ABSTRACT
Human pancreatic cancer is one of the most fatal of all solid tissue malignancies. Pancreatic inflammation plays a key role in the development of pancreatic malignancy mediated by pro-inflammatory signalling cascades. Despite advances in surgery and radiation oncology, no significant improvements in overall survival have yet been achieved. Recent investigations suggest a crucial role of interleukin-33 (IL-33), a novel IL-1 family cytokine, in the pathogenesis of chronic pancreatitis and possibly pancreatic cancer. However, the precise role of IL-33 in pancreatic carcinogenesis is poorly understood. As IL-33 mediates its effects via the heterodimeric ST2L/IL-1 receptor accessory protein (IL-1RAcP) receptor complex, we investigated the influence of IL-33 alone, IL-33 combined with IL-1 and other inflammatory cytokines on IL-33 receptor/ligand mRNA expression and production of tumorigenic factors in the highly metastatic human pancreatic adenocarcinoma cell line Colo357. Our results demonstrated that IL-1 and IL-3 up-regulated IL-33 mRNA while IL-12 showed the opposite effect. We also detected a counter-regulatory effect of IL-33 and IL-1 on the mRNA expression of soluble IL-33 receptor ST2 and membrane-bound receptor ST2L. Furthermore, IL-33 and IL-1 acted synergistically in up-regulating secretion of pro-inflammatory IL-6. IL-33 alone stimulated spontaneous release of pro-angiogenic IL-8, but it did not affect IL-1-induced IL-8 secretion. IL-33/IL-1 effects on cytokine production appear to be mediated via NF-κB activation. These data argue for the pro-inflammatory role of IL-33 in Colo357 cells implying that IL-33 might act as a crucial mediator in inflammation-associated pancreatic carcinogenesis.
Subject(s)
Gene Expression Regulation, Neoplastic , Inflammation Mediators/metabolism , Interleukins/genetics , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/pathology , Receptors, Cell Surface/genetics , Animals , Cell Line, Tumor , Gene Expression Regulation, Neoplastic/drug effects , Humans , Interleukin-1/pharmacology , Interleukin-1 Receptor-Like 1 Protein , Interleukin-33 , Interleukins/metabolism , Interleukins/pharmacology , Mice , NF-kappa B/metabolism , Neoplasm Metastasis , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, Cell Surface/metabolism , Signal Transduction/geneticsABSTRACT
Human pancreatic cancer is currently one of the fifth-leading causes of cancer-related mortality with a 5-year survival rate of less than 5%. Since pancreatic carcinoma is largely refractory to conventional therapies, there is a strong medical need for the development of novel and innovative therapeutic strategies. Increasing evidence suggests an association of carcinogenesis and chronic inflammation. Because IL-1 plays a crucial role in inflammation-associated carcinogenesis, we analyzed the biological effects of IL-1 and its modulation by the chemopreventive green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) in the human pancreatic adenocarcinoma cell line Colo357. Proinflammatory IL-6 and PGHS-2 as well as proangiogenic IL-8 and VEGF were induced by IL-1, whereas the secretion of invasion-promoting MMP-2 remained unaffected. IL-1 responsiveness and constitutive MMP-2 release in Colo357 were downregulated by EGCG in a dose- and time-dependent manner. Moreover, EGCG reduced cell viability via induction of apoptosis in Colo357. Since EGCG effects on cytokine production precede reduction in cell viability, we hypothesize that these findings are not only a result of cell death but also depend on alterations in the IL-1 signaling cascade. In this context, we found for the first time an EGCG-induced downregulation of the IL-1RI expression possibly being caused by NF-κB inhibition and causative for its inhibitory action on the production of tumorigenic factors. Thus, our data might have future clinical implications with respect to the development of novel approaches as an adjuvant therapy in high-risk patients with human pancreatic carcinoma.
