Karolien Beel

Loss or Inhibition of Stromal-Derived PlGF Prolongs Survival of Mice with Imatinib-Resistant Bcr-Abl1+ Leukemia

Imatinib has revolutionized the treatment of Bcr-Abl1(+) chronic myeloid leukemia (CML), but, in most patients, some leukemia cells persist despite continued therapy, while others become resistant. Here, we report that PlGF levels are elevated in CML and that PlGF produced by bone marrow stromal cells (BMSCs) aggravates disease severity. CML cells foster a soil for their own growth by inducing BMSCs to upregulate PlGF, which not only stimulates BM angiogenesis, but also promotes CML proliferation and metabolism, in part independently of Bcr-Abl1 signaling. Anti-PlGF treatment prolongs survival of imatinib-sensitive and -resistant CML mice and adds to the anti-CML activity of imatinib. These results may warrant further investigation of the therapeutic potential of PlGF inhibition for (imatinib-resistant) CML.

A large kindred with X-linked neutropenia with an I294T mutation of the Wiskott-Aldrich syndrome gene

X‐linked neutropenia (XLN, OMIM #300299) is a rare form of severe congenital neutropenia. It was originally described in a three‐generation family with five affected members that had an L270P mutation in the GTP‐ase binding domain (GBD) of the Wiskott‐Aldrich syndrome protein (WASP) [ Devriendt et al (2001) Nature Genetics, Vol. 27, 313–317 ]. Here, we report and describe a large three‐generation family with XLN, with 10 affected males and eight female carriers. A c.882T>C mutation was identified in the WAS gene, resulting in an I294T mutation. The infectious course is variable and mild in view of the profound neutropenia. In addition to the original description, low‐normal IgA levels, low to low‐normal platelet counts and reduced natural killer (NK)‐cell counts also appear as consistent XLN features. However, inverted CD4/CD8 ratios were not found in this family, nor were cases identified with myelodysplastic syndrome or acute myeloid leukaemia. Female carriers exhibited a variable attenuated phenotype. Like L270P WASP, I294T WASP is constitutively active towards actin polymerization. In conclusion, this largest XLN kindred identified to date provides new independent genetic evidence that mutations disrupting the auto‐inhibitory GBD of WASP are the cause of XLN. Reduced NK cells, low to low normal platelet counts and low to low‐normal IgA levels are also features of XLN.

G-CSF receptor (CSF3R) mutations in X-linked neutropenia evolving to acute myeloid leukemia or myelodysplasia

This paper shows for the first time that patients with X-linked neutropenia, caused by mutations in the Wiskott Aldrich syndrome gene, developed myelodysplasia/acute myeloid leukemia with acquisition of mutations in the CSF3R gene and loss of chromosome 7. See related perspective article on page 1333. X-linked neutropenia (XLN) is a rare form of Congenital Neutropenia (CN) caused by inherited gain-of-function mutations of WAS. Here we report 2 cases of the original L270P X-linked neutropenia kindred that evolved to MDS or AML, with acquisition of G-CSFR (CSF3R) mutations and monosomy 7. Thus, leukemic transformation with acquisition of CSF3R mutations and monosomy 7 is not restricted to classical congenital neutropenia with autosomal inheritance, but can also occur in other genotypes of inherited neutropenia.

Severe congenital neutropenia, a genetically heterogeneous disease group with an increased risk of AML/MDS

Over the past decade, enormous progress has been made in the understanding of severe congenital neutropenia (SCN), by identification of several causal gene mutations: in ELANE, GFI1, HAX1, WAS and G3PC3. SCN is a preleukemic condition, independent of the genetic subtype. Acquired CSF3R mutations are specific for SCN and are strongly associated with malignant progression. In this review, we describe the known genetic subtypes of SCN, their molecular basis and clinical presentation and summarize the available evidence on CSF3R mutations and monosomy 7 in malignant conversion.

CML with e6a2 BCR-ABL1 transcript: an aggressive entity?

Dear Editor, The BCR-ABL1 fusion gene is characteristic of CML. Four different breakpoint cluster regions (bcr) have been described in BCR. The most common BCR breakpoints, in 95% of CML cases, occur in M-BCR, i.e., introns 13 or 14, resulting in an e13a2 (b2a2) or an e14a2 (b3a2) BCR-ABL1 transcript. “Atypical” transcripts, e8a2, e19a2, e13a3, e14a3, e1a3, and e6a2 BCR-ABL1, account for less than 1% of CML cases [1, 2]. Only 11 CML patients have been reported with the e6a2 variant. A male predominance and a worse outcome have been suggested for this variant [3]. Here, we describe an additional CML case with an e6a2 fusion transcript. This 57-year-old male patient presented with hepatosplenomegaly, weight loss, cough, and fever. Laboratory examination showed a hemoglobin level of 12.1 g/dL, a white blood cell count of 43.5×10*9/L with 5% myeloblasts and 10% eosinophils, a platelet count of 129×10*9/L, and an LDH of 3,363 U/L (normal value, 313–618 U/L). An abdominal CT scan confirmed the hepatomegaly (craniocaudal diameter of 24 cm) and splenomegaly (bipolar diameter of 20 cm). Sokal score was 2.11, and Hasford score, 2,211.6 (both high risk). Bone marrow aspirate showed a hypocellular marrow with 10% myeloblasts and marked eosinophilia. On trephine biopsy, a myeloproliferative disease with striking fibrosis was seen. Taqman RQ-PCR was negative for e13a2/e14a2 transcripts and weakly positive for the e1a2 transcript in peripheral blood. A subsequent cytogenetic analysis showed the t(9;22)(q34;q11) translocation in all metaphases and trisomy of chromosome 8 in 6 out of 10 metaphases, indicating clonal evolution. Fluorescent in situ hybridization (FISH), using the Vysis LSI BCR/ABL1 extra signal dual color translocation probe, revealed, in addition to the expected fusion signal on der(22), a small fusion on der(9), further suggesting the presence of a variant breakpoint, located centromeric to M-BCR (Fig. 1). Qualitative reverse transcription polymerase chain reaction (RT-PCR), using forward primers in BCR exon 1 and reverse primers in ABL1 exon 2, confirmed the presence of a variant transcript of 502 bp. This was identified as e6a2 after Sanger sequencing. Based on these findings, a diagnosis of CML in an accelerated phase was made, and the patient was started on imatinib 600 mg daily. Three months later, while still on imatinib, he was readmitted with CML in blast crisis. He had cutaneous chloromas, severe abdominal pain, a productive cough, and life-threatening dyspnea, necessitating intubation and mechanical ventilation. Peripheral leukocyte count was 465× 10*9/L with 29% myeloblasts; he had severe anemia (Hb, 6.5 g/L), thrombocytopenia (75×10*9/L), and an LDH of 10,612 U/L. Chest CT scan revealed multiple pathologically enlarged mediastinal and hilar lymph nodes. Fundoscopic examination showed features of hyperviscosity. Peripheral blood karyotype and FISH now showed an extra derivative der(22)t(9;22) in ~50% of cells. Following leukapheresis and PV is a senior clinical investigator of the Fund for Scientific ResearchFlanders (Belgium) (FWO Vlaanderen). K. A. Beel : J. Maertens Department of Hematology, Internal Medicine, University Hospital Leuven, Leuven, Belgium

Reduction of BCR-ABL1 mutant clones after discontinuation of TKI therapy

In this letter we describe two case reports of CML patients with acquired mutations of the BCR-ABL1 kinase domain, in whom the mutant clone regressed and drug sensitivity was restored after temporary interruption of TKI. We believe that temporary interruption of an ATP-competitive tyrosine kinase inhibitor and switching to non-selective therapy can be a valid therapeutic option in CML patients. In addition, we highlight the potential of a flow cytometric CRKL phosphorylation assay to explore TKI sensitivity in CML cells ex vivo, and its correlation with clinical and haematological sensitivity or resistance.

Results from the Belgian mantle cell lymphoma registry.

Introduction: Mantle cell lymphoma is a B-cell non-Hodgkin’s lymphoma characterized by a t(11;14), resulting in overexpression of cyclin D1. Conventional chemotherapy obtains frequent (but short) remissions, leading to a poor median overall survival (OS) of 3–5 years. To obtain more information about the prevalence and current treatment of Mantle cell lymphoma (MCL) in Belgium, we collected data in a Belgian registry of MCL. Materials and methods: All Belgian MCL patients, t(11;14) and/or cyclin D1 positive, seen in hematology departments over a one-year period (April 2013–March 2014) were included. Data about patient characteristics, histology, treatment lines, and response were compiled and retrospectively analyzed. Results: Four hundred and four patients were included with a median age at diagnosis of 64 years (range 23–96 years) and a male predominance (72%). For 2013, we calculated a prevalence of at least 36.2 per million and an incidence of at least 7.0 per million in the Belgian population. Characteristics at diagnosis involved lymphadenopathy (82%), splenomegaly (44%), B-symptoms (39%), and hepatomegaly (10%). Bone marrow invasion was present at diagnosis in 77%. Stage at diagnosis was advanced in the majority of cases. The median number of treatment lines was 1. Type of first line treatment included a combination of anthracyclin and cytarabine-based regimen (34%), anthracyclin (39%), and other. Rituximab was used in 88% of first line treatments. In 44% first line treatment was followed by autologous stem cell transplantation. Conclusion: The analysis of this Belgian MCL registry provides insight in the epidemiology, demographics, and current treatment of our Belgian MCL population.