Inhibition of interleukin 6-mediated mitogen-activated protein kinase activation attenuates growth of a cholangiocarcinoma cell line

Biliary tract malignancies represent challenges because of the lack of effe ctive therapy and poor prognosis, in part because of the paucity of informa tion regarding the mechanisms regulating their growth. We have recently ide ntified a critical role for the p44/p42 mitogen-activated protein kinase (M APK) pathway in interleukin 6 (IL-6)-stimulated growth of human cholangiocy tes, Although IL-6 is a potential mitogen for cholangiocarcinoma, the role of this cytokine and its intracellular signaling pathways in cholangiocarci noma growth is unknown. Thus, our aims were to determine the role of IL-6-m ediated signaling mechanisms, and in particular the MAPK pathways, in the g rowth regulation of human cholangiocarcinoma, KMCH-1 cells (malignant chola ngiocyte cells) secreted IL-6 constitutively, and increased IL-6 secretion in response to inflammatory cytokines such as tumor necrosis factor alpha ( TNF-alpha) and IL-1 beta, Stimulation with IL-6 resulted in proliferation o f malignant cholangiocytes. These cells also possessed the IL-6 receptor co mplex subunits as directly assessed by immunoblot analysis. Furthermore, pr oliferation was completely inhibited by preincubation with anti-IL-6 neutra lizing antibodies, indicating that the proliferative response to IL-6 invol ved receptor-mediated signaling. Both p38 and p44/p42 MAPKs were constituti vely present and active in malignant cholangiocytes, and increased activity of both was observed within 15 minutes of stimulation with IL-6. Selective inhibition of either the p44/p42 MAPK pathway, by PD098059, or of the p38 MAPK pathway, by SB203580, blocked proliferation in response to IL-6. Thus, IL-6 can contribute to the autocrine and/or paracrine growth stimulation o f malignant cholangiocytes via activation of either p38 or p44/p42 MAPK sig naling pathways.