Allergies, Asthma May Protect Against Brain Cancer
Study Shows a Genetic Link Between the 2
July 15, 2005 -- Early genetic research raises the possibility that
allergies and asthma may help protect against a deadly form of brain
The findings, while preliminary, could help advance the understanding of the
immune system's role in cancer, researchers say.
The newly published study suggests that variations in specific genes that
have been linked to asthma, hay fever, and other allergic conditions may also
be associated with a decreased risk for the brain tumor known as glioblastoma
Glioblastomas, or gliomas, are the most common type of brain cancers and are
more common in the elderly. The tumor occurs in 13 out of 100,000 people over
age 65, and the five-year survival rate in this age group is very low.
Genetic Link Explored
The study is not the first to suggest that people with allergies appear to
have a lower risk of developing the deadly tumor. Researchers with the National
Cancer Institute came to the same conclusion in a 2002 study that compared
allergy history among people with and without gliomas.
The new study is the first, however, to show a possible genetic reason for
Researchers from Ohio State University and Sweden's Karolinska Institute
looked for evidence of common genetic variants on two genes that have been
linked to asthma and allergies -- IL4RA and IL-13.
They analyzed DNA samples from 111 patients with glioblastoma tumors and 422
people without brain tumors. The participants were also questioned about their
allergy and asthma history.
Epidemiologist and researcher Judith Schwartzbaum, PhD, tells WebMD that
people with two specific genetic variants for IL-4RA were twice as likely to
have asthma but 40% less likely to have a glioblastoma. A similar association
was seen for two variations on the IL-13 gene.
The study is published in the July 15 issue of the journal Cancer
Is Inflammation the Key?
IL-4RA and IL-13 genes help regulate chemical messengers called cytokines,
which control the actions of cells that drive the immune system.
Schwartzbaum says it is not yet clear if these chemicals play a direct role
in the development of brain tumors or if allergies and gliomas share a common
pathway within the immune system.
Another possibility, she says, is that the immune response that is triggered
in people with asthma and allergies helps protect them against the brain
cancer. This is just speculation, but Schwartzbaum says the implications of
such an association would be great.
"If this is the case the question becomes, 'How aggressively should you
treat these conditions?'" she tells WebMD. "Obviously, people can die
from asthma. It is a serious disease that needs to be treated. But it could be
that a little bit of hay fever may be a good thing."