Expression and function of a receptor for hyaluronan-mediated motility on normal and malignant B lymphocytes

Abstract

Migration through extracellular matrix is fundamental to malignant invasion. A receptor for hyaluronan-mediated motility (RHAMM) has previously been shown to play a fundamental role in locomotion of ras-transformed cells as well as functioning in signal transduction. Expression of RHAMM was characterized on B lymphocytes from normal and malignant lymphoid tissues using multiparameter phenotypic immunofluorescence analysis as well as functional analysis of its role in locomotion of malignant hairy cell leukemia B cells. RHAMM is not detectable on most normal B cells located in blood, spleen, or lymph node, but it is detectable on bone marrow and thymic B cells. Among B-cell malignancies, it is expressed on most terminally differentiated B cells from multiple myeloma bone marrows, is present on a subset of non-Hodgkin's lymphomas, and is absent on B chronic lymphocytic leukemia. Activation of peripheral blood B cells by Staphylococcus A cowan (SAC), but not by pokeweed mitogen, induced transient expression of RHAMM at day 3 of culture, suggesting RHAMM may be used by antigen-activated normal B cells. For malignant cells, expression of RHAMM increased on long-term culture of bone marrow plasma cells from multiple myeloma patients, indicating prolonged expression in contrast to the transient expression on SAC-activated normal B cells. Intriguingly, RHAMM was expressed on hairy leukemia cells located in spleen but absent from those in peripheral blood of the same patient. RHAMM, as expressed on splenic hairy cells, was a 58-Kd molecule that binds hyaluronan, is encoded by a 5.2-kb messenger RNA, and participates in locomotion by these cells. Hairy cells locomoted in response to hyaluronan at 4 mu per minute. Monoclonal antibody to RHAMM inhibited this locomotion almost completely as detected using video time-lapse cinemicrography. These observations are consistent with a role for RHAMM in malignant invasion and metastatic growth.