Compounds in Some Foods May Cause DNA Damage

Certain foods have been found to contain compounds that activate the p53 tumor suppressor gene in a fashion similar to the p53 activation caused by DNA damage.

The p53 tumor suppressor is a cell's critical defender against genome damage from chemicals, viruses, or ionizing radiation. The p53 protein is normally found at low levels, but when DNA damage is sensed, p53 levels rise and initiate protective measures. The protein binds to many regulatory sites in the genome and triggers production of proteins that halt cell division until the damage is repaired, or if the damage is too severe, p53 initiates the process of apoptosis, which directs the cell to commit suicide, permanently removing the damage.

Cancer cells typically contain two types of mutations: mutations that cause uncontrolled growth and multiplication of cells, and other mutations that block the normal defenses that protect against unnatural growth. P53 is in this second category and mutations in the p53 gene contribute to about half of the cases of human cancer. In these mutants, normal p53 function is blocked, and the protein is unable to stop multiplication of the damaged cell. If the cell has other mutations that cause uncontrolled growth, it will develop into a tumor.

Investigators at Johns Hopkins University (Baltimore, MD, USA) applied a recently developed cellular biological assay to screen for p53-stimulating activity in selected foods and flavorings.

They reported in the May 2013 online edition of the journal Food and Chemical Toxicology that following exposure of human cell cultures to different foods or flavorings they had found potent p53-stimulating activity in dietary concentrations of tea, coffee, and liquid smoke. Breaks in double-stranded DNA were confirmed by the comet assay. Pyrogallol-related chemicals and tannins are present in dietary sources, and these compounds were shown to individually produce strong p53-stimulating activity: pyrogallol (30-fold increase), 3-methoxycatechol (25-fold increase), gallic acid (21-fold increase), and 1,2,4-benzenetriol (21-fold increase).

Other flavorings such as fish and oyster sauces, Tabasco and soy sauces, black bean sauces, soybean paste, kimchee, wasabi powder, hickory smoke powders, and smoked paprika showed minimal p53-stimulatory effects.

"We found that Scotch whiskey, which has a smoky flavor and could be a substitute for liquid smoke, had minimal effect on p53 activity in our tests," said senior author Dr. Scott Kern, professor of oncology and pathology at Johns Hopkins University.

"We do not know much about the foods we eat and how they affect cells in our bodies," said Dr. Kern. "But it is clear that plants contain many compounds that are meant to deter humans and animals from eating them, like cellulose in stems and bitter-tasting tannins in leaves and beans we use to make teas and coffees, and their impact needs to be assessed. More studies are needed to examine the type of DNA damage caused by pyrogallol and gallic acid, but there could be ways to remove the two chemicals from foods and flavorings."

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