Targeted Fluorescent-Imaging Compound Detects Viable Cancer Cells

A fluorescent-imaging compound is turned on only when it is inside a living cell and stops fluorescing when the cell dies or becomes damaged. The compound can be engineered to target specific types of cancer cells.

The new compound enabled scientists 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 into living cells. This method of targeting and activation allowed the scientists to detect specific types of live cancer cells in a mouse model of breast cancer.

Previously developed fluorescent compounds that are activated inside the body's cells have the limitation that once turned on they continue to fluoresce even after they diffuse to new locations. This makes it very difficult to distinguish viable tumor cells from normal tissue, dead, or damaged tumor cells.

The investigation took place at the National Cancer Institute (NCI), part of the US National Institutes of Health (Bethesda, MD, USA) and in Japan. The scientific team that created the imaging compound was led by Hisataka Kobayashi, M.D., Ph.D., from NCI's Center for Cancer Research (CCR), in collaboration with Yasuteru Urano, Ph.D., from the University of Tokyo (Japan).

"These [fluorescing-imaging] 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," said Dr. Kobayashi. He added, "Our design concept is very versatile and can be used to detect many types of cancer. 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."

The new compound was described online in Nature Medicine on December 7, 2008.

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US National Institutes of Health
University of Tokyo