Abstract 4833: The eicosanoid 20-HETE triggers Ras activation, pancreatic cancer growth and metastasis through inflammatory macrophage signaling
Authors: Gus-Brautbar Yael , Casper Jessica , Bielenberg Diane R. , Cheng Jennifer , Schmidt Birgitta , Hammock Bruce D. , Zeldin Darryl C. , Kieran Mark W. , Panigrahy Dipak 
Published: May 2015

Prolonged, unresolving inflammation is increasingly implicated in the pathogenesis of pancreatic cancer, but the critical inflammatory mediators remain largely unknown. Most efforts to elucidate these mediators have focused on protein cytokines rather than lipid autacoids. Lipid autacoids are metabolites of arachidonic acid and other related fatty acids that regulate inflammation and tumor growth. Among these, the metabolites of the cytochrome P450 (CYP) epoxygenases and ω-hydroxylases, including EETs and 20-HETE, respectively, have been largely neglected in cancer. Recently, we showed that epoxyeicosatrienoic acids (EETs) stimulate multi-organ metastasis and tumor dormancy escape. We report for the first time, that elevated levels of 20-hydroxyeicosatetraenoic acid (20-HETE), a product of the ω-hydroxylases CYP4A/F, stimulate primary pancreatic tumor growth and metastasis. Using genetic and pharmacological manipulation of endogenous 20-HETE, we demonstrate that systemic administration of 20-HETE promotes primary human and murine pancreatic cancer in subcutaneous and orthotopic models. Furthermore, a transgenic murine model of endogenously high 20-HETE level (Tie2-CYP4F2 Tr), exhibited spontaneous liver and mediastinal lymph node metastasis after resection of subcutaneous primary pancreatic tumors. In contrast, wild-type mice did not develop liver and mediastinal lymph node metastasis after primary tumor resection. We show that 20-HETE activated Ras in human pancreatic tumor cell lines and the 20-HETE antagonist, HET0016, decreased Ras activity. The p65 subunit of NF-κB also increased in a 20-HETE-dependent manner in these tumor cell lines. 20-HETE induced migration of human macrophages in vitro, and tumor-associated macrophages expressed the 20-HETE generating enzyme CYP4F2. Depletion of macrophages with clodronate liposomes impaired CYP-metabolite-stimulated tumor growth. In addition, we show that 14,15-EET promotes pancreatic tumor growth in vivo. Moreover, inhibitors of soluble epoxide hydrolase, the enzyme that metabolizes EETs, elevated EET levels and promoted pancreatic tumor growth. Either the 20-HETE antagonist HET0016, or the EET antagonist 14,15-EEZE alone significantly inhibited primary tumor growth. Remarkably, systemic administration of both antagonists together resulted in sustained regression of established pancreatic tumors. This combination of 20-HETE and EET antagonists also suppressed ascites formation and prolonged survival in an orthotopic pancreatic cancer model without toxic effects. Thus, 20-HETE and EET production by macrophages in the tumor microenvironment critically regulates Ras activation, pancreatic tumor growth and metastasis. Our studies offer a mechanistic rationale for using 20-HETE and EET antagonists as a novel approach and anti-cancer therapeutics for pancreatic cancer.

Citation Format: Yael Gus-Brautbar, Jessica Casper, Diane R. Bielenberg, Jennifer Cheng, Birgitta Schmidt, Bruce D. Hammock, Darryl C. Zeldin, Mark W. Kieran, Dipak Panigrahy. The eicosanoid 20-HETE triggers Ras activation, pancreatic cancer growth and metastasis through inflammatory macrophage signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4833. doi:10.1158/1538-7445.AM2014-4833