Abstract POSTER-BIOL-1350: Dissecting cellular and molecular consequences of disrupting cyclooxygenase-1 activity in ovarian cancer

Introduction: Cyclooxygenase-1 (COX-1) and COX-2 catalyze the rate-limiting step in the biosynthesis of prostaglandins and thromboxanes, which contribute to tumorigenesis by promoting tumor proliferation, escape from apoptosis, and angiogenesis. COX-1 is overexpressed in multiple human and mouse models of ovarian cancer and that COX-1 inhibition reduces ovarian cancer cell viability in preclinical models; in contrast COX-2 is the principle COX isoform expressed in most solid tumors. Our group has an ongoing interest in developing COX-1-targeted molecules for molecular imaging and therapeutic use. Hypothesis: We hypothesize that COX-1 is a viable molecular target for the treatment of ovarian cancer. To test this hypothesis, we (i) compared expression of COX-1 and COX-2 in The Cancer Genome Atlas (TCGA) ovarian tumors and in an ovarian cancer tissue microarray (TMA) generated in our laboratory, and (ii) determined cellular and molecular effects of disrupting COX-1 activity in ovarian cancer cells. Methods: RNA-seq mRNA data for COX-1 and COX-2 in the PANCAN 12 tumor panel of TCGA was accessed through the Firehose repository (Broad Institute, Cambridge, MA). COX-1 and COX-2 protein expression in our TMA was determined by immunohistochemistry, and percentage of COX-1 and COX-2-positive tumor cells quantified. An ovarian cancer cell line model of disrupted COX-1 activity was generated by the stable integration of shRNA targeting COX-1 in OVCAR-3 cells (ShCOX1). Cell growth in ShCOX1 cells compared to control cells expressing scrambled shRNA (ShSCR) was determined by sulphorhodamine B assay. Differential gene expression between ShSCR and ShCOX1 cells was determined by RNA-seq. Results: TCGA RNA-seq data revealed that COX-1 mRNA levels was significantly higher than COX-2 expression in ovarian cancer and higher than 11 other solid tumor types. We confirmed these findings at the protein level in our TMA. Specific COX-1 knockdown in OVCAR-3 cells significantly reduced growth compared to control cells. Pathway analysis from RNA-seq data revealed that COX-1 knockdown significantly downregulates genes involved in cell proliferation, cell migration/invasion, angiogenesis and epithelial-mesenchymal transition. Conclusions: Our findings confirm that COX-1 is over-expressed in ovarian cancer, and is likely to play a key role in tumor progression through promoting oncogenic tumor growth and progression. Therefore, exploiting high COX-1 expression in ovarian cancer with novel COX-1-targeted molecules has the potential to improve the detection and treatment of this deadly disease. Citation Format: Andrew J. Wilson, Brian D. Lehmann, Qi Liu, MD Jashim Uddin, Anna Elleman, Brenda Crews, Jeanette Saskowski, Jennifer Pietenpol, Lawrence J. Marnett, Dineo Khabele. Dissecting cellular and molecular consequences of disrupting cyclooxygenase-1 activity in ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1350.