Now Kashani-Sabet, Mehdi Nostrati and their colleagues have developed a molecular test that can highlight differences between malignant melanomas and harmless moles under the microscope.
The University of California has patented the test, and Kashani-Sabet has already started up a biotech company to work on commercializing it. He hopes it will be in widespread use in a year or two.
It's based on their previous finding that used DNA microarrays to analyze the levels of activity of more than 40,000 different genes in various stages of melanoma, as well as in benign noles. That work revealed "about a thousand genes that… the levels were different in these genes in moles versus melanomas," Kashani-Sabet explains.
In their new study,published in the Proceedings of the National Academy of Sciences, "We picked five of these genes that would be at higher levels in melanomas than in the moles. And by looking at these five genes and combining their levels together, we were able to develop a test to be able to distinguich between a mole and a melanoma," Kashani-Sabet says.
To develop the test, they used a technique called antibody staining to highlight the proteins encoded by those genes in biopsy samples, allowing them to visualize the amounts of the proteins under the microscope. They also used a computer program that can score the amounts of staining in each sample.
"We looked at these five proteins initially in 500 moles and melanomas and found that these markers, the proteins, were accurate in diagnosing these cases in about 92 percent of the time," says Kashani-Sabet.
It turned out that in addition to the amounts of these proteins, the team also found a difference in their locations.
"We found that the levels of these proteins were clearly higher in melanomas than in moles, and that's what we expected from our earlier study," Kashani-Sabet says. "But what was unexpected was that it wasn't just how high the proteins were, but the pattern of expression was very different between moles and melanomas."And what we found was that, for melanomas, these proteins expressed them in a very uniform way from the top of the cancer to the bottom of the cancer."
Whereas for the mole, the proteins were present at the top, but they were usually lost or absent down at the bottom. So this different pattern of expression wound up being able to help us discriminate between the benign mole and the cancer," he says.