Monday, February 11, 2008

Antioxidants and Cancer

A critical factor in mutagenesis is cell division. When the cell divides, an unrepaired DNA lesion can give rise to a mutation. Thus an important factor in mutagenesis, and therefore carcinogenesis, is the cell division rate in the precursors of tumor cells. Stem cells are important as precursor cells in cancer because they are not on their way to being discarded. Increasing their cell division rate would increase mutation. As expected, there is little cancer in non-dividing cells. Such diverse agents as chronic infection high levels of particular hormones, or chemicals at doses that cause cell death result in increased cell division and therefore an increased risk for cancer.

Oxidants form one important class of agents that stimulate cell division. This may be related to the stimulation of cell division that occurs during the inflammatory process accompanying wound healing. Antioxidants therefore can decrease mutagenesis, and thus carcinogenesis, in two ways:

by decreasing oxidative DNA damage and by decreasing cell division. Of great interest is the understanding of mechanisms by which tocopherol and carotenoids can prevent cell division

There is an increasing literature on the protective role of dietary tocopherol, ascorbate, and ß-carotene in lowering the incidence of a wide variety of human cancer.

Antioxidants can counteract the induction of cancer in rodents by a variety of carcinogens. Two of the major causes of cancer, cigarette smoke and chronic inflammation, both appear to involve oxidants in their mechanism of action.

Almost all of the epidemiological studies that examined the relation between Antioxidant levels and cigarette-induced lung cancer showed a statistically significant protective effect of Antioxidants.

Antioxidants inhibit much of the pathology of cigarette smoke in rodents.

Inflammatory reactions release large amounts of NO, a radical, nitrosating agent, and indirect mutagenic oxidant. Ascorbate inhibits nitrosation under physiological conditions.

Antioxidants help to protect against the carcinogenic effects of chronic inflammation, as discussed above.

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