Ultrasound Can Selectively Kill Cancer Cells

A new technique could offer a targeted approach to fighting cancer: low-intensity pulses of ultrasound have been shown to selectively kill cancer cells while leaving normal cells unharmed.

Ultrasound wavessound waves with frequencies higher than humans can hear—have been used as a cancer treatment before, albeit in a broad-brush approach: high-intensity bursts of ultrasound can heat up tissue, killing cancer and normal cells in a target area. Now, scientists and engineers are exploring the use of low-intensity pulsed ultrasound (LIPUS) in an effort to create a more selective treatment.

A study describing the effectiveness of the new approach in cell models was published in Applied Physics Letters. The researchers behind the work caution that it is still preliminary—it still has not been tested in a live animal let alone in a human, and there remain several key challenges to address—but the results so far are promising.

The research began five years ago when Caltech‘s Michael Ortiz, Frank and Ora Lee Marble Professor of Aeronautics and Mechanical Engineering, found himself pondering whether the physical differences between cancer cells and healthy cells—things like size, cell-wall thickness, and size of the organelles within them—might affect how they vibrate when bombarded with sound waves and how the vibrations might trigger cancer cell death.

I have my moments of inspiration,” Ortiz says wryly.

And so Ortiz built a mathematical model to see how cells would react to different frequencies and pulses of sound waves. Together with then-graduate student Stefanie Heyden (PhD ’14), who is now at ETH Zurich, Ortiz published a paper in 2016 in the Journal of the Mechanics and Physics of Solids showing that there was a gap in the so-called resonant growth rates of cancerous and healthy cells. That gap meant 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 leaving healthy cells unharmed. Ortiz dubbed the process “oncotripsy” from the Greek oncos (for tumor) and tripsy (for breaking).

Source: https://www.caltech.edu/