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Tumors that Glow in the Dark

The gene that enables fireflies to flash, as part of the insects' nocturnal courtship displays, is also allowing researchers to track the effectiveness of anti-cancer drugs as they move through the body.

Researchers are using a technique, called bioluminescence imaging, to observe changes in the size of tumors after the cells are injected with the insect gene, luciferace.

The discovery, by a team of researchers led by Ralph Mason at the University of Texas Southwestern Medical Center, was published in a study online in the Journal of the Federation of American Societies for Experimental Biology.

Cancer cells were grafted into laboratory mice, which were then inoculated with the chemical luciferin, which is oxidized by an enzyme to produce oxyluciferin and light. Although the glowing tumor cells which result are too dim to be seen by the human eye, the researchers used a highly sensitive astronomy camera, like those that zoom in on radiation from distant stars, to detect the light.

When the mice were injected with a new cancer drug, the glow vanished. The drug, called combretastin A4, is a synthetic version of a compound extracted from the African bush willow tree, and blocks the formation of new blood vessels supplying the tumor. It's a highly promising treatment. Mason's method allows the size of the tumor to be accurately measured, enabling researchers to pinpoint the optimal dose to give to humans - hopefully destroying cancer cells while limiting any side effects.

"What we've done is offer proof-of-concept that (bioluminescence imaging) may be an effective and cheaper method to assess drug development and effectiveness," Mason said. "The technique is not intended to be used for imaging tumors or diagnosing cancer in humans, but it potentially allows us to do much more efficient pre-clinical experiments."