The gene responsible for getting fireflies to "glow" is being used by University of Texas Southwestern researchers to track blood flow to cancerous tumors, testing the effectiveness of cancer drugs whose main job is cutting off that blood supply.

According to a report from the Dallas-based team, a technique called "Bioluminescence imaging" or BLI requires a substrate called luciferin be added to the bloodstream, which is then carried to cells throughout the body. When luciferin reaches cells that have been altered to carry the firefly gene, those cells emit light and the amount of that "light" helps monitor the drug's success.

Some cancer drugs work by cutting off the blood supply to tumor cells. given that luciferin is delivered via the vasculature, the researchers set out to determine the kinetics of luciferin delivery and whether BLI techniques could be used to gauge the effectiveness of drugs that destroy blood vessels that feed tumors.
They tested their theory in mice bearing human breast-cancer tumors. The tumor cells, before being introduced to the mice, were transinfected with the firefly gene, which became part of the cells as they divide and grow--much like a genetically-modified food crop.

While the mice themselves didn't visibly glow, the researchers used special light-detection equipment to observe strong correlations between the amount of light emitted and the size of the tumor as it grew. Detected light emission, however, was severely reduced after the vascular-disrupting drug was administered.

"What we've done is offer proof-of-concept that BLI may be an effective and cheaper method to assess drug development and effectiveness," says Dr. Ralph Mason, professor of radiology and director of UT Southwestern Cancer Imaging Center and senior author of the study which was supported by the Department of Defense and the National Cancer Institute.

Dr, Mason stressed that light-emission kinetics depend heavily on tumor location.

"The technique is not intended to be used for imaging tumors or diagnosing cancer in humans," he adds. "But it potentially allows us to do much more efficient pre-clinical experiments."

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