Cytotoxicity and modes of action of 4′-hydroxy-2′,6′-dimethoxychalcone and other flavonoids toward drug-sensitive and multidrug-resistant cancer cell lines

Introduction: Resistance of cancer to chemotherapy is a main cause in treatment failure. Naturally occurring chalcones possess a wide range of biological activities including anti-cancer effects. In this work, we evaluated the antiproliferative activity of three chalcones [4'-hydroxy-2',6'-dimethoxychalcone (1), cardamomin (2), 2',4'-dihydroxy-3,6'-dimethoxychalcone (3)], and four flavanones [(S)-(-)-pinostrobin (4), (S)-(-)-onysilin (5) and alpinetin (6)] toward nine cancer cell lines amongst which were multidrug resistant (MDR) types. Methods: The resazurin reduction assay was used to detect the antiproliferative activity of the studied samples whilst flow cytometry for the mechanistic studies of the most active molecule (1). Results: IC50 values in a range of 2.54 mu M against CEM/ADR5000 leukemia cells to 58.63 mu M toward hepatocarcinoma HepG2 cells were obtained with 1. The lowest IC50 values of 8.59 mu M for 2 and 10.67 mu M for 3 were found against CCRF-CEM cells leukemia cells, whilst the corresponding values were above 80 mu M for 4 and 6. P-glycoprotein-expressing and multidrug-resistant CEM/ADR5000 cells were much more sensitive toward compound 1 than toward doxorubicin and low cross-resistance or even collateral sensitivity was observed in other drug-resistent cell lines to this compound. Normal liver AML12 cells were more resistant to the studied compounds than HepG2 liver cancer cells, indicating tumor specificity at least to some extent. Compound 1 arrested the cell cycle between Go/G1 phase, strongly induced apoptosis via disrupted mitochondrial membrane potential (MMP) and increased production of reactive oxygen species (ROS) in the studied leukemia cell line. Conclusions: Chalcone 1 was the best tested cytotoxic molecule and further studies will be performed in order to envisage its possible use in the fight against multifactorial resistant cancer cells. (C) 2014 Elsevier GmbH. All rights reserved.