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Involvement of DNA repair in cancer and aging
1Molecular and Cell Biology Branch, NIA, Bethesda, MD 20892.
Abstract:
The theory of aging which proposes that DNA repair capacity declines with age and/or DNA damage accumulates with age, resulting in increasingly aberrant gene expression, is attractive but still unproven. Most results that do not support the theory are at least neutral. We propose that much of the ambiguity produced by work so far is due to (a) the difficulty of controlling all relevant variables, including particularly the proliferation state of the cells used and the location and nature of the damage being repaired, and (b) the existence of multiple and overlapping DNA repair pathways. A better knowledge of the critical, rate-limiting events in DNA repair in vivo, and the application of more sophisticated approaches for studying these events, may ultimately resolve the ambiguities. The causal relationship between DNA damage and cancer seems more secure. Declining DNA repair capacity with age would be expected to accelerate the increased incidence of cancer with age, but it is not known how important this is compared to other genetic and environmental variables. Results with genetic diseases generally support this view. Diseases characterized by DNA repair deficiencies are accompanied by phenomena that are also characteristic of normal aging, but a causal relationship has not been established. However, some of these diseases do constitute a strong risk factor for cancer. Even less convincing is a causal link between DNA repair deficiencies and aging in the so-called premature aging syndromes.
Insights
The theory that declining DNA repair capacity causes aging remains unproven due to complex variables. Further research into DNA repair mechanisms is needed to clarify its role in aging and cancer.
Area of Science:
- Genetics
- Molecular Biology
- Gerontology
Background:
- The theory linking aging to decreased DNA repair capacity and accumulated DNA damage is attractive but lacks definitive proof.
- Existing research presents ambiguous results, potentially due to challenges in controlling cellular proliferation, damage type/location, and the complexity of multiple DNA repair pathways.
Purpose of the Study:
- To address the ambiguities in the theory that declining DNA repair capacity contributes to aging.
- To explore the relationship between DNA damage, repair mechanisms, aging, and cancer incidence.
Main Methods:
- Review and analysis of existing research on DNA repair and aging.
- Discussion of methodological challenges in studying DNA repair in vivo.
- Consideration of evidence from genetic diseases and premature aging syndromes.
Main Results:
- The causal link between aging and declining DNA repair capacity is not definitively established.
- The relationship between DNA damage accumulation and cancer incidence appears more robust.
- Genetic diseases with DNA repair deficiencies share aging-like characteristics, but causality is unproven.
Conclusions:
- Resolving ambiguities in DNA repair research requires a better understanding of critical, rate-limiting events and advanced study approaches.
- While declining DNA repair may influence cancer risk with age, its precise contribution relative to other factors is unknown.
- A causal link between DNA repair deficiencies and premature aging syndromes is less convincing.