Reversal of P-glycoprotein-mediated multidrug resistance by 5,6,7,3',4'-pentamethoxyflavone (Sinensetin).
Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly with chemosensitizers. In this study, chemosensitizing effects of 5,6,7,3',4'-pentamethoxyflavone (sinensetin) and its analogs were investigated with respect to in vitro efficacy and structure-activity relationship. Sinensetin reversed the resistance of P-glycoprotein (Pgp)-overexpressing AML-2/D100 to vincristine in a concentration-dependent manner. Chemosensitizing effect of sinensetin was 10- and 18-fold higher than those of 5,7,3',4'-tetramethoxyflavone and 3,7-dihydroxy-3',4'-dimethoxyflavone, respectively. Sinensetin cytotoxicity in AML-2/D100 was not changed by the complete inhibition of Pgp, suggesting that it is not a substrate for Pgp. Flow cytometry showed that sinensetin increased drug accumulation in the AML-2/D100 in a concentration-dependent manner. Unlike verapamil and cyclosporin A, the maximum non-cytotoxic concentrations of sinensetin were found to decrease the Pgp levels. Azidopine-binding assay showed that cyclosporin A or verapamil inhibited azidopine binding on Pgp partially but sinensetin did not. Taken together, these results suggest that sinensetin has a chemosensitizing effect in reversing Pgp-mediated MDR by increasing the intracellular accumulation of drugs without competition in a binding site of azidopine. Thus, sinensetin is anticipated as a novel and highly potent second-generation flavonoid chemosensitizer, since sinensetin has significant advantages of having a high therapeutic index, of being a non-transportable inhibitor, and of effecting no induction of Pgp.
Choi
Cheol Hee
CH
Kolon Central Research Park, Yongin-City, Republic of Korea. chchoi@mail.chosun.ac.kr
Sun
Kyung Hoon
KH
An
Chun San
CS
Yoo
Jin Cheol
JC
Hahm
Kyung Soo
KS
Lee
In Hwa
IH
Sohng
Jae Kyung
JK
Kim
Youn Chul
YC
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple; D005419:Flavonoids / Q000494:pharmacology*; D006461:Hemolysis; D020128:Inhibitory Concentration 50; D008956:Models, Chemical; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011794:Quercetin / Q000494:pharmacology; D020112:Rhodamine 123 / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005419:Flavonoids; D020112:Rhodamine 123; C059295:sinensetin; D011794:Quercetin