Objective: To investigate the killing effect of high intensity focused ultrasound (HIFU) on human tumor cells and study the mechanism of its action.
Methods: Human breast cancer cells MCF-7 were treated with different intensity of HIFU in vitro and incubated. The killing effect and proliferation inhibition effect of HIFU on tumor cells were investigated with the methods of trypan blue exclusion assay, MTT assay and colony formation assay. And the cell cycle, apoptotic cells and the expressions of P53, BCL-2, FAS and HSP70 were measured with flow cytometry.
Results: After HIFU treatment, the death rates of cancer cell increased, the proliferation of cell waned (P < 0.05), the number of colony formation decreased (P < 0.001), the cell number increased in G0/G1 phase (P < 0.05) and decreased in S phase, the apoptotic indices increased (P < 0.01), the expression of HSP70 was enhanced, and no significant changes of P53, BCL-2, FAS expressions were found (P > 0.05).
Conclusion: HIFU produces significant effects such as killing, proliferation inhibition and colony formation inhibition on human breast cancer cells; its mechanism of action may be associated with the inhibition of DNA synthesis. In addition, HIFU treatment can induce apoptotic cell death, which may not be associated with the mediation and regulation of P53, BCL-2 and FAS genes.