New Targeted Fluorescent-Imaging Compound Allows Researchers to Detect Viable Cancer Cells in Mice
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Researchers have developed a new type of imaging compound that allows them to visualize viable breast cancer cells that have spread to the lungs in mice.
The compound binds to a protein called HER2, which is found on the surface of some breast cancer cells, and it glows, or fluoresces, only when taken inside living cells. This method of targeting and activation allowed researchers to detect specific types of live cancer cells in a mouse model of breast cancer.
The study, by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, and in Japan, appeared online Dec. 7, 2008, in Nature Medicine.
Previously developed fluorescent compounds that are activated inside the body's cells have the limitation that, once they are turned on, they continue to fluoresce even after they diffuse to new locations, making it difficult to distinguish viable tumor cells from normal tissue or dead or damaged tumor cells.
The research team, led by Hisataka Kobayashi, M.D., Ph.D., at the Molecular Imaging Program of NCI's Center for Cancer Research (CCR), in collaboration with Yasuteru Urano, Ph.D., at the University of Tokyo, created an imaging compound that is turned on only when it is inside a living cell and stops fluorescing when it leaves the cell, as would happen when the cell dies or becomes damaged. The compound also can be engineered to target specific types of cancer cells.
"Imaging compounds designed by our concept may have applications in the clinic," said Kobayashi. "These compounds may allow clinicians to monitor a patient's response to cancer therapy by allowing them to visualize whether a drug hits its target and whether hitting the target leads to shrinkage of the tumor. With additional research and extensive testing in humans, these compounds may also be adapted for use in endoscopy procedures and for use as a surgical aid to improve removal of tumors."
"Our design concept is very versatile and can be used to detect many types of cancer," said Kobayashi. "Unlike other activatable fluorescent compounds, our compound consists of a targeting agent and a fluorescing agent that act independently. We can target the fluorescing agent to different types of cancer cells by using any antibody or molecule that is internalized by the targeted cells after it binds to the cell's surface proteins."
