title: Downregulation of c-kit (stem cell factor receptor) in transformed hematopoietic precursor cells by stroma cells.
abstract: We show a dramatic downregulation of the stem cell factor (SCF) receptor in different hematopoietic cell lines by murine stroma. Growth of the human erythroid/macrophage progenitor cell line TF-1 is dependent on granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3). However, TF-1 cells clone and proliferate equally well on stroma. Independent stroma-dependent TF-1 clones (TF-1S) were generated on MS-5 stroma. Growth of TF-1S and TF-1 cells on stroma still requires interaction between c-kit (SCF receptor) and its ligand SCF, because antibodies against c-kit inhibit growth to less than 2%. Surprisingly, c-kit receptor expression (RNA and protein) was downregulated by 2 to 3 orders of magnitude in TF-1S and TF-1 cells grown on stroma. This stroma-dependent regulation of the kit receptor in TF-1 was also observed on exposure to kit ligand-negative stroma, thus indicating the need for heterologous receptor ligand interaction. Removal of stroma induced upregulation by 2 to 4 orders of magnitude. Downregulation and upregulation of c-kit expression could also be shown for the megakaryocytic progenitor cell line M-07e and was comparable to that of TF-1, indicating that stroma-dependent regulation of c-kit is a general mechanism. Downregulation may be an economic way to compensate for the increased sensitivity of the c-kit/ligand interaction on stroma. The stroma-dependent c-kit regulation most likely occurs at the transcriptional level, because mechanisms, such as splicing, attenuation, differential promoter usage, or mRNA stability, could be excluded.
authors.affiliation: Department of Cell and Virus Genetics, Heinrich-Pette-Institut für experimentelle Virologie und Immunologie an der Universität Hamburg, Hamburg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Heberlein
authors.forename: J
authors.initials: J
authors.lastname: Friel
authors.forename: C
authors.initials: C
authors.lastname: Laker
authors.forename: D
authors.initials: D
authors.lastname: von Laer
authors.forename: U
authors.initials: U
authors.lastname: Bergholz
authors.forename: M
authors.initials: M
authors.lastname: Bögel
authors.forename: L K
authors.initials: LK
authors.lastname: Ashman
authors.forename: K
authors.initials: K
authors.lastname: Klingler
authors.forename: W
authors.initials: W
authors.lastname: Ostertag
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002455:Cell Division; D002460:Cell Line; D015536:Down-Regulation; D005786:Gene Expression Regulation; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins; D019089:Stem Cell Factor / Q000378:metabolism; D017154:Stromal Cells / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D007377:Interleukin-3; D012333:RNA, Messenger; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019009:Proto-Oncogene Proteins c-kit