Genomic characterization in triple-negative primary myelofibrosis and other myeloid neoplasms with bone marrow fibrosis

Triple-Negative Myelofibrosis: Disease Features, Response to Treatment and Outcomes

BACKGROUND

Myelofibrosis is the most aggressive subtype among classical BCR::ABL1 negative myeloproliferative neoplasms. About 90% of cases are driven by constitutive activation of 1 of 3 genes impacting the JAK/STAT pathway: JAK2, CALR, and MPL. Triple-negative myelofibrosis (TN-MF) accounts for only 5%-10% of cases and carries the worst outcomes. Little has been described about this subset of disease. Given the marked heterogeneity surrounding disease biology, clonal architecture, clinical presentation, and poor outcomes in TN-MF, identification of features of interest and assessment of treatment response are areas in need of further investigation.

PATIENTS AND METHODS

We collected and evaluated baseline clinical and molecular parameters from 626 patients with a diagnosis of myelofibrosis who presented to the H. Lee Moffitt Cancer Center in Tampa (Florida, US) between 2003 and 2021 and compared them based on presence or absence of the three classical phenotypic driver mutations.

RESULTS

A small proportion of patients (6%) harbored TN-MF which correlated with inferior outcomes, marked by a 4-year reduction in overall survival time compared to the non-TN cohort (mOS 37.4 months vs. 85.7 months; P = .009) and higher rates of leukemic transformation. More pronounced thrombocytopenia and anemia, lower LDH, EPO levels, as well as lower percentage of marrow blasts at baseline were more commonly seen in TN-MF (P < .05). Similarly, patients with TN-MF had higher risk disease per DIPSS+ and GIPSS. Mutations impacting RNA splicing, epigenetic modification and signaling, specifically SRSF2, SETBP1, IDH2, CBL, and GNAS, were more commonly seen among those lacking a classical phenotypic driver. The prevalence of co-mutant ASXL1/SRSF2 clones was significantly higher in TN-MF as was trisomy 8. TN patients had fewer responses (46.2% vs. 63.4%) and shorter duration of response to ruxolitinib.

CONCLUSION

TN-MF is invariably associated with significantly decreased survival and more aggressive clinical behavior with higher rates of leukemic transformation and shorter duration of response to ruxolitinib. Mutations impacting RNA splicing, epigenetic modification and signaling (SRSF2, SETBP1, IDH2, CBL, and GNAS) are more common in TN-MF, which likely drive its aggressive course and may account for suboptimal responses to JAK inhibition.

Understanding triple negative myeloproliferative neoplasms: pathogenesis, clinical features, and management

ABSTRACTMyeloproliferative neoplasms (MPNs) that lack the classical "driver mutations," termed triple negative MPNs, remain a poorly understood entity. Despite considerable progress toward understanding MPN pathobiology, the mechanisms leading to the development of these MPNs remains inadequately elucidated. While triple negative primary myelofibrosis (TN-PMF) portends a poor prognosis, triple negative essential thrombocythemia (TN-ET) is more favorable as compared with JAK2 mutated ET. In this review, we summarize the clinical features and prognosis of TN-PMF and -ET as well as diagnostic challenges including identification of non-canonical driver mutations. We also discuss additional molecular drivers to better understand possible pathogenic mechanisms underlying triple negative MPNs. Finally, we highlight current therapeutic approaches as well as novel targets, particularly in the difficult to treat TN-PMF population.

Sequential gene expression analysis of myelodysplastic syndrome transformation identifies HOXB3 and HOXB7 as the novel targets for mesenchymal cells in disease

BACKGROUND

Myelodysplastic syndrome (MDS) is known to arise through the pathogenic bone marrow mesenchymal stem cells (MSC) by interacting with hematopoietic stem cells (HSC). However, due to the strong heterogeneity of MDS patients, it is difficult to find common targets in studies with limited sample sizes. This study aimed to describe sequential molecular changes and identify biomarkers in MSC of MDS transformation.

METHODS

Multidimensional data from three publicly available microarray and TCGA datasets were analyzed. MDS-MSC was further isolated and cultured in vitro to determine the potential diagnostic and prognostic value of the identified biomarkers.

RESULTS

We demonstrated that normal MSCs presented greater molecular homogeneity than MDS-MSC. Biological process (embryonic skeletal system morphogenesis and angiogenesis) and pathways (p53 and MAPK) were enriched according to the differential gene expression. Furthermore, we identified HOXB3 and HOXB7 as potential causative genes gradually upregulated during the normal-MDS-AML transition. Blocking the HOXB3 and HOXB7 in MSCs could enhance the cell proliferation and differentiation, inhibit cell apoptosis and restore the function that supports hematopoietic differentiation in HSCs.

CONCLUSION

Our comprehensive study of gene expression profiling has identified dysregulated genes and biological processes in MSCs during MDS. HOXB3 and HOXB7 are proposed as novel surrogate targets for therapeutic and diagnostic applications in MDS.

Idiopathic erythrocytosis: a germline disease?

Polycythemia Vera (PV) is typically caused by V617F or exon 12 JAK2 mutations. Little is known about Polycythemia cases where no JAK2 variants can be detected, and no other causes identified. This condition is defined as idiopathic erythrocytosis (IE). We evaluated clinical-laboratory parameters of a cohort of 56 IE patients and we determined their molecular profile at diagnosis with paired blood/buccal-DNA exome-sequencing coupled with a high-depth targeted OncoPanel to identify a possible underling germline or somatic cause. We demonstrated that most of our cohort (40/56: 71.4%) showed no evidence of clonal hematopoiesis, suggesting that IE is, in large part, a germline disorder. We identified 20 low mutation burden somatic variants (Variant allelic fraction, VAF, < 10%) in only 14 (25%) patients, principally involving DNMT3A and TET2. Only 2 patients presented high mutation burden somatic variants, involving DNMT3A, TET2, ASXL1 and WT1. We identified recurrent germline variants in 42 (75%) patients occurring mainly in JAK/STAT, Hypoxia and Iron metabolism pathways, among them: JAK3-V722I and HIF1A-P582S; a high fraction of patients (48.2%) resulted also mutated in homeostatic iron regulatory gene HFE-H63D or C282Y. By generating cellular models, we showed that JAK3-V722I causes activation of the JAK-STAT5 axis and upregulation of EPAS1/HIF2A, while HIF1A-P582S causes suppression of hepcidin mRNA synthesis, suggesting a major role for these variants in the onset of IE.

[A man in his forties with anaemia requiring transfusion]

BACKGROUND

While standard blood tests are often sufficient for an anaemia workup, sometimes more invasive diagnostic testing is required to exclude rare conditions.

CASE PRESENTATION

A man in his forties contacted his general practitioner because of increasing functional dyspnoea. He had completed a course of dicloxacillin a few months previously for a skin abscess on his abdomen. Bloodwork revealed severe anaemia (haemoglobin 5.4 g/dL), which required transfusion. Subsequent testing excluded iron and vitamin deficiency anaemia, haemolysis and malignancy. Initial bone marrow biopsy was of suboptimal quality. However, repeat tissue sample supported a diagnosis of pure red cell aplasia. The patient improved with ciclosporin treatment, which was gradually tapered.

INTERPRETATION

Pure red cell aplasia should be considered in patients with new onset isolated anaemia with severe reticulocytopenia. Diagnosis depends on obtaining representative tissue from bone marrow biopsy. It is difficult to conclude for this patient whether the aetiology of his pure red cell aplasia was idiopathic or secondary to recent dicloxacillin use.

Triple-Negative Primary Myelofibrosis: A Bone Marrow Pathology Group Study

Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm driven by canonical gene mutations in JAK2, CALR, or MPL in >80% of the cases. PMF that lacks these canonical alterations is termed triple-negative PMF (TN-PMF). The pathologic and genetic characteristics of TN-PMF compared with those of conventional PMF with canonical driver mutations (DM-PMF) have not been well studied. We aimed to identify clinicopathologic and molecular genetic differences between patients with TN-PMF (n = 56) and DM-PMF (n = 89), all of whom fulfilled the 2016 World Health Organization diagnostic criteria for PMF. Compared with the control group, patients in the TN-PMF group were more likely to have thrombocytopenia and less likely to have organomegaly. The bone marrow in patients with TN-PMF showed fewer granulocytic elements and more frequent dyserythropoiesis. Cytogenetic analysis showed a higher incidence of trisomy 8. Targeted next-generation sequencing revealed a lower frequency of ASXL1 mutations but enrichment of ASXL1/SRSF2 comutations. Our findings demonstrated several clinicopathologic and molecular differences between TN-PMF and DM-PMF. These findings, particularly the observed mutation profile characterized by a higher frequency of ASXL1 and SRSF2 comutation, suggest that at least a subset of TN-PMF may be pathogenetically different from DM-PMF, with potential prognostic implications.

Predictors of thrombosis and bleeding in 1613 myelofibrosis patients from the Spanish Registry of Myelofibrosis

Available data have proved insufficient to develop consensus recommendations on the prevention of thrombosis and bleeding in myelofibrosis (MF). We evaluated the incidence and risk factors of vascular complications in 1613 patients from the Spanish Myelofibrosis Registry. Over a total of 6981 patient-years at risk, 6.4% of the study population had at least one thrombotic event after MF diagnosis, amounting to an incidence rate of 1.65 per 100 patient-years. Prior history of thrombosis, the JAK2 mutation, and the intermediate-2/high-risk International Prognostic Scoring System (IPSS) categories conferred an increased thrombotic risk after adjustment for the risk-modifying effect of anti-thrombotic and cytoreductive treatments. History of thrombosis and the JAK2 mutation allowed us to pinpoint a group of patients at higher risk of early thrombosis. No decreased incidence of thrombosis was observed while patients were on anti-thrombotic or cytoreductive treatment. An increased risk of venous thrombosis was found during treatment with immunomodulatory agents. A total of 5.3% of patients had at least one episode of major bleeding, resulting in an incidence rate of 1.5 events per 100 patient-years. Patients in the intermediate-2/high-risk IPSS categories treated with anti-coagulants had an almost sevenfold increased risk of major bleeding. These findings should prove useful for guiding decision-making in clinical practice.

Molecular characterization of triple-negative myeloproliferative neoplasms by next-generation sequencing

The role of next-generation sequencing (NGS) in identifying mutations in the driver, epigenetic regulator, RNA splicing, and signaling pathway genes in myeloproliferative neoplasms (MPNs) has contributed substantially to our understanding of the disease pathogenesis as well as disease evolution. NGS aids in determining the clonal nature of the disease in a subset of these disorders where mutations in the driver genes are not detected. There is a paucity of real-world data on the utility of this test in the characterization of triple-negative myeloproliferative neoplasms (TN-MPN). In this study, 46 samples of TN-MPN (essential thrombocythemia (ET) = 17; primary myelofibrosis (PMF) = 23; & myeloproliferative neoplasm unclassified (MPN-u) = 6) were screened for markers of clonality using targeted NGS. Among these, 25 (54.3%) patients had mutations that would help determine the clonal nature of the disease. Eight of the 17 TN-ET (47%) and 13 of the 23 TN-PMF (56.5%) patients had noncanonical mutations in the driver genes and mutations in the genes involved in epigenetic regulation. Identification of mutations categorized as high molecular markers (HMR) in 2 patients helped classify them as PMF with high risk according to the MIPSS 70 scoring system. A novel mutation in the MPIG6B (C6orf25) gene associated with childhood myelofibrosis was detected in a 14-year-old girl. The presence of clonal hematopoiesis could be confirmed in four of the six MPN-u patients in this cohort. This study demonstrates the utility of NGS in improving the characterization of TN-MPN by establishing clonality and detecting noncanonical mutations in driver genes, thereby aiding in clinical decision-making.

How I Diagnose Primary Myelofibrosis

OBJECTIVES

Primary myelofibrosis (PMF) is a BCR/ABL1-negative myeloproliferative neoplasm (MPN) with a shorter overall survival and a higher leukemic transformation than other BCR/ABL1-negative MPNs. Diagnosis of PMF can be challenging given its clinical, morphologic, molecular overlap with other myeloid neoplasms also associated with myelofibrosis, and reactive conditions.

METHODS

We summarize and discuss the clinical, morphologic, and molecular features useful for diagnosing PMF as well as salient features helpful in distinguishing PMF from myelodysplastic syndrome with associated fibrosis and autoimmune myelofibrosis using a case-based approach.

RESULTS

PMF in both its prefibrotic and fibrotic stages, the latter characterized by reticulin/collagen marrow fibrosis, is characterized by a proliferation of predominantly abnormal megakaryocytes and granulocytes in the bone marrow. Driver mutations in   JAK2, CALR, or MPLare seen in approximately 90% of PMF cases. In triple-negative cases, the presence of cytogenetic abnormalities and other somatic mutations identified by next-generation sequencing can help establish a diagnosis of PMF in the appropriate clinical and morphologic context.

CONCLUSIONS

Given the significant difference in prognosis and treatment, integration of clinical, morphological, and molecular/genetic findings is essential in distinguishing PMF from other etiologies that can demonstrate myelofibrosis.

Next-generation sequencing in the diagnosis of non-cirrhotic splanchnic vein thrombosis

BACKGROUND & AIMS

Myeloproliferative neoplasms (MPNs) are the most frequent cause of non-tumoural non-cirrhotic splanchnic vein thrombosis (NC-SVT). Diagnosis of MPN is based on blood cell count alterations, bone marrow histology, and detection of specific gene mutations. Next-generation sequencing (NGS) allows the simultaneous evaluation of multiple genes implicated in myeloid clonal pathology. The aim of this study was to evaluate the potential role of NGS in elucidating the aetiology of NC-SVT.

METHODS

DNA samples from 80 patients (75 with idiopathic or exclusively local factor [Idiop/loc-NC-SVT] and 5 with MPN and NC-SVT [SVT-MPN] negative for Janus kinase 2 gene [JAK2] [V617F and exon 12], calreticulin gene [CALR], and thrombopoietin gene [MPL] mutations by classic techniques) were analysed by NGS. Mutations involved in myeloid disorders different from JAK2, CALR, and MPL genes were categorised as high-molecular-risk (HMR) variants or variants of unknown significance.

RESULTS

In 2/5 triple-negative SVT-MPN cases (40%), a mutation in exon 12 of JAK2 was identified. JAK2-exon 12 mutation was also identified in 1/75 patients with Idiop/loc-NC-SVT. Moreover, 28/74 (37.8%) of the remaining Idiop/loc-NC-SVT had at least 1 HMR variant. Sixty-two patients with Idiop/loc-NC-SVT were not receiving long-term anticoagulation and 5 of them (8.1%) had recurrent NC-SVT. This cumulative incidence was significantly higher in patients with HMR variants than in those without.

CONCLUSIONS

NGS identified JAK2-exon12 mutations not previously detected by conventional techniques. In addition, NGS detected HMR variants in approximately one-third of patients with Idiop/loc-NC-SVT. These patients seem to have a higher risk of splanchnic rethrombosis. NGS might be a useful diagnostic tool in NC-SVT.

LAY SUMMARY

Next-generation sequencing (NGS) performs massive sequencing of DNA allowing the simultaneous evaluation of multiple genes even at very low mutational levels. Application of this technique in a cohort of patients with non-cirrhotic non-tumoral portal vein thrombosis (NC-SVT) and a negative study for thrombophilic disorders was able to identify patients with a mutation in exon 12 not previously detected by conventional techniques. Moreover, NGS detected High Molecular Risk (HMR)-variants (Mutations involved in myeloid disorders different from JAK2, CALR and MPL genes) in approximately one third of patients. These patients appear to be at increased risk of rethrombosis. All these findings supports NGS as a potential useful tool in the management of NC-SVT.

Salvage Therapy Using Azacitidine for Relapsed Primary Myelofibrosis after Cord Blood Transplantation

We present the case of a 53-year-old woman with prefibrotic stage primary myelofibrosis (PMF) who underwent cord blood transplantation. Nine years after transplantation, she relapsed, which was confirmed by a bone marrow examination. We decided to treat her using azacitidine. After three courses of azacitidine, a partial cytogenetic response was confirmed. Azacitidine maintenance therapy successfully maintained a low level of recipient-origin peripheral blood cells with a stable hematological condition. Azacitidine may therefore be a promising therapeutic option for PMF patients who relapse after allogeneic stem cell transplantation.