Cytokines increase human hemopoietic cell adhesiveness by activation of very late antigen (VLA)-4 and VLA-5 integrins.

Abstract

Sunlln~l.l-yCytokines are known to be important regulators of normal hemopoiesis, acting in concert with components of the bone marrow microenvironment. Interactions with this microenvironment are known to regulate the proliferation, differentiation, and homing of hemopoietic progenitor (CD34 +) cells. Adhesive interactions with the extracellular matrix retain CD34 + cells in close proximity to cytokines, but may also provide important costimulatory signals. Thus, the functional states of adhesion receptors are critical properties of CD34 + cells, but the physiological mechanisms responsible for regulating functional properties of cell adhesion receptors on primitive hemopoietic cells are still unknown. We confirm that the integrins very late antigen (VLA)-4 and VLA-5 are expressed on the CD34 + cell lines MO7e, TF1, and on normal bone marrow CD34 + progenitor cells, but in a low affinity state, conferring on them a weak adhesive phenotype on fibronectin (Fn). Herein, we show that the cytokines interleukin (IL)-3, granulocytemacrophage CSF (GM-CSF), and KIT ligand (KL) are physiological activators of VLA-4 and VLA-5 expressed by MO7e, TF1, and normal bone marrow CD34 + progenitor cells. Cytokinestimulated adhesion on Fn is dose dependent and transient, reaching a maximum between 15 and 30 min and returning to basal levels after 2 h. This cytokine-dependent activation is specific for VLA-4 and VLA-5, since activation of other ~1 integrins was not observed. The addition of second messenger antagonists staurosporine and W7 abolished all cytokine-stimulated adhesion to Fn. In contrast, genistein inhibited KL-stimulated adhesion, but failed to inhibit GM-CSFand IL-3-stimulated adhesion. Our data suggest that cytokines GM-CSF and IL-3 specifically stimulate B1 integrin function via an "inside-out" mechanism involving protein kinase activity, while KL stimulates integrin activity through a similar, but initially distinct, pathway via the KIT tyrosine-kinase. Thus, in addition to promoting the survival, proliferation, and development of hemopoietic progenitors, cytokines also regulate adhesive interactions between progenitor cells and the bone marrow microenvironment by modifying the functional states of specific integrins. These data are of importance in understanding the fundamental processes of/~1 integrin activation and cellular response to mitogenic cytokines, as well as on the clinical setting where cytokines induce therapeutic mobilization of hematopoietic progenitors.

GM-CSF-mobilized peripheral blood CD34+ cells differ from steady-state bone marrow CD34+ cells in adhesion molecule expression

“…6,14 BM CD34 + cells may acquire the capacity to circulate by changing the pattern of Discussion adhesion molecule expression following GM-CSF administration. However, GM-CSF is known to upregulate specific This study was designed to evaluate differences in the expression of adhesion molecules on CD34 + cells in periphadhesion molecules including those in the integrin family on PCs, monocytes and endothelial cells, [23][24][25] although eral blood leukapheresis products (GM-CSF-mobilized) in comparison to CD34 + cells in steady-state BM products.…”

Expression and purification of bioactive soluble murine stem cell factor from recombinant Escherichia coli using thioredoxin as fusion partner

“…SCF promotes the survival (Domen and Weissman, 2000), proliferation (Leary et al, 1992;Tsai et al, 1991), mobilization (Fleming et al, 1993) and adhesion (Levesque et al, 1995) of hematopoietic stem cells and their progenitors. The cytokine is also involved in the development and function of other cell lineages, including melanocytes and germ cells (Sette et al, 2000).…”

The 30/35 kDa chymotryptic fragment of fibronectin enhances retroviral-mediated gene transfer in purified chronic myelogenous leukemia bone marrow progenitors

“…Given that FN enhances gene transfer in CML CD34 + HLA-DR + and CD34 + may partially restore the adhesive properties of CML HPC. This notion is supported by recent work by Levesque et al, 48 HLA-DR − cells, serious consideration of clinical gene therapy protocols which include FN-coated culture dishes during prein which they demonstrated that exposure of normal human CD34 + cells to SCF, IL-3 and GM-CSF in combination constimulation and transduction of CML cells, as well as those intended for the treatment of other diseases, is warranted. ferred on these cells an enhanced adherence to FN.…”