Flavonoid Monomers as Potent, Nontoxic, and Selective Modulators of the Breast Cancer Resistance Protein (ABCG2)

Abstract

We synthesize various substituted triazole-containing flavonoids and identify potent, nontoxic, and highly selective BCRP inhibitors. Ac18Az8, Ac32Az19, and Ac36Az9 possess m-methoxycarbonylbenzyloxy substitution at C-3 of the flavone moiety and substituted triazole at C-4′ of the B-ring. They show low toxicity (IC50 toward L929 > 100 μM), potent BCRP-inhibitory activity (EC50 = 1–15 nM), and high BCRP selectivity (BCRP selectivity over MRP1 and P-gp > 67–714). They inhibit the efflux activity of BCRP, elevate the intracellular drug accumulation, and restore the drug sensitivity of BCRP-overexpressing cells. Like Ko143, Ac32Az19 remarkably exhibits a 100% 5D3 shift, indicating that it can bind and cause a conformational change of BCRP. Moreover, it significantly reduces the abundance of functional BCRP dimers/oligomers by half to retain more mitoxantrone in the BCRP-overexpressing cell line and that may account for its inhibitory activity. They are promising candidates to be developed into combination therapy to overcome MDR cancers with BCRP overexpression.

Characterization of a Potent, Selective, and Safe Inhibitor, Ac15(Az8)2, in Reversing Multidrug Resistance Mediated by Breast Cancer Resistance Protein (BCRP/ABCG2)

“…The membrane fraction of S1M180 cells was prepared as previously reported [ 48 ]. Around 5 × 10 7 cells of S1M180 were resuspended in 5 mL homogenization buffer (0.33 M sucrose, 300 mM Tris pH7.4, 1 mM EDTA, 1 mM EGTA, 2 mM DTT, 100 mM 6-aminocaproic acid, 1 mM PMSF, and 1X protease inhibitor (cOmplete™ Protease Inhibitor Cocktail Tablets, Roche) and lysed using a Branson SFX550 sonicator for 10 cycles at 50% amplitude with 30 s on/30 s off.…”

“…Membrane fraction of cells was collected by ultracentrifugation of cell lysate at 45,000 rpm using Himac CP70G (Hitachi) for 1.5 h. Membrane fraction pellet was re-suspended in 300 µL of ATPase assay buffer (50 mM Tris at pH7.5, 2 mM EGTA at pH 7.0, 2 mM DTT, 50 mM KCl, 10 mM MgCl 2 , 5 mM sodium azide, and 1 mM ouabain). Vanadate-sensitive BCRP-ATPase activity of Ac15(Az8) 2 or Ko143 was conducted as previously reported [ 48 ]. In brief, membrane fraction was pre-incubated with or without 0.3 mM sodium ortho vanadate and respective tested compounds for 30 min.…”

Identification of Binding Sites in the Nucleotide-Binding Domain of P-Glycoprotein for a Potent and Nontoxic Modulator, the Amine-Containing Monomeric Flavonoid FM04

“…After 5 days, the percentage of survival and the EC 50 of the modulator was determined by MTS according to procedures reported previously. 55 4.6. Photo-Crosslinking of FM04 Photoaffinity Derivatives with LCC6 and LCC6MDR Cells.…”

“…The P-gp ATPase activity was determined according to the previously reported procedures. 55 The P-gp transfected HEK293FT cells were resuspended in homogenization buffer (330 mM sucrose, 300 mM Tris−HCl, pH 7.4, 1 mM EDTA, 1 mM EGTA, 2 mM DTT, 100 mM 6-aminocaproic acid, 1 mM PMSF, and 1X protease inhibitor) and lysed by a sonicator (QSONICA) at 10 kHz for 10 min (30 s on/ 30 s off).…”

Imidazo[1,2-a]Pyridine Derivatives as Novel Dual-Target Inhibitors of ABCB1 and ABCG2 for Reversing Multidrug Resistance

“…However, no specific inhibitor of ABCB1 has been successful in clinical trials. Thus potent ABCB1 inhibitors with low toxicity and nonclinical drug–drug interaction are crucial for the treatment of MDR of malignant tumors. − Compared with ABCB1, the research on ABCG2 is still at an early stage. − As the first identified ABCG2 inhibitor fumitremorgin C and its analogue Ko143 were precluded from the clinical study due to their unsatisfied drug properties, researchers focused on the discovery of novel ABCG2 inhibitors with high activity and safety, such as quinazolines derivative compound 41 (Figure B). − Therefore, to solve the MDR problem caused by drug efflux more effectively, the development of effective and nontoxic ABC transporter inhibitors is highly pursued for clinical applications.…”