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In April, researchers at USC’s Keck School of Medicine and
Harvard
Medical
School
reported in the journal Nature Genetics that they have identified
genetic risk factors that independently and in combination predict the
occurrence of prostate cancer.
The
study focused on seven DNA sequences clustered in a single region of the
human genome on chromosome 8. Two other studies, one from
Iceland
and another other from the National Cancer Institute in the
US
, were published in the same issue, and independently support the
findings of the USC/Harvard team.
The
USC/Harvard study has generated substantial interest in the scientific
community because the genetic variants identified by the researchers
predict more than a five-fold range of risk for prostate cancer. The
study is also noteworthy because the seven genetic areas related to
prostate cancer risk are located in a region that has traditionally been
thought to contain unimportant non-coding DNA material.
“These
sequences are not ‘junk DNA,’” said Brian Henderson, M.D., the
paper’s co-author and dean of the Keck School of Medicine. “The
discovery of multiple, independent genetic changes that are in close
proximity to one another, but outside any known gene, suggests that
these results may also teach us about novel molecular mechanisms whereby
DNA changes can alter risk of disease.”
Christopher
Haiman, Ph.D., assistant professor of preventive medicine at USC and
lead author of the Nature article, noted that the newly
defined genetic areas contain both germ-line and somatic variations, a
combination not previously reported.
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| Christopher
Haiman, Ph.D., assistant
professor of preventive medicine at the Keck School of Medicine
and lead author of the Nature Genetics article . |
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While
both Henderson and Haiman agree it is too early to fully understand the
biology of the findings, the discovery of seven genetic variants may
help explain why African-American men have a greater risk for prostate
cancer than other populations in the
United States
. In
the study, almost all of the variants were found at a higher frequency
in African-American men. “Screening for the presence of these variants
may explain from 30 percent to as much as 70 percent of prostate cancer
cases in this population,” Haiman added.
New
tests based on the predictive power of the variants could help prevent
prostate cancer by enabling doctors to identify men who should be
prioritized for early screening and prevention efforts. Prostate cancer
is the third-leading cause of cancer-related deaths among men, and has
long been associated with risk factors such as age, race, family
history, nationality, diet, and exercise, with the first three
considered the most important.
So
what are the next steps for the USC/Harvard team?
While Haiman believes that the data from this study may be
applicable to other disease states, he isn’t ready to make any
predictions regarding the promise of new targeted therapies. He believes
that the data are strong, but too new to fully understand.
“Whatever
it is, it’s happening, and further sequencing of the variants will
reveal more information,” he said. “We need more subjects and the
money to conduct more comprehensive sequencing in order to further
understand the implications of our original findings.
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MaryAnn
Foote provides consulting services to biopharmaceutical companies. She
can be reached at: 805-370-6360 or mawriter@aol.com.
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