Hundt Walter, Steinbach Silke, O'Connell-Rodwell Caitlin E, Bednarski Mark D, Guccione Samira
Department of Radiology, Lucas MRS Research Center, Stanford School of Medicine, Stanford, CA 94305, USA.
Ultrasonics. 2009 Mar;49(3):312-8. doi: 10.1016/j.ultras.2008.10.002. Epub 2008 Oct 17.
In this study, we compared the effect of high intensity focused ultrasound (HIFU) and thermal stress on the luciferase activity, controlled by a cytomegaly virus (CMV) promoter in an in vitro model using two tumor cell lines (M21, SCCVII). HIFU was applied in a pulsed-wave mode with increasing voltage at constant pulse duration, or thermal stress was delivered over a range of temperatures (36-52 degrees C) for 5 min. The resulting luciferase activity was measured in live cells using a cooled CCD camera. Luciferase activity was measured at set time intervals over a total of 48 h post-stress. Compared to baseline, the luciferase activity of the M21 tumor cell line when exposed to HIFU was approximately 54.2+/-67.5% (p<0.01) higher at a temperature of 42 degrees C, and approximately 52.9+/-128.5% (p<0.01) higher at 44 degrees C. In the SCCVII tumor cell line, the luciferase activity after HIFU application was 55.4+/-66.6% (p<0.01) higher compared to baseline at a temperature of 42 degrees C. The M21 and SCCVII tumor cell line when exposed to thermal stress alone did not increase the luciferase activity. M21 and SCCVII tumor cells exposed to HIFU showed a maximum decrease in cell viability to 45.3+/-7.5% and 10.3+/-7.5%, respectively, and when exposed to thermal stress to 85.3+/-3.5% and 20.4+/-6.5%, respectively, compared to the untreated control. In M21 and SCCVII cells exposed to HIFU, free radicals could be detected using the dichlorofluorescein dye. Our findings demonstrate that HIFU can enhance the luciferase activity controlled by a CMV promoter. However it also has a higher damaging effect on the cells.
在本研究中，我们在体外模型中使用两种肿瘤细胞系（M21、SCCVII），比较了高强度聚焦超声（HIFU）和热应激对由巨细胞病毒（CMV）启动子控制的荧光素酶活性的影响。HIFU以脉冲波模式施加，在恒定脉冲持续时间下增加电压，或者在一系列温度（36 - 52摄氏度）下进行5分钟的热应激。使用冷却的电荷耦合器件（CCD）相机在活细胞中测量产生的荧光素酶活性。在应激后总共48小时内按设定的时间间隔测量荧光素酶活性。与基线相比，M21肿瘤细胞系在42摄氏度温度下暴露于HIFU时，荧光素酶活性比基线高约54.2±67.5%（p<0.01），在44摄氏度时高约52.9±128.5%（p<0.01）。在SCCVII肿瘤细胞系中，在42摄氏度温度下施加HIFU后，荧光素酶活性比基线高55.4±66.6%（p<0.01）。单独暴露于热应激时，M21和SCCVII肿瘤细胞系的荧光素酶活性未增加。与未处理的对照相比，暴露于HIFU的M21和SCCVII肿瘤细胞的细胞活力分别最大降低至45.3±7.5%和10.3±7.5%，暴露于热应激时分别降低至85.3±3.5%和20.4±6.5%。在暴露于HIFU的M21和SCCVII细胞中，可以使用二氯荧光素染料检测到自由基。我们的研究结果表明，HIFU可以增强由CMV启动子控制的荧光素酶活性。然而，它对细胞也具有更高的损伤作用。
