TNF down-regulation of receptor tyrosine kinase-dependent mitogenic signal pathways as an important step in cytostasis induction and commitment to apoptosis of Kym-1 rhabdomyosarcoma cells.
Growth of Kym-1 rhabdomyosarcoma cells depends on endogenous receptor tyrosine kinase signals activated by insulin and insulin-like growth factors (IGF), as revealed from enhancement of proliferation by insulin and IGF-1 and cytostatic action of inhibitors of IR/IGFR kinases. Depending on the presence or absence of the caspase inhibitor z-VAD-fmk, TNF induced full growth arrest or apoptosis, respectively, indicating dominance of TNF over mitogenic signal pathways in Kym-1 cells. In accordance with a caspase-independent cytostatic action, TNF downregulated IR kinase activity and caused a profound inhibition of downstream mitogenic signals including the MAPK cascade and STAT5, key pathways of proliferation and cell survival. Removal of z-VAD-fmk after 24 h induced rapid cell death in the absence of TNF. The inhibition of survival signals concomitant with persisting proapoptotic signals may tip the balance towards an irreversible commitment of the cell to apoptosis that becomes apparent upon relief of suppression of effector caspases.
Institute of Cell Biology and Immunology, University of Stuttgart, Germany.
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P
Storz
H
H
Döppler
J
J
Horn-Müller
G
G
Müller
K
K
Pfizenmaier
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015536:Down-Regulation / Q000502:physiology; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D020239:Receptor Cross-Talk / Q000502:physiology; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D012208:Rhabdomyosarcoma; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000201:enzymology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D007004:Hypoglycemic Agents; D007328:Insulin; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D017526:Receptor, IGF Type 1; D019908:Proto-Oncogene Proteins c-raf