The FASEB Journal express article 10.1096/fj.04-1601fje. Published online July 1, 2004.
Apoptosis signals in lymphoblasts induced by focused ultrasound Amir Abdollahi,* Sophie Domhan,* Juergen W. Jenne,* Mazin Hallaj,‡ Giorgio Dell` Aqua,* Martina Mueckenthaler,† Alexandra Richter,† Heather Martin,‡ Juergen Debus,* Wilhelm Ansorge,† Kullervo Hynynen,‡ and Peter E. Huber* *Department of Radiation Oncology, German Cancer Research Center (DKFZ), D-69120 Heidelberg; †European Molecular Biology Laboratory (EMBL), D-69117 Heidelberg, Germany; and ‡Department of Radiology, Brigham and Womens’ Hospital, Harvard Medical School, Boston, Massachusetts 02115 Corresponding author: Peter E. Huber, M.D., Ph.D., German Cancer Research Center/Deutsches Krebsforschungszentrum (DKFZ), Department of Radiation Oncology, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany. E-mail:
[email protected] ABSTRACT We investigated the effects of focused ultrasound (FUS) on specific molecular signaling and cellular response in three closely related human Tk6 lymphoblast cell lines that differed only in their p53 status. The applied ultrasound parameters fell between the physical dose range, which is safely used in medical diagnostics (peak pressure10 MPa). Based on cDNA microarrays and protein analysis, we found that FUS at the intermediate peak pressure of 1.5 MPa induced a complex signaling cascade with upregulation of proapoptotic genes [e.g., p53, p21, Thy1 (CD 90)]. Simultaneously, FUS downregulated cellular survival components (e.g., bcl-2, SOD). The p53 status was important for the reaction of the cells to ultrasound. Apoptosis and G1 arrest were induced primarily in p53+ cells, while p53- cells showed less apoptosis but exhibited G2 arrest. Likewise, the proliferation of lymphoblasts was much more strongly inhibited in p53+ than in p53- cells. Microarray analysis further demonstrated an upregulation of genes involved in oxidative stress (e.g., ferritin), suggesting that indirect sonochemical effects via reactive oxygen species play a causative role in the interaction of ultrasound with lymphoblasts. An important characteristic of FUS in therapeutic ultrasound applications is its ability to be administered to the human body in a targeted manner while sparing intermediate tissues. Therefore, our data indicate that this noninvasive, mechanical wave transmission, which is free of ionizing radiation, has the potential to specifically induce localized cell signals and apoptosis. Key words: FUS ● p53 ● bcl-2
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nowledge of the details of molecular signaling in response to mechanical pressure or pressure waves such as ultrasound is limited (1). We were interested in shedding some light on the complex biological events and signaling cascades initiated by structural and mechanical stimuli subsequent to the application of ultrasound waves. Today, ultrasound primarily serves as a safe diagnostic tool without any apparent adverse effects in nearly all fields
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of medicine. However, ultrasound can be focused through the intact skin and be delivered precisely to a given volume consisting of a few millimeters cubed. When focused in this manner, local energy densities can be achieved that are higher by a factor of 104 when compared with ultrasound diagnostics (kW/cm2, peak pressure p>10 MPa vs. 0.1 W/cm2, peak pressure
