Sylvester Comprehensive Cancer Center

Cancer Researchers Find Genetic Differences in Breast Tissue Among Races


Results from a pilot study by scientists from Sylvester Comprehensive Cancer Center at the University of Miami Miller School of Medicine suggest underlying genetic differences among ethnic groups are present not just in tumors, but in normal breast tissue as well. These findings may partially explain why women of certain ethnic backgrounds are more susceptible and at a higher risk for certain breast cancers than others.

Lisa Baumbach, Ph.D., associate research professor of neurology, and Mark Pegram, M.D., professor of medicine and director of the Clinical and Translational Research Program at the Braman Family Breast Cancer Institute, led the study which is being presented at the American Association for Cancer Research 102nd Annual Meeting 2011 in Orlando on April 4.

“Our group has been working for quite some time on the hypothesis that there are underlying genetic differences in breast tissue across ethnicities,” said Baumbach, “which would explain, at least in part, disparities in morbidity and mortality.”

Baumbach’s research group is investigating a multi-ethnic cohort of patients with triple-negative breast cancer, including 10 blacks, 10 Hispanics and 10 non-Hispanic whites. Study samples were marked by pathology as normal vs. tumor tissue. They were then analyzed for RNA isolation, cDNA preparation and hybridization of tumor/normal cDNAs and compared to a breast cancer focused gene expression array.

Previously, the Baumbach-Pegram team had observed genetic differences in breast tumor tissue among women of different ethnicities, African-American, Hispanic and non-Hispanic Whites. In this study, partially funded by a Bankhead-Coley Grant from the State of Florida, the researchers examined normal breast tissue, with no sign of disease. “We wanted to see if women from different ethnicities are at a higher risk from the very start,” said Baumbach.

They found there were statistically significant differences in a subset of genes among the three different ethnic groups. Between African-American and Caucasian women, there were as many as 65 genes that expressed at least a two-fold change in over or under expression, with one gene under expressed ten times less in African-Americans. Hispanics also showed a distinct difference in normal breast tissue compared to Caucasian women, with most of the genes over expressed. The greatest difference was between Hispanics and African-Americans with 82 genes showing statistical differentiation.

The sample was small and more analysis is needed, Baumbach says, but the findings point to a clear need. “If women from different ethnicities are at a higher risk of breast cancer from the very start,” said Baumbach, “we may need to change screening recommendations.” She adds that diet and environment may also require re-examination. Over the rest of the year, Baumbach and her team plan to further these studies by dissecting the epithelial and surrounding breast tissue in these normal samples to further understand interactions of the microenvironment in normal breast tissue. Significant data suggests that breast tissue microenvironment contributes to tumor formation.

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