Expression of growth factor receptors in unilineage differentiation culture of purified hematopoietic progenitors

Abstract

We have evaluated the expression of growth factor receptors (GFRs) on early hematopoietic progenitor cells (HPCs) purified from human adult peripheral blood and induced in liquid suspension culture to unilineage differentiation/maturation through the erythroid (E), granulocytic (G), megakaryocytic (Mk), or monocytic (Mo) lineage. The receptors for basic fibroblast GF (bFGF), erythropoietin (Epo), thrombopoietin (Tpo), and macrophage colony-stimulating factor (MCSF) have been only assayed at mRNA level; the majority of GFRs have been evaluated by both mRNA and protein analyses: the expression patterns were consistent at both levels. In quiescent HPCs the receptors for early-acting [flt3 ligand (FL), c-kit ligand (KL), bFGF, interleukin-6 (IL-6)] and multilineage [IL-3, granulocyte-macrophage CSF (GM-CSF)] HGFs are expressed at significant levels but with different patterns, eg, kit and flt3 are detected on a majority and minority of HPCs, respectively, whereas IL-3Rs and GM-CSFRs are present on almost all HPCs. In the four differentiation pathways, expression of early-acting receptors shows a progressive decrease, more rapidly for bFGFR-1 and flt3 than for c-kit; furthermore, c-kit is more slowly downmodulated in the E and Mk than the G and Mo lineages. As a partial exception, IL-6Rs are still detected through the early or late stages of maturation in the Mk and Mo lineages, respectively. IL-3R expression is progressively and rapidly downmodulated in both E and Mk pathways, whereas it moderately decreases in the Mo lineage and is sustained in the G series. The expression of GM-CSFR is gradually downmodulated in all differentiation pathways, ie, the receptor density markedly decreases but late erythroblasts are still partially GM-CSFR+ and terminal G, Mk and Mo cells are essentially GM-CSFR+. Expression of receptors for late-acting cytokines is lineage-specific. Thus, EpoR, G-CSFR, TpoR, and M-CSFR exhibit a gradual induction followed by a sustained expression in the E, G, MK, and Mo lineages, respectively. In the other differentiation pathways the expression of these receptors is either absent or initially low and there-after suppressed. These observations are compatible with the following multi-step model. (1) The early-acting GFRs are expressed on quiescent HPCs with different patterns, whereas the multilineage GFRs are present on > or = 90% to 95% HPCs. (2) Multilineage GFs, potentiated by early-acting HGFs, trigger HPCs into cycling. HPC proliferation/differentiation is followed by declining expression of the early-acting GFRs and in part of multilineage GFRs (see above). (3) Multilineage GFs trigger the expression of the unilineage GFRs (see Testa U, et al: Blood 81:1442, 1993). Interaction of each unilineage GF with its receptor leads to sustained expression of the receptor (possibly via transcription factors activating the receptor promoter) and thus mediates differentiation/maturation through the pertinent lineage.

Mechanisms of differential transferrin receptor expression in normal hematopoiesis

“…The functional linkage between Epo and TfR expression in erythroid cells is further strengthed by the observation that the kinetics of TfR expression in erythroid cells closely resembles that observed for GATA-1 [28] and Epo receptor [57]. More particularly, GATA-1 and EpoR, only scarcely expressed in quiescent HPCs, are initially induced at low level when these cells were triggered to cycling by either an erythroid or granulocytic differentiation stimulus; however, at later stages of differentiation (from day 5 of culture onward) sustained expression of GATA-1 and Epo receptor were observed only in erythroid cells, while these two genes were silenced in granulocytic cells [28,56].…”

Synergy between erythropoietin and stem cell factor during erythropoiesis can be quantitatively described without co‐signaling effects

“…Studies aiming at elucidating the intracellular molecular mechanisms mediating these actions have revealed that SCF was essential for the expression of the EPO receptor (EPOR) and the signal transducer and activator of transcription-5 (STAT5) in immature erythroid progenitors and, subsequently, the increased survival of mature erythroid progenitors (Kapur and Zhang, 2001). In addition, consideration of the differential expression profiles of the SCF and EPO receptors during erythroid differentiation (Broudy et al, 1991;Dai et al, 1991;Menon et al, 2006;Testa et al, 1996;Uoshima et al, 1995) suggest a sequential action of these cytokines.…”

Basic fibroblast growth factor modulates the expression of glycophorin A and c‐kit and inhibits erythroid differentiation in K562 cells

“…Receptors for FGFs have been found on K562 cells (Allouche, 1995;Liuzzo and Moscatelli, 1996) and on CD34 hematopoietic progenitor cells (Berardi et al, 1995;Le Bousse-Kerdil Á es et al, 1996;Testa et al, 1996;Burger et al, 1998Burger et al, , 1999 and direct effects of bFGF have been shown on progenitor cell proliferation (Gabbianelli et al, 1990;Bruno et al, 1993;Gabrilove et al, 1994;Allouche, 1995;Berardi et al, 1995). These direct effects are signi®cantly less than those noted when bFGF is added to stromal based hematopoietic cultures Quito et al, 1996).…”

“…bFGF also promotes myeloblast proliferation and inhibits the terminal differentiation of skeletal muscle cells (Clegg et al, 1987;Olwin and Rapraeger, 1992). 1995; Berardi et al, 1995;Le Bousse-Kerdil Á es et al, 1996;Liuzzo and Moscatelli, 1996;Testa et al, 1996;Burger et al, 1998Burger et al, , 1999. bFGF prevents the transforming growth factor-b (TGF-b)-mediated increase in hemoglobin production by K562 cells (Burger et al, 1994).…”