High-Intensity Ultrasound Used to Fight Cancer

This high-intensity focused ultrasound (HIFU) technology is in use or testing in China, Europe, and the United States to destroy tumors by heating them. But Duke researchers now find that HIFU might work even better if it is first delivered in a way that just shakes the cells. That shaking ruptures tumor cell membranes, causing them to spill their contents. The toxic spill then alerts the immune system to the cancer threat, leading to the generation of tumor-fighting white blood cells.

If the effect seen in mice holds true in human patients, such a treatment could be an important development in many cancer therapies because of its potential to deal with both primary tumors and metastatic tumors that have spread to other organs--all without the need for surgery, the research team reported in the Journal of Translational Medicine on August 3, 2007.

In most cancers, what actually ends up killing the patient is the spread of the cancer from its original site to other parts of the body, said Dr. Pei Zhong, an associate professor in Duke's mechanical engineering and materials science department. If the patient has a tumor in the kidney or liver, several treatment options--including surgery, radiation, or HIFU--can be used to get rid of the cancerous tissues. However, if the cancer cells spread to other vital organs such as the lung or brain, the outcomes are often much worse. HIFU in the current form can only be used to treat the primary tumor. We now think that HIFU delivered in a different mode, with emphasis on using mechanical vibration to break apart the tumor cells, may have an even more significant impact in suppressing cancer metastasis by waking up the immune system.

For reasons that are still not completely understood, cancer cells frequently go largely undetected by the immune system, according to Dr. Zhong. For an anti-tumor immune response to be successful, it may need to recognize not only the surface proteins of cancer cells, but also some of the other proteins locked inside those cells, which Dr. Zhong called danger signals.

In laboratory mice with colon cancer, the researchers discovered that mechanical HIFU delivered to the animals' tumors triggered an immune response twice as strong as did thermal HIFU, most probably by releasing a much more diverse range of danger signals.


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