RARbeta P2 promoter methylation: Potential biomarker for use with breast Random Periareolar Fine Needle Aspiration in breast cancer risk assessment

Abstract

1014 Background: Methylation of RARbeta P2 promoter is hypothesized to be an important early event in mammary carcinogenesis. Random Periareolar Breast Fine Needle Aspiration (RPFNA) is a research technique developed to repeatedly sample mammary cells from the whole breast of asymptomatic high-risk subjects to assess both 1) breast cancer risk, and 2) response to chemoprevention [Fabian et al. JNCI, 2000; Fabian et al. Clinical Cancer Res., 2002]. Coupling RARbeta P2 promoter methylation to RPFNA has the potential to enhance the sensitivity and specificity of RPFNA and to further delineate breast cancer risk. Methods: The frequency of RARbeta P2 methylation was tested through methylation-specific-PCR (MS-PCR) in 1) tissue biopsy specimens from 17 low-risk, primary breast cancers with a five year patient clinical follow-up and 2) RPFNA samples performed in 21 subjects at increased risk of developing breast cancer. Risk was defined as either 1) 5 year Gail risk calculation > 1.7%, 2) prior biopsy exhibiting atypical hyperplasia, LCIS, DCIS, or 3) known BRCA1/2 mutation carrier. The presence of methylation in RPFNA was compared to the degree of cytologic abnormality as assessed by the Masood semiquantitative index score. Results: RARbeta P2 promoter methylation was present in 12/17 (71%) of the primary breast cancers. RARbeta P2 promoter methylation was present in 9/21 (43%) RPFNA aspirates. The presence of RARbeta methylation correlated with the severity of the mammary epithelial cell atypia seen in the RPFNA cytology. Conclusions: We detect the presence of RARbeta P2 methylation early in mammary carcinogenesis and its presence positively correlates with worsening degrees of mammary epithelial cell atypia (Masood score). These observations provide further support that presence of RARbeta P2 promoter methylation in RPFNA can contribute to assessment of breast cancer risk. No significant financial relationships to disclose.