Abstract POSTER-BIOL-1320: Rho-family GTPases as therapeutic targets in ovarian cancer

Purpose of the study: Although Rac1 and Cdc42 are considered attractive therapeutic targets, no selective inhibitors of these GTPases are in clinical trials. The Ras-homologous (Rho) family GTPases Rac1 and Cdc42 contribute to metastatic dissemination through regulation of actin reorganization, cell motility, cell-cell and cell-extracellular matrix adhesion. Using high throughput screening and cheminformatics, we identified the R-enantiomer of ketorolac as a novel inhibitor of Rac1 and Cdc42. R-enantiomers of nonsteroidal anti-inflammatory drugs are poor inhibitors of cyclooxygenase (COX) activity, yet little is known about the pharmacologic activities or targets of the R-enantiomers. The purpose of this study was to investigate the effects of R-ketorolac on ovarian cancer. Experimental procedures: GTPase target expression and activity was determined by immunohistochemistry, RT-PCR and enzymatic assays. The effects of racemic, R- and S-ketorolac on proliferation, adhesion and migration were investigated using human ovarian tumor cells (OvCA 429 and SKOV3ip). In vivo effect of ketorolac treatments was determined in a xenograft model using SKOV3ip cells. Pharmacokinetic and pharmacodynamic assessments of racemic R/S-ketorolac (Toradol®) in patients were conducted in women with suspected advanced stage ovarian, fallopian tube or primary peritoneal cancer with planned optimal cytoreductive surgery. Ascites samples were obtained for measurement of cell adhesion and drug inhibition of GTPase activity. After placement of an IP port the recommended dose of IV racemic ketorolac was administered and blood and peritoneal fluid were obtained at T=0, 1h, 6h and 24h. R- and S-ketorolac concentrations in serum and peritoneal fluid were measured by HPLC. GTPase inhibitory activity of ketorolac was assessed in peritoneal tumor cells. Summary of the data: Elevation of Cdc42 protein and expression of the constitutively active Rac1b splice variant of Rac1 were detected in ovarian cancer specimens providing the first evidence for dysregulation of these GTPase targets in ovarian cancer. R-ketorolac, and not S-ketorolac, inhibits Rac1 and Cdc42 activity demonstrating an unexpected pharmacologic activity for the R-enantiomer. R-ketorolac, but not S-ketorolac, inhibits cell adhesion and migration, and reduced peritoneal tumor implantation in a mouse xenograft model. In the clinical studies using R/S-ketorolac for post-operative pain management, we found that ketorolac distributed to peritoneal fluids within 6 hours and fluids were highly enriched in the R-enantiomer compared to the S-enantiomer. Rac1 and Cdc42 activity was inhibited in ovarian tumor cells retrieved from the peritoneal cavity post-ketorolac administration. Cell adhesion was decreased by R-ketorolac in patient-derived ovarian tumor cells. Conclusions: The findings show R-ketorolac is a novel inhibitor of Rac1 and/or Cdc42, and active in ovarian cancer model systems. The favorable distribution of R-ketorolac in the peritoneal cavity coupled with GTPase inhibition in cells retrieved from the intraperitoneal compartment support the potential benefit of R-ketorolac for ovarian cancer patients. Citation Format: Hudson LG, Kenney SR, Guo Y, Adams S, Rutledge T, Muller CY, Wandinger-Ness A. Rho-family GTPases as therapeutic targets 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-1320.