Abstract 3994: Anti-metastatic drug MBQ-167 regulates cell polarity via Cdc42

Cdc42 (cell division control protein 42 homolog) is a Rho GTPase highly conserved among eukaryotes in structure and function. Mechanical or chemical cues in the microenvironment stimulate the localized activation of Cdc42, aiding cells to polarize and arrange their components accordingly. Its role in cell polarity was first described in budding yeast and subsequently in other eukaryotes, including animal cells determining the direction of motility. Accordingly, in cancer Cdc42 mediates migration, invasion, and spread of tumor cells. Therefore, we target Cdc42 as therapeutic strategy to treat metastatic breast cancer. Our group designed and characterized the small molecule MBQ-167 as a potent inhibitor against Cdc42 activation (IC50=0.1 µM), demonstrating its effectiveness in preventing tumor growth and cell migration in vitro and in vivo. Because in yeast S. cereviciae Cdc42 is well known for regulating the location of budding events, we used this well-characterized model of cell polarization to test our previous findings of MBQ-167 and its specificity for Cdc42. By using a tetracycline-controlled transcriptional inactivation (Tet-Off) system at the promoter region of the CDC42 gene of yeast, we knocked down Cdc42 supplementing the media with doxycycline (DOX; IC=10ug/uL). Next, we analyzed the growth, budding pattern, and Cdc42 activity of budding yeast exposed to DOX, MBQ-167 or in combination. The maximum growth, doubling time and budding polarity of recombinant yeast with the Tet-Off system were reduced when treated with DOX (EC50=10ug/mL), as expected. The same effect was seen in the group treated with MBQ-167 (ED50=100uM), both alone and in combination with DOX. Ultimately, pull-down assays of the active Cdc42-GTP complex confirmed our hypothesis that MBQ-167 disrupts cell polarity through impeding Cdc42 activation. Here we validated MBQ-167 as a Cdc42 inhibitor in another biologic context. and present a method for screening Cdc42 inhibitors and potential therapeutics against metastatic cancer. Citation Format: Michael John Rivera-Robles, Julia Medina-Velázquez, Gabriela M. Asencio-Torres, Sahily González-Crespo, Brian C. Rymond, José Rodríguez-Medina, Suranganie Dharmawardhane. Anti-metastatic drug MBQ-167 regulates cell polarity via Cdc42 [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 3994.