Selectively Killing Cancer Cells Using Ultrasound %

Ultrasound are sound waves with frequencies higher than the upper audible limit of human hearing which are also used to make an image of a person’s internal body structure. Ultrasound waves have been used in cancer treatments before using high-intensity bursts to heat up tissue and killing cancer and normal cells in the area targeted. Researching to create a selective treatment, scientists and engineers are exploring low-intensity pulsed Ultrasound waves to find a way to kill cancer cells without affecting healthy cells.

This research began about 5 years ago when Caltech’s Micheal Ortiz studied the physical differences like size, cell-wall thickness and the size of organelles between healthy and cancer cells and how these properties may be affected when they are bombarded with sound waves. He wondered if it would be possible for the different vibrations of cancer cells to trigger their death. Later in 2016, Ortiz published a study in which he showed that there was a gap in the resonant growth rates of cancerous cells and healthy cells. In theory, this meant that a carefully tuned sound wave could cause the cancerous cells to vibrate to a point that they ruptured, all while leaving the healthy cells in the target area unharmed. Ortiz named this process “oncotripsy”.

A problem identified during this study was that since even within a single tumor, cancer cells are quite heterogeneous, It is almost impossible to find a range of setting for the ultrasound that would kill every single cancer cell. Due to this, the surviving cells would be left out causing the tumor to regrow. This problem could be solved if the body’s immune system could recognize cell death as an injury instead of apoptosis. Apoptosis is when cells in our body grow old and naturally die (over 50 million cells die in our body every day). A healthy immune system can tell the difference between apoptosis and an injury, and so it ignores apoptosis and attacks any invading pathogens during an injury. If the ultrasound could be used in a way that the body’s immune system recognized it as an injury instead of apoptosis, this would lead the site of the tumor to be flooded with white blood cells that could attack the remaining cancer cells and prevent regrowth.

Since the research is still in the development phase, it has not yet been tested on live animals let alone human beings; the experiments so far have been conducted on cancer cells in Petri dishes. Regardless, this research has great potential to find a way to treat different types of cancer without causing healthy cells to die as well.