BLyS expression and JNK activation may form a feedback loop to promote survival and proliferation of multiple myeloma cells.

B-Lymphocyte stimulator (BLyS), a member of tumor necrosis factor superfamily, is a potent co-activator of B cells in vitro, and in vivo induces B cell proliferation and immunoglobulin secretion. Multiple myeloma (MM) is an incurable malignancy of terminally differentiated B cells (plasma cells). Previous studies have well ascertained that BLyS plays an important contributory role in the pathogenesis and propagation of multiple myeloma by virtue of its ability to promote B cell survival, expansion, and differentiation. However, the intracellular signaling of BLyS in human MM cells remains undefined. This study was designed to see whether there was interaction between MAPK signaling pathway and BLyS expression. It was found that the active protein p-JNK was expressed in KM3, U266 and PBMCs of MM patients, and that the expression of BLyS could be changed by JNK pathway activator and inhibitor. In addition, recombinant BLyS activated JNK pathway, while BLyS siRNA treatment inhibited the activation of JNK pathway. The level of BLyS expression and the activation of JNK pathway were positively correlated. These findings suggest that JNK activation and BLyS expression in MM cells may form a positive feedback loop that promotes the survival and proliferation of MM cells, and these may shed some light on the pathogenesis and treatment of MM.