Clonal Hematopoiesis at the Crossroads of Inflammatory Bowel Diseases and Hematological Malignancies: A Biological Link?

Risk of Hematologic Malignancies in Patients with Inflammatory Bowel Disease: A Meta-Analysis of Cohort Studies

Background/Aims

Inflammatory bowel disease (IBD) may contribute to the development of hematologic malignancies. In this study, the potential relationship between IBD and hematologic malignancies was investigated.

Methods

We searched the PubMed, Web of Science, Embase, and Cochrane Library databases for all cohort studies comparing the incidence of hematologic malignancies in non-IBD populations with that in IBD patients, and we extracted relevant data from January 2000 to June 2023 for meta-analysis.

Results

Twenty cohort studies involving 756,377 participants were included in this study. The results showed that compared with the non-IBD cohort, the incidence of hematologic malignancies in the IBD cohort was higher (standardized incidence ratio [SIR]=3.05, p<0.001). According to the specific types of IBD, compared with the non-IBD patients, the incidences of hematologic malignancies in ulcerative colitis patients (SIR=2.29, p=0.05) and Crohn's disease patients (SIR=3.56, p=0.005) were all higher. In the subgroup analysis of hematologic malignancy types, compared with the control group, the incidences of non-Hodgkin's lymphoma (SIR=1.70, p=0.01), Hodgkin's lymphoma (SIR=3.47, p=0.002), and leukemia (SIR=3.69, p<0.001) were all higher in the IBD cohort.

Conclusions

The incidence of hematologic malignancies, including non-Hodgkin's lymphoma, Hodgkin's lymphoma, and leukemia is higher in patients with IBD (ulcerative colitis or Crohn's disease) than in non-IBD patients.

Clonal hematopoiesis and inflammation in the vasculature: CHIVE, a prospective, longitudinal clonal hematopoiesis cohort and biorepository

ABSTRACT

Clonal hematopoiesis (CH) is an age-associated phenomenon leading to an increased risk of both hematologic malignancy and nonmalignant organ dysfunction. Increasingly available genetic testing has made the incidental discovery of CH clinically common yet evidence-based guidelines and effective management strategies to prevent adverse CH health outcomes are lacking. To address this gap, the prospective CHIVE (clonal hematopoiesis and inflammation in the vasculature) registry and biorepository was created to identify and monitor individuals at risk, support multidisciplinary CH clinics, and refine taxonomy and standards of practice for CH risk mitigation. Data from the first 181 patients enrolled in this prospective registry recapitulate the molecular epidemiology of CH from biobank-scale retrospective studies, with DNMT3A, TET2, ASXL1, and TP53 as the most commonly mutated genes. Blood counts across all hematopoietic lineages trended lower in patients with CH. In addition, patients with CH had higher rates of end organ dysfunction, in particular chronic kidney disease. Among patients with CH, variant allele frequency was independently associated with the presence of cytopenias and progression to hematologic malignancy, whereas other common high-risk CH clone features were not clear. Notably, accumulation of multiple distinct high-risk clone features was also associated with cytopenias and hematologic malignancy progression, supporting a recently published CH risk score. Surprisingly, ∼30% of patients enrolled in CHIVE from CH clinics were adjudicated as not having clonal hematopoiesis of indeterminate potential, highlighting the need for molecular standards and purpose-built assays in this field. Maintenance of this well-annotated cohort and continued expansion of CHIVE to multiple institutions are underway and will be critical to understanding how to thoughtfully care for this patient population.

Clonal hematopoiesis and autoimmunity

Clonal hematopoiesis (CH) has been associated with aging, occurring in about 10% of individuals aged >70 years, and immune dysfunction. Aged hematopoietic stem and progenitor cells exhibit pathological changes in immune function and activation of inflammatory pathways. CH clones commonly harbor a loss of function mutation in DNMT3A or TET2, which causes increased expression of inflammatory signaling genes, a proposed mechanism connected to CH and the development of age-related diseases. Additionally, inflammation may stress the hematopoietic compartment, driving the expansion of mutant clones. While the epidemiologic overlap between CH, hematologic malignancies, and atherosclerotic cardiovascular diseases has been reported, the mechanisms linking these concepts are largely unknown and merit much further investigation. Here, we review studies highlighting the interplay between CH, inflamm-aging, the immune system, and the prevalence of CH in autoimmune diseases.

Clonal Hematopoiesis, Inflammation, and Hematologic Malignancy

Somatic or acquired mutations are postzygotic genetic variations that can occur within any tissue. These mutations accumulate during aging and have classically been linked to malignant processes. Tremendous advancements over the past years have led to a deeper understanding of the role of somatic mutations in benign and malignant age-related diseases. Here, we review the somatic mutations that accumulate in the blood and their connection to disease states, with a particular focus on inflammatory diseases and myelodysplastic syndrome. We include a definition of clonal hematopoiesis (CH) and an overview of the origins and implications of these mutations. In addition, we emphasize somatic disorders with overlapping inflammation and hematologic disease beyond CH, including paroxysmal nocturnal hemoglobinuria and aplastic anemia, focusing on VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. Finally, we provide a practical view of the implications of somatic mutations in clinical hematology, pathology, and beyond.

Altered DNA methylation within DNMT3A, AHRR, LTA/TNF loci mediates the effect of smoking on inflammatory bowel disease

This work aims to investigate how smoking exerts effect on the development of inflammatory bowel disease (IBD). A prospective cohort study and a Mendelian randomization study are first conducted to evaluate the association between smoking behaviors, smoking-related DNA methylation and the risks of Crohn's disease (CD) and ulcerative colitis (UC). We then perform both genome-wide methylation analysis and co-localization analysis to validate the observed associations. Compared to never smoking, current and previous smoking habits are associated with increased CD (P = 7.09 × 10-10) and UC (P < 2 × 10-16) risk, respectively. DNA methylation alteration at cg17742416 [DNMT3A] is linked to both CD (P = 7.30 × 10-8) and UC (P = 1.04 × 10-4) risk, while cg03599224 [LTA/TNF] is associated with CD risk (P = 1.91 × 10-6), and cg14647125 [AHRR] and cg23916896 [AHRR] are linked to UC risk (P = 0.001 and 0.002, respectively). Our study identifies biological mechanisms and pathways involved in the effects of smoking on the pathogenesis of IBD.

Regulators of clonal hematopoiesis and physiological consequences of this condition

Clonal hematopoiesis (CH) is a prevalent condition that results from somatic mutations in hematopoietic stem cells. When these mutations occur in "driver" genes, they can potentially confer fitness advantages to the affected cells, leading to a clonal expansion. While most clonal expansions of mutant cells are generally considered to be asymptomatic since they do not impact overall blood cell numbers, CH carriers face long-term risks of all-cause mortality and age-associated diseases, including cardiovascular disease and hematological malignancies. While considerable research has focused on understanding the association between CH and these diseases, less attention has been given to exploring the regulatory factors that contribute to the expansion of the driver gene clone. This review focuses on the association between environmental stressors and inherited genetic risk factors in the context of CH development. A better understanding of how these stressors impact CH development will facilitate mechanistic studies and potentially lead to new therapeutic avenues to treat individuals with this condition.

Ulcerative Colitis Concomitant with Cytomegalovirus Infection, Bullous Sweet's Syndrome, and Acute Myeloid Leukemia: A Case Report and Literature Review

Background

Ulcerative colitis (UC) is a chronic, relapsing progressive inflammatory immune disease. There is still no cure for it. Even worse, UC may predispose patients to opportunistic infections, and several extra-intestinal manifestations (EIMs) and comorbidities may antedate, occur with, or postdate the onset of UC, which may increase the mortality risk. But case reports of UC patients simultaneously concomitant with opportunistic infection, EIM, and comorbidity are extremely rare.

Case Presentation

We report a case of 51-year-old male patient with incipient UC accompanied by cytomegalovirus (CMV) infection and bullous Sweet's syndrome (bSS, a cutaneous EIM of UC) after treatment with oral mesalazine and prednisolone for 3 weeks. After clearance of the CMV infection by using ganciclovir, the patient was administered two cycles of infliximab to cure UC and bSS; however, he developed acute myeloid leukemia (AML) a month later and died after two cycles of chemotherapy.

Conclusion

Based on this rare case of UC concomitant with CMV infection, bSS and AML, we recommend that it is important to distinguish between an acute UC flare and opportunistic infections, especially in patients receiving immunosuppressive therapy, and monitor EIMs and comorbidities timely. Particular attention should be paid to cancer surveillance. Clinicians should be mindful of these facts to adopt optimal therapeutic options to address all aspects of UC. Early initiation of biological therapy may be of benefit to patients with newly diagnosed severe UC.

Microbiota Influences on Hematopoiesis and Blood Cancers: New Horizons?

Hematopoiesis governs the generation of immune cells through the differentiation of hematopoietic stem cells (HSC) into various progenitor cells, a process controlled by intrinsic and extrinsic factors. Among extrinsic factors influencing hematopoiesis is the microbiota, or the collection of microorganisms present in various body sites. The microbiota has a profound impact on host homeostasis by virtue of its ability to release various molecules and structural components, which promote normal organ function. In this review, we will discuss the role of microbiota in influencing hematopoiesis and how disrupting the microbiota/host network could lead to hematologic malignancies, as well as highlight important knowledge gaps to move this field of research forward.

SIGNIFICANCE

Microbiota dysfunction is associated with many pathologic conditions, including hematologic malignancies. In this review, we discuss the role of microbiota in influencing hematopoiesis and how disrupting the microbiota/host network could lead to hematologic malignancies. Understanding how the microbiota influences hematologic malignancies could have an important therapeutic impact for patients.

Interplay between chronic inflammation and clonal haematopoiesis of indeterminate potential in Behçet's disease

BACKGROUND

Clonal haematopoiesis of indeterminate potential (CHIP) is a predisposition to haematological malignancy whose relationship with chronic inflammatory diseases, such as cardiovascular diseases, has been highlighted. Here, we aimed to investigate the CHIP emergence rate and its association with inflammatory markers in Behçet's disease (BD).

METHODS

We performed targeted next-generation sequencing to detect the presence of CHIP using peripheral blood cells from 117 BD patients and 5004 healthy controls between March 2009 and September 2021 and analysed the association between CHIP and inflammatory markers.

RESULTS

CHIP was detected in 13.9% of patients in the control group and 11.1% of patients in the BD group, indicating no significant intergroup difference. Among the BD patients of our cohort, five variants (DNMT3A, TET2, ASXL1, STAG2, and IDH2) were detected. DNMT3A mutations were the most common, followed by TET2 mutations. CHIP carriers with BD had a higher serum platelet count, erythrocyte sedimentation rate, and C-reactive protein level; older age; and lower serum albumin level at diagnosis than non-CHIP carriers with BD. However, the significant association between inflammatory markers and CHIP disappeared after the adjustment for various variables, including age. Moreover, CHIP was not an independent risk factor for poor clinical outcomes in patients with BD.

CONCLUSIONS

Although BD patients did not have higher CHIP emergence rates than the general population, older age and degree of inflammation in BD were associated with CHIP emergence.

Clonal hematopoiesis onset in chronic myeloid leukemia patients developing an adverse cardiovascular event

Life expectation of chronic myeloid leukemia patients in the tyrosine kinase inhibitors era is almost equal to that of healthy subjects. On the other hand, their long-term management must take into account a higher risk of adverse events, at least partly related to the treatment. Various studies reported a higher incidence of cardiovascular events in these patients. Clonal hematopoiesis is broadly considered a major independent risk factor for cardiovascular events. Of note, the underlying physiopathological mechanisms connect clonal hematopoiesis with a global proinflammatory status, triggering a vicious circle in which the somatic mutations and inflammation feed each other. All this considered, we investigated the occurrence of clonal hematopoiesis in chronic myeloid leukemia patients developing a cardiovascular event under tyrosine kinase inhibitor therapy.

Clonal hematopoiesis, somatic mosaicism, and age-associated disease

Somatic mosaicism, the occurrence of multiple genetically distinct cell clones within the same tissue, is an evitable consequence of human aging. The hematopoietic system is no exception to this, where studies have revealed the presence of expanded blood cell clones carrying mutations in preleukemic driver genes and/or genetic alterations in chromosomes. This phenomenon is referred to as clonal hematopoiesis and is remarkably prevalent in elderly individuals. While clonal hematopoiesis represents an early step toward a hematological malignancy, most individuals will never develop blood cancer. Somewhat unexpectedly, epidemiological studies have found that clonal hematopoiesis is associated with an increase in the risk of all-cause mortality and age-related disease, particularly in the cardiovascular system. Studies using murine models of clonal hematopoiesis have begun to shed light on this relationship, suggesting that driver mutations in mature blood cells can causally contribute to aging and disease by augmenting inflammatory processes. Here we provide an up-to-date review of clonal hematopoiesis within the context of somatic mosaicism and aging and describe recent epidemiological studies that have reported associations with age-related disease. We will also discuss the experimental studies that have provided important mechanistic insight into how driver mutations promote age-related disease and how this knowledge could be leveraged to treat individuals with clonal hematopoiesis.

The genomic analysis brings a new piece to the molecular jigsaw of idiopathic erythrocytosis

Erythrocytosis is a clinical condition characterized by increased red cell mass, hemoglobin, and hematocrit values. A significant fraction of patients is described as having idiopathic erythrocytosis. We have previously demonstrated an association between erythrocytosis and the JAK2 GGCC_46/1 haplotype and CALR rs1049481_G allele. In the present study, we investigated genomic and clinical features of 80 erythrocytosis patients with the aim to provide useful information in clinical practice. Patients with idiopathic erythrocytosis could have a genomic germline background, eventually associated with somatic variants. Through association analysis, we show that male patients presenting with idiopathic erythrocytosis, and normal EPO levels could be the best candidates for the search for the JAK2 GGCC_46/1 haplotype and CALR rs1049481_G allele. Further studies are needed to confirm these findings and to depict detailed genomic and phenotypical characteristics of these patients.