Abstract LB101: <i>Tet2</i> deficiency mitigates epigenetic aging in clonal hematopoiesis

Abstract Aging is a process of systemic deterioration and the most significant risk factor for cancers. Clonal hematopoiesis (CH) commonly occurs with aging and links to higher mortality, leukemia risk, and cardiovascular diseases. Age-related CH involves the abnormal clonal expansion of hematopoietic stem cells (HSCs) bearing somatic mutations in genes frequently mutated in leukemia, including genes encoding epigenetic regulators, e.g., the DNA demethylase TET2. While such mutations are known to alter the HSC epigenome, the mechanisms through which these mutations drive HSC self-renewal and myeloid transformation preferentially in old age remain elusive. In this study, we hypothesize that aging and CH mutations cooperatively reshape the HSC transcriptomic landscape, enhancing HSC competitive advantage that facilitates clonal expansion. Using single-cell multi-omic analyses and flow cytometry for Mx1-cre mouse models, we demonstrated, for the first time, that Tet2 deficiency mitigates detrimental HSC aging processes at the transcriptomic, epigenomic, and cellular levels, thereby promoting age-dependent expansion. Age-related gene expression changes, including increased Eya4, Lars2, and Mical2 and decreased Cdk6, CD53, and Sox4, were mitigated in Tet2-deficient HSCs, with a log2 fold-change cutoff as 0.5 and FDR&amp;lt;20%. These gene expression changes were confirmed by single-nucleus ATAC-seq. Chromatin accessibility analysis also revealed Tet2 deficiency predominantly mitigates epigenetic changes associated with HSC aging. Specifically, age-related increase in chromatin accessibility of binding motifs of transcription factors (TFs), such as E2f4, Ppard, Mycn, and Max, and decrease in binding motifs of chromatin accessibility for Gabpa, Runx3, Etv4, and Elf1, were also mitigated in Tet2-deficient HSCs. Furthermore, DNA methylation status of these TF binding motifs is linked to the regulation for the targets’ gene expression, and CTCF insulator binding during HSC aging are also mitigated by Tet2 deficiency. Together, Tet2 deficiency stabilizes TF-target gene pairs critical for maintaining HSC self-renewal during aging. In conclusion, our findings reveal that Tet2 deficiency significantly contributes to the mitigation of HSC aging and hijacks the HSC expansion strategy during HSC aging via epigenetic reprogramming, which contributes to age-related CH. By elucidating the transcriptomic and epigenomic alterations in Tet2-deficient HSCs, our study provides novel insights into how age and somatic mutations interact to promote the pathogenesis of age-related hematological diseases. These discoveries enhance our understanding of how aging and somatic mutations interact, offering insights into potential biomarkers and therapeutic targets for age-associated hematological disorders. Citation Format: Shilpita Karmakar, Efthymios Motakis, Yang Liu, Kaustav Sengupta, Lamis Naddaf, Travis Roeder, Brandon Vu, Kristina Mujica, Ming Xu, Eric M. Pietras, James DeGregori, Jennifer J. Trowbridge, Hideyuki Oguro, Sheng Li. Tet2 deficiency mitigates epigenetic aging in clonal hematopoiesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB101.