(Corrects last name of researcher to Hagen from Hagan in 2nd paragraph and makes conform throughout)

By Julie Steenhuysen

CHICAGO, March 25 (Reuters) - U.S. researchers have identified all 1,116 unique proteins found in human saliva glands, a discovery they said on Tuesday could usher in a wave of convenient, spit-based diagnostic tests that could be done without the need for a single drop of blood.

As many as 20 percent of the proteins that are found in saliva are also found in blood, said Fred Hagen, a researcher at the University of Rochester Medical Center in New York who worked on the study.

"This is potentially a large field that has many clinical implications in the area of disease diagnostics," said Hagen, whose work was published in the Journal of Proteome Research.

The researchers hope saliva-based tests could be used to diagnose cancer, heart disease, diabetes and a number of other conditions.

"To be able to diagnose disease using saliva, you really have to have a comprehensive understanding of the saliva proteome," Hagen said in a telephone interview.

Like a genome, which lists all of the genes in an organism, a proteome is a complete map of proteins. While genes provide the instruction manual, proteins carry out the instructions by regulating cellular processes.

Researchers from five universities -- the University of Rochester, The Scripps Research Institute, the University of Southern California, The University of California San Francisco and the University of California Los Angeles -- sought to determine the complete set of proteins secreted by the major salivary glands.

BLOOD, SPIT AND TEARS

They collected saliva from 23 healthy men and women of several races. They tested saliva samples using some form of mass spectrometry, which determines the identity of proteins based on measurements of their mass and charge.

They compared their findings with recent protein maps of human blood and tears.

Early analysis has already turned up a number of proteins with known roles in Alzheimer's, Huntington's and Parkinson's diseases; breast, colorectal and pancreatic cancer and diabetes.

Most of the proteins were part of signaling pathways, which are key to the body's response to systemwide diseases.

Hagen said the work should accelerate the development of new tools for tracking disease throughout the body.

Already there are saliva-based antibody tests to detect human immunodeficiency virus, or HIV, and hepatitis infections, Hagen said. He said this protein map will provide new targets.

"Monitoring disease as well as drug use could be more easily done with saliva as opposed to blood or urine," he said.

Other groups are working on a saliva-based test for breast cancer that would detect a protein fragment from the HER2 protein. Hagen said such tests could eventually replace uncomfortable and costly mammograms.

"We envision in the future spitting in a tube and looking for a marker like this breast cancer marker. It would be much easier to do, potentially at home," he said.

"Given that we've made this information publicly available, we fully expect a number of research groups will be picking their favorite targets and developing their own tests. That is the intent -- to create a wealth of data to stimulate more research and increase the chances of producing better diagnostic tests," Hagen said. (Editing by Maggie Fox and Mohammad Zargham)

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