title: Flavonoid dimers as bivalent modulators for p-glycoprotein-based multidrug resistance: structure-activity relationships.
abstract: We recently described the modulatory activities of apigenin homodimers linked by ethylene glycol units in multidrug- resistant breast cancer and leukemic cells overexpressing ABCB1 (P-glycoprotein, P-gp). To further improve the potency of these dimers, a small library of flavonoid homodimers and heterodimers were synthesized, and their in vitro activity in reversing cellular resistance to paclitaxel, along with structure-activity relationships (SAR), were evaluated using a P-gp-expressing human breast cancer cell line. Among these synthesized homodimers, many showed more potent reversing activity than that of the parent compound and verapamil. Two compounds in particular showed promising reversing activity at sub-micromolar concentrations with no cytotoxic effects. Regarding SAR trends, flavonoid dimers with nonpolar and hydrophobic substituents (e.g., methyl and ethyl groups) generally showed more potent resistance-reversing activity than that of dimers with polar and hydrophilic substituents (e.g. hydroxy groups) at the C3, C6, and C7 positions, but not at C5. In terms of substituent steric bulk at C6, it was found that the flavonoid dimer with methyl groups was optimal, with bulkier substituents leading to lower reversing activity. Comparisons of flavonoid heterodimers with the corresponding homodimers revealed that the two binding sites on P-gp for flavonoid moieties are quite similar to each other. Besides paclitaxel, these new compounds also increased drug accumulation and enhanced the cytotoxicity of other cancer drugs such as doxorubicin, vincristine, and vinblastine by decreasing the IC(50) values 4-45-fold.
authors.affiliation: Department of Applied Biology and Chemical Technology and Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong Polytechnic University, Hong Kong SAR.
authors.forename: Kin-Fai
authors.initials: KF
authors.lastname: Chan
authors.forename: Yunzhe
authors.initials: Y
authors.lastname: Zhao
authors.forename: Toby W S
authors.initials: TW
authors.lastname: Chow
authors.forename: Clare S W
authors.initials: CS
authors.lastname: Yan
authors.forename: Dik Lung
authors.initials: DL
authors.lastname: Ma
authors.forename: Brendan A
authors.initials: BA
authors.lastname: Burkett
authors.forename: Iris L K
authors.initials: IL
authors.lastname: Wong
authors.forename: Larry M C
authors.initials: LM
authors.lastname: Chow
authors.forename: Tak Hang
authors.initials: TH
authors.lastname: Chan
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000378:metabolism; D047310:Apigenin / Q000737:chemistry; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019281:Dimerization; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D005419:Flavonoids / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D008872:Microwaves; D015394:Molecular Structure; D017239:Paclitaxel / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005419:Flavonoids; D047310:Apigenin; D017239:Paclitaxel