Identification of small-molecule ERBB4 agonists for the treatment of heart failure

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Dehousse fellowship

Introduction

Although progress has been made in the treatment of heart failure, morbidity and mortality remain high, requiring new therapeutic targets. The neuregulin-1 (NRG1)/ERBB4 axis is cardioprotective and antifibrotic when activated in the myocardium, and therefore a possible target for therapy. Phase 2 and 3 clinical trials with NRG1 are ongoing, but require intravenous administration regimens, limiting applicability and efficacy.

Purpose

To develop small-molecule ERBB4 agonists with cardioprotective and antifibrotic properties.

Methods

A high-throughput screening (HTS) of 10,240 compounds was performed on a ERBB4/ERBB4 dimerization assay. Hit compounds were co-administered with NRG1 or fluorescently labeled NRG1 to determine competitive binding. Selectivity, receptor phosphorylation, cell proliferation and toxicity were determined using Luminex RTK phosphoprotein, ERBB2/ERBB3 dimerization, WST-1 colorimetric, and adenylate kinase assays. Antifibrotic effects were studied in vitro on TGF-β-induced collagen synthesis in human dermal and atrial fibroblasts, and in a mouse model of angiotensin II (AngII, 1000 ng/kg/min)-induced left ventricular (LV) myocardial fibrosis with selected compounds (83 µg/kg/h), administrated with osmotic minipumps (N=4–5/group). mRNA expression was evaluated after 7 days; LV myocardial fibrosis area, cardiomyocyte cross sectional area (CSA), echocardiographic parameters and heart- to bodyweight ratio (HW:BW) were analyzed at 28 days. Antiapoptotic effects were studied on rat atrial cardiomyocytes (AM) after hydrogen peroxide (H2O2)-induced cardiotoxicity.

Results

The HTS (Z’=0.7) resulted in 8 similar pyrimidine derivatives (EF-1–8) inducing ERBB4/ERBB4 dimerization (Emax 9–33% relative to NRG1, EC50 6E-6 to 2E-7 M). Competition assays indicate allosteric binding. The compounds also significantly potentiated NRG1-induced ERBB4 receptor dimerization up to 2.7 fold. Two compounds were excluded because of in vitro toxicity. The other 6 compounds were non-toxic and induced ERBB4, but neither ERBB1, ERBB2 or ERBB3 phosphorylation, nor tumor growth–inducing ERBB2/ERBB3 dimerization. Selected compounds showed significant dose-dependent antiapoptotic properties on H2O2-stimulated AM, and antifibrotic effects on human atrial and dermal fibroblasts. In vivo, compound EF-1 significantly decreased myocardial fibrosis (by 76±26%) and Col1a1, Col3a1 (-70±17%; -61±20%), and Nppa (-78±32%) mRNA expression, and significantly enhanced cardiomyocyte CSA (+24±8%). No differences were observed in cardiac function or HW:BW ratio.

Conclusion

We identified novel pyrimidine derivative small-molecule ERBB4 agonists with cardiomyocyte protective effects and antifibrotic properties in vitro and in AngII-induced myocardial fibrosis in vivo.

Mutant JAK3 phosphoproteomic profiling predicts synergism between JAK3 inhibitors and MEK/BCL2 inhibitors for the treatment of T-cell acute lymphoblastic leukemia

Mutations in the interleukin-7 receptor (IL7R) or the Janus kinase 3 (JAK3) kinase occur frequently in T-cell acute lymphoblastic leukemia (T-ALL) and both are able to drive cellular transformation and the development of T-ALL in mouse models. However, the signal transduction pathways downstream of JAK3 mutations remain poorly characterized. Here we describe the phosphoproteome downstream of the JAK3(L857Q)/(M511I) activating mutations in transformed Ba/F3 lymphocyte cells. Signaling pathways regulated by JAK3 mutants were assessed following acute inhibition of JAK1/JAK3 using the JAK kinase inhibitors ruxolitinib or tofacitinib. Comprehensive network interrogation using the phosphoproteomic signatures identified significant changes in pathways regulating cell cycle, translation initiation, mitogen-activated protein kinase and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT signaling, RNA metabolism, as well as epigenetic and apoptotic processes. Key regulatory proteins within pathways that showed altered phosphorylation following JAK inhibition were targeted using selumetinib and trametinib (MEK), buparlisib (PI3K) and ABT-199 (BCL2), and found to be synergistic in combination with JAK kinase inhibitors in primary T-ALL samples harboring JAK3 mutations. These data provide the first detailed molecular characterization of the downstream signaling pathways regulated by JAK3 mutations and provide further understanding into the oncogenic processes regulated by constitutive kinase activation aiding in the development of improved combinatorial treatment regimens.

Characterization of the genome-wide TLX1 binding profile in T-cell acute lymphoblastic leukemia

The TLX1 transcription factor is critically involved in the multi-step pathogenesis of T-cell acute lymphoblastic leukemia (T-ALL) and often cooperates with NOTCH1 activation during malignant T-cell transformation. However, the exact molecular mechanism by which these T-cell specific oncogenes cooperate during transformation remains to be established. Here, we used chromatin immunoprecipitation followed by sequencing to establish the genome-wide binding pattern of TLX1 in human T-ALL. This integrative genomics approach showed that ectopic TLX1 expression drives repression of T cell-specific enhancers and mediates an unexpected transcriptional antagonism with NOTCH1 at critical target genes, including IL7R and NOTCH3. These phenomena coordinately trigger a TLX1-driven pre-leukemic phenotype in human thymic precursor cells, reminiscent of the thymus regression observed in murine TLX1 tumor models, and create a strong genetic pressure for acquiring activating NOTCH1 mutations as a prerequisite for full leukemic transformation. In conclusion, our results uncover a functional antagonism between cooperative oncogenes during the earliest phases of tumor development and provide novel insights in the multi-step pathogenesis of TLX1-driven human leukemia.

Gene expression profiling reveals clear differences between EBV-positive and EBV-negative posttransplant lymphoproliferative disorders

Posttransplant patients are at risk of developing a potentially life-threatening posttransplantation lymphoproliferative disorder (PTLD), most often of diffuse large B cell lymphoma (DLBCL) morphology and associated with Epstein-Barr Virus (EBV) infection. The aim of this study was to characterize the clinicopathological and molecular-genetic characteristics of posttransplant DLBCL and to elucidate whether EBV(+) and EBV(-) posttransplant DLBCL are biologically different. We performed gene expression profiling studies on 48 DLBCL of which 33 arose posttransplantation (PT-DLBCL; 72% EBV+) and 15 in immunocompetent hosts (IC-DLBCL; none EBV+). Unsupervised hierarchical analysis showed clustering of samples related to EBV-status rather than immune status. Except for decreased T cell signaling these cases were inseparable from EBV(-) IC-DLBCL. In contrast, a viral response signature clearly segregated EBV(+) PT-DLBCL from EBV(-) PT-DLBCL and IC-DLBCL cases that were intermixed. The broad EBV latency profile (LMP1+/EBNA2+) was expressed in 59% of EBV(+) PT-DLBCL and associated with a more elaborate inflammatory response compared to intermediate latency (LMP1+/EBNA2-). Inference analysis revealed a role for innate and tolerogenic immune responses (including VSIG4 and IDO1) in EBV(+) PT-DLBCL. In conclusion we can state that the EBV signature is the most determining factor in the pathogenesis of EBV(+) PT-DLBCL.

Role of GRB2-associated binder 1 in epidermal growth factor receptor-induced signaling in head and neck squamous cell carcinoma

The epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of head and neck squamous cell carcinoma (HNSCC). Despite the high expression of EGFR in HNSCC, EGFR inhibitors have only limited success as monotherapy. The Grb2-associated binder (GAB) family of adaptor proteins acts as docking/scaffolding molecules downstream of tyrosine kinase receptors. We hypothesized that GAB1 may amplify EGFR-induced signaling in HNSCCs and therefore could play a role in the reduced sensitivity of HNSCC to EGFR inhibitors. We used representative human HNSCC cell lines overexpressing wild type EGFR, and expressing GAB1 but not GAB2. We demonstrated that baseline Akt and MAPK signaling were reduced in HNSCC cells in which GAB1 expression was reduced. Furthermore, the maximal EGF-induced activation of the Akt and MAPK pathway was reduced and delayed, and the duration of the EGF-induced activation of these pathways was reduced in cells with GAB1 knock-down. In agreement with this, HNSCC cells in which GAB1 levels were reduced showed an increased sensitivity to the EGFR inhibitor gefitinib. Our work demonstrates that GAB1 plays an important role as part of the mechanism of by which EGFR induces induced activation of the MAPK and AKT pathway. Our results identify GAB1 as an amplifier of the EGFR-initiated signaling, which may also interfere with EGFR degradation. These findings support the emerging notion that reducing GAB1 function may sensitize HNSCC to EGFR inhibitors, hence representing a new therapeutic target HNSCC treatment in combination with EGFR targeting agents.

Identification and characterization of novel oncogenes in chronic eosinophilic leukemia and T-cell acute lymphoblastic leukemia

Research conducted in my group in the period 2006-2009 has led to a better understanding of the oncogenic mechanisms of the FIP1L1-PDGFRA and NUP214-ABL1 oncogenes. Insights into these mechanisms may help us to design novel strategies to treat leukemia. In addition, we have identified the small molecule inhibitor sorafenib as a potent inhibitor of the FIP1L1-PDGFRA and its T674I imatinib resistant mutant. Sorafenib was originally developed as a BRAF inhibitor, but our work demonstrates that sorafenib can also be used to treat FIP1L1-PDGFRA positive leukemia, demonstrating that new therapies to treat rare leukemias may be simply found by testing drugs that are already in use for the treatment of other diseases. Finally, using genome-wide screening approaches, we have identified the MYB gene as a novel oncogene implicated in the pathogenesis of T-ALL, and we suggest that MYB may represent a novel target for therapy in T-ALL as well as in other cancers.

Heterogeneous patterns of amplification of the NUP214-ABL1 fusion gene in T-cell acute lymphoblastic leukemia

Episomes with the NUP214-ABL1 fusion gene have been observed in 6% of T-ALL. In this multicentric study we collected 27 cases of NUP214-ABL1-positive T-ALL. Median age was 15 years with male predominance. Outcome was poor in 12 patients. An associated abnormality involving TLX1 or TLX3 was found in all investigated cases. Fluorescent in situ hybridization revealed a heterogeneous pattern of NUP214-ABL1 amplification. Multiple episomes carrying the fusion were detected in 24 patients. Episomes were observed in a significant number of nuclei in 18 cases, but in only 1-5% of nuclei in 6. In addition, intrachromosomal amplification (small hsr) was identified either as the only change or in association with episomes in four cases and two T-ALL cell lines (PEER and ALL-SIL). One case showed insertion of apparently non-amplified NUP214-ABL1 sequences at 14q12. The amplified sequences were analyzed using array-based CGH.These findings confirm that the NUP214-ABL1 gene requires amplification for oncogenicity; it is part of a multistep process of leukemogenesis; and it can be a late event present only in subpopulations. Data also provide in vivo evidence for a model of episome formation, amplification and optional reintegration into the genome. Implications for the use of kinase inhibitors are discussed.

Intrinsic differences between the catalytic properties of the oncogenic NUP214-ABL1 and BCR-ABL1 fusion protein kinases

The NUP214-ABL1 fusion kinase has recently been identified in 6% of patients with T-cell acute lymphoblastic leukemia. In contrast to the more common oncogenic ABL1 fusion BCR-ABL1, NUP214-ABL1 localizes to the nuclear pore complexes and has attenuated transforming properties in hematopoietic cells and in mouse bone marrow transplant models. We have performed a thorough biochemical comparative analysis of NUP214-ABL1 and BCR-ABL1 and show that, despite their common tyrosine kinase domain, the two fusion proteins differ in many critical catalytic properties. NUP214-ABL1 has lower in vitro tyrosine kinase activity, which is in agreement with the absence of phosphorylation on its activation loop. NUP214-ABL1 was more sensitive to imatinib (Glivec) than BCR-ABL1 in vitro and in cells, indicating a different activation state and conformation of the two ABL1 fusion kinases. Using a peptide array, we identified differences in the spectrum and efficiency of substrate peptide phosphorylation and a differential involvement of Src kinases in downstream signaling. These results clearly indicate that different fusion partners of the same kinase can determine not only localization, but also critical functional properties of the enzyme such as inhibitor sensitivity and substrate preference, with subsequent differences in downstream signaling effectors and likely consequences in disease pathogenesis.

Activity of tyrosine kinase inhibitors against human NUP214-ABL1-positive T cell malignancies

Amplification of the NUP214-ABL1 oncogene can be detected in patients with T cell acute lymphoblastic leukemia (T-ALL). We screened 29 patients with T cell malignancies for the expression of NUP214-ABL1 by reverse transcription-polymerase chain reaction (RT-PCR). NUP214-ABL1 was detected in three (10%) patients. These results were confirmed by fluorescence in situ hybridization techniques. We also studied the activity of imatinib, nilotinib and dasatinib against the human NUP214-ABL1-positive cell lines PEER and BE-13. All three tyrosine kinase inhibitors decreased the viability of PEER and BE-13 cells, but nilotinib and dasatinib had >1-log lower IC(50) values than imatinib (P<0.001). In contrast, the NUP214-ABL-negative T-ALL cell line Jurkat, was remarkably resistant to tyrosine kinase inhibition. The inhibition of cellular proliferation was associated with time-dependent induction of apoptosis and inhibition of ABL, CrKL and STAT5 phosphorylation. Moreover, dasatinib was active in a NUP214-ABL1-positive leukemia xenograft murine model and in marrow lymphoblasts from a patient with NUP214-ABL1-positive T-ALL. On the basis of these results, ABL1 kinase inhibitors warrant clinical investigation in patients with NUP214-ABL1-positive T-cell malignancies.

FIP1L1-PDGFRA in chronic eosinophilic leukemia and BCR-ABL1 in chronic myeloid leukemia affect different leukemic cells

We investigated genetically affected leukemic cells in FIP1L1-PDGFRA+ chronic eosinophilic leukemia (CEL) and in BCR-ABL1+ chronic myeloid leukemia (CML), two myeloproliferative disorders responsive to imatinib. Fluorescence in situ hybridization specific for BCR-ABL1 and for FIP1L1-PDGFRA was combined with cytomorphology or with lineage-restricted monoclonal antibodies and applied in CML and CEL, respectively. In CEL the amount of FIP1L1-PDGFRA+ cells among CD34+ and CD133+ cells, B and T lymphocytes, and megakaryocytes were within normal ranges. Positivity was found in eosinophils, granulo-monocytes and varying percentages of erythrocytes. In vitro assays with imatinib showed reduced survival of peripheral blood mononuclear cells but no reduction in colony-forming unit growth medium (CFU-GM) growth. In CML the BCR-ABL1 fusion gene was detected in CD34+/CD133+ cells, granulo-monocytes, eosinophils, erythrocytes, megakaryocytes and B-lymphocytes. Growth of both peripheral blood mononuclear cells and CFU-GM was inhibited by imatinib. This study provided evidence for marked differences in the leukemic masses which are targeted by imatinib in CEL or CML, as harboring FIP1L1-PDGFRA or BCR-ABL1.

Clinical, cytogenetic and molecular characteristics of 14 T-ALL patients carrying the TCRβ-HOXA rearrangement: a study of the Groupe Francophone de Cytogénétique Hématologique

Recently, we and others described a new chromosomal rearrangement, that is, inv(7)(p15q34) and t(7;7)(p15;q34) involving the T-cell receptor beta (TCRbeta) (7q34) and the HOXA gene locus (7p15) in 5% of T-cell acute lymphoblastic leukemia (T-ALL) patients leading to transcriptional activation of especially HOXA10. To further address the clinical, immunophenotypical and molecular genetic findings of this chromosomal aberration, we studied 330 additional T-ALLs. This revealed TCRbeta-HOXA rearrangements in five additional patients, which brings the total to 14 cases in 424 patients (3.3%). Real-time quantitative PCR analysis for HOXA10 gene expression was performed in 170 T-ALL patients and detected HOXA10 overexpression in 25.2% of cases including all the cases with a TCRbeta-HOXA rearrangement (8.2%). In contrast, expression of the short HOXA10 transcript, HOXA10b, was almost exclusively found in the TCRbeta-HOXA rearranged cases, suggesting a specific role for the HOXA10b short transcript in TCRbeta-HOXA-mediated oncogenesis. Other molecular and/or cytogenetic aberrations frequently found in subtypes of T-ALL (SIL-TAL1, CALM-AF10, HOX11, HOX11L2) were not detected in the TCRbeta-HOXA rearranged cases except for deletion 9p21 and NOTCH1 activating mutations, which were present in 64 and 67%, respectively. In conclusion, this study defines TCRbeta-HOXA rearranged T-ALLs as a distinct cytogenetic subgroup by clinical, immunophenotypical and molecular genetic characteristics.

[A man with FIP1L1/PDGFRA-positive chronic eosinophilic leukemia]

A 39-year-old man was referred from Surinam to the Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands, for a right ventricular tumour, hypereosinophilia and mild thrombocytopenia. He appeared to have chronic eosinophilic leukaemia that was positive for the 'FIP1-like-1-platelet-derived growth factor receptor alpha' (FIP1L1-PDGFRA) gene. In addition, he had signs of a right ventricular thrombus that had existed for at least 6 months. The patient was treated with oral anticoagulants and the tyrosine kinase inhibitor imatinib. The latter therapy resulted in normalisation of leukocyte count and differential values. After 3 months of therapy, the FIP1L1-PDGFRA fusion transcript was no longer detectable in peripheral blood. After 1 year of follow up, the patient was in complete haematological and molecular remission for chronic eosinophilic leukaemia. The cardiac mass remained unchanged, but caused no haemodynamic problems.

Cytogenetics and molecular genetics of T-cell acute lymphoblastic leukemia: from thymocyte to lymphoblast

For long, T-cell acute lymphoblastic leukemia (T-ALL) remained in the shadow of precursor B-ALL because it was more seldom, and showed a normal karyotype in more than 50% of cases. The last decennia, intense research has been carried out on different fronts. On one side, development of normal thymocyte and its regulation mechanisms have been studied in multiple mouse models and subsequently validated. On the other side, molecular cytogenetics (fluorescence in situ hybridization) and mutation analysis revealed cytogenetically cryptic aberrations in almost all cases of T-ALL. Also, expression microarray analysis disclosed gene expression signatures that recapitulate specific stages of thymocyte development. Investigations are still very much actual, fed by the discovery of new genetic aberrations. In this review, we present a summary of the current cytogenetic changes associated with T-ALL. The genes deregulated by translocations or mutations appear to encode proteins that are also implicated in T-cell development, which prompted us to review the 'normal' and 'leukemogenic' functions of these transcription regulators. To conclude, we show that the paradigm of multistep leukemogenesis is very much applicable to T-ALL and that the different genetic insults collaborate to maintain self-renewal capacity, and induce proliferation and differentiation arrest of T-lymphoblasts. They also open perspectives for targeted therapies.

Molecular cytogenetic study of 126 unselected T-ALL cases reveals high incidence of TCRbeta locus rearrangements and putative new T-cell oncogenes

Chromosomal aberrations of T-cell receptor (TCR) gene loci often involve the TCRalphadelta (14q11) locus and affect various known T-cell oncogenes. A systematic fluorescent in situ hybridization (FISH) screening for the detection of chromosomal aberrations involving the TCR loci, TCRalphadelta (14q11), TCRbeta (7q34) and TCRgamma (7p14), has not been conducted so far. Therefore, we initiated a screening of 126 T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma cases and 19 T-ALL cell lines using FISH break-apart assays for the different TCR loci. Genomic rearrangements of the TCRbeta locus were detected in 24/126 cases (19%), most of which (58.3%) were not detected upon banding analysis. Breakpoints in the TCRalphadelta locus were detected in 22/126 cases (17.4%), whereas standard cytogenetics only detected 14 of these 22 cases. Cryptic TCRalphadelta/TCRbeta chromosome aberrations were thus observed in 22 of 126 cases (17.4%). Some of these chromosome aberrations target new putative T-cell oncogenes at chromosome 11q24, 20p12 and 6q22. Five patients and one cell line carried chromosomal rearrangements affecting both TCRbeta and TCRalphadelta loci. In conclusion, this study presents the first inventory of chromosomal rearrangements of TCR loci in T-ALL, revealing an unexpected high number of cryptic chromosomal rearrangements of the TCRbeta locus and further broadening the spectrum of genes putatively implicated in T-cell oncogenesis.

Chronic myeloproliferative disorders: a tyrosine kinase tale

Chronic myeloproliferative diseases (CMPDs) are characterized by the abnormal proliferation and survival of one or more myeloid cell types. The archetype of this class of hematological diseases is chronic myeloid leukemia (CML), characterized by the presence of the Philadelphia (Ph) chromosome, the result of t(9;22)(q34;q11), and the associated BCR-ABL1 oncogene. Some of the Ph-negative myeloproliferative diseases are characterized by other chromosomal translocations involving a variety of tyrosine kinase genes, including ABL1, ABL2, PDGFRA, PDGFRB, FGFR1, and JAK2. The majority of Ph-negative CMPDs, however, such as chronic eosinophilic leukemia, polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis are not characterized by the presence of recurrent chromosomal abnormalities. Recent studies have identified the FIP1L1-PDGFRA fusion gene, generated due to a small cryptic deletion on chromosome 4q12, and the activating V617F mutation in JAK2 in a significant fraction of Ph-negative CMPDs. These results show that abnormalities in tyrosine kinase genes are central to the molecular pathogenesis of CMPDs. Genome-wide screenings to identify novel tyrosine kinase abnormalities in CMPDs may contribute to further improvement of the diagnosis and the treatment of these diseases.

KIAA1509 is a novel PDGFRB fusion partner in imatinib-responsive myeloproliferative disease associated with a t(5;14)(q33;q32)

We report the cloning of a novel PDGFRB fusion gene partner in a patient with a chronic myeloproliferative disorder characterized by t(5;14)(q33;q32), who responded to treatment with imatinib mesylate. Fluorescence in situ hybridization demonstrated that PDGFRB was involved in the translocation. Long distance inversion PCR identified KIAA1509 as the PDGFRB fusion partner. KIAA1509 is an uncharacterized gene with a predicted coiled-coil oligomerization domain with homology to the HOOK family of proteins. The predicted KIAA1509-PDGFRbeta fusion protein contains the KIAA1509 coiled-coil domain fused to the cytoplasmic domain of PDGFRbeta that includes the tyrosine kinase domain. Imatinib therapy resulted in rapid normalization of the patient's blood counts, and subsequent bone marrow biopsies and karyotypic analysis were consistent with sustained complete remission.

A new recurrent inversion, inv(7)(p15q34), leads to transcriptional activation of HOXA10 and HOXA11 in a subset of T-cell acute lymphoblastic leukemias

Chromosomal translocations with breakpoints in T-cell receptor (TCR) genes are recurrent in T-cell malignancies. These translocations involve the TCRalphadelta gene (14q11), the TCRbeta gene (7q34) and to a lesser extent the TCRgamma gene at chromosomal band 7p14 and juxtapose T-cell oncogenes next to TCR regulatory sequences leading to deregulated expression of those oncogenes. Here, we describe a new recurrent chromosomal inversion of chromosome 7, inv(7)(p15q34), in a subset of patients with T-cell acute lymphoblastic leukemia characterized by CD2 negative and CD4 positive, CD8 negative blasts. This rearrangement juxtaposes the distal part of the HOXA gene cluster on 7p15 to the TCRbeta locus on 7q34. Real time quantitative PCR analysis for all HOXA genes revealed high levels of HOXA10 and HOXA11 expression in all inv(7) positive cases. This is the first report of a recurrent chromosome rearrangement targeting the HOXA gene cluster in T-cell malignancies resulting in deregulated HOXA gene expression (particularly HOXA10 and HOXA11) and is in keeping with a previous report suggesting HOXA deregulation in MLL-rearranged T- and B cell lymphoblastic leukemia as the key factor in leukaemic transformation. Finally, our observation also supports the previous suggested role of HOXA10 and HOXA11 in normal thymocyte development.

FIP1L1-PDGFR alpha, a therapeutic target for the treatment of chronic eosinophilic leukemia

The identification of the FIP1L1-PDGFRA fusion gene provides a molecular explanation for the pathogenesis of approximately half of the patients with the hypereosinophilic syndrome (HES). A diagnostic test to identify FIP1L1-PDGFRA positive HES cases (subsequently reclassified as chronic eosinophilic leukemia, CEL) is now available. FIP1L1-PDGFR alpha is a novel therapeutic target of the kinase inhibitor imatinib (Glivec, Novartis), which provides the basis for the treatment of these patients with this drug. FIP1L1-PDGFRA positive CEL patients respond very well to imatinib therapy, some of which are remarkable responses with normalization of the blood counts within 2 weeks after start of the therapy. Imatinib is well tolerated with minimal side effects, and most CEL patients respond to low doses of imatinib (100 mg/day), being important for lowering both the cost of therapy and drug related toxicity. All imatinib treated FIP1L1-PDGFRA positive CEL patients achieve hematological and cytogenetic remission, and the majority of patients also achieve a molecular remission with the fusion gene no longer detectable in blood, even by the most sensitive PCR techniques.

Fusion of NUP214 to ABL1 on amplified episomes in T-cell acute lymphoblastic leukemia

In T-cell acute lymphoblastic leukemia (T-ALL), transcription factors are known to be deregulated by chromosomal translocations, but mutations in protein tyrosine kinases have only rarely been identified. Here we describe the extrachromosomal (episomal) amplification of ABL1 in 5 of 90 (5.6%) individuals with T-ALL, an aberration that is not detectable by conventional cytogenetics. Molecular analyses delineated the amplicon as a 500-kb region from chromosome band 9q34, containing the oncogenes ABL1 and NUP214 (refs. 5,6). We identified a previously undescribed mechanism for activation of tyrosine kinases in cancer: the formation of episomes resulting in a fusion between NUP214 and ABL1. We detected the NUP214-ABL1 transcript in five individuals with the ABL1 amplification, in 5 of 85 (5.8%) additional individuals with T-ALL and in 3 of 22 T-ALL cell lines. The constitutively phosphorylated tyrosine kinase NUP214-ABL1 is sensitive to the tyrosine kinase inhibitor imatinib. The recurrent cryptic NUP214-ABL1 rearrangement is associated with increased HOX expression and deletion of CDKN2A, consistent with a multistep pathogenesis of T-ALL. NUP214-ABL1 expression defines a new subgroup of individuals with T-ALL who could benefit from treatment with imatinib.

Clinical and molecular features of FIP1L1-PDFGRA (+) chronic eosinophilic leukemias

Detection of the FIP1L1-PDGFRA fusion gene or the corresponding cryptic 4q12 deletion supports the diagnosis of chronic eosinophilic leukemia (CEL) in patients with chronic hypereosinophilia. We retrospectively characterized 17 patients fulfilling WHO criteria for idiopathic hypereosinophilic syndrome (IHES) or CEL, using nested RT-PCR and interphase fluorescence in situ hybridization (FISH). Eight had FIP1L1-PDGFRA (+) CEL, three had FIP1L1-PDGFRA (-) CEL and six had IHES. FIP1L1-PDGFRA (+) CEL responded poorly to steroids, hydroxyurea or interferon-alpha, and had a high probability of eosinophilic endomyocarditis (n=4) and disease-related death (n=4). In FIP1L1-PDGFRA (+) CEL, palpable splenomegaly was present in 5/8 cases, serum vitamin B(12) was always markedly increased, and marrow biopsies revealed a distinctively myeloproliferative aspect. Imatinib induced rapid complete hematological responses in 4/4 treated FIP1L1-PDGFRA (+) cases, including one female, and complete molecular remission in 2/3 evaluable cases. In the female patient, 1 log reduction of FIP1L1-PDGFRA copy number was reached as by real-time quantitative PCR (RQ-PCR). Thus, correlating IHES/CEL genotype with phenotype, FIP1L1-PDGFRA (+) CEL emerges as a homogeneous clinicobiological entity, where imatinib can induce molecular remission. While RT-PCR and interphase FISH are equally valid diagnostic tools, the role of marrow biopsy in diagnosis and of RQ-PCR in disease and therapy monitoring needs further evaluation.

The NPM-ALK and the ATIC-ALK fusion genes can be detected in non-neoplastic cells

Anaplastic large cell lymphoma (ALCL) is frequently associated with the t(2;5)(p23;q35) translocation. It creates a NPM-ALK fusion gene, fusing the anaplastic lymphoma kinase (ALK) gene (2p23) and the nucleophosmin (NPM) gene (5q35). Other rearrangements involving the ALK gene have recently been shown to be associated with ALCL, among which the ATIC-ALK rearrangement resulting from the inv(2)(p23q35) translocation is probably the most recurrent. The aims of the present study were to investigate the presence of NPM-ALK and ATIC-ALK fusion genes in ALCL, using a real-time 5' exonuclease-based reverse-transcription polymerase chain reaction (RT-PCR). This sensitive technique was also applied to investigate whether both fusion genes might be detected in Hodgkin's disease cases and in reactive lymphoid tissue. Results of the RT-PCR were compared to ALK immunostaining, cytogenetics, and fluorescence in situ hybridization (FISH) results. RT-PCR detected the NPM-ALK and ATIC-ALK fusions at high levels in 8 and 3 of a total of 13 ALK-positive ALCL cases. One ALK-positive ALCL case was negative for both fusion genes analyzed but revealed a new ALK-related translocation t(2;17)(p23;q25) by cytogenetic and FISH analysis. In addition, of the eight ALK-positive ALCL cases that were strongly positive for the NPM-ALK fusion, three cases also showed the presence of the ATIC-ALK fusion, although at much lower levels. Similarly, out of the three strongly positive ATIC-ALK cases, one case was positive for the NPM-ALK fusion, at low levels. Finally, the NPM-ALK and the ATIC-ALK fusions were detected, at equally low levels, respectively in 13 and 5 ALK-negative ALCL cases, in 11 and 5 Hodgkin's disease cases and in 20 and 1 non-neoplastic lymphoid tissues. The distinction between the high- and low-level detection was confirmed by relative quantitative RT-PCR for a representative number of cases. Of interest is the fact that the high-level detection coincided with the presence of ALK gene rearrangement detected by cytogenetics and FISH and may reflect a central role of the transcript in the oncogenic mechanism of ALK-positive ALCL. Low-level detection is not supported by cytogenetics and FISH, presumably due to the presence of the transcripts in only a small minority of normal cells not detectable by these techniques. Our findings demonstrate that NPM-ALK and ATIC-ALK fusion transcripts may be detected in conditions other than ALK-positive ALCL including reactive lymphoid tissues, although at low levels, suggesting the presence of the transcripts in normal (bystander) cells. Moreover, they suggest that the ALK gene rearrangement by itself might be insufficient to induce tumor formation. They further question the validity of quantitative real-time RT-PCR for monitoring minimal residual disease in ALCL. Finally, the newly identified translocation t(2;17)(p23;q25) can be added to the list of ALK gene rearrangements occurring in ALK-positive ALCL.

A new family of small, palmitoylated, membrane-associated proteins, characterized by the presence of a cysteine-rich hydrophobic motif

We recently cloned the CHIC2 gene (previously BTL) by virtue of its involvement in a chromosomal translocation t(4;12)(q11;p13) occurring in acute myeloid leukemias. In this study we show that CHIC2 is a member of a highly conserved family of proteins characterized by the presence of a striking cysteine-rich hydrophobic (CHIC) motif. Our data illustrate that cysteines in this central CHIC motif are palmitoylated and that CHIC2 is associated with vesicular structures and the plasma membrane. The CHIC proteins thus resemble the cysteine string proteins, which function in regulated exocytosis.

Inv(2)(p23q35) in anaplastic large-cell lymphoma induces constitutive anaplastic lymphoma kinase (ALK) tyrosine kinase activation by fusion to ATIC, an enzyme involved in purine nucleotide biosynthesis

The non-Hodgkin lymphoma (NHL) subtype anaplastic large-cell lymphoma (ALCL) is frequently associated with a t(2;5)(p23;q35) that results in the fusion of the ubiquitously expressed nucleophosmin (NPM) gene at 5q35 to the anaplastic lymphoma kinase (ALK) gene at 2p23, which is not normally expressed in hematopoietic tissues. Approximately 20% of ALCLs that express ALK do not contain the t(2;5), suggesting that other genetic abnormalities can result in aberrant ALK expression. Here we report the molecular characterization of an alternative genetic means of ALK activation, the inv(2)(p23q35). This recurrent abnormality produces a fusion of the amino-terminus of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC), a bifunctional homodimeric enzyme that catalyzes the penultimate and final steps of de novo purine nucleotide biosynthesis, with the intracellular portion of the ALK receptor tyrosine kinase. RT-PCR analysis of 5 ALCL tumors that contained the inv(2) revealed identical ATIC-ALK fusion cDNA junctions in all of the cases. Transient expression studies show that the ATIC-ALK fusion transcript directs the synthesis of an approximately 87-kd chimeric protein that is localized to the cytoplasm, in contrast to NPM-ALK, which typically exhibits a cytoplasmic and nuclear subcellular distribution. ATIC-ALK was constitutively tyrosine phosphorylated and could convert the IL-3-dependent murine hematopoietic cell line BaF3 to cytokine-independent growth. Our studies demonstrate an alternative mechanism for ALK involvement in the genesis of NHL and suggest that ATIC-ALK activation results from ATIC-mediated homodimerization. In addition, expected decreases in ATIC enzymatic function in ATIC-ALK-containing lymphomas may render these tumors more sensitive to antifolate drugs such as methotrexate. (Blood. 2000;95:2144-2149)

Fusion of a novel gene, BTL, to ETV6 in acute myeloid leukemias with a t(4;12)(q11-q12;p13)

The ETV6 gene (also known as TEL) is the main target of chromosomal translocations affecting chromosome band 12p13. The rearrangements fuse ETV6 to a wide variety of partner genes in both myeloid and lymphoid malignancies. We report here 4 new cases of acute myeloid leukemia (AML) with very immature myeloblasts (French-American-British [FAB]-M0) and with a t(4;12)(q11-q12;p13). In all cases, ETV6 was found recombined to a new gene, homologous to the mouse Brx gene. The gene was named BTL (Brx-like Translocated in Leukemia). Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments indicate that the expression of the BTL-ETV6 transcript, but not of the reciprocal ETV6-BTL transcript, is a common finding in these leukemias. In contrast to the majority of other ETV6 fusions, both the complete helix-loop-helix (HLH) and ETS DNA binding domains of ETV6 are present in the predicted BTL-ETV6 fusion protein, and the chimeric gene is transcribed from the BTL promoter.

Genomic organization of human JAK2 and mutation analysis of its JH2-domain in leukemia

The Janus kinase family of proteins, with four mammalian members (JAK1, JAK2, JAK3 and TYK2), plays an essential role in the signal transduction pathway from non-catalytic cytokine receptors to the nucleus. We recently reported the involvement of ETV6-JAK2 fusion genes in the development of leukemia of both lymphoid and myeloid origin. Dominant missense mutations of hopscotch, a Drosophila JAK homologue, causing leukemia-like defects were described. One of these mutations affected a conserved residue of the kinase- like JH2 domain and the introduction of this mutation in murine Jak2 resulted in the constitutional activation of its kinase activity. In order to further analyze its role in leukemogenesis, we cloned human JAK2 and determined its genomic organization. Twenty-four exons spanning a region of approximately 150 kb were identified. A mutation analysis of the exons 13 to 19, encoding the kinase-like JH2 domain failed to detect activating mutations in leukemia samples, suggesting that this is a rare event in human leukemia.

Fusion of TEL, the ETS-variant gene 6 (ETV6), to the receptor-associated kinase JAK2 as a result of t(9;12) in a lymphoid and t(9;15;12) in a myeloid leukemia

Translocations in hematologic disease of myeloid or lymphoid origin with breakpoints at chromosome band 12p13 frequently result in rearrangements of the Ets variant gene 6 (ETV6). As a consequence either the ETS DNA-binding domain or the Helix-Loop-Helix (HLH) oligomerization domain of ETV6 is fused to different partner genes. We show here that a t(9;12)(p24;p13) in a case of early pre-B acute lymphoid leukemia and a t(9;15;12)(p24;q15;p13) in atypical chronic myelogenous leukemia in transformation involve the ETV6 gene at 12p13 and the JAK2 gene at 9p24. In each case different fusion mRNAs were found, with only one resulting in an open reading frame for a chimeric protein consisting of the HLH oligomerization domain of ETV6 and the protein tyrosine kinase (PTK) domain of JAK2. The cloning of the complete human JAK2 coding and genomic sequences and of the genomic junction fragments of the translocations allowed a characterization of the different splice events leading to the various mRNAs. JAK2 plays a central role in non-protein tyrosine kinase receptor signaling pathways, which could explain its involvement in malignancies of different hematologic lineages. Besides hop in Drosophila no member of the JAK family has yet been implicated in tumorigenesis.

Emotional arousal and overeating in restrained eaters

We tested the effects of 3 mood inductions (neutral, positive, and negative) on food intake in 91 women of varying degrees of dietary restraint. Mood induction was accomplished by exposure to 1 of 3 film segments: a travelogue (neutral affect), a comedy film (positive affect), and a horror film (negative affect). In subjects exposed to the neutral film, food intake decreased with increasing levels of dietary restraint. Among subjects who viewed either the comedy film or the horror film, however, food intake increased with increasing restraint. Although the horror film appeared to be more disinhibiting than the comedy film, this effect may have resulted from a difference in the intensity of the emotions induced rather than from their valence. These results suggest that emotional arousal, regardless of valence, may trigger overeating among restrained eaters.

Emotional arousal and overeating in restrained eaters

We tested the effects of 3 mood inductions (neutral, positive, and negative) on food intake in 91 women of varying degrees of dietary restraint. Mood induction was accomplished by exposure to 1 of 3 film segments: a travelogue (neutral affect), a comedy film (positive affect), and a horror film (negative affect). In subjects exposed to the neutral film, food intake decreased with increasing levels of dietary restraint. Among subjects who viewed either the comedy film or the horror film, however, food intake increased with increasing restraint. Although the horror film appeared to be more disinhibiting than the comedy film, this effect may have resulted from a difference in the intensity of the emotions induced rather than from their valence. These results suggest that emotional arousal, regardless of valence, may trigger overeating among restrained eaters.

Problem-solving deficits in suicidal patients: trait vulnerability or state phenomenon?

A diathesis-stress model has been proposed (Schotte & Clum, 1982, 1987), in which deficits in interpersonal problem-solving skills are said to predispose individuals under chronic stress to depression, hopelessness, and suicide ideation. The present study examined the stability of interpersonal problem-solving skills in a short-term, longitudinal study of hospitalized suicide ideators (N = 36). The Ss displayed marked changes in depressive symptoms, state anxiety, hopelessness, and suicide intent over time, and these improvements were associated with improvements in interpersonal problem-solving skills. It is concluded that interpersonal problem-solving deficits may be a concomitant, rather than a cause, of depression, hopelessness, and suicide intent.

Film-induced negative affect triggers overeating in restrained eaters

We tested the effects of film-induced negative affect (i.e., exposure to a frightening film) in 60 women classified as either restrained or unrestrained eaters on the basis of their responses to the Revised Restraint Scale (Herman & Polivy, 1980). Exposure to the frightening film, in contrast to a neutral film, was associated with increases in anxiety, sadness, and anger. High restraint subjects exposed to the frightening film ate more than did equally restrained subjects exposed to a neutral film or low restraint subjects exposed to either film. Thus, negative affect triggered overeating among restrained eaters. Although unrestrained eaters exposed to the frightening film ate less than those who viewed the neutral film, this difference was not statistically significant. These results suggest that negative affect may prompt overeating in persons who attempt to restrict their caloric intake.

Problem-solving deficits in suicidal patients: Trait vulnerability or state phenomenon?

A diathesis-stress model has been proposed (Schotte & Clum, 1982, 1987), in which deficits in interpersonal problem-solving skills are said to predispose individuals under chronic stress to depression, hopelessness, and suicide ideation. The present study examined the stability of interpersonal problem-solving skills in a short-term, longitudinal study of hospitalized suicide ideators (N = 36). The Ss displayed marked changes in depressive symptoms, state anxiety, hopelessness, and suicide intent over time, and these improvements were associated with improvements in interpersonal problem-solving skills. It is concluded that interpersonal problem-solving deficits may be a concomitant, rather than a cause, of depression, hopelessness, and suicide intent.

Film-induced negative affect triggers overeating in restrained eaters

We tested the effects of film-induced negative affect (i.e., exposure to a frightening film) in 60 women classified as either restrained or unrestrained eaters on the basis of their responses to the Revised Restraint Scale (Herman & Polivy, 1980). Exposure to the frightening film, in contrast to a neutral film, was associated with increases in anxiety, sadness, and anger. High restraint subjects exposed to the frightening film ate more than did equally restrained subjects exposed to a neutral film or low restraint subjects exposed to either film. Thus, negative affect triggered overeating among restrained eaters. Although unrestrained eaters exposed to the frightening film ate less than those who viewed the neutral film, this difference was not statistically significant. These results suggest that negative affect may prompt overeating in persons who attempt to restrict their caloric intake.