Up‐regulation of interleukin (IL)‐6 receptor gene expression in vitro and in vivo in IL‐6 deprived myeloma cells

Abstract
Mycloma cells absolutely require interleukin‐6 (IL‐6) for growing in vivo in patients with multiple mycloma and exogenous IL‐6‐dependentmycloma cell lines have been reproducibly obtained. In this study we show a dramatic up‐regulation of the IL‐6 receptor (gp80 chain) gene expression in mycloma cell lines following the removal of exogenous IL‐6. Such a regulation was also known to occur in IL‐6‐deprived mycloma cells in vivo in three patients who were treated with optimal doses of anti‐IL‐6 monoclonal antibodies. The direct effect of IL‐6 on IL‐6 receptor gene expression in mycloma cells was further confirmed by adding IL‐6 to an autonomously growing mycloma cell line.