Susan G Komen  
I've Been Diagnosed With Breast Cancer Someone I Know Was Diagnosed Share Your Story Join Us And Stay Informed Donate To End Breast Cancer
    Home > Research & Grants > Grants Program > Research Grants > Research Grants Awarded > Abstract

    Research Grants Awarded

    Brca1-Mediated Regulation Of Oxidative DNA Damage In Breast Cancer

    Grant Mechanism:
    Postdoctoral Fellowships

    Scientific Abstract:
    Breast cancer is a genetic disease in that it results from and is maintained by genomic instability. Genomic instability is due in part to the accumulation of mutations in tumor suppressor genes such as Breast Cancer Susceptibility Gene 1 (BRCA1). BRCA1-associated malignancies include hereditary breast cancers due to germline genetic mutations in BRCA1, sporadic breast cancers due to epigenetic silencing of BRCA1, and the basal-like subtype of breast cancer or ?triple negatives? (i.e. negative for expression of the estrogen, progesterone, and HER2 receptors), which have a similar gene expression profile and clinical outcome to cancers with mutations in BRCA1. Together, these malignancies are often associated with an aggressive phenotype and comprise 30-50% of all breast cancer cases. The underlying mechanisms that contribute to the initiation and progression of these cancers are poorly understood, but remain important for developing more effective strategies for prevention and/or treatment. Oxidative DNA damage (ODD) leads to mutagenesis and genetic instability. In addition, we recently found that cells deficient for BRCA1 or harboring the basal-like phenotype exhibited more ODD than control cells. Therefore, we hypothesize that BRCA1 can prevent and/or repair ODD, and that breast cancer cells with BRCA1 aberrations or the basal-like phenotype exhibit an impaired defense mechanism against oxidative stress. We will address the following specific aims: (1) analyze the ability of BRCA1 to prevent reactive oxygen species (ROS)-mediated induction of oxidative DNA damage, (2) analyze the ability of BRCA1 to repair ODD through base excision repair, and (3) compare the mechanisms of regulating ODD between BRCA1-mutated breast cancer cells and basal-like breast cancer cells. To examine a role for BRCA1 in preventing ODD, we will first use isogenic cell lines for BRCA1 to determine whether BRCA1 can induce antioxidant activity and diminish ROS levels. We will also use these cell lines to determine whether BRCA1 can activate MTH1, an enzyme that degrades oxidatively-damaged nucleotides within the nucleotide pool to prevent their incorporation into DNA. To examine a role for BRCA1 in repairing ODD, we will determine the effect of BRCA1 on base excision repair using two different assays, host-cell reactivation and the alkaline comet assay. The combination of these assays will provide an in vivo and in vitro analysis of the overall activity and rate of base excision repair in the nucleus. Third, we will examine the ability to prevent and repair ODD in BRCA1-mutated breast cancer cell lines, and compare this ability to that of basal-like breast cancer cell lines, as well as other breast cancer and normal-like breast cell lines. Finally, we will determine whether the response to oxidative stress in basal-like breast cancer cells correlates with ODD levels. Overall, this proposal is aimed to better understand the mechanisms of regulating ODD that may contribute to the initiation and progression of cancers with BRCA1 mutations or a related phenotype.

    Lay Abstract:
    Breast cancer is a disease that results from and is maintained by abnormalities in our genetic material. These abnormalities are due in part to the accumulation of mutations in important cancer regulatory genes such as Breast Cancer Susceptibility Gene 1 (BRCA1). BRCA1-associated malignancies include hereditary breast cancers due to mutations in BRCA1 acquired at birth by one of our parents, sporadic breast cancers due to decreased levels of BRCA1 by other mechanisms, and the basal-like subtype of breast cancer or ?triple negatives? (i.e. negative for expression of the estrogen, progesterone, and HER2 receptors), which are similar to the former at the molecular and cellular level. Together, these cancers have a poor clinical outcome and comprise 30-50% of all breast cancer cases. The underlying mechanisms that contribute to the initiation and progression of these cancers are poorly understood, but remain important for developing more effective strategies for prevention and/or treatment. Damage to our genetic material by oxidative stress, which is termed oxidative DNA damage (ODD), leads to mutations and other abnormalities in our genetic material. In addition, we recently found that cells deficient for BRCA1 or harboring the basal-like phenotype have high levels of ODD. Therefore, we hypothesize that BRCA1 can prevent and/or repair ODD, and that breast cancer cells with BRCA1 aberrations or the basal-like phenotype exhibit an impaired defense mechanism against oxidative stress. The goals of this project are : (1) to analyze the ability of BRCA1 to prevent ODD from occurring, (2) to analyze the ability of BRCA1 to repair ODD that has evaded attempts of prevention, and (3) compare the ability to correct and repair ODD between BRCA1-mutated breast cancer cells and basal-like breast cancer cells. To examine a role for BRCA1 in preventing ODD, we will determine whether BRCA1 can remove potential sources of ODD. To examine a role for BRCA1 in repairing ODD, we will determine the effect of BRCA1 on the cells ability to remove ODD from our genetic material. We will then examine the ability to prevent and repair ODD in BRCA1-mutated breast cancer cells, and compare this ability to that of basal-like breast cancer cells, as well as other breast cancer and normal-like breast cells. Finally, we will determine levels of ODD in basal-like breast cancer cells. Overall, this proposal is aimed to understand the mechanisms of regulating ODD that may contribute to the initiation and progression of cancers with BRCA1 mutations or a related phenotype.