title: Analysis of the mechanism of adhesion of precursor-B acute lymphoblastic leukemia cells to bone marrow fibroblasts.
abstract: Normal B lymphopoiesis is dependent on a close relationship between B-cell precursors and the bone marrow (BM) microenvironment. To further understand the mechanisms regulating the proliferation of the malignant counterpart of B-cell precursors, namely precursor-B acute lymphoblastic leukemia (ALL), we examined the adhesion to BM fibroblasts (BMF) of 19 cases of precursor-B ALL using a chromium labeling assay. Eleven of 19 cases showed greater than 10% binding to BMF (range 2.3% to 54.8%, mean 19.1%). Binding was increased approximately twofold by preincubation of BMF with tumor necrosis factor and interleukin-4, which also resulted in upregulation of expression of vascular cell adhesion molecule-1 (VCAM-1) on BMF. The mechanism of attachment was investigated using murine monoclonal antibodies to leukocyte integrins, principally the beta, integrins VLA-4 and VLA-5, which were demonstrated to be present on most cases by flow cytometry. Statistically significant inhibition of adhesion was observed with antibodies to the beta 1 common subunit, VLA-4, and VLA-5, whereas little effect was seen with antibodies to VLA-6 or the beta 2 integrin subunit. Preincubation of fibroblasts with an antibody to VCAM-1 (a ligand of VLA-4) inhibited leukemic cell binding in the majority of cases, which was an effect also observed on cytokine-stimulated BMF. However, a minority of cases, as well as the pre-B lines NALM-6 and KM-3, showed no evidence of inhibition of adhesion with anti-VCAM-1 antibodies. Treatment of BMF with antifibronectin antibody alone had little effect on ALL adhesion and did not enhance the inhibitory effect of anti-VCAM-1. These data indicate that precursor-B ALL cells bind to BM stroma through the beta 1 integrins VLA-4 and VLA-5 and that this effect is partly mediated by VCAM-1 on stromal cells, although other undefined VLA ligands are also likely to be involved. Attachment of ALL cells to stroma is likely to play a key role in regulating the survival and growth of these cells through exposure to stromal cytokines.
authors.affiliation: Haematology Department, Westmead Hospital, New South Wales, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Bradstock
authors.forename: V
authors.initials: V
authors.lastname: Makrynikola
authors.forename: A
authors.initials: A
authors.lastname: Bianchi
authors.forename: K
authors.initials: K
authors.lastname: Byth
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001854:Bone Marrow Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005347:Fibroblasts / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000473:pathology*; D016029:Receptors, Very Late Antigen / Q000502:physiology; D017154:Stromal Cells / Q000473:pathology; D014407:Tumor Cells, Cultured; D019010:Vascular Cell Adhesion Molecule-1
chemical_list: D015815:Cell Adhesion Molecules; D016029:Receptors, Very Late Antigen; D019010:Vascular Cell Adhesion Molecule-1