The mini-pyrotechnics of fireflies could prove to be lightning in a bottle for drug researchers, providing a way to speed up the long and arduous process of developing and testing new drugs.

Washington University (St. Louis) radiologist David Piwnica-Worms and his team are using a firefly protein to make mouse cells glow when triggered by a drug. When they sedate the mice and put them under a special camera, they can see changes in the glow in real time. In the experiment they put the glowing protein into tumor cells treated by an experimental cancer drug.

"You're actually looking at how much of the drug got in and affected the target protein, because that protein is now fused to the glowing firefly protein," he says. "By following the light coming out, you can very sensitively follow, over time, different doses of the drug and know how long it takes and how much it takes to get into the tumor. So you have a much more precise tool for understanding the molecular targeting of the drug."

As he and his team reported in the journal Nature Methods, the new technique could make tests of many kinds of new drugs faster and more efficient. And the technique does not harm test subjects.

"You can just image the animals over and over and over again for hours and hours and days on end... at any type of time interval that you want," he says.

Piwnica-Worms' study on the cancer drug took five days and required only 30 mice. He says it normally might have taken six months and 300 mice.

"A traditional way of studying that would be to [give] the animal with a certain amount of the drug and then wait a number of days or weeks and see how the tumor grew," he says, "but you still never knew if the drug was acting on the tumor in the way you'd designed it to. The end result — the tumor stopped growing — is helpful; but you'd still have to wait days and weeks to find that out ... and of course you have to destroy the cells or the animal in order to study these particular proteins."

The researchers recently published a similar paper in the journal Analytical Chemistry, but with proteins from click beetles, which glow red and green. Combined with the yellow of fireflies, these extra colors give them the option of watching a drug's effect on several different areas at one time.