Evidence that ceramide mediates the ability of tumor necrosis factor to modulate primitive human hematopoietic cell fates.
In this study, it is shown that short-term exposure of normal human marrow CD34(+)CD38(-) cells to low concentrations of tumor necrosis factor (TNF) in the presence of 100 ng/mL Flt3 ligand and Steel factor and 20 ng/mL interleukin-3 (IL-3), IL-6, and granulocyte colony-stimulating factor, in either bulk or single-cell serum-free cultures, markedly reduces their ability subsequently to generate colony-forming cells (CFCs) in 6-week stromal cell-containing long-term cultures without affecting their viability, mitogenic response, or short-term ability to produce CFCs. A similar differential effect on the functional attributes of CD34(+)CD38(-) cells was seen when C2- or C6-ceramide, but not dihydro-C2-ceramide (an inactive analog of ceramide), was substituted for TNF. The addition of D-erythro-MAPP (a specific inhibitor of intracellular ceramide degradation) enhanced the ability of TNF to selectively eliminate long-term culture-initiating cell (LTC-IC) activity. These findings indicate that TNF can directly modulate the ability of CD34(+)CD38(-) cells to maintain their LTC-IC function at doses below those required to initiate apoptosis, cell cycle arrest, or both, and they suggest that this may be mediated by the TNF-induced generation of intracellular ceramide. Identification of a signaling intermediate that can influence primitive hematopoietic cell fate decisions offers a new approach to the investigation of signaling mechanisms in normal stem cell populations and to how these may be altered in leukemic cells.
Maguer-Satta
V
V
Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.
Oostendorp
R
R
Reid
D
D
Eaves
C J
CJ
D002478:Cells, Cultured; D002518:Ceramides / Q000494:pharmacology / Q000502:physiology*; D003114:Colony-Forming Units Assay; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004357:Drug Synergism; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008565:Membrane Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013107:Sphingolipids / Q000502:physiology; D019089:Stem Cell Factor / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002518:Ceramides; D016895:Culture Media, Serum-Free; D007377:Interleukin-3; D015850:Interleukin-6; D008565:Membrane Proteins; D013107:Sphingolipids; D019089:Stem Cell Factor; D014409:Tumor Necrosis Factor-alpha; C084881:flt3 ligand protein; D016179:Granulocyte Colony-Stimulating Factor