TYROSINE PHOSPHORYLATION OF JAK-TYK KINASES IN MALIGNANT PLASMA-CELL LINES GROWTH-STIMULATED BY INTERLEUKIN-6 AND INTERLEUKIN-11

The pleiotropic cytokine interleukin (IL)-6 is a major growth factor f or murine plasmacytomas/hybridomas and human myeloma cells. Here we re port that IL-6 stimulated different patterns of tyrosine phosphorylati on of JAK-TYK kinases in IL-6-responsive murine (B9E and T10D) and hum an (ANBL-6 and OCI-My4) plasma cell tumor lines. Interestingly, the St at91 transcription factor essential for interferon signaling mediated by JAK-TYK kinases was significantly tyrosine phosphorylated in respon se 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 phosphory lation as IL-6 in B9E and T10D cells. These results suggest that funct ionally redundant JAK-TYK kinase cascades triggered through gp130 are involved in the growth regulation of plasma cell neoplasms. (C) 1994 A cademic Press, Inc.