Novel inhibition of central carbon metabolism pathways by Rac and Cdc42 inhibitor MBQ-167 and paclitaxel.

Triple negative breast cancer (TNBC) represents a therapeutic challenge where standard chemotherapy is limited to paclitaxel. MBQ-167, a clinical stage small molecule inhibitor that targets Rac and Cdc42, inhibits tumor growth and metastasis in mouse models of TNBC. Herein, we investigated the efficacy of MBQ-167 in combination with paclitaxel in TNBC pre-clinical models, as a prelude to safety trials of this combination in advanced breast cancer patients. Individual MBQ-167 or combination therapy with paclitaxel was more effective at reducing TNBC cell viability and increasing apoptosis compared to paclitaxel alone. In orthotopic mouse models of human TNBC (MDA-MB-231 and MDA-MB-468), individual MBQ-167, paclitaxel, or the combination reduced mammary tumor growth with similar efficacy, with no apparent liver toxicity. However, paclitaxel single agent treatment significantly increased lung metastasis, while MBQ-167, single or combined, reduced lung metastasis. In the syngeneic 4T1/BALB/c model, combined MBQ-167 and paclitaxel decreased established lung metastases by ~80%. To determine the molecular basis for the improved efficacy of the combined treatment on metastasis, 4T1 tumor extracts from BALB/c mice treated with MBQ-167, paclitaxel, or the combination were subjected to transcriptomic analysis. Gene set enrichment identified specific downregulation of central carbon metabolic pathways by the combination of MBQ-167 and Paclitaxel but not individual compounds. Biochemical validation, by immunoblotting and metabolic Seahorse analysis, shows that combined MBQ-167 and paclitaxel reduces glycolysis. This study provides a strong rationale for the clinical testing of MBQ-167 in combination with paclitaxel as a potential therapeutic for TNBC and identifies a unique mechanism of action.