A sprayed substance that turns fluorescent green when it hits cancer cells could revolutionize the way surgeons remove tumors.
Researchers tested the spray on ovarian tumors in mice, and it lit up the cells of all tumors that contained a specific molecule. Around 70 percent of human ovarian tumors have that marker.
"The probe doesn't have any color before it's sprayed onto a tumor," said Hisataka Kobayashi of the National Cancer Institute, lead researcher on the new work. "But once it's activated by cancer cells, it lights up and we can see it."
The spray could show surgeons in the middle of an operation whether they've gotten out all the cancerous cells when they remove a tumor.
The findings were published today (Nov. 23) in the journal Science Translational Medicine.
Tool for surgeons
The cancer molecule that the spray detects is called GGT, for gamma-glutamyltranspeptidase. GGT is found in ovarian cancers as well as a fraction of other tumors, including some colon, gastric and liver cancers.
Kobayashi and his colleagues knew that GGT makes a cut in a certain protein. So the scientists engineered a fluorescent probe that lit up only when it was cut. They then formulated the probe into a spray.
When the spray lands on a tumor cell that has GGT molecules on its surface, it lights up within 10 to 20 seconds, Kobayashi said. Even if there are only a few sparse molecules of GGT, the spray will fluoresce within two minutes.
The team tested the spray on mice with ovarian tumors. The researchers genetically engineered the mouse tumors to fluoresce red, then used the spray, which turns green. The red and green regions overlapped, showing the effectiveness of the spray.
Kobayashi noted that other methods of looking for cancer cells in people rely on formulations administered ahead of time — the night before a surgery or procedure, for example. The spray would be faster and easier.
"I think this is a very practical approach," he said. "If you need to inject an agent ahead of time, or a night before, it's less practical to use. But with this one, a surgeon can use it anytime they want" to see where the edges of the tumor lie.
Study in humans needed
"I thought this was great work," said Dr. Michael Bouvet, a surgeon at the University of California, San Diego Cancer Center. "Something that allows surgeons to just spray it onto the tumor, and get a quick readout of what's cancer and what's not, is very appealing."
However, Bouvet noted that the spray would be useful only for tumors known to express GGT. And more work is needed to test the safety and effectiveness of the spray in humans.
Researcher Robert Hoffman of UCSD is looking forward to the day it can be used on ovarian cancer patients.
"Ovarian cancer is a horrendous disease and it has a tendency to spread all over the ovarian cavity," Hoffman said. "If we're able to see it, as opposed to not see it, that's a big advantage."
The scientists said the spray could be applied directly into the body during a surgery, to make sure there are no cancer cells remaining. Additionally, the spray could be applied to a tumor that has been removed, to illustrate whether the margins — the borders around the tumor — are truly cancer-free.
Other approaches to detecting tumors are in the development pipeline, Bouvet and Hoffman said. One involves a fluorescent molecule that lights up in the presence of telomerase — a protein that's more universal across cancer types. However, not all the probes act as quickly as the GGT spray.
Pass it on: A new spray that lights up cancer cells might help surgeons detect whether they've removed all of a tumor.
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