Tumor necrosis factor alpha (TNF alpha) downregulates c-kit proto- oncogene product expression in normal and acute myeloid leukemia CD34+ cells via p55 TNF alpha receptors

Abstract

Tumor necrosis factor alpha (TNF alpha), as a modulator of hematopoiesis, interacts with many growth factor receptors, such as interleukin-3, granulocyte-macrophage colony-stimulating factor (CSF), and granulocyte-CSF receptors. Here, we studied the interactions between TNF alpha and the stem cell factor (SCF) receptor, c-kit, in normal CD34+ hematopoietic progenitors and their leukemic counterpart, ie, acute myeloid leukemic (AML) CD34+ cells coexpressing c-kit antigen. The results showed that (1) incubation of normal bone marrow mononuclear cells with 200 U/mL rhTNF alpha for 20 hours induced a diminution of 31.2% +/- 5.2% of CD34+ cells coexpressing c-kit; (2) the same decrease was observed using purified CD34+ cells and, furthermore, their proliferative response to SCF was inhibited by 31.5% +/- 7.3% after exposure to TNF alpha; (3) similar experiments performed on CD34+ c-kit+ AML cells from 11 patients gave comparable results. Further analysis at the mRNA level indicated that TNF alpha decreased c-kit mRNA transcripts. Moreover, using monoclonal antibodies against the two types of TNF alpha receptors, p75 and p55, we showed that the downregulation of c-kit proto-oncogene product by TNF alpha, on normal and leukemic CD34+ cells, was exclusively mediated by the TNF alpha p55 receptor. Therefore, we conclude that TNF alpha acts as a downregulator of the SCF receptor expression.

Expression and role in growth regulation of tumour necrosis factor receptors p55 and p75 in acute myeloblastic leukaemia cells

“…Our results indicate that the enhancing effects of TNFon IL-3 or GM-CSF-induced AML cell growth are equally mediated through both the p55 and p75 TNF receptors, whereas the inhibition of G-CSF or SCF-stimulated proliferation is exclusively signalled via the p55 receptors. These data concerning the TNF-induced inhibition of the G-CSF or SCFinduced proliferation of AML cells are in accordance with reported observations (Delwel et al, 1992;Khoury et al, 1994). However, a recent study has shown that the TNFmediated enhancement of IL-3/GM-CSF-induced proliferation is only a p55-mediated event (Delwel et al, 1992).…”

“…Proliferationof acute myeloid leukaemia (AML) cells in vitro is stimulated by haemopoietic growth factors (HGFs), in particular, interleukin-3 (IL-3), granulocytemacrophage colony-stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), macrophage-CSF (M-CSF) and stem cell factor (SCF) (Delwel et al, 1988;Kuriu et al, 1991). Tumournecrosis factor-(TNF-) can modulate the in vitro responses through a variety of mechanisms, including synergism with IL-3 and GM-CSF in stimulation of AML growth (Hoang et al, 1989), and up-regulation of IL-3 and GM-CSF receptors (Elbaz et al, 1991a); suppression of G-CSF-induced AML proliferation through down-regulation of G-CSF receptors (Elbaz et al, 1991b); inhibition of SCF-stimulated AML cell growth by down-regulation of SCF receptors (Khoury et al, 1994); induction of AML cell growth via an autocrine mechanism (Carter et al, 1992); and inhibition of clonal proliferation of leukaemic cells . Some AML cells constitutively secrete TNFand use this activity as an autocrine growth modulator (Oster et al, 1989;Carter et al, 1992).…”

Induction of c‐kit Molecules on Human CD34 + /c‐kit <low Cells: Evidence for CD34 + /c‐kit <low Cells as Primitive Hematopoietic Stem Cells

“…However, only a small but steady number of CD34 + /c-kit <low cells were detected in the CB, suggesting that a niche constructed by stromal cells or some cytokine(s) negatively regulate the induction of c-kit molecules and the reactivity to SCF to maintain dormant P-HSCs. The report that TNF-α and TGF-β downregulate not only the c-kit m-RNA but also c-kit protein in CD34 + /c-kit high cells and CD34 + leukemia cells might support this possibility [38][39][40].…”

Serum levels of p55 and p75 soluble TNF receptors in adult acute leukaemia at diagnosis: correlation with clinical and biological features and outcome

“…Experimental evidence suggests that tumour necrosis factor (TNF) is involved in the proliferation of acute leukaemia cells ( Hoang et al , 1989 ; Oster et al , 1989 ; Elbaz et al , 1991a , b; Delwel et al , 1992 ; Carter et al , 1994 , 1996). TNF acts as a pleiotropic cytokine enhancing leukaemic growth ( Hoang et al , 1989 ; Oster et al , 1989 ; Carter et al , 1994 , 1996), inducing the transcription of other proliferation‐relevant cytokine or cytokine receptor genes ( Elbaz et al , 1991a , b; Delwel et al , 1992 ; Vinante et al , 1993 , 1996; Khoury et al , 1994 ; Carter et al , 1996 ) and triggering apoptosis ( Elbaz et al , 1991b ; Delwel et al , 1992 ; Khoury et al , 1994 ; Carter et al , 1996 ).…”

“…Both TNF receptors (p55‐ and p75‐TNFR), which bind to TNF with roughly equal affinity ( Bazzoni & Beutler, 1995; Gruss & Dower, 1995), have been reported to be expressed on acute leukaemia cells and to mediate distinct either inhibitory or stimulatory effects ( Delwel et al , 1992 ; Carter et al , 1996 ). In acute myeloid leukaemia (AML) blasts the engagement in vitro of p55‐TNFR can be followed by enhanced DNA synthesis ( Hoang et al , 1989 ; Oster et al , 1989 ; Delwel et al , 1992 ; Carter et al , 1994 , 1996), induction of granulocyte‐macrophage colony stimulating factor (GM‐CSF) ( Carter et al , 1996 ) and regulation of the receptors for stem cell factor (SCF), granulocyte colony stimulating factor (G‐CSF) and GM‐CSF ( Elbaz et al , 1991a , b; Delwel et al , 1992 ; Khoury et al , 1994 ; Carter et al , 1996 ) and by cytotoxic effects ( Kobayashi et al , 1997 ). p75‐TNFR seems to be mainly involved in the induction of secondary cytokines ( Delwel et al , 1992 ; Carter et al , 1996 ).…”