OBJECTIVETo establish human hepatocellular carcinoma multidrug-resistance cell line (HepG2/ADM) and to determine the effect of low-frequency pulse ultrasound (US) on MDR cells and investigate its mechanism.

METHODSUsing gradual increase of adriamycin (ADM) concentrations in culture, an adriamycin-resistant human hepatocellular carcinoma cell sub line (HepG2/ADM) was established in vitro. HepG2/ADM cells were cultured in vitro and randomly divided into 4 groups: the control group (HepG2/ADM only), the group ADM by 1.0 mug/ml adriamycin for 1 h, the group US by low-frequency pulse ultrasound for 10 min, and the group US by low-frequency pulse ultrasound and treated with adriamycin simultaneously at same time. A sonication at a frequency of 0.8 MHz, was delivered with an intensity level of 0.5W/cm2, with continuous exposure of 10 min was applied. The ability of US to induce the apoptosis of MDR was evaluated by analyses of fluorescence microscopy, DNA fragmentation assay and flow cytometry assay.

RESULTSHepG2/Adm was resistant to many anti-tumor agents, and its IC50 of ADM was 26 times higher than that of parent cell line HepG2. Significant over expressions of P-gp, MRP, LRP and GSTs were detected. HepG2/ADM cells radiated by US had the typical characteristics of apoptosis. Compared with the control group (HepG2/ADM, 3.47%); the apoptosis rates were higher in US (12.23%). The therapeutic alliance of US with ADM for MDR cells, have a significant change in the ratio of apoptosis (18.81%, t=1.46 to 5.36, P<0.01).

CONCLUSIONHepG2/ADM could have the biological characteristics of human multidrug-resistance cell line. The US sonication of 0.8 MHz could induce apoptosis of HepG2/ADM cell in vitro, and could act synergistically with Adriamycin.