Impact of gene mutations on treatment response and prognosis of acute myeloid leukemia secondary to myeloproliferative neoplasms

From regulation to deregulation of p53 in hematologic malignancies: implications for diagnosis, prognosis and therapy

The p53 protein, encoded by the TP53 gene, serves as a critical tumor suppressor, playing a vital role in maintaining genomic stability and regulating cellular responses to stress. Dysregulation of p53 is frequently observed in hematological malignancies, significantly impacting disease progression and patient outcomes. This review aims to examine the regulatory mechanisms of p53, the implications of TP53 mutations in various hematological cancers, and emerging therapeutic strategies targeting p53. We conducted a comprehensive literature review to synthesize recent findings related to p53's multifaceted role in hematologic cancers, focusing on its regulatory pathways and therapeutic potential. TP53 mutations in hematological malignancies often lead to treatment resistance and poor prognosis. Current therapeutic strategies, including p53 reactivation and gene therapy, show promise in improving treatment outcomes. Understanding the intricacies of p53 regulation and the consequences of its mutations is essential for developing effective diagnostic and therapeutic strategies in hematological malignancies, ultimately enhancing patient care and survival.

The role of TET2 in solid tumors and its therapeutic potential: a comprehensive review

Indeed, tumors are a significant health concern worldwide, and understanding the underlying mechanisms of tumor development is crucial for effective prevention and treatment. Epigenetics, which refers to changes in gene expression that are not caused by alterations in the DNA sequence itself, plays a critical role in the entire process of tumor development. It goes without saying that the effect of methylation on tumors is a significant aspect of epigenetics. Among the methylation modifications, DNA methylation is an important part, which plays a regulatory role in tumor-related genes. Ten-eleven translocation 2 (TET2) is a highly influential protein involved in the modification of DNA methylation. Its primary role is associated with the suppression of tumor development, making it a significant player in cancer research. However, TET2 is frequently mentioned in hematological diseases, its role in solid tumors has received little attention. Studying the changes of TET2 in solid tumors and the regulatory mechanism will facilitate its investigation as a clinical target for targeted therapy and may also provide directions for clinical treatment of malignant tumors.

Function of serine/arginine-rich splicing factors in hematopoiesis and hematopoietic malignancies

The serine/arginine-rich splicing factors (SRSFs) play an important role in regulating the alternative splicing of precursor RNA (pre-RNA). During this procedure, introns are removed from the pre-RNA, while the exons are accurately joined together to produce mature mRNA. In addition, SRSFs also involved in DNA replication and transcription, mRNA stability and nuclear export, and protein translation. It is reported that SRSFs participate in hematopoiesis, development, and other important biological process. They are also associated with the development of several diseases, particularly cancers. While the basic physiological functions and the important roles of SRSFs in solid cancer have been extensively reviewed, a comprehensive summary of their significant functions in normal hematopoiesis and hematopoietic malignancies is currently absent. Hence, this review presents a summary of their roles in normal hematopoiesis and hematopoietic malignancies.

Treatment approach and outcomes of patients with accelerated/blast-phase myeloproliferative neoplasms in the current era

ABSTRACT

Progression of myeloproliferative neoplasms (MPNs) to accelerated or blast phase is associated with poor survival outcomes. Since 2017 there have been several therapies approved for use in acute myeloid leukemia (AML); these therapies have been incorporated into the management of accelerated/blast-phase MPNs (MPN-AP/BP). We performed a multicenter analysis to investigate outcomes of patients diagnosed with MPN-AP/BP in 2017 or later. In total, 202 patients were identified; median overall survival (OS) was 0.86 years. We also analyzed patients based on first-line treatment; the 3 most common approaches were intensive chemotherapy (n = 65), DNA methyltransferase inhibitor (DNMTi)-based regimens (n = 65), and DNMTi + venetoclax-based regimens (n = 54). Median OS was not significantly different by treatment type. In addition, we evaluated response by 2017 European LeukemiaNet AML criteria and 2012 MPN-BP criteria in an effort to understand the association of response with survival outcomes. We also analyzed outcomes in 65 patients that received allogeneic hematopoietic stem cell transplant (allo-HSCT); median OS was 2.30 years from time of allo-HSCT. Our study demonstrates that survival among patients with MPN-AP/BP is limited in the absence of allo-HSCT even in the current era of therapeutics and underscores the urgent need for new agents and approaches.

Biological relevance of alternative splicing in hematologic malignancies

Alternative splicing (AS) is a strictly regulated process that generates multiple mRNA variants from a single gene, thus contributing to proteome diversity. Transcriptome-wide sequencing studies revealed networks of functionally coordinated splicing events, which produce isoforms with distinct or even opposing functions. To date, several mechanisms of AS are deregulated in leukemic cells, mainly due to mutations in splicing and/or epigenetic regulators and altered expression of splicing factors (SFs). In this review, we discuss aberrant splicing events induced by mutations affecting SFs (SF3B1, U2AF1, SRSR2, and ZRSR2), spliceosome components (PRPF8, LUC7L2, DDX41, and HNRNPH1), and epigenetic modulators (IDH1 and IDH2). Finally, we provide an extensive overview of the biological relevance of aberrant isoforms of genes involved in the regulation of apoptosis (e. g. BCL-X, MCL-1, FAS, and c-FLIP), activation of key cellular signaling pathways (CASP8, MAP3K7, and NOTCH2), and cell metabolism (PKM).

Genomic alterations in blast phase of BCR::ABL1-negative myeloproliferative neoplasms

The blast phase of BCR::ABL1-negative myeloproliferative neoplasm (MPN-BP) represents the final stage of the disease, which is complicated by complex genomic alterations. These alterations result from sequence changes in genetic material (DNA, RNA) and can lead to either a gain or loss of function of encoded proteins, such as adaptor proteins, enzymes, components of spliceosomes, cell cycle checkpoints regulators, transcription factors, or proteins in cell signaling pathways. Interference at various levels, including transcription, translation, and post-translational modification (such as methylation, dephosphorylation, or acetylation), can contribute to these alterations. Mutated genes such as ASXL1, EZH2, IDH1, IDH2, TET2, SRSF2, U2AF1, TP53, NRAS, KRAS, PTPN11, SH2B3/LNK, and RUNX1 play active roles at different stages of genetic material expression, modification, and protein function manipulation in MPNs. These mutations are also correlated with, and can contribute to, the progression of MPN-BP. In this review, we summarize their common mutational profiles, functions, and associations with progression of MPN-BP.

Efficacy and safety of combination therapies vs monotherapy of hypomethylating agents in accelerated or blast phase of Philadelphia negative myeloproliferative neoplasms: a systematic review and meta-analysis

BACKGROUND

There is a lack of evidence regarding whether combination therapy of hypomethylating agents (HMAs) has better outcomes than HMA monotherapy in patients with Philadelphia chromosome-negative accelerated or blast phase myeloproliferative neoplasms (MPN-AP/BP).

MATERIALS AND METHODS

Pubmed, Embase, Web of Science and Cochrane library databases were searched for studies from inception of each database until 31 December 2021. Data extraction and synthesis were conducted following the PRISMA reporting guideline.

RESULTS

It was found that HMAs plus venetoclax therapy yielded a higher CR/CRi rate than HMAs alone [36% vs 19%, p = .0204] and a higher CR rate than HMAs plus ruxolitinib [22% vs 8%, p = .0313]. HMAs plus ruxolitinib combination showed a higher ORR than HMA monotherapy [45% vs 30%, p = .0395], but there was no improvement in CR/CRi. The one-year and two-year OS rate for patients treated with HMAs plus venetoclx/ruxolitinib demonstrated a trend towards prolonged survival than HMAs alone [HMAs plus venetoclax: 24% vs 11%, p = .1295 and 12% vs 3%, p = .2357; HMAs plus ruxolitinib: 25% vs 11%, p = .0774 and 33% vs 3%, p = .051].

CONCLUSION

It was confirmed that HMA in combination with venetoclax is an effective and well-tolerated option in MPN-AP/BP patients in pre- as well as post-haematopoietic stem cell transplantation settings. HMA plus ruxolitinib therapy was revealed to be effective in patients with MPN-AP.Key MessagesCombination therapy with HMAs and venetoclax/ruxolitinib was associated with improved outcomes than HMAs alone in MPN-AP/BP patients.Further large-scale randomized controlled trials are needed to confirm regarding to the optimal treatment for this patient population.

The molecular profile in patients with polycythemia vera and essential thrombocythemia is dynamic and correlates with disease's phenotype

Introduction

Polycythemia vera (PV) and essential thrombocythemia (ET) are diseases driven by canonical mutations in JAK2, CALR, or MPL gene. Previous studies revealed that in addition to driver mutations, patients with PV and ET can harbor other mutations in various genes, with no established impact on disease phenotype. We hypothesized that the molecular profile of patients with PV and ET is dynamic throughout the disease.

Methods

In this study, we performed a 37-gene targeted next-generation sequencing panel on the DNA samples collected from 49 study participants in two-time points, separated by 78-141 months. We identified 78 variants across 37 analyzed genes in the study population.

Results

By analyzing the change in variant allele frequencies and revealing the acquisition of new mutations during the disease, we confirmed the dynamic nature of the molecular profile of patients with PV and ET. We found connections between specific variants with the development of secondary myelofibrosis, thrombotic events, and response to treatment. We confronted our results with existing conventional and mutation-enhanced prognostic systems, showing the limited utility of available prognostic tools.

Discussion

The results of this study underline the significance of repeated molecular testing in patients with PV and ET and indicate the need for further research within this field to better understand the disease and improve available prognostic tools.

PHF5A as a new OncoTarget and therapeutic prospects

PHF5A (PHD-finger domain protein 5A) is a highly conserved protein comprised of 110 amino acids that belong to PHD zinc finger proteins and is ubiquitously expressed in entire eukaryotic nuclei from yeast to man. PHF5A is an essential component of the SF3B splicing complex regulating protein-protein or protein-DNA interactions; particularly involved in pre-mRNA splicing. Besides its basic spliceosome-associated attributes encompassing the regulation of alternative splicing of specific genes, PHF5A also plays a pivotal role in cell cycle regulation and morphological development of cells along with their differentiation into particular tissues/organs, DNA damage repair, maintenance of pluripotent embryonic stem cells (CSCs) embryogenesis and regulation of chromatin-mediated transcription. Presently identification of spliceosome and non-spliceosome-associated attributes of PHF5A needs great attention based on its key involvement in the pathogenesis of cancer malignancies including the prognosis of lung adenocarcinoma, endometrial adenocarcinoma, breast, and colorectal cancer. PHF5A is an essential splicing factor or cofactor actively participating as an oncogenic protein in tumorigenesis via activation of downstream signaling pathway attributed to its regulation of dysregulated splicing or abnormal alternative splicing of targeted genes. Further, the participation of PHF5A in regulating the growth of cancer stem cells might not be ignored. The current review briefly overviews the structural and functional attributes of PHF5A along with its hitherto described role in the propagation of cancer malignancies and its future concern as a potential therapeutic target for cancer management/treatment.

Gene mutation analysis using next-generation sequencing and its clinical significance in patients with myeloid neoplasm: A multi-center study from China

BACKGROUND

Myeloid neoplasms (MN) tend to relapse and deteriorate. Exploring the genomic mutation landscape of MN using next-generation sequencing (NGS) is a great measure to clarify the mechanism of oncogenesis and progression of MN.

METHODS

This multicenter retrospective study investigated 303 patients with MN using NGS from 2019 to 2021. The characteristics of the mutation landscape in the MN subgroups and the clinical value of gene variants were analyzed.

RESULTS

At least one mutation was detected in 88.11% of the patients (267/303). TET2 was the most common mutation in the cohort, followed by GATA2, ASXL1, FLT3, DNMT3A, and TP53. Among patients with myeloid leukemia (ML), multivariate analysis showed that patients aged ≥60 years had lower overall survival (OS, p = 0.004). Further analysis showed TET2, NPM1, SRSF2, and IDH1 gene mutations, and epigenetic genes (p < 0.050) presented significantly higher frequency in older patients. In patients with myelodysplastic syndrome (MDS) and myelodysplastic neoplasms (MPN), univariate analysis showed that BCORL1 had a significant impact on OS (p = 0.040); however, in multivariate analysis, there were no factors significantly associated with OS. Differential analysis of genetic mutations showed FLT3, TP53, MUC16, SRSF2, and KDM5A mutated more frequently (p < 0.050) in secondary acute myeloid leukemia (s-AML) than in MDS and MPN. TP53, U2AF1, SRSF2, and KDM5A were mutated more frequently (p < 0.050) in s-AML than in primary AML. KDM5A was observed to be restricted to patients with s-AML in this study, and only co-occurred with MUC16 and TP53 (2/2, 100%). Another mutation was MUC16, and its co-occurrence pattern differed between s-AML and AML. MUC16 mutations co-occurred with KDM5A and TP53 in 66.7% (2/3) of patients with s-AML and co-occurred with CEBPA in 100% (4/4) of patients with AML.

CONCLUSIONS

Our results demonstrate different genomic mutation patterns in the MN subgroups and highlight the clinical value of genetic variants.

Venetoclax in combination with hypomethylating agent for the treatment of advanced myeloproliferative neoplasms and acute myeloid leukemia with extramedullary disease

The combination of venetoclax and hypomethylating agent (HMA/venetoclax) has emerged as a treatment option for patients with de novo acute myeloid leukemia (AML) who are unfit to receive intensive chemotherapy. In this single-center retrospective study, we evaluated clinical outcomes following treatment with HMA/venetoclax in 35 patients with advanced myeloproliferative neoplasms, myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes or AML with extramedullary disease. The composite complete remission (CR) rate (including confirmed/presumed complete cytogenetic response, acute leukemia response-complete, CR and CR with incomplete hematologic recovery) was 42.9% with median overall survival (OS) of 9.7 months. Complex karyotype was associated with inferior median OS (3.7 versus 12.2 months; p = 0.0002) and composite CR rate (22% versus 50.0%; p = 0.2444). Although SRSF2 mutations were associated with higher composite CR rate (80.0% versus 28.0%; p = 0.0082), this was not associated with longer median OS (10.9 versus 8.0 months; p = 0.2269). Future studies should include these patient subgroups.

Targeted Therapy for MPNs: Going Beyond JAK Inhibitors

PURPOSE OF REVIEW

JAK inhibition is an effective means of controlling symptom burden and improving splenomegaly in patients with myeloproliferative neoplasms (MPNs). However, a majority of patients treated with JAK inhibition will have disease progression with long-term use. In In this review, we focus on the investigation of novel targeted agents beyond JAK inhibitors both in the chronic phase of disease and in the accelerated/blast phase of disease.

RECENT FINDINGS

Relevant targeted therapies in MPNs include BET inhibitors, BCL inhibitors, LSD1 inhibitors, PI3K inhibitors, IDH inhibitors, telomerase inhibitors, and MDM2 inhibitor. Agents within these classes have been investigated either as monotherapy or in combination with a JAK inhibitor. We summarize the prospective data for these agents along with detailing the ongoing phase III trials incorporating these agents. While JAK inhibition has been a mainstay of therapy in MPNs, a majority of patients will have disease of progression. JAK inhibitors also have limited anti-clonal effect and do not impact the rate of progression to the blast phase of disease. The novel therapies detailed in this review not only show promise in ameliorating the symptom burden of MPNs but may be able to alter the natural history of disease.

SOHO State of the Art Updates and Next Questions | Accelerated Phase of MPN: What It Is and What to Do About It

Progression of Philadelphia-chromosome negative myeloproliferative neoplasms (MPNs) to the accelerated phase (AP) or blast phase (BP) is associated with poor outcomes. As our understanding of the molecular drivers of MPN progression has grown, there has been increasing investigation into the use of novel targeted approaches in the treatment of these diseases. In this review we summarize the clinical and molecular risk factors for progression to MPN-AP/BP followed by discussion of treatment approach. We also highlight outcomes using conventional approaches such as intensive chemotherapy and hypomethylating agents along with considerations around allogeneic hematopoietic stem cell transplant. We then focus on novel targeted approaches in MPN-AP/BP including venetoclax-based regimens, IDH inhibition, and ongoing prospective clinical trials.

Impact of Molecular Biology in Diagnosis, Prognosis, and Therapeutic Management of BCR::ABL1-Negative Myeloproliferative Neoplasm

BCR::ABL1-negative myeloproliferative neoplasms (MPNs) include three major subgroups-polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF)-which are characterized by aberrant hematopoietic proliferation with an increased risk of leukemic transformation. Besides the driver mutations, which are JAK2, CALR, and MPL, more than twenty additional mutations have been identified through the use of next-generation sequencing (NGS), which can be involved with pathways that regulate epigenetic modifications, RNA splicing, or DNA repair. The aim of this short review is to highlight the impact of molecular biology on the diagnosis, prognosis, and therapeutic management of patients with PV, ET, and PMF.

Novel Molecular Insights into Leukemic Evolution of Myeloproliferative Neoplasms: A Single Cell Perspective

Myeloproliferative neoplasms (MPNs) are clonal disorders originated by the serial acquisition of somatic mutations in hematopoietic stem/progenitor cells. The major clinical entities are represented by polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), that are caused by driver mutations affecting JAK2, MPL or CALR. Disease progression is related to molecular and clonal evolution. PV and ET can progress to secondary myelofibrosis (sMF) but can also evolve to secondary acute myeloid leukemia (sAML). PMF is associated with the highest frequency of leukemic transformation, which represents the main cause of death. sAML is associated with a dismal prognosis and clinical features that differ from those of de novo AML. The molecular landscape distinguishes sAML from de novo AML, since the most frequent hits involve TP53, epigenetic regulators, spliceosome modulators or signal transduction genes. Single cell genomic studies provide novel and accurate information about clonal architecture and mutation acquisition order, allowing the reconstruction of clonal dynamics and molecular events that accompany leukemic transformation. In this review, we examine our current understanding of the genomic heterogeneity in MPNs and how it affects disease progression and leukemic transformation. We focus on molecular events elicited by somatic mutations acquisition and discuss the emerging findings coming from single cell studies.

Acute Myeloid Leukemia Following Myeloproliferative Neoplasms: A Review of What We Know, What We Do Not Know, and Emerging Treatment Strategies

Acute myeloid leukemia (AML) arising from myeloproliferative neoplasms (MPNs) represents a small subtype of secondary AML (sAML). This entity is well known to be associated with poor responses to available treatment options and dismal outcomes. To date, there are no standardized treatment options and there has been very little therapeutic advancement in recent years. This is a stark contrast to other subsets of AML for which there have been significant advances in therapeutic approaches, especially for patients with targetable mutations. We aim to focus our review on the incidence, risk factors for leukemogenesis, pathogenesis, molecular landscape, and emerging therapeutic options in post-myeloproliferative neoplasm acute myeloid leukemia (post-MPN AML).

Comparison of Different Treatment Strategies for Blast-Phase Myeloproliferative Neoplasms

INTRODUCTION

Up to 20% of patients with myeloproliferative neoplasms (MPN) will progress to blast phase (MPN-BP). Outcomes are dismal, with intensive chemotherapy providing little benefit. Low-intensity therapy is preferred due to better tolerability, but the prognosis remains poor. Allogeneic stem cell transplant (AHSCT) is still the only potential for long term survival.

PATIENTS AND METHODS

To better evaluate the initial treatment approach in MPN-BP, we performed a single-institution retrospective analysis of 75 patients with MPN-BP treated at Moffitt Cancer Center between 2001 and 2021. Patients were stratified by initial treatment: best supportive care (BSC), hypomethylating agent (HMA)-based therapy or intensive chemotherapy (IC).

RESULTS

Median overall survival (mOS) for the entire cohort was 4.8 months (BSC 0.8 months, HMA 4.7 months, and IC 11.4 months). Among IC patients, improved survival was evident in those that received AHSCT (mOS 40.8 months vs. 4.9 months, p < .01). Most patients that underwent AHSCT were initially treated with IC (p < .01). All patients that underwent AHSCT had achieved complete response (CR) or CR with incomplete hematological recovery (CRi). On multivariate analysis, factors associated with improved survival were receipt of therapy (HMA or IC) (P = .017), CR/CRi (P = .037) and receipt of AHSCT (p < .001).

CONCLUSION

We show that active treatment with IC improves survival, but it is mostly tied to receipt of AHSCT. IC is a reasonable approach in appropriate patients as it can provide an effective bridge to AHSCT. Other treatment strategies such as molecularly targeted therapy and novel agents are desperately needed.

Clinical features and next-generation sequencing landscape of essential thrombocythemia, prefibrotic primary myelofibrosis, and overt fibrotic primary myelofibrosis: a Chinese monocentric retrospective study

OBJECTIVE

Since prefibrotic primary myelofibrosis (pre-PMF) was recognized as a separate entity in the 2016 revised classification of MPN differed from essential thrombocythemia (ET) or overt fibrotic primary myelofibrosis (overt PMF), it has been a subject of debate among experts due to its indefinite diagnosis.

METHODS

We retrospectively reviewed the clinical parameters, haematologic information, and genetic mutations of patients who were diagnosed with myeloproliferative neoplasms (MPNs) according to the WHO 2016 criteria in China, including 56 ET patients, 19 pre-PMF patients, and 43 overt PMF patients.

RESULTS

Pre-PMF patients exhibited higher leukocyte counts [14.2(6.0-28.1) × 10⁹/L vs 9.6(4.0-55.0) × 10⁹/L, P = 0.003], LDH values [307(233-479)U/L vs 241(129-1182)U/L, P < 0.001], onset ages [67(32-76) years vs 50(16-79) years, P = 0.006], a higher frequency of splenomegaly(47.4% vs 16.7%, P = 0.018) and hypertension (57.9 vs 23.2%, P = 0.005) than ET patients. On the other hand, pre-PMF patients had higher platelet counts [960(500-2245) × 10⁹/L vs 633(102-1720) × 10⁹/L, P = 0.017], haemoglobin levels [152(115-174)g/L vs 119(71-200)g/L, P = 0.003], lower LDH values [307(233-479)U/L vs 439(134-8100)U/L, P = 0.007] and a lower frequency of splenomegaly(47.4 vs 75.6%, P = 0.031) than overt PMF patients. Next-generation sequencing landscape was performed in 50 patients, revealed the frequency of EP300 mutations was significantly increased in pre-PMF patients compared with ET and overt PMF patients (60 vs 10 vs 15.79%, P = 0.033), and WT1 was more often overexpressed (WT1/ABL1 copies ≥ 1.0%) in patients with overt PMF than in those with ET or pre-PMF(54.55 vs 16.67 vs 17.65%, P = 0.009). In terms of outcome, male sex, along with symptoms including MPN10, anaemia (haemoglobin < 120 g/L), thrombocytopenia (platelet count < 100 × 10⁹/L), leucocytosis (leukocyte counts > 13 × 10⁹/L), high LDH value (> 350U/L), splenomegaly, WT1 overexpression(WT1/ABL1 copies ≥ 1.0%), KMT2A, ASXL1 and TP53 mutations, indicated a poor prognosis for PMF patients.

CONCLUSION

The results of this study indicated that a comprehensive evaluation of BM features, clinical phenotypes, haematologic parameters, and molecular profiles is needed for the accurate diagnosis and treatment of ET, pre-PMF, and overt PMF patients.

Mutational landscape of blast phase myeloproliferative neoplasms (MPN-BP) and antecedent MPN

Myeloproliferative neoplasms (MPN) have an inherent tendency to evolve to the blast phase (BP), characterized by ≥20% myeloblasts in the blood or bone marrow. MPN-BP portends a dismal prognosis and currently, effective treatment modalities are scarce, except for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in selected patients, particularly those who achieve complete/partial remission. The mutational landscape of MPN-BP differs from de novo acute myeloid leukemia (AML) in several key aspects, such as significantly lower frequencies of FLT3 and DNMT3A mutations, and higher incidence of IDH1/2 and TP53 in MPN-BP. Herein, we comprehensively review the impact of the three signaling driver mutations (JAK2 V617F, CALR exon 9 indels, MPL W515K/L) that constitutively activate the JAK/STAT pathway, and of the other somatic non-driver mutations (epigenetic, mRNA splicing, transcriptional regulators, and mutations in signal transduction genes) that cooperatively or independently promote MPN progression and leukemic transformation. The MPN subtype, harboring two or more high-molecular risk (HMR) mutations (epigenetic regulators and mRNA splicing factors) and "triple-negative" PMF are among the critical factors that increase risk of leukemic transformation and shorten survival. Primary myelofibrosis (PMF) is the most aggressive MPN; and polycythemia vera (PV) and essential thrombocythemia (ET) are relatively indolent subtypes. In PV and ET, mutations in splicing factor genes are associated with progression to myelofibrosis (MF), and in ET, TP53 mutations predict risk for leukemic transformation. The advent of targeted next-generation sequencing and improved prognostic scoring systems for PMF inform decisions regarding allo-HSCT. The emergence of treatments targeting mutant enzymes (e.g., IDH1/2 inhibitors) or epigenetic pathways (BET and LSD1 inhibitors) along with new insights into the mechanisms of leukemogenesis will hopefully lead the way to superior management strategies and outcomes of MPN-BP patients.

Can molecular insights guide treatment of AML evolved from MPNs?

Leukemic transformation of myeloproliferative neoplasms (MPNs) is associated with dismal outcomes. The genetic complexity of leukemic transformation of MPNs is being deciphered and will likely result in targeted therapy approaches. Ongoing trials are investigating the efficacy of emerging treatments for this high-risk patient population. This review has outlined recent progress in the understanding and treatment of leukemia arising from MPNs.

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs): A continuum of different disease entities

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells and close pathobiologic and clinical features. According to the 2016 World Health Organization (WHO) classification, MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision aimed in particular at strengthening the distinction between masked PV and JAK2-mutated ET, and between prefibrotic/early (pre-PMF) and overt PMF. Clinical manifestations in MPNs include constitutional symptoms, microvascular disorders, thrombosis and bleeding, splenomegaly secondary to extramedullary hematopoiesis, cytopenia-related symptoms, and progression to overt MF and acute leukemia. A dysregulation of the JAK/STAT pathway is the unifying mechanistic hallmark of MPNs, and is guided by somatic mutations in driver genes including JAK2, CALR and MPL. Additional mutations in myeloid neoplasm-associated genes have been also identified, with established prognostic relevance, particularly in PMF. Prognostication of MPN patients relies on disease-specific clinical models. The increasing knowledge of MPN biology led to the development of integrated clinical and molecular prognostic scores that allow a more refined stratification. Recently, the therapeutic landscape of MPNs has been revolutionized by the introduction of potent, selective JAK inhibitors (ruxolitinib, fedratinib), that proved effective in controlling disease-related symptoms and splenomegaly, yet leaving unmet critical needs, owing the lack of disease-modifying activity. In this review, we will deal with molecular, clinical, and therapeutic aspects of the three classical MPNs aiming at highlighting either shared characteristics, that overall define a continuum within a single disease family, and uniqueness, at the same time.

Integration of Molecular Information in Risk Assessment of Patients with Myeloproliferative Neoplasms

Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) are clonal disorders of a hematopoietic stem cell, characterized by an abnormal proliferation of largely mature cells driven by mutations in JAK2, CALR, and MPL. All these mutations lead to a constitutive activation of the JAK-STAT signaling, which represents a target for therapy. Beyond driver ones, most patients, especially with myelofibrosis, harbor mutations in an array of "myeloid neoplasm-associated" genes that encode for proteins involved in chromatin modification and DNA methylation, RNA splicing, transcription regulation, and oncogenes. These additional mutations often arise in the context of clonal hematopoiesis of indeterminate potential (CHIP). The extensive characterization of the pathologic genome associated with MPN highlighted selected driver and non-driver mutations for their clinical informativeness. First, driver mutations are enlisted in the WHO classification as major diagnostic criteria and may be used for monitoring of residual disease after transplantation and response to treatment. Second, mutation profile can be used, eventually in combination with cytogenetic, histopathologic, hematologic, and clinical variables, to risk stratify patients regarding thrombosis, overall survival, and rate of transformation to secondary leukemia. This review outlines the molecular landscape of MPN and critically interprets current information for their potential impact on patient management.

Genetic factors rather than blast reduction determine outcomes of allogeneic HCT in BCR-ABL-negative MPN in blast phase

There is a limited understanding of the clinical and molecular factors associated with outcomes of hematopoietic cell transplantation (HCT) in patients with BCR-ABL-negative myeloproliferative neoplasms in blast phase (MPN-BP). Using the Center for International Blood and Marrow Transplant Research database, we evaluated HCT outcomes in 177 patients with MPN-BP. Ninety-five (54%) had sufficient DNA for targeted next-generation sequencing of 49 genes clinically relevant in hematologic malignancies. At 5 years, overall survival (OS), cumulative incidence of relapse, and nonrelapse mortality of the study cohort was 18%, 61%, and 25%, respectively. In a multivariable model, poor-risk cytogenetics was associated with inferior OS (hazard ratio [HR], 1.71; 95% CI, 1.21-2.41) due to increased relapse (HR, 1.93; 95% CI, 1.32-2.82). Transplants using mobilized peripheral blood (PB) were associated with better OS (HR, 0.60; 95% CI, 0.38-0.96). No difference in outcomes was observed in patients undergoing HCT with PB/BM blasts <5% vs those with active leukemia. Among the 95 patients with molecular data, mutation of TP53, present in 23%, was the only genetic alteration associated with outcomes. In a multivariate model, TP53-mutant patients had inferior OS (HR, 1.99; 95% CI, 1.14-3.49) and increased incidence of relapse (HR, 2.59; 95% CI, 1.41-4.74). There were no differences in the spectrum of gene mutations, number of mutations, or variant allele frequency between patients undergoing HCT with PB/BM blasts <5% vs those with active leukemia. Genetic factors, namely cytogenetic alterations and TP53 mutation status, rather than degree of cytoreduction predict outcomes of HCT in MPN-BP. No meaningful benefit of conventional HCT was observed in patients with MPN-BP and mutated TP53.

Leukemic evolution of polycythemia vera and essential thrombocythemia: genomic profiles predict time to transformation

Among myeloproliferative neoplasms, polycythemia vera (PV) and essential thrombocythemia (ET) are the 2 entities associated with the most chronic disease course. Leukemic evolution occurs rarely but has a grim prognosis. The interval between diagnosis and leukemic evolution is highly variable, from a few years to >20 years. We performed a molecular evaluation of 49 leukemic transformations of PV and ET by targeted next-generation sequencing. Using a hierarchical classification, we identified 3 molecular groups associated with a distinct time to leukemic transformation. Short-term transformations were mostly characterized by a complex molecular landscape and mutations in IDH1/2, RUNX1, and U2AF1 genes, whereas long-term transformations were associated with mutations in TP53, NRAS, and BCORL1 genes. Studying paired samples from chronic phase and transformation, we detected some mutations already present during the chronic phase, either with a significant allele burden (short-term transformation) or with a very low allele burden (especially TP53 mutations). However, other mutations were not detected even 1 year before leukemic transformation. Our results suggest that the leukemic transformation of PV and ET may be driven by distinct time-dependent molecular mechanisms.

Accelerated Phase of Myeloproliferative Neoplasms

BACKGROUND

Myeloproliferative neoplasms (MPNs) can transform into blast phase MPN (leukemic transformation; MPN-BP), typically via accelerated phase MPN (MPN-AP), in ∼20-25% of the cases. MPN-AP and MPN-BP are characterized by 10-19% and ≥20% blasts, respectively. MPN-AP/BP portend a dismal prognosis with no established conventional treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole modality associated with long-term survival.

SUMMARY

MPN-AP/BP has a markedly different mutational profile from de novo acute myeloid leukemia (AML). In MPN-AP/BP, TP53 and IDH1/2 are more frequent, whereas FLT3 and DNMT3A are rare. Higher incidence of leukemic transformation has been associated with the most aggressive MPN subtype, myelofibrosis (MF); other risk factors for leukemic transformation include rising blast counts above 3-5%, advanced age, severe anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, lack of driver mutations (negative for JAK2, CALR, or MPL genes), adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157). The aforementioned factors have been incorporated in several novel prognostic scoring systems for MF. Currently, elderly/unfit patients with MPN-AP/BP are treated with hypomethylating agents with/without ruxolitinib; these regimens appear to confer comparable benefit to intensive chemotherapy but with lower toxicity. Retrospective studies in patients who acquired actionable mutations during MPN-AP/BP showed positive outcomes with targeted AML treatments, such as IDH1/2 inhibitors, and require further evaluation in clinical trials. Key Messages: Therapy for MPN-AP patients represents an unmet medical need. MF patients, in particular, should be appropriately stratified regarding their prognosis and the risk for transformation. Higher-risk patients should be monitored regularly and treated prior to progression to MPN-BP. MPN-AP patients may be treated with hypomethylating agents alone or in combination with ruxolitinib; also, patients can be provided with the option to enroll in rationally designed clinical trials exploring combination regimens, including novel targeted drugs, with an ultimate goal to transition to transplant.

What are the molecular mechanisms driving the switch from MPNs to leukemia?

Myeloproliferative neoplasm-blast phase (MPN-BP) is a form of acute leukemia which is distinct from de novo acute myeloid leukemia with each entity being characterized by specific complex cytogenetic abnormalities and myeloid gene mutational patterns. MPN-BP patients have a particularly dismal prognosis with a medium overall survival of 5.8 months with currently available therapies. Large-scale sequencing studies have unraveled the mutational landscape of the chronic MPNs and MPN-BP, demonstrating importance of clonal heterogeneity and the role of somatic mutations in disease progression and their use to determine patient outcomes. JAK inhibitors represent the standard of care for intermediate/high-risk MF patients and have been shown to improve clinical symptoms. However, this therapeutic approach leads to a modest reduction in the variant allele frequency of the known MPN driver mutations in most patients and does not substantially delay or prevent the evolution to MPN-BP. In this article, we will review molecular mechanisms driving the progression from chronic MPNs to a BP, the impact of genetic changes on MPN-BP evolution, and the role of clonal evolution in response to JAK inhibitor therapy and disease progression. We will also discuss our ongoing functional studies of cells responsible for the development of MPN-BP.

Triple-Negative Essential Thrombocythemia: Clinical-Pathological and Molecular Features. A Single-Center Cohort Study

Lack of demonstrable mutations affecting JAK2, CALR, or MPL driver genes within the spectrum of BCR-ABL1-negative myeloproliferative neoplasms (MPNs) is currently referred to as a triple-negative genotype, which is found in about 10% of patients with essential thrombocythemia (ET) and 5-10% of those with primary myelofibrosis (PMF). Very few papers are presently available on triple-negative ET, which is basically described as an indolent disease, differently from triple-negative PMF, which is an aggressive myeloid neoplasm, with a significantly higher risk of leukemic evolution. The aim of the present study was to evaluate the bone marrow morphology and the clinical-laboratory parameters of triple-negative ET patients, as well as to determine their molecular profile using next-generation sequencing (NGS) to identify any potential clonal biomarkers. We evaluated a single-center series of 40 triple-negative ET patients, diagnosed according to the 2017 WHO classification criteria and regularly followed up at the Hematology Unit of our Institution, between January 1983 and January 2019. In all patients, NGS was performed using the Illumina Ampliseq Myeloid Panel; morphological and immunohistochemical features of the bone marrow trephine biopsies were also thoroughly reviewed. Nucleotide variants were detected in 35 out of 40 patients. In detail, 29 subjects harbored one or two variants and six cases showed three or more concomitant nucleotide changes. The most frequent sequence variants involved the TET2 gene (55.0%), followed by KIT (27.5%). Histologically, most of the cases displayed a classical ET morphology. Interestingly, prevalent megakaryocytes morphology was more frequently polymorphic with a mixture of giant megakaryocytes with hyperlobulated nuclei, normal and small sized maturing elements, and naked nuclei. Finally, in five cases a mild degree of reticulin fibrosis (MF-1) was evident together with an increase in the micro-vessel density. By means of NGS we were able to identify nucleotide variants in most cases, thus we suggest that a sizeable proportion of triple-negative ET patients do have a clonal disease. In analogy with driver genes-mutated MPNs, these observations may prevent issues arising concerning triple-negative ET treatment, especially when a cytoreductive therapy may be warranted.

Accelerated and Blast Phase Myeloproliferative Neoplasms

Accelerated and blast phase myeloproliferative neoplasms are advanced stages of the disease with historically a poor prognosis and little improvement in outcomes thus far. The lack of responses to standard treatments likely results from the more aggressive biology reflected by the higher incidence of complex karyotype and high-risk somatic mutations, which are enriched at the time of transformation. Treatment options include induction chemotherapy (7 + 3) as that used on de novo acute myeloid leukemia or hypomethylating agent-based therapy, which has shown similar outcomes. Allogeneic stem cell transplantation remains the only potential for cure.

Acute Myeloid Leukemia Evolving from Myeloproliferative Neoplasms: Many Sides of a Challenging Disease

The evolution to blast phase is a frequently unpredictable and almost invariably fatal event in the course of myeloproliferative neoplasms. The molecular mechanisms underlying blast transformation have not been elucidated and the specific genetic and epigenetic events governing leukemogenesis remain unclear. The result of the long-lasting dynamics, passing through progressive genetic steps, is the emergence of one or more clones often characterized by complex genetics, either at conventional karyotyping or at modern high-throughput sequencing analyses, with all clinical and prognostic correlates. The current therapeutic approaches are largely inadequate and incapable of modifying the inherent unfavorable outcome. In this perspective, the application of targeted strategies should aim to prevent the occurrence of leukemic evolution. At transformation, the crucial target of treatment should be the allocation to allogeneic transplant for eligible patients. With this in mind, novel combination treatments may provide useful bridging strategies, beyond potentially improving outcomes for patients who are not candidates for intensive approaches.

Acute Myeloid Leukemia Evolving from Myeloproliferative Neoplasms: Many Sides of a Challenging Disease

The evolution to blast phase is a frequently unpredictable and almost invariably fatal event in the course of myeloproliferative neoplasms. The molecular mechanisms underlying blast transformation have not been elucidated and the specific genetic and epigenetic events governing leukemogenesis remain unclear. The result of the long-lasting dynamics, passing through progressive genetic steps, is the emergence of one or more clones often characterized by complex genetics, either at conventional karyotyping or at modern high-throughput sequencing analyses, with all clinical and prognostic correlates. The current therapeutic approaches are largely inadequate and incapable of modifying the inherent unfavorable outcome. In this perspective, the application of targeted strategies should aim to prevent the occurrence of leukemic evolution. At transformation, the crucial target of treatment should be the allocation to allogeneic transplant for eligible patients. With this in mind, novel combination treatments may provide useful bridging strategies, beyond potentially improving outcomes for patients who are not candidates for intensive approaches.

Current clinical strategies and emergent treatment landscapes in leukemic transformation of Philadelphia-negative myeloproliferative neoplasms

Introduction: Transformation to acute myeloid leukemia (AML) of Philadelphia chromosome-negative (Ph-) chronic myeloproliferative neoplasms (MPN) represents a challenging medical concern and an unmet clinical need, since it charts a very poor outcome and a low rate of response to standard treatments with the exception of allogeneic hematopoietic stem cell transplantation (HSCT). Recent novel insights into the molecular disease pathways and the genomic features characterizing the transformation of Ph-MPN have led to new therapeutic individualized approaches with the potential to modify the clinical management of these difficult-to-treat patients. Areas covered: Literature review (MeSH headings/PubMed) of risk factors of MPNs progression and treatment options for transformed disease with traditional standard approaches, and novel and investigational agents was performed. One or combinations of related subject headings like transformed MPN, epigenetics, molecular alterations, HSCT, ruxolitinib, azacytidine, decitabine, gliterinib, novel agents, personalized therapy was screened. Informative papers were selected by the appropriate actual evidence and suggesting strategies for improving outcomes in the future. Expert opinion: Current and emerging treatments for transformed Ph-MPN, are presented. Novel targeted or experimental agents to be used both before HSCT, to induce blast-free state, or to modify the disease prognosis and improve survival and quality of life are critically reviewed.

Genomics of MPN progression

The Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs) are a heterogenous group of hematopoietic stem cell diseases characterized by activated JAK/STAT signaling and a variable propensity toward myelofibrotic and leukemic transformation. Acquisition of somatic mutations in addition to the canonical JAK2, MPL, and CALR mutations found in MPNs is an important catalyst in the clonal evolution and progression of these disorders. In recent years, our increasing understanding of the molecular landscape of Ph- MPNs has generated important prognostic information that informs our approach to risk stratification and therapeutic decision-making. This review will focus on the critical impact of genomics on our approach to management of advanced Ph- MPNs.

Isocitrate Dehydrogenase Mutations in Myelodysplastic Syndromes and in Acute Myeloid Leukemias

Acute myeloid leukemia (AML) is a heterogeneous disease generated by the acquisition of multiple genetic and epigenetic aberrations which impair the proliferation and differentiation of hematopoietic progenitors and precursors. In the last years, there has been a dramatic improvement in the understanding of the molecular alterations driving cellular signaling and biochemical changes determining the survival advantage, stimulation of proliferation, and impairment of cellular differentiation of leukemic cells. These molecular alterations influence clinical outcomes and provide potential targets for drug development. Among these alterations, an important role is played by two mutant enzymes of the citric acid cycle, isocitrate dehydrogenase (IDH), IDH1 and IDH2, occurring in about 20% of AMLs, which leads to the production of an oncogenic metabolite R-2-hydroxy-glutarate (R-2-HG); this causes a DNA hypermethylation and an inhibition of hematopoietic stem cell differentiation. IDH mutations differentially affect prognosis of AML patients following the location of the mutation and other co-occurring genomic abnormalities. Recently, the development of novel therapies based on the specific targeting of mutant IDH may contribute to new effective treatments of these patients. In this review, we will provide a detailed analysis of the biological, clinical, and therapeutic implications of IDH mutations.

MPN: The Molecular Drivers of Disease Initiation, Progression and Transformation and their Effect on Treatment

Myeloproliferative neoplasms (MPNs) constitute a group of disorders identified by an overproduction of cells derived from myeloid lineage. The majority of MPNs have an identifiable driver mutation responsible for cytokine-independent proliferative signalling. The acquisition of coexisting mutations in chromatin modifiers, spliceosome complex components, DNA methylation modifiers, tumour suppressors and transcriptional regulators have been identified as major pathways for disease progression and leukemic transformation. They also confer different sensitivities to therapeutic options. This review will explore the molecular basis of MPN pathogenesis and specifically examine the impact of coexisting mutations on disease biology and therapeutic options.

Splicing Anomalies in Myeloproliferative Neoplasms: Paving the Way for New Therapeutic Venues

Since the discovery of spliceosome mutations in myeloid malignancies, abnormal pre-mRNA splicing, which has been well studied in various cancers, has attracted novel interest in hematology. However, despite the common occurrence of spliceosome mutations in myelo-proliferative neoplasms (MPN), not much is known regarding the characterization and mechanisms of splicing anomalies in MPN. In this article, we review the current scientific literature regarding "splicing and myeloproliferative neoplasms". We first analyse the clinical series reporting spliceosome mutations in MPN and their clinical correlates. We then present the current knowledge about molecular mechanisms by which these mutations participate in the pathogenesis of MPN or other myeloid malignancies. Beside spliceosome mutations, splicing anomalies have been described in myeloproliferative neoplasms, as well as in acute myeloid leukemias, a dreadful complication of these chronic diseases. Based on splicing anomalies reported in chronic myelogenous leukemia as well as in acute leukemia, and the mechanisms presiding splicing deregulation, we propose that abnormal splicing plays a major role in the evolution of myeloproliferative neoplasms and may be the target of specific therapeutic strategies.

Leukemia secondary to myeloproliferative neoplasms

Secondary acute myeloid leukemias (AMLs) evolving from an antecedent myeloproliferative neoplasm (MPN) are characterized by a unique set of cytogenetic and molecular features distinct from de novo AML. Given the high frequency of poor-risk cytogenetic and molecular features, malignant clones are frequently insensitive to traditional AML chemotherapeutic agents. Allogeneic stem cell transplant, the only treatment modality shown to have any beneficial long-term outcome, is often not possible given the advanced age of patients at time of diagnosis and frequent presence of competing comorbidities. Even in this setting, relapse rates remain high. As a result, outcomes are generally poor and there remains a significant unmet need for novel therapeutic strategies. Although advances in cancer genomics have dramatically enhanced our understanding of the molecular events governing clonal evolution in MPNs, the cell-intrinsic and -extrinsic mechanisms driving leukemic transformation at this level remain poorly understood. Here, we review known risk factors for the development of leukemic transformation in MPNs, recent progress made in our understanding of the molecular features associated with leukemic transformation, current treatment strategies, and emerging therapeutic options for this high-risk myeloid malignancy.

Genomic heterogeneity in myeloproliferative neoplasms and applications to clinical practice

The myeloproliferative neoplasms (MPN) polycythaemia vera, essential thrombocythaemia and primary myelofibrosis are chronic myeloid disorders associated most often with mutations in JAK2, MPL and CALR, and in some patients with additional acquired genomic lesions. Whilst the molecular mechanisms downstream of these mutations are now clearer, it is apparent that clinical phenotype in MPN is a product of complex interactions, acting between individual mutations, between disease subclones, and between the tumour and background host factors. In this review we first discuss MPN phenotypic driver mutations and the factors that interact with them to influence phenotype. We consider the importance of ongoing studies of clonal haematopoiesis, which may inform a better understanding of why MPN develop in specific individuals. We then consider how best to deploy genomic testing in a clinical environment and the challenges as well as opportunities that may arise from more routine, comprehensive genomic analysis of patients with MPN.

Roles and mechanisms of alternative splicing in cancer - implications for care

Removal of introns from messenger RNA precursors (pre-mRNA splicing) is an essential step for the expression of most eukaryotic genes. Alternative splicing enables the regulated generation of multiple mRNA and protein products from a single gene. Cancer cells have general as well as cancer type-specific and subtype-specific alterations in the splicing process that can have prognostic value and contribute to every hallmark of cancer progression, including cancer immune responses. These splicing alterations are often linked to the occurrence of cancer driver mutations in genes encoding either core components or regulators of the splicing machinery. Of therapeutic relevance, the transcriptomic landscape of cancer cells makes them particularly vulnerable to pharmacological inhibition of splicing. Small-molecule splicing modulators are currently in clinical trials and, in addition to splice site-switching antisense oligonucleotides, offer the promise of novel and personalized approaches to cancer treatment.

Prognostic impact of RAS-pathway mutations in patients with myelofibrosis

RAS-pathway mutations are recurrent events in myeloid malignancies. However, there is limited data on the significance of RAS-pathway mutations in patients with myelofibrosis (MF). We analyzed next-generation sequencing data of 16 genes, including RAS-pathway genes, from 723 patients with primary and secondary MF across three international centers and evaluated their significance. N/KRAS variants were present in 6% of patients and were typically sub-clonal (median VAF = 20%) relative to other genes variants. RAS variants were associated with advanced MF features including leukocytosis (p = 0.02), high somatic mutation burden (p < 0.01) and the presence of established "molecular high-risk" (MHR) mutations. MF patients with N/KRAS mutations had shorter 3-year overall survival (OS) (34% vs 58%, p < 0.001) and higher incidence of acute myeloid leukemia at 3 years (18% vs 11%, p = 0.03). In a multivariate Cox model, RAS mutations were associated with decreased OS (HR 1.93, p < 0.001). We created a novel score to predict OS incorporating RAS mutations, and it predicted OS across training and validation cohorts. Patients with intermediate risk/high-risk DIPSS with RAS mutations who received ruxolitinib had a nonsignificant longer 2-year OS relative to those who did not receive ruxolitinib. These data demonstrate the importance of identifying RAS mutations in MF patients.

The Molecular Genetics of Myeloproliferative Neoplasms

Activated JAK-STAT signaling is central to the pathogenesis of BCR-ABL-negative myeloproliferative neoplasms (MPNs) and occurs as a result of MPN phenotypic driver mutations in JAK2, CALR, or MPL The spectrum of concomitant somatic mutations in other genes has now largely been defined in MPNs. With the integration of targeted next-generation sequencing (NGS) panels into clinical practice, the clinical significance of concomitant mutations in MPNs has become clearer. In this review, we describe the consequences of concomitant mutations in the most frequently mutated classes of genes in MPNs: (1) DNA methylation pathways, (2) chromatin modification, (3) RNA splicing, (4) signaling pathways, (5) transcription factors, and (6) DNA damage response/stress signaling. The increased use of molecular genetics for early risk stratification of patients brings the possibility of earlier intervention to prevent disease progression in MPNs. However, additional studies are required to decipher underlying molecular mechanisms and effectively target them.

Targeted molecular characterization shows differences between primary and secondary myelofibrosis

INTRODUCTION

In BCR-ABL1-negative myeloproliferative neoplasms, myelofibrosis (MF) is either primary (PMF) or secondary (SMF) to polycythemia vera or essential thrombocythemia. MF is characterized by an increased risk of transformation to acute myeloid leukemia (AML) and a shortened life expectancy.

METHODS

Because natural histories of PMF and SMF are different, we studied by targeted next generation sequencing the differences in the molecular landscape of 86 PMF and 59 SMF and compared their prognosis impact.

RESULTS

PMF had more ASXL1 (47.7%) and SRSF2 (14%) gene mutations than SMF (respectively 27.1% and 3.4%, P = .04). Poorer survival was associated with RNA splicing mutations (especially SRSF2) and TP53 in PMF (P = .0003), and with ASXL1 and TP53 mutations in SMF (P < .0001). These mutations of poor prognosis were associated with biological features of scoring systems (DIPSS and MYSEC-PM score). Mutations in TP53/SRSF2 in PMF or TP53/ASXL1 in SMF were more frequent as the risk of these scores increased. This allowed for a better stratification of MF patients, especially within the DIPSS intermediate-1 risk group (DIPSS) or the MYSEC-PM high risk group. AML transformation occurred faster in SMF than in PMF and patients who transformed to AML were more SRSF2-mutated and less CALR-mutated at MF sampling.

CONCLUSIONS

PMF and SMF have different but not specific molecular profiles and different prognosis depending on the molecular profile. This may be due to differences in disease history. Combining mutations and existing scores should improve prognosis assessment.

Prognostic impact of circulating tumor DNA status post–allogeneic hematopoietic stem cell transplantation in AML and MDS

This study was performed to assess the utility of tumor-derived fragmentary DNA, or circulating tumor DNA (ctDNA), for identifying high-risk patients for relapse of acute myeloid leukemia and myelodysplastic syndrome (AML/MDS) after undergoing myeloablative allogeneic hematopoietic stem cell transplantation (alloSCT). We retrospectively collected tumor and available matched serum samples at diagnosis and 1 and 3 months post-alloSCT from 53 patients with AML/MDS. After identifying driver mutations in 51 patients using next-generation sequencing, we designed at least 1 personalized digital polymerase chain reaction assay per case. Diagnostic ctDNA and matched tumor DNA exhibited excellent correlations with variant allele frequencies. Sixteen patients relapsed after a median of 7 months post-alloSCT. Both mutation persistence (MP) in bone marrow (BM) at 1 and 3 months post-alloSCT and corresponding ctDNA persistence (CP) in the matched serum (MP1 and MP3; CP1 and CP3, respectively) were comparably associated with higher 3-year cumulative incidence of relapse (CIR) rates (MP1 vs non-MP1, 72.9% vs 13.8% [P = .0012]; CP1 vs non-CP1, 65.6% vs 9.0% [P = .0002]; MP3 vs non-MP3, 80% vs 11.6% [P = .0002]; CP3 vs non-CP3, 71.4% vs 8.4% [P &lt; .0001]). We subsequently evaluated whether subset analysis of patients with 3 genes associated with clonal hematopoiesis, DNMT3A, TET2, and ASXL1 (DTA), could also be helpful in relapse prediction. As a result, CP based on DTA gene mutations also had the prognostic effect on CIR. These results, for the first time, support the utility of ctDNA as a noninvasive prognostic biomarker in patients with AML/MDS undergoing alloSCT.

Targeted next-generation sequencing in blast phase myeloproliferative neoplasms

Among 248 consecutive patients with blast phase myeloproliferative neoplasm (MPN-BP), DNA collected at the time of blast transformation was available in 75 patients (median age, 66 years; 64% men). MPN-BP followed primary myelofibrosis in 39 patients, essential thrombocythemia in 20 patients, and polycythemia vera in 16 patients. A myeloid neoplasm-relevant 33-gene panel was used for next-generation sequencing. Driver mutation distribution was JAK2 57%, CALR 20%, MPL 9%, and triple-negative 13%. Sixty-four patients (85%) harbored other mutations/variants, including 37% with ≥3 mutations; most frequent were ASXL1 47%, TET2 19%, RUNX1 17%, TP53 16%, EZH2 15%, and SRSF2 13%; relative mutual exclusivity was expressed by TP53, EZH2, LNK, RUNX1, SRSF2, and NRAS/KRAS mutations. Paired chronic-blast phase sample analysis was possible in 19 patients and revealed more frequent blast phase acquisition of ASXL1, EZH2, LNK, TET2, TP53, and PTPN11 mutations/variants. In multivariable analysis, RUNX1 and PTPN11 mutations/variants were associated with shorter survival duration; respective hazard ratios (HRs) (95% confidence interval [CI]) were 2.1 (95% CI, 1.1-3.8) and 3.0 (95% CI, 1.1-6.6). An all-inclusive multivariable analysis confirmed the prognostic relevance of RUNX1 mutations (HR, 1.9; 95% CI, 1.5-5.5) and also showed additional contribution from a treatment strategy that includes transplant or induction of complete or near-complete remission (HR, 0.3; 95% CI, 0.2-0.5). The current study points to specific mutations that might bear pathogenetic relevance for leukemic transformation in MPN and also suggest an adverse survival effect of RUNX1 mutations.

Clinicopathological and molecular features of SF3B1-mutated myeloproliferative neoplasms

The introduction of next-generation sequencing has broadened the genetic landscape of myeloproliferative neoplasms (MPNs) beyond JAK2, MPL, and CALR. However, the biological role and clinical impact of most other mutations are not well defined. We interrogated 101 genes in 143 BCR-ABL1-negative MPNs in chronic phase from 2 large institutions. We detected SF3B1 mutations in 15 cases (10%) and set to investigate the clinical, morphologic, and molecular features of SF3B1 mutated (SF3B1+) MPNs in comparison to SF3B1 wild-type (SF3B1-) cases and to identify distinctive features with myelodysplastic/myeloproliferative neoplasms with ring sideroblasts (RS) and thrombocytosis, which can show partial clinical and morphological overlap with MPNs. SF3B1+ cases were enriched in primary myelofibrosis in both prefibrotic and fibrotic stage, but mutations of SF3B1 seem to occur only as a late event in the fibrotic phase of essential thrombocythemia and polycythemia vera. SF3B1+ MPNs showed borderline lower hemoglobin but no other clinical or molecular differences compared to SF3B1- MPNs. Of note, RS were present only in a subset of SF3B1+ cases (4/10) without any other feature of erythroid or granulocytic dysplasia. Our results suggest that mutations in SF3B1 are not a rare event in MPNs, especially in primary myelofibrosis and during late fibrotic stages of essential thrombocythemia and polycythemia vera, but are not associated with myelodysplastic progression. Careful examination of bone marrow and peripheral blood for morphologic dysplasia is crucial to reach the correct diagnosis and avoid a misdiagnosis of myelodysplastic/myeloproliferative neoplasms with RS and thrombocytosis, a pitfall with potential prognostic and therapeutic implications.

How I treat the blast phase of Philadelphia chromosome–negative myeloproliferative neoplasms

The classic Philadelphia chromosome (Ph)–negative myeloproliferative neoplasms (MPNs) are a heterogeneous group of hematopoietic stem-cell diseases, characterized by activated JAK/STAT signaling and significant phenotypic mimicry, including a propensity for evolution to myeloid blast phase disease. Effective therapeutic options are limited for patients with Ph− MPNs in the blast phase (MPN-BP), and allogeneic stem-cell transplantation is the only known cure. Our increasing understanding of the molecular pathogenesis of this group of diseases, coupled with the increasing availability of targeted agents, has the potential to inform new subset-specific therapeutic approaches. Ultimately, progress in MPN-BP will hinge on prospective clinical and translational investigations with the goal of generating more effective treatment interventions. This case-based review highlights the molecular and clinical heterogeneities of MPN-BP and incorporates a treatment algorithm that underscores the importance of a personalized approach to this challenging group of diseases.