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Aberrant Rac1 signaling contributes to cancer growth and metastasis, therefore, we investigated the effect of altering Rac1 expression and activity to pinpoint which metastatic processes and tumor microenvironment immune factors are influenced by Rac1 signaling. We have identified that the R- enantiomer of ketorolac, a drug given for pain management, is a Rac1 and Cdc42 selective inhibitor. In a retrospective study, we found that treatment with racemic ketorolac significantly increased the survival probability of ovarian cancer patients. RNA seq analyses of ascites tumor cell samples from ovarian cancer patients in a prospective study receiving racemic ketorolac for clinically indicated use in pain relief, showed significant downregulation of genes involved in endocytosis, regulation of actin cytoskeleton, ER protein processing, TNF and NOD signaling. To further distinguish the activities most directly regulated by Rac1 and important in ovarian cancer, we tested the impact of manipulating the expression of Rac1 in ovarian cancer cells on adhesive and invasive cell behaviors, as well as the impacts of gene expression relative to ketorolac treatment. Using electric cell-substrate impedance sensing (ECIS), Rac1 overexpression resulted in increased cell-cell barrier formation and cell adhesion. Whereas, CRISPR-CAS9 mediated knockdown of Rac1 resulted in decreased cell adhesion. Using Matrigel invasion chambers and mesothelial clearance assays, Rac1 overexpression led to increased ovarian cancer cell invasion when compared to parental and Rac1 knockdown cell lines. Furthermore, intraperitoneal growth of ovarian cancer cells overexpression Rac1 relative to parental control lines increased tumor burden in vivo. Conversely, with knockdown of Rac1, tumor burden and omental adhesion was decreased, as quantified using IVIS bioluminescence imaging. RNA seq analyses of tumors manipulated for Rac1 as compared to R-ketorolac will be presented. The composite data indicate that targeting Rac1 in ovarian cancer with R-ketorolac or otherwise has therapeutic benefit in decreasing tumor cell dissemination and metastasis. Citation Format: Melanie Rivera, Martha M. Grimes, Laurie G. Hudson, Angela Wandinger-Ness. Rac1 as a driver and therapeutic target in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2898.

Five-year ovarian cancer patient survival has not improved for decades, largely due to disease recurrence. Therefore, drivers of relapse need to be identified. We first reported that Rac1 and Cdc42 GTPases are highly overexpressed in serous ovarian cancer using immunohistochemistry. To correlate GTPase expression with survival outcomes, we analyzed gene expression data in The Cancer Genome Atlas, revealing that ovarian cancer patients with the highest RAC1 RNA levels had significantly worse age-adjusted survival than those with low RAC1. Quantitative analyses of Rac1b, a constitutively active Rac1 splice variant, show dramatic overexpression in tumor epithelia relative to stroma and normal epithelia. Since high Rac1 and Cdc42 levels drive cancer cell adhesion, invasion and metastasis, we used multiple assays to assess the dependence of ovarian cancer cell behaviors on Rac1 and Cdc42. Using Matrigel invasion chambers, treatment of multiple ovarian cancer cell lines with specific Rac1 and Cdc42 inhibitors resulted in significantly decreased cellular invasion. Conversely, with overexpression of Rac1, ovarian cancer cells demonstrated increased invasion. Furthermore, IP injection of ovarian cancer cells overexpressing Rac1 resulted in increased adhesion, invasion and metastasis in the omentum and peritoneum in vivo. These data support Rac1 and Cdc42 as important drivers of invasive and metastatic ovarian cancer and as novel high-value therapeutic targets with potential impact in reducing disease metastasis. Citation Format: Melanie Rivera, Dayna Dominguez, Christine Pauken, Elsa Romero, S. Ray Kenney, Yang Shi, Ji-Hyun Lee, Jennifer Gillette, Laurie G. Hudson, Angela Wandinger-Ness. Rac1 and Cdc42 as drivers in ovarian cancer metastasis [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 3159.