The Rac Inhibitor EHop-016 Inhibits Mammary Tumor Growth and Metastasis in a Nude Mouse Model

Metastatic disease still lacks effective treatments, and remains the primary cause of Cancer mortality. Therefore, there is a critical need to develop better strategies to inhibit metastatic Cancer. The Rho family GTPase Rac is an ideal target for anti-metastatic Cancer therapy, because Rac is a key molecular switch that is activated by a myriad of cell surface receptors to promote Cancer cell migration/invasion and survival. Previously, we reported the design and development of EHop-016, a small molecule compound, which inhibits Rac activity of metastatic Cancer cells with an IC50 of 1 μM. EHop-016 also inhibits the activity of the Rac downstream effector p21-activated kinase (PAK), lamellipodia extension, and cell migration in metastatic Cancer cells. Herein, we tested the efficacy of EHop-016 in a nude mouse model of experimental metastasis, where EHop-016 administration at 25 mg/kg body weight (BW) significantly reduced mammary fat pad tumor growth, metastasis, and angiogenesis. As quantified by UPLC MS/MS, EHop-016 was detectable in the plasma of nude mice at 17 to 23 ng/ml levels at 12 h following intraperitoneal (i.p.) administration of 10 to 25 mg/kg BW EHop-016. The EHop-016 mediated inhibition of angiogenesis In Vivo was confirmed by immunohistochemistry of excised tumors and by In Vitro tube formation assays of endothelial cells. Moreover, EHop-016 affected cell viability by down-regulating Akt and Jun kinase activities and c-Myc and Cyclin D expression, as well as increasing Caspase 3/7 activities in metastatic Cancer cells. In conclusion, EHop-016 has potential as an Anticancer compound to block Cancer progression via multiple Rac-directed mechanisms.