Abstract 3480: COX-2 alters the metabolic secretome in triple negative human breast cancer xenografts
Authors: Bharti Santosh Kumar , Winnard Paul T. , Mironchik Yelena , Dore-Savard Louis , Krishnamachary Balaji , Bhujwalla Zaver M. 
Published: August 2018

Abstract
Cyclooxygenase-2 (COX-2) is an active mediator of the inflammatory response of cells and plays an important role in the development, progression, invasion, and metastasis of cancers including breast cancer [1]. Tumor interstitial fluid (TIF), the milieu that contains the tumor secretome, is one of the least examined aspects of the TME because of the difficulty in sampling this fluid from tumors. Here, for the first time, we have sampled TIF from COX-2 overexpressing triple negative SUM-149 human breast cancer xenografts and empty vector SUM-149 xenografts.
The cloning, construction of a lentivirus vector expressing COX-2 gene, and the establishment of SUM-149 cells stably overexpressing COX-2 (SUM-COX-2) were reported by us previously[2]. A home-built TIF collection chamber was inserted subcutaneously in female SCID mice with 4-6 1-2 mm tumor pieces packed around the chamber. Once tumors were ~ 400 mm3, TIF was collected from chambers. Each chamber yielded ~50μL of TIF that was analyzed with high-resolution 1H magnetic resonance spectroscopy (MRS) at 750 MHz.
SUM-COX-2 tumors showed consistently higher COX-2 expression compared to SUM-EV tumors. COX-2 overexpression resulted in a significant increase of lactate, glutamate, acetate, and succinate, and a significant decrease of glucose, glutamine, citrate, formate, and lipids; pyruvate tended to decrease. The changes in lactate and lipids are consistent with our earlier observations where COX-2 downregulation in triple negative MDMB-231 human breast cancer cells resulted in a significant decrease of lactate and an increase of lipids and lipid droplets in intact perfused cells[3]. Here, COX-2 overexpression increased glycolysis. Depletion of pyruvate observed here in COX-2 overexpressing cells would limit production of acetyl-CoA and consequently citrate to diminish fatty acid synthesis/lipids. Increased succinate parallels the increase in glutamate/α-ketoglutarate, the upstream intermediate to succinate in the tricarboxylic acid cycle [1], and indicates increased utilization/depletion of glutamine to supplement the TCA cycle. Importantly, accumulation of succinate inhibits HIF-1α prolyl hydroxylase that stabilizes HIF-1α driven cancer promoting metabolic pathways such as enhanced glycolysis and increased ROS[4]. Moreover, increased succinate also through the succinate/succinate dehydrogenase reaction, provides necessary electrons to the electron transport chain upstream of the COX-2 reaction[5]. These data provide new insights into the role of COX-2 in the metabolic secretome and tumor metabolism, and identify metabolic pathways as potential targets for reducing the effects of COX-2 expression in cancer.
Ref.
1. Wang et. al. Nat. Rev. Can. 2010
2. Krishnamachary et al. Oncot. 2017
3. Shah et al. NMR Biomed. 2012
4. Selak et al. Can Cell. 2005
5. Mills et al. Trd in Cell Bio. 2014
Citation Format: Santosh Kumar Bharti, Paul T. Winnard, Yelena Mironchik, Louis Dore-Savard, Balaji Krishnamachary, Zaver M. Bhujwalla. COX-2 alters the metabolic secretome in triple negative human breast cancer 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 3480.