Background: By integrating extracellular signals with actin cytoskeletal changes, Cdc42 plays important roles in cell physiology and has been implicated in human diseases.Results: A small molecule was found to selectively inhibit Cdc42 in biochemical and cellular assays.Conclusion: The identified compound is a highly Cdc42-selective inhibitor.Significance: The described first-in-class Cdc42 GTPase-selective inhibitor will have applications in drug discovery and fundamental research.

Cdc42 (cell division control protein 42) and Rac1 (Ras-related C3 botulinum toxin substrate 1) are attractive therapeutic targets in ovarian cancer based on established importance in tumor cell migration, adhesion and invasion. Despite a predicted benefit, targeting GTPases has not yet been translated to clinical practice. We previously established that Cdc42 and constitutively active Rac1b are overexpressed in primary ovarian tumor tissues. Through high throughput screening and computational shape homology approaches we identified R-ketorolac as a Cdc42 and Rac1 inhibitor; distinct from the anti-inflammatory, cyclooxygenase inhibitory activity of S-ketorolac. In the present study, we establish R-ketorolac as an allosteric inhibitor of Cdc42 and Rac1. Cell-based assays validate R-ketorolac activity against Cdc42 and Rac1. Studies on immortalized human ovarian adenocarcinoma cells (SKOV3ip), and primary, patient-derived ovarian cancer cells show R-ketorolac is a robust inhibitor of growth factor or serum dependent Cdc42 and Rac1 activation with a potency and cellular efficacy similar to small molecule inhibitors of Cdc42 (CID2950007/ML141) and Rac1 (NSC23766). Furthermore, GTPase inhibition by R-ketorolac reduces downstream p21-activated kinases (PAK1/PAK2) effector activation by >80%. Multiple assays of cell behavior using SKOV3ip and primary patient-derived ovarian cancer cells show that R-ketorolac significantly inhibits cell adhesion, migration and invasion. In sum, we provide evidence for R-ketorolac as direct inhibitor of Cdc42 and Rac1 that is capable of modulating downstream GTPase-dependent, physiological responses, which are critical to tumor metastasis. Our findings demonstrate the selective inhibition of Cdc42 and Rac1 GTPases by an FDA approved drug-racemic ketorolac that can be used in humans.

PURPOSE We previously identified the R-enantiomer of ketorolac as an inhibitor of the Rho-family GTPases Rac1 and Cdc42. Rac1 and Cdc42 regulate cancer-relevant functions including cytoskeleton remodeling necessary for tumor cell adhesion and migration. This study investigated whether administration of racemic (R,S) ketorolac after ovarian cancer surgery leads to peritoneal distribution of R-ketorolac, target GTPase inhibition in cells retrieved from the peritoneal cavity, and measureable impact on patient outcomes. EXPERIMENTAL DESIGN Eligible patients had suspected advanced stage ovarian, fallopian tube or primary peritoneal cancer. Secondary eligibility was met when ovarian cancer was confirmed and optimally debulked, an intraperitoneal port was placed, and there were no contraindications for ketorolac administration. R- and S-ketorolac were measured in serum and peritoneal fluid, and GTPase activity was measured in peritoneal cells. A retrospective study correlated peri-operative ketorolac and ovarian cancer-specific survival in ovarian cancer cases. RESULTS Elevated expression and activity of Rac1 and Cdc42 was detected in ovarian cancer patient tissues, confirming target relevance. Ketorolac in peritoneal fluids was enriched in the R-enantiomer and peritoneal cell GTPase activity was inhibited after ketorolac administration when R-ketorolac was at peak levels. After adjusting for age, AJCC stage, completion of chemotherapy, and neo-adjuvant therapy, women given peri-operative ketorolac had a lower hazard of death (Hazard Ratio=0.30 [95%CI 0.11–0.88]). CONCLUSION Ketorolac has a novel pharmacologic activity conferred by the R-enantiomer and R-ketorolac achieves sufficient levels in the peritoneal cavity to inhibit Rac1 and Cdc42, potentially contributing to the observed survival benefit in women who received ketorolac.

The revised Fig. 1A correctly shows CID44216842 as a 3-methoxyphenyl analog and not a 4-methoxyphenyl analog as originally published. The correction does not impact the interpretations or conclusions of the article.

Fatal metastasis occurs when circulating tumor cells (CTCs) disperse through the blood to initiate a new tumor at specific sites distant from the primary tumor. CTCs have been classically defined as nucleated cells positive for epithelial cell adhesion molecule and select cytokeratins (EpCAM/CK/DAPI), while negative for the common lymphocyte marker CD45. The enumeration of CTCs allows an estimation of the overall metastatic burden in breast cancer patients, but challenges regarding CTC heterogeneity and metastatic propensities persist, and their decryption could improve therapies. CTCs from metastatic breast cancer (mBC) patients were captured using the RareCyteTM Cytefinder II platform. The Lin− and Lin+ (CD45+) cell populations isolated from the blood of three of these mBC patients were analyzed by single-cell transcriptomic methods, which identified a variety of immune cell populations and a cluster of cells with a distinct gene expression signature, which includes both cells expressing EpCAM/CK (“classic” CTCs) and cells possessing an array of genes not previously associated with CTCs. This study put forward notions that the identification of these genes and their interactions will promote novel areas of analysis by dissecting properties underlying CTC survival, proliferation, and interaction with circulatory immune cells. It improves upon capabilities to measure and interfere with CTCs for impactful therapeutic interventions.