Abstract B50: Promoter methylation of the BRCA1 gene in young breast cancer patients with no significant family history

Abstract

Abstract Background: Premenopausal breast cancer represents < 25% of all breast cancers, and only 5–10% of all breast cancer can be attributed to mutations in BRCA1/2 genes. Therefore, 90–95% of premenopausal patients may have a sporadic form of breast cancer. Although these women do not have germline mutations in the BRCA genes, it is possible that epigenetic modifications which lead to BRCA gene silencing may play a role in these sporadic cases. Previous research has identified epigenetic changes in the BRCA1 gene in as many as 10–20% of sporadic cases (1). More recently, other investigators used peripheral blood cells (PBC) to evaluate the presence of somatic methylation of the BRCA1 promoter and suggested that promoter methylation in normal PBC can be identified and correlated with development of triple negative breast cancer. However, currently the presence and rate of BRCA1 promoter methylation is not well described in subsets of breast cancer. Therefore, in this current study our aim was to examine PBC of premenopausal breast cancer patients diagnosed at or under 40 who had no detectable BRCA1 mutations in an effort to correlate BRCA1 promoter methylation with premenopausal breast cancer development. Methods: 28 patients with a history of breast cancer or ductal carcinoma in situ (DCIS) who tested negative for a deleterious mutation in the BRCA1 gene were enrolled in the study. Median age was 36.5 (range 28–47). Twenty-two (78.6%) of the patients had a positive family history of breast and or ovarian cancer, other patients were tested for BRCA mutations on the basis of their young age. Three (10.71%) had DCIS, 2 (7.14%) had stage I, 14 (50%) had stage II, 7 (25%) stage III, and 2 (7.14%) stage IV breast cancer. The estrogen receptor (ER) was positive in 21 (75%) of the samples, progesterone receptor (PR) in 15 (53.56%) and Her-2/neu was positive (based on IHC scores of 2 or 3 +, or FISH +) in 15 (53.56%) of the patients. Four (14.29%) of the tumors were ER, PR, and Her-2/neu (triple) negative. At the time of sample collection, 7 patients (25%) were chemotherapy naive and 21 patients (75%) had received chemotherapy. DNA was extracted from PBC then subjected to bisulfite conversion (Invitrogen, MethylCode Bisulfite Conversion kit) and the promoter region was examined using methylation-specific PCR techniques (−157 to +57, +1 serving as transcription start site). Results: We observed that 3 out of 28 PBCs displayed BRCA1 promoter methylation. Promoter methylation did not correlate with any certain subgroups; however, the numbers of subjects are too small at this point. Conclusions: These preliminary results suggest that 10.7% of sporadic breast cancers have a somatic promoter methylation in the BRCA1 gene. This finding might be important for the development of this test in the assessment of breast cancer risk of women who have no deleterious BRCA1 mutations. Further studies are ongoing to evaluate these promoter methylations in women who are at increased risk for breast cancer. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B50.