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Apr 7th, 2011
On-Q-ity presents data on improved cell capture capabilities of its C5 chip at AACR
On-Q-ity presented its dual-capture platform for circulating tumor cells at the annual meeting of the American Association for Cancer Research.
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The microfluidic chip, called the On-Q-ity Circulating Cancer Capture and Characterization Chip, or C5, uses both antibody affinity and size to filter CTCs from normal blood. In a study comparing C5 and a chip using antibody affinity alone, On-Q-ity's dual capture chip "greatly improved" capture rate over the comparator.

In the study, C5 showed between 94 percent and 97 percent efficiency in capturing high epithelial cell adhesion molecule-expressing cancer cells compared to between 51 percent and 55 percent efficiency for the chip with no size gradient, the company said. EpCAMs are proteins associated with many carcinomas.

The Waltham, Mass.-based personalized diagnostics company is hoping that the C5 chip will lead to the identification of biomarkers to improve cancer diagnosis, monitoring, and early detection of recurrence.

"We believe that captured CTCs will serve as a 'bag of biomarkers' that will become the foundation for our molecular diagnostics business by providing greater insight into the mechanisms that drive CTCs, leading to better treatments for cancer patients," Walter Carney, On-Q-ity's chief scientific officer, said in a statement.

Doubling the number of CTCs captured offers more material for the study of disease biomarkers, according to On-Q-ity. Researchers are conducting studies to evaluate C5's utility in late-stage lung cancer, colon cancer, and prostate cancer.

Carney noted that C5 is an improvement over chips that only use affinity for EpCAM-positive cells to capture CTCs, since these methods tend to miss those cells that express the protein at very low levels or don't express EpCAM at all.

"This microfluidic platform allows for affinity and size capture of heterogeneous CTCs on a novel, gradient EpCAM antibody chip," On-Q-ity researchers concluded in the abstract presented at AACR. "The platform can capture spiked cells with good precision. High-efficiency cell capture is demonstrated by combining size and affinity, with almost 100 percent efficiency, regardless of EpCAM expression."

On the company's C5 chip, posts are arranged in a gradient of decreasing diameter and decreasing gap spacing to a minimum of 12 micrometers between posts. The posts are also coated with a monoclonal antibody to capture cells that express EpCAM.

As blood flows over the chip, cells are captured by their EpCAM affinity and by their size. The size gradient allows smaller blood cells to flow through, snagging larger CTCs in the gaps.

To further investigate the improved precision of the dual capture chip, On-Q-ity researchers also tested a control chip with a size gradient, but no antibody affinity. This showed that size alone is largely responsible for the capture of low EpCAM expressing cells, which were captured at 38 percent by the C5 chip.

Heat maps of cell distribution revealed that the small gap regions of the chip were primarily responsible for capturing low EpCAM expressing cells. Cells with high EpCAM also showed a uniform distribution across the C5 chip, suggesting both size and affinity were responsible for the capture of high EpCAM cells.

Other companies are working on CTC technology, including Johnson & Johnson's Veridex, Advanced Cell Diagnostics and Biocept. But On-Q-ity has described its platform as a "rare cell detection system," that will be not only able to capture CTCs, but also circulating stem cells, circulating dendritic cells, or circulating endothelial cells


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