A recent study published in Nature Genetics has made a significant impact in the scientific community by demonstrating that certain chemotherapeutic agents, while effective at combating cancer, can leave permanent genetic scars in healthy cells of the human body, particularly in blood stem cells. These damages are not merely residual; in many cases, they represent an accelerated form of biological aging, as if those cells had lived through several decades within just weeks or months of treatment. This finding, led by scientists from the Wellcome Sanger Institute, Cambridge University Hospitals, and Great Ormond Street Hospital, is based on an exhaustive analysis of the genome of hematopoietic cells in patients previously treated with chemotherapy, compared to individuals with no such exposure, using state-of-the-art sequencing technology.

To conduct the study, the researchers recruited a total of 23 patients who had undergone cancer treatments, including chemotherapy with drugs such as cisplatin, carboplatin, oxaliplatin, melphalan, and other alkylating agents. The participants represented a wide age range—from three-year-old children to older adults—and had been treated for various cancer types, including both hematological and solid tumors. Peripheral blood samples were obtained from each patient, specifically to isolate hematopoietic stem cells and clonal progenitors. In parallel, a control group of nine individuals with no cancer history and no prior exposure to chemotherapy was included, and their blood cells were analyzed to establish a mutational reference profile.

The methodological core of the study relied on whole-genome sequencing (WGS) at the clonal level. This involved isolating individual blood stem cells through ex vivo expansion and culturing techniques, followed by deep genome sequencing of hundreds of cellular clones per patient. This approach enabled the researchers to detect somatic mutations with high precision, even those present at extremely low frequencies, and to reconstruct phylogenetic trees within the same patient to trace the mutational history of each cell back to its ancestral stem cell.

Once the genetic sequences were obtained, the team used advanced bioinformatics tools to identify mutational signatures, which are specific patterns of base substitutions or small insertions/deletions (indels) associated with defined molecular mechanisms. These signatures are well-characterized in the COSMIC (Catalogue Of Somatic Mutations In Cancer) database and can be linked to known mutagens, such as alkylating agents, ionizing radiation, homologous recombination repair defects, or replicative aging. For instance, cisplatin was shown to induce a high frequency of T>A and C>A substitutions in specific genomic contexts, along with short deletions of 1 to 10 base pairs, forming a mutational footprint characteristic of its cytotoxic mechanism.

The researchers also applied mathematical models of mutation accumulation to estimate the “biological age” of the analyzed cells. By comparing the total number of somatic mutations in patients’ stem cells with those from healthy individuals of known chronological age, they were able to infer that in some cases—notably a three-year-old child treated with cisplatin—the mutational burden was equivalent to that found in an 80-year-old adult with no treatment history. These estimates were not based on simple averages, but rather on Bayesian models of mutational rates adjusted by cellular lineage and estimated division rate, reinforcing the statistical robustness of the finding.

Another notable aspect of the study was the comparison between different chemotherapeutic drugs. The researchers found that although all the agents evaluated induced some degree of mutation, not all had the same impact on the genome of healthy cells. For example, oxaliplatin—also a platinum-based drug—produced significantly less genomic damage than cisplatin. This suggests that even small chemical differences between related compounds can result in vastly different levels of genotoxicity in non-tumor tissues. This observation has immediate clinical implications, as it could allow for the selection of less damaging therapeutic alternatives for certain patients without compromising oncologic efficacy.

To confirm that the mutations observed were not due to natural aging, chronic inflammation, or technical artifacts, the authors included several quality controls. They compared the mutational profiles with those from other public cohorts, including data from the UK’s 100,000 Genomes Project, and observed that chemotherapy-induced mutations formed a clearly distinct cluster. They also ruled out the possibility that the mutations came from residual tumor cells by confirming that the analyzed cells were immunophenotypically normal and lacked common oncogenic driver mutations.

Beyond the technical aspects, this study also highlights a functional and clinical dimension of therapy-induced aging. Senescence of hematopoietic stem cells not only reduces their renewal capacity but also disrupts immune homeostasis, promotes low-grade inflammation, and may predispose individuals to conditions like clonal anemia, marrow dysplasia, and late-onset immunodeficiency. These manifestations have already been reported in cohorts of childhood cancer survivors, and this study provides the first mechanistic explanation at the single-cell genomic level.

Figure 1. Intravenously administered chemotherapy circulates systemically and reaches the bone marrow, where it can induce DNA damage in hematopoietic stem cells (HSCs). This mutational injury compromises the regenerative capacity of the HSC pool, leading to reduced self-renewal, weakened immune function, and accelerated biological aging of the blood system.

The authors argue that these findings should be considered in future treatment decisions, especially for young patients with long life expectancies or those for whom less genotoxic alternatives exist. While chemotherapy remains a powerful and often irreplaceable tool, these insights call for a shift in focus—from simply eradicating tumors to a more holistic approach that preserves long-term health and vitality. They also propose that genetic or epigenetic biomarkers could be developed to identify patients most vulnerable to this type of damage, or that protective adjuvant drugs could be designed to shield healthy genomes during treatment.

This study represents a turning point in our understanding of the silent cost chemotherapy can impose on the body. It is no longer enough to survive cancer; more than ever, we must ask how our cells survive, with what invisible wounds they continue to function, and what can be done to ensure that cancer treatment not only saves lives but also preserves their full regenerative potential, longevity, and vitality.

Main Reference:

Mitchell, E., Pham, M. H., Clay, A., Sanghvi, R., Williams, N., Pietsch, S., Hsu, J. I., Jung, H., Vedi, A., Moody, S., Wang, J., Leonganmornlert, D., Spencer Chapman, M., Dunstone, E., Santarsieri, A., Cagan, A., Machado, H. E., Baxter, E. J., Follows, G., Hodson, D. J., … Stratton, M. R. (2025). The long-term effects of chemotherapy on normal blood cells. Nature genetics, 57(7), 1684–1694. https://doi.org/10.1038/s41588-025-02234-x

Other References:

DeVita, V. T., Jr, & Chu, E. (2008). A history of cancer chemotherapy. Cancer research, 68(21), 8643–8653. https://doi.org/10.1158/0008-5472.CAN-07-6611

Tilsed, C. M., Fisher, S. A., Nowak, A. K., Lake, R. A., & Lesterhuis, W. J. (2022). Cancer chemotherapy: insights into cellular and tumor microenvironmental mechanisms of action. Frontiers in oncology, 12, 960317. https://doi.org/10.3389/fonc.2022.960317

Kollmannsberger, C., Hartmann, J. T., Kanz, L., & Bokemeyer, C. (1998). Risk of secondary myeloid leukemia and myelodysplastic syndrome following standard-dose chemotherapy or high-dose chemotherapy with stem cell support in patients with potentially curable malignancies. Journal of cancer research and clinical oncology, 124(3-4), 207–214. https://doi.org/10.1007/s004320050156