University of Michigan researchers study how sound waves trigger immune responses to cancer in mice: 'The body can see them and attack them'

University of Michigan (U-M) researchers are pursuing a technique that could potentially revolutionize cancer treatment.

According to a press release from the University of Michigan, researchers have discovered that a noninvasive sound wave technique called histotripsy can activate an immune response in mice by breaking down cancer cell walls to expose cancer cell markers previously hidden from the body's defenses. 

This development offers medical professionals two approaches to attacking cancer by physically destroying tumors through sound waves while triggering the body's immune response. The treatment wouldn't have the harmful side effects associated with radiation and chemotherapy.

“We found that histotripsy somehow not only kills cancer cells but causes them to undergo a unique pathway of cell death that draws the attention of the immune system,” said Clifford Cho, the C. Gardner Child Professor of Surgery and vice chair of surgery, according to the press release. 

In cancer cells, the tumor antigens are hidden behind the cell walls. During chemotherapy or radiation, these antigens are destroyed along with cancer cells. By contrast, sound waves kill cancer cells by breaking their cell walls, releasing tumor antigens that trigger the body's defense system.

Zhen Xu, U-M professor of biomedical engineering and an inventor of the histotripsy approach, said that with this technique, the antigens are not destroyed but are released while killing the tumor cells. 

“Once they’re no longer hidden, the body can see them and attack them,” Xu said, according to the press release.

The team discovered the technique by treating a mouse with histotripsy and then injecting leftover material from broken-down tumors from that mouse into another which also developed immune protection from that cancer.

"Injecting the debris into a second mouse had almost a vaccine-like property," Xu said. "Mice that received this debris were surprisingly resistant to the growth of cancers."

Histotripsy could also offer an advantage in cancer treatment, as the immune response occurred throughout the body, not just in the area where the treatment was applied. With the promising results on histotripsy treatment of brain cancer therapy and immunotherapy, the researchers are hoping that this noninvasive technique will be applied to human cancer treatment soon.