Role of Oxidative DNA Damage to Breast Tumor Progression
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: A classic theory of carcinogenesis proposes that DNA is damaged by environmental factors, which lead to mutations in the DNA code. Once enough mutations accumulate, cells can no longer function properly, and cancer arises. The facts that smoking causes lung cancer, and that sunlight exposure causes skin cancer support this theory. However, such a direct environmental link is not evident for breast cancer in humans. A more contemporary theory suggests that-the metabolism of oxygen produces free radicals, such as hydrogen peroxide, and these cause carcinogenic DNA damage. In order to validate the latter theory, it is necessary to measure the products of free radical damage in cells. Damage to cells caused by reactive oxygen species is called oxidation. 
 
 
 
 
 
 
 
 In some breast cancers, increased levels of oxidative DNA damage have been associated with tumor progression. However, the most commonly used marker of DNA oxidation, called 8-oxoG, is known to be chemically unstable, and is difficult to measure accurately. Importantly, 8-oxoG is itself easily oxidized to form several secondary oxidation products. Recently, I have determined that these secondary products are chemically stable, and that they are highly mutagenic. However, the products have not been studied in breast cancer, since they are difficult to detect with current technology. Thus, I propose to develop new technology that will allow detection of the 8-oxoG oxidation products in rat and human breast cancer cells. 
 
 
 
 
 
 
 
 We will chemically synthesize a radioactively labeled DNA building block, which can be tested in model cell and animal models as a “surrogate marker” to measure oxidative DNA damage. The radioactive label is easy to detect, and will allow very low concentrations of DNA damage to be assayed. The building block will be introduced to breast cancer cells, which will incorporate it into new DNA during tumor growth. We expect that the radioactive building block will be damaged by free radicals inside the cancer cell, and that the DNA damage products will contribute to the progression of the cancer. After isolation of DNA from the cells, the radioactive label will be used to determine how much of the building block has been incorporated into the cell, and to what extent the DNA of the cell is damaged. The technology will be developed using human breast cancer cells grown in cell culture, which are easy to handle. Then, as a model of human disease, breast cancer-prone rats will be fed the building block. At different times during breast cancer development in the rats, their breast tissue will be isolated and tested for oxidized DNA damage. The stable, radioactively-labeled biomarkers can be detected at remarkably low levels, which will allow the study of the typical, “real life” levels of DNA damage. Lawrence Livermore National Laboratory is a world leader in biological applications of radiolabel detection. 
 
 
 
 
 
 
 
 Such a novel DNA oxidative damage-based assay can be used as a foundation for making diagnostics for use in future human clinical and epidemiological studies. An additional benefit of these biomarkers will be their eventual application to chemoprevention of cancer.