Dirty Mouth? Clean It Up with Cancer Screening

by Katie Pratt

We can all tell when someone ate a piece of garlic bread, or just brushed their teeth, or should have brushed their teeth, but it turns out there is far more to learn from a person’s exhalation than what they ate for dinner last night. Indeed our breath exhibits an individuality that is almost on a par with our fingerprints.

As well as the obvious aromatics that we can smell, we are constantly breathing out volatile organic compounds (VOCs) that are a normal by-product of cellular metabolism. A 1999 study found over 3000 different VOCs in the breath of 50 volunteers, the combination of which varied widely. Since then the challenge has been to decipher the information contained in the “VOC code”, and researchers have made considerable progress in using VOC profiles to detect metabolic diseases and various types of cancers.

Cancer cells often have a drastically altered metabolism and therefore excrete different chemicals into the blood stream. For example, certain types of breast cancer are known to release increased levels of pentane, which is a result of elevated oxygen free radical activity. Once in the blood, such VOCs can cross into the alveoli of the lungs and are subsequently breathed out. Measuring VOC levels in a patient’s breath therefore represents a non-invasive early-screening method for detecting different kinds of cancer.

The first challenge in using VOCs as a biomarker for cancer is to develop reliable, fast, and cheap methods for detecting them. Earlier this year it was reported that dogs have the olfactory skills needed to sniff out bowel cancer. But humans have a relatively primitive sense of smell, so researchers at Technicon – Israel Institute of Technology in Haifa, have been perfecting the Nanoscale Artificial Nose (Na-Nose, or E-Nose for Electronic Nose). This device utilizes tiny particles of gold conjugated to molecules that interact with VOCs. Different combinations of detector molecules, or ligands, can be used depending on what VOCs you want to “smell”. Importantly the Na-Nose can be synthesized in such a way that it can ignore potentially confounding VOCs present in a patient’s breath that often result from smoking, gender, or medications.

This may feel a little cold and wet...

In their most recent work, Haick’s team has been using the Na-Nose technology to identify head-and-neck cancers (HNCs). These cancers are particularly nasty as they are generally diagnosed late (due to being asymptomatic initially), have a high rate of metastasis, and any surgical treatments can be distressingly disfiguring. More often than not, heavy smoking and/or drinking cause these cancers, but between 25-35% of mouth and throat cancers are caused by viral infection with HPV (human papilloma virus). HNCs therefore represent a group of cancers in grave need of an early screening method.

The current work successfully used a specialized Na-Nose to differentiate between HNC and healthy patients in a small sample of patients. In addition the researchers showed that it could tell the difference between HNCs and lung cancers, although this was slightly less reliable. They also identified six specific VOCs associated with HNCs that were present at much higher levels than in healthy volunteers.

While some experts see this technology as a novel and under-developed system, Haick’s group believes that it could be utilized in the clinic in a matter of years; the ease of testing and cost-effectiveness of the Na-Nose is very attractive. Instituting the test as a means of screening at-risk individuals, or for following up with HNC survivors would undoubtedly increase the rates of early-detection and thus survival rates (which are currently less than 50%). And it’s considerably less bizarre than breathing on a dog to find out if you’re sick.

Katie Pratt is a graduate student in Molecular Biology at Brown University. She has a passion for science communication, and in an attempt to bring hardcore biology and medicine to everyone, she blogs jargon-free at www.katiephd.com. Follow her escapades in the lab and online on Twitter.

Be the first one to mind the gap by leaving the correct virus name as a comment and get your name in the blog along with a sweet new BenchFly mug!

UPDATE: Congratulations to Dr. 27 – winner of this edition of Mind the Gap!

About the winner: Dr 27 is really almost 30, but she started her blog at 27, hoping to finish the PhD by that age (she did, but at 28). She’s a postdoc in structural biology living in Canada, hoping to get a “real job” real soon. You can follow her on Twitter.

About the prize: In addition to fame and glory beyond their wildest dreams, winners receive our new hot-off-the-presses large (15 oz) BenchFly mug to help quench their unending thirst for scientific knowledge… or coffee.