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 mechanism in 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/cm² group. 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 fluorescence staining. The expressions of MMP-2 and MMP-9 were examined by real-time fluorescent 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 fluorescence 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.

Key words: Low intensity ultrasound, Liver cancer cell, Migration, Matrix metalloproteinase