DESCRIPTION: (Adapted from Investigator's Abstract) While our knowledge
about the penetrance and attributable risks associated with BRCA1 and BRCA2
mutations is continuing to be refined, the potential impact of these genes
in minority populations remains largely unknown. As examples from the
Ashkenazi Jewish and Icelandic subpopulations have demonstrated, different
ethnic groups are likely to have different spectrums of mutations and
polymorphisms occurring in BRCA1 and BRCA2. The identification of germline
mutations in cancer susceptibility genes such as BRCA1 and BRCA2 has opened
up the possibility of identifying and characterizing high risk families and
individuals. However, at the present time, the broad spectrum of mutations,
limited knowledge of the functional role of these genes, and incomplete
information on gene penetrance and factors that affect expression of these
genes (i.e., gene-gene and gene-environment interactions) severely limit the
practical application of such knowledge in cancer prevention and counseling.
The investigators state that this application proposes to utilize a large
multi-ethnic population-based cohort that will provide greater heterogeneity
of gene mutations, allele frequencies, and environmental exposures than
would be available within any single ethnic group. To fully exploit this
multi-ethnic resource, they state they are studying families affected with
at least two cases of breast or ovarian cancer and comparing affected and
unaffected siblings within and across ethnic groups.
Specifically, this application will investigate the role of BRCA1, BRCA2,
the cytochrome P450cl7alpha gene (CYP17), and the 17beta-hydroxysteroid
dehydrogenase 1 gene (HSD17B1) among African-American and Latino families
with a history of breast and ovarian cancer and evaluate possible gene-gene
and gene-environment interactions in the etiology of breast cancer. The
primary rationale for studying families is to increase substantially the
efficiency with which the specific aims can be achieved. Focusing on
sibships with a family history of breast cancer will increase the proportion
of subjects who carry a mutation in BRCA1 or BRCA2. Consequently, this will
substantially increase the power of the study to estimate main effects and
interactions. Further, the investigators state that a family-based design
offers the advantage of being able to determine the role of polymorphisms in
metabolic genes involved in estrogen biosynthesis without underlying
confounding that can be introduced from genetic heterogeneity.
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