Caltech Ultrasound Technique Can Selectively Kill Cancer Cells

Researchers at Caltech have devised a new approach to fight cancer using ultrasound. The technique uses low-intensity pulses of ultrasound and has been shown to selectively kill cancer cells while leaving normal cells unharmed. The scientists say that high-intensity bursts of ultrasound can heat tissue, killing cancer cells and normal cells in the target area.The new research uses low-intensity pulsed ultrasound (LIPUS) in an effort to create a more selective treatment. While the work is still preliminary and hasn't been tested in live animals or humans, the results are promising. Scientist Michael Ortiz says that he wondered if things like size, cell-wall thickness, and size of the organelles inside the cells might affect how they vibrate when bombarded with sound waves and how the vibrations might trigger cancer cell death.

He began to build a mathematical model to see how different cells would react to different frequencies and pulses of sound waves. The team found that there was a gap in the resonant growth rates of cancerous and healthy cells. That means that a carefully tuned sound wave could in theory cause the cell membranes of cancerous cells to vibrate to the point that they ruptured while healthy cells were unharmed.

Two of the ultrasound instruments have been built so far with one at the Caltech-City of Hope Biomedical Research Initiative. The team is drawing samples from humans and mice to include colon and breast cancer. They have also tested a variety of healthy cells, including immune cells, to see how the treatment affects them.

One scientist notes that cancer cells are quite heterogeneous, even within a single tumor. Because of that it will be almost impossible to find a range of settings for the ultrasound that could kill every single cancer cell. The team also thinks that there is a chance to tune the treatment to cause cancer cell death in a way that the immune system might think the cell death is an injury rather than natural death and send white blood cells to attack the other cancer cells.