Age-dependent DNA methylation of genes that are suppressed in stem cells is a hallmark of cancer.
Level 4 - case-series / case-control
Cross-sectional human observational and retrospective genomic validation study (grade by design analogy).
PubMed 20219944 · doi:10.1101/gr.103606.109
What was done
Researchers measured DNA promoter methylation across >27,000 CpGs in ~14,000 genes using whole blood from a discovery cohort of 261 postmenopausal women. They assessed whether Polycomb group target genes (PCGTs)—which repress stem cell differentiation—preferentially acquire methylation with age. An age-hypermethylated PCGT signature was identified and tested across seven independent validation datasets comprising over 900 samples, including normal solid tissues, cancer tissues, and bone marrow mesenchymal stem/stromal cells.
What was found
Stem cell PCGTs were significantly more likely to become methylated with age than non-target genes (odds ratio = 5.3, 95% CI [3.8-7.4], P < 10^-10), independent of sex, tissue type, disease state, and platform. A core signature of 69 PCGT CpGs showed age-dependent hypermethylation and was validated across independent datasets (P < 10^-5). The signature was also present in preneoplastic conditions.
Why it matters
This study provides an epigenetic mechanism connecting chronological aging to carcinogenesis, showing that age-related DNA hypermethylation preferentially affects stem cell differentiation genes across multiple human tissues.
Limits
The discovery cohort was cross-sectional and limited to whole blood in postmenopausal women. The abstract does not report adjustment for age-related blood cell composition changes. Causal contribution of this methylation signature to malignant transformation is inferred from observational associations rather than prospectively or experimentally proven.
Cited by
- supports DNA methylation sites that gain methylation with aging are enriched in Polycomb group protein target sites.