title: Regulatory functions of TRAIL in hematopoietic progenitors: human umbilical cord blood and murine bone marrow transplantation.
abstract: The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) signaling pathway has selective toxicity to malignant cells. The TRAIL receptors DR4 and DR5 are expressed at low levels in human umbilical cord blood cells (3-15%) and are upregulated by incubation with the cognate ligand, triggering apoptosis in 70-80% of receptor-positive cells (P<0.001). Apoptosis is not induced in hematopoietic progenitors, as determined from sustained severe combined immunodeficiency reconstituting potential and clonogenic activity. Furthermore, elimination of dead cells after incubation with TRAIL for 72 h results in a threefold enrichment in myeloid progenitors. Exposure to TRAIL in semisolid cultures showed synergistic activity of DR4 and granulocyte/macrophage colony-stimulating factor in recruiting lineage-negative (lin(-)) and CD34(+) progenitors and in promoting the formation of large colonies. In murine bone marrow, approximately 30% of lin(-) cells express TRAIL-R2 (the only murine receptor), and the receptor is upregulated after transplantation in cycling and differentiating donor cells that home to the host marrow. However, this receptor is almost ubiquitously expressed in the most primitive (lin(-)SCA-1(+)c-kit(+)) progenitors, and stimulates the clonogenic activity of lin(-) cells (P<0.001), suggesting a tropic function after transplantation. It is concluded that TRAIL does not trigger apoptosis in hematopoietic progenitors, and upregulation of its cognate receptors under stress conditions mediates tropic signaling that supports recovery from hypoplasia.
authors.affiliation: Center for Stem Cell Research, Department of Pediatric Hematology-Oncology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
authors.forename: K
authors.initials: K
authors.lastname: Mizrahi
authors.forename: J
authors.initials: J
authors.lastname: Stein
authors.forename: M
authors.initials: M
authors.lastname: Pearl-Yafe
authors.forename: O
authors.initials: O
authors.lastname: Kaplan
authors.forename: I
authors.initials: I
authors.lastname: Yaniv
authors.forename: N
authors.initials: N
authors.lastname: Askenasy
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism; D016026:Bone Marrow Transplantation; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D005312:Fetal Blood / Q000187:drug effects / Q000378:metabolism*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D019089:Stem Cell Factor / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*
chemical_list: D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D019089:Stem Cell Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D016178:Granulocyte-Macrophage Colony-Stimulating Factor