Luspatercept: A New Tool for the Treatment of Anemia Related to β-Thalassemia, Myelodysplastic Syndromes and Primary Myelofibrosis

Anemia is a common feature of both benign and malignant hematologic diseases. Beta-thalassemia (β-thalassemia) syndromes are a group of hereditary disorders characterized by ineffective erythropoiesis, due to a genetic deficiency in the synthesis of the beta chains of hemoglobin, often accompanied by severe anemia and the need for red blood cell (RBC) transfusions. Myelodysplastic syndromes (MDS) are characterized by cytopenia(s) and ineffective hematopoiesis, despite a hypercellular bone marrow. Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm characterized by reactive fibrosis of the bone marrow, accompanied by extramedullary hematopoiesis. Luspatercept, previously known as ACE-536, is a fusion protein that combines a modified activin receptor IIB (ActRIIB), a member of the transforming growth factor-β (TGF-β) superfamily, with the Fc domain of human immunoglobulin G (IgG1). It has shown efficacy in the treatment of anemia due to beta β-thalassemia, MDS and PMF and recently gained approval by the Federal Drug Agency (FDA) and the European Medicines Agency (EMA) for transfusion-dependent (TD) patients with β-thalassemia and very low to intermediate-risk patients with MDS with ringed sideroblasts who have failed to respond to, or are ineligible for, an erythropoiesis-stimulating agent. In this review, we describe the key pathways involved in normal hematopoiesis and the possible mechanism of action of luspatercept, present its development and data from the most recent clinical trials in β-thalassemia, MDS and PMF, and discuss its potential use in the treatment of these hematological disorders.

Epialleles and epiallelic heterogeneity in hematological malignancies

DNA methylation has a well-established role in the pathogenesis, prognosis, and response to treatment in all the spectra of hematological malignancies. However, most of the data reported involve average DNA methylation observed in a sample. The emergence of bisulfite sequencing methods such as enhanced reduced representation that permit analyze adjacent CpGs led to exciting findings. Among these are the epialleles shift and the resulting epigenetic heterogeneity observed in leukemias and lymphomas. Epialleles seem to have an influential role as the cause of mutations that characterize leukemias, may stratify groups with different prognosis and response to treatment, and may be redistributed in the genome at different time points of the disease promoting activation of alternate transcriptional networks. Epiallelic shift may be responsible for the intratumor heterogeneity observed within the cells of the same tumor which increases with disease aggressiveness. It may also responsible for the interpatient heterogeneity explaining why blood cancers exhibit different behavior among different patients. Understanding better epiallelic conformation and the consequent chromatin conformational changes and the pathways that may be affected will permit deeper understanding of hematological malignancies pathogenesis and treatment.

Long non-coding RNAs and MYC association in hematological malignancies

Long non-coding RNAs (lncRNAs) have an established role in cell biology. Among their functions is the regulation of hematopoiesis. They characterize the different stages of hematopoiesis in a more lineage-restricted expression pattern than coding mRNAs. They affect hematopoietic stem cell renewal, proliferation, and differentiation of committed progenitors by interacting with master regulators transcription factors. Among these transcription factors, MYC has a prominent role. Similar to MYC's transcriptional activation/amplification of protein coding genes, MYC also regulates lncRNAs' expression profile, while it is also regulated by lncRNAs. Both myeloid and lymphoid malignancies are prone to the association of MYC with lncRNAs. Such interaction inhibits apoptosis, enhances cell proliferation, deregulates metabolism, and promotes genomic instability and resistance to treatment. In this review, we discuss the recent findings that encompass the crosstalk between lncRNAs and describe the pathways that very probably have a pathogenetic role in both acute and chronic hematologic malignancies.

Enhancers and MYC interplay in hematopoiesis

Transcription requires the fine interplay between enhancers and transcription factors. Enhancers are able to activate transcription of genes involved in normal cell biology, whereas aberrant enhancer activity leads to oncogenesis. MYC is a well-established proto-oncogene involved in half of human cancers amplifying the output of its targets. The crosstalk between MYC and enhancers is known for many years since the discovery of IgH enhancer juxtaposition with MYC in high-grade lymphomas. Here, we focus mainly in the enhancers surrounding MYC in the 8q24 locus. That region comprises several enhancers that associate with other transcription factors, transmembrane receptors, and fusion genes composing complex regulatory networks aberrantly expressed in almost all types of hematological malignancies. Understanding the nature of these interactions in normal blood cells and in leukemias/lymphomas will expand MYC targeting options in the armamentarium against hematological cancers.

On the potential role of DNMT1 in acute myeloid leukemia and myelodysplastic syndromes: not another mutated epigenetic driver

DNA methylation is the most common epigenetic modification in the mammalian genome. DNA methylation is governed by the DNA methyltransferases mainly DNMT1, DNMT3A, and DNMT3B. DNMT1 methylates hemimethylated DNA ensuring accurate DNA methylation maintenance. DNMT1 is involved in the proper differentiation of hematopoietic stem cells (HSCs) through the interaction with effector molecules. DNMT1 is deregulated in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) as early as the leukemic stem cell stage. Through the interaction with fundamental transcription factors, non-coding RNAs, fusion oncogenes and by modulating core members of signaling pathways, it can affect leukemic cells biology. DNMT1 action might be also catalytic-independent highlighting a methylation-independent mode of action. In this review, we have gathered some current facts of DNMT1 role in AML and MDS and we also propose some perspectives for future studies.

DLK1-DIO3 imprinted cluster in induced pluripotency: landscape in the mist

DLK1-DIO3 represents an imprinted cluster which genes are involved in physiological cell biology as early as the stem cell level and in the pathogenesis of several diseases. Transcription factor-mediated induced pluripotent cells (iPSCs) are considered an unlimited source of patient-specific hematopoietic stem cells for clinical application in patient-tailored regenerative medicine. However, to date there is no marker established able to distinguish embryonic stem cell-equivalent iPSCs or safe human iPSCs. Recent findings suggest that the DLK1-DIO3 locus possesses the potential to represent such a marker but there are also contradictory data. This review aims to report the current data on the topic describing both sides of the coin.

Gene mutations and molecularly targeted therapies in acute myeloid leukemia

Acute myelogenous leukemia (AML) can progress quickly and without treatment can become fatal in a short period of time. However, over the last 30 years fine-tuning of therapeutics have increased the rates of remission and cure. Cytogenetics and mutational gene profiling, combined with the option of allogeneic hematopoietic stem cell transplantation offered in selected patients have further optimized AML treatment on a risk stratification basis in younger adults. However there is still an unmet medical need for effective therapies in AML since disease relapses in almost half of adult patients becoming refractory to salvage therapy. Improvements in the understanding of molecular biology of cancer and identification of recurrent mutations in AML provide opportunities to develop targeted therapies and improve the clinical outcome. In the spectrum of identified gene mutations, primarily targetable lesions are gain of function mutations of tyrosine kinases FLT3, JAK2 and cKIT for which specific, dual and multi-targeted small molecule inhibitors have been developed. A number of targeted compounds such as sorafenib, quizartinib, lestaurtinib, midostaurin, pacritinib, PLX3397 and CCT137690 are in clinical development. For loss-of-function gene mutations, which are mostly biomarkers of favorable prognosis, combined therapeutic approaches can maximize the therapeutic efficacy of conventional therapy. Apart from mutated gene products, proteins aberrantly overexpressed in AML appear to be clinically significant therapeutic targets. Such a molecule for which targeted inhibitors are currently in clinical development is PLK1. We review characteristic gene mutations, discuss their biological functions and clinical significance and present small molecule compounds in clinical development, which are expected to have a role in treating AML subtypes with characteristic molecular alterations.

Non-coding RNAs and EZH2 interactions in cancer: long and short tales from the transcriptome

A large amount of data indicates that non-coding RNAs represent more than the "dark matter" of the genome. Both microRNAs and long non-coding RNAs are involved in several fundamental biologic processes, and their deregulation may lead in oncogenesis. Interacting with the Polycomb-repressive complex 2 subunit EZH2, they could affect the expression of protein-coding genes and form feedback networks and autoregulatory loops. They can also form networks with upstream and downstream important factors, in which EZH2 represent the stabilizing factor of the pathway. As such non-coding RNAs affect the epigenetic modifications leading to malignant transformation.

The microRNAs within the DLK1-DIO3 genomic region: involvement in disease pathogenesis

The mammalian genome is transcribed in a developmentally regulated manner, generating RNA strands ranging from long to short non-coding RNA (ncRNAs). NcRNAs generated by intergenic sequences and protein-coding loci, represent up to 98 % of the human transcriptome. Non-coding transcripts comprise short ncRNAs such as microRNAs, piwi-interacting RNAs, small nucleolar RNAs and long intergenic RNAs, most of which exercise a strictly controlled negative regulation of expression of protein-coding genes. In humans, the DLK1-DIO3 genomic region, located on human chromosome 14 (14q32) contains the paternally expressed imprinted genes DLK1, RTL1, and DIO3 and the maternally expressed imprinted genes MEG3 (Gtl2), MEG8 (RIAN), and antisense RTL1 (asRTL1). This region hosts, in addition to two long intergenic RNAs, the MEG3 and MEG8, one of the largest microRNA clusters in the genome, with 53 miRNAs in the forward strand and one (mir-1247) in the reverse strand. Many of these miRNAs are differentially expressed in several pathologic processes and various cancers. A better understanding of the pathophysiologic importance of the DLK1-DIO3 domain-containing microRNA cluster may contribute to innovative therapeutic strategies in a range of diseases. Here we present an in-depth review of this vital genomic region, and examine the role the microRNAs of this region may play in controlling tissue homeostasis and in the pathogenesis of some human diseases, mostly cancer, when aberrantly expressed. The potential clinical implications of this data are also discussed.

Asymptomatic T-cell large granular lymphocyte leukemia with an unusual immunophenotype

T-cell large granular lymphocyte (T-LGL) leukemia represents a clonal proliferation of cytotoxic T-cells which etiology has not been entirely elucidated. However, CD4⁺, CD4⁻, CD8⁻, CD4⁺, CD8⁺ cases have been described. The disease is usually characterized by cytopenias and a modest lymphocytosis. The majority of patients with T-LGL leukemia remains asymptomatic for a long period and will require treatment later during the course of their disease. Hereby we describe a case of T-LGL leukemia diagnosed by flow cytometry, which presented indolent course and required no treatment so far.

Deregulated microRNAs in multiple myeloma

MicroRNAs are short noncoding RNAS involved in gene expression regulation under physiological and pathological situations. They bind to mRNA of target genes and are potential regulators of gene expression at a post-transcription level through the RNA interference pathway. They are estimated to represent 1% to 2% of the known eukaryotic genome, and it has been demonstrated that they are involved in the pathogenesis of neurodegenerative diseases, cancer, metabolism disorders, and heart disease. MicroRNAs are known to act as tumor suppressors or oncogenes in cancer biology. The authors describe the current knowledge on microRNA involvement in regulatory pathways that characterize multiple myeloma pathogenesis gained from in vitro and in vivo studies. These small molecules interact with important factors such as p53, SOCS1, IGF-1, IGF-1R, vascular endothelial growth factor, NF-κB, and others. As such, microRNAs represent an attractive therapeutic target in the context of multiple myeloma interfering with the myeloma regulatory networks. Further studies are needed to better understand their role in myelomagenesis and their therapeutic potential.

MEG3 imprinted gene contribution in tumorigenesis

Maternally expressed gene 3 (MEG3) is a maternally expressed imprinted gene representing a large noncoding RNA in which microRNAs (miRNAs) and small nucleolar RNAs are also hosted. It is capable of interacting with cyclic AMP, p53, murine double minute 2 (MDM2) and growth differentiation factor 15 (GDF15) playing a role in cell proliferation control. MEG3 expression is under epigenetic control, and aberrant CpG methylation has been observed in several types of cancer. Moreover, gene copy number loss has been reported as additional mechanism associated with tumorigenesis. MEG3 deletion seems to upregulate the paternally expressed genes and on the other hand downregulate the expression of downstream maternally expressed genes and tumor suppressor miRNAs, although there are conflicting data on the topic. MEG3 could represent a tumor suppressor gene located in chromosome 14q32 and its association with tumorigenesis is growing every day.

Polo-like kinase 2 (SNK/PLK2) is a novel epigenetically regulated gene in acute myeloid leukemia and myelodysplastic syndromes: genetic and epigenetic interactions

Polo-like kinase 2 (SNK/PLK2), a transcriptional target for wild-type p53 and is hypermethylated in a high percentage of multiple myeloma and B cell lymphomas patients. Given these data, we sought to study the methylation status of the specific gene in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), and to correlate it with clinical and genetic features. Using methylation-specific PCR MSP, we analyzed the methylation profile of 45 cases of AML and 43 cases of MDS. We also studied the distribution of MTHFR A1298C and MTHFR C677T polymorphisms and FLT3 mutations in AML patients and correlated the results with hypermethylation in the SNK/PLK2 CpG island. The SNK/PLK2 CpG island was hypermethylated in 68.9% and 88.4% of AML and MDS cases, respectively. Cases with hypermethylation had a trend towards more favorable overall survival (OS). There was no association between different MTHFR genotypes and susceptibility to develop AML. SNK/PLK2 hypermethylation combined with the MTHFR AA1298 genotype was associated with a tendency for a better OS. Similarly, patients with SNK/PLK2 hypermethylation combined with the MTHFR CT677 polymorphism had a better OS (HR = 0.34; p = 0.017). SNK/PLK2 methylation associated with unmutated FLT3 cases had a trend for better OS compared to patients with mutated FLT3 gene. SNK/PLK2 is a novel epigenetically regulated gene in AML and MDS, and methylation occurs at high frequency in both diseases. As such, SNK/PLK2 could represent a potential pathogenetic factor, although additional studies are necessary to verify its exact role in disease pathogenesis.

Study of specific genetic and epigenetic variables in multiple myeloma

Few studies have examined the association between methylenetetrahydrofolate reductase (MTHFR) SNPs, epigenetic changes, and multiple myeloma (MM). We wished to determine genotype distributions for MTHFR 1298AC SNP in cases of MM and healthy controls and to examine whether there is any correlation between the methylation status of the CpG island of CDKN2A and Snk/Plk2 and MTHFR genotypes and with overall survival (OS) and other relevant clinical parameters. Bone marrow and peripheral blood were obtained from 45 patients with MM and 77 controls, respectively. The frequencies of the MTHFR 1298AA, 1298AC, and 1298CC genotypes were 53.3%, 40%, and 6.7% for the patient population and 50.6%, 41.6%, and 7.8% for the controls. No statistically significant difference was found in genotype distribution between cases and controls. No correlation was noted between MTHFR genotypes and OS, disease stage, bone disease, anemia, and extramedullary disease. Regarding CDKN2A and Snk/Plk2 CpG island methylation analysis, we found 12 of 45 patients and 27 of 45, respectively, to be methylated. CDKN2A and Snk/Plk2 methylation did not correlate with MTHFR genotypes. Herein, we report the identification of Snk/Plk2 as a novel methylated gene in MM and show that methylation is not influenced in this CpG island or in that of a previously described methylated gene, CDKN2A, in MM. Further evaluation in a larger sample of patients is needed in order to better define the prognostic and clinical value, if any, of MTHFR 1298 polymorphisms and CDKN2A and Snk/Plk2 methylation in the pathogenesis of MM.

CpG methylation analysis of the MEG3 and SNRPN imprinted genes in acute myeloid leukemia and myelodysplastic syndromes

Methylation is now established as a fundamental regulator of gene transcription. To investigate this in haematologic malignancies, we evaluated the aberrant promoter methylation of two imprinted genes (MEG3 and SNRPN) in 43 MDS and 42 AML patients. MEG3 hypermethylation occurred in 15 MDS patients (34.9%), and in 20 AML patients (47.6%). SNRPN hypermethylation was observed in 15 MDS patients (34.9%), and in 21 AML patients (50%). There were no significant correlations between WHO subtype, WPSS score, karyotype, haemoglobin levels, white blood cell count, platelet count and CpG methylation of any gene. MEG3 hypermethylation was associated with significantly reduced overall survival in individuals with AML (HR=1.98, p=0.04), while SNRPN CpG methylation was not associated with survival (HR=0.94, p=0.87). In addition, no association between survival and aberrant MEG3 (HR=2.15, p=0.072) or SNRPN methylation (HR=1.08, p=0.85) was observed in patients MDS. Our findings suggest that these genes are abnormally methylated in AML and MDS patients, and methylation of MEG3 confers worse overall prognosis. The MEG3 methylation status may serve as a useful biomarker in leukemia.

Von Hippel-Lindau methylation status in patients with multiple myeloma: a potential predictive factor for the development of bone disease

It has been suggested that during multiple myeloma (MM) progression, a proangiogenesis stress response occurs, but the mechanistic basis of this has not been established. It is an attractive hypothesis that loss of expression of the von Hippel-Lindau (VHL) gene, resulting in constitutive activation of hypoxia-inducible factor-1alpha (HIF-1alpha), contributes to increased angiogenesis in MM. Because aberrant methylation in the VHL CpG island could cause downregulation of VHL transcription, we prospectively studied the methylation status of the VHL CpG island in 45 individuals with multiple myeloma (MM; 25 men, 20 women; mean age, 66.4 years) and in 10 individuals with borderline thrombocytopenia, who were proven to have no malignancy and served as controls. Methylation was found in 15 of 45 patients with MM at diagnosis (33.3%). The presence of methylation in the VHL CpG island was significantly associated with the development of bone disease (odds ratio, 7.5; P = .018). Patients with bone disease had an increased risk of death compared with those with no bone lytic lesions (hazard ratio [HR], 5.1; P = .13). VHL methylation was not a predictor of excess mortality (HR, 0.92; P = .91). Our data imply that methylation in the VHL CpG island is a frequent event in patients with MM and might be a potential biomarker of bone disease. Methylation in the VHL CpG island, leading to transcriptional silencing and hence decreased HIF-1alpha proteolysis, could be a possible mechanism of increased angiogenesis and altered bone marrow microenvironment that is more supportive for survival and growth of MM cells, contributing to MM bone disease. Whether it represents an early or late event of the disease merits additional study. Additional studies regarding the serum levels of HIF-1alpha and vascular endothelial growth factor would be mechanistically interesting.

Snk/Plk2 CpG methylation in patients with multiple myeloma

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Background: We previously showed that polo like kinase 2 (Snk/Plk2) is subject to methylation-dependent transcriptional silencing in a very high frequency in Burkitt lymphomas. Here, we have examined CpG methylation in Snk/Plk2 in a well-characterized series of multiple myeloma (MM) patients. Methods: Bone marrow samples from individuals with MM were obtained at diagnosis and in 5 cases at disease progression as well. Genomic DNA was isolated and bisulphite modification was performed using commercially available kits. The methylation-specific polymerase chain reaction (MSP) was employed to study its methylation status. Control methylated and unmethylated genomic DNAs were included in each experiment. Ten bone marrow samples from individuals proven to have no haematological malignancy, served as negative controls. Logistic regression analyses were used to measure the association between gene methylation and the development of advanced disease (DS≥II), extramedullary disease, bone disease, anemia (Hb 10 mg/dl), serum albumin and beta 2 microglobulin levels. Results: We analyzed the methylation of Snk/Plk2 in 45 cases of MM (24 male, 21 female, mean age 66.4 years ±12.4). Classical cytogenetic analysis was available in 30/45 patients and none of them was found to have chromosome 13 abnormalities. No sample from the control population was found methylated. The Snk/Plk2 promoter was found to be methylated in 27/45 patients (60%). Median survival of patients in whom the Snk/Plk2 CpG island was methylated was 7.1 years compared to a median survival of 8.8 years for unmethylated. However Snk/Plk2 methylation was not a predictor of excess mortality (HR=0.6, p=0.5), bone lytic lesions (OR=0.56, p=0.3), anemia (OR=0.5, p=0.3) or advanced stage as defined above (OR=0.8, p=0.7). Conclusions: Snk/Plk2 DNA Methylation is a frequent event in patients with multiple myeloma. There was no association between the methylation status of the gene and relevant clinical parameters. Further evaluation in a larger sample of patients is needed in order to better define the prognostic and clinical value if any of Snk/Plk2 methylation in MM.

No significant financial relationships to disclose.

Absence of methylation-dependent transcriptional silencing in TP73 irrespective of the methylation status of the CDKN2A CpG island in plasma cell neoplasia

Few studies exist regarding the methylation status of the TP73 CpG island in plasma cell dyscrasias. We have tested whether CpG methylation of both CDKN2A and TP73 occurs in 45 individuals with multiple myeloma (24 male and 21 female, mean age 66.4 years) and in 4 patients (2 male and 2 female, mean age 61.7 years) with Waldenström's macroglobulinemia. No patient was found to be methylated for the promoter of TP73 while CDKN2A promoter was found to be methylated in 12/45 MM patients (26.6%) at diagnosis and in 1/4 WM patients. To verify the absence of detectable methylation observed using MSP, we performed bisulphite sequence analysis on a subset of the cases and confirmed the absence of methylation. Interesting trends were identified where patients with methylated CDKN2A had an increased risk of death (HR = 1.9, p = 0.32), advanced stage disease (DS > or = II) (OR = 1.9, p = 0.3) and anemia (OR = 1.4, p = 0.6). TP73 CpG methylation is an infrequent event in patients with MM and WM. Further evaluation in a larger sample of patients is needed in order to enhance our statistical power and to test our hypothesis that CDKN2A methylation status can become a useful prognostic biomarker.

Promoter hypermethylation of the MEG3 (DLK1/MEG3) imprinted gene in multiple myeloma

BACKGROUND

Methylation represents the most studied epigenetic modification and results in the silencing of genes involved in various processes such as differentiation and cell-cycle regulation. MEG3 represents an imprinted gene maternally expressed in humans that encodes a nontranslated product. In this survey, we studied the methylation status of the specific gene in multiple myeloma (MM).

PATIENTS AND METHODS

Twenty-one patients with MM (17 with immunoglobulin [Ig] G, 3 with IgA, and 1 with IgM) were evaluated using methylation-specific polymerase chain reaction (after DNA bisulphite modification).

RESULTS

Promoter hypermethylation was observed in 12 (57.14%) bone marrow samples and in 9 of 14 (64.28%) available peripheral blood samples. A correlation with disease stage was also observed and also with the disease subtype (IgG, 64.7%; IgA, 0; IgM, 100%).

CONCLUSION

We conclude that promoter hypermethylation of the differentially methylated region of the MEG3 imprinted gene is observed in patients with MM.

Malignancies in beta-thalassemia patients: a single-center experience and a concise review of the literature

Thalassemia represents the world's most common monogenic disease, characterized by absence of or decreased globin chain production. The lifespan of thalassemia patients has been extended as a result of current supportive treatment. We report three cases of cancer (non-Hodgkin lymphoma, Hodgkin disease, and seminoma) in thalassemic patients. Factors that may contribute to the pathogenesis of cancer seem to be infections and iron overload through mechanisms of oxidative damage; immunomodulation or coexistence of the two diseases may only be coincidental.

Spontaneous splenic haematoma in a multiple myeloma patient receiving pegfilgrastim support

Growth factors are a significant advance in the supportive care of patients with cancer with a wide range of indications. Frequent side effects of G-CSF include bone pain, headache, fatigue and nausea. We report a case of subcapsular splenic haematoma following pegfilgrastim administration in a 65-year old patient with multiple myeloma. Proposed mechanisms accounting for splenic enlargement include extramedullary haemopoiesis, intrasplenic infiltration by mature and immature myeloid cells and intrasplenic stem cell homing and proliferation. The risk of spontaneous splenic rupture is difficult to quantify. Physicians should be aware of this life-threatening condition and early diagnosis can be difficult since anemia and splenomegaly are common findings in haematologic patients.