As expected, EHop-016 inhibited the aggregation of endothelial cells into tubes. At 4 μM EHop-016, there was reduced tube formation, which was impaired at 8 μM, the concentration at which we observed a 50% reduction in Rac activity. (Figure 3B). Since Racs [1] and [2] play an essential role in blood vessel morphogenesis via integrin signaling and endothelial cell proliferation/adhesion/migration Raf phosphorylation mechanisms [63], [64] and [65], we expect EHop-016 to additionally block tumor growth by reducing their blood

supply via inhibition of the Rac activity of endothelial cells. In this study, for the first time, we have shown that EHop-016 can be used effectively to block mammary tumor progression to metastasis. This anticancer activity of EHop-016 is predicted to be due to inhibition of Rac, and possibly Cdc42, activities in the human breast cancer cells as well as the endothelial cells in the tumor microenvironment. Therefore, EHop-016 may inhibit mammary tumor growth via multiple mechanisms of blocking the growth and migration of tumor cells and endothelial cells. Future studies will Venetoclax mouse investigate the effect of EHop-016 on additional cells in the tumor microenvironment, such as macrophages and neutrophils as well as T and B lymphocytes that are regulated by Vav1/Rac2

signaling [66]. Recent studies have documented the utility of inhibiting Rac and Cdc42 to reduce tumor growth and metastasis in xenograft models. Another NSC23766 analog AZA1 (at 100 μg/day) was shown to inhibit

Rac1 and Cdc42 in prostate cancer cells and reduce tumor growth via inhibition of Rac/Cdc42/PAK signaling to the actin cytoskeleton as well as Akt and Cyclin D to reduce cell survival and induce cell death [46]. The Rac GEF inhibitor ZINC639391 at 25 mg/kg BW, and its analog IA-116 at 3 mg/kg BW, resulted in reduced lung metastases from spontaneous metastases assays [47]. Similarly a Cdc42 specific inhibitor, AZA197, suppressed colon cancer growth via down-regulation of PAK and ERK activities, and Cyclin D1 expression [48]. Therefore, we expect EHop-016 to inhibit mammary tumor progression via multiple Rac/Cdc42/PAK-mediated signaling mechanisms. To understand the mechanism by which EHop-016 reduces tumor growth, we investigated Lck the effect of EHop-016 on apoptosis and cell survival signaling In Vitro. As previously shown by us, at concentrations ≥ 10 μM EHop-016 inhibits Rac and PAK activities by ~ 100% and Cdc42 activity by 75%, and reduces cell viability [52]. Figure 4 shows that in MDA-MB-435 metastatic cancer cells, at concentrations ≥ 10 μM, EHop-016 increases caspase 3/7 activity in a statistically significant (P < .05) and concentration-dependent manner with a maximum 1.6-fold induction at 25 μM, at concentrations that inhibit both Rac and Cdc42.