Research linking Ashkenazi Jews and breast cancer genes beset by problems
New study questions use of ethnic identity as proxy for genetic differences
Genetic research over the past decade has linked Ashkenazi Jewish ethnicity to an increased risk for hereditary breast cancer, so much so that certain gene mutations have become known as "Jewish ancestral mutations." But a new study released in the November 2006 issue of The American Journal of Public Health challenges this population-based approach, warning that disparities in access to care and other unintended consequences for specific ethic groups can result, and may have already occurred.
The study, conducted by Columbia University College of Physicians & Surgeons researchers, notes that while three recognized breast cancer mutations are present in two-three percent of the Ashkenazi Jewish population, similar prevalence studies have not been carried out in other ethnic groups. In addition, the study finds that research linking the breast cancer mutations with Ashkenazi Jews has been beset by methodological problems that cast doubt on the use of ethnicity as the basis for genetic research on disease.
"The linking of Ashkenazi Jews to a deadly disease raises serious scientific and social concerns," said co-author Sheila M. Rothman, Ph.D., professor of sociomedical sciences at the Center for the Study of Society and Medicine at Columbia University College of Physicians & Surgeons. "Focusing genetic studies on a specific ethnic group may confer disadvantages to that group and others. This finding in Ashkenazi Jews raises the risk of stigmatization and insurance or job discrimination. For other groups, it introduces a gap in access to testing and treatment."
The report cites examples of disparities that have occurred. For instance, Ashkenazi Jewish women have access to an inexpensive test that detects the mutations at a cost of $415 compared with $2,975 for the test for non-Ashkenazi Jewish women without known family mutations. Other studies have found that Ashkenazi Jewish women with family histories of breast cancer are more than twice as likely as other women at similar risk to undergo testing for suspect genes.
Dr. Rothman and her coauthors interviewed 30 genetic researchers and conducted a review of genetic and historical literature on the Ashkenazi Jewish population. The interviews revealed how geneticists came to substitute ethnicity for family history as the most relevant indicator of risk.
Serendipity played a vital role. Researchers had previously found a high prevalence of a mutation causing Tay-Sachs disease in Ashkenazi Jews. Within 20 years, one million Jews around the world had been tested for the Tay-Sachs mutation, and scientific institutions had created large repositories of genetic samples that could then be screened for other mutations including those associated with breast cancer--but only in Ashkenazi Jews.
"The science of breast cancer genetics has been marked by methodological inconsistency in how researchers defined 'Ashkenazi Jew,'" said study coauthor Sherry Brandt-Rauf, J.D., associate research scholar at the Center. Most scientists relied on study participants' self-identification. Ashkenazi Jews are descended from Jews who lived in central and Eastern Europe, but a complex history of migrations, and multiple cultural and religious meanings of Ashkenazi, makes self-identification problematic.
The study also illuminates how geneticists interpreted Jewish history to support the theory of Ashkenazi genetic uniqueness. This interpretation views the historic Ashkenazi Jewish population as isolated, and as having undergone extreme expansions and contractions. It attributes Ashkenazi Jewish genetic uniqueness to "founder effects," the idea that genetic mutations can take hold and spread within small, geographically isolated populations, such as a group living alone on an island.
Although Ashkenazi Jews were never geographically isolated, Rothman said that "researchers made persecution--the pogroms and massacres in Jewish history--the equivalent of geographic isolation."
The study noted that a number of recent genetic surveys--including among Spanish, German, Dutch, Polish and Hispanic women--have shown a high presence of the so-called "ancestral Jewish mutations" in non-Ashkenazi and non-Jewish groups. For example, a large study of Spanish women with breast cancer reported that one of the three mutations accounted for 16.7 percent of all mutations in the gene.
While the authors recognize the public health advantages of focusing genetic research on ethnic groups, "Our major concern is the largely unacknowledged disadvantages," Dr. Rothman said. "Serendipity may initiate a scientific quest, but should it continue to drive it--and to whose benefit?"
Media may obtain a copy of "Ashkenazi Jews and Breast Cancer: The Consequences of Linking Ethnic Identity to Genetic Disease," in the November 2006 issue of the American Journal ofPublic Health by contacting Olivia Chang at [email protected]. A copy of journal can be obtained by visiting www.ajph.org/subscriptions.
Columbia University Medical Center provides international leadership in pre-clinical and clinical research, in medical and health sciences education, and in patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, nurses, dentists, and public health professionals at the College of Physicians & Surgeons, the College of Dental Medicine, the School of Nursing, the Mailman School of Public Health, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. www.cumc.columbia.edu
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