For some time, researchers have recognized the potential utility of tracking circulating tumor cells (CTCs) for the study of metastasis. However, how to best identify these cells amongst the millions of healthy cells circulating in the blood has posed a problem. Now, researchers at the University of Wisconsin-Madison and the University of North Carolina School of Medicine have demonstrated a method for identifying large numbers of the cells in cancer patients undergoing radiation therapy.
When CTCs circulate in the blood, they attach themselves to blood vessel walls and tumble along until they find an appropriate place to invade. The technology described in the paper capitalizes on this aberrant behavior using an array of sticky proteins that force the CTCs to begin rolling, thus slowing them down.
These cells are then trapped using a series of three cancer-specific antibodies that bind the CTCs, holding onto them. The researchers also developed a nanoscale structure, shaped like a tree, with antibody-tipped ‘branches’. When a cancer cell passes nearby, the branches latch on and increase the attachment strength.
The researchers were able to capture an average of 200 CTCs from each milliliter of a patient’s blood. While the team was not able to draw a correlation between number of CTCs and stage of the cancer, they were able to use it to determine the success of radiation therapy. During therapy, the number of CTCs dropped and subsequently rebounded in patients that ended up requiring additional treatment. These findings suggest that the technology could be used as a resource to monitor treatment success.
The research team has patented this technology, which they call CapioCyte, and started the company Capio Biosciences in 2015 to commercialize it. Their findings for this study were published online today in the journal Clinical Cancer Research.
Image: This is an illustration of the CTC capture process where cancer cells (in orange) and white blood cells (in white) both begin rolling along sticky proteins mimicking blood vessel walls. Only cancer cells are held firmly in place by CTC-specific antibodies, while normal white blood cells are allowed to keep moving. Image courtesy of Michael Poellmann.