Chronic pancreatic inflammation is strongly associated with pancreatic cancer. We previously demonstrated that inflammatory cytokines interact to produce a DUOX2 -dependent, reactive oxygen species (ROS)-related, pro-oxidant milieu that could increase the pathologic potential of pancreatic inflammation, enhancing malignant transformation. Furthermore, we have shown that DUOXuox2 expression is upregulated in patients with chronic pancreatitis as well as pancreatic ductal adenocarcinoma (PDAC). Dexamethasone (Dex) has been reported to inhibit PDAC invasiveness, the formation of pancreatic intraepithelial neoplasia in genetically-engineered mouse models of pancreatic cancer, as well as epithelial to mesenchymal transition in PDACs, and local tumor recurrence and metastasis in vivo. Using cultured human pancreatic cancer cell lines, we found that in a dose- and time-dependent fashion Dex inhibited cytokine (IFN-γ/LPS, IL-4, and IL-17)-mediated up-regulation of DUOXuox2 and VEGF-A expression in several human pancreatic cancer cell lines, including BxPC-3, ASPC-1, and CFPAC-1. Dex pretreatment also blocked DUOX2-related DNA double strand breaks (detected as activated γH2AX) and the expression of HIF-1α in PDAC cells treated with pro-inflammatory cytokines. The effects of Dex were abolished by pre-treatment with the Dex antagonist RU-486. As expected, we did not observe anti-proliferative effects of Dex on PDAC cells in vitro. However, Dex strongly repressed DUOXuox2 mRNA and protein expression as well as the growth of xenografts initiated from BxPC-3 cells; in contrast, for the MIA-Paca line that is unresponsive to cytokines in culture, Dex produced no effect on DUOXuox2 expression and tumor growth when these cells were grown as xenografts. Examination of the human DUOXuox2 promotor in silico revealed a putative negative glucocorticoid receptor (GR) binding element. Western analysis, using nuclear extracts from pancreatic cancer cells treated with Dex, revealed that both activated glucocorticoid receptor and certain co-repressors, such as NCOR-1/2 and histone deacetylases (HDAC1, 2, and 3) exist in human pancreatic cancer cell nuclei. Our ongoing experiments are focused on understanding the molecular mechanism of Dex-mediated DUOXuox2 repression both in vitro and in vivo. In summary, these studies suggest that cytokine-related oxidant stress, generated by Duox2, could play a role in the progression of pancreatic cancer.
Citation Format: Yongzhong Wu, James H. Doroshow. Dexamethasone suppresses cytokine-induced dual oxidase 2 and VEGF-A expression in human pancreatic cancer cells in vitro and pancreatic cancer growth in xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5741.