Acquired copy-neutral loss of heterozygosity of chromosome 1p as a molecular event associated with marrow fibrosis in MPL-mutated myeloproliferative neoplasms

Key Points In MPL exon 10–mutated myeloproliferative neoplasms, the MPL-mutant allele burden varies considerably from about 1% to almost 100%. High mutation burdens originate from acquired copy-neutral loss of heterozygosity of chromosome 1p and are associated with marrow fibrosis.

Download Full-text

Copy-Neutral Loss-of-Heterozygosity Adds Diagnostic and Prognostic Information to the Molecular Profiling of Hematological Malignancies

Blood ◽

10.1182/blood-2021-152195 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2228-2228

Author(s):

Wencke Walter ◽

Heiko Müller ◽

Claudia Haferlach ◽

Constance Baer ◽

Stephan Hutter ◽

...

Keyword(s):

Loss Of Heterozygosity ◽

Mutant Allele ◽

Neutral Loss ◽

Simultaneous Detection ◽

Prognostic Information ◽

Allele Burden ◽

Myeloid Neoplasms ◽

Lymphoid Neoplasms ◽

Recurrent Mutations ◽

Relevant Gene

Abstract Background: Copy-neutral loss-of-heterozygosity (CN-LOH) - not detectable by chromosome banding analysis - is gaining importance as a prognostic factor and can either cause the duplication of an activating mutation in an oncogene, the deletion of a tumor suppressor gene or the gain/loss of specific methylated regions. However, examination for possible CN-LOH in hematological diagnostics is at present not routinely performed and, hence, data regarding the occurrence of CN-LOH across different entities as well as the association of relevant genes is limited. Aim: (1) Frequency assessment of CN-LOH by target enrichment sequencing (TES) in a diagnostic setting, (2) evaluation of whole genome sequencing (WGS) data to estimate the prevalence of CN-LOH in a larger cohort, to pinpoint relevant genes for CN-LOHs with so far unknown associations, and to determine cross-entity variability. Patients and Methods: 1196 patients (507 female, 689 male, median age: 66 years), sent between 04/2021-07/2021 for diagnostic work-up, were analyzed by TES with a median coverage of 1765x for the gene panel and 52x for the CNV spike-in panel (IDT, Coralville, IA). Amplification-free WGS libraries of 3851 different patients were sequenced with a median coverage of 102x. Reads were aligned to the human reference genome (GRCh37, Ensembl annotation, Isaac aligner). Cnvkit (v 0.9.9) was used to call copy number variations (CNVs) and CN-LOH for TES and HadoopCNV (Yang et al. 2017) was used to call CN-LOH for WGS. Results: 1196 patients were analyzed by TES. For 10% of the patients at least one CN-LOH event was detected without any association to age or gender but a slightly higher incidence in myeloid compared to lymphoid neoplasms (10% vs 6%). In 14 patients, CN-LOH affected more than one chromosome arm. CN-LOH occurred most frequently in 4q (n = 15), 7q (n = 16), 9p (n = 25) and 11q (n = 10). As expected, 4q CN-LOH co-occurred with high variant allele frequencies (VAF) of TET2. Based on WGS data, 4q CN-LOH occurred predominately in AML (35%), CMML (22%), and MDS (20%). In rare cases, 4q CN-LOH was associated with FBXW7 variants in T-ALL. 7q CN-LOH occurred nearly exclusively in myeloid neoplasms (95%) and was associated with high VAFs in EZH2 in 69% of TES and 82% of WGS cases. CUX1 variants with high VAFs were detected in 80% (TES) and 45% (WGS) of the remaining cases, respectively. The well-known 9p CN-LOH led to JAK2V617F homozygosity in all myeloid neoplasms and occurred most often in MPNs. In T-ALL, regions of 9p CN-LOH harbored CDKN2A/B deletions. 11q CN-LOH occurred more often in myeloid than lymphoid neoplasms (79% vs 21%) and was associated with CBL variants in 61% and KMT2A-PTD in 19% of the cases. In contrast, ATM was the relevant gene in all lymphoid cases with 11q CN-LOH. CN-LOH in 11p was detected less frequently and only in 25% of cases an association with WT1 variants could be identified. Our WGS data confirmed the known associations between 1p CN-LOH and high allele burden in MPL, CSF3R and NRAS, 2p CN-LOH and DNMT3A variants, 13q CN-LOH and FLT3-ITD, the near exclusive occurrence of 16p CN-LOH in follicular lymphoma (FL, 98%) with high CREBBP-mutant allele burden , 17p CN-LOH and TP53 homozygosity, and the exclusive occurrence of 21q CN-LOH in AML and its association with RUNX1 mutations. Besides, 12q CN-LOH was associated with KMT2D in FL, with SH2B3 in MDS/MPN overlaps and in rare cases with KDM2B. For 17q CN-LOH the relevant gene was not unequivocally identifiable with high mutant allele variants in SRSF2, STAT5B, and NF1. 18q CN-LOH was a very rare event but consistently associated with a high VAF of MBD2, which presumably influences cell proliferation (Cheng et al. 2018). 19q CN-LOH was mostly (63%) associated with a high VAF of CEBPA variants, except for patients with hairy cell leukemia: in these cases nonsense mutations in CIC (VAF > 90%) were detected. CN-LOH in 22q was more common in myeloid malignancies (65% vs 35%) and associated with PRR14L mutations in the majority of myeloid cases (62%). Of note, this association occurred neither in AML samples nor in lymphoid neoplasms. No recurrent mutations were found for 6p and 14q CN-LOHs. For all other chromosomes, CN-LOH events were very rare. Conclusions: By using a CNV spike-in panel, TES adds additional diagnostic and prognostic information by enabling simultaneous detection of selected gene mutations and genome-wide CNVs, as well as CN-LOH, without increase in sequencing costs and turn-around times. Figure 1 Figure 1. Disclosures Haferlach: MLL Munich Leukemia Laboratory: Other: Part ownership. Kern: MLL Munich Leukemia Laboratory: Other: Part ownership. Haferlach: MLL Munich Leukemia Laboratory: Other: Part ownership.

Download Full-text

Clonal Analysis of SF3B1, JAK2 and MPL in Refractory Anemia with Ring Sideroblasts Associated with Marked Thrombocytosis

Blood ◽

10.1182/blood.v120.21.172.172 ◽

2012 ◽

Vol 120 (21) ◽

pp. 172-172

Author(s):

Ilaria Ambaglio ◽

Anna Gallì ◽

Daniela Pietra ◽

Matteo G Della Porta ◽

Marta Ubezio ◽

...

Keyword(s):

Mutant Allele ◽

Somatic Mutations ◽

Myeloproliferative Neoplasms ◽

Jak2 V617f ◽

Refractory Anemia ◽

Wild Type ◽

Mutation Status ◽

Allele Burden ◽

Ring Sideroblasts ◽

Exon 10

Abstract Abstract 172 Somatic mutations of the RNA splicing machinery have been recently identified in patients with myelodysplastic syndrome (MDS). In particular, a strong association has been found between SF3B1 mutation and the MDS subtype defined as refractory anemia with ring sideroblasts (RARS). Similarly, within myelodysplastic/myeloproliferative neoplasms (MDS/MPN) a high prevalence of SF3B1 mutations has been reported in the provisional entity defined as refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T). These findings strongly support a causal relationship between SF3B1 mutations and ring sideroblasts. Interestingly, a high proportion of RARS-T patients also harbor JAK2 and/or MPL mutations. The available evidence suggests that somatic mutations of SF3B1 might be an early pathogenetic event determining myelodysplastic features, and that subsequent occurrence of JAK2 and/or MPL mutations may cause the myeloproliferative phenotype. In this work, we studied the mutation status of SF3B1, JAK2 and MPL in circulating granulocytes and bone marrow cells from RARS-T patients. We also studied the in vitro growth of hematopoietic progenitors (BFU-E, CFU-GM), and genotyped individual colonies to examine the mutation status of the above genes. The coding exons of SF3B1 were screened using massively parallel pyrosequencing. A real time PCR-based allelic discrimination assay was used for the detection of JAK2 (V617F), while Sanger sequencing was employed for JAK2 exon 12 and MPL exon 10 mutation analysis. Twenty-eight patients affected with RARS-T were assessed for SF3B1, JAK2 and MPL exon 10 mutation status. Eighteen patients (64%) showed somatically acquired mutation of SF3B1. The median mutant allele burden was 43%, consistent with the presence in the majority of patients of clonal hematopoiesis characterized by a dominant clone carrying a heterozygous SF3B1 mutation. Fourteen patients carried the JAK2 (V617F) mutation (median allele burden 6.5%, range 0.4–29.5%), while one had a JAK2 exon 12 mutation. In 13 cases, the JAK2 mutation was detected at the time of diagnosis, whereas in 2 patients, who had a typical RARS phenotype and were negative for JAK2 mutations at clinical onset, JAK2 (V617F) was detected 18 and 32 months after diagnosis, respectively, and concomitantly with a progressive increase in platelet count. Four patients, two of whom were JAK2 (V617F)-positive, carried the MPL (W515L) mutation (median allele burden 27.5%, range 25–50%). Concomitant mutations of SF3B1 and JAK2 or MPL were observed in 8 cases. Seven patients carried an SF3B1 mutation and JAK2 (V617F), while one carried SF3B1 (K700E), JAK2 (V617F), and MPL (W515L). In all these cases, the SF3B1 mutant allele burden was higher than that of JAK2 or MPL, indicating the existence of an SF3B1-mutated dominant clone with minority JAK2- or MPL-mutated clones. We genotyped individual colonies from peripheral blood in 2 patients with concomitant mutations. In a patient with granulocyte SF3B1 and JAK2 mutant allele burdens equal to 45% and 8%, respectively, SF3B1 (H662Q) was detected in 9 of 11 colonies, three of which also carried JAK2 (V617F); the remaining two colonies had wild type SF3B1 and JAK2. These data are consistent with the existence of a dominant hematopoietic clone carrying the SF3B1 mutation and the subsequent emergence of a JAK2-mutated subclone. The other patient, who was initially SF3B1- mutated and JAK2 wild type, at the time of colony assay had a mutant allele burden equal to 50% and 1% for SF3B1 (K700E) and JAK2 (V617F), respectively. Forty-three of 45 colonies were heterozygous for SF3B1 (K700E) and wild type for JAK2. The opposite pattern was observed in the remaining 2 colonies, which carried just JAK2 (V617F). These data indicate the coexistence of two distinct clones, a dominant one carrying the SF3B1 mutation and a minority one carrying JAK2 (V617F). In summary, these observations suggest that the occurrence of an SF3B1 mutation represents an early event in patients with RARS-T, likely causing mitochondrial iron overload, ring sideroblasts, ineffective erythropoiesis and anemia, typical myelodysplastic features. The subsequent occurrence of a somatic mutation of JAK2 or MPL involves the emergence of minority clones and the acquisition of myeloproliferative features. JAK2- mutated clones may emerge as subclones of the dominant SF3B1-mutated clone or as independent clones. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Using the Minor Variant Finder software to identify and quantify the allelic burden level of somatic mutations in oncohematologic diseases

Oncohematology ◽

10.17650/1818-8346-2020-15-2-85-91 ◽

2020 ◽

Vol 15 (2) ◽

pp. 85-91

Author(s):

T. N. Subbotina ◽

I. E. Maslyukova ◽

A. A. Faleeva ◽

P. A. Nikolaeva ◽

A. S. Khazieva ◽

...

Keyword(s):

Mutant Allele ◽

Sanger Sequencing ◽

Quantitative Assessment ◽

Somatic Mutations ◽

Myeloproliferative Neoplasms ◽

Mutant Gene ◽

Positive Sample ◽

Allele Burden ◽

Minor Variant ◽

Allelic Burden

Background. There are problems related to both quantitative assessment of an allele burden level of a mutant gene and interpretation of results in DNA samples with the burden level of the mutant allele less than 15–20 %, when using Sanger sequencing for analyzing somatic mutations. Applied Biosystems (USA) has developed new software Minor Variant Finder, which allows determining mutations with the allele burden level from 5 %.The objective: to determine the allele burden level and identification of minor variants of somatic mutations in the ASXL1, JAK2 genes and BCR-ABL oncogene using Minor Variant Finder software in patients with myeloproliferative neoplasms.Materials and methods. The level of mutant allele burden for 15 patients with myeloproliferative neoplasms was determined by the identified mutations using the Minor Variant Finder software, after analysis of point somatic mutations in the ASXL1, JAK2 genes and BCR-ABL oncogene by Sanger sequencing.Results. The allele burden level in all 5 ASXL1-positive samples and BCR-ABL-positive sample was determined as higher than 20 % using the Minor Variant Finder software. The allele burden level in 2 cases was higher than 20 % and in 7 cases lower than 20 %, when we analyzed 9 JAK2-positive samples.Conclusion. Minor Variant Finder software can be used to estimate the allele burden level and to identify minor variants of somatic mutations in the ASXL, JAK2 and BCR-ABL genes.

Download Full-text

Loss of heterozygosity 4q24 and TET2 mutations associated with myelodysplastic/myeloproliferative neoplasms

Blood ◽

10.1182/blood-2009-02-205690 ◽

2009 ◽

Vol 113 (25) ◽

pp. 6403-6410 ◽

Cited By ~ 252

Author(s):

Anna M. Jankowska ◽

Hadrian Szpurka ◽

Ramon V. Tiu ◽

Hideki Makishima ◽

Manuel Afable ◽

...

Keyword(s):

Loss Of Heterozygosity ◽

Chromosomal Abnormalities ◽

Myeloproliferative Neoplasms ◽

Neutral Loss ◽

Regulatory Gene ◽

Clinical Analysis ◽

Gene Marker ◽

Compound Heterozygous ◽

Single Nucleotide ◽

Myeloid Malignancies

Abstract Chromosomal abnormalities are frequent in myeloid malignancies, but in most cases of myelodysplasia (MDS) and myeloproliferative neoplasms (MPN), underlying pathogenic molecular lesions are unknown. We identified recurrent areas of somatic copy number–neutral loss of heterozygosity (LOH) and deletions of chromosome 4q24 in a large cohort of patients with myeloid malignancies including MDS and related mixed MDS/MPN syndromes using single nucleotide polymorphism arrays. We then investigated genes in the commonly affected area for mutations. When we sequenced TET2, we found homozygous and hemizygous mutations. Heterozygous and compound heterozygous mutations were found in patients with similar clinical phenotypes without LOH4q24. Clinical analysis showed most TET2 mutations were present in patients with MDS/MPN (58%), including CMML (6/17) or sAML (32%) evolved from MDS/MPN and typical MDS (10%), suggesting they may play a ubiquitous role in malignant evolution. TET2 mutations affected conserved domains and the N terminus. TET2 is widely expressed in hematopoietic cells but its function is unknown, and it lacks homology to other known genes. The frequency of mutations in this candidate myeloid regulatory gene suggests an important role in the pathogenesis of poor prognosis MDS/MPN and sAML and may act as a disease gene marker for these often cytogenetically normal disorders.

Download Full-text

Clinical Implications for Patients with Low JAK2V617F Allele Burden

Blood ◽

10.1182/blood.v120.21.1745.1745 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1745-1745

Author(s):

Marguerite Vignon ◽

Dorota Jeziorowska ◽

Pierre Hirsch ◽

Ollivier Legrand ◽

Nicole Casadevall ◽

...

Keyword(s):

Bone Marrow ◽

Clinical Phenotype ◽

Myeloproliferative Neoplasms ◽

Kinase Domain ◽

Jak2 Mutation ◽

Allele Burden ◽

Vein Thrombosis ◽

Myeloid Neoplasms ◽

Exon 10 ◽

Jak2v617f Allele Burden

Abstract Abstract 1745 In classical Philadelphia-negative myeloproliferative neoplasms (MPN), JAK2V617F is considered as a driver mutation when the threshold of 1% JAK2V617F/JAK2total allele burden is reached. However a lower ratio is sometimes detected with highly sensitive assays. We investigated the clinical significance of such minor clones by describing the characteristics of 27 patients with a low JAK2V617F allele burden ranging from 0.1% to 0.99%. Material and Methods A commercially available quantitative ASO-PCR assay of 0.1% sensitivity (MutaQuant® kit, Ipsogen) was used. Two thousand five hundred consecutive blood samples were sent to our lab for JAK2V617F mutation between 2009 and 2012. Total blood DNA was extracted by an automated standardized procedure (Qiasymphony®, Qiagen). All samples were tested in duplicate. The 27 samples of our cohort were controlled using a second assay of 0.01% sensitivity (Larsen et al, BJH 2007). Thirty samples from healthy donors were also tested. High resolution melting curve (HRM) analysis of JAK2 exon 14 ruled out the possibility of an additional mutation hampering the annealing of a primer. Patients with a known classical MPN clinical phenotype were also tested for JAK2 exons 12–17 (entire pseudo-kinase domain) or for MPL exon 10 depending on the context. Results Laboratory Findings Among the 2500 samples, 735 (29.4%) were positive above 1%, 27 (1.1%) had low JAK2V617F allele burden ranging from 0.12 to 0.99%. The patient with the lowest ratio (0.12%) was not confirmed by the second assay and therefore was excluded from the study. This allowed the median to settle at 0.40%. No associated mutations were found in the JAK2 pseudo-kinase domain in patients with polycythemia vera (PV) and in MPL exon 10 in patients with essential thrombocytosis (ET) and primary myelofibrosis (PMF). Healthy patients were all tested JAK2V617F negative. Clinical Aspects The cohort included 19 men and 7 women ranging from 28 to 95 years of age (median 63 years old). Two patients had secondary acute myeloid leukaemia following JAK2V617F positive MPN indicating the presence of residual JAK2V617F cells and the negativity of the myeloblastic population. Thirteen patients (50%) had a classical MPN with a median ratio of 0.36%: 7 ET, 5 PV and 1 PMF according to WHO 2008 criteria. However a bone marrow biopsy was available for only two patients (1 ET, 1 PMF). None of them had received pegylated interferon alpha-2a. Four patients had a prior history of thrombosis: two strokes, one pulmonary embolism, two portal vein thrombosis (PVT). For one PV patient, a 6 months follow-up blood and bone marrow sample confirmed a low allele burden in the same range (0.4%) and in vitro Epo-independant erythroid colonies were observed. Five patients had other chronic myeloid neoplasms (two myelodysplastic/myeloproliferative neoplasms, one chronic eosinophilic leukaemia, one chronic myeloid leukaemia, one refractory anaemia with ring sideroblasts). Among these five, four had an abnormal karyotype. We did not observe any thrombotic event in these patients. We cannot conclude on hematological diagnosis for the last six patients: four patients were screened for JAK2 mutation because of PVT. One patient had chronic polycythemia in a context of alcohol and tobacco abuse. One patient had homozygous hemochromatosis with a normal haemoglobin level in spite of repeated phlebotomies. Discussion In this single centre study low JAK2V617F allele burden represented 1% of all samples sent for JAK2V617F study and 3.5% of JAK2V617F positive patients. Seventeen patients (65%) had classical MPN or splanchnic vein thrombosis. To our knowledge PV patients with such low JAK2V617F allele burden have not been reported in the absence of associated JAK2 pseudo-kinase domain mutation. A larger screen for cooperating mutations responsible for the PV phenotype is under process. In the context of other chronic myeloid neoplasms, the JAK2V617F mutation is thought to belong to a more complex clonal architecture mostly implicating chromatin remodeling genes. Here, the presence of a JAK2 mutation could argue in favour of clonal haematopoiesis. In conclusion the clinical phenotype of low JAK2V617F patients overlaps with classical JAK2V617F MPN. The technical implications might be challenging for molecular diagnostic platforms. More data are needed to further characterize these patients. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

A Heterogeneous Response Pattern to Interferon-alpha2 with Induction of a Significant Decrease in the Calreticulin Mutant Allele Burden in a Subset of Patients with Essential Thrombocythemia and Primary Myelofibrosis

Blood ◽

10.1182/blood.v126.23.4057.4057 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4057-4057

Author(s):

Sabrina Cordua ◽

Lasse Kjaer ◽

Morten Orebo Holmström ◽

Niels Pallisgaard ◽

Vibe Skov ◽

...

Keyword(s):

Essential Thrombocythemia ◽

Mutant Allele ◽

Myeloproliferative Neoplasms ◽

Primary Myelofibrosis ◽

Allele Burden ◽

Travel Grant ◽

Ifn Treatment

Abstract Introduction The discovery of mutations in the calreticulin (CALR) gene in the majority of JAK2 -V617F negative patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF) (Klampfl et al., 2013; Nangalia et al., 2013) has improved the diagnostic accuracy considerably, and most recently distinct clinical and hematological characteristics according to mutational status have been described (Park et al., 2015). The perspective is to personalize and optimize treatment according to the molecular and clinical landscape. This may be achieved by obtaining more information on responses in myeloproliferative neoplasms (MPN) to existing treatment strategies as assessed by the allele burden. Mutations in the CALR gene have proven to play a major role in oncogenic and immunologic processes (Lu, Weng, & Lee, 2015). In this context, it is highly relevant to explore the effectiveness of interferon-alpha2 (IFN) in reducing the CALR -mutated clone. Until now, only one paper has reported a decrease in allele burden in two patients during IFN treatment (Cassinat, Verger, & Kiladijan, 2014). The objective of this report is to expand current knowledge on this important topic by describing the mutant CALR allele burden over time in a larger group of IFN-treated patients. Method Clinical data were collected retrospectively from a single institution on all IFN-treated CALR positive MPN patients with sequential determinations of the mutant allele burden. Type 1 and type 2 mutations were initially identified by a previously published fragment analysis (Klampfl et al 2013). We have developed a Taqman qPCR assay for precise determination of the mutant allele burden of type 1 and type 2 mutations. Stored DNA was subsequently analysed to increase follow-up time. Results Twenty-one patients were included. Fifteen patients had a diagnosis of PMF; 7 of these were diagnosed with prefibrotic myelofibrosis. Six patients had ET. The type 1 and 2 mutations were found in 15 and 6 patients, respectively. Median age was 60 years (range 42-79) and the sex ratio (M/F) was 8/13. Fifteen patients (71%) were in ongoing treatment with IFN, whereas treatment was discontinued in 6 (29%) because of side effects. Median time of IFN treatment was 756 days (range 42-3927). The IFN prescribed was either subcutaneous injection of Pegasys® (median: 45 microgram (ug) per week), PegIntron® 25-50 ug per week, or Multiferon® 3 x 3 million IU per week. Median follow up time since the first CALR measurement was 756 days (range 294-2108). Fourteen patients (67%) maintained an unchanged allele burden during follow up; 1 patient (5%) presented a temporary decrease (from 39% to 27% in allele burden) but increased to the initial level within months while still on IFN treatment (presumably due to low compliance); 1 patient (5%) displayed an increase in allele burden during transformation to acute myelogenous leukemia (Figure 1); and 5 patients (24%) exhibited a marked decrease in allele burden (median decrease: 32%, range 18-45) during treatment with IFN (Figure 2). All 5 patients with decreasing allele burden (Table 1) normalized their platelet counts within a median time of 5 weeks (range 4-20) after initiating treatment with IFN. Conclusion Using a novel sensitive assay for the CALR mutant allele burden, we have demonstrated and substantiated the effectiveness of IFN to reduce the allele burden in a larger series of CALR positive patients with PMF and ET. Importantly, we report for the first time on highly heterogeneous response patterns. Our observation of one fourth of the CALR positive patients responding to treatment with IFN strongly suggests that IFN significantly influences the CALR mutational load. Further clinical and molecular studies are urgently needed to explore the mechanisms behind the heterogeneous response patterns and the clinical implications in regard to clonal evolution and disease progression in non-responding patients. We are currently analysing these issues to assess the definite role of IFN in future treatment strategies in CALR positive MPN patients. Table 1. Patients responding to interferon-alpha2 Characteristics Number/median (range) Patients 5 Age, years 53 (42-62) Sex (M/F) 1/4 Diagnosis- Essential thrombocythemia- Primary myelofibrosis- Prefibrotic myelofibrosis 221 Calreticulin mutation type- type 1- type 2 50 Duration of interferon-alpha2 treatment, days 960 (177-2790) Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Cordua: Janssen-Cilag: Other: travel grant. Off Label Use: interferon alpha2 for myeloproliferative neoplasms. Holmström:La Roche Ltd: Other: travel grant. Pallisgaard:Qiagen: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Other: travel grant, Speakers Bureau; Bristol Meyer Squibb: Speakers Bureau; Novartis: Other: travel grant, Research Funding, Speakers Bureau; Roche: Other: travel grant. Hasselbalch:Novartis: Research Funding.

Download Full-text

JAK2 p.V617F detection and allele burden measurement in peripheral blood and bone marrow aspirates in patients with myeloproliferative neoplasms

Blood ◽

10.1182/blood-2013-07-515676 ◽

2013 ◽

Vol 122 (23) ◽

pp. 3784-3786 ◽

Cited By ~ 17

Author(s):

Koichi Takahashi ◽

Keyur P. Patel ◽

Hagop Kantarjian ◽

Rajyalakshmi Luthra ◽

Sherry Pierce ◽

...

Keyword(s):

Bone Marrow ◽

Sensitivity And Specificity ◽

Peripheral Blood ◽

Myeloproliferative Neoplasms ◽

Allele Burden ◽

Key Points

Key Points The sensitivity and specificity of detecting the JAK2 p.V617F mutation in PB are both 100% compared with BM. The JAK2 p.V617F allele burden measured in PB is equivalent to that in BM aspirate (R2 = 0.991; P < .0001).

Download Full-text

Nonfamilial,MPLS505N-Mutated Essential Thrombocythaemia

Case Reports in Hematology ◽

10.1155/2013/729327 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Ruth Morrell ◽

Stephen E. Langabeer ◽

Liam Smyth ◽

Meegahage Perera ◽

Gerard Crotty

Keyword(s):

Bone Marrow ◽

Clinical Features ◽

Clinical Course ◽

Myeloproliferative Neoplasms ◽

Significant Proportion ◽

Essential Thrombocythaemia ◽

Bone Marrow Fibrosis ◽

Thrombotic Risk ◽

Exon 10 ◽

Marrow Fibrosis

Mutations ofMPLare present in a significant proportion of patients with the myeloproliferative neoplasms (MPN), primary myelofibrosis (PMF), and essential thrombocythaemia (ET). The most frequent of these mutations, W515L and W515K, occur in exon 10 ofMPL, which encodes the receptor for thrombopoietin. Another exon 10 mutation,MPLS505N, has been shown to be a founder mutation in several pedigrees with familial thrombocythaemia where it is associated with a high thrombotic risk, splenomegaly and progression to bone marrow fibrosis. Rare cases of sporadic, nonfamilial,MPLS505N MPN have been documented, but the presenting laboratory and clinical features have not been described in detail. The diagnosis and clinical course of a case ofMPLS505N-positive MPN are presented with diagnostic features and treatment response resembling typical ET but with evidence of increasing bone marrow fibrosis. Further MPN cases possessing this genotype require reporting in order to ascertain whether any particular morphological or clinical features, if present, determine clinical course and aid the refinement of therapeutic options.

Download Full-text

Lysine-Specific Histone Demethylase, LSD1, (KDM1A) As a Novel Therapeutic Target in Myeloproliferative Neoplasms

Blood ◽

10.1182/blood.v126.23.601.601 ◽

2015 ◽

Vol 126 (23) ◽

pp. 601-601 ◽

Cited By ~ 2

Author(s):

Maria Kleppe ◽

Kaitlyn Shank ◽

Papalexi Efthymia ◽

Hugh Riehnhoff ◽

Ross L. Levine

Keyword(s):

Mutant Allele ◽

Myeloproliferative Neoplasms ◽

Serum Levels ◽

Advisory Committees ◽

Allele Burden ◽

Circulating Cells ◽

Cell Counts ◽

White Blood Cell Counts ◽

The Impact

Abstract Among BCR-ABL-negative myeloproliferative neoplasms (MPN), primary myelofibrosis (PMF) and post PV/ET myelofibrosis (MF) are associated with the highest degree of morbidity and mortality, including progressive bone marrow (BM) fibrosis and resultant BM failure. Although the JAK inhibitor ruxolitinib is now approved for the treatment of MF-associated splenomegaly and systemic symptoms, JAK inhibitor therapy does not reduce the proportion of JAK2-mutant cells in MPN patients. The limited ability of JAK inhibition to induce molecular or clinicopathologic responses in the majority of MPN patients underscores the need for the development of more effective therapies for JAK kinase-dependent malignancies. Recent studies have shown that the lysine-specific histone demethylase, LSD1 (KDM1A), participates in the balance between proliferation and differentiation in vivo by influencing state-specific gene expression patterns. In physiologic hematopoiesis, LSD1 is essential for normal myeloid differentiation affecting the erythroid, megakaryocytic and granulocytic lineages. Small molecule inhibitors of LSD1 have shown promising results in preclinical models of acute myeloid leukemia (AML) and solid cancers and have recently entered clinical trials in AML. However, the role and requirement for LSD1 in the pathogenesis of MPNs and the therapeutic targeting of LSD1 in MPN has not been investigated. In this study, we first tested the effects of IMG-98, a potent, selective LSD1 inhibitor, in the MPLW515L-driven ET/MF mouse model. After disease was established, mice were treated with IMG-98 or vehicle for 28 days. LSD1 inhibition in mice markedly suppressed myeloproliferation reducing granulocyte counts and spleen weights compared to mice treated with vehicle thus establishing therapeutic efficacy (Fig. 1a). Pathologic analysis of BM and spleen confirmed a marked reduction in myeloproliferation as well as a reversal of extramedullary hematopoiesis (EMH). Most notably, we observed a marked reduction in reticulin fibrosis with IMG-98 treatment (Fig. 1b). We next investigated the impact of IMG-98 therapy on inflammatory cytokine signaling; in contrast to the broad anti-cytokine effects of JAK1/2 inhibition, we observed a more specific anti-cytokine effect of IMG-98, a significant reduction in the secretion of the inflammatory cytokine Cxcl5 (Fig. 1c), a key participant in pathologic inflammatory states. We then investigated the in vivo impact of IMG-98 therapy on mutant disease burden. IMG-98 therapy reduced mutant allele burden to a degree not seen with JAK1/2 inhibitor therapy: whereas 74.6% of circulating cells in mice treated with vehicle were GFP-positive cells, only 43.2% of circulating cells were GFP-positive in IMG-98-treated mice (Fig. 1d). Flow cytometry analysis of spleen and BM revealed reduced numbers of CD11b/Gr1-positive myeloid cells and CD41-positive megakaryocytes. The numbers of mutant GFP-positive myeloid cells and megakaryocytes in these tissues were also significantly reduced by IMG-98 treatment. Studies of the impact of LSD1 inhibition on MPN stem cell function and on epigenetic regulation in MPN cells will be presented in detail. In summary, the LSD1 inhibitor IMG-98 had a highly significant therapeutic effect in an established preclinical model of ET/MF. LSD1 inhibition in diseased mice reduced JAK-STAT-driven myeloproliferation, markedly reversed EMH and BM fibrosis, and reduced the mutant clone burden. These data suggest LSD1 is a valid target in MPN and that clinical studies of LSD1 inhibitor IMG-98 alone and in combination with JAK inhibitors are warranted. Figure 1. a, b) LSD1 inhibition results in reduced white blood cell counts (WBC) and platelet counts (PLT). (a), and in near-complete elimination of BM fibrosis (b). c) Profound reduction of Cxcl5 serum levels in IMG-98 treated mice compared to vehicle treated mice. d) Significantly lower mutant allele burden in the peripheral blood of IMG-98 treated mice. * P<0.05, n =5. Figure 1. a, b). LSD1 inhibition results in reduced white blood cell counts (WBC) and platelet counts (PLT). (a), and in near-complete elimination of BM fibrosis (b). c) Profound reduction of Cxcl5 serum levels in IMG-98 treated mice compared to vehicle treated mice. d) Significantly lower mutant allele burden in the peripheral blood of IMG-98 treated mice. * P<0.05, n =5. Disclosures Riehnhoff: Imago: Employment, Equity Ownership. Levine:Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy.

Download Full-text