Supplemental Table 1: Effect of MBQ-167 on Rho GTPase activity (Active Rho GTPase/Total Rho GTPase) following 24 h in MDA-MB-231 cells, relative to vehicle (=1); Supplemental Table 2: Effect of MBQ-167 on Rac activity (Active Rac/Total Rac) following 24 h in MCF-7 cells; Supplemental Table 3: Optimal %Treated (T)/Control (C) for mammary fat pad tumor growth for EHop-167 treated nude mice; Supplemental Table 4: Tumor growth delay for EHop-167-treated mice
ARTICLE ABSTRACTThe Rho GTPases Rac (Ras-related C3 botulinum toxin substrate) and Cdc42 (cell division control protein 42 homolog) regulate cell functions governing cancer malignancy, including cell polarity, migration, and cell-cycle progression. Accordingly, our recently developed Rac inhibitor EHop-016 (IC50, 1,100 nmol/L) inhibits cancer cell migration and viability and reduces tumor growth, metastasis, and angiogenesis in vivo. Herein, we describe MBQ-167, which inhibits Rac and Cdc42 with IC50 values of 103 and 78 nmol/L, respectively, in metastatic breast cancer cells. Consequently, MBQ-167 significantly decreases Rac and Cdc42 downstream effector p21-activated kinase (PAK) signaling and the activity of STAT3, without affecting Rho, MAPK, or Akt activities. MBQ-167 also inhibits breast cancer cell migration, viability, and mammosphere formation. Moreover, MBQ-167 affects cancer cells that have undergone epithelial-to-mesenchymal transition by a loss of cell polarity and inhibition of cell surface actin-based extensions to ultimately result in detachment from the substratum. Prolonged incubation (120 hours) in MBQ-167 decreases metastatic cancer cell viability with a GI50 of approximately 130 nmol/L, without affecting noncancer mammary epithelial cells. The loss in cancer cell viability is due to MBQ-167–mediated G2–M cell-cycle arrest and subsequent apoptosis, especially of the detached cells. In vivo, MBQ-167 inhibits mammary tumor growth and metastasis in immunocompromised mice by approximately 90%. In conclusion, MBQ-167 is 10× more potent than other currently available Rac/Cdc42 inhibitors and has the potential to be developed as an anticancer drug, as well as a dual inhibitory probe for the study of Rac and Cdc42. Mol Cancer Ther; 16(5); 805–18. ©2017 AACR.