Capturing CTCs


Circulating Tumor Cells or CTCs, have been recognized by scientists as potentially beneficial metrics for tracking a patient’s disease for some time, but these cells are difficult to find, because they are drowned out by billions of ordinary red blood cells and other cells found in the blood. With current technologies only recognizing a handful of cells from certain patients, developing ways to specifically concentrate and trap CTCs has been technically challenging,

However, in the new research conducted by University of Wisconsin-Madison Professor of Pharmacy, Seungpyo Hong and his collaborators, they have spent years of work in isolating these circulating tumor cells, or CTCs, by demonstrating better methods for their capture on clinical samples for the first time. Researchers were able to identify large numbers of the cells in cancer patients undergoing radiation therapy by forcing cancer cells to slow down and develop stronger molecular traps specific to CTCs.

The CTC count drastically decreased during the therapy then bounced back  in the patients that ended up requiring additional treatment — signifying that the technology could supplement other techniques for tracking the progress of treatment.

The study was published last March 15 in the journal Clinical Cancer Research. Collaborators from the University of Illinois in Chicago, Duke University and Yonsei University in South Korea also contributed to the work, which was funded in part by the National Institutes of Health and the National Science Foundation.

Hong and his collaborator Andrew Wang of the University of North Carolina School of Medicine created a company named Capio Biosciences in 2015 to commercialize a new technology they call CapioCyte.

They were inspired by the behavior of CTCs in the blood, which attach themselves to blood vessel walls and begin tumbling along looking for suitable places to invade. This separates them from the cells carrying oxygen  and is replicated by CapioCyte technology using an array of sticky proteins that force the CTCs to roll, which slows them down.

The cells are then trapped by a series of antibodies, more specifically proteins that  bind and hold onto the CTCs. The researchers developed a nanoscale structure shaped a little like a tree, with each branch tipped with an antibody, to make the connection sturdier. When a cancer cell passes by, a lot of individual branches can latch on it, increasing the strength of the attachment.

Though the cell count did not correlate with the stage, and thus severity, of the cancer, the reduction in cells was correlated with positive radiation therapy. CTC numbers came back up in two out of three patients that had repeated or persistent disease.

“Our data suggest that we have a good chance of making CTCs a predictive biomarker or biomarker for surveillance for at least a few cancers, and that’s always exciting,” says Wang.