Weihong Tan and his research group at the University of Florida have found DNA strands that cling to cancer cells. Doctors could use the adhesive molecules, which are known as aptamers, to check their patients for the deadly disease.

The new test could be a godsend for people with liver cancer, which often surfaces after it is too late for surgery.

It might work like this: A physician could take some blood or tissue from their patient and send it off to a lab. Technicians would mix it with aptamers that are attached to a fluorescent dye. If any of the cells happen to be cancerous, the luminous molecules will stick to them. Under a fluorescence microscope or in a cell-counting machine called a flow cytometer, each one will be lit up like a Christmas tree.

In a more sophisticated world, clinicians could coat nanoparticles with the aptamers and inject them directly into their patients. The tiny objects would drift around randomly unless they encountered tumor tissue. In that case, they would all cluster in the same place and show up as a big bright spot on a whole-body scan.

More important than the chemicals themselves are the methods used to discover them. Tan and his colleagues developed a procedure called cell-SELEX, which is essentially a molecular elimination tournament.

In the Feb. 1 issue of Analytical Chemistry, he told the story of his latest project.

His team started out by bathing liver cancer cells in roughly a billion billion different DNA strands. By chance, some of the strands were able to stick. Those that could not were discarded.

Next, the molecules that could adhere to the cancer cell were mixed with healthy cells. If they also stuck to the healthy cells, they were punted. Only those that survived both challenges would go on to be copied by a PCR machine.

Competing in a game of SELEX is not easy. The pool of successful DNA was forced to face the same pair of obstacles fifteen more times.

In the end, when only a few molecules remained, the scientists read their sequences. Then, they tested some of the winners individually. All of them could firmly hold onto malignant liver cells.

Without a doubt, the same procedure could be used to identify DNA that can bind to other types of cancer cells. Some of them may be used in revolutionary medical tests.

The Team: Shangguan Dihua is a professor, Ling Meng is a graduate student, Zehui Charles Cao is a postdoc, Zeyu Xiao is a visiting student from Chinese Academy of Sciences, Xiaohong Fang is the advisor of the visiting student from Chinese Academy of Sciences, Ying Yi is an assistant clinical professor of Pathology, Diana Cardona is a resident at UF, Rafal Witek is a postdoctoc, Chen Liu is an associate professor of Pathology