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A device that shines a laser on the blood vessels (here, in a mouse) can detect circulating rare tumor cells.
Ekaterina Galanzha / University of Arkansas for Medical Sciences
By Jocelyn Kaiser
Tumors release cells in the blood that can reveal that the cancer is developing and spreading to other parts of the body. Researchers have now shown that they can train a laser device on the hand of a patient with skin cancer and detect those rare tumor cells circulating in the blood. The device could one day improve the screening for cancer melanoma. It could also help doctors monitor the proper functioning of treatments and even slow down the spread of the original tumor by zapping the wandering cells.
"It is fascinating to be able to detect these circulating tumor cells literally through the skin," says oncologist Klaus Pantel of the Hamburg-Eppendorf University Medical Center in Germany, who was not involved in the study. . But he and other people warn that there is still much to be done to show that the device will help people with melanoma.
Most researchers who work on ways to detect circulating cancer cells (CTC) look for them in blood taken from a person. In people with advanced breast, colon or prostate cancer, doctors may order a commercial test that counts CTCs in such a blood sample. But these approaches often fail to detect the few cells released by early cancers and do not work for melanoma because its cells do not carry the main surface marker used by the tests to detect CTCs.
Hoping to improve other methods, a team led by the University of Arkansas biomedical engineer Vladimir Zharov for medical science in Little Rock coupled a laser to an ultrasonic detector to create what they called the "Cytophone Because this device detects cells acoustically. ("Cyto" means cell.) When they project the Cytophone's laser onto the skin of an animal or person, so that its light penetrates a few millimeters into the blood vessels near the surface, melanoma cells in courses heat slightly because of their dark pigment, melanin. This harmless heating creates a tiny acoustic wave that is picked up by the ultrasonic detector.
When Zharov's team focused his device on a person's hand for a few seconds at a time and searched for the signals against the background noise from abundant red blood cells, absorbing less energy, it did not detect no CTC in 19 healthy volunteers. But in 27 of the 28 patients with melanoma, CTCs turned out to be peaks.
The Cytophone can take a single CTC in 1 liter of blood, which is up to 1000 times more sensitive than other detection methods that detect CTCs in a typical blood sample of 7.5 milliliters, announced today the team Translational medicine science. The device has also detected small blood clots that can develop and kill a cancer patient.
Curiously, when the researchers adjusted the laser to a higher energy level, but still safe, they also showed that a patient's CTC levels decreased over the hour, because the device was in destroy the cells without causing side effects. Although it is unlikely that a person's cancer will be completely eliminated – the initial tumor or metastatic tumors will continue to release cells – the Cytophone could be used to enhance the effects of an anti-cancer drug, Zharov says.
The device could be used to determine if an anti-cancer drug is working. If this is the case, the patient's CTC rate should drop, says Zharov, who, along with his colleagues, has patented the Cytophone and started a business to further develop it. "You can check periodically every 3 months and see if the melanoma reappears." It could also be used as a supplement to skin checks to improve melanoma screening, such as a mammogram for breast cancer, he suggests. And Zharov used this software to detect or monitor other types of cancer by labeling patients' CTCs with gold nanoparticles that, like melanin, would heat the cells.
But Pantel and others point out that these applications are very far apart. On the one hand, the team only tested three patients with early-stage melanoma. "They will have to show that they can find [CTCs] Anthony Lucci, MD Oncologist, MD Anderson Cancer Center, Houston, Texas.
Researchers must also determine if the Cytophone can detect CTCs in patients with darker skin. Because of their higher levels of melanin in normal cells, it may be difficult for the Cytophone to distinguish between cancer cells, says Shannon Stott, a mechanical engineer at Massachusetts General Hospital in Boston. . For now, she says, "This is a very cool and promising study."
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