While genomic instability is a hallmark of aging, and unrepaired or mutagenic double-strand breaks (DSBs) are established drivers, recent evidence suggests that even accurately repaired DSBs contribute to aging. Here, we focus on an intriguing study by Bantele et al. published in Science, which demonstrates that Cas9-induced DSB repair can induce persistent, heritable alterations in higher-order chromatin structure and function, termed "chromatin fatigue". These alterations, characterized by changes in chromatin topology and gene expression, persist long after DNA sequence restoration and are inherited through cell divisions. Crucially, they impair transcriptional responsiveness to physiological stimuli. This finding provides a novel mechanism for DNA damage-driven aging independent of mutations, potentially explaining age-related epigenetic dysfunction. The commentary also highlights key unresolved questions regarding the permanence, locus-specificity, and physiological impact of chromatin fatigue, and explores its interaction with age-related DNA repair decline. This striking molecular phenomenon challenges the notion that faithful repair ensures full functional restoration and opens avenues for future research into interventions against aging and other age-related diseases, such as cancer.

Genomic instability (GI), characterized by the progressive failure of mechanisms that maintain genome integrity, serves as a fundamental link between aging and cancer at the molecular level. It not only drives the aging process but also promotes tumorigenesis through multiple pathways: on one hand, GI can induce cellular senescence and create a pro-inflammatory and tissue remodeling microenvironment via the senescence-associated secretory phenotype; on the other hand, GI can bypass senescence, directly facilitating tumor progression through mechanisms such as aneuploidy, the expansion of pre-malignant clones, and chronic inflammation mediated by DNA damage-associated molecular patterns. The decline in physiological functions accompanying aging and the increased risk of cancer are closely associated with the accumulation of GI, while aging itself may exert anti-cancer effects through irreversible cell cycle arrest in specific contexts. Therefore, a thorough investigation of GI’s dual role in aging and cancer can help reveal the shared biological basis of both processes and provide new strategies for the precise prevention and treatment of age-related tumors.

Aging tissues accumulate DNA damage, while genome instability is a defining feature of cancer. Despite this shared foundation, DNA damage is still largely viewed as a transient lesion that is either faithfully repaired or converted into a mutation. New evidence challenges this binary view, indicating that DNA double-strand breaks (DSBs), even when accurately repaired at the sequence level, can leave durable and heritable alterations in chromatin organization and gene regulation. Accordingly, DSB repair restores DNA integrity but does not necessarily re-establish the original regulatory architecture. The biological consequences of such post-repair regulatory memory remain largely underappreciated, progressively contributing to age-associated tissue dysfunction while simultaneously creating permissive states for malignant transformation and therapy resistance. In this commentary, we argue that reframing DNA damage as a source of heritable regulatory change, rather than solely as a mutational event, reshapes our understanding of aging trajectories and cancer risk.