Inner workings: Spraying to see cancer cells.

In a Stanford University operating room, surgeons peer into the abdomen of a patient, scalpels delicately dancing under the bright lights. They’re removing a gastric tumor, hoping they can cut away every cancerous cell. Just outside the operating room, an unlikely group waits to lend a hand: they’re not medical doctors, but chemists, and they hope to improve the success rate of cancer surgeries. In the group is Livia Eberlin. As a graduate student at Purdue University, Eberlin worked in an analytical chemistry laboratory perfecting a new imaging technique. Scientists using the approach spray a liquid at any material they want to study, and then analyze the droplets that bounce off its surface. By measuring chemicals contained within the droplets, the scientists can elucidate the makeup of the material in question. The method, called desorption electrospray ionization mass spectrometric imaging, or DESI-MSI, was seen as useful for forensics; researchers could use it to detect drug residue on a dollar bill or determine the composition of a pill. However, Eberlin had another use in mind for the technique. “In hospitals, surgeons and pathologists need a way to analyze tissue very quickly,” she says. “The patient is open and the surgeon is waiting at the operating table to get results.” In operations to remove a tumor, Eberlin explains, surgeons must know whether they’ve removed all of the cancerous cells. So they give samples of removed tissue to a pathologist to examine. If the surgeon has collected not only cancer cells, but a margin of healthy cells surrounding the cancer, then the tumor is likely contained. If not, the surgeon needs to continue operating. Using standard methods, pathologists must go through a number of steps to analyze such a tissue. “But DESI-MSI takes less than a second and can be done in open air, with no sample preparation,” Eberlin says. “It seemed very appropriate for this setting.” Eberlin began testing whether DESI-MSI could detect the difference between healthy and cancerous cells. She showed, in 2013, that it worked in brain cancers (1); the spray picked up small molecules that varied between healthy and diseased tissue. When Eberlin graduated, she moved to Stanford and teamed up with chemist Richard Zare, pathologists, and surgeons to start testing the approach in gastric cancers. Recently, they’ve reported that the technique is a success in speeding up the detection of these tumor cells as well (2). “There’s a lot of enthusiasm among the clinicians about this,” Zare says. As the surgeon finishes removing a tumor, he or she passes samples along to Eberlin and Zare’s group. Down the hallway, the scientists spray the samples under the mass spectrometry machine and can quickly obtain data on which parts of the tissue are cancerous. “This just showcases how powerful a simple technique can be,” Eberlin says. “The richness of information we can get from just spraying a tissue still blows my mind.”