High-throughput virtual screening and preclinical analysis identifies CB-1, a novel potent dual B-Raf/c-Raf inhibitor, effective against wild and mutant variants of B-Raf expression in colorectal carcinoma

Abstract

Paradoxical Raf activation via Raf dimerization is a major drawback of wild/mutant B-Raf inhibitors. Herein, we report that CB-1 a novel, potent B-Raf/c-Raf dual inhibitor, effective against colon cancer cells, irrespective of their genetic status. High-throughput virtual screening of the ChemBridge library against wild B-Raf (B-RafWT), mutant B-Raf (B-RafV600E), and c-Raf was performed using an automated protocol with the AutoDock-VINA. Caco-2 and HT-29 cells were used. Of the 23,365 compounds screened computationally, CB-1 showed the highest binding energy towards B-RafWT with a ΔGbinding score of − 13.0 kcal/mol. The compound was also predicted to be effective against B-RafV600E and c-Raf molecules with ΔGbinding energies of − 10.6 and − 10.1 kcal/mol, respectively. The compound inhibited B-RafWT, B-RafV600E and c-Raf kinases with IC50 values of 27.13, 51.70, and 40.23 nM, respectively. The GI50 value of CB-1 was 247.9 nM in B-RafWT-expressing Caco-2 cells and 352.4 nM in B-RafV600E-expressing HT-29 cells. Dose-dependent increases in total apoptosis and G1 cell cycle phase arrest was observed in CB-1-treated colon cancer cells. The compound decreased B-Raf expression in both wild and mutant colon cancer cells. CB-1, a novel, potent dual B-Raf/c-Raf inhibitor was effective against colon cancer cells bearing wild-type and mutant variants of B-Raf expression.