A glass plate with a nanoscale roughness could be a simple way for scientists to capture and study the circulating tumor cells that carry cancer around the body through the bloodstream.
Engineering and medical researchers at the University of Michigan have devised such a set-up, which they say takes advantage of cancer cells' stronger drive to settle and bind compared with normal blood cells.
Circulating tumor cells are believed to contribute to cancer metastasis, the grim process of the disease spreading from its original site to distant tissues. Blood tests that count these cells can help doctors predict how long a patient with widespread cancer will live.
As important as the castaway cells are, scientists don't know a lot about them. They're rare, at about one per billion blood cells. And they are not all identical, even if they come from the same tumor. Existing tools for isolating them only catch certain types of cells-those that express specific surface proteins or are larger than normal blood cells.
For example, the commonly used, FDA-approved CellSearch system uses antibody- coated magnetic beads to seek out tumor cells and bind to them. But not all circulating tumor cells express the proteins these antibodies recognize. It is possible that the most dangerous ones, known as cancer stem or progenitor cells, may have shed that tell-tale coat, thereby evading approaches that rely on antibodies.
The researchers say their system could likely trap these stealth cancer stem cells-a feat no research team has accomplished yet.
"Our system can capture the majority of circulating tumor cells regardless of their surface proteins or their physical sizes, and this could include cancer progenitor or initiating cells," said Jianping Fu, assistant professor of mechanical engineering and biomedical engineering and a senior author of a paper on the technique published online in ACS Nano.
Fu and his engineering colleagues teamed up with U-M senior cancer researcher and breast cancer clinician Dr. Sofia Merajver and her team. This multidisciplinary group believes that while the device could one day improve cancer diagnosis and prognosis, its first uses would be for researchers to isolate live circulating tumor cells from blood specimens and study their biological and physical properties.
"Understanding the physical behavior and nature of these circulating tumor cells will certainly help us understand better one of the most difficult questions in cancer biology-the metastatic cascade, that is, how the disease spreads," Fu said. "Our system could provide an efficient and powerful way to capture the live circulating tumor cells and use them as a surrogate to study the metastatic process."
But capturing them, as challenging as it has proven to be, is only the beginning, said Merajver, who has spent the last 18 years studying cell signaling and the physical properties of highly aggressive cancer cells.