title: Adhesion of multiple myeloma peripheral blood B cells to bone marrow fibroblasts: a requirement for CD44 and alpha4beta7.
abstract: We have earlier described the presence of phenotypically unusual monoclonal B cells within the peripheral blood of multiple myeloma (MM) patients. To determine the biological properties of these B cells as compared to B cells from normal donors, we investigated the potential of CD19+ MM blood B cells to adhere to endothelial cell and bone marrow (BM)-fibroblast monolayers. We find that 30-60% of freshly isolated CD19+ MM blood B cells adhere to endothelial cell monolayers, and 50-80% adhere to BM fibroblast monolayers. The adhesion of MM blood B cells to either monolayer was not increased by in vitro activation, suggesting that these cells were activated in vivo. In contrast, fewer than 10% of CD19+ B cells from peripheral blood of normal donors adhered. Function-blocking monoclonal antibodies (mAbs) were used to determine which adhesion receptors were involved in CD19+ MM blood B cell interaction with BM fibroblasts. mAbs against very late antigen 4, the beta7-integrin subunit, and CD44, but not mAbs against very late antigen 5 and beta1, inhibited adhesion 61, 50, and 30%, respectively. The lack of inhibition with mAbs against beta1 implicates alpha4beta7 but not alpha4beta1 in adhesion of CD19+ MM blood B cells. To determine the alpha4beta7 ligand that mediated MM blood B cell adhesion, mAbs against vascular cellular adhesion molecule 1 and fibronectin, as well as CS1 and RGD peptides, were used as inhibitors. These were unable to reduce the adhesion of CD19+ MM blood B cells to BM fibroblasts, suggesting that fibronectin and vascular cellular adhesion molecule 1 are not involved in adhesion. Also, adhesion of MM blood B cells to mucosal addressin cell adhesion molecule 1-transfected Chinese hamster ovary cells was not enhanced compared to control-transfected Chinese hamster ovary cells, suggesting that mucosal addressin cell adhesion molecule 1 was not promoting adhesion of these cells. These data implicate CD44:HA interactions, as well as alpha4beta7 and an as yet unidentified ligand in the adhesion of in vivo activated MM blood B cell adhesion to BM fibroblasts. The adhesion properties of MM CD19+ B cells distinguishes them from normal B cells. Although the malignant status of these cells is as yet undefined, their adhesion properties implicate MM blood B cells in migratory spread of the disease.
authors.affiliation: Department of Oncology, University of Alberta, Edmonton, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Masellis-Smith
authors.forename: A R
authors.initials: AR
authors.lastname: Belch
authors.forename: M J
authors.initials: MJ
authors.lastname: Mant
authors.forename: L M
authors.initials: LM
authors.lastname: Pilarski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000502:physiology*; D018941:Antigens, CD19 / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology*; D001854:Bone Marrow Cells; D016466:CHO Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology*; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology*; D005347:Fibroblasts / Q000166:cytology; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000502:physiology*; D006820:Hyaluronic Acid / Q000502:physiology; D007136:Immunoglobulins / Q000378:metabolism; D039441:Integrin alpha4; D039641:Integrin beta Chains; D016023:Integrins / Q000502:physiology*; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000378:metabolism; D009101:Multiple Myeloma / Q000473:pathology*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018941:Antigens, CD19; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D018960:Hyaluronan Receptors; D007136:Immunoglobulins; D039641:Integrin beta Chains; D016023:Integrins; C504265:MADCAM1 protein, human; D009088:Mucoproteins; D010455:Peptides; D019010:Vascular Cell Adhesion Molecule-1; C091368:integrin beta7; D039441:Integrin alpha4; D006820:Hyaluronic Acid