Rac1 and Cdc42 as drivers in ovarian cancer metastasis

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.