• 7/20/2005
  • South Bend, IN
  • Patty Levine
  • South Bend Tribune (www.southbendtribune.com)

At your next periodic dental checkup and cleaning, your dentist might take a few extra minutes to examine your tongue, gums, the roof and floor of your mouth. This thorough mouth exam probes for oral cancer, a disease which will strike 30, 000 Americans this year and kill 8,000.

But within two years, you may be able to go for your regular dental visit, spit in a cup and, before the appointment is over, find out from an analysis of your saliva whether you’re at risk for oral cancer.

In a small study reported last year, at the American Association for Cancer Research in Anaheim, Calif., researchers from the UCLA School of Dentistry found that genetic “biomarkers” isolated in saliva predicted oral cancer in about nine out of 10 cases. According to this team of scientists, out of about 3,000 distinct bits of genetic material called messenger RNA in saliva, the appearance of four particular “biomarkers” may signal the presence of cancer of the mouth, tongue, larynx or pharynx — even before any symptoms appear. Although it is not yet clear whether these four RNA particles are detectable because their corresponding genes are activated, or whether their presence indicates the body’s inflammatory response to the cancer, the use of saliva for predicting cancer is significant.

And in a study reported this past April from Johns Hopkins Medical Institutions, scientists found that an increase of another type of genetic material found in saliva, mitochondrial DNA, is a reliable marker for head and neck cancer.

Welcome to the brave new world of saliva testing. Saliva is a health drink for your teeth and mouth. The three or so pints produced by the salivary glands each day contain antibacterial substances that protect teeth from cavities as well as calcium and phosphorus that teeth absorb. Saliva also serves to lubricate the mouth, keeping food from sticking to your teeth and gums. Saliva neutralizes gastric acid and may help check gastroesophageal reflux (GERD), a leading cause of heartburn.

Saliva, a near cousin to blood, is also a medical treasure-trove of proteins, hormones, antibodies and other molecular substances found in the clear part of blood, albeit in weakened concentrations.

According to Dr. Mythily Srinivasin, an assistant professor of oral pathology at the University of Indiana School of Dentistry, until just a few years ago, the technology to analyze minute quantities of genetic material and proteins in saliva wasn’t available. But in today’s scientific world of genomics and proteomics — the study of genes and the proteins they make — highly sensitive nanotechnology-based sensors (ultra-tiny machines that read the simplest cell structure) permit the detection of disease-bearing biomarkers in saliva.

Srinivasin says that saliva testing is less invasive and less painful than blood testing, and because there is no need for a phlebotomist, potentially less expensive. And since saliva can be tested repeatedly during the day, doctors can use these tests to keep track of real-time physiological responses, such as how a patient with an infection responds to a course of antibiotics.

Dr. Richard Gregory, professor of oral biology at the Indiana University School of Dentistry, says that scientists and researchers have long been intrigued by what can be studied in saliva. There are already saliva-based tests available to detect the presence of the HIV/AIDS virus, alcohol, illegal drugs, the influenza virus, hormones related to ovulation and premature labor, and levels of hormones such as testosterone, estrogen and cortisol.

A significant amount of money already has been earmarked to encourage development of salivary tests. The National Center for Dental and Craniofacial Research has designated $64 million for this, and the center has put an additional $15 million toward a project called the Salivary Proteome Program whose goal is to compile a complete catalog of all the proteins in saliva. If normal levels of proteins are known, tests then can be developed to detect when protein levels become abnormal.

But there’s more. Within a few years, we may be spitting in our doctors’ offices as well. Researchers have already shown that proteins such as Her-2/neu — linked to breast cancer — and CA-125 — linked to ovarian cancer — can be detected in saliva, leading researchers to the conclusion that a screening test for these cancers could be developed. Gregory adds that because saliva testing can be used to monitor levels of C-reactive protein, it can be used as a general marker of increased risk of heart disease and rheumatoid arthritis.

Studies also are currently under way to determine whether saliva DNA testing can accurately evaluate how well levels of serotonin, a neurotransmitter linked to depression, can be controlled by a person’s brain– an important screening test for a person’s risk for depression and his or her chance of responding to antidepressant medications.

Saliva has not yet yielded a successful test for diabetes. Monitoring their diabetes through saliva testing would be of great benefit for diabetics who now must use their blood to check sugar levels. Srinivasin holds out hope that there might be other markers in saliva that may yet be used to detect diabetes.