Abstract 3819: COX-2 inhibition with apricoxib drives mesenchymal to epithelial transition and synergizes with anti-VEGF therapy
Authors: Kirane Amanda R. , Dellinger Michael T. , Toombs Jason E. , Burrows Francis J. , Brekken Rolf A. 
Published: August 2012

Abstract
Resistance to standard therapy remains a challenge in treatment of pancreatic ductal adenocarcinoma (PDAC) resulting in need for novel therapeutic strategies. Anti-VEGF therapy with r84 delays PDAC progression; however, chronic hypoxia ultimately results in transition to a mesenchymal phenotype and rapid progression at a later timepoint. COX-2 inhibition with apricoxib, a novel antagonist in Phase II trials, reverses EMT in PDAC cells. We investigate the relationship between COX-2 and VEGF production in PDAC cell lines to evaluate the efficacy of a combination strategy in preclinical models of PDAC. In vitro, changes in VEGF production by PDAC cells following apricoxib were assessed by ELISA at baseline and following forced induction of EMT. The effect of r84, apricoxib, or combination on tumor growth and metastatic incidence was determined in SCID mice with established orthotopic pancreatic xenografts. Improvement of survival and reduction in tumor burden was assessed in a murine genetic model of PDAC using p48-Cre; KrasG12D;Cdkn2alox/lox mice, tissue was collected at 4 weeks of therapy with control antibody, r84 or apricoxib for analysis. PDAC cell lines grown in the presence of TGF-β and collagen demonstrated increased Zeb1 and decreased ECAD expression by Western blot. Treatment with clinically-achievable doses of apricoxib reversed this change in phenotype. High expression of COX-2 correlated with high levels of VEGF in conditioned media in human PDAC cell lines. VEGF production was initially sensitive to COX-2 inhibition, with complete depletion of VEGF in the first 6 hours, but VEGF levels returned to baseline by 16 hours and continued to rise throughout the first 72 hours post apricoxib. Upon repeat dosing at 24 hours, VEGF production had become independent of COX-2 and no changes were observed. Similar results were seen following induction of EMT, however, baseline VEGF production was dramatically increased, and while there was an initial decrease after apricoxib, production remained more than 2-fold higher than in cells under normal culture conditions. In vivo, apricoxib and r84 had minimal effect on primary tumor growth as single agents; however each agent resulted in a reduction of metastatic incidence. Combination therapy reduced primary tumor size and virtually eliminated metastases. Overall survival was significantly improved with apricoxib as a single agent. Apricoxib treated animals also demonstrated a delay in progression of disease and decreased collagen deposition in the microenvironment compared to r84, which increased collagen deposition.We conclude that COX-2 inhibition by apricoxib delays progression of PDAC and results in mesenchymal to epithelial transition. Combination with anti-VEGF therapy results in potent antitumor and antimetastatic effects in our models and warrants further evaluation as a strategy to augment chemotherapy.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3819. doi:1538-7445.AM2012-3819