An intense form of ultrasound that shakes a tumour until its cells start to leak can trigger an “alarm” that enlists immune defences against the cancerous invasion, according to a study led by researchers at US’ Duke University’s Pratt School of Engineering. The new findings from animal experiments suggest that once activated by the ultrasound, the immune system might even seek and destroy cancer cells, including those that have spread through the bloodstream to lurk in other parts of the body.
--- Picture: Pei Zhong, a professor at Duke’s mechanical engineering and materials science department, poses besides an ultrasound machine. Zhong along with his team have found that doctors could possibly use High-Intensity Ultrasound to launch an attack on cancer, wherever it lurks ---
Creating a Toxic Spill
High-intensity focused ultrasound, or HIFU, is in use or testing in China, Europe and the United States to kill tumours by heating them. But Duke researchers now find that HIFU might work even better if it is first delivered in a manner that just shakes the cells. That shaking ruptures tumour cell membranes, causing them to spill their contents. The toxic spill then alerts the immune system to the cancer threat, leading to the production of tumour-fighting white blood cells.
If the effect seen in mice holds true in human patients, such a treatment could be an important advance in many cancer therapies because of its potential to tackle both primary tumours and metastatic cancers that have spread to other organs – all without the need for surgery, the research team reported in the Journal of Translational Medicine on August 3. The work, done by the engineers in collaboration with cancer immunologists and physicians at the Duke Comprehensive Cancer Centre, was supported by US’ National Institutes of Health.
“In most cancers, what actually ends up killing the patient is the spread of the cancer from its original site to other parts of the body,” said Pei Zhong, an associate professor in Duke’s mechanical engineering and materials science epartment. “If the patient has a tumour in the kidney or liver, several treatment options - Including surgery, radiation or HIFU – can be used to get rid of the cancerous tissues. However, if the cancer cells spread to other vital organs such as the lung or brain, the outcomes are often much worse.
“HIFU in the current form can only be used to treat the primary tumour,” he continued. “We now think that HIFU delivered in a different mode, with emphasis on using mechanical vibration to break apart the tumour cells, may have an even more significant impact in suppressing cancer metastasis by waking up the immune system.”
Road blocks ahead
For reasons that are still not completely understood, cancer cells often go largely undetected by the immune system, Zhong said. For an anti-tumour immune response to be effective, it may need to recognise not only the surface proteins of cancer cells, but some of the other proteins locked inside those cells, which Zhong called “danger signals.”
Preliminary tests show potential
The researchers found in mice with colon cancer that mechanical HIFU delivered to the animals’ tumours sparked an immune response twice as strong as did thermal HIFU, presumably by releasing a much more diverse range of danger signals.“Our results show that mechanical HIFU has the potential to induce a stronger anti-tumour immune response,” Zhong said. “These preliminary findings open up the possibility that we could use heat from HIFU to treat the primary tumour and HIFU-boosted immunotherapy for combating any residual and metastatic tumour cells.”