β1-integrins dominate cell traffic of leukemic cells in human bone-marrow stroma

Abstract

The major function of bone marrow is growth stimulation and differentiation of hematopoietic stem cells (Dorshkind, 1990). In vitro studies of long-term bone-marrow cultures (LTBMC) have emphasized the essential role of bone-marrow stromal cells in hematopoiesis (Dorshkind, 1990). Colonization of bone-marrow precursor cells is mediated by contacts between adhesion receptors on bone-marrow stromal cells and on precursor hematopoietic cells (Leavesley et al., 1994). These precursor cells interact directly with stromal cells, but also indirectly via the extracellular matrix (ECM) proteins. As a result of this type of interaction, intracellular signalling of stromal cells can take place followed by activation and production of growth factors or cytokines. Growth factors and cytokines are essential for the regulation of cell growth and differentiation (Dorshkind, 1990). Different adhesion pathways have been described for the leukocyte-endothelial-cell interaction pathways (Elices et al., 1990). In particular, the role of integrins in cell contacts as well as in the linkage of ECM proteins with the intracellular signal transduction pathways seems to be essential in basic development of the hematopoiesis, but may also be significant in aberrant processes such as tumor-cell invasion (Juliano, 1994;Clark and Brugge, 1995). So far, for the leukemic-cell/bone-marrow stromal-cell interaction, integrins appear to be essential, but the details of this interaction remain largely unknown.The aim of this study was to investigate the variations in adhesion and migratory behavior of leukemic cells on human bone-marrow stromal cells. Therefore, we developed an in vitro model to study the basic interaction patterns of leukemic cells with human bone-marrow stromal cells. Adhesion, spreading and migration of erythroleukemic HEL92.1.7 and K562 cells together with the promyeloid HL60 cells on human BM stromal cells was monitored at the ultrastructural level and with phase-contrast microscopy. The role of adhesion molecules was studied, especially that of the pl-integrins. Discrete distribution of cell-surface molecules on these human leukemic cell lines and BM stromal cells was associated with a clear variation in adhesion and migration patterns. Adhesion and migration blocking studies using MAbs against the various adhesion molecules proved that the P1-integrins VLA-4 and VLA-5 in particular fulfil an essential function in tumor-cell adhesion and migration. MATERIAL AND METHODS Cells and culture conditionsBone-marrow stromal cells. Bone-marrow aspirates were obtained from donors without hematologic abnormalities, after informed consent. The aspirates were obtained from the sternum during coronary bypass operations and were diluted with an equal volume of RPMI 1640 containing heparin. A buf€y coat was isolated by centrifugation for 15 min at 2,000 rpm. Erythrocytes were lysed with NbCl(8.3 g/1 containing 1 g NaHC03 and 37 mg EDTA) buffer and washed 3 times with RPMI-1640 medium. The remaining cells were collected and cultured. A human b...

Effects of human bone marrow stromal cell line (HFCL) on the proliferation, differentiation and apoptosis of acute myeloid leukemia cell lines U937, HL-60 and HL-60/VCR

“…Previous study has shown that binding of AML cells to extracellular matrix proteins fibronectin and laminin was predominantly b1-integrin-dependent, but AML cell adhesion to BM fibroblast relies on the simultaneous involvement of b1 and b2 integrins as well as other currently unrecognized ligands. Similar observations have also been made that the role of gap junctions in direct contact interaction of leukemic progenitors with bone marrow stromal cell line resulting in similar biologic effects as described in the current report [20,30]. Inclusion of these references in the discussion will significantly support the current data.…”

“…After in direct contact with HFCL cells the expression of activated Caspase-3 decreased and the expression of Bcl-2 increased.It was also discovered that the effect by HFCL directly contacted with leukemic cells was more significant than that by transwell group. Since b1 integrin plays an important role in the interaction between bone marrow stromal and leukemic Effects of HFCL on the proliferation, differentiation and apoptosis of acute myeloid leukemia cell lines 159 cells [20], it was indicated that b1 integrin might also attach itself to signal transduction pathways of this inhibition of apoptosis. We analysed the gene profiles differently expressed between HL-60 cells and HL-60 cells in direct contact with HFCL by using Affymetrix GeneChip Human Genome U133 set A.…”

Differential adhesion pattern of B cell chronic lymphocytic leukemia cells

“…Yet, VCAM-1 is also selectively expressed by endothelial cells in adult and fetal hematopoietic organs 27 where it mediates the in vitro adherence of normal and leukemic cells. [28][29][30] Furthermore, binding on to bone marrow fibroblasts via integrin ␣4␤1/VCAM-1 supported survival of B cell lineage acute lymphoblastic leukemia (ALL) cells. 31 We speculate, therefore, that the observed germinal center binding of B-CLL cells via integrin ␣4␤1/VCAM-1 might mirror the capacity of these cells to use this ligand pair for their migration and proliferation within the microenvironment of hematopoietic organs.…”

Human mesenchymal stem cells in contact with their environment: surface characteristics and the integrin system

“…Several research groups have already explored this field and have shared the evidence that ␣4␤1 and ␣5␤1 integrins dominate the traffic of leukemic cells in human BM stroma. For example, K562 cells, an erythroleukemia control cell line, lack the ␣4 and ␣5 receptors and show the absence of binding to the BM [95]. The same group also proposes fibronectin as a matrix for tumour cell adhesion in the BM stroma.…”