['To prove that DNA damage, intracellular reactive oxygen species (ROS) generation and loss of mitochondrial membrane potential (MMP) are contributing factors for the inhibition of cell proliferation induced by doxorubicin (DOX) administration combined with microbubble-assisted low-level therapeutic ultrasound (US) in K562 cells.', '3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay was adopted to examine cytotoxicity of different treatments. Changes on apoptosis and necrosis rates, DNA fragmentation, intracellular reactive oxygen species production, mitochondrial membrane potential, cellular membrane permeability and DOX-uptake were analysed by flow cytometry. Nuclear morphology changes were observed under a fluorescence microscope. Ultrasonic cavitation was measured by spectrofluorimetry.', 'Under optimal conditions, MB-US significantly aggravated DOX-induced K562 cell death, especially necrosis, when compared with either monotherapy. Synergistic potentiation on DNA damage, ROS generation and MMP loss were observed. Ultrasonic cavitation effects, plasma membrane permeabilization and DOX-uptake were notably improved after MB-US exposure.'] Does activation of microbubbles by low-level therapeutic ultrasound enhance the antitumor effects of doxorubicin?