Transforming growth factor-beta regulates c-kit message stability and cell-surface protein expression in hematopoietic progenitors

Abstract

The cell-surface receptor c-kit and its cognate ligand stem-cell factor (SCF) or steel factor (SLF) are important for the maintenance of hematopoiesis both in vitro and in vivo. Transforming growth factor- beta (TGF-beta) has been shown to be a potent inhibitor of SLF-mediated synergistic growth of murine Lin-Sca-1+ progenitor cells, as well as more committed progenitors. In the present study, we examined the regulation of c-kit mRNA and cell-surface expression by TGF-beta. Among the murine hematopoietic progenitor cells tested, the myeloid cell line FDC-P1 and the mast-cell line MC-6, as well as progenitor-enriched bone marrow cells, constitutively expressed functional cell-surface c-kit. Treatment of these progenitor cell lines and primary progenitor cells with TGF-beta resulted in downregulation of cell-surface c-kit expression. This effect was not a secondary event of cell-cycle status. TGF-beta inhibition was dose- and time-dependent, with 50% inhibition seen between 0.3 to 3 ng/mL TGF-beta and maximal inhibition at 30 ng/mL. Using the FDC-P1 cell line, we observed that the inhibition of cell-surface c-kit expression by TGF-beta is preceded by a marked reduction in c-kit mRNA levels starting 2 hours after TGF-beta treatment, and reaches a maximum by 6 hours. The inhibition in steady- state c-kit mRNA levels is explained, in part, by a decrease in the half-life of c-kit transcripts (2 to 4 hours for control cells v 0.5 to 1.5 hours for TGF-beta-treated cells). These findings suggest that TGF- beta regulates the responsiveness of murine hematopoietic progenitors to SLF through a decrease in c-kit message stability leading to decreased cell-surface expression.

Neutralization of Autocrine Transforming Growth Factor‐β in Human Cord Blood CD34+CD38−Lin−Cells Promotes Stem‐Cell‐Factor‐Mediated Erythropoietin‐Independent Early Erythroid Progenitor Development and Reduces Terminal Differentiation

“…This growth stimulatory effect was previously reported in other culture systems [32,[34][35][36][37]. Possible mechanism(s) cited for the ability of anti-TGF-β to activate quiescent cells include upregulation of SCF and/or Epo receptors [1,[9][10][11]; however, in our cultures, anti-TGF-β-mediated proliferation of CD34 + CD38 -Lincells was not preceded by the upregulation of c-kit expression, as measured by flow cytometry (data not shown). Because TGF-β1 regulates the production and/or function of the cell cycle inhibitors p21 and p27 [38][39][40][41], our results are consistent with the concept that neutralization of endogenous TGF-β1 leads to greater cell cycle progression of quiescent cells.…”

“…Previous studies addressing the effect of TGF-β1, or its neutralization by antibodies or antisense oligonucleotides in association with other cytokines, on the regulation of primitive hematopoietic stem cells (HSCs) have demonstrated that: A) TGF-β1 has both paracrine and autocrine effects on HSCs [3][4][5][6]; B) TGF-β1 regulates quiescence of HSCs, and C) primitive HSCs, such as human CD34 + CD38lineage-markernegative (Lin -) and murine Lin -Hoescht 33342 low /Rhodamine 123 low cells, are more highly sensitive to cell cycle inhibition than their more mature counterparts [6][7][8]. The ability of TGF-β1 to maintain primitive HSCs in a quiescent state has been explained by downmodulation of the expressions of various cytokine receptors including: the receptor for stem cell factor (SCF) (c-kit), the thrombopoietin receptor (c-Mpl), the interleukin (IL)-6 receptor, and the Flt-3 ligand receptor [1,[9][10][11]. Moreover, it has been argued that TGF-β1 may control apoptosis in normal hematopoiesis [11], but recent findings, showing an in vitro reversibility of the cell cycle inhibitory effect exerted by TGF-β1 on HSCs [8,[12][13] and increased HSC survival after TGF-β neutralization, are not compatible with the induction of cell death [2,14].…”

dlk Inhibits Stem Cell Factor‐Induced Colony Formation of Murine Hematopoietic Progenitors: Hes‐1‐Independent Effect

“…From this finding, it is implied that mDLK-Fc inhibits macrophage colony formation. It is known that suppressive cytokines such as macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), IL-1α, and transforming growth factor-β (TGF-β) are produced by accessory cells [42][43][44][45][46][47][48]. These cytokines inhibit the proliferation of hematopoietic progenitors stimulated by various hematopoietic growth factors.…”

Age‐related changes in dermal mast cell prevalence in BALB/c mice: functional importance and correlation with dermal mast cell expression of Kit

“…Transforming growth factor-b 1 (TGF-b 1 ) can decrease SCF mRNA and SCF production in vitro. 21 In another study, 22 a de®ciency of tumour necrosis factor (TNF) or TNF receptors was linked with decreased dermal mast cell prevalence; it is unknown if this was an effect that was manifest in reduced SCF levels. Similarly, mice carrying the Uvs1 gene, a gene for susceptibility to UV suppression, have a dermal mast cell prevalence greater than their BALB/c counterparts.…”