Science News for Students - Spring 2021

Targeting cancer with ultrasound therapies

High-intensity ultrasound (left, depicted as red) kills all cells. In con- trast, low-intensity ultrasound (depicted as blue), targets only cancer cells (depicted in red), leaving healthy ones (green) intact.

High Intensity Ultrasound Therapy

Targeted Pulsed Ultrasound Therapy

Cancer cell

Healthy cell

All cells destroyed

Cancer cells destroyed/ Healthy cells spared

the end, bubbles in the standing wave oscil- late more than do those in a normal wave. And that extra oscillation proved essential to killing cancer cells. The team suspects the standing wave brings microbubbles closer together. That then boosts the ultrasound energy deposited on the cells, Mittelstein says. Not all cells respond equally to this standing wave. Which do will depend on their physical properties. Here, only cancer cells were harmed. In his experiment, Mittelstein used a reflector to bounce the sound waves back into the sus- pension to create that standing wave. Bouncing ultrasound against bone might provide the same type of boosted impact, he suspects. The team published its findings January 7, 2020 in Applied Physics Letters . This study is exciting, says TimothyMeakem.

He was not involved with the study. He does, how- ever, know about ultrasound’s value in medicine. He works at Focused Ultrasound Foundation in Charlottesville, Va., as its chief medical officer. If the effect seen in these cells also occurs in people, he says, it would let doctors target cancer cells in ways not currently possible. However, he cautions, this technique is not ready for use in patients. This is just the first step in the process of developing a new treatment. But if the next stages go well, it “might be a huge benefit to patients.” Mittelstein is already moving ahead. His team’s next experiments will go beyond targeting cells in a liquid. Theywill focus on mounds of cells, which model a cancerous tumor. If they get similar cell killing in treated tumors, he says, “we think this therapy could make a significant impact in cancer therapy.” ×

DAVID MITTELSTEIN/CALTECH

22 SCIENCE NEWS FOR STUDENTS | Invention & Innovation