Abstract 85: Detection of promoter methylation of tumor supressor genes in serum DNA of breast cancer patients and controls

Abstract

Abstract Background: Changes in DNA methylation patterns are a common feature of malignant cells. Methylation is an epigenetic change that affects gene expression. Methylation of a cytosine guanine dinucleotide-rich area (CpG island) of the promoter region of a gene that is normally unmethylated is correlated with silencing of that gene. Certain tumor suppressor genes are hypermethylated in breast tumor tissue and rarely methylated in normal breast tissue. Circulating serum DNA, presumably including DNA shed from the tumor, can be tested for promoter hypermethylation. Breast cancer detection with moderate sensitivity has been achieved in several small studies relying on a few genes and suggests that assaying methylation levels in a larger panel of genes might result in a useful serum marker for breast cancer detection. Methods: Bisulfite-modified serum DNA was evaluated for promoter methylation via pyrosequencing in 12 candidate tumor suppressor genes (GSTP1, SRFP1, RAR-beta, ER1, TWIST, HIN1, APC, ECAD, p16, BRAC1, CyclinD2, RASSF1). Study subjects included approximately 250 node-positive postmenopausal breast cancer cases, 75 node negative postmenopausal breast cancer cases and a comparison group of 250 postmenopausal women with benign breast disease types not strongly associated with breast cancer, all of whom donated blood at the time of diagnosis to the Mayo Serum Bank, a resource established in the 1970's to identify early markers of breast cancer. Results: As hypothesized, mean percent levels of serum DNA methylation were modestly but statistically higher in node-positive breast cancer cases than controls for TWIST (4.9% vs 3.9%; p-value =.002), CyclinD2 (3.2% vs 2.1%; p=.03), and HIN1 (3.9% vs 2.4%; p=.03). In the nine other genes, percent methylation levels were also moderately higher in node-positive cases than controls but did not reach statistical significance (e.g., SRFP1 [6.3% vs 4.3%; p=.06]). For TWIST, Cyclin D2, HIN1, mean percent levels were intermediate in node-negative patients compared to node-positive cases and controls. Additional analyses evaluating the predictive ability of multivariate sets of DNA methylation markers together with established breast cancer risk factors are underway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 85. doi:10.1158/1538-7445.AM2011-85