Tyrosine phosphorylation of JAK-TYK kinases in malignant plasma cell lines growth-stimulated by interleukins 6 and 11.

The pleiotropic cytokine interleukin (IL-6) is a major growth factor for murine plasmacytomas/hybridomas and human myeloma cells. Here we report that IL-6 stimulated different patterns of tyrosine phosphorylation of JAK-TYK kinases in IL-6-responsive murine (B9E and T10D) and human (ANBL-6 and OCI-My4) plasma cell tumor lines. Interestingly, the Stat91 transcription factor essential for interferon signaling mediated by JAK-TYK kinases was significantly tyrosine phosphorylated in response to IL-6 in ANBL-6 cells but not in the other cell lines. We further show that IL-11, a cytokine that signals via the gp130 subunit of the IL-6 receptor, induced similar profiles of JAK-TYK tyrosine phosphorylation as IL-6 in B9E and T10D cells. These results suggest that functionally redundant JAK-TYK kinase cascades triggered through gp130 are involved in the growth regulation of plasma cell neoplasms.