Anti-α4 integrin antibody suppresses the development of multiple myeloma and associated osteoclastic osteolysis

Abstract

Supporting roles of stromal cells in preferential colonization of myeloma cells in bone marrow and development of associated osteoclastic osteolysis through cell-cell interactions have been indicated. Here we examined the effects of a monoclonal antibody to α4 integrin (anti-α4 Ab) that disrupts myeloma cell-stromal cell interactions mediated via α4β1 integrin and vascular cell adhesion molecule-1 (VCAM-1) on myeloma cell growth in bone marrow and accompanying osteolysis. The anti-α4 Ab decreased VCAM-1-stimulated 5TGM1/luc cell growth in culture. The 5TGM1 murine myeloma cells stably transfected with the firefly luciferase (5TGM1/luc) were inoculated from tail vein in bg/xid/nd mice. Preventative administration of the anti-α4 Ab suppressed the elevation of serum IgG2b levels, decreased 5TGM1/luc tumor burden with increased apoptosis in bone and spleen, reduced bone destruction with diminished number of osteoclasts, and prolonged survival of 5TGM1/luc-bearing mice. In contrast, therapeutic administration of the antibody failed to show these effects. However, therapeutic administration of the antibody combined with melphalan significantly suppressed serum IgG2b levels and tumor burden in bone. Our results suggest that the interactions with stromal cells via α4β1/VCAM-1 are critical to the development of myeloma and associated osteolysis and that disruption of these interactions using anti-α4 Ab is a potential therapeutic approach for myeloma. © 2004 by The American Society of Hematology.