Before long, it may be possible to detect melanoma by its odor.
Scientists have known for several years that melanoma, like some other cancers, has a distinct smell; in fact, dogs have been trained to sniff it out. Although dogs have proved to be inconsistent diagnosticians, scientists have looked for other ways to screen for cancer using its distinct scent.
Researchers at Monell Chemical Senses Center and the University of Pennsylvania have focused on the airborne molecules known as volatile organic compounds (VOCs) that are produced by human skin, many of which are odorous.1
“There is a potential wealth of information waiting to be extracted from examination of VOCs associated with various diseases, including cancers, genetic disorders, and viral or bacterial infections,” said George Preti, PhD, one of the study’s authors.
The researchers grew melanoma cells in culture and used an absorbent device to collect VOCs from normal melanocytes and from melanoma cells at three stages of the disease—radial growth phase, vertical growth phase, and metastasis. They then used gas chromatography-mass spectrometry techniques to analyze the compounds, identify VOC profiles from the three disease stages, and compare them with the VOC profiles of normal cells.
Overall, thirty-one VOCs were identified. The types and concentrations of VOCs in the melanoma cells differed from those in the normal cells—some VOCs that were present in melanoma cells did not appear in normal cells, and VOCs that diseased and normal cells shared occurred in higher or lower concentrations in the melanoma cells. VOC profiles could also be used to differentiate the three stages of melanoma.
Translating these findings into a screening tool would require a reliable and portable device, so the researchers tested a nanosensor, which is constructed of nano-sized carbon tubes coated with strands of DNA. The sensors can be bioengineered to recognize a wide variety of molecules, and were able to distinguish differences in VOCs produced by the normal cells and the different types of melanoma cells, with a high degree of test-retest reliability.
According to the study authors, these findings provide proof-of-concept regarding the potential of this technique to detect and identify biomarkers that distinguish melanoma cells from normal melanocytes and differentiate among stages of melanoma. They suggest that “e-nose” technology employing nanosensors that are highly selective for endogenous melanoma biomarkers may come to play an important role in screening for melanoma.
Nanosensors aren’t likely to replace visual surveillance and biopsy to diagnose melanoma, but they might play an important role in early detection, which, in turn, could reduce the mortality rate from this often-deadly form of skin cancer.
Nevertheless, don’t count dogs out for detecting melanoma. A small study found that two dogs, a schnauzer and a golden retriever, were able to detect melanoma in seven patients and could distinguish between localized and nonlocalized disease, with good inter-observer reliability.2 While nano-technology continues to be researched as a means to improve melanoma detection, using dogs to detect skin cancer may offer some diagnostic insight—after all, it is probably much less expensive, even when factoring in the cost of chew toys.
1. Kwak J, Gallagher M, Ozdener MH, et al. Volatile biomarkers from human melanoma cells. Journal of Chromatography B. 2013;931:90-6.
2. Pickel D, Manucy GP, Walker DB, Hall SB, Walker SC. Evidence for canine olfactory detection of melanoma. Appl Animal Behav Sci. 2004;89:107-16.