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BACKGROUND: Clonal hematopoiesis of indeterminate potential (CHIP)–the age-related clonal expansion of blood stem cells with leukemia-associated mutations–is a novel cardiovascular risk factor. Whether CHIP remains prognostic in individuals with established atherosclerotic cardiovascular disease (ASCVD) is less clear. OBJECTIVES: This study tested whether CHIP predicts adverse outcomes in individuals with established ASCVD. METHODS: Individuals aged 40 to 70 years from the UK Biobank with established ASCVD and available whole-exome sequences were analyzed. The primary outcome was a composite of ASCVD events and all-cause mortality. Associations of any CHIP (variant allele fraction ≥2%), large CHIP clones (variant allele fraction ≥10%), and the most commonly mutated driver genes (DNMT3A, TET2, ASXL1, JAK2, PPM1D/TP53 [DNA damage repair genes], and SF3B1/SRSF2/U2AF1 [spliceosome genes]) with incident outcomes were compared using unadjusted and multivariable-adjusted Cox regression. RESULTS: Of 13,129 individuals (median age: 63 years) included, 665 (5.1%) had CHIP. Over a median follow-up of 10.8 years, any CHIP and large CHIP at baseline were associated with adjusted HRs of 1.23 (95% CI: 1.10-1.38; P < 0.001) and 1.34 (95% CI: 1.17-1.53; P < 0.001), respectively, for the primary outcome. TET2 and spliceosome CHIP, especially large clones, were most strongly associated with adverse outcomes (large TET2 CHIP: HR: 1.89; 95% CI: 1.40-2.55; P

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Clonal hematopoiesis results from somatic mutations in cancer driver genes in hematopoietic stem cells. We sought to identify novel drivers of clonal expansion using an unbiased analysis of sequencing data from 84,683 persons and identified common mutations in the 5-methylcytosine reader ZBTB33 as well as in YLPM1, SRCAP, and ZNF318. We also identified these mutations at low frequency in patients with myelodysplastic syndrome. Zbtb33-edited mouse hematopoietic stem and progenitor cells exhibited a competitive advantage in vivo and increased genome-wide intron retention. ZBTB33 mutations potentially link DNA methylation and RNA splicing, the two most commonly mutated pathways in clonal hematopoiesis and myelodysplastic syndromes.Significance:Mutations in known driver genes can be found in only about half of individuals with clonal hematopoiesis. Here, we performed a somatic mutation discovery effort in nonmalignant blood samples, which identified novel candidate genes that may play biological roles in hematopoietic stem cell expansion and hematologic malignancies.This article is highlighted in the In This Issue feature, p. 403

Background:Coronary artery disease is an incurable, life-threatening disease that was once considered primarily a disorder of lipid deposition. Coronary artery disease is now also characterized by chronic inflammation‚ notable for the buildup of atherosclerotic plaques containing immune cells in various states of activation and differentiation. Understanding how these immune cells contribute to disease progression may lead to the development of novel therapeutic strategies.Methods:We used single-cell technology and in vitro assays to interrogate the immune microenvironment of human coronary atherosclerotic plaque at different stages of maturity.Results:In addition to macrophages, we found a high proportion of αβ T cells in the coronary plaques. Most of these T cells lack high expression ofCCR7andL-selectin, indicating that they are primarily antigen-experienced memory cells. Notably, nearly one-third of these cells express theHLA-DRAsurface marker, signifying activation through their TCRs (T-cell receptors). Consistent with this, TCR repertoire analysis confirmed the presence of activated αβ T cells (CD4HLA-DRA, 2 clusters expressed a proinflammatory and cytolytic signature characteristic of CD8 cells, while the other expressed AREG (amphiregulin), which promotes smooth muscle cell proliferation and fibrosis, and, thus, contributes to plaque progression.Conclusions:Taken together, these findings demonstrate that plaque T cells are clonally expanded potentially by antigen engagement, are potentially reactive to self-epitopes, and may interact with smooth muscle cells and macrophages in the plaque microenvironment.

Clonal hematopoiesis of indeterminate potential (CHIP) is a state in which somatic mutations in hematopoietic stem cells lead to clonal expansion of blood cells in individuals without hematologic malignancy. The mutated genes, including TET2, DNMT3A, ASXL1, TP53, JAK2, and SF3B1, are also recurrently mutated in myeloid malignancies. Individuals with CHIP have an increased risk of developing a hematologic cancer. Moreover, individuals with CHIP have an elevated risk of all-cause mortality that is significantly attributable to cardiovascular disease, independent of traditional risk factors. The mechanism for this increased risk is likely linked to increased inflammation driven by mutated macrophages, in part through inflammasome activation. This has broadened our understanding of how chronic diseases are influenced by CHIP and of the mechanistic role of inflammation in these disorders.

Background and Purpose: Clonal hematopoiesis of indeterminate potential (CHIP) is a novel age-related risk factor for cardiovascular disease–related morbidity and mortality. The association of CHIP with risk of incident ischemic stroke was reported previously in an exploratory analysis including a small number of incident stroke cases without replication and lack of stroke subphenotyping. The purpose of this study was to discover whether CHIP is a risk factor for ischemic or hemorrhagic stroke. Methods: We utilized plasma genome sequence data of blood DNA to identify CHIP in 78 752 individuals from 8 prospective cohorts and biobanks. We then assessed the association of CHIP and commonly mutated individual CHIP driver genes ( DNMT3A , TET2 , and ASXL1 ) with any stroke, ischemic stroke, and hemorrhagic stroke. Results: CHIP was associated with an increased risk of total stroke (hazard ratio, 1.14 [95% CI, 1.03–1.27]; P =0.01) after adjustment for age, sex, and race. We observed associations with CHIP with risk of hemorrhagic stroke (hazard ratio, 1.24 [95% CI, 1.01–1.51]; P =0.04) and with small vessel ischemic stroke subtypes. In gene-specific association results, TET2 showed the strongest association with total stroke and ischemic stroke, whereas DMNT3A and TET2 were each associated with increased risk of hemorrhagic stroke. Conclusions: CHIP is associated with an increased risk of stroke, particularly with hemorrhagic and small vessel ischemic stroke. Future studies clarifying the relationship between CHIP and subtypes of stroke are needed.

The mechanistic link between the complex mutational landscape ofde novomethyltransferaseDNMT3Aand the pathology of acute myeloid leukemia (AML) has not been clearly elucidated so far. A recent discovery on the catalogue of DNMT3A-destabilizing mutations throughout theDNMT3Agene as well as the oligomerization-dependent catalytic property of DNMT3A prompted us to investigate the common effect of DNMT3A-destabilizing mutations (DNMT3AINS) on the genomewide methylation patterns of AML cells. In this study, we describe the characteristics ofDNMT3AINSAML methylomes through the comprehensive computational analyses on three independent AML cohorts. As a result, we show that methylomes ofDNMT3AINSAMLs are considerably different from those ofDNMT3AR882AMLs in that they exhibit both locally disordered DNA methylation states and increased across-cell DNA methylation heterogeneity in bivalent chromatin domains. This increased epigenetic heterogeneity was functionally associated with heterogeneous expression of membrane-associated factors shaping stem cell niche, implying the diversification of the modes of leukemic stem cell-niche interactions. We also present that the level of methylation disorder at bivalent domains predicts the response of AML cells to hypomethylating agents through cell line- and patient-level analyses, which supports that the survival of AML cells depends on stochastic DNA methylations at bivalent domains. Altogether, our work provides a novel mechanistic model suggesting the genomic origin of the aberrant epigenomic heterogeneity in disease conditions.

Clonal hematopoiesis of indeterminate potential (CHIP) is a common form of age-related somatic mosaicism that is associated with significant morbidity and mortality. CHIP mutations can be identified in peripheral blood samples sequenced using approaches that cover the whole genome, whole exome or targeted genetic regions; however, differentiating true CHIP mutations from sequencing artifacts and germline variants is a considerable bioinformatic challenge. We present a stepwise method that combines filtering based on sequencing metrics, variant annotation, and novel population-based associations to increase the accuracy of CHIP calls. We apply this approach to ascertain CHIP in ∼550,000 individuals in the UK Biobank complete whole exome cohort and the All of Us Research Program initial whole genome release cohort. CHIP ascertainment on this scale unmasks recurrent artifactual variants and highlights the importance of specialized filtering approaches for several genes includingTET2andASXL1. We show how small changes in filtering parameters can considerably increase CHIP misclassification and reduce the effect size of epidemiological associations. Our high-fidelity call set refines prior population-based associations of CHIP with incident outcomes. For example, the annualized incidence of myeloid malignancy in individuals with small CHIP clones is 0.03%/year, which increases to 0.5%/year amongst individuals with very large CHIP clones. We also find a significantly lower prevalence of CHIP in individuals of self-reported Latino or Hispanic ethnicity in All of Us, highlighting the importance of including diverse populations. The standardization of CHIP calling will increase the fidelity of CHIP epidemiological work and is required for clinical CHIP diagnostic assays.

Clonal hematopoiesis of indeterminate potential (CHIP) is associated with an increased risk of cardiovascular diseases (CVD), putatively via inflammasome activation. We pursued an inflammatory gene modifier scan for CHIP-associated CVD risk among 424,651 UK Biobank participants. CHIP was identified using whole exome sequencing data of blood DNA and modeled both as a composite and for common drivers (DNMT3A, TET2, ASXL1, andJAK2) separately. We developed predicted gene expression scores for 26 inflammasome-related genes and assessed how they modify CHIP-associated CVD risk. We identifyIL1RAPas a potential key molecule for CHIP-associated CVD risk across genes and increasedAIM2gene expression leading to heightenedJAK2- andASXL1-associated CVD risks. We show that CRISPR-inducedAsxl1mutated murine macrophages have a particularly heightened inflammatory response to AIM2 agonism. Our study provides new evidence to support gene-specific strategies to address CHIP-associated CVD risk.

Aging is associated with increased mutational burden in every tissue studied. Occasionally, fitness-increasing mutations will arise, leading to stem cell clonal expansion. This process occurs in several tissues but has been best studied in blood. Clonal hematopoiesis is associated with an increased risk of blood cancers, such as acute myeloid leukemia, which result if additional cooperating mutations occur. Surprisingly, it is also associated with an increased risk of nonmalignant diseases, such as atherosclerotic cardiovascular disease. This may be due to enhanced inflammation in mutated innate immune cells, which could be targeted clinically with anti-inflammatory drugs. Recent studies have uncovered other factors that predict poor outcomes in patients with clonal hematopoiesis, such as size of the mutant clone, mutated driver genes, and epigenetic aging. Though clonality is inevitable and largely a function of time, recent work has shown that inherited genetic variation can also influence this process. Clonal hematopoiesis provides a paradigm for understanding how age-related changes in tissue stem cell composition and function influence human health. Expected final online publication date for the

Myeloid neoplasms and acute leukemias derive from the clonal expansion of hematopoietic cells driven by somatic gene mutations. Although assessment of morphology plays a crucial role in the diagnostic evaluation of patients with these malignancies, genomic characterization has become increasingly important for accurate diagnosis, risk assessment, and therapeutic decision making. Conventional cytogenetics, a comprehensive and unbiased method for assessing chromosomal abnormalities, has been the mainstay of genomic testing over the past several decades and remains relevant today. However, more recent advances in sequencing technology have increased our ability to detect somatic mutations through the use of targeted gene panels, whole-exome sequencing, whole-genome sequencing, and whole-transcriptome sequencing or RNA sequencing. In patients with myeloid neoplasms, whole-genome sequencing represents a potential replacement for both conventional cytogenetic and sequencing approaches, providing rapid and accurate comprehensive genomic profiling. DNA sequencing methods are used not only for detecting somatically acquired gene mutations but also for identifying germline gene mutations associated with inherited predisposition to hematologic neoplasms. The 2022 International Consensus Classification of myeloid neoplasms and acute leukemias makes extensive use of genomic data. The aim of this report is to help physicians and laboratorians implement genomic testing for diagnosis, risk stratification, and clinical decision making and illustrates the potential of genomic profiling for enabling personalized medicine in patients with hematologic neoplasms.

In the multi-hit model of carcinogenesis, a precancerous state often precedes overt malignancy. Identification of these states has been of great interest as they allow for early identification of at-risk individuals before the appearance of a future cancer. One such condition has recently been described for blood cancers: Clonal Hematopoiesis of Indeterminate Potential (CHIP). Recent research advances have elucidated the risk of progression of CHIP to myeloid malignancies, its potential as a precursor for non-myeloid blood cancers, and its association with non-hematological cancers. Understanding the evolution of CHIP to hematological malignancy may help identify CHIP carriers at high risk of transformation and lead to the development of targeted therapies that can be deployed preemptively.

Human genetic studies support an inverse causal relationship between leukocyte telomere length (LTL) and coronary artery disease (CAD), but directionally mixed effects for LTL and diverse malignancies. Clonal hematopoiesis of indeterminate potential (CHIP), characterized by expansion of hematopoietic cells bearing leukemogenic mutations, predisposes both hematologic malignancy and CAD. TERT (which encodes telomerase reverse transcriptase) is the most significantly associated germline locus for CHIP in genome-wide association studies. Here, we investigated the relationship between CHIP, LTL, and CAD in the Trans-Omics for Precision Medicine (TOPMed) program ( n = 63,302) and UK Biobank ( n = 47,080). Bidirectional Mendelian randomization studies were consistent with longer genetically imputed LTL increasing propensity to develop CHIP, but CHIP then, in turn, hastens to shorten measured LTL (mLTL). We also demonstrated evidence of modest mediation between CHIP and CAD by mLTL. Our data promote an understanding of potential causal relationships across CHIP and LTL toward prevention of CAD.

Gout is a common inflammatory arthritis caused by precipitation of monosodium urate (MSU) crystals in individuals with hyperuricemia. Acute flares are accompanied by secretion of proinflammatory cytokines, including interleukin-1β (IL-1β). Clonal hematopoiesis of indeterminate potential (CHIP) is an age-related condition predisposing to hematologic cancers and cardiovascular disease. CHIP is associated with elevated IL-1β, thus we investigated CHIP as a risk factor for gout. To test the clinical association between CHIP and gout, we analyzed whole exome sequencing data from 177 824 individuals in the MGB Biobank (MGBB) and UK Biobank (UKB). In both cohorts, the frequency of gout was higher among individuals with CHIP than without CHIP (MGBB, CHIP with variant allele fraction [VAF] ≥2%: odds ratio [OR], 1.69; 95% CI, 1.09-2.61; P = .0189; UKB, CHIP with VAF ≥10%: OR, 1.25; 95% CI, 1.05-1.50; P = .0133). Moreover, individuals with CHIP and a VAF ≥10% had an increased risk of incident gout (UKB: hazard ratio [HR], 1.28; 95% CI, 1.06-1.55; P = .0107). In murine models of gout pathogenesis, animals with Tet2 knockout hematopoietic cells had exaggerated IL-1β secretion and paw edema upon administration of MSU crystals. Tet2 knockout macrophages elaborated higher levels of IL-1β in response to MSU crystals in vitro, which was ameliorated through genetic and pharmacologic Nlrp3 inflammasome inhibition. These studies show that TET2-mutant CHIP is associated with an increased risk of gout in humans and that MSU crystals lead to elevated IL-1β levels in Tet2 knockout murine models. We identify CHIP as an amplifier of NLRP3-dependent inflammatory responses to MSU crystals in patients with gout.

Introduction: Clonal hematopoiesis of indeterminate potential (CHIP) is a newly recognized aging-related condition due to clonal expansion of mutated hematopoietic stem cells (HSC) that results in increased risk for coronary artery disease (CAD). The extent to which CHIP is associated with stroke risk is not well understood. Methods: CHIP genotypes were obtained from 6 cohort studies [the Atherosclerosis Risk in Communities Study (ARIC), the Cardiovascular Health Study (CHS), the Framingham Heart Study (FHS), the Jackson Heart Study (JHS), the Multi-Ethnic Study of Atherosclerosis (MESA), the Women’s Health Initiative (WHI)] and two electronic health record-based biobanks [UK Biobank (UKBB) and Massachusetts General Brigham Biobank (MGBB)]. Incident stroke was ascertained by physician adjudicators in the cohort studies, and by ICD codes in the biobanks. Cox proportional hazards models were fitted with adjustment for age, sex, diabetes mellitus, smoking status (never, past, current) and race. Fixed-effects meta-analysis was used to estimate pooled effect sizes. Results: A total of 74,306 participants from 8 studies were included. In the fixed-effects meta-analysis, CHIP mutations were associated with an increased risk of total stroke (HR= 1.17, 95% CI 1.05-1.28) ( Figure 1 ). In analysis of stroke subgroups, the risk was greater for hemorrhagic (HR= 1.37, 95% CI 1.15-1.59) than ischemic stroke (HR= 1.13, 95% CI 1.00-1.26). Individuals with particularly expanded CHIP mutations (i.e. variant allele fraction >10%), showed similar effect estimates of association for total stroke, ischemic stroke, or hemorrhagic stroke were observed (HR any stroke = 1.21, 95% CI 1.09-1.34; HR ischemic stroke = 1.15, 95% CI 1.01-1.30; HR hemorrhagic stroke = 1.43, 95% CI 1.20-1.67) . Conclusions: CHIP is associated with incident ischemic and hemorrhagic stroke.

Osteoporosis is caused by an imbalance of osteoclasts and osteoblasts, occurring in close proximity to hematopoietic cells in the bone marrow. Recurrent somatic mutations that lead to an expanded population of mutant blood cells is termed clonal hematopoiesis of indeterminate potential (CHIP). Analyzing exome sequencing data from the UK Biobank, we found CHIP to be associated with increased incident osteoporosis diagnoses and decreased bone mineral density. In murine models, hematopoietic-specific mutations in Dnmt3a, the most commonly mutated gene in CHIP, decreased bone mass via increased osteoclastogenesis. Dnmt3a−/− demethylation opened chromatin and altered activity of inflammatory transcription factors. Bone loss was driven by proinflammatory cytokines, including Irf3-NF-κB–mediated IL-20 expression from Dnmt3a mutant macrophages. Increased osteoclastogenesis due to the Dnmt3a mutations was ameliorated by alendronate or IL-20 neutralization. These results demonstrate a novel source of osteoporosis-inducing inflammation.

Clonal hematopoiesis results from somatic mutations in cancer driver genes in hematopoietic stem cells. We sought to identify novel drivers of clonal expansion using an unbiased analysis of sequencing data from 84,683 persons and identified common mutations in the 5-methylcytosine reader, ZBTB33, as well as in YLPM1, SRCAP, and ZNF318. We also identified these mutations at low frequency in myelodysplastic syndrome patients. Zbtb33 edited mouse hematopoietic stem and progenitor cells exhibited a competitive advantage in vivo and increased genome-wide intron retention. ZBTB33 mutations potentially link DNA methylation and RNA splicing, the two most commonly mutated pathways in clonal hematopoiesis and MDS.

Background Molecular and cellular changes are intrinsic to aging and age-related diseases. Prior cross-sectional studies have investigated the combined effects of age and genetics on gene expression and alternative splicing; however, there has been no long-term, longitudinal characterization of these molecular changes, especially in older age. Results We perform RNA sequencing in whole blood from the same individuals at ages 70 and 80 to quantify how gene expression, alternative splicing, and their genetic regulation are altered during this 10-year period of advanced aging at a population and individual level. We observe that individuals are more similar to their own expression profiles later in life than profiles of other individuals their own age. We identify 1291 and 294 genes differentially expressed and alternatively spliced with age, as well as 529 genes with outlying individual trajectories. Further, we observe a strong correlation of genetic effects on expression and splicing between the two ages, with a small subset of tested genes showing a reduction in genetic associations with expression and splicing in older age. Conclusions These findings demonstrate that, although the transcriptome and its genetic regulation is mostly stable late in life, a small subset of genes is dynamic and is characterized by a reduction in genetic regulation, most likely due to increasing environmental variance with age.

Adult hematological malignancies, such as acute myeloid leukemia, are thought to arise through the gradual acquisition of oncogenic mutations within long-lived hematopoietic stem cells (HSCs). Genomic analysis of peripheral blood DNA has recently identified leukemia-associated genetic mutations within otherwise healthy individuals, an observation that is strongly associated with age. These genetic mutations are often found at high frequency, suggesting dominance of a mutant HSC clone. Expansion of clones carrying other mutations not associated with leukemia or larger chromosomal deletions were also observed. This clinical observation has been termed clonal hematopoiesis, a condition associated with increased the risk of both hematological malignancy and cardiovascular disease. Here, we discuss the identification of clonal hematopoiesis and its implications on human health, based on the May 2019 International Society for Experimental Hematology New Investigator Committee Webinar.

A novel, common, and potent cardiovascular risk factor has recently emerged: clonal hematopoiesis of indeterminate potential (CHIP). CHIP arises from somatic mutations in hematopoietic stem cells that yield clonal progeny of mutant leukocytes in blood. Individuals with CHIP have a doubled risk of coronary heart disease and ischemic stroke, and worsened heart failure outcomes independent of traditional cardiovascular risk factors. The recognition of CHIP as a nontraditional risk factor challenges specialists in hematology/oncology and cardiovascular medicine alike. Should we screen for CHIP? If so, in whom? How should we assess cardiovascular risk in people with CHIP? How should we manage the excess cardiovascular risk in the absence of an evidence base? This review explains CHIP, explores the clinical quandaries, strives to provide reasonable recommendations for the multidisciplinary management of cardiovascular risk in individuals with CHIP, and highlights current knowledge gaps.

The incidence of cardiovascular diseases increases with age and is also correlated with increased inflammatory burden. Recently, human genetics provided a new paradigm linking aging, inflammation, and atherosclerotic cardiovascular disease (ASCVD). Next-generation genetic sequencing of whole blood-derived DNA in humans showed that clonal expansion of hematopoietic cells with somatic mutations in leukemogenic genes was associated with age and correlated with increased mortality. This phenomenon, termed clonal hematopoiesis of indeterminate potential (CHIP), was associated with hematologic malignancy as well as ASCVD independently of age and other traditional risk factors. Because the implication of CHIP with ASCVD, genetic loss-of-function studies of Tet2 and Dnmt3a in murine models have supported a mechanistic role for CHIP in promoting vascular disease. Despite the potential contribution of CHIP to myriad cardiovascular and aging-related diseases, the epidemiology and biology surrounding this phenomenon remains incompletely appreciated and understood, especially as applied to clinical practice and prognostication. Here, the authors review this emerging key risk factor, defining its discovery, relationship to cardiovascular diseases, preclinical evidence for causality, and implications for risk prediction and mitigation.

Clonal hematopoiesis of indeterminate potential (CHIP) is a common precursor state for blood cancers that most frequently occurs due to mutations in the DNA‐methylation modifying enzymes DNMT3A or TET2. We used DNA‐methylation array and whole‐genome sequencing data from four cohorts together comprising 5522 persons to study the association between CHIP, epigenetic clocks, and health outcomes. CHIP was strongly associated with epigenetic age acceleration, defined as the residual after regressing epigenetic clock age on chronological age, in several clocks, ranging from 1.31 years (GrimAge, p 0 in both Hannum and GrimAge (referred to as AgeAccelHG+). This group was at high risk of all‐cause mortality (hazard ratio 2.90, p, Clonal hematopoiesis of indeterminate potential (CHIP) and epigenetic age acceleration are the two important aging phenomenon associated with adverse clinical outcomes. We found that mutations in most CHIP genes were associated with increased age acceleration in multiple epigenetic clocks. Individuals with CHIP and age acceleration had a greatly increased risk of mortality and coronary heart disease compared to individuals with only CHIP or age acceleration.

Human genetic studies support an inverse causal relationship between leukocyte telomere length (LTL) and coronary artery disease (CAD), but directionally mixed effects for LTL and diverse malignancies. Clonal hematopoiesis of indeterminate potential (CHIP), characterized by expansion of hematopoietic cells bearing leukemogenic mutations, predisposes both hematologic malignancy and CAD. TERT (which encodes telomerase reverse transcriptase) is the most significantly associated germline locus for CHIP in genome-wide association studies. Here, we investigated the relationship between CHIP, LTL, and CAD in Trans-Omics for Precision Medicine (TOPMed) program (N=63,302) and UK Biobank (N=48,658). Bidirectional Mendelian randomization studies were consistent with LTL lengthening increasing propensity to develop CHIP, but CHIP then in turn hastening LTL shortening. We also demonstrated evidence of modest mediation between CHIP and CAD by LTL. Our data promote an understanding of potential causal relationships across CHIP and LTL toward prevention of CAD.

To review the most common forms of cardiovascular toxicities from anti-cancer drugs, with a focus on their prevention via cardioprotective pharmacologic or lifestyle therapy, risk factors management, screening, monitoring, and surveillance methods. There are almost 20 million cancer survivors in the USA, and their leading cause of death besides cancer recurrence or a secondary cancer is cardiovascular disease (CVD). CVD is prevalent in this population, with the most common forms being cardiomyopathy, ischemia, atrial fibrillation, and hypertension from cancer drugs or radiation therapy. The field of cardio-oncology is continuously evolving with multi-modality risk prediction strategies, moving towards precision surveillance and interventions that allow for safe continuation of life-saving chemotherapy. Preventative measures with implementation of novel drugs (including sodium-glucose cotransporter inhibitors) and modulated chemotherapy administration can aid in cardiotoxicity risk reduction. Recently, clonal hematopoiesis of indeterminate potential has been identified as a common risk factor for atherosclerotic cardiovascular disease present in > 10% of those age 70 or older. Also, risk stratification for atrial fibrillation appears pivotal. Multidisciplinary team management might have a central role in patient management and care. There is a central role for the optimization of cardiovascular disease risk for cancer patients and survivors in multidisciplinary teams, with descriptions of four forms of cardiovascular toxicities. In addition to pharmacologic cardioprotection, lifestyle modification is becoming more prominent as a preventive tool. Moreover, studies relevant to one type of toxicity should be scrutinized routinely to determine how those result may play out in the setting of other types of toxicities. All of these areas of investigation should ultimately be pursued in the setting of personalized medicine, and will likely benefit from the integration of artificial intelligence methods. Studies in genomics and transcriptomics have identified variations in the genome and gene expression profiles that associate with induction of or protection from cardiovascular toxicity and can affect cardioprotection efforts. Larger randomized clinical trials will be needed for all patients, with a focus on incorporation of ethnic minorities likely by intentional oversampling, to overcome decades of demographic homogeneity in the trials.

Age-related clonal hematopoiesis (CH) is a risk factor for malignancy, cardiovascular disease and all-cause mortality. Somatic mutations in DNMT3A are drivers of CH, but decades may elapse between acquisition of a mutation and CH, suggesting that environmental factors contribute to clonal expansion. We tested whether infection provides selective pressure favoring expansion of Dnmt3a-mutant hematopoietic stem cells (HSCs) in mouse chimeras. We created Dnmt3a-mosaic mice by transplanting Dnmt3a(−/−) and WT HSCs into WT mice and observed substantial expansion of Dnmt3a(−/−) HSCs during chronic mycobacterial infection. Injection of recombinant IFNγ alone was sufficient to phenocopy CH by Dnmt3a(−/−) HSCs upon infection. Transcriptional and epigenetic profiling and functional studies indicate reduced differentiation associated with widespread methylation alterations and reduced secondary stress-induced apoptosis account for Dnmt3a(−/−) clonal expansion during infection. DNMT3A-mutant human HSCs similarly exhibit defective IFNγ-induced differentiation. We thus demonstrate that IFNγ signaling induced during chronic infection can drive DNMT3A-loss of function CH.

Background: Clonal hematopoiesis of indeterminate potential (CHIP) occurs when there is expansion of leukocyte clones in the blood due to mutations in hematopoietic stem cells. CHIP is associated with a high risk of hematologic malignancy and increased risk of cardiovascular disease (CVD). Although the environmental risk factors for CHIP remain poorly understood, radon is a ubiquitous mutagen and may deliver non-negligible doses of α-radiation to bone marrow that trigger CHIP development. Methods: We conducted a cross-sectional study of 10,495 postmenopausal women without hematologic malignancy from the Women’s Health Initiative clinical trials and observational study (mean age: 69 years; 82% white; 9% African American; 4% Hispanic/Latina; 3% Asian). Using blood from the 1993-1998 screening visit or a subsequent annual visit, and whole genome sequence data from the Trans-Omics for Precision Medicine project, we identified CHIP using the GATK Mu TECT2 somatic variant caller, a pre-specified list of leukemogenic driver mutations in 74 genes, and a threshold variant allele fraction > 0.02. We linked geocoded participant addresses at the time of blood draw to county-level, indoor, screening radon concentrations that were predicted by the Environmental Protection Agency (EPA) in 1993 using data on indoor radon, geology, aerial radioactivity, soil parameters, and foundation types. Radon exposure was classified as follows: Zone 3 (< 2 pCi/L), Zone 2 (2-4 pCi/L), and Zone 1 (> 4 pCi/L), the level at which EPA recommends remediation. We estimated the radon-related risk of CHIP as an odds ratio (OR, 95% CI) using logistic regression with and without adjustment for study design, participant sampling, age, race/ethnicity, smoking, and other sociodemographic / behavioral covariates. Results: We identified CHIP in 887 (8.5% of) participants. 3106 (29.6%), 3982 (37.9%), and 3407 (32.5%) had Zone 3, 2, and 1 radon exposures. The corresponding percentage of participants with CHIP across zones was 7.6%, 8.6%, and 9.1%. Relative to participants in Zone 3, those in Zones 2 and 1 had a higher adjusted risk of CHIP: OR (95% CI) = 1.13 (0.95, 1.35) and 1.24 (1.03, 1.48). Conclusion: Risk of CHIP was positively associated with indoor radon concentrations in this cross-sectional study of post-menopausal women. Longitudinal study of temporally integrated, in-home radon exposures, incident CHIP, and CVD would help confirm this novel radon-CHIP association and place it in context.

Truncating mutations in the terminal exon of protein phosphatase Mg2+/Mn2+ 1D (PPM1D) have been identified in clonal hematopoiesis and myeloid neoplasms, with a striking enrichment in patients previously exposed to chemotherapy. In this study, we demonstrate that truncating PPM1D mutations confer a chemoresistance phenotype, resulting in the selective expansion of PPM1D-mutant hematopoietic cells in the presence of chemotherapy in vitro and in vivo. Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease mutational profiling of PPM1D in the presence of chemotherapy selected for the same exon 6 mutations identified in patient samples. These exon 6 mutations encode for a truncated protein that displays elevated expression and activity due to loss of a C-terminal degradation domain. Global phosphoproteomic profiling revealed altered phosphorylation of target proteins in the presence of the mutation, highlighting multiple pathways including the DNA damage response (DDR). In the presence of chemotherapy, PPM1D-mutant cells have an abrogated DDR resulting in altered cell cycle progression, decreased apoptosis, and reduced mitochondrial priming. We demonstrate that treatment with an allosteric, small molecule inhibitor of PPM1D reverts the phosphoproteomic, DDR, apoptotic, and mitochondrial priming changes observed in PPM1D-mutant cells. Finally, we show that the inhibitor preferentially kills PPM1D-mutant cells, sensitizes the cells to chemotherapy, and reverses the chemoresistance phenotype. These results provide an explanation for the enrichment of truncating PPM1D mutations in the blood of patients exposed to chemotherapy and in therapy-related myeloid neoplasms, and demonstrate that PPM1D can be a targeted in the prevention of clonal expansion of PPM1D-mutant cells and the treatment of PPM1D-mutant disease.

Clonal expansions of mutated hematopoietic cells, termed clonal hematopoiesis, are common in aging humans. One expected consequence of mutation-associated clonal hematopoiesis is an increased risk of hematologic cancers, which has now been shown in several studies. However, the hematopoietic stem cells that acquire these somatic mutations also give rise to mutated immune effector cells, such as monocytes, granulocytes, and lymphocytes. These effector cells can potentially influence many disease states, especially those with a chronic inflammatory component. Indeed, several studies have now shown that clonal hematopoiesis associates with increased risk of atherosclerotic cardiovascular disease. Emerging data also associate clonal hematopoiesis to other non-hematologic diseases. Here, we will review recent studies linking clonal hematopoiesis to altered immune function, inflammation, and non-malignant diseases of aging.

Introduction: Clonal hematopoiesis of indeterminate potential (CHIP) may occur when a hematopoietic stem cell (HSC) acquires a fitness-increasing mutation resulting in its clonal expansion. A diverse set of driver genes, such as regulators of DNA methylation, splicing, and chromatin remodeling, have been associated with CHIP, but it remains largely unknown why HSCs bearing these mutations are positively selected. It has been challenging to identify the genetic and environmental factors mediating clonal expansion in humans, partially due to a lack of large cohorts with longitudinal blood sampling of participants. To circumvent this limitation, we developed a method to infer clonal expansion rate from single timepoint data called PACER (passenger-approximated clonal expansion rate). Methods: PACER is based on the principle that genomic passenger mutations can be used to infer the birth date of pre-malignant clones because these mutations accumulate fairly linearly over time. Thus, an individual with CHIP with a greater number of passenger mutations in the mutant clone is expected to have acquired the clone at a later age than someone with fewer passenger mutations. For two individuals of the same age and with clones of the same size, we expect the clone with more passengers to be more fit, as it expanded to the same size in less time. Typically, one would need to isolate single-cell colonies derived from HSCs in order to calculate the total passenger mutation burden. However, we hypothesized that this measure could also be approximated from whole genome sequencing of blood cell DNA, such as that used in large biobank projects. The expansion rate (PACER) is then estimated by adjusting the total passenger count for age and variant allele fraction in each individual. The ability of passengers to predict future clonal expansion was validated using longitudinal blood samples from 51 CHIP carriers in the Women's Health Initiative taken ~10 years apart (Figure 1). It also accurately predicted the known fitness effects due to different driver mutations in 5,551 CHIP carriers from the Trans-Omics for Precision Medicine (TOPMed) program (Figure 2). Results: Having validated the approach, we next hypothesized that we could identify germline variants influencing PACER, thus revealing genes and pathways mediating clonal expansion. The lead hit in a genome-wide association study (GWAS) of PACER was a common single nucleotide polymorphism (SNP) in the TCL1A promoter that was associated with slower clonal expansion in CHIP overall (Figure 3). TCL1A is an oncogene that is activated via translocation in T-cell prolymphocytic leukemia, but has no known role in CHIP or myeloid malignancies. A gene-level analysis indicated that the TCL1A SNP was associated with slower growth of clones bearing TET2 mutations, but had no effect on DNMT3A-mutant clone growth. We further found that those carrying two copies of the protective SNP had 40-80% reduced odds of having clones with driver mutations in TET2, ASXL1, SF3B1, SRSF2, and JAK2, but not DNMT3A. A concomitant decrease in incident myeloid malignancies was also seen in carriers of this protective SNP. Next, we interrogated how the protective SNP influenced TCL1A activity in HSCs. Normal human HSCs lacked open chromatin at the TCL1A promoter and TCL1A expression, but inducing frameshift mutations in TET2 via CRISPR editing led to accessibility of the promoter and gene/protein expression in HSCs (Figure 4). This effect was abrogated in HSCs from donors of the protective TCL1A SNP in a dose-dependent manner. Finally, we found that HSCs from donors homozygous for the protective SNP had markedly less expansion of phenotypic stem and progenitor cells in vitro after the introduction of TET2 mutations than TET2-edited HSCs from donors with two copies of the reference allele. Conclusions: In summary, we developed a novel method to infer the expansion rate of pre-malignant clones and performed the first ever GWAS for this trait. Our results indicate that the fitness advantage of several common driver genes in CHIP and hematological cancers is mediated through TCL1A activation, which may be a therapeutic target to treat these conditions. PACER is an approach that can be widely adopted to uncover genetic and environmental determinants of pre-malignant clonal expansion in blood and other tissues. Figure 1 Figure 1. Disclosures Desai: Bristol Myers Squibb: Consultancy; Kura Oncology: Consultancy; Agios: Consultancy; Astex: Research Funding; Takeda: Consultancy; Janssen R&D: Research Funding. Natarajan: Blackstone Life Sciences: Consultancy; Boston Scientific: Research Funding; Novartis: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Apple: Consultancy, Research Funding; Amgen: Research Funding; Genentech: Consultancy; Foresite Labs: Consultancy. Jaiswal: Novartis: Consultancy, Honoraria; AVRO Bio: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; Foresite Labs: Consultancy; Caylo: Current holder of stock options in a privately-held company.

Clonal hematopoiesis of indeterminate potential (CHIP) occurs when hematopoietic stem cells (HSCs) acquire a mutation, most commonly a null variant in TET2 or DNMT3A, that confers a selective advantage. Blood cancers may result if additional cooperating mutations are acquired. However, CHIP may also cause atherosclerosis and other inflammatory diseases because these mutations alter the function or development of effector immune cells derived from the HSCs. Genome-wide association studies have implicated microglia, the resident myeloid cells in the brain, as key players in the biology of Alzheimer's disease (AD). Here, we asked whether CHIP associated with AD dementia or neuropathologic change, and whether mutant marrow-derived cells could be found in the brains of CHIP carriers. To test for an association, we used data from the Trans-omics for Precision Medicine project (TOPMed) and the Alzheimer's Disease Sequencing Project (ADSP), where whole genome or exome sequencing data as well as AD phenotype data was available on 5,730 persons. TOPMed contained population-based cohorts unselected for AD, while ADSP was a case-control study for AD. We surprisingly discovered that the presence of CHIP was associated with a reduced risk of AD dementia in both projects (fixed-effects meta-analysis odds ratio 0.64, p = 3.0 x 10-5, adjusted for age, sex and APOE genotype) (Figure 1). The protective effect of CHIP was strongest in those with APOE e3 or e4 alleles, but not seen in those with APOE e2 allele. No substantial differences in AD risk were seen based on mutated driver gene. In addition, the presence of CHIP was associated with a reduced burden of amyloid plaques and neurofibrillary tangles in the brains of those without dementia. In sum, our human genetic analyses indicated that CHIP was robustly associated with protection from AD dementia and AD-related neuropathologic changes. A causal link between CHIP and AD would be strengthened by finding the mutated cells infiltrating the brain. However, it is presumed that bone marrow progenitors have minimal contribution to the adult microglial pool. To determine if the mutations seen in the blood of CHIP carriers could also be found in the brain, we obtained 8 occipital cortex samples from autopsy of donors with CHIP, 6 of whom were cognitively normal at the time of death. The 8 CHIP carriers had mutations in DNMT3A, TET2, ASXL1, SF3B1, and GNB1 with the highest frequency in DNMT3A and TET2, which is representative of the relative proportion of these mutations in the general population. We detected the CHIP somatic variants in the microglia enriched (NeuN- c-Maf+) fraction of brain in 7 out of 8 CHIP carriers, with a VAF ranging from 0.02 to 0.28 (representing 4% to 56% of nuclei) (Figure 2), but at low levels or absent in the other fractions of brain. We then performed single-cell ATAC-sequencing on brain samples from 2 CHIP carriers and 1 control to specify the cellular population harboring CHIP mutations. This revealed that hematopoietic cells in the 3 samples formed a single myeloid cluster that had accessible chromatin at the microglia marker genes TMEM119, P2RY12, and SALL1, but not in genes specific to monocytes or dendritic cells. We further determined that the proportion of cells in this cluster bearing the CHIP mutations ranged from ~40-80% in these two samples, indicating widespread replacement of the endogenous microglial pool by mutant cells. We show here that, unexpectedly, the presence of CHIP is associated with protection from AD dementia. CHIP is also associated with lower levels of neuritic plaques and neurofibrillary tangles in those without dementia, indicating a possible modulating effect of CHIP on the underlying pathophysiology of AD. Consistent with this hypothesis, we also detect substantial infiltration of brain by marrow-derived mutant cells which adopt a microglial-like phenotype. We speculate that the mutations associated with CHIP confer circulating precursor cells with an enhanced ability to engraft in the brain, to differentiate into microglia once engrafted, and/or to clonally expand relative to unmutated cells in the brain microenvironment. These non-mutually exclusive possibilities could provide protection from AD by supplementing the phagocytic capacity of the endogenous microglial system during aging. Figure 1 Figure 1. Disclosures Jaiswal: Novartis: Consultancy, Honoraria; Foresite Labs: Consultancy; Genentech: Consultancy, Honoraria; AVRO Bio: Consultancy, Honoraria; Caylo: Current holder of stock options in a privately-held company.

Cryptic signs of aging in our blood Time is not a friend to our DNA. Aging is associated with an accumulation of somatic mutations in normal dividing cells, including the hematopoietic stem cells (HSCs) that give rise to all blood cells. Certain mutations in HSCs confer a fitness advantage that results in clonal expansions of mutant blood cells that sometimes—but not always—forecast the development of cancer and other age-related diseases. Jaiswal and Ebert review this process of “clonal hematopoiesis,” including the mechanisms by which it arises and the current state of knowledge regarding its effects on human health. Science , this issue p. eaan4673

© 2020, The Author(s), under exclusive licence to Springer Nature Limited. Age is the dominant risk factor for most chronic human diseases, but the mechanisms through which ageing confers this risk are largely unknown1. The age-related acquisition of somatic mutations that lead to clonal expansion in regenerating haematopoietic stem cell populations has recently been associated with both haematological cancer2–4 and coronary heart disease5—this phenomenon is termed clonal haematopoiesis of indeterminate potential (CHIP)6. Simultaneous analyses of germline and somatic whole-genome sequences provide the opportunity to identify root causes of CHIP. Here we analyse high-coverage whole-genome sequences from 97,691 participants of diverse ancestries in the National Heart, Lung, and Blood Institute Trans-omics for Precision Medicine (TOPMed) programme, and identify 4,229 individuals with CHIP. We identify associations with blood cell, lipid and inflammatory traits that are specific to different CHIP driver genes. Association of a genome-wide set of germline genetic variants enabled the identification of three genetic loci associated with CHIP status, including one locus at TET2 that was specific to individuals of African ancestry. In silico-informed in vitro evaluation of the TET2 germline locus enabled the identification of a causal variant that disrupts a TET2 distal enhancer, resulting in increased self-renewal of haematopoietic stem cells. Overall, we observe that germline genetic variation shapes haematopoietic stem cell function, leading to CHIP through mechanisms that are specific to clonal haematopoiesis as well as shared mechanisms that lead to somatic mutations across tissues.

A novel, common, and potent cardiovascular risk factor has recently emerged: clonal hematopoiesis of indeterminate potential (CHIP). CHIP arises from somatic mutations in hematopoietic stem cells that yield clonal progeny of mutant leukocytes in blood. Individuals with CHIP have a doubled risk of coronary heart disease and ischemic stroke, and worsened heart failure outcomes independent of traditional cardiovascular risk factors. The recognition of CHIP as a non-traditional risk factor challenges specialists in hematology/oncology and cardiovascular medicine alike. Should we screen for CHIP? If so, in whom? How should we assess cardiovascular risk in people with CHIP? How do we manage the excess cardiovascular risk in the absence of an evidence base to guide us? This document explains CHIP, explores the clinical quandaries, strives to provide reasonable recommendations for the multidisciplinary management of cardiovascular risk in individuals with CHIP, and highlights current knowledge gaps.

Clonal hematopoiesis is a common, age-related process in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. This phenomenon has been observed in populations across the globe and, while virtually non-existent in children is estimated to affect10% of the 70-and-older age group. The mutations are thought to occur in stem cells, which makes them pre-cancerous, and precursors to cancer stem cells. Many of the genes most commonly mutated in clonal hematopoiesis are also recurrently mutated in leukemia, genes such as DNMT3A, TET2, ASXL1, JAK2, and TP53. However, between 40% and 60% of cases arise from the accumulation of what appear to be random mutations outside of known driver genes. Clonal hematopoiesis is frequently present in otherwise healthy individuals and may persist for many years. Though largely asymptomatic, carrying these somatic mutations confers a small but significantly increased risk of leukemic transformation, affecting 0.5-1% carriers per year; although most genes confer an increased risk of transformation, mutations in TP53 and U2AF1 appear to carry a particularly high risk for transformation. Additionally, a patient's history of prior treatment with cytotoxic chemotherapy and/or radiation are correlated with the development of clonal hematopoiesis; in the setting of chemotherapy treatment of solid tumors, hematopoietic mutations in TP53 and PPM1D appear to contribute to outgrowth of clones that may lead to subsequent malignancy. The presence of a clone also imparts a significantly increased risk of cardiovascular disease, which in some cases appears to be due to increased inflammation and atherosclerosis. Clonal hematopoiesis is correlated with several other diseases as well, including diabetes, chronic pulmonary disease, and aplastic anemia, with other associations probably yet to be uncovered.

SummaryMolecular and cellular changes are intrinsic to aging and age-related diseases. Prior cross-sectional studies have investigated the combined effects of age and genetics on gene expression and alternative splicing; however, there has been no long-term, longitudinal characterization of these molecular changes, especially in older age. We performed RNA sequencing in whole-blood from the same individuals from the PIVUS study at ages 70 and 80 to quantify how gene expression, alternative splicing, and their genetic regulation are altered during this 10-year period of advanced aging. We observe that individuals are more similar to their own expression profiles later in life than profiles of other individuals their own age; 93% of samples cluster with their own measurement at another age, and there is a strong correlation of genetic effects on expression between the two ages (median ρG = 0.96). Despite this, we identify 1,291 and 294 genes differentially expressed and alternatively spliced with age, as well as 529 genes with outlying individual trajectories of aging. Further, 7.8% and 9.6% of tested genes show a reduction in genetic associations with expression and alternative splicing in older age, with impacted genes enriched in DNA repair pathways. Together these findings indicate that, although gene expression and alternative splicing and their genetic regulation are mostly stable late in life, a small subset of genes is dynamic and is characterized by changes in expression and splicing and a reduction in genetic regulation.

Clonal hematopoiesis is a common, age-related process in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. This phenomenon has been observed in populations across the globe and, while virtually non-existent in children is estimated to affect >10% of the 70-and-older age group. The mutations are thought to occur in stem cells, which makes them pre-cancerous, and precursors to cancer stem cells. Many of the genes most commonly mutated in clonal hematopoiesis are also recurrently mutated in leukemia, genes such as DNMT3A, TET2, ASXL1, JAK2, and TP53. However, between 40% and 60% of cases arise from the accumulation of what appear to be random mutations outside of known driver genes. Clonal hematopoiesis is frequently present in otherwise healthy individuals and may persist for many years. Though largely asymptomatic, carrying these somatic mutations confers a small but significantly increased risk of leukemic transformation, affecting 0.5-1% carriers per year; although most genes confer an increased risk of transformation, mutations in TP53 and U2AF1 appear to carry a particularly high risk for transformation. Additionally, a patient's history of prior treatment with cytotoxic chemotherapy and/or radiation are correlated with the development of clonal hematopoiesis; in the setting of chemotherapy treatment of solid tumors, hematopoietic mutations in TP53 and PPM1D appear to contribute to outgrowth of clones that may lead to subsequent malignancy. The presence of a clone also imparts a significantly increased risk of cardiovascular disease, which in some cases appears to be due to increased inflammation and atherosclerosis. Clonal hematopoiesis is correlated with several other diseases as well, including diabetes, chronic pulmonary disease, and aplastic anemia, with other associations probably yet to be uncovered.

Additional file 12 Review history.

Jaiswal et al. report the results of four case–control studies that confirm a near doubling in the risk of coronary heart disease in patients with CHIP,1 a finding that was first reported in the Journal in 2014.2 The authors postulate that two mechanisms may be involved: the promotion of inflammatory responses, as supported in a study involving Tet2 knockout mice, and an increase in the number of myeloid cells, a finding that appears to be more relevant for patients with JAK2 mutations, which confer a much larger risk than the more common DNMT3A, TET2, and ASXL1 mutations, in which blood counts remain normal. However, the authors do not provide data relating to red-cell distribution width, which is the only blood-cell index that has been shown to have a significant association with CHIP2 and which has been associated with an unexplained increase in all-cause mortality in an aging population. 3,4 In understanding how CHIP promotes atherosclerosis, it is important to explore the causal relationship between clonal hematopoiesis and red-cell anisocytosis to determine whether these are independent or associated risk factors for cardiovascular disease.