Abstract 2930: IL-6 stimulates STAT-3 and Pim-1 kinase in pancreatic cancer cell lines

Abstract

Abstract Introduction: IL-6 has both diagnostic and prognostic significance in pancreatic cancer. We investigated the signaling pathways activated in response to IL-6 in pancreatic cell lines, with a focus on STAT-3 and Pim-1 kinase. Methods: IL-6 receptor (IL-6R) expression was evaluated by Western blot analysis across a panel of human pancreatic cell lines. Panc-1 and MiaPaCa2 cell lines were serum starved for 24 hrs and then treated with 100 ng/mL of IL-6 for various time courses from 0 to 6 hr. STAT-3 activation and Pim-1 kinase protein levels were assessed in the presence and absence of IL-6 by Western blot analysis. The ability of cucurbitacin B to block both STAT-3 and Pim-1 activation, and inhibit cell proliferation was investigated. Stably transfected Pim-1 kinase over-expressing cell lines were generated and characterized for their response to IL-6 in vitro, and their growth rate in vivo as flank tumors in scid mice. Results: IL-6R is broadly expressed across multiple cancer cell lines, with the highest expression observed in the Panc-1 cell line. IL-6 stimulation resulted in increased STAT-3 phosphorylation in Panc-1, and MiaPaCa2 tumor cell lines as well as the HP-DEV transformed pancreatic ductal cell line. Treatment with IL-6 resulted in increased Pim-1 protein expression in the Panc-1 but not the MiaPaCa2 parent cell lines. Induction of Pim-1 protein was also observed in both Panc-1 and MiaPaCa2 stably transfected over-expressing cell lines. Pre-treatment with the STAT-3 inhibitor cucurbitacin B resulted in inhibition of STAT-3 phosphorylation and decreased cell proliferation, but was not associated with suppression of Pim-1 protein expression in the Panc-1 cell lines. Over-expression of Pim-1 in the Panc-1 cell line was associated with no significant changes in basal apoptosis rate, cell growth rate in vitro or in flank xenografts, or IL-6 induced expression of VEGF. Conclusions: IL-6 stimulation activates both STAT-3 and Pim-1 kinase expression in pancreatic cell line models. Induction of Pim-1 kinase was cell line specific, suggesting that the molecular context is essential for this pathway to be activated. Suppression of STAT-3 with a pharmacological inhibitor resulted in exaggerated Pim-1 expression in over-expressing cell lines implying Pim-1 up-regulation may be one of the compensatory and/or stress pathways activated when STAT-3 is inhibited. Stable over-expressing Pim-1 kinase Panc-1 and MiaPaCa2 cells did not exhibit significant changes in growth or apoptosis, unlike previously reported studies in the literature with other pancreatic cancer cell line models. This may be due to the multiple pathways that are dysregulated in these cell lines. Both STAT-3 and Pim-1 kinase have previously been identified as drug targets in multiple malignancies, including leukemia, lymphoma, prostate, and pancreatic cancer. Our study suggests that both pathways may be activated in patients with elevated IL-6 levels. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2930. doi:10.1158/1538-7445.AM2011-2930