Synthesis and SAR Study of Anticancer Protoflavone Derivatives: Investigation of Cytotoxicity and Interaction with ABCB1 and ABCG2 Multidrug Efflux Transporters.

There is a constant need for new therapies against multidrug-resistant (MDR) cancer. Natural compounds are a promising source of novel anticancer agents. We recently showed that protoflavones display activity in MDR cancer cell lines that overexpress the P-glycoprotein (P-gp) drug efflux pump. In this study, 52 protoflavones, including 22 new derivatives, were synthesized and tested against a panel of drug-sensitive parental cells and their MDR derivatives obtained by transfection with the human ABCB1 or ABCG2 genes, or by adaptation to chemotherapeutics. With the exception of protoapigenone, identified as a weak ABCG2 substrate, all protoflavones bypass resistance conferred by these two transporters. The majority of the compounds were found to exhibit mild to strong (up to 13-fold) selectivity against the MCF-7Dox and KB-V1 cell lines, but not to transfected MDR cells engineered to overexpress the MDR transporters. Our results suggest that protoflavones can overcome MDR cancer by evading P-gp-mediated efflux.