MOUSE PLASMACYTOMA GROWTH-INVIVO - ENHANCEMENT BY INTERLEUKIN-6 (IL-6) AND INHIBITION BY ANTIBODIES DIRECTED AGAINST IL-6 OR ITS RECEPTOR

Murine plasmacytomas show a striking dependence on interleukin 6 (IL6) for their growth in vitro. Here, we present evidence suggesting that IL6 also plays an essential role in the in vivo development of these tumors. This conclusion is based on the finding that the tumorigenicity of an IL-6-dependent plasmacytoma cell line was increased ~100-fold on transfection with an IL-6 expression vector, whereas it was inhibited in animals treated with monoclonal antibodies capable of blocking the binding of IL-6 to its receptor. Injection of these antibodies 1 d before tumor challenge protected >50% ofthe mice and retarded tumor growth in all animals. Tumors arising in antibody-treated mice retained their IL-6 dependence in vitro, suggesting that the level of protection could be improved if stronger IL-6 antagonists were available. © 1990, Rockefeller University Press., All rights reserved.