Abstract 4928: 14-3-3ζ-mediated hypomethylation of c-myc oncogene by downregulation of Dnmts contributes to initiation and progression of breast cancer

Abstract

Abstract The development of breast cancer is a multistep process and the molecular mechanisms underlying this process are still elusive. Previously, we discovered that 14-3-3ζ overexpression not only contribute to breast cancer progression but also play an important role in breast cancer initiation, including an early stage of breast disease-atypical ductal hyperplasia (ADH). However, the underlying mechanisms remain unclear. Recently, 14-3-3ζ has been shown to bind to Histone H3, Methylation Binding Proteins (MBPs) and HDAC family members, suggesting 14-3-3ζ may play a role in epigenetic regulation. As an initial effort to investigate whether 14-3-3ζ has a role in epigenetic regulation and whether epigenetic regulation by 14-3-3ζ plays a role in breast cancer initiation, we established 14-3-3ζ stable overexpressing lines (10A.14-3-3ζ) in non-tumorigenic MCF10A human mammary epithelial cells (HMEC) and analyzed molecular alterations by cDNA microarray in the 10A.14-3-3ζ cells versus the 10A.vec control cells in a 3D culture system. Interestingly, we found that c-myc, a well known oncogene which is overexpressed in many types of cancer, was upregulated at the mRNA level in the 10A.14-3-3ζ cells versus the 10A.vec cells. We further confirmed c-Myc upregulation at both mRNA level by RT-PCR and protein level by Western Blotting. Additionally, we performed Reverse Phase Protein Array (RPPA) analysis with a series of validated antibodies, and we found that Dnmt1, the key DNA methyltransferase in mammals, was downregulated in 10A.14-3-3ζ cells compared to 10A.vec cells. We have confirmed Dnmt1 downregulation by western blotting. Since c-myc oncogene are well known to be upregulated by hypomethylation as a consequence of Dnmt1 downregulation, these data suggest that 14-3-3ζ may contribute to breast cancer initiation and progression by upregulation of oncogene c-myc via promoter hypomethylation. We will continue this study to provide a better understanding on how 14-3-3ζ contributes to breast cancer initiation and progression via epigenetic deregulation (demethylation) of c-myc. This study will bring insight into how 14-3-3ζ overexpression elicits the phenotypic changes during the development of breast carcinomas through global deregulation of transcriptome as well as specific gene expressions. Our studies could provide a better understanding of the role of 14-3-3ζ in breast cancer initiation and progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4928.