The study led by researchers at Duke University's Pratt School of Engineering has suggested that a high intensity ultrasound can activate an "alarm" that enlists immune defenses against the cancerous invasion.
The new findings from animal experiments imply that once triggered by the ultrasound, the immune system might even search for and devastate cancer cells, including those that have spread through the bloodstream to lurk in other parts of the body.
This high-intensity focused ultrasound, or HIFU, is in use or testing in China, Europe and the United States to kill tumors 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 breaks tumor 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 tumor-fighting white blood cells.
The researchers suggest that 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 deal with both primary tumors and metastatic cancers that have spread to other organs, all without the need for surgery.
"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. If the patient has a tumor 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," said Pei Zhong, an associate professor in Duke's mechanical engineering and materials science department.
"HIFU in the current form can only be used to treat the primary tumor. We now think that HIFU delivered in a different mode, with emphasis on using mechanical vibration to break apart the tumor cells, may have an even more significant impact in suppressing cancer metastasis by waking up the immune system," he added.
The researchers found in mice with colon cancer that mechanical HIFU delivered to the animals' tumors sparked an immune response twice as strong as did thermal HIFU, most probably by releasing a much more diverse range of danger signals.
"Our results show that while mechanical HIFU is not as effective as thermal HIFU in killing tumor cells directly, it has the potential to induce a stronger anti-tumor immune response. These preliminary findings open up the possibility that we could use heat from HIFU to treat the primary tumor and HIFU-boosted immunotherapy for combating any residual and metastatic tumor cells," Zhong said.
The findings of the study are published in the Journal of Translational Medicine.