ABSTRACT
Objective To explore whether the low-intensity pulsed ultrasound (LIPU) could induce apoptosis on SMMC-7721 cells and to explore the underlying mechanism.Methods The SMMC-7721 cells were randomly divided into 4 groups:a blank control group,which was subject to sham exposure to ultrasound,and 3 ultrasound intervention groups exposed to ultrasound at intensities of 0.5,1.3 and 2.0 W/cm2,respectively.Then they were incubated for 6 h.The cell apoptosis,necrosis and changes of cell cycles were measured using the flow cytometry.The transmission electron microscope (TEM) was used to observe microstructural changes in the cells.The agarose gel electrophoresis (AGE) was used to examine the DNA fragmentation,and Western-blotting was employed to assess the protein expression of caspase-3.Results The average cell apoptosis rate of the 3 intervention groups were 4.66％,8.99％ and 32.41％,respectively.The percentage of cells in G2 phase increased significantly and those in G1 phase decreased significantly in the 3 intervention groups compared to the blank control group at the same time points.In the intervention groups,significant cell apoptosis was observed under TEM,and DNA ladders was seen in AGE,with DNA fragments appearing obviously when cells were incubated for 6 h and 9 h after ultrasound exposure.In intervention groups subject to 1.3 and 2.0 W/cm2 ultrasound exposure,the protein expression of caspase-3 was significantly higher than that of the control group.Conclusion LIPU can inhibit the proliferation and induce apoptosis of SMMC-7721 cells with a dose-dependent feature.The possible mechanism underlying the LIPU-induced cell apoptosis might be related to the activation of the mitochondria pathway,and especially the caspase-3 protein.
ABSTRACT
Background and purpose:Low intensity ultrasound (LIUS) can kill cancer cells and promote their apoptosis. However, it is still unknown how it affects the migration and invasion of tumor cells. This study aimed to explore the effect of LIUS on human hepatocellular line MHCC97H in migration and metastasis and the possible mechanismin vitro.Methods:According to the intensity of ultrasonic irradiation, 4 experimental groups were established: control group (0 W/cm2), 0.5 W/cm2, 1.0 W/cm2 and 1.5 W/cm2group. The migration and invasion ability of hepatocellular cells was detected by scratch assay and Transwell migration and invasion assay after the irradiation of LIUS. The changes of cytoskeleton after irradiation were observed by microscope and F-actin green lfuorescence staining. The expressions of MMP-2 and MMP-9 were examined by real-time lfuorescent quantitative polymerase chain reaction (RTFQ-PCR) and Western blot.Results:Low intensity ultrasound (≤1.5 W/cm2) promoted the migration and invasion of hepatocellular line MHCC97H. Scratch assay and Transwell assay showed much more cells under irradiation migrated through membrane than untreated. It was found that morphology of liver cancer cells changed after LIUS irradiation using optical microscope and lfuorescence microscope. The results of RTFQ-PCR and Western blot showed upregulation of MMP-2 expression by LIUS in MHCC97H and high expression of MMP-9 mRNA. Conclusion:Low intensity ultrasound may promote the migration and invasion of MHCC97H through changing cytoskeleton and upregulating protein expression of MMP-2.