New Findings About Asbestos' Relation to Cancer

Clinical application is years away, however, the researchers hope
their findings could aid in drug development efforts targeting
illnesses caused by excessive exposure to asbestos, including the
deadly cancer called mesothelioma.

The researchers use atomic force microscopy to observe how a single
asbestos fiber binds with a specific receptor protein on cell
surfaces. They suspect that at least one of the more lethal forms of
asbestos triggers a cascade of events inside cells that eventually
lead to illness, sometimes decades later.

The conditions most commonly associated with long-term exposure to
airborne asbestos are lung cancer; asbestosis, a chronic respiratory
disease; and mesothelioma, a cancer that forms in the membrane lining
most internal organs of the body, including the lungs.

Eric Taylor, a doctoral candidate in earth sciences at Ohio State and
a coauthor of the study, describes atomic force microscopy as "Braille
on a molecular level," meaning it allows scientists to feel and
observe what's happening on molecular surfaces.

"We're looking at what molecules are involved in the chain of events
when the fiber touches the cell. Does the binding occur over minutes,
or hours? And what processes are triggered?" said Taylor, who
presented the research at the American Geophysical Union meeting in
San Francisco.
Asbestos comprises six different minerals that naturally occur in both
fragment and fibrous forms. Because of its high durability and heat
resistance, the fibrous form has been used in many manufacturing
products since the late 1800s. Though its use is now highly regulated,
asbestos is still present in many materials. The U.S. Department of
Labor estimates that 1.3 million employees face significant asbestos
exposure on the job. Environmental exposure is also possible because
asbestos is a naturally occurring mineral in soils and exposed
bedrock.

Crocidolite, or blue asbestos, is part of the amphibole group of
asbestos minerals, which were banned in most of the Western world by
the mid-1980s. Before that, they were used in such products as ceiling
tiles and thermal insulation.

Ohio State researchers have focused so far on the crocidolite form of
asbestos, but eventually hope to study how all six forms of asbestos
interact with certain proteins on cell surfaces. Some forms of
asbestos can dissolve in the lungs if they are inhaled, but others are
believed to essentially "stick" to cells, especially at high
concentrations, and eventually cause lung diseases.

"For the first time, this will give us data on biological activity
that should help policymakers determine which forms of asbestos are
the most dangerous," said Steven Lower, associate professor of earth
sciences at Ohio State and a coauthor on the study.

"The hypothesis we're testing is that binding of cell surface
receptors to asbestos fibers triggers a signal event, which initiates
the cancer," said Lower, also a faculty member in the School of
Environment and Natural Resources. "There seems to be something
intrinsic about certain types of asbestos, blue asbestos in
particular, that elicits a unique signal, and it triggers
inflammation, the formation of pre-malignant cells and, ultimately,
cancer."

The first protein to be studied is epidermal growth factor receptor,
which is present on the surface of every human cell. Understanding the
intricacies of the binding process between the mineral and one or more
proteins will provide an index of the biological activity of a
particular type of asbestos, and might lead the researchers to figure
out how to prevent or undo that interaction, Lower said.

Taylor said the driving motivation behind the research is the
potential to find a way to intervene and prevent illness even after
someone is exposed to asbestos. Mesothelioma symptoms don't typically
appear until 30 to 50 years after exposure. After diagnosis, however,
the cancer is difficult to control, and there is no cure.