Breath Test
UMaine chemist works to isolate the molecular biomarkers of ovarian cancer

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With all the ways in which human beings are different, breathing is one pursuit that remains decidedly universal. We may eat different foods, speak different languages and live different lifestyles, but the rhythmic pumping of our lungs is the same around the world. However, scientists are discovering that the molecular makeup of a breath may be as unique as the person from whom it was exhaled. Thousands of molecules, set adrift within a cloud of carbon dioxide, nitrogen and other gases, appear in precise combinations that can be identified and interpreted. And the story they tell, can, quite literally, mean the difference between life and death.

University of Maine chemistry professor Touradj Solouki, working in collaboration with researchers at the Pine Street Foundation in California, is applying advanced techniques in chemistry and proteomics to uncover the hidden signs of disease that linger in a human breath. Armed with electron guns, ion cyclotron resonance mass spectrometers, and other futuristic tools of the trade, he operates a device that is, in effect, an incredibly effective molecular trap — a trap he is using to delve into the secret life of cancer.

With nearly $500,000 in funding from the Department of Defense Ovarian Research Program, Solouki is using specialized molecular isolation techniques and one of the Northeast's most powerful superconducting magnets to isolate and identify molecules contained in a human breath. By comparing the molecular components found in a healthy person's breath with those found in the breath of a cancer patient, Solouki and his team hope to identify specific biomarkers that indicate the presence of ovarian cancer. While ovarian cancer is the fifth leading cause of cancer deaths in women, the disease has a 90 percent survival rate if detected in its early stages.

"We already know some potential markers for diabetes and high cholesterol that are present in human breath. The goal now is to find the biomarkers for ovarian cancer so that a sensor that uses this noninvasive method can be developed for use in hospitals," says Solouki, while recharging the lab's massive magnet with liquid nitrogen. "The device includes both high- and low-pressure instruments, so getting the different components to work together was a challenge. But by putting them together, you realize tremendous advantages."

The device professor Solouki and his research team have constructed is known by the rather unwieldy acronym PC/GC/FT-ICR MS, or Preconcentrator/Gas Chromatography/Fourier Transform Ion Cyclotron Resonance Mass Spectrometer. By linking several state-of-the-art technologies and standardizing the methods by which sample molecules are analyzed, Solouki has developed a greatly improved isolation procedure for examining individual molecules.

Homing in on individual molecules is no easy task, but the ability to do so is already opening new doors in chemistry, biotechnology and other fields. Solouki and his research group have used the technique in a variety of applications, from identifying biomarkers and disinfection by-products in drinking water to determining the country of origin for a sample of gasoline. The ability to isolate and manipulate molecules such as those exhaled in a breath is particularly important to the growing fields of proteomics and metabolomics.

Simply defined, proteomics is the large- scale study of the structures and functions of proteins. The human body contains more than 2 million different proteins, each with its own dynamic structure and function. In addition to modern genomic and DNA studies, understanding proteins — from the relatively short insulin molecule to giant muscle-forming proteins such as titin — and their functions is critical to improving human health.

Solouki and his team are able to separate the molecules that make up complex mixtures, such as the components of a human exhaled breath, by forcing them to sort into like groups as they travel through hundreds of meters of fine tubing. A specialized coating on the inside of the tube affects the movements of each type of molecule in a different way, causing them to segregate. The molecules are then captured in a device that is cooled by liquid nitrogen, remaining in a state of suspended animation at 200 degrees below zero, waiting to be released into the grip of a very strong superconducting magnet.

In the magnetic field, the molecules are ionized with a beam of electrons. The ionized molecules are trapped and their translational motion is further restricted using a combination of a strong magnetic field and an electrical field. These trapped ionized molecules can be identified according to the specific natural cyclotron frequencies at which they spin.

Solouki's collaborators at the Pine Street Foundation published a study in 2006 on the detection of early- and late-stage lung and breast cancers using samples of exhaled breath. In the study, dogs were used to "sniff out" cancer patients using only their highly sensitive noses. Breath samples from 86 people diagnosed with lung or breast cancer were presented to five professionally trained scent dogs, along with samples from 83 healthy controls.

The dogs were able to correctly identify or rule out lung and breast cancer at both early and late stages with an accuracy of more than 90 percent.

Researchers suspect that, unlike normal cells, cancer cells emit different metabolic waste products. Solouki's molecular identification techniques promise to determine the source of those differences, providing not only a new way of detecting cancer, but also a greater understanding of how the disease affects the body.

In the current project, Pine Street Foundation researchers will recruit ovarian cancer patients and control subjects, and apply the same methods used in the breast and lung cancer study — training dogs to detect the disease in samples of exhaled breath. Those same breath samples will be analyzed in Solouki's laboratory at UMaine to obtain a comprehensive and detailed inventory of the chemical compounds found in the breath of ovarian cancer patients.

"Canines have been used for a long time for detecting explosives and illegal drugs, and they are just starting to be used for biomedical purposes," says Solouki. "Dogs have shown a high rate of success in distinguishing between normal and abnormal breath samples associated with different types of cancer, and what we hope to determine is exactly what it is that the animals can detect. The ultimate goal of this research is to look at a patient's breath and biological fluids to build a picture of how they all relate. We want to know what is happening in the body at the molecular level so that we can develop better treatments."

The project is the first to use analysis of exhaled breath for early detection of ovarian cancer. Unlike blood tests, biopsies and some other cancer detection methods, the breath analysis approach is a truly noninvasive diagnostic technique. Once the biomarkers for ovarian cancer and other diseases are identified, a sensor could be developed for quick, accurate testing in hospitals and doctors' offices, increasing the chances of early detection and significantly improving the chances for successful treatment.

"The potential for using these techniques in the diagnosis and treatment of disease is almost limitless," says Solouki. "This project could really improve our ability to detect cancer in time to control it."

by David Munson
May-June, 2007

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