Characterization of Novel Derivatives of MBQ-167, an Inhibitor of the GTP-binding Proteins Rac/Cdc42

Abstract

Rac and Cdc42, are homologous GTPases that regulate cell migration, invasion, and cell cycle progression; thus, representing key targets for metastasis therapy. We previously reported on the efficacy of MBQ-167, which blocks both Rac1 and Cdc42 in breast cancer cells and mouse models of metastasis. To identify compounds with increased activity, a panel of MBQ-167 derivatives was synthesized, maintaining its 9-ethyl-3-(1H-1,2,3-triazol-1-yl)-9H-carbazole core. Similar to MBQ-167, MBQ-168 and EHop-097, inhibit activation of Rac and Rac1B splice variant and breast cancer cell viability, and induce apoptosis. MBQ-167 and MBQ-168 inhibit Rac and Cdc42 by interfering with guanine nucleotide binding, and MBQ-168 is a more effective inhibitor of PAK (1,2,3) activation. EHop-097 acts via a different mechanism by inhibiting the interaction of the guanine nucleotide exchange factor (GEF) Vav with Rac. MBQ-168 and EHop-097 inhibit metastatic breast cancer cell migration, and MBQ-168 promotes loss of cancer cell polarity to result in disorganization of the actin cytoskeleton and detachment from the substratum. In lung cancer cells, MBQ-168 is more effective than MBQ-167 or EHop-097 at reducing ruffle formation in response to EGF. Comparable to MBQ-167, MBQ-168 significantly inhibits HER2+ tumor growth and metastasis to lung, liver, and spleen. Both MBQ-167 and MBQ-168 inhibit the cytochrome P450 (CYP) enzymes 3A4, 2C9, and 2C19. However, MBQ-168 is ~10X less potent than MBQ-167 at inhibiting CYP3A4, thus demonstrating its utility in relevant combination therapies. In conclusion, the MBQ-167 derivatives MBQ-168 and EHop-097 are additional promising anti metastatic cancer compounds with similar and distinct mechanisms.

Efficacy and delivery strategies of the dual Rac/Cdc42 inhibitor MBQ-167 in HER2 overexpressing breast cancer

“…Our group has developed and characterized MBQ-167, a dual Rac/Cdc42 inhibitor with cell proliferation inhibition at the nanomolar scale capable of reducing tumor growth and metastasis in HER2+ and triple-negative breast cancer cells and mouse models [ 14 , 15 , 22 , 24 ]. Herein, we demonstrate that treating trastuzumab-resistant SKBR3 or the GFP-HER2-BM trastuzumab-resistant metastatic cancer cell line with MBQ-167 reduces cell viability, cell migration and induces apoptosis in a dose-dependent manner.…”

“…As previously described [14] , female SCID mice were inoculated in the fourth right mammary fat pad with 5 × 10 5 cells/mL of GFP-HER2-BM cells in 1:1 Geltrex (Gibco™ Gel-trex™ LDEV-Free Reduced Growth Factor Basement Membrane Matrix Cat. A14132–02): serum free DMEM.…”

“…These receptors, and their signaling, converge on the activation of guanine nucleotide exchange factors (GEFs), which in turn activate Ras-related C3 botulinum toxin substrate (Rac) and its close homolog cell division control protein 42 (Cdc42) by catalyzing the exchange of a GDP molecule for a GTP molecule bound to Rac/Cdc42 [ 12 , 13 ]. Rac and Cdc42 have been extensively studied due to their central role in cell migration, cytoskeleton, and actin organization, vesicle trafficking, cell polarity, apoptosis and metastasis [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] . Hyperactive and overexpressed Rac and Cdc42 have been implicated in cancer cell survival, proliferation and metastasis [ 21 , 22 ].…”

“…US9981980B2) as a specific Rac and Cdc42 inhibitor. MBQ-167 inhibits Rac or Cdc42 activation with IC50s of 103 nM and 78 nM, respectively by blocking guanine nucleotide association [ 14 , 15 ]. Additionally, MBQ-167 inhibits HER2-positive and triple-negative breast cancer tumor growth and both experimental and spontaneous metastasis in mouse xenograft models [ 15 , 24 ].…”

The Rac inhibitor HV-107 as a potential therapeutic for metastatic breast cancer

“…Previously it was shown that inhibition of Rac1 negatively affects the migration of cancerous cells (Montalvo-Ortiz et al 2012 ; Kunschmann et al 2019 ; Medina et al 2022 ). Thus, we tested the potential of HV-107 to inhibit cell migration and extracellular matrix degradation.…”