IL-6 upregulates its own receptor on some human myeloma cell lines

Interleukin 6 (IL-6) is the major survival factor of myeloma cells. In this study, we demonstrate that IL-6, oncostatin M (OSM) and leukemia inhibitory factor (LIF) upregulate membrane IL-6 receptor alpha (IL-6Ralpha) on OPM-2 myeloma cell line at transcriptional level. In OPM-2 cells, IL-6, OSM and LIF induce both signal transducers and activators of transcription (STAT), mitogen activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI 3-K) activation. We show that the cytokine-induced upregulation of IL-6Ralpha can be abolished by a janus kinase (JAK)-2 specific inhibitor, i.e. AG490, suggesting an involvement of the JAK/STAT pathway in this process. Finally, IL-6Ralpha upregulation was also inhibited by wortmannin, an inhibitor of the PI 3-kinase pathway. In conclusion, IL-6 can upregulate its own receptor on OPM-2 cells probably through the JAK/STAT and PI 3-kinase pathways.