Abstract 5093: Fibulin-5 supports pancreatic tumor growth through inhibition of integrin-induced ROS

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDA) is a highly recalcitrant disease. One factor contributing to chemoresistance is thought to be the desmoplastic response seen in these tumors. Fibronectin (FN) is a major constituent of the desmoplastic reaction of PDA. It has been shown that integrin activation by fibronectin can induce reactive oxygen species (ROS) production by stromal cells. Increased ROS has been observed in many cancers, including PDA. Therefore, we propose that oxidation therapy is an attractive approach to increase chemoresponse in PDA as this strategy takes advantage of the sensitivity of these tumors to further ROS insults. We discovered that the matricellular protein Fibulin5 (Fbln5) is upregulated in PDA and reduces FN-mediated integrin-induced ROS production by competing with FN for binding to α5β1 integrin and blocking integrin-induced ROS production. Mutation of the RGD-integrin binding domain in Fbln5 to RGE abolishes the binding of Fbln5 to the integrin and increases integrin-induced ROS production. Fbln5RGE/RGE (RGE) mice, display reduced tumor growth in implant and genetic models of PDA (KIC and KPC) as a direct consequence of elevated ROS levels in the tumor microenvironment. Furthermore, ROS induction correlates with reduced angiogenesis in tumors from RGE animals and had an additive therapeutic effect when combined with standard therapy. We have identified multiple oxidative stress-responsive genes that are elevated in stromal fibroblasts isolated from tumors from RGE animals. One of the most promising targets is NAD(P)H dehydrogenase (quinone 1) (Nqo1). In support of this observation we found that the level of Nqo1 is significantly higher in RGE fibroblasts compared with WT fibroblasts when plated on FN but not collagen or plastic. Furthermore we have demonstrated that FN-mediated induction of ROS and Nqo1 is dependent on β1 integrin and 5-lipooxygenase (5-LOX). Our studies reveal a unique integrin-based mechanism to enhance ROS production to a level that is specifically toxic to the tumor by exploiting the tumor-specific expression of Fbln5. Current studies are focused on understanding the mechanism by which Fbln5 is induced in PDA. Citation Format: Mary Topalovski, Miao Wang, Zachary Moore, David Boothman, Rolf Brekken. Fibulin-5 supports pancreatic tumor growth through inhibition of integrin-induced ROS. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5093.