'Painting' Cancer Cells in Living Animals

The probe's main ingredient is a molecule that labels active proteases - protein-destroying enzymes - that run amok in cancerous cells. The molecule is normally invisible to the naked eye but it carries a fluorescent tag that lights up when it binds to the protease. The tag beams out near-infrared light that passes through skin and is detectable with a special camera.

"We think these probes may ultimately provide a less harmful, noninvasive method of detecting cancer," said Galia Blum, PhD, a postdoctoral scholar in the laboratory of Matthew Bogyo, PhD, assistant professor of pathology Stanford University Medical Center.

A key advantage of this enzyme-targeting molecule is its size. About 100 times smaller than other molecular imaging reporters, it can easily slip across the cell membrane and enter living cells. It can also move through the animal quickly, which opens up the possibility of using the technique to light up tumors while surgery is in progress.

"Unlike other enzyme-targeting molecules, it's very specific, sticks to where it binds and does it all very rapidly - in 30 minutes or less," Bogyo said.

And unlike most other molecular probes, this type identifies only active enzymes. "We went one step beyond just telling if the enzymes are there. We can answer the question, 'Are they active"' That's important because an accumulation of inactive enzymes doesn't necessarily indicate disease," Blum said.

The researchers designed the probe to bind to a subset of a family of proteases called cysteine cathepsins, which are more active in several types of cancer as well as other diseases.

COMPAMED.de; Source: Stanford University Medical Center