Epigenetics in Myeloproliferative Neoplasms

Molecular diagnostic criteria of myeloproliferative neoplasms

INTRODUCTION

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal hematopoietic stem cell neoplasms characterized by the driver mutations JAK2, CALR, and MPL. These mutations cause constitutive activation of JAK-STAT signaling, which is central to pathogenesis of MPNs. Next-generation sequencing has further expanded the molecular landscape allowing for improved diagnostics, prognostication, and targeted therapy.

AREAS COVERED

This review aims to address current understanding of the molecular diagnosis of MPN not only through improved awareness of the driver mutations but also the disease modifying mutations. In addition, other genetic factors such as clonal hematopoiesis of indeterminate potential (CHIP), order of mutation, and mutation co-occurrence are discussed and how these factors influence disease initiation and ultimately progression. How this molecular information is incorporated into risk stratification models allowing for earlier intervention and targeted therapy in the future will be addressed further.

EXPERT OPINION

The genomic landscape of the MPN has evolved in the last 15 years with integration of next-generation sequencing becoming the gold standard of MPN management. Although diagnostics and prognostication have become more personalized, additional studies are required to translate these molecular findings into targeted therapy therefore improving patient outcomes.

P14.5 functions to inhibit cell migration and can be used as a prognostic marker in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy with a high mortality rate. P14.5 is a member of the highly conserved YER057c/YIL051c/YjgF subfamily and is highly expressed in the liver. However, its low expression is associated with carcinogenesis in HCC.

OBJECTIVE

This study aimed to investigate the role and prognostic significance of P14.5 in HCC.

METHODS

The clinical significance of P14.5 in HCC was examined using ONCOMINE, UALCAN, Human Protein Atlas, and Kaplan-Meier plotter. The DNA methylation profile of the P14.5 promoter was examined in 103 HCC and paired precancerous tissues; the HCC cell lines HepG2, MHCC-97L, SMMC-7721, SK-Hep-1, and Huh7; and the normal hepatic cell line HL-7702 via MALDI-TOF mass spectrometry. In addition, in vitro experiments were performed to examine the effects of P14.5 overexpression on the proliferation and migration of SMMC-7721 cells.

RESULTS

Low expression of P14.5 was correlated with shorter overall survival (OS) and disease-free survival (DFS) in HCC. Based on the results of MALDI-TOF mass spectrometry, no difference was observed in the methylation level between HCC cells and normal human hepatic cells and between HCC and paired precancerous tissues. Additionally, P14.5 overexpression promoted the proliferation and inhibited the migration of SMMC7721 cells in vitro.

CONCLUSIONS

P14.5 may serve as a prognostic biomarker in HCC and plays a role in the migration and proliferation of HCC cells. Low expression of P14.5 during hepatocarcinogenesis is not attributed to DNA methylation.

Screening for aberrantly methylated and differentially expressed genes in nonalcoholic fatty liver disease of hepatocellular carcinoma patients with cirrhosis

Background

Nonalcoholic fatty liver disease (NAFLD) as the leading chronic liver disease worldwide causes hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The aim of this study was to find potential aberrantly methylated and differentially expressed genes in NAFLD of HCC patients with cirrhosis.

Methods

DNA methylation data, mRNA expression data, and the corresponding clinical information of HCC were downloaded from the Cancer Genome Atlas (TCGA, tissue sample) database. HCC patients with cirrhosis were divided into two groups according to the presence of NAFLD. The differentially expressed genes (DEGs) and differentially methylated genes (DMGs) were obtained.

Results

By overlapping 79 up-regulated genes and 1020 hypomethylated genes, we obtained 5 hypomethylated-highly expressed genes (Hypo­HGs). By overlapping 365 down-regulated genes and 481 hypermethylated genes, we identified 13 hypermethylated-lowly expressed genes (Hyper-LGs). Survival analysis of these 18 MDEGs indicated that the expression of DGKK and HOXD9 was significantly correlated with the overall survival time of NAFLD patients.

Conclusions

We identified several candidate genes whose expressions were regulated by DNA methylation of NAFLD of HCC with cirrhosis, which may provide a new field in understanding the clinical pathological mechanism of NAFLD of HCC with cirrhosis.

Identification of three novel DNMT3A mutations with compromising methylation capacity in human acute myeloid leukaemia

BACKGROUND

Acute myeloid leukaemia (AML) is a complex and heterogeneous hematopoietic stem and progenitor cell malignancy characterised by the accumulation of immature blast cells in the bone marrow, blood, and other organs linked to environmental, genetic, and epigenetic factors. Somatic mutations in the gene DNA (cytosine-5)-methyltransferase 3A (DNMT3A; NM_022552.4) are common in AML patients.

METHODS

In this study, we used Sanger sequencing to detect the mutations in the DNMT3A gene in 61 Iraqi AML patients, Hence, the protein function and stability within alterations were identified and analyzed using a variety of computational tools with the goal of determining how these changes affect total protein stability, and then the capacity of methylation was analyzed by methylation specific PCR MSP status at CpG islands.

RESULTS

Three novel mutations in exon 23 of DNMT3A were identified in 14 patients (22.9%; V877I, N879delA, and L888Q). The V877I and L888Q substitutions are caused by heterozygous C2629G > A and C2663T > A mutations, respectively, while frameshift mutation C2635delA caused protein truncation with stop codon N879T*. Methylation was detected in the DNMT3A promoter region in 9 patients carrying DNMT3A mutations (64.28%) by MSP, and we found significant correlations between DNMT3A mutations and promoter methylation (p = 8.52 × 10⁵). In addition, we found a significant overrepresentation of DNMT3A methylation status in patients ≥ 50 years old (p = 0.025).

CONCLUSION

Our findings highlight the importance of studying the effects of DNMT3A methylation alteration in Iraqi populations beyond R882 substitutions in the leukemogenic pathway so that patient treatment can be tailored to prevent therapeutic resistance and relapse.

Understanding Aberrant Signaling to Elude Therapy Escape Mechanisms in Myeloproliferative Neoplasms

Aberrant signaling in myeloproliferative neoplasms may arise from alterations in genes coding for signal transduction proteins or epigenetic regulators. Both mutated and normal cells cooperate, altering fragile balances in bone marrow niches and fueling persistent inflammation through paracrine or systemic signals. Despite the hopes placed in targeted therapies, myeloid proliferative neoplasms remain incurable diseases in patients not eligible for stem cell transplantation. Due to the emergence of drug resistance, patient management is often very difficult in the long term. Unexpected connections among signal transduction pathways highlighted in neoplastic cells suggest new strategies to overcome neoplastic cell adaptation.

Insights into the Potential Mechanisms of JAK2V617F Somatic Mutation Contributing Distinct Phenotypes in Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPN) are a group of blood cancers in which the bone marrow (BM) produces an overabundance of erythrocyte, white blood cells, or platelets. Philadelphia chromosome-negative MPN has three subtypes, including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The over proliferation of blood cells is often associated with somatic mutations, such as JAK2, CALR, and MPL. JAK2V617F is present in 95% of PV and 50–60% of ET and PMF. Based on current molecular dynamics simulations of full JAK2 and the crystal structure of individual domains, it suggests that JAK2 maintains basal activity through self-inhibition, whereas other domains and linkers directly/indirectly enhance this self-inhibited state. Nevertheless, the JAK2V617F mutation is not the only determinant of MPN phenotype, as many normal individuals carry the JAK2V617F mutation without a disease phenotype. Here we review the major MPN phenotypes, JAK-STAT pathways, and mechanisms of development based on structural biology, while also describing the impact of other contributing factors such as gene mutation allele burden, JAK-STAT-related signaling pathways, epigenetic modifications, immune responses, and lifestyle on different MPN phenotypes. The cross-linking of these elements constitutes a complex network of interactions and generates differences in individual and cellular contexts that determine the phenotypic development of MPN.

Integrated Bioinformatic Analysis Identifies TIPIN as a Prognostic Biomarker in Hepatocellular Carcinoma

Background

Gene expression and DNA methylation analyses have long been used to identify cancer markers. However, a combination analysis of the gene expression and DNA methylation has yet to be performed to identify potential biomarkers of hepatocellular carcinoma (HCC).

Methods

By matching gene expression profiles and promoter methylation data in The Cancer Genome Atlas (TCGA), genes with discrepant expression as well as genes with differential promoter methylation were identified. High-expression genes with low promoter methylation were defined as epigenetically induced (EI), while low-expression genes with high promoter methylation were defined as epigenetically suppressed (ES). The human protein interaction network was further integrated to construct the EI/ES gene interaction network, and the key genes in the subnet were identified as potential HCC biomarkers. The expression differences and prognostic values were verified in TCGA and Gene Expression Omnibus (GEO) databases, as well as with tissue chip technology.

Results

Four key genes were identified: TIPIN, RBM15B, DUSP28, and TRIM31, which demonstrated the differential gene expression and prognostic value in TCGA and GEO databases. Tissue microarray analysis (TMA) revealed that TIPIN levels were altered in HCC. The upregulated TIPIN expression was associated with worse overall survival. Univariate and multivariate analyses showed that the TIPIN expression was an independent predictor of HCC.

Conclusion

TIPIN might be a potential novel prognostic biomarker for HCC.

A computer aided drug discovery based discovery of lead-like compounds against KDM5A for cancers using pharmacophore modeling and high-throughput virtual screening

KDM5A over-expression mediates cancer cell proliferation and promotes resistance toward chemotherapy through epigenetic modifications. As its complete mechanism of action is still unknown, there is no KDM5A specific drug available at clinical level. In the current study, lead compounds for KDM5A were determined through pharmacophore modeling and high-throughput virtual screening from Asinex libraries containing 0.5 million compounds. These virtual hits were further evaluated and filtered for ADMET properties. Finally, 726 compounds were used for docking analysis against KDM5A. On the basis of docking score, 10 top-ranked compounds were selected and further evaluated for non-central nervous system (CNS) and CNS drug-like properties. Among these compounds, N-{[(7-Methyl-4-oxo-1,2,3,4-tetrahydrocyclopenta [c] chromen-9-yl) oxy]acetyl}-l-phenylalanine (G-score: -11.363 kcal/mol) was estimated to exhibit non-CNS properties while 2-(3,4-Dimethoxy-phenyl)-7-methoxy-chromen-4-one (G-score: -7.977 kcal/mol) was evaluated as CNS compound. Docked complexes of both compounds were finally selected for molecular dynamic simulation to examine the stability. This study concluded that both these compounds can serve as lead compounds in the quest of finding therapeutic agents against KDM5A associated cancers.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Gene expression profiling of CD34(+) cells from patients with myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal disorders characterized by the increased proliferation of hematopoietic stem cell precursors and mature blood cells. Mutations of Janus kinase 2 (JAK2), Calreticulin (CALR) and MPL (myeloproliferative leukemia virus) are key driver mutations in MPN. However, the molecular profile of triple negative MPN has been a subject of ambiguity over the past few years. Mutations of, methylcytosine dioxygenase TET2, polycomb group protein ASXL1 and histone-lysine N-methyltransferase EZH2 genes have accounted for certain subsets of triple negative MPNs but the driving cause for majority of cases is still unexplored. The present study performed a microarray-based transcriptomic profile analysis of bone marrow-derived CD34(+) cells from seven MPN samples. A total of 21,448 gene signatures were obtained, which were further filtered into 472 upregulated and 202 downregulated genes. Gene ontology and protein-protein interaction (PPI) network analysis highlighted an upregulation of genes involved in cell cycle and chromatin modification in JAK2V617F negative vs. positive MPN samples. Out of the upregulated genes, seven were associated with the hematopoietic stem cell signature, while forty-seven were associated with the embryonic stem cell signature. The majority of the genes identified were under the control of NANOG and E2F4 transcription factors. The PPI network indicated a strong interaction between chromatin modifiers and cell cycle genes, such as histone-lysine N-methyltransferase SUV39H1, SWI/SNF complex subunit SMARCC2, SMARCE2, chromatin remodeling complex subunit SS18, tubulin β (TUBB) and cyclin dependent kinase CDK1. Among the upregulated epigenetic markers, there was a ~10-fold increase in MYB expression in JAK2V617F negative samples. A significant increase in total CD34 counts in JAK2V617F negative vs. positive samples (P<0.05) was also observed. Overall, the present data showed a distinct pattern of expression in JAK2V617F negative vs. positive samples with upregulated genes involved in epigenetic modification.

TET2, DNMT3A, IDH1, and JAK2 Mutation in Myeloproliferative Neoplasms in southern Iran

BACKGROUND

Five epigenetic regulator mutations are considered in myeloproliferative neoplasms (MPN) that have prognostic and therapeutic values.

OBJECTIVE

We aimed to evaluate these mutations in MPNs among the Iranian population.

METHODS

We selected 5 mutations in 4 epigenetic regulatory genes [TET2, DNMT3A, IDH1 (rs147001633&rs121913499), and JAK2)] and evaluated 130 patients with MPNs including 78 Philadelphia chromosome negative (49 ETs, 20 PVs, and 9 PMFs) and 52 Philadelphia chromosome-positive patients as well as 51 healthy controls.

RESULTS

Eight patients (6.5%) carried the DNMT3A mutation, 35 (27%) were positive for TET2 mutation and 64 (49.3%) had the JAK2V617F mutation. In the healthy controls, 16 (31.4%) cases had the TET2 mutation (15 Heterozygote + 1 Homozygote) and one had heterozygote JAK2 mutation. There was no statistically significant difference between patient groups for any of these mutations, except for JAK2. The JAK2 mutation rate was 18 (90%), 25 (51%), 7 (77.8%), 14 (26.9%) in polycythemia vera, essential thrombocythemia, primary myelofibrosis, and chronic myelocytic leukemia, respectively. Patients aged 60 and older were more likely to carry the TET2 mutation (23% vs. 39% in younger and older than 60 years old individuals, p=0.025). IDH1 was not detected at all and PV had the highest TET2 mutation 7(35%). Two PMF patients had a history of bone marrow transplantation that were negative for IDH1and DNMT3A and one was positive for TET2 mutation.

CONCLUSION

In the normal Iranian population, the heterozygote form of TET2 mutation is significant, especially in the elderly. No association was found between JAK2 and TET2 mutations. Both of them are more prevalent in the age group of 60 years and older. DNMT3A mutation has a low prevalence and occurs in both positive and negative MPNs.

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.

Preclinical evaluation of a regimen combining chidamide and ABT-199 in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous myeloid neoplasm with poor clinical outcome, despite the great progress in treatment in recent years. The selective Bcl-2 inhibitor venetoclax (ABT-199) in combination therapy has been approved for the treatment of newly diagnosed AML patients who are ineligible for intensive chemotherapy, but resistance can be acquired through the upregulation of alternative antiapoptotic proteins. Here, we reported that a newly emerged histone deacetylase inhibitor, chidamide (CS055), at low-cytotoxicity dose enhanced the anti-AML activity of ABT-199, while sparing normal hematopoietic progenitor cells. Moreover, we also found that chidamide showed a superior resensitization effect than romidepsin in potentiation of ABT-199 lethality. Inhibition of multiple HDACs rather than some single component might be required. The combination therapy was also effective in primary AML blasts and stem/progenitor cells regardless of disease status and genetic aberrance, as well as in a patient-derived xenograft model carrying FLT3-ITD mutation. Mechanistically, CS055 promoted leukemia suppression through DNA double-strand break and altered unbalance of anti- and pro-apoptotic proteins (e.g., Mcl-1 and Bcl-xL downregulation, and Bim upregulation). Taken together, these results show the high therapeutic potential of ABT-199/CS055 combination in AML treatment, representing a potent and alternative salvage therapy for the treatment of relapsed and refractory patients with AML.

Modification of the Histone Landscape with JAK Inhibition in Myeloproliferative Neoplasms

Dysregulation of epigenetic processes is increasingly understood to play a role in the pathogenesis of myeloproliferative neoplasms (MPNs). Ruxolitinib, a JAK/STAT inhibitor, has proved a useful addition to the therapeutic arsenal for these disorders, but has limited disease modifying activity. We determined the effect of JAK inhibition on the histone landscape of MPN cells in cell line models of MPNs and validated using samples from the MAJIC randomised clinical trial of ruxolitinib in polycythaemia vera and essential thrombocythaemia. We demonstrated an epigenetic modifying effect of ruxolitinib using a histone modification assay. The majority of 21 histone H3 modifications were upregulated, with H3K27me3 and H3K36me2 significant in the combined cell line results. Chromatin immunoprecipitation and sequencing (CHIP-seq) for three marks of interest, H3K4me1, H3K4me3 and H3K27ac, was consistent with the histone modification assay showing a significant increase in H3K4me3 and H3K27ac peaks at promoter regions, both marks of active transcription. In contrast, RNA sequencing demonstrates a coordinated reduction in gene expression in a number of cell pathways including PI3K-AKT signalling, transcriptional misregulation in cancer and JAK-STAT signalling in spite of these histone changes. This highlights the complex mechanisms of transcriptional control within the cells which was reflected in analysis of the histone landscape in patient samples following ruxolitinib treatment.

A novel strategy for the diagnosis, prognosis, treatment, and chemoresistance of hepatocellular carcinoma: DNA methylation

The cancer mortality rate of hepatocellular carcinoma (HCC) is the second highest in the world and the therapeutic options are limited. The incidence of this deadly cancer is rising at an alarming rate because of the high degree of resistance to chemo- and radiotherapy, lack of proper, and adequate vaccination to hepatitis B, and lack of consciousness and knowledge about the disease itself and the lifestyle of the people. DNA methylation and DNA methylation-induced epigenetic alterations, due to their potential reversibility, open the access to develop novel biomarkers and therapeutics for HCC. The contribution to these epigenetic changes in HCC development still has not been thoroughly summarized. Thus, it is necessary to better understand the new molecular targets of HCC epigenetics in HCC diagnosis, prevention, and treatment. This review elaborates on recent key findings regarding molecular biomarkers for HCC early diagnosis, prognosis, and treatment. Currently emerging epigenetic drugs for the treatment of HCC are summarized. In addition, combining epigenetic drugs with nonepigenetic drugs for HCC treatment is also mentioned. The molecular mechanisms of DNA methylation-mediated HCC resistance are reviewed, providing some insights into the difficulty of treating liver cancer and anticancer drug development.

When Oxidative Stress Meets Epigenetics: Implications in Cancer Development

Cancer is one of the leading causes of death worldwide and it can affect any part of the organism. It arises as a consequence of the genetic and epigenetic changes that lead to the uncontrolled growth of the cells. The epigenetic machinery can regulate gene expression without altering the DNA sequence, and it comprises methylation of the DNA, histones modifications, and non-coding RNAs. Alterations of these gene-expression regulatory elements can be produced by an imbalance of the intracellular environment, such as the one derived by oxidative stress, to promote cancer development, progression, and resistance to chemotherapeutic treatments. Here we review the current literature on the effect of oxidative stress in the epigenetic machinery, especially over the largely unknown ncRNAs and its consequences toward cancer development and progression.

Givinostat: an emerging treatment for polycythemia vera

INTRODUCTION

Polycythemia vera (PV), a Philadelphia chromosome-negative myeloproliferative neoplasm, is characterized by panmyelosis, pancytosis, and a JAK2 mutation. Patients are at increased risk of thrombohemorrhagic events, and progression to myelofibrosis or acute leukemia. Current treatments include aspirin, phlebotomy, and cytoreductive drugs (most commonly hydroxyurea). Givinostat is a potent, class I/II histone deacetylase (HDAC) inhibitor that is in phase I/II clinical trials in PV. Givinostat was well tolerated and yielded promising clinico-hematological responses. A phase III study of givinostat versus hydroxyurea in high-risk PV patients is planned.

AREAS COVERED

We present an overview of PV, current treatment guidelines, and the putative mechanism(s) of action of givinostat. We discuss the preclinical and clinical studies of givinostat in PV and briefly review approved and investigational competitor compounds.

EXPERT OPINION

HDAC inhibitors have long been known to be active in PV, but chronic toxicities can be challenging. Givinostat, however, is active and well tolerated, and is entering a pivotal Phase III randomized trial. Givinostat offers the possibility of replacing hydroxyurea as the standard first-line cytoreductive choice for PV patients. This would completely change the current therapeutic paradigm and guidelines for PV management. Although surrogate clinical study endpoints may suffice for regulatory purposes, thrombosis reduction and prevention of disease progression remain most important to patients and clinicians.

JAK2-negative acute monocytic leukemia with TET2 mutation in essential thrombocythemia with JAK2 mutation with literature review

Essential thrombocythemia (ET) is an indolent myeloproliferative neoplasm (MPN) with a transformation to acute myeloid leukemia in <5% of patients. A 79-year-old man with JAK2V617F-positive ET exhibited leukocytosis with an increase in monoblastic cells, leading to a diagnosis of acute monoblastic and monocytic leukemia. Leukemic cells carried a TET2 mutation but not JAK2V617F mutation. We concluded that the TET2 mutation occurred in MPN-initiating cells and overcame JAK2-mutated cells. The absence of a JAK2 mutation in the leukemic cells in this case suggests the leukemia emerged from a JAK2-negative MPN cell clone carrying the TET2 mutation.

Advanced forms of MPNs are accompanied by chromosomal abnormalities that lead to dysregulation of TP53

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and the prefibrotic form of primary myelofibrosis (PMF), frequently progress to more overt forms of MF and a type of acute leukemia termed MPN-accelerated phase/blast phase (MPN-AP/BP). Recent evidence indicates that dysregulation of the tumor suppressor tumor protein p53 (TP53) commonly occurs in the MPNs. The proteins MDM2 and MDM4 alter the cellular levels of TP53. We investigated in 1,294 patients whether abnormalities involving chromosomes 1 and 12, which harbor the genes for MDM4 and MDM2, respectively, and chromosome 17, where the gene for TP53 is located, are associated with MPN disease progression. Gain of 1q occurred not only in individuals with MPN-BP but also in patients with PV and ET, who, with further follow-up, eventually evolve to either MF and/or MPN-BP. These gains of 1q were most prevalent in patients with a history of PV and those who possessed the JAK2V617F driver mutation. The gains of 1q were accompanied by increased transcript levels of MDM4 In contrast, 12q chromosomal abnormalities were exclusively detected in patients who presented with MF or MPN-BP, but were not accompanied by further increases in MDM2/MDM4 transcript levels. Furthermore, all patients with a loss of 17p13, which leads to a deletion of TP53, had either MF or MPN-AP/BP. These findings suggest that gain of 1q, as well as deletions of 17p, are associated with perturbations of the TP53 pathway, which contribute to MPN disease progression.

Analysis of genes encoding epigenetic regulators in myeloproliferative neoplasms: Coexistence of a novel SETBP1 mutation in a patient with a p.V617F JAK2 positive myelofibrosis

In recent years it has been shown that the causes of chronic myeloproliferative neoplasms (MPNs) are more complex than a simple signaling aberration and many other mutated genes affecting different cell processes have been described. For instance, mutations in genes encoding epigenetic regulators are more frequent than expected. One of the latest genes described as mutated is SET binding protein 1 (SETBP1). In silico tools have revealed that there are several human SETBP1 paralogous to nuclear receptor binding SET domain protein 1 (NSD1), NSD2 and NSD3, for example, which are also involved in the development of other hematological malignancies. Therefore, the present study analyzed the mutational status of NSD1, NSD2, NSD3 and SETBP1 in BCR-ABL1 negative MPNs with or without Janus kinase 2 (JAK2) p.V617F mutation. The present study revealed that the NSD genes are not frequently mutated in MPNs. However, a novel SETBP1 mutation was identified in a patient with p.V617F JAK2 positive primary myelofibrosis. These results provide further insight into the genetic complexity of MPNs.

Does SF3B1/TET2 Double Mutation Portend Better or Worse Prognosis Than Isolated SF3B1 or TET2 Mutation?

BACKGROUND

Mutations in splicing factor 3b subunit 1 (SF3B1) have been reported to be associated with a favorable prognosis, while the prognostic impact of tet methylcytosine dioxygenase 2 (TET2) mutations is still controversial. The clinical significance of combined SF3B1 and TET2 mutation is even more uncertain. In this study, the clinical consequences of concurrent double SF3B1/TET2 mutation were compared with isolated SF3B1 or TET2 mutation.

MATERIALS AND METHODS

The demographics, diagnosis, cytogenetic abnormalities, and overall survival time of 130 patients with isolated SF3B1 (n=48) or TET2 mutation (n=54), or double SF3B1/TET2 mutation (n=28) were compared by next-generation sequencing.

RESULTS

Patients with double mutation were found to be significantly older than patients with isolated TET2 mutation. Patients with double mutation or isolated SF3B1 mutation were less likely to be diagnosed with acute myeloid leukemia than patients with isolated TET2 mutation. Patients with myelodysplasia had a higher percentage of double or isolated SF3B1 mutation, while patients with myeloproliferative neoplasms had a higher percentage of isolated TET2 mutation. Patients with double mutation more frequently had increased ring sideroblasts similarly to patients with isolated SF3B1 mutation. The percentage of patients with normal cytogenetics or good cytogenetic abnormalities was significantly higher in patients with double mutation than those with isolated mutation. Finally, in patients with myelodysplasia and normal cytogenetics, the median survival time in those with double mutation was significantly longer than in those with isolated SF3B1 mutation, even though the overall survival curve was not statistically significant.

CONCLUSION

TET2 mutation appeared not to have additional effects when combined with SF3B1, and patients with double mutation appeared to have at least as, good as or even better prognosis than patients with isolated mutation.

Ruxolitinib

Ruxolitinib, formerly known as INCB018424 or INC424, is a potent and selective oral inhibitor of Janus kinase (JAK) 1 and JAK2. Ruxolitinib has been approved for the treatment of myelofibrosis (MF) by the US Food and Drug Administration (FDA) in 2011 and by the European Medicines Agency (EMA) in 2012, followed by the approval for the treatment of hydroxyurea (HU)-resistant or -intolerant polycythemia vera (PV) in 2014. Both MF and PV are myeloproliferative neoplasms (MPNs) which are characterized by the aberrant activation of the JAK-STAT pathway. Clinically, MF features bone marrow fibrosis, splenomegaly, abnormal blood counts, and poor quality-of-life through associated symptoms. PV is characterized by the overproduction of primarily red blood cells (RBC), risk of thrombotic complications, and development of secondary MF. Ruxolitinib treatment results in a meaningful reduction in spleen size and symptom burden in the majority of MF patients and may also have a favorable effect on survival. In PV, ruxolitinib effectively controls the hematocrit and reduces splenomegaly. Since recently, ruxolitinib is also under investigation for the treatment of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HSCT). Toxicities of ruxolitinib include myelosuppression, which results in dose-limiting thrombocytopenia and anemia, and viral reactivations. The metabolization of ruxolitinib through CYP3A4 needs to be considered particularly if co-administered with potent CYP3A4 inhibitors. Several further JAK inhibitors are currently under investigation for MPNs or other immuno-inflammatory diseases.

Emerging therapeutic targets in myeloproliferative neoplasms and peripheral T-cell leukemia and lymphomas

Introduction: Hematopoietic neoplasms are often driven by gain-of-function mutations of the JAK-STAT pathway together with mutations in chromatin remodeling and DNA damage control pathways. The interconnection between the JAK-STAT pathway, epigenetic regulation or DNA damage control is still poorly understood in cancer cell biology.

Areas covered: Here, we focus on a broader description of mutational insights into myeloproliferative neoplasms and peripheral T-cell leukemia and lymphomas, since sequencing efforts have identified similar combinations of driver mutations in these diseases covering different lineages. We summarize how these pathways might be interconnected in normal or cancer cells, which have lost differentiation capacity and drive oncogene transcription.

Expert opinion: Due to similarities in driver mutations including epigenetic enzymes, JAK-STAT pathway activation and mutated checkpoint control through TP53, we hypothesize that similar therapeutic approaches could be of benefit in these diseases. We give an overview of how driver mutations in these malignancies contribute to hematopoietic cancer initiation or progression, and how these pathways can be targeted with currently available tools.