Queen's University - Utility Bar

QSpace at Queen's University >
Theses, Dissertations & Graduate Projects >
Queen's Theses & Dissertations >

Please use this identifier to cite or link to this item: http://hdl.handle.net/1974/7521

Title: Characterization of Glucocorticoid Receptor Promoter Methylation in Breast Cancer
Authors: Nesset, Kirsten A.

Files in This Item:

File Description SizeFormat
Nesset_Kirsten_A_201209_MSc.pdf3.98 MBAdobe PDFView/Open
Keywords: glucocorticoid receptor
epigenetic
breast cancer
methylation
Issue Date: 26-Sep-2012
Series/Report no.: Canadian theses
Abstract: Epidemiological studies have identified psychological stress as a significant risk factor in breast cancer. The stress response is regulated by the HPA axis in the brain and is mediated by glucocorticoid receptor (GR) signalling. It has been found that early life events can affect epigenetic programming of GR, and methylation of the GR promoter has been reported in colorectal tumourigenesis. Decreased GR expression has also been observed in breast cancer. In addition, it has been previously demonstrated that unliganded GR can serve as a direct activator of the BRCA1 promoter in mammary epithelial cells. We propose a model whereby methylation of the GR promoter in the breast significantly lowers GR expression, resulting in insufficient BRCA1 promoter activation and an increased risk of developing cancer. Antibody-based methylated DNA enrichment was followed by qPCR analysis (MeDIP-qPCR) in a novel assay developed to detect locus-specific methylation levels. It was found that 13% of primary breast tumours were hypermethylated at the GR proximal promoter whereas no methylation was detected in normal tissue. RT-PCR and 5’ RACE analysis identified exon 1B as the predominant alternative first exon in the breast. Tumours methylated near exon 1B had decreased GR expression compared to unmethylated samples, suggesting that this region is important for transcriptional regulation of GR. It was also determined that GR and BRCA1 expression was decreased in breast tumour compared to normal tissue. Furthermore, the relative expression of GR and BRCA1 measured by qRT-PCR was correlated in normal tissue but this association was not found in tumour tissue. From this, it appears that lower GR levels with associated decreased BRCA1 expression in tissues may be a predisposing factor for breast cancer. Based on these results we propose a role for GR as a potential tumour suppressor gene in the breast due to its association with BRCA1, also a tumour suppressor gene, as well as its consistently decreased expression in breast tumours and methylation of its proximal promoter in a subset of cancer patients.
Description: Thesis (Master, Biochemistry) -- Queen's University, 2012-09-26 18:19:11.006
URI: http://hdl.handle.net/1974/7521
Appears in Collections:Biochemistry Graduate Theses
Queen's Theses & Dissertations

Items in QSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

  DSpace Software Copyright © 2002-2008  The DSpace Foundation - TOP