Compared with the general population, women who have inherited a germline mutation in the BRCA1 gene have a greatly increased risk of developing breast cancer. However, there is also substantial interindividual variability in the occurrence of breast cancer among BRCA1 mutation carriers. We hypothesize that other genes, particularly those involved in endocrine signaling, may modify the BRCA1-associated age-specific breast cancer risk. We studied the effect of the CAG repeat-length polymorphism found in exon 1 of the androgen-receptor (AR) gene (AR-CAG). AR alleles containing longer CAG repeat lengths are associated with a decreased ability to activate androgen-responsive genes. Using a sample of women who inherited germline BRCA1 mutations, we compared AR-CAG repeat length in 165 women with and 139 women without breast cancer. We found that women were at significantly increased risk of breast cancer if they carried at least one AR allele with >/=28 CAG repeats. Women who carried an AR-CAG allele of >/=28, >/=29, or >/=30 repeats were given a diagnosis 0.8, 1.8, or 6.3 years earlier than women who did not carry at least one such allele. All 11 women in our sample who carried at least one AR-CAG allele with >/=29 repeats had breast cancer. Our results support the hypothesis that age at breast cancer diagnosis is earlier among BRCA1 mutation carriers who carry very long AR-CAG repeats. These results suggest that pathways involving androgen signaling may affect the risk of BRCA1-associated breast cancer.

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Inherited susceptibility to breast cancer has been an area of intense investigation for the past 10 years. Early work focused on identifying modes of transmission, which culminated in the identification of chromosome 17q12-21 as the first human genomic region that harbored an autosomal dominant susceptibility gene for breast cancer (BRCA1) in 1990. BRCA1 was subsequently identified and was followed shortly by the identification of BRCA2. Research in the past 3 years has elucidated much about the mutation spectrum and mutation frequency of these genes in specific populations and is beginning to identify potential functions. Whereas progress in this area has been rapid and much is now known about inherited susceptibility to breast cancer, much more needs to be done to make these discoveries useful in the diagnosis, treatment, and ultimately, the prevention of breast cancer.

BACKGROUND Incidence of cutaneous melanoma continues to increase in the Caucasian population worldwide. Approximately 5% of melanoma patients develop additional primary melanoma. This rate is significantly higher than the estimated lifetime risk of an individual for developing the disease (1.4%). These features suggest that a genetic predisposition may underlie multiple primary melanomas (MPMs). Prior studies had identified CDKN2A mutations in a few MPM individuals. The objectives of this study were to determine the frequency of family history of melanoma in MPM cases, to characterize other clinical features including history of other cancer, and to determine the association with functional CDKN2A mutations. METHODS This study used a case series design. All living patients who had been seen in the Pigmented Lesion Clinic at the University of Pennsylvania and who had more than one primary invasive malignant melanoma or an invasive primary followed by an in situ melanoma were eligible for participation. RESULTS Individuals with MPM frequently had a family history of melanoma, dysplastic nevi (DN), and/or another cancer including basal cell carcinoma (BCC), and squamous cell carcinoma breast cancer, and a personal history of DN, and basal cell carcinoma. Germline mutations in CDKN2A gene were identified in 8 of 96 MPM cases (8.3%, 95% confidence interval, 6.7–9.9%). CONCLUSIONS These data indicate that the presence of MPM is associated with a modest incidence of a family history of melanoma, DN, or BCC and a small association with CDKN2A mutations. Therefore, in addition to the MPM index case, other family members can benefit from screening and regular surveillance for melanoma, DN, and BCC. Cancer 2002;94:2248–55. © 2002 American Cancer Society. DOI 10.1002/cncr.10454

These results suggest that at least half of breast/ovarian families evaluated in a high-risk cancer evaluation clinic may have germline mutations in BRCA1 or BRCA2. Whether the remaining families have mutations in noncoding regions in BRCA1, mutations in other, as-yet-unidentified, low-penetrance susceptibility genes, or represent chance clustering remains to be determined.