To determine the function of c-Myc in hepatocyte sensitivity to TNF, stable transfectants of the rat hepatocyte cell line RALA255-10G containing sense and antisense c-myc expression vectors were isolated with increased (S-Myc cells) and decreased (AN-Myc cells) c-Myc transcriptional activity. While S-Myc cells proliferated in response to TNF treatment, AN-Myc cells underwent 32% cell death within 6 h. Fluorescent microscopic studies indicated that TNF induced apoptosis and necrosis in AN-Myc cells. Cell death was associated with DNA hypoploidy and poly(ADP-ribose) polymerase cleavage but occurred in the absence of detectable caspase-3, -7, or -8 activation. TNF-induced, AN-Myc cell death was dependent on Fas-associated protein with death domain and partially blocked by caspase inhibitors. AN-Myc cells had decreased levels of NF-κB transcriptional activity, but S-Myc cells maintained resistance to TNF despite NF-κB inactivation, suggesting that c-Myc and NF-κB independently mediate TNF resistance. Thus, in the absence of sufficient c-Myc expression, hepatocytes are sensitized to TNF-induced apoptosis and necrosis. These findings demonstrate that hepatocyte resistance to TNF is regulated by multiple transcriptional activators.
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U2 - 10.1074/jbc.M001565200
DO - 10.1074/jbc.M001565200
M3 - Article
C2 - 11016920
AN - SCOPUS:0034704116
SN - 0021-9258
VL - 275
SP - 40155
EP - 40162
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 51
ER -