Microbiology: A Systems Approach 4th Edition by Marjorie Kelly Cowan

Exercise 10

Your Spit: It Might Save Your Life
You've heard it at your dentist's office dozens of times: the whooshing sound of your saliva being sucked down the vacuum system when the assistant clears out your mouth with that plastic tube. What if that saliva could be the key to diagnosing diseases like cancer, Alzheimer's, Parkinson's, or diabetes According to recent research, it can.
Scientists have found short lengths of proteins called biomarkers excreted in the saliva whose presence can indicate disease status. Dr. David Wong, a dental expert at UCLA, along with groups at UCSF and the Scripps Research Institute have been cataloging these proteins and have identified over 2,200 proteins called the "salivary proteome." Many of these protein biomarkers can be the first indicators of disease. Wong says that about two-thirds of the proteins are produced normally by the salivary glands and are used to kill microbes and other pathogens, digest foods, or heal wounds within the mouth. The other one-third of the proteins come from other parts of the body and are then filtered through the blood and exit via the salivary glands. These proteins from the heart, liver, muscles, or other organs have no role in the mouth and elevated levels of these proteins can indicate disease.
Timothy Griffin, a biochemist at the University of Minnesota, has been studying the differences in salivary proteins between healthy people and those with cancer. He has found that the saliva of patients with cancer has unexpected proteins that occur at elevated levels or have been chemically modified when compared to patients who are cancer-free. Griffin has found biomarkers for oral cancer in patients who have not been diagnosed with the disease but only have an oral lesion or an elevated risk for cancer. Griffith's group has also been able to find biomarkers for breast cancer.
What was the first biomarker discovered by scientists
Other than in the saliva, where can biomarkers be detected
Even though Dr. Wong's group has cataloged thousands of different proteins that can be detected in the saliva, biomarkers are not limited to short peptide sequences. Biomarkers can be mRNA, DNA, or chemical pollutants excreted in the saliva or other bodily fluids. One of the first biomarkers discovered was lead. Dr. Herbert Needleman was an assistant professor at Harvard Medical School in the 1970s when he studied levels of lead in the blood of children and showed that the smallest detectable levels of lead could impair a child's IQ. His research spurred the removal of lead from gasoline and paint, which were the largest sources of human exposure to lead at the time. Even though levels of lead in the blood weren't considered biomarkers per se at the time, Needleman's research was among the first to measure a substance in the blood and relate its effect to a disease condition.

Needleman's research sparked a flurry of research into biomarkers, but scientists lacked an organized framework for biomarker studies and communicating with each other about their discoveries. In the 1980s, the National Research Council came up with four basic groupings of biomarkers:
Exposure biomarkers, which measure external exposure and internal dose
Effect biomarkers, which measure some impairment to health, like lead
Early disease precursors, or events that predict some health impairment
Susceptibility biomarkers, which include genetic markers or other disease characteristics
These categories represent a wide range of chemicals, proteins, and genetic material. Until recently, most biomarkers were detected in the blood, urine, or cerebrospinal fluid.
How is detection of biomarkers in saliva different than other types of body sampling