FIP1L1 PDGFRA Research Articles

Acute exacerbation of idiopathic hypereosinophilic syndrome following asymptomatic coronavirus disease 2019: a case report

BackgroundPrevious research has suggested that some autoimmune diseases develop after the occurrence of coronavirus disease 2019. Hypereosinophilic syndrome is a rare disease presenting with idiopathic eosinophilia and multiple organ involvement, including the skin, lungs, gastrointestinal tract, heart, and nervous system. The diagnosis of idiopathic hypereosinophilic syndrome poses a dilemma because clinical manifestation and serum biomarkers are similar to those of eosinophilic granulomatosis with polyangiitis. Only a few cases have been reported where coronavirus disease 2019 may have caused the new onset or exacerbation of eosinophilic granulomatosis with polyangiitis or idiopathic hypereosinophilic syndrome.Case presentationWe present the case of a 48-year-old Japanese woman with history of asthma who developed deteriorating symptoms of insidiously developed idiopathic hypereosinophilic syndrome following asymptomatic coronavirus disease 2019. She developed acute-onset back pain, tachycardia, abdominal discomfort, loss of appetite, weight loss, skin rash on the back, and numbness of the extremities 3 days after the quarantine period. Extreme hypereosinophilia with multiple abnormal findings including pulmonary ground-glass opacity lesions and mononeuritis multiplex was consistent with hypereosinophilic syndrome. Normal cellularity with eosinophilic proliferation in the bone marrow and negative FIP1L1–PDGFRA raised the diagnosis of idiopathic hypereosinophilic syndrome. Although the patient tested negative for anti-neutrophilic cytoplasmic antibodies and skin biopsy was negative for vasculitis, eosinophilic granulomatosis with polyangiitis could not be excluded. Since glucocorticoids are a standard therapy for both idiopathic hypereosinophilic syndrome and eosinophilic granulomatosis with polyangiitis, we initiated glucocorticoids following a multidisciplinary discussion.ConclusionAlthough the relationship between asymptomatic coronavirus disease 2019 and acute idiopathic hypereosinophilic syndrome exacerbation was uncertain, the chronological order of the symptomatic development suggested a possible link. More clinical cases and population-based studies are needed to determine the potential effect of coronavirus disease 2019 on autoimmune diseases.

Massive eosinophilia despite severe aplastic anemia.

A 47-year-old nonsmoking man developed very severe aplastic anemia (AA) (hemoglobin 56 g/L, neutrophils 110/μl, eosinophils 0/μl, platelets 4000/μl) with fatty marrow (Figure 1A: hematoxylin–eosin stain, ×4 objective). He had a history of bronchial asthma for 3 years and had been treated with inhaled corticosteroid in combination with long-acting β2-agonist (budesonide/formoterol fumarate). In addition, he had developed eosinophilic pneumonia requiring systemic administration of prednisolone (<30 mg/day) twice in the last 1.5 years. His family history was not significant for any serious diseases. Treatment with antithymocyte globulin, eltrombopag olamine, and cyclosporine (CsA) (500 mg/day) eliminated the need for blood transfusions and the CsA dose was gradually reduced. While pancytopenia continued (hemoglobin <97 g/L, neutrophils <1400/μl, platelets <30,000/μl), eosinophilia (>500/μl) appeared 17 months after the start of treatment. This increased to 4550/μl in 4 months after discontinuation of CsA treatment at 33 months. In addition, he presented with a rash with purpura on the legs, for which prednisolone (<20 mg/day) was not effective. Bone marrow examination showed mild hypocellular marrow with eosinophil expansion (43.8%) (Figure 1B: hematoxylin–eosin stain, ×4 objective; Figure 1C: hematoxylin–eosin stain, ×40 objective; Figure 1D: direct Fast Scarlet stain, ×40 objective). Increased blasts and significant dysplasia were not observed. G-banding and fluorescence in situ hybridization for the FIP1L1–PDGFRA re-arrangement detected no chromosomal aberrations. Moreover, skin biopsy revealed eosinophilic vasculitis and panniculitis, compatible with eosinophilic granulomatosis with polyangiitis (Figure 1E: hematoxylin–eosin stain, ×20 objective; Figure 1F: direct Fast Scarlet stain, ×40 objective). After re-administration of CsA (150 mg/day), eosinophilia and skin lesions disappeared in 5 weeks. This case indicates that massive reactive eosinophilia can occur even in AA patients with eosinophil-associated diseases, especially during dose reduction, or after the discontinuation of CsA. None. The authors declare that there is no conflict of interest. Aya Takahashi and Tsutomu Shinohara designed the research, drafted the manuscript, and created the figure. Aya Takahashi performed the skin biopsy. Yoshihito Iwahara, Aya Takahashi, Hisanori Machida, Keishi Naruse, Eiji Takeuchi, and Tsutomu Shinohara analyzed the data. Keishi Naruse contributed to pathological assessment. All authors revised the manuscript critically and approved the final manuscript.

The Actionable Genomic Landscape in Glioblastoma

The standard treatment for glioblastoma involves a combination of surgery, radiation and chemotherapy but have limited impact on survival. The recent exponential increase in targeted agents directed at pivotal oncogenic pathways now provide new therapeutic opportunities for this tumor type. However, lack of precision oncology testing at diagnosis means such therapeutic opportunities are missed. To address this unmet clinical need we established Oncofocus®, a clinically validated precision oncology test for solid tumors, detecting actionable genetic variants in 505 genes linked to 764 anti-cancer targeted agents/combinations and immunotherapies. Analysis of trending data in relation to a cohort of 55 glioblastoma cases has revealed a complex and rich actionable mutational landscape in which 166 actionable mutations were detected across 36 genes. The majority of patients harbored three or more actionable mutations (median 3, range 1-9) affecting key cancer related regulatory networks including the PI3K/AKT/MTOR and RAS/RAF/MEK/MAPK signaling pathways, DNA-damage repair pathways and cell cycle checkpoints. Oncogenic fusion genes were identified at high frequency (23.6%), including two novel fusions in glioblastoma, namely TBL1XR1-PIK3CA and FIP1L1–PDGFRA. Linkage with anti-PD-L1/PD-1 immunotherapy was also identified in 63.6% of glioblastoma patients as a consequence of either elevated PD-L1 levels or mutations in DNA-damage repair genes. Despite the commonly held perception that treatment options for glioblastoma are limited, we have shown here that glioblastoma harbors a diverse actionable mutational landscape providing a broad therapeutic armamentarium of targeted therapies and immunotherapies. Our data indicates that precision oncology testing should be considered as part of the standard molecular diagnostic work up for glioblastoma.

Chromatin Conformation Signatures Associated with Epigenetic Deregulation of the FIP1L1 and PDGFRA Genes

The human genome is organized into topological domains with discrete structural and regulatory units that influence gene expression epigenetically (Crutchley et al., 2010). In glioma patients with IDH1 (R132H) mutations, researchers detected aberrant methylation of transcriptional CTCF-enhancer regions between the FIPL1L1 and PDGFRA genes. Conformational changes to the chromosomal arrangement of these regions have been shown to upregulate PDGFRA expression (Flavahan et al; 2016). Flavahan et al also demonstrated the down regulation of cell growth and proliferation in the glioma cells with the addition of tyrosine kinase inhibitors that target the interaction.We explored this epigenetic interaction and its utility in the stratification of patients for treatment with tyrosine kinase inhibitors. Using a high-resolution chromosome-conformation capture or 3C analysis platform known as EpiSwitchTMand quantitative PCR, we mapped, evaluated, and quantified the conformational juxtaposition between FIP1L1 and PDGFRA in glioma-cell lines with and without IDH mutations. Deregulation of PDGFRA by interstitial deletion at 4q12 and fusion to FIP1L1 associated with chronic esosinophic leukemias prompted our group to also investigate whether the same chromosome-conformation interactions are present in EOL-1 and other leukemic cell lines.EpiSwitchTM templates were produced using a modified process to purify the 3C DNA. Unlike previous protocols, only one set of primers is required. Chromosome conformation capture analysis with a probe, single step PCR and gel purification was used to identify and sequence 3C interactions in the AML cell lines EOL-1 and HL-60. qPCR templates, adjusted to 20 ng of 3C library DNA, were used with concentration-matched negative controls (ie, 3C libraries derived from adipose biopies and normal blood). A 3C interaction with MMP-1 was used as a internal control for the EpiSwitchTM library. A dual label hydrolysis probe was used to detect the sequenced interaction. Five novel interactions were identified between FIP1L1 and PDGFRA by single step PCR and confirmed by sequencing. We quantified one interaction with a dual-labeled hydrolysis probe based qPCR assay to determine copy number in eight cell lines: BT-412 (anaplastic oligoastrocytoma), DBTRG-05MG (glioblastoma multiforme), U-3T3 (glioblastoma astrocytoma), U-87 (glioblastoma astrocytoma), GDM-1 (acute myelomonocytic leukemia), EOL-1 (acute myeloid leukemia, AML), HL-60 (AML) and KG-1 (AML).Using EpiSwitchTM and ISO standard MIQE-compliant qPCR design, five specific epigenetic interactions were detected in three types of cancerous cell lines including EOL-1 and HL-60. qPCR was used to detect one specific difference between normal blood (n = 4) and leukemic cell lines (n = 4). By qPCR the interaction was detected in two AML cell lines known to be highly sensitive to the tyrosine kinase inhibitor Glivec (EOL-1 and GDM-1), as well as HL-60 cells, but not in KG-1. The FIP1L1 PDGFRA 3C interaction was also found in DBTRG-05MG and U-373 at a similar copy number compared to the AML cell lines. A glioma patient biopsy tissue also tested positive for the conformational-chromosome interaction by qPCR compared with an adipose biopsy control. An interaction in the MMP-1 gene was used as an internal positive control in all samples tested.Emerging epigenetic approaches, such as chromosome conformation signatures as detected by EpiSwitchTM, are providing sensitive and accurate methods for improving patient treatment stratification. Detection of interactions between PDGFRA and FIP1L1 based on chromosomal conformational changes have the potential to improve upon the available methods for identifying patients who may benefit from treatment with PDGFRA-targeted tyrosine kinase inhibitors. Further research is needed to validate the method described using blood and biopsy samples in patients with glioma, AML and other myeloproliferative neoplasms associated with the FIP1L1-PDGFRA fusion gene. DisclosuresGrand:Oxford BioDynamics Limited: Employment, Equity Ownership. Bird:Oxford BioDynamics Limited: Employment. Corfield:Oxford BioDynamics Limited: Employment. Dezfouli:Oxford BioDynamics Limited: Employment. Warren:Oxford BioDynamics Limited: Employment. Foulkes:Oxford BioDynamics Limited: Employment. Khudari:Oxford BioDynamics Limited: Employment. Salter:Oxford BioDynamics Limited: Employment. Mahecha:Oxford BioDynamics Limited: Employment. Ssentongo:Oxford BioDynamics Limited: Employment. Green:Oxford BioDynamics Limited: Employment, Equity Ownership. Womersley:Oxford BioDynamics Limited: Employment, Patents & Royalties. Hunter:Oxford BioDynamics Limited: Employment. Ramadass:Oxford BioDynamics Limited: Employment. Akoulitchev:Oxford BioDynamics Limited: Employment, Equity Ownership.

KIT D816V and JAK2 V617F mutations are seen recurrently in hypereosinophilia of unknown significance.

Myeloproliferative neoplasms with eosinophilia are commonly characterized by a normal karyotype and remain poorly defined at the molecular level. We therefore investigated 426 samples from patients with hypereosinophilia of unknown significance initially referred for screening of the FIP1L1-PDGFRA (FP) fusion gene also for KIT D816V and JAK2 V617F mutations. Overall, 86 (20%) patients tested positive: FP+ in 55 (12%), KIT D816V+ in 14 (3%), and JAK2 V617F+ in 17 (4%) patients, respectively. To gain better insight into clinical characteristics, we compared these cases with 31 additional and well-characterized KIT D816V+ eosinophilia-associated systemic mastocytosis (SM-eo) patients enrolled within the "German Registry on Disorders of Eosinophils and Mast cells." Significant differences included younger age, male predominance, and higher eosinophil counts for FP+ cases while abdominal lymphadenopathy, ascites, and serum tryptase levels >100 μg/l were characteristic for those with KIT D816V. Leukocytes, hemoglobin, and splenomegaly did not differ significantly. A median of three additional mutations, most frequently TET2 and SRSF2, were identified in 12/13 KIT D816V+ SM-eo patients with available material indicating a more complex molecular pathogenesis. Median survival was not reached for FP+ cases but was only 26 and 41 months for KIT D816V+ SM and JAK2 V617F+ MPN-eo, respectively. Eosinophilia of ≥2 × 10(9) /l was identified as discriminator for inferior survival in KIT D816V+ and/or JAK2 V617F+ patients (median survival 20 months vs. not reached, P = 0.002). Thus, there is a clear prognostic and therapeutic rationale for detection of KIT D816V and JAK2 V617F in the diagnostic work up of eosinophilia.

PP-056 HYPEREOSINOPHILIC SYNDROME: CASE REPORT

Before the 1990s, lack of evidence for a reactive cause of hypereosinophilia or chronic eosinophilic leukemia (e.g. presence of a clonal cytogenetic abnormality or increased blood or bone marrow blasts) resulted in diagnosticians characterizing such nebulous cases as ‘idiopathic hypereosinophilic syndrome (HES)’. However, over the last decade, significant advances in our understanding of the molecular pathophysiology of eosinophilic disorders have shifted an increasing proportion of cases from this idiopathic HES ‘pool’ to genetically defined eosinophilic diseases with recurrent molecular abnormalities. The majority of these genetic lesions result in constitutively activated fusion tyrosine kinases, the phenotypic consequence of which is an eosinophilia-associated myeloid disorder. Most notable among these is the recent discovery of the cryptic FIP1L1–PDGFRA gene fusion in karyotypically normal patients with systemic mast cell disease with eosinophilia or idiopathic HES, redefining these diseases as clonal eosinophilias. Rearrangements involving PDGFRA and PDGFRB in eosinophilic chronic myeloproliferative disorders, and of fibroblast growth factor receptor 1 (FGFR1) in the 8p11 stem cell myeloproliferative syndrome constitute additional examples of specific genetic alterations linked to clonal eosinophilia. The identification of populations of aberrant T-lymphocytes secreting eosinophilopoietic cytokines such as interleukin-5 establish a pathophysiologic basis for cases of lymphocyte-mediated hypereosinophilia. This recent revival in understanding the biologic basis of eosinophilic disorders has permitted more genetic specificity in the classification of these diseases, and has translated into successful therapeutic approaches with targeted agents such as imatinib mesylate and recombinant anti-IL-5 antibody.

Hypereosinophilic syndrome induced cystitis mimicking bladder tumor

Hypereosinophilic syndrome induced cystitis mimicking bladder tumor

Myeloid neoplasms with eosinophilia and FIP1L1–PDGFRA fusion gene: another point of view

Myeloid neoplasms with eosinophilia and FIP1L1–PDGFRA fusion gene: another point of view

Concomitant FIP1L1–PDGFRA fusion gene and T-cell clonality in a case of chronic eosinophilic leukemia with clonal evolution and an incomplete response to imatinib

Hypereosinophilic syndromes (HES) are rare heterogeneous hematological disorders, characterized by sustained (unexplained) eosinophil overproduction, in which tissue infiltration and mediator relea...

PDGFRA rearrangement leading to hyper-eosinophilia, T-lymphoblastic lymphoma, myeloproliferative neoplasm and precursor B-cell acute lymphoblastic leukemia

The recent World Health Organization (WHO) classification clearly defined a new entity, named ‘myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB and FGFR1’, as a category of three rare specific but related disease groups.1 They are characterized by the formation of a fusion gene encoding an aberrant tyrosine kinase and almost always associated with peripheral blood eosinophilia.1 Myeloid and lymphoid neoplasms with PDGFRA rearrangement are unique disease entities mostly characterized by the formation of a fusion gene FIP1L1–PDGFRA, as a result of a cryptic deletion at chromosome 4q12.1, 2 The disease presents generally as chronic eosinophilic leukemia but can also present as acute myeloid leukemia, T-lymphoblastic lymphoma or both simultaneously. Although the hematopoietic stem cell has been postulated as a possible cellular origin of the disease, clinical manifestations are apparently limited only to the myeloid and T-cell lineages both in chronic phase and in acute leukemic transformation.1, 2 In this study we present an extremely rare case, in which a single genetic abnormality (PDGFRA rearrangement) led to multiple morphologically and immunophenotypically distinct diseases, including T-lymphoblastic lymphoma, a myeloproliferative neoplasm with eosinophilia and abnormal mastocytosis, and a precursor B-cell acute lymphoblastic leukemia, thus involving all three major hematopoietic lineages, that is, myeloid, T-cell and B-cell in the same patient, truly representing a ‘pluripotent hematopoietic stem cell disorder.’

KIT D816V and JAK2 V617F Point Mutations Are Recurrently Found In Suspected Hypereosinophilic Syndrome

AbstractAbstract 4100In some patients with suspected hypereosinophilic syndrome (HES), clonality of eosinophils may be proven by identification of an acquired chromosome or molecular abnormality leading to the diagnosis of chronic eosinophilic leukemia (CEL). The most common molecular aberrations are fusion genes with involvement of PDGFRA, e.g. FIP1L1-PDGFRA (FP), or PDGFRB, e.g. ETV6-PDGFRB. Molecular testing for FP by RT-PCR or FISH is nowadays performed early in the diagnostic work-up of suspected non-reactive eosinophilia. However, eosinophilia is also present at variable frequency in patients with systemic mastocytosis (SM) and other subtypes of myeloproliferative neoplasms (MPN). Recurrent molecular markers for those entities are KIT D816V (80-90% positivity in SM) and JAK2 V617F (60-70% positivity in MPN). We therefore sought to evaluate the relative frequency of FP (by RT-PCR), KIT D816V (by D-HPLC plus direct sequencing) and JAK2 V617F (by ARMS-PCR) in 300 samples from patients with suspected HES/CEL and to correlate molecular findings with clinical features. Molecular abnormalities were identified in 42 (14%) cases; 22 (7.3%) were positive for FP, 14 (4.6%) for KIT D816V and 6 (2.0%) for JAK2 V617F, respectively. Most baseline clinical characteristics, e.g. leukocytes, absolute and relative number of eosinophils, hemoglobin, platelets or splenomegaly, were not different between the three entities.Significant differences were found regarding age, gender, serum tryptase levels and course of disease. FP positive patients were significantly younger (p<0.001) and exclusively male while a female prepoderance was observed for KIT and JAK2 mutated patients. Significantly elevated serum tryptase levels (normal value <11.4μ g/l) were found in all cases of FP and KIT D816V positive patients. However, serum tryptase levels >50μ g/l were almost exclusively seen in KIT D816V positive SM patients. Aggressive SM (ASM) was diagnosed in 6 of 14 (43%) KIT D816V positive patients due to characteristic bone marrow morphology and the presence of diverse C-findings (e.g. anemia <10g/dl, n=2, and/or thrombocytopenia <100×109/μ l, n=7). Frequent additional clinical features included lymphadenopathy (n=9) and urticaria pigmentosa (n=6). Two ASM patients died within first year of diagnosis while 21 (95%) FP positive CEL patients are in complete molecular remission on imatinib after a median treatment time of 28 months (range 8–149). We conclude that the serum tryptase level is an important diagnostic and prognostic marker in eosinophilia. We suggest that FP negative HES patients should be screened for KIT D816V and JAK2 V617F point mutations, both of which are potentially targetable by small molecule inhibitors.FIP1L1-PDGFRAKIT D816VJAK2 V617FNumber of patients22 (7.3%)14 (4.6%)6 (2.0%)Age (median, years)4418–736342–817269–87Gender (m/f)22/06/84/6Leukocytes (median, range, ×109/l)13.57.2–85.610.06.8–124.026.812.7–61.1Eosinophil (median, range, ×109/l)6.51.4–34.82.21.2–100.010.03.2–16.5Eosinophils (%)469–74246–81378–61Hemoglobin (median, range, g/dl)12.67.1–15.811.77.9–15.713.511.4–16.2Platelets (median, range, ×109/l)16034–37511215–94517434–364Splenomegaly14/14 (100%)13/13 (100%)4/4 (100%)Serum tryptase >50μ g/l1/13 (8%)8/9 (88%)not done>100μ g/l0/13 (-)7/7 (100%)not done Disclosures:Erben:Novartis: Honoraria, Research Funding.

The low frequency of clinical resistance to PDGFR inhibitors in myeloid neoplasms with abnormalities of PDGFRA might be related to the limited repertoire of possible PDGFRA kinase domain mutations in vitro

Myeloproliferation with prominent eosinophilia is associated with rearrangements of PDGFR-A or -B. The most common rearrangement is FIP1L1-PDGFRA (FP). The majority of patients with PDGFR-rearranged myeloproliferation respond to treatment with imatinib. In contrast to BCR-ABL-positive chronic myelogenous leukemia, only few cases of imatinib resistance and mutations of the FP kinase domain have been described so far. We hypothesized that the number of critical residues mediating imatinib resistance in FP in contrast to BCR-ABL might be limited. We performed an established systematic and comprehensive in vitro resistance screen to determine the pattern and frequency of possible TKI resistance mutations in FP. We identified 27 different FP kinase domain mutations including 25 novel variants, which attenuated response to imatinib, nilotinib or sorafenib. However, the majority of these exchanges did not confer complete inhibitor resistance. At clinically achievable drug concentrations, FP/T674I predominated with imatinib, whereas with nilotinib and sorafenib, FP/D842V and the compound mutation T674I+T874I became prevalent. Our results suggest that the PDGFR kinase domain contains a limited number of residues where exchanges critically interfere with binding of and inhibition by available PDGFR kinase inhibitors at achievable concentrations, which might explain the low frequency of imatinib resistance in this patient population. In addition, these findings would help to select the appropriate second-line drug in cases of imatinib-resistant disease and may be translated to other neoplasms driven by activated forms of PDGFR-A or -B.

Myeloid neoplasm with prominent eosinophilia and PDGFRA rearrangement treated with imatinib mesylate

The FIP1L1-PDGFRA fusion gene is the most frequent genetic aberration in myeloid neoplasms associated with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1. Affected patients in adult populations are very sensitive to imatinib therapy. Pediatric cases are rare and so far only one case of FIP1L1-PDGFRA positive disease has been reported. We report a 2-year-old female with a myeloid neoplasm associated with eosinophilia and rearrangement of PDGFRA. Treatment with imatinib resulted in complete and durable clinical, hematological, and molecular remission within 3 months after starting treatment.

Successful treatment of cardiac manifestation of eosinophilic leukemia

A 37-year-old male patient presented to the stroke unit of our neurology department with weakness and paresthesia of the right arm and slight anomia. Physical examination revealed distal palsy of both arms, predominantly on the right side. No other pathologic findings were observed. Cranial MRI revealed bilateral territorial infarction in the supply territories of the middle and posterior cerebral arteries. A 12-lead electrocardiography showed incomplete right bundle branch block, negative T waves and ST depression in II, III, aVF and V4–V6 (Fig. 1a). Transesophageal and transthoracic echocardiography revealed normal dimensions of both ventricles with regular systolic and diastolic function. No intracardiac thrombi and no patent foramen ovale could be detected at that time. HolterECG did not show paroxysmal atrial fibrillation. Carotid artery stenosis was ruled out by duplex ultrasound. Blood examination showed increased creatinine (1.59 mg/dL) and urea (60 mg/dL). The white cell count was 13.2 9 10/L, with 6.9 9 10/L eosinophils (52%). A screening for vasculitis was unremarkable aside from an ANA titer of 1:320. Stool analysis and serologic tests were unsuspicious for parasitic helminth infection and there was no apparent primary allergic disorder. Because of the drastically increased eosinophils, we suspected a myeloproliferative disorder. A bone marrow biopsy was done, showing increased myelopoiesis and megakaryopoiesis as well as massive eosinophilia. These findings led us to the diagnosis of hypereosinophilic syndrome (HES). The firstline therapy for HES is steroids [3]; so, we started treatment with prednisone. Antiplatelet therapy with aspirin was administered because of the stroke. As it may have influence on the treatment, it is necessary to further classify the disease by cytogenetic and molecular genetic analysis. During these diagnostic procedures, a chromosomal deletion on 4q12 leading to creation of the FIP1L1–PDGFRA fusion gene was detected. This gene encodes a protein displaying constitutive tyrosine kinase activity. Thus, the final diagnosis was F/P ? chronic eosinophilic leukemia (CEL) [7] and the tyrosine kinase inhibitor imatinib, which is regarded as first line therapy for this special disease subgroup [3, 7], was administered at a dose of 100 mg/day. A control echocardiography was performed 2 months later, revealing an elastic echogenic mass filling the left ventricular apex (Fig. 1b; Movie 1) and right ventricular involvement. These findings could be confirmed in further follow-up studies. Cardiac magnetic resonance (CMR) also confirmed the presence of thrombotic formations in the left and right ventricular apex (Fig. 1d). Strikingly, leukocyte count was normalized to 9.1 9 10/L with 0.5% eosinophils at this point of time. No FIP1L1–PDGFRA transcripts were detectable, so a complete molecular genetic remission was achieved. The patient remained clinically stable without symptoms. Echocardiography follow-up was continued and after 1 year of therapy with imatinib, a clear regression of cardiac involvement could be assessed, since the left and right ventricular echogenic masses could not be detected any longer (Fig. 1c; Movie 2). Chronic eosinophilic leukemia is part of the heterogenous group of HESs. As these are very rare, there are no published Electronic supplementary material The online version of this article (doi:10.1007/s00392-010-0143-9) contains supplementary material, which is available to authorized users.

Sorafenib and Nilotinib Are Candidates to Overcome Imatinib Resistance in Myeloproliferation with FIP1L1-PDGFRA.

Abstract 2912Poster Board II-888Constitutively activated variants of PDGFRA, PDGFRB can be found in a subset of patients with myeloid neoplasms associated with eosinophilia. The most common is FIP1L1-PDGFRA (FP). Patients with PDGFR-A and -B rearranged myeloproliferation respond to treatment with imatinib. However, single cases of clinical resistance due to a secondary FP/T674I mutation have been reported. In CML, more than 40 different exchanges have been described that confer imatinib resistance, and sequential treatment with imatinib and novel Abl kinase inhibitors has become reality. Nilotinib and sorafinib are potent alternative inhibitors of PDGFR-A and -B. We therefore hypothesized that available PDGFR kinase inhibitors might produce specific profiles of secondary FP kinase domain mutations mediating inhibitor resistance. To this aim, we selected clones of FP expressing Ba/F3 cells resistant to rising concentrations of imatinib, nilotinib, and sorafinib. In these, we identified 27 different PDGFRA kinase domain mutations. Imatinib, nilotinib and sorafenib produced distinct profiles of resistance mutations. During selection with imatinib, FP/T674I predominated with rising concentrations. FP/T674I corresponds to Bcr-Abl/T315I, which is frequently found in imatinib resistant CML. In contrast to imatinib, nilotinib and sorafenib produced a significantly lower frequency of resistant cell clones. Also, T674I disappeared at therapeutic nilotinib concentrations in favour of T674I+T874I and D842V. Sorafinib displayed a distinct profile of mutations including D842V, but not T674I. Following cloning and expression of all FP variants, dose-response analysis indicated that full cross-resistance to all three inhibitors was limited to D842V, whereas the gatekeeper T674I exchange retained sensitivity to sorafenib and nilotinib, and T674I+T874I was responsive to sorafenib only. In silico structure modelling indicated that differences in inhibitor response observed in distinct clusters of FP mutations identified in drug-resistant clones are based on differences of sorafenib versus imatinib and nilotinib in key drug - protein target interactions in PDGFR family kinases. Besides direct inhibitor binding effects, we propose that the identified exchanges shift an inactive-active conformation equilibrium and thereby affect binding of type II inhibitors like imatinib, nilotinib and sorafenib. Our results predict PDGFR variants that might come up in patients with myeloproliferation positive for PDGFR-A or -B fusions treated with imatinib, nilotinib or sorafenib. These findings will help in selection of an appropriate second line PDGFR kinase inhibitor when resistance to imatinib emerges, and will guide drug design. Moreover, our data can be translated to other neoplasms driven by activated forms of PDGFR-A or -B including GIST, CMML, and dermatofibrosarcoma protuberans. Disclosures:Off Label Use: Use of sorafenib and nilotinib in myeloproliferation with prominent eosinophilia.

Five years since the discovery of FIP1L1–PDGFRA: what we have learned about the fusion and other molecularly defined eosinophilias

The year 2008 marks the fifth anniversary since the publication which identified the FIP1L1-PDGFRA fusion gene in patients with idiopathic hypereosinophilia. With the benefit of time, a more comprehensive picture has emerged regarding several characteristics of the fusion, including its incidence, biological features and the clinical profile of patients who carry the molecular rearrangement. A few prospective trials have now better defined the natural history of imatinib-treated FIP1L1-PDGFRA-positive patients, from which some basic conclusions can be drawn: the prognosis is outstanding, acquired resistance is exceedingly rare, but ongoing imatinib treatment is likely required to prevent relapse. The emergence of genetically assigned eosinophilias has led the World Health Organization in 2008 to adopt a semi-molecular classification scheme, with one subcategory named 'myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1.' Molecular rearrangements involving other partner genes, such as ETV6 and JAK2, have also been associated with eosinophilic disorders, and will likely be assimilated into such classifications over time. Despite the molecularly defined eosinophilias comprising a small proportion of cases compared to the aggregate of other subtypes of hypereosinophilia, their recognition is critical because of the availability of highly effective molecularly targeted therapy.

FIP1L1–PDGFRA positive chronic eosinophilic leukaemia and associated central nervous system involvement

Interstitial deletion involving chromosome 4q12 generates the novel tyrosine kinase fusion protein encoded by FIP1L1–PDGFRA, which is present in many patients previously labelled as having hypereosinophilic syndrome, initially reported in...

Redefinition of Hypereosinophilic Disorders Based on an Analysis of 28 Cases of FIP1 L1-PDGFRA Negative Persistent Unexplained Eosinophilia (PUE) with Eosinophil End-Organ Damage (EEOD).

In 1997 the term eosinophil end-organ damage(EEOD) was introduced to facilitate management of patients with high eosinophil counts in whom damage to organs such as heart, lungs, and skin by eosinophils was associated with persistent unexplained eosinophilia (no obvious cause for eosinophilia was identified). In 2003 Cools et al identified the presence of the FIP1L1-PDGFRA gene as the causation of eosinophilia in 50% of cases of hypereosinophilic syndromes with end organ damage. Cases which are negative for this gene and a Tcell clone appear to form a distinctive group whose aetiopathogenesis and clinical significance are different. In order to identify the extent of end organ damage in FIP1L1-PDGFRA negative cases and/or identify rarer causes of unexplained eosinophilia in all cases of eosinophilia presenting from 14.06.2002 to 14.06.2006, we looked at all patients who had persistent eosinophilia present on two separate blood tests done I month apart with eosinophil counts greater than 1–1.5 x 10 9/l. All cases of unexplained eosinophilia (Eosinophil count greater than 1– 1.5 x 10 9/L) seen at our institution in a 4 year period in whom no obvious cause of eosinophilia was found were evaluated for the presence of the FIP1L1-PDGFRA gene, TEL-PDGFRB and variant BCR-ABL gene. Of 40 cases seen 2 men were FIP1L1-PDGFRA positive, 3 others (2 men and 1 woman) had myeloproliferative diseases, I man had clozapine induced eosinophilia, one woman Kimura Weils disease and 1 man had cutaneous mastocytosis . There were 28 cases (14 women, 2 children,12 men) who were FIP1L1 -PDGFRA negative and had persistent unexplained eosinophilia without clonal T cells. These cases were followed up over a 4 year period and tested serially for damage to end organs by eosinophils. FIP1L1-PDGFRA was tested and found negative on two separate occasions. Ig E levels had to be less then 500 iu/l to exclude allergy and a therapeutic trial of mebendazole 100mg daily for three days was given in all cases even if parasite testing did not identify a parasitic infestation. There were 28 cases (14 women, 2 children,12 men) who were FIP1L1-PDGFRA negative which contrasts with the Male Female ratio seen in FIP1 L1-PDGFRA positive cases in which males predominate. The age ranged from 9–80. Four year follow up identified a chronic illness in these cases with no damage to vital organs. Clinical symptoms complained of included fatigue(28), joint and muscle pains(28), skin rashes(10), blackouts(1), thrombotic events(2), diarrhoea(2), fasciitis(2), gastroenteritis(2), cough(2), and breathlessness(2). No organomegaly was seen. In one clonal T cells were identified on serial testing after 1 year of follow up. We conclude that cases of FIP1L1-PDGFRA negative hypereosinophilia are a distinct group with a chronic illness mainly affecting skin and joints who respond well to symptomatic treatment, oral steroids, or hydroxyurea. We believe that hypereosinophilic diorders need to be redined as PUEand EEOD. When both PUE and EEOD are present the diagnosis is HES.

Chronic eosinophilic leukaemia with FIP1L1–PDGFRA fusion and T674I mutation that evolved from Langerhans cell histiocytosis with eosinophilia after chemotherapy

Chronic eosinophilic leukaemia with <i>FIP1L1–PDGFRA</i> fusion and T674I mutation that evolved from Langerhans cell histiocytosis with eosinophilia after chemotherapy

Relationship between idiopathic hypereosinophilic syndrome, eosinophilic leukemia, and systemic mastocytosis.

Chronic eosinophilic leukemia is a neoplastic condition with persistent eosinophilia as the major hematological abnormality and with the eosinophils being part of the neoplastic clone. Some cases can be recognized by traditional hematological criteria, but many can be recognized only when a clonal cytogenetic or molecular genetic abnormality is demonstrated. A range of cytogenetic and molecular genetic abnormalities has been recognized, including both those seen in other myeloid malignancies (such as trisomy 8, monosomy 7, and 20q-) and those that are particularly linked to eosinophil differentiation (such as rearrangements of PDGFRB, FGFR1, and PDGFRA, the latter with formation of a FIP1L1-PDGFRA fusion gene). The discovery of the FIP1L1-PDGFRA fusion gene has led to the recognition that many patients who would previously have been regarded as having idiopathic hypereosinophilia actually have chronic eosinophilic leukemia. The same fusion gene has also been found in patients with hypereosinophilia and atypical bone marrow mast cells but whether this syndrome should be regarded as a variant of eosinophilic leukemia or as a variant of systemic mastocytosis remains to be established.