Therapy-Related Clonal Hematopoiesis: A New Link Between Cancer and Cardiovascular Disease

Cardiovascular Disease and Cancer: A Dangerous Liaison

The field of cardio-oncology has traditionally focused on the impact of cancer and its therapies on cardiovascular health. Mounting clinical and preclinical evidence, however, indicates that the reverse may also be true: cardiovascular disease can itself influence tumor growth and metastasis. Numerous epidemiological studies have reported that individuals with prevalent cardiovascular disease have an increased incidence of cancer. In parallel, studies using preclinical mouse models of myocardial infarction, heart failure, and cardiac remodeling support the notion that cardiovascular disorders accelerate the growth of solid tumors and metastases. These findings have ushered in a new and burgeoning field termed reverse cardio-oncology that investigates the impact of cardiovascular disease pathophysiology on cancer emergence and progression. Recent studies have begun to illuminate the mechanisms driving this relationship, including shared risk factors, reprogramming of immune responses, changes in gene expression, and the release of cardiac factors that result in selective advantages for tumor cells or their local milieu, thus exacerbating cancer pathology. Here, we review the evidence supporting the relationship between cardiovascular disease and cancer, the mechanistic pathways enabling this connection, and the implications of these findings for patient care.

Early cardio-oncology intervention in thoracic radiotherapy: prospective single-arm pilot study

BACKGROUND

While there is increasing recognition of the morbidity of cardiovascular disease in cancer survivors, including accelerated atherosclerosis following thoracic radiotherapy, patients are frequently under-optimized for cardiovascular risk.

METHODS

In this prospective single-arm cohort pilot study, patients were treated with high-dose thoracic radiotherapy and had early consultation with cardio-oncology. Twenty patients were enrolled. The primary endpoint was adherence to cardio-oncology consultation. Secondary endpoints were cardiovascular medication intervention rate and patient-reported intervention perspectives. Clonal hematopoiesis of indeterminate potential, a major cardiovascular risk marker enriched in patients with cancer and induced by radiation exposure, was measured as an exploratory endpoint.

RESULTS

The cohort median age is 71 years. Most patients are female (13/20), have primary lung or esophageal carcinoma (16/20), and 7/20 have pre-existing cardiovascular disease. We show that cardio-oncology consultation adherence is high (19/20) and results in cardiovascular medication optimization changes in most patients (12/19), most commonly to initiate or intensify statin therapy (8/12). 8/12 patients with a primary cardiologist prior to enrollment have medication changes recommended. Most (12/17) participants are glad to learn about their heart health during cancer treatment. Clonal hematopoiesis is detectable prior to treatment in 8/20 patients and three develop new variants after treatment (1/3 de novo).

CONCLUSIONS

We observe that early cardio-oncology consultation is feasible, leads to cardiovascular medication optimization in the majority (>60%) of participants, most commonly to initiate or intensify statin therapy. New clonal hematopoiesis variants are detectable early after radiotherapy and the impact on post-treatment cardiovascular risk is worthy of further study.

The emerging role of clonal haematopoiesis in the pathogenesis of dilated cardiomyopathy

The increased sensitivity of novel DNA sequencing techniques has made it possible to identify somatic mutations in small circulating clones of haematopoietic stem cells. When the mutation affects a 'driver' gene, the mutant clone gains a competitive advantage and has the potential to expand over time, a phenomenon referred to as clonal haematopoiesis (CH), which is emerging as a new risk factor for various non-haematological conditions, most notably cardiovascular disease (e.g. heart failure). Dilated cardiomyopathy (DCM) is a form of non-ischaemic heart failure that is characterized by a heterogeneous aetiology. The first evidence is arising that CH plays an important role in the disease course in patients with DCM, and a strong association of CH with multiple aetiologies of DCM has been described (e.g. inflammation, chemotherapy, and atrial fibrillation). The myocardial inflammation induced by CH may be an important trigger for DCM development for an already susceptible heart, e.g. in the presence of genetic variants, environmental triggers, and comorbidities. Studies investigating the role of CH in the pathogenesis of DCM are expected to increase rapidly. To move the field forward, it will be important to report the methodology and results in a standardized manner, so results can be combined and compared. The accurate measurement of CH in patients with DCM can provide guidance of specific (anti-inflammatory) therapies, as mutations in the CH driver genes prime the inflammasome pathway.

Distinct landscape and clinical implications of therapy-related clonal hematopoiesis

Therapy-related clonal hematopoiesis (t-CH) is defined as clonal hematopoiesis detected in individuals previously treated with chemotherapy and/or radiation therapy. With the increased use of genetic analysis in oncological care, the detection of t-CH among cancer patients is becoming increasingly common. t-CH arises through the selective bottleneck imposed by chemotherapies and potentially through direct mutagenesis from chemotherapies, resulting in a distinct mutational landscape enriched with mutations in DNA damage-response pathway genes such as TP53, PPM1D, and CHEK2. Emerging evidence sheds light on the mechanisms of t-CH development and potential strategies to mitigate its emergence. Due to its unique characteristics that predominantly affect cancer patients, t-CH has clinical implications distinct from those of CH in the general population. This Review discusses the potential mechanisms of t-CH development, its mutational landscape, mutant-drug relationships, and its clinical significance. We highlight the distinct nature of t-CH and call for intensified research in this field.

Cardiovascular disease and cancer: shared risk factors and mechanisms

Cardiovascular disease (CVD) and cancer are among the leading causes of morbidity and mortality globally, and these conditions are increasingly recognized to be fundamentally interconnected. In this Review, we present the current epidemiological data for each of the modifiable risk factors shared by the two diseases, including hypertension, hyperlipidaemia, diabetes mellitus, obesity, smoking, diet, physical activity and the social determinants of health. We then review the epidemiological data demonstrating the increased risk of CVD in patients with cancer, as well as the increased risk of cancer in patients with CVD. We also discuss the shared mechanisms implicated in the development of these conditions, highlighting their inherent bidirectional relationship. We conclude with a perspective on future research directions for the field of cardio-oncology to advance the care of patients with CVD and cancer.

Interplay of the heart, spleen, and bone marrow in heart failure: the role of splenic extramedullary hematopoiesis

Improvements in therapies for heart failure with preserved ejection fraction (HFpEF) are crucial for improving patient outcomes and quality of life. Although HFpEF is the predominant heart failure type among older individuals, its prognosis is often poor owing to the lack of effective therapies. The roles of the spleen and bone marrow are often overlooked in the context of HFpEF. Recent studies suggest that the spleen and bone marrow could play key roles in HFpEF, especially in relation to inflammation and immune responses. The bone marrow can increase production of certain immune cells that can migrate to the heart and contribute to disease. The spleen can contribute to immune responses that either protect or exacerbate heart failure. Extramedullary hematopoiesis in the spleen could play a crucial role in HFpEF. Increased metabolic activity in the spleen, immune cell production and mobilization to the heart, and concomitant cytokine production may occur in heart failure. This leads to systemic chronic inflammation, along with an imbalance of immune cells (macrophages) in the heart, resulting in chronic inflammation and progressive fibrosis, potentially leading to decreased cardiac function. The bone marrow and spleen are involved in altered iron metabolism and anemia, which also contribute to HFpEF. This review presents the concept of an interplay between the heart, spleen, and bone marrow in the setting of HFpEF, with a particular focus on extramedullary hematopoiesis in the spleen. The aim of this review is to discern whether the spleen can serve as a new therapeutic target for HFpEF.

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.