The goal of this project is to determine if decreased expression of ATM, a well characterized tumor suppressor important in the maintenance of genome integrity, occurs in breast cancer. Epidemiologic studies on ATM heterozygotes determined that these individuals display an elevated risk for breast cancer, presumably due to decreased ATM abundance. However, whether reduced ATM expression is a factor in sporadic breast cancer is currently unresolved. We have recently shown that aberrant methylation of CpG dinucleotides within the proximal promoter region of the ATM gene gives rise to dramatic downregulation of ATM expression and phenotypic consequences associated with reduced ATM abundance (e.g., increased radiosensitivity). Aberrant promoter methylation, a phenomenon termed epigenetic silencing, leads to decreased expression of numerous tumor suppressors in breast and other cancers. Based on our findings, we hypothesize that ATM is a novel target for epigenetic silencing in breast cancer. We will examine this hypothesis by addressing the following aims: 1) We will test our hypothesis that breast cancer cell lines exhibit diminished ATM expression due to aberrant ATM promoter methylation. This hypothesis will be examined by determining: a) relative ATM protein abundance in an extensive panel of cultured breast tumor lines by immunoblotting; b) relative ATM mRNA abundance in cell lines displaying reduced ATM protein expression by quantitative, real-time PCR; c) methylation status of the ATM promoter in cell lines showing reduced ATM protein and mRNA expression using a variety of approaches to that score methylation in genomic DNA. 2) We will test our hypothesis that surgically obtained breast adenocarcinomas exhibit diminished ATM expression due to aberrant ATM promoter methylation. We will test this hypothesis by determining: a) relative ATM mRNA abundance in breast tumors by real-time PCR; b) methylation of status of the ATM promoter in malignant cells showing reduced ATM expression. Completion of this research program will result in a greater understanding of the occurrence of decreased ATM expression in breast cancer, and whether this event can be used as a prognostic marker in this disease. Because reduced ATM expression renders cells more sensitive to the cytotoxic effects of ionizing radiation, these studies could prove useful in predicting the effectiveness of radiotherapy.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21CA102220-02
Application #
6771169
Study Section
Metabolic Pathology Study Section (MEP)
Program Officer
Kim, Kelly Y
Project Start
2003-07-03
Project End
2004-07-31
Budget Start
2004-07-01
Budget End
2004-07-31
Support Year
2
Fiscal Year
2004
Total Cost
$11,833
Indirect Cost
Name
Louisiana State University Hsc New Orleans
Department
Biochemistry
Type
Schools of Medicine
DUNS #
782627814
City
New Orleans
State
LA
Country
United States
Zip Code
70112
Demircan, Berna; Dyer, Lisa M; Gerace, Mallory et al. (2009) Comparative epigenomics of human and mouse mammary tumors. Genes Chromosomes Cancer 48:83-97
Ai, Lingbao; Kim, Wan-Ju; Demircan, Berna et al. (2008) The transglutaminase 2 gene (TGM2), a potential molecular marker for chemotherapeutic drug sensitivity, is epigenetically silenced in breast cancer. Carcinogenesis 29:510-8
Ai, Lingbao; Tao, Qian; Zhong, Sheng et al. (2006) Inactivation of Wnt inhibitory factor-1 (WIF1) expression by epigenetic silencing is a common event in breast cancer. Carcinogenesis 27:1341-8
Ai, Lingbao; Kim, Wan-Ju; Kim, Tae-You et al. (2006) Epigenetic silencing of the tumor suppressor cystatin M occurs during breast cancer progression. Cancer Res 66:7899-909
Bolt, Jennifer; Vo, Quynh N; Kim, Wan-Ju et al. (2005) The ATM/p53 pathway is commonly targeted for inactivation in squamous cell carcinoma of the head and neck (SCCHN) by multiple molecular mechanisms. Oral Oncol 41:1013-20
Ai, Lingbao; Vo, Quynh N; Zuo, Chunlai et al. (2004) Ataxia-telangiectasia-mutated (ATM) gene in head and neck squamous cell carcinoma: promoter hypermethylation with clinical correlation in 100 cases. Cancer Epidemiol Biomarkers Prev 13:150-6