Reversal of Multidrug Resistance by Guggulsterone in Drug-Resistant MCF-7 Cell Lines

Background: Multidrug resistance (MDR) presents a serious problem in cancer chemotherapy. Our previous studies have shown that the MDR of K562/DOX cells could be reversed by guggulsterone through inhibiting the function and expression of P-glycoprotein. The purpose of this study was to investigate the reversal effect of guggulsterone on MDR in drug-resistant MCF-7 cells and the parental MCF-7 cells. Methods: MTT cytotoxicity assays, flow cytometry, and Western blot analysis were performed to investigate the antiproliferative effects of the combination of anticancer drugs with guggulsterone, to study the reversal of drug resistance and to examine the inhibitory effects on MRP1 expression. Results: The results showed that co-administration of guggulsterone (10 mu M) resulted in a significant increase in chemosensitivity of MCF-7/DOX cells to doxorubicin, compared with doxorubicin treatment alone (p < 0.01). The fold reversal of 10 mu M guggulsterone (11.48) was comparable to that of 10 mu M verapamil (13.23). Rhodamine123 and doxorubicin accumulation in MCF-7/DOX cells was significantly enhanced after the incubation with guggulsterone (10 mu M), compared with untreated MCF-7/DOX cells (p < 0.01). When doxorubicin (10 mu M) was combined with guggulsterone (10 mu M), the mean apoptotic population of MCF-7/DOX cells was 24.91%. It was increased by 6.15 times, compared with doxorubicin (10 mu M) treatment alone. However, guggulsterone had little inhibitory effect on the expression of MRP1 proteins. Conclusion: Guggulsterone is a novel and potent MDR reversal agent with the potential to be an adjunctive agent for tumor chemotherapy. Copyright (C) 2011 S. Karger AG, Basel