Familial chronic myeloproliferative disorders: clinical phenotype and evidence of disease anticipation

Exploiting Synthetic Lethality between Germline BRCA1 Haploinsufficiency and PARP Inhibition in JAK2V617F-Positive Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) are rare hematologic disorders characterized by clonal hematopoiesis. Familial clustering is observed in a subset of cases, with a notable proportion exhibiting heterozygous germline mutations in DNA double-strand break repair genes (e.g., BRCA1). We investigated the therapeutic potential of targeting BRCA1 haploinsufficiency alongside the JAK2V617F driver mutation. We assessed the efficacy of combining the PARP inhibitor olaparib with interferon-alpha (IFNα) in CRISPR/Cas9-engineered Brca1+/- Jak2V617F-positive 32D cells. Olaparib treatment induced a higher number of DNA double-strand breaks, as demonstrated by γH2AX analysis through Western blot (p = 0.024), flow cytometry (p = 0.013), and confocal microscopy (p = 0.071). RAD51 foci formation was impaired in Brca1+/- cells compared to Brca1+/+ cells, indicating impaired homologous recombination repair due to Brca1 haploinsufficiency. Importantly, olaparib enhanced apoptosis while diminishing cell proliferation and viability in Brca1+/- cells compared to Brca1+/+ cells. These effects were further potentiated by IFNα. Olaparib induced interferon-stimulated genes and increased endogenous production of IFNα in Brca1+/- cells. These responses were abrogated by STING inhibition. In conclusion, our findings suggest that the combination of olaparib and IFNα presents a promising therapeutic strategy for MPN patients by exploiting the synthetic lethality between germline BRCA1 mutations and the JAK2V617F MPN driver mutation.

Recurrent germline variant in ATM associated with familial myeloproliferative neoplasms

Genetic predisposition (familial risk) in the myeloproliferative neoplasms (MPNs) is more common than the risk observed in most other cancers, including breast, prostate, and colon. Up to 10% of MPNs are considered to be familial. Recent genome-wide association studies have identified genomic loci associated with an MPN diagnosis. However, the identification of variants with functional contributions to the development of MPN remains limited. In this study, we have included 630 MPN patients and whole genome sequencing was performed in 64 individuals with familial MPN to uncover recurrent germline predisposition variants. Both targeted and unbiased filtering of single nucleotide variants (SNVs) was performed, with a comparison to 218 individuals with MPN unselected for familial status. This approach identified an ATM L2307F SNV occurring in nearly 8% of individuals with familial MPN. Structural protein modeling of this variant suggested stabilization of inactive ATM dimer, and alteration of the endogenous ATM locus in a human myeloid cell line resulted in decreased phosphorylation of the downstream tumor suppressor CHEK2. These results implicate ATM, and the DNA-damage response pathway, in predisposition to MPN.

Identification of putative noncanonical driver mutations in patients with essential thrombocythemia

Essential thrombocythemia (ET) cases without canonical JAK2, CALR, or MPL mutations, that is, triple-negative (TN) ET, have been found in 10%-20% of ET cases. Owing to the limited number of TN ET cases, its clinical significance remains unclear. This study evaluated TN ET's clinical characteristics and identified novel driver mutations. Among 119 patients with ET, 20 (16.8%) had no canonical JAK2/CALR/MPL mutations. Patients with TN ET tended to be younger and had lower white blood cell counts and lactate dehydrogenase values. We identified putative driver mutations in 7 (35%): MPL S204P, MPL L265F, JAK2 R683G, and JAK2 T875N were previously reported as candidate driver mutations in ET. Moreover, we identified a THPO splicing site mutation, MPL*636Wext*12, and MPL E237K. Four of the seven identified driver mutations were germline. Functional studies on MPL*636Wext*12 and MPL E237K revealed that they are gain-of-function mutants that increase MPL signaling and confer thrombopoietin hypersensitivity with very low efficiency. Patients with TN ET tended to be younger, although this was thought to be due to the inclusion of germline mutations, hereditary thrombocytosis. Accumulating the genetic and clinical characteristics of noncanonical mutations may help future clinical interventions in TN ET and hereditary thrombocytosis.

Clinical implementation of genetic testing in adults for hereditary hematologic malignancy syndromes

PURPOSE

As research on hereditary hematologic malignancy syndromes (HHMS) are accumulating, cancer genetics clinics are identifying more adult hematology patients with an inherited component to their disease. However, investigations for HHMS are complex, and there is no formal consensus on genetic testing criteria.

METHODS

We developed genetic testing criteria for adult hematology patients through a comprehensive literature review and our experience at the Princess Margaret Cancer Centre. We validated our criteria by applying them retrospectively to patients referred to our clinic for HHMS assessment.

RESULTS

Our genetic testing criteria are comprehensive of myeloid malignancies, lymphoid malignancies, and bone marrow failure, including age at diagnosis, family history, and genetic test results in blood and bone marrow. Of the 104 patients who met the criteria, 26% had at least 1 actionable variant in any gene associated with an increased risk of cancer and 13% had an actionable variant resulting in an HHMS diagnosis. A total of 15 patients had incidental findings, including 11 patients with a pathogenic variant associated with carrier status for an autosomal recessive disorder and 4 patients with a mosaic result.

CONCLUSION

Our high gene positivity rate shows the utility of a broad approach to germline testing in an adult hematology population.

CHST15 gene germline mutation is associated with the development of familial myeloproliferative neoplasms and higher transformation risk

Herein, we describe the clinical and hematological features of three genetically related families predisposed to myeloproliferative neoplasms (MPNs). Using whole-exome sequencing, we identified a c.1367delG mutation(p.Arg456fs) in CHST15 (NM_001270764), a gene encoding a type II transmembraneglycoproteinthat acts as a sulfotransferase and participates in the biosynthesis of chondroitin sulfate E, in germline and somatic cells in familial MPN. CHST15defects caused an increased JAK2V617F allele burden and upregulated p-Stat3 activity,leading to an increase in the proliferative and prodifferentiation potential of transgenic HEL cells. We demonstrated that mutant CHST15 is able to coimmmunoprecipitate the JAK2 protein,suggesting the presence of a CHST15-JAK2-Stat3 signaling axis in familial MPN. Gene expression profiling showed that the FREM1, IFI27 and C4B_2 genes are overexpressed in familial MPN, suggesting the activation of an "inflammatory response-extracellular matrix-immune regulation" signaling network in the CHST15 mutation background.We thus concluded that CHST15 is a novel gene that predisposes to familial MPN and increases the probability of disease development or transformation.

Haematological malignancies in relatives of patients affected with myeloproliferative neoplasms

In a cohort of 3131 patients with myeloproliferative neoplasms (MPNs), we identified 200 patients (6.4%) who reported a second case of haematological malignancies (HM) in first- or second-degree relatives. The occurrence of a second HM in the family was not influenced by MPN subtype, sex or driver mutation, while it was associated with age at MPN diagnosis: 8.5% of patients diagnosed with MPN younger than 45 years had a second relative affected with HM compared to 5.5% of those diagnosed at the age of 45 years or older (p = 0.003), thus suggesting a genetic predisposition to HM with early onset.

Molecular Pathogenesis of Myeloproliferative Neoplasms: From Molecular Landscape to Therapeutic Implications

Despite distinct clinical entities, the myeloproliferative neoplasms (MPN) share morphological similarities, propensity to thrombotic events and leukemic evolution, and a complex molecular pathogenesis. Well-known driver mutations, JAK2, MPL and CALR, determining constitutive activation of JAK-STAT signaling pathway are the hallmark of MPN pathogenesis. Recent data in MPN patients identified the presence of co-occurrence somatic mutations associated with epigenetic regulation, messenger RNA splicing, transcriptional mechanism, signal transduction, and DNA repair mechanism. The integration of genetic information within clinical setting is already improving patient management in terms of disease monitoring and prognostic information on disease progression. Even the current therapeutic approaches are limited in disease-modifying activity, the expanding insight into the genetic basis of MPN poses novel candidates for targeted therapeutic approaches. This review aims to explore the molecular landscape of MPN, providing a comprehensive overview of the role of drive mutations and additional mutations, their impact on pathogenesis as well as their prognostic value, and how they may have future implications in therapeutic management.

Familial essential thrombocythemia: 6 cases from a mono-institutional series

Rarely essential thrombocythemia (ET) is diagnosed in more than one person within a family. Familial myeloproliferative neoplasms are underdiagnosed. In this report, we describe 6 couples of familial ET, evaluating the heterogeneity of the mutational state and the clinical presentation.

Germline ATG2B/GSKIP-containing 14q32 duplication predisposes to early clonal hematopoiesis leading to myeloid neoplasms

The germline predisposition associated with the autosomal dominant inheritance of the 14q32 duplication implicating ATG2B/GSKIP genes is characterized by a wide clinical spectrum of myeloid neoplasms. We analyzed 12 asymptomatic carriers and 52 patients aged 18-74 years from six families, by targeted sequencing of 41 genes commonly mutated in myeloid malignancies. We found that 75% of healthy carriers displayed early clonal hematopoiesis mainly driven by TET2 mutations. Molecular landscapes of patients revealed two distinct routes of clonal expansion and leukemogenesis. The first route is characterized by the clonal dominance of myeloproliferative neoplasms (MPN)-driver events associated with TET2 mutations in half of cases and mutations affecting splicing and/or the RAS pathway in one-third of cases, leading to the early development of MPN, mostly essential thrombocythemia, with a high risk of transformation (50% after 10 years). The second route is distinguished by the absence of MPN-driver mutations and leads to AML without prior MPN. These patients mostly harbored a genomic landscape specific to acute myeloid leukemia secondary to myelodysplastic syndrome. An unexpected result was the total absence of DNMT3A mutations in this cohort. Our results suggest that the germline duplication constitutively mimics hematopoiesis aging by favoring TET2 clonal hematopoiesis.

Germline variants in DNA repair genes, including BRCA1/2, may cause familial myeloproliferative neoplasms

The molecular causes of myeloproliferative neoplasms (MPNs) have not yet been fully elucidated. Approximately 7% to 8% of the patients carry predisposing genetic germline variants that lead to driver mutations, which enhance JAK-STAT signaling. To identify additional predisposing genetic germline variants, we performed whole-exome sequencing in 5 families, each with parent-child or sibling pairs affected by MPNs and carrying the somatic JAK2 V617F mutation. In 4 families, we detected rare germline variants in known tumor predisposition genes of the DNA repair pathway, including the highly penetrant BRCA1 and BRCA2 genes. The identification of an underlying hereditary tumor predisposition is of major relevance for the individual patients as well as for their families in the context of therapeutic options and preventive care. Two patients with essential thrombocythemia or polycythemia vera experienced progression to acute myeloid leukemia, which may suggest a high risk of leukemic transformation in these familial MPNs. Our study demonstrates the relevance of genetic germline diagnostics in elucidating the causes of MPNs and suggests novel therapeutic options (eg, PARP inhibitors) in MPNs. Furthermore, we uncover a broader tumor spectrum upon the detection of a germline mutation in genes of the DNA repair pathway.

Novel germline mutation KMT2A G3131S confers genetic susceptibility to familial myeloproliferative neoplasms

The current study analyzed the clinical and genetic characteristics of a family with familial myeloproliferative neoplasms (MPNs). Whole-exome sequencing was conducted, and a germline heterozygous mutation in lysine methyltransferase 2A (KMT2A, also known as MLL1), G3131S (c.9391G > A, p.Gly3131Ser, rs150804738), was identified. Somatic DNA and germline DNA were collected from 8 family members, 120 healthy donors (somatic DNA), and 30 healthy donors (germline DNA). Using Sanger sequencing, the KMT2A G3131S mutation was analyzed. Four individuals, the proband (II-1), his sister (patient II-2), and family members II-3 and III-1 (somatic DNA and germline DNA), tested positive for the KMT2A G3131S mutation. We did not observe the KMT2A G3131S mutation in healthy donors (somatic DNA and germline DNA), indicating that this is not a SNP. Bioinformatics analysis of KMT2A G3131S suggested that protein structure changes could be caused by this mutation. To further elucidate the function of KMT2A G3131S, the CRISPR-Cas9 technique was applied to generate a KMT2A G3131S heterozygous K562 cell line. The colony formation potency, apoptosis, and cell cycle of KMT2A G3131S mutant K562 cells were analyzed. The results demonstrated that KMT2A G3131S mutant K562 cells showed increased proliferation and colony formation ability. Immunophenotyping was performed using flow cytometry to analyze the surface marker expression of gene-edited KMT2A G3131S mutant K562 cells. A significant increase in CD11b and mild increases in CD61 and CD235a were observed in KMT2A G3131S mutant K562 cells, suggesting that the KMT2A G3131S mutant could cause an increase in myeloproliferation. May-Giemsa staining showed that the morphological changes in KMT2A G3131S mutant K562 cells were consistent with the flow cytometry analysis. To verify which downstream genes were affected by the KMT2A G3131S mutant, we performed real-time PCR to evaluate the expression of previously reported KMT2A-related genes and found that C-MYB expression was significantly decreased. Western blotting was applied to investigate the expression of Kmt2a and C-myb proteins, and the results showed that in KMT2A G3131S mutant K562 cells, the expression of C-myb was decreased. Our findings suggested that KMT2A G3131S could affect the myeloproliferation of K562 cells and decrease C-myb expression. In conclusion, KMT2A G3131S could be considered a novel genetic susceptibility gene in familial MPN.

Molecular pathogenesis of the myeloproliferative neoplasms

The Philadelphia negative myeloproliferative neoplasms (MPN) compromise a heterogeneous group of clonal myeloid stem cell disorders comprising polycythaemia vera, essential thrombocythaemia and primary myelofibrosis. Despite distinct clinical entities, these disorders are linked by morphological similarities and propensity to thrombotic complications and leukaemic transformation. Current therapeutic options are limited in disease-modifying activity with a focus on the prevention of thrombus formation. Constitutive activation of the JAK/STAT signalling pathway is a hallmark of pathogenesis across the disease spectrum with driving mutations in JAK2, CALR and MPL identified in the majority of patients. Co-occurring somatic mutations in genes associated with epigenetic regulation, transcriptional control and splicing of RNA are variably but recurrently identified across the MPN disease spectrum, whilst epigenetic contributors to disease are increasingly recognised. The prognostic implications of one MPN diagnosis may significantly limit life expectancy, whilst another may have limited impact depending on the disease phenotype, genotype and other external factors. The genetic and clinical similarities and differences in these disorders have provided a unique opportunity to understand the relative contributions to MPN, myeloid and cancer biology generally from specific genetic and epigenetic changes. This review provides a comprehensive overview of the molecular pathophysiology of MPN exploring the role of driver mutations, co-occurring mutations, dysregulation of intrinsic cell signalling, epigenetic regulation and genetic predisposing factors highlighting important areas for future consideration.

Germline ERBB2/HER2 Coding Variants Are Associated with Increased Risk of Myeloproliferative Neoplasms

Familial cases of myeloproliferative neoplasms (MPN) are relatively common, yet few inherited risk factors have been identified. Exome sequencing of a kindred with a familial cancer syndrome characterized by both MPN and melanoma produced a germline variant in the ERBB2/HER2 gene that co-segregates with disease. To further investigate whether germline ERBB2 variants contribute to MPN predisposition, the frequency of ERBB2 variants was analyzed in 1604 cases that underwent evaluation for hematologic malignancy, including 236 cases of MPN. MPN cases had a higher frequency of rare germline ERBB2 coding variants compared to non-MPN hematologic malignancies (8.9% vs. 4.1%, OR 2.4, 95% CI: 1.4 to 4.0, p = 0.0028) as well as cases without a blood cancer diagnosis that served as an internal control (8.9% vs. 2.7%, OR 3.5, 95% CI: 1.4 to 8.3, p = 0.0053). This finding was validated via comparison to an independent control cohort of 1587 cases without selection for hematologic malignancy (8.9% in MPN cases vs. 5.2% in controls, p = 0.040). The most frequent variant identified, ERBB2 c.1960A > G; p.I654V, was present in MPN cases at more than twice its expected frequency. These data indicate that rare germline coding variants in ERBB2 are associated with an increased risk for development of MPN. The ERBB2 gene is a novel susceptibility locus which likely contributes to cancer risk in combination with additional risk alleles.

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Precision medicine in myeloid malignancies

Myeloid malignancies have always been at the forefront of an improved understanding of the molecular pathogenesis of cancer. In accordance, over the last years, basic research focusing on the aberrations underlying malignant transformation of myeloid cells has provided the basis for precision medicine approaches and subsequently has led to the development of powerful therapeutic strategies. In this review article, we will recapitulate what has happened since in the 1980s the use of all-trans retinoic acid (ATRA), as a first targeted cancer therapy, has changed one of the deadliest leukemia subtypes, acute promyelocytic leukemia (APL), into one that can be cured without classical chemotherapy today. Similarly, imatinib, the first molecularly designed cancer therapy, has revolutionized the management of chronic myeloid leukemia (CML). Thus, targeted treatment approaches have become the paradigm for myeloid malignancy, but many questions still remain unanswered, especially how identical mutations can be associated with different phenotypes. This might be linked to the impact of the cell of origin, gene-gene interactions, or the tumor microenvironment including the immune system. Continuous research in the field of myeloid neoplasia has started to unravel the molecular pathways that are not only crucial for initial treatment response, but also resistance of leukemia cells under therapy. Ongoing studies focusing on leukemia cell vulnerabilities do already point to novel (targetable) "Achilles heels" that can further improve myeloid cancer therapy.

Genetics of Myeloproliferative Neoplasms

Myeloproliferative neoplasms are hematopoietic stem cell disorders based on somatic mutations in JAK2, calreticulin, or MPL activating JAK-STAT signaling. Modern sequencing efforts have revealed the genomic landscape of myeloproliferative neoplasms with additional genetic alterations mainly in epigenetic modifiers and splicing factors. High molecular risk mutations with adverse outcomes have been identified and clonal evolution may promote progression to fibrosis and acute myeloid leukemia. JAK2V617F is recurrently detected in clonal hematopoiesis of indeterminate potential with increased risk for vascular events. Insights into the genetics of myeloproliferative neoplasms has facilitated diagnosis and prognostication and poses novel candidates for targeted therapeutic intervention.

Somatically acquired mutations in primary myelofibrosis: A case report and meta-analysis

Familial myeloproliferative disease (MPD) cases account for 7.6% of the global MPD cases. The present study reported 2 cases of primary myelofibrosis (PMF). The patients were two sisters; the older sister succumbed to the disease at the age of 37, whereas the younger sister maintained a stable disease status and gave birth to a son through in vitro fertilization. Genetic analysis of bone marrow DNA samples showed that both sisters carried a Janus kinase 2 (JAK2) V617F mutation, and the older sister also had a trisomy 8 chromosomal abnormality (47, XX, +8). A systematic literature search was also performed using PubMed, CNKI and Wanfang databases, to determine the association between JAK2 and PMF. Following comprehensive screening of the published literature, 19 studies were found to be eligible for the current meta-analysis. The results showed that JAK2 V617F was a risk factor of PMF, and no sex dimorphism was observed in JAK2 V617F mutation prevalence amongst all PMF cases. In addition, there was a lack of association between the JAK2 V617F mutation and PMF-related mortality.

Epidemiology of the Philadelphia Chromosome-Negative Classical Myeloproliferative Neoplasms

Polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) comprise the BCR-ABL-negative classical myeloproliferative neoplasms (MPNs). These clonal myeloid diseases are principally driven by well-described molecular events; however, factors leading to their acquisition are not well understood. Beyond increasing age, male sex, and race/ethnicity differences, few consistent risk factors for the MPNs are known. PV and ET have an incidence of 0.5 to 4.0 and 1.1 to 2.0 cases per 100,000 person-years, respectively, and predict similar survival. PMF, which has an incidence of about 0.3 to 2.0 cases per 100,000 person-years, is associated with the shortest survival of the MPNs.

Aetiology of Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) have estimated annual incidence rates for polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis of 0.84, 1.03, and 0.47 per 100,000. Prevalence is much higher, particularly for PV and ET, as mortality rates are relatively low. Patients are often concerned about why they developed an MPN and epidemiological studies enable the identification of potential causative factors. Previous work in small heterogeneous studies has identified a variety of risk factors associated with MPNs including family history of MPN, autoimmune conditions, some occupational exposures, and blood donation. At a population level, germline predisposition factors in various populations have been associated with MPNs. The pilot MOSAICC (Myeloproliferative Neoplasm: An In-depth Case-Control) study is one of the largest epidemiological studies in MPN ever carried out to date. It demonstrated the most effective methods for carrying out a significant epidemiological study in this patient group including the best way of recruiting controls, as well as how to evaluate occupational and lifestyle exposures, evaluate symptoms, and collect biological samples. Significant results linked to MPNs in the pilot study of 106 patients included smoking, obesity, and childhood socioeconomic status. The methodology is now in place for a much larger ongoing MOSAICC study which should provide further insight into the potential causes of MPNs.

Germline genetic factors in the pathogenesis of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal hematological malignancies that lead to overproduction of mature myeloid cells. They are due to acquired mutations in genes encoding for AK2, MPL and CALR that result in the activation of the cytokine receptor/JAK2 signaling pathway. In addition, it exists germline variants that can favor the initiation of the disease or may affect its phenotype. First, they can be common risk alleles, which correspond to frequent single nucleotide variants present in control population and that contribute to the development of either sporadic or familial MPN. Second, some variants predispose to the onset of MPN with a higher penetrance and lead to familial clustering of MPN. Finally, some extremely rare genetic variants can induce MPN-like hereditary disease. We will review these different subtypes of germline genetic variants and discuss how they impact the initiation and/or development of the MPN disease.

Epidemiology of the classical myeloproliferative neoplasms: The four corners of an expansive and complex map

The classical myeloproliferative neoplasms (MPNs), specifically chronic myeloid leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF), represent clonal myeloid disorders whose pathogenesis is driven by well-defined molecular abnormalities. In this comprehensive review, we summarize the epidemiological literature and present our own analysis of the most recent the Surveillance, Epidemiology, and End Results (SEER) program data through 2016. Older age and male gender are known risk factors for MPNs, but the potential etiological role of other variables is less established. The incidences of CML, PV, and ET are relatively similar at 1.0-2.0 per 100,000 person-years in the United States, while PMF is rarer with an incidence of 0.3 per 100,000 person-years. The availability of tyrosine kinase inhibitor therapy has dramatically improved CML patient outcomes and yield a life expectancy similar to the general population. Patients with PV or ET have better survival than PMF patients.

How we manage Philadelphia-negative myeloproliferative neoplasms in pregnancy

The combined incidence of classical Philadelphia-negative myeloproliferative neoplasm (MPN) is 6-9/100 000 with a peak frequency between 50 and 70 years. MPN is less frequent in women of reproductive age. However, for essential thrombocythaemia (ET) in particular there is a second peak in women of reproductive age and 15% of polycythaemia vera (PV) patients are less than 40 years of age at the time of diagnosis. Thus these diseases are encountered in women of reproductive potential and may be diagnosed in pregnancy or in women being investigated for recurrent pregnancy loss. The incidence of MPN pregnancies is 3·2/100 000 maternities per year in the UK. The majority of data regarding Philadelphia-negative MPNs relates to patients with ET, for which the literature suggests significant maternal morbidity and poor fetal outcome; specifically maternal thrombosis and haemorrhage, miscarriage, pre-eclampsia, intrauterine growth restriction (IUGR), stillbirth and premature delivery as summarised in the recent systematic review and meta-analysis in Blood, 2018, 132, 3046. The literature for PV is more sparse but increasing and is concordant with ET pregnancy outcomes. The literature regarding primary myelofibrosis (PMF) is even more scarce. Treatment options include aspirin, venesection, low molecular weight heparin (LMWH) and cytoreductive therapy. Data and management recommendations are often extrapolated from other pro-thrombotic conditions or from ET to PV and PMF. Women of reproductive age with a diagnosis of MPN should receive information and assurance regarding management and outcome of future pregnancies. From pre-conceptual planning to the post-partum period, women should have access to joint care from an obstetrician with experience of high-risk pregnancies and a haematologist in a multidisciplinary setting. This paper provides an update with regards to Philadelphia-negative MPN in pregnancy, details local practise in an internationally recognised centre for patients with MPN and outlines a future research strategy.

Recent insights regarding the molecular basis of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal disorders characterized by the overproduction of mature blood cells that have an increased risk of thrombosis and progression to acute myeloid leukemia. Next-generation sequencing studies have provided key insights regarding the molecular mechanisms of MPNs. MPN driver mutations in genes associated with the JAK-STAT pathway include JAK2 V617F, JAK2 exon 12 mutations and mutations in MPL, CALR, and CSF3R. Cooperating driver genes are also frequently detected and also mutated in other myeloid neoplasms; these driver genes are involved in epigenetic methylation, messenger RNA splicing, transcription regulation, and signal transduction. In addition, other genetic factors such as germline predisposition, order of mutation acquisition, and variant allele frequency also influence disease initiation and progression. This review summarizes the current understanding of the genetic basis of MPN, and demonstrates how molecular pathophysiology can improve both our understanding of MPN heterogeneity and clinical practice.

Diagnostic workflow for hereditary erythrocytosis and thrombocytosis

In the patient presenting with an elevated blood count who does not have an acquired clonal disorder causing a myeloproliferative neoplasm, hereditary erythrocytosis or hereditary thrombocytosis needs to be considered as a possible explanation. A young patient and/or those with a family history of myeloproliferative neoplasm should specifically raise this possibility. Among the causes of hereditary erythrocytosis are mutations in the genes in the oxygen sensing pathway and high-affinity hemoglobins. Hereditary thrombocytosis has been shown to be accounted for by mutations in THPO, MPL, and JAK2 genes. In those who have a possible hereditary erythrocytosis or thrombocytosis, the investigative pathway includes specific investigation to rule out the more common acquired clonal disorders, and, if indicated, other secondary causes, measurement of specific cytokines as indicated, and search for specific identified molecular lesions that have been shown to cause these hereditary disorders. There remain individuals who appear to have a hereditary disorder in whom a genetic lesion cannot currently be identified.

Hematological Malignancies in Adults With a Family Predisposition

BACKGROUND

Some hematological malignancies arise in persons with a hereditary predisposition. The hereditary nature of these diseases often goes unrecognized, particularly when symptoms begin in adulthood.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed.

RESULTS

Many rare germline mutations have been identified that lead to acute leukemia and myelodysplastic syndromes. They differ from one another with respect to their penetrance, the age of onset of disease, and the clinical manifestations. In view of this heterogeneity, no uniform recommendations have yet been formulated for their diagnosis and treatment. The most common types of hematological malig- nancy with a hereditary predisposition are traceable to an underlying disturbance of DNA damage response and repair mechanisms and to mutations of hematological transcription factors. With regard to the selection of patients for testing, the con- sensus is that cytogenetic and molecular-genetic findings that are suspect for a hereditary predisposition, such as CEBPA and RUNX1 mutations, call for further investigation, as do any clinical features that are typical of tumor syndromes, or a positive family history. The knowledge that a hereditary predisposition may be present is highly stressful for patients; testing should only be carried out after the patient has received genetic counseling. The confirmation of a germline mutation always requires a comparison with healthy tissue. A fibroblast culture is recom- mended as the gold standard for this purpose.

CONCLUSION

The detection of a hereditary predisposition to hematological neoplasia is often relevant to treatment and follow-up care: for example, it may motivate early allogeneic stem-cell transplantation. Counseling, predictive testing, and follow-up care are available to the patients' relatives as well.

Developments in diagnosis and treatment of essential thrombocythemia

INTRODUCTION

Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm characterized by thrombocytosis, increased risk of thrombotic/hemorrhagic events and clonal evolution into blast phase or myelofibrosis. Areas covered: The authors will discuss biology, diagnosis, prognosis, therapy, and outcome of ET. An accurate molecular-morphologic assessment is necessary in order to properly establish diagnosis and prognosis of ET. Stratification for thrombosis prediction is essential, and IPSET-t model is widely applied. The current treatment strategy is directed to lower the rate of vascular events using cytoreduction in patients at high risk. Prophylactic low dose aspirin indication is more uncertain. To date, therapies for patients who are resistant or intolerant to first-line treatments are scarce. Overall, life expectancy indicates an indolent disease, but IPSET model helps in predicting survival at the time of diagnosis. Expert opinion: Challenging for the future will be to share criteria for ET diagnosis with the community. New insights into the molecular pathogenesis of the disease will improve the prediction of clonal evolution and outcome, and lead to the use of disease-modifying treatments.

Inheritance of Susceptibility to Malignant Blood Disorders

Malignant blood disorders depend on heritable susceptibility genes and occur in familial aggregations. We suggest a model of transgenerational segregation of the susceptibility genes based on the study of malignant blood disorders in Norwegian and Danish families with unrelated parents, and in the inbred Faroese population with related parents. This model, consisting of parental genomic imprinting and mother-son microchimerism, can explain the male predominance in most of the diseases, the predominance of affected parent-offspring when parents are not related, and the different modes of segregation in males and females. The model displays a specific pattern in the distribution of affected relatives for each diagnosis, viz. a characteristic distribution in the pedigrees of family members with malignant blood disorder related to the proband. Three such patterns, each reflecting a specific transgenerational passage, were identified: (1) alterations in the number of affected relatives in paternal lines alone, e.g. in patterns for probands with multiple myeloma; (2) alterations in the number of affected relatives in both paternal and maternal lines for probands with chronic lymphocytic leukemia; and (3) no alterations in the numbers of male and female affected relatives in the parental lines, e.g. for probands with some types of malignant lymphoma.

Myeloproliferative Neoplasms in Danish Twins

OBJECTIVE

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of diseases characterized by clonal hyperproliferation of immature and mature cells of the myeloid lineage. Genetic differences have been proposed to play a role in the development of MPNs. Monozygotic twin pairs with MPNs have been reported in a few case reports, but the MPN concordance pattern in twins remains unknown.

METHOD

All twin pairs born in the period 1900-2010 were identified in the nationwide Danish Twin Registry. Only pairs with both twins alive on January 1, 1977, and those born thereafter were included to allow identification in the Danish National Patient Registry.

RESULTS

A total of 158 twin pairs were registered with an MPN diagnosis: 36 monozygotic, 104 dizygotic, and 18 pairs with unknown zygosity. MPNs were diagnosed in both twins in 4 pairs. The probandwise concordance rates for monozygotic twin pairs were higher than for dizygotic twin pairs (15 vs. 0%; p = 0.016).

CONCLUSION

An estimated concordance rate of 15% (95% CI 0.059-0.31) is modest, but given the rarity of MPNs this finding is clinically relevant and provides further support for the role of genetic predisposition in the development of MPNs.

The JAK2 GGCC (46/1) Haplotype in Myeloproliferative Neoplasms: Causal or Random?

The germline JAK2 haplotype known as “GGCC or 46/1 haplotype” (haplotype^GGCC_46/1) consists of a combination of single nucleotide polymorphisms (SNPs) mapping in a region of about 250 kb, extending from the JAK2 intron 10 to the Insulin-like 4 (INLS4) gene. Four main SNPs (rs3780367, rs10974944, rs12343867, and rs1159782) generating a “GGCC” combination are more frequently indicated to represent the JAK2 haplotype. These SNPs are inherited together and are frequently associated with the onset of myeloproliferative neoplasms (MPN) positive for both JAK2 V617 and exon 12 mutations. The association between the JAK2 haplotype^GGCC_46/1 and mutations in other genes, such as thrombopoietin receptor (MPL) and calreticulin (CALR), or the association with triple negative MPN, is still controversial. This review provides an overview of the frequency and the role of the JAK2 haplotype^GGCC_46/1 in the pathogenesis of different myeloid neoplasms and describes the hypothetical mechanisms at the basis of the association with JAK2 gene mutations. Moreover, possible clinical implications are discussed, as different papers reported contrasting data about the correlation between the JAK2 haplotype^GGCC_46/1 and blood cell count, survival, or disease progression.

Do we need antiplatelet therapy in thrombocytosis? Pro

Thrombocytosis (defined as platelets >450 × 109/l) has several aetiologies. After having excluded spurious thrombocytosis (e. g., due to microspherocytes, schistocytes, cryoglobulins, or bacteria), the differential diagnosis of true thrombocytosis encompasses secondary causes (as diverse as inflammation, infection, malignancy, iron deficiency, or asplenia), primary hereditary (rare forms of familial thrombocytosis) and primary acquired entities (either in the context of a myelodys-plastic syndrome or more frequently a myeloproliferative neoplasia). This manuscript addresses the following aspects: 1) diagnostic approach to thrombocytosis; 2) various mechanisms leading to a high platelet count; 3) potential of some of these mechanisms to modulate platelet function, producing hyper-reactive platelets and thus exerting a direct impact on the thrombotic risk; 4) indication of anti-thrombotic treatment in patients with thrombocytosis. There is a single prospective randomized clinical trial showing the benefit of acetyl-salicylic acid in polycythaemia vera. For other types of primary thrombocytosis and for secondary forms, treatment decisions have to be individualized according to the patient thrombotic and bleeding risks, taking into account the mechanism causing thrombocytosis. This manuscript discusses experimental and clinical data suggesting that besides patients with essential thrombocythaemia and other forms of primary thrombocytosis also those with thrombocytosis in the context of chronic inflammation, malignancy, or exposure to high altitude might benefit from anti-platelet treatment.

Buccal epithelial cells display somatic, bone marrow-derived CALR mutation

Buccal epithelial cells harbor an MPN-associated CALR mutation in a patient with CALR-mutant essential thrombocytosis, Ph⁺ CML, and no germ line CALR mutation.

Pathogenesis of Myeloproliferative Disorders

Myeloproliferative neoplasms (MPNs) are a set of chronic hematopoietic neoplasms with overlapping clinical and molecular features. Recent years have witnessed considerable advances in our understanding of their pathogenetic basis. Due to their protracted clinical course, the evolution to advanced hematological malignancies, and the accessibility of neoplastic tissue, the study of MPNs has provided a window into the earliest stages of tumorigenesis. With the discovery of mutations in CALR, the majority of MPN patients now bear an identifiable marker of clonal disease; however, the mechanism by which mutated CALR perturbs megakaryopoiesis is currently unresolved. We are beginning to understand better the role of JAK2(V617F) homozygosity, the function of comutations in epigenetic regulators and spliceosome components, and how these mutations cooperate with JAK2(V617F) to modulate MPN phenotype.

Genetic predisposition to hematologic malignancies: management and surveillance

As individuals with germ line predisposition to hematologic malignancies are diagnosed with increasing frequency, the need for clinical surveillance has become apparent. Unfortunately, few prospective data are available, so recommendations are based on collective experience and expert consensus. There is general agreement to advocate for expert consultation or referral of patients to centers with expertise in these syndromes, since presentations and disease progression can be subtle, and treatment strategies must be tailored. Here, we summarize and integrate expert consensus recommendations and medical management considerations for the patient newly diagnosed with a leukemia predisposition disorder. Indications to consider additional studies and referral for allogeneic stem cell transplantation are also discussed.

Advances in understanding the pathogenesis of familial myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are generally acquired as a result of a somatic stem cell mutation leading to clonal expansion of myeloid precursors. In addition to sporadic cases, familial MPN occurs when one or several MPN affect different relatives of the same family. MPN driver mutations (JAK2, CALR, MPL) are somatically acquired also in familial cases, so a genetic predisposition to acquire one of the MPN driver mutations would be inherited, even though the causative germline mutations underlying familial MPN remain largely unknown. Recently some germline variants [ATG2B and GSKIP duplication, RBBP6 mutations, SH2B3 (LNK) mutations], which can cause familial MPN, have been reported but these mutations are rare and do not explain most familial cases. Patients with familial MPN show the same clinical features and suffer the same complications as those with sporadic disease. This review aims to offer up-to-date information regarding the genetics of familial MPN.

Genomics of Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are a group of related clonal hematologic disorders characterized by excess accumulation of one or more myeloid cell lineages and a tendency to transform to acute myeloid leukemia. Deregulated JAK2 signaling has emerged as the central phenotypic driver of BCR -ABL1-negative MPNs and a unifying therapeutic target. In addition, MPNs show unexpected layers of genetic complexity, with multiple abnormalities associated with disease progression, interactions between inherited factors and phenotype driver mutations, and effects related to the order in which mutations are acquired. Although morphology and clinical laboratory analysis continue to play an important role in defining these conditions, genomic analysis is providing a platform for better disease definition, more accurate diagnosis, direction of therapy, and refined prognostication. There is an emerging consensus with regard to many prognostic factors, but there is a clear need to synthesize genomic findings into robust, clinically actionable and widely accepted scoring systems as well as the need to standardize the laboratory methodologies that are used.

Individualizing Care for Patients With Myeloproliferative Neoplasms: Integrating Genetics, Evolving Therapies, and Patient-Specific Disease Burden

Individualized medicine is important for patients with myeloproliferative neoplasms (MPNs), including essential thrombocythemia, polycythemia vera, and myelofibrosis, which are heterogeneous in terms of genetic mutation profile, prognosis, disease burden, and symptoms. Status of MPN driver mutations in JAK2, CALR, and MPL (or lack of one of these mutations) and other myeloid mutations (ASXL1, SRSF2, CBL, and IDH1/2, among others) affects diagnosis and prognosis. Management begins with estimating the prognosis, disease burden including MPN symptoms, and prevention of vascular events. Allogeneic stem cell transplantation is the definitive therapy in a subset of patients with myelofibrosis, the majority of whom receive JAK inhibition with ruxolitinib to relieve splenomegaly and symptoms and to prolong survival. Ruxolitinib is now a second-line therapy in polycythemia vera, with pegylated interferon being evaluated as a potential front-line therapy compared with hydroxyurea. The therapeutic landscape is evolving to include new JAK inhibitors, which may affect cytopenias (pacritinib and momelotinib), combination therapies including ruxolitinib, and novel targets such as pentraxin and telomerase. Assessing the therapeutic efficacy (including symptom impact) and toxicity of these new approaches is necessary to determine longitudinal management of MPNs in clinical practice and is a key component of "individualizing" care for patients with MPNs.

A TET2 rs3733609 C/T genotype is associated with predisposition to the myeloproliferative neoplasms harboring JAK2(V617F) and confers a proliferative potential on erythroid lineages

Common germline single-nucleotide polymorphisms (SNPs) at JAK2 locus have been associated with Myeloproliferative neoplasms (MPN). And, the germline sequence variant rs2736100 C in TERT is related to risk of MPN, suggesting a complex association between SNPs and the pathogenesis of MPN. Our previous study (unpublished data) showed that there was a high frequency distribution in rs3733609 C/T genotype at Ten-Eleven Translocation 2 (TET2) locus in one Chinese familial primary myelofibrosis. In the present study, we evaluate the role and clinical significance of rs3733609 C/T genotype in JAK2V617F-positive sporadic MPN (n = 181). TET2 rs3733609 C/T genotype had a higher incidence (13.81%; 25/181) in JAK2V617F-positive sporadic MPN patients than that in normal controls (n = 236) (6.35%; 15/236), which was predisposing to MPN (odds ratio(OR) = 2.361; P = 0.01). MPN patients with rs3733609 C/T genotype had increased leukocyte and platelets counts, elevated hemoglobin concentration in comparison with T/T genotype. Thrombotic events were more common in MPN patients with rs3733609 C/T than those with T/T genotype (P < 0.01). We confirmed that rs3733609 C/T genotype downregulated TET2 mRNA transcription, and the mechanism may be involved in a disruption of the interaction between CCAAT/enhancer binding protein alpha (C/EBPA) and TET2 rs3733609 C/T locus.TET2 rs3733609 C/T genotype stimulated the erythroid hematopoiesis in MPN patients. Altogether, we found a novel hereditary susceptible factor-TET2 rs3733609 C/T variant for the development of MPN, suggesting the variant may be partially responsible for the pathogenesis and accumulation of MPN.

Diagnosis, risk stratification, and response evaluation in classical myeloproliferative neoplasms

Philadelphia-negative classical myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues includes new criteria for the diagnosis of these disorders. Somatic mutations in the 3 driver genes, that is, JAK2, CALR, and MPL, represent major diagnostic criteria in combination with hematologic and morphological abnormalities. PV is characterized by erythrocytosis with suppressed endogenous erythropoietin production, bone marrow panmyelosis, and JAK2 mutation. Thrombocytosis, bone marrow megakaryocytic proliferation, and presence of JAK2, CALR, or MPL mutation are the main diagnostic criteria for ET. PMF is characterized by bone marrow megakaryocytic proliferation, reticulin and/or collagen fibrosis, and presence of JAK2, CALR, or MPL mutation. Prefibrotic myelofibrosis represents an early phase of myelofibrosis, and is characterized by granulocytic/megakaryocytic proliferation and lack of reticulin fibrosis in the bone marrow. The genomic landscape of MPNs is more complex than initially thought and involves several mutant genes beyond the 3 drivers. Comutated, myeloid tumor-suppressor genes contribute to phenotypic variability, phenotypic shifts, and progression to more aggressive disorders. Patients with myeloid neoplasms are at variable risk of vascular complications, including arterial or venous thrombosis and bleeding. Current prognostic models are mainly based on clinical and hematologic parameters, but innovative models that include genetic data are being developed for both clinical and trial settings. In perspective, molecular profiling of MPNs might also allow for accurate evaluation and monitoring of response to innovative drugs that target the mutant clone.

From leeches to personalized medicine: evolving concepts in the management of polycythemia vera

Polycythemia vera is a clonal disorder of hematopoietic stem/progenitor cells. It manifests as an expansion of red cell mass. It is the most common chronic myeloproliferative neoplasm. In virtually all cases, it is characterized by a V617F point mutation in JAK2 exon 14 or less common mutations in exon 12. The landmark discovery of the autonomously activated JAK/STAT signaling pathway paved the way for the clinical development of the first target drug, the JAK1 and JAK2 inhibitor ruxolitinib. This is now approved for patients with resistance or intolerance to hydroxyurea. Phlebotomies and hydroxyurea are still the cornerstone of treatment, and aim to prevent the first appearance or recurrence of cardiovascular events that, together with progression to post-polycythemia vera myelofibrosis and leukemia, represent the main causes of death. Interferon-α is an alternative drug and has been shown to induce molecular remissions. It is currently undergoing phase III trials that might eventually lead to its approval for clinical use. The last few years have witnessed important advances towards an accurate early diagnosis of polycythemia vera, greater understanding of its pathogenesis, and improved patient management. This review will focus on the most recent achievements and will aim to unify the different concepts involved in a personalized approach to the patient with polycythemia vera. In spite of many recent advances in the understanding of its pathogenesis and improved disease management, polycythemia vera remains a life-threatening myeloproliferative neoplasm for which there is no cure. This review will present a critical overview of evolving concepts in diagnosis and treatment of this disease.

How I treat essential thrombocythemia

Essential thrombocythemia (ET) is an indolent myeloproliferative neoplasm that may be complicated by vascular events, including both thrombosis and bleeding. This disorder may also transform into more aggressive myeloid neoplasms, in particular into myelofibrosis. The identification of somatic mutations of JAK2, CALR, or MPL, found in about 90% of patients, has considerably improved the diagnostic approach to this disorder. Genomic profiling also holds the potential to improve prognostication and, more generally, clinical decision-making because the different driver mutations are associated with distinct clinical features. Prevention of vascular events has been so far the main objective of therapy, and continues to be extremely important in the management of patients with ET. Low-dose aspirin and cytoreductive drugs can be administered to this purpose, with cytoreductive treatment being primarily given to patients at high risk of vascular complications. Currently used cytoreductive drugs include hydroxyurea, mainly used in older patients, and interferon α, primarily given to younger patients. There is a need for disease-modifying drugs that can eradicate clonal hematopoiesis and/or prevent progression to more aggressive myeloid neoplasms, especially in younger patients. In this article, we use a case-based discussion format to illustrate our approach to diagnosis and treatment of ET.

The expression of Death Inducer-Obliterator (DIDO) variants in Myeloproliferative Neoplasms

Chronic Myeloid Leukemia (CML), Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF) are Myeloproliferative Neoplasms (MPN) characterized by clonal myeloproliferation without cell maturation impairment. CML pathogenesis is associated with the Ph chromosome leading to BCR-ABL tyrosine-kinase constitutive expression. The Ph negative MPN (PV, ET and PMF) are characterized by the mutation JAK2(V617F) of the JAK2 protein in the auto-inhibitory JH2 domain, which is found in most PV patients and in approximately half of ET and PMF patients. Considerable effort is being made to understand the role of JAK2(V617F) at the MPN initiation and to clarify the pathogenesis and apoptosis resistance in CML, PV, ET and PMF patients. In the present investigation, we evaluated the Death Inducer-Obliterator (DIDO) (variants DIDO 1, 2 and 3) levels in CML, PV, ET and PMF patients. Our data reported the DIDO 1, 2 and 3 differential expressions in Myeloproliferative Neoplasms.

JAK2(V617I) results in cytokine hypersensitivity without causing an overt myeloproliferative disorder in a mouse transduction-transplantation model

A germline JAK2(V617I) point mutation results in hereditary thrombocytosis and shares some phenotypic features with myeloproliferative neoplasm, a hematologic malignancy associated with a somatically acquired JAK2(V617F) mutation. We established a mouse transduction-transplantation model of JAK2(V617I) that recapitulated the phenotype of humans with germline JAK2(V617I). We directly compared the phenotypes of JAK2(V617I) and JAK2(V617F) mice. The JAK2(V617I) mice had increased marrow cellularity with expanded myeloid progenitor and megakaryocyte populations, but this phenotype was less severe than that of JAK2(V617F) mice. JAK2(V617I) resulted in cytokine hyperresponsiveness without constitutive activation in the absence of ligand, whereas JAK2(V617F) resulted in constitutive activation. This may explain why JAK2(V617I) produces a mild myeloproliferative phenotype in the mouse model, as well as in humans with germline JAK2(V617I) mutations.