[SCIENCE] A Conversation with David Wong
- A CONVERSATION WITH DAVID WONG
A Bloodless Revolution: Spit Will Tell What Ails You
By CLAUDIA DREIFUS
The New York Times
Published: April 19, 2005
BALTIMORE - Unlike the rest of us, David Wong enjoys talking about
He likes to speak of its texture, color, scent and sociology. Spend a
few hours with him and one learns that saliva is the lubricant that
makes food and language possible and that at certain Greek weddings,
celebrants spit on the bride and groom for good luck.
If Dr. Wong, 50, the associate dean for research at the U.C.L.A.
School of Dentistry, is singular in his conversation, it is because
he has seen the future, and it is spit.
At his laboratory, Dr. Wong has been investigating the molecular
content of saliva, with the hope of developing a whole new category
of tests for diagnosing human diseases.
"If you consider the eyes the window to the soul, then spit is a
window to the body," he said during a break at a recent dentistry
conference in Baltimore. "It is a part of circulation. It came from
it. It doesn't have the color of blood, but it's less sticky. A
saliva test will be totally noninvasive."
Q. How did spit become your research topic?
A. Three years ago, the National Institute of Dental and Craniofacial
Research put out a "request for applications," an R.F.A., which is a
kind of money-carrot to researchers saying, "This is what we'd like
to get done."
In this case, this government agency offered $57 million dollars to
scientists to build tools to detect the molecular components of
saliva. A sample of saliva can have within it DNA, RNA, proteins,
germs, viruses, fatty acids and a host of interesting molecules
useful in disease detection. This R.F.A. was a sign that the
government was putting serious effort behind developing a saliva-
based diagnostic test for various diseases.
I'm both a molecular biologist and a dentist. And dentists really
know their spit: we work with it every day. So this seemed a natural
for my lab. When the grants were finally announced, ours was one of
nine laboratories around the country put to work on this project.
Q. Why should we use spit for diagnoses? What's wrong with a blood
A. It's invasive. You have to puncture veins to get it. And with
needles, there's always the danger of secondary infections.
With saliva, all a patient has to do is expectorate.
Moreover, you can monitor saliva frequently so it's possible to
follow real-time changes in the body. If you want to collect samples
from a patient, you can take saliva 10 times a day. Can you imagine
being needled 10 times a day? No, no, no! I really don't like giving
blood. I have to prepare myself mentally for it.
Q. Is this idea of saliva as a medical gauge a new idea?
A. It's been around awhile. But I think it's going to happen now. The
time is right. We've long known that whatever is in blood is also in
saliva. It is, in fact, a reflection of our blood; it's a blood
filtrate. So the content of saliva might include many molecules we
can use in diagnosis.
In fact, anything present in blood is also in spit - though in much
smaller quantities. The problem was, We didn't have the means to
detect most of it until recently. And knowing exactly what's in there
is critical because we need to know if it changes when somebody is
Do the proteins in saliva change when someone becomes diabetic or
develops a disease process like cancer? If so, we can use molecular
profiles of "healthy spit" and "sick spit" to screen for disease.
Now, the big change in saliva's possibilities came only three years
ago, when engineers developed highly sensitive sensors that can
detect molecules at minute levels. These non-electrical mechanical
systems can locate one anthrax spore in a huge public space. And this
same technology can detect obscure molecules in saliva.
Q. To create a workable test, won't you need to do more than chart
the molecular content of saliva?
A. We need to know how salivary proteins change when someone is sick.
At my lab, we are developing saliva "disease profiles" for breast
cancer, oral cancer, diabetes 2, Sjogren's syndrome and ovarian
cancer. If we can get a picture of what saliva looks like in these
diseases and get to compare it to that of healthy people, we might
have the basis of a test.
Think about this scenario: Two years from now, when you go to a
dentist, before they clean your teeth, they'll take a drop of saliva
and put it into a little machine. At the end of the visit, you will
get a printed chart that will tell if you're at risk for Disease A or
Disease B and if you should have a follow-up with a medical doctor.
The dentist in the very near future may become a triage doctor.
That's going to change dentistry.
Q. Dentists don't get much respect, do they?
A. No. And they have a self-esteem problem. Dentists, generally,
don't make the first call on a serious medical problem. If someone
goes to the E.R. with a gunshot wound in the jaw, the doctors will
call the dentist only later to fix up the mouth. This could reverse
the process. And that's important because more people go more
regularly to dentists than to other kinds of health care
I really believe this test could change the mentality of dentistry as
Q. You say this is only two years away. Why?
A. We're close already. Saliva tests are in use right now for H.I.V.
and substance abuse. At my lab, we have the concept for an oral
cancer test ready. The prototype will be available in about a year.
Our work on oral cancer helped us prove that there is RNA associated
with diseases in saliva. This is a breakthrough, which started when
Maie St. John, a U.C.L.A. resident in neck surgery who also works in
my lab, looked at some earlier research I'd done.
She saw that there were elevated levels of an RNA molecule in oral
cancer cells. She then asked, "Does this oral cancer marker appear in
saliva too?" We began looking, and wow, we found it! Four RNA markers
were able to discriminate with 91 percent accuracy whether what we
had was saliva for a normal person or an oral cancer patient.
The next question was, Are there other RNA's in saliva? Amazingly, we
found a world of RNA in there. We then asked if this RNA is
associated with specific diseases. That's the $6 million question. So
far, we've made a lot of progress on finding a breast cancer marker
Q. Do you own the patent on the saliva tests?
A. U.C.L.A. will. Some part of it comes back to my academic
Q. Let's face it, saliva is a body fluid with a lot of negative
connotations. Will you need to do some public relations work before
you market your test?
A. I know what you're saying. If someone spits at you, it's not a
good thing. Giving spit or spitting, it's thought of as unhealthy
behavior. On the other hand, people share saliva when they are
intimate. They don't have a problem with that.
As a dentist, I've seen what happens to people who've lost their
salivary glands because of cancer and who don't have spit. They can't
speak or swallow. Saliva is a lubricant. Without it, the mouth is
sandpaper. When you've seen what happens to these patients, you come
to value what others consider an uncharismatic body fluid. I wish,
someday, we could say that saliva is a charismatic fluid.