DNA repair, aging, and cancer.

The ability of cells to repair UV damage to DNA is closely associated with a reduction in skin cancer incidence, and the quantitative epidemiological data indicate that proficient repair systems reduce cancer incidence by as much as 10,000-fold. The latter decrease corresponds to an equivalent reduction in UV dose of sevenfold to twentyfold. Older cells may accumulate DNA damage, but this accumulation does not seem to be the result of a deterioration of the repair systems studied to date. Although a correlation has been described between life-span and the proficiency of nucleotide excision repair and the association between cellular aging and decreasing repair is much weaker, no definitive data indicate whether these relations are causal ones.