Ponatinib suppresses the development of myeloid and lymphoid malignancies associated with FGFR1 abnormalities

Single-cell analysis defines highly specific leukemia-induced neutrophils and links MMP8 expression to recruitment of tumor associated neutrophils during FGFR1 driven leukemogenesis

BACKGROUND

Leukemias driven by activated, chimeric FGFR1 kinases typically progress to AML which have poor prognosis. Mouse models of this syndrome allow detailed analysis of cellular and molecular changes occurring during leukemogenesis. We have used these models to determine the effects of leukemia development on the immune cell composition in the leukemia microenvironment during leukemia development and progression.

METHODS

Single cell RNA sequencing (scRNA-Seq) was used to characterize leukemia associated neutrophils and define gene expression changes in these cells during leukemia progression.

RESULTS

scRNA-Seq revealed six distinct subgroups of neutrophils based on their specific differential gene expression. In response to leukemia development, there is a dramatic increase in only two of the neutrophil subgroups. These two subgroups show specific gene expression signatures consistent with neutrophil precursors which give rise to immature polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). Analysis of gene expression in these precursor cells identified pathways that were specifically upregulated, the most pronounced of which involved matrix metalloproteinases Mmp8 and Mmp9, during leukemia progression. Pharmacological inhibition of MMPs using Ilomastat preferentially restricted in vitro migration of neutrophils from leukemic mice and led to a significantly improved survival in vivo, accompanied by impaired PMN-MDSC recruitment. As a result, levels of T-cells were proportionally increased. In clinically annotated TCGA databases, MMP8 was shown to act as an independent indicator for poor prognosis and correlated with higher neutrophil infiltration and poor pan-cancer prognosis.

CONCLUSION

We have defined specific leukemia responsive neutrophil subgroups based on their unique gene expression profile, which appear to be the precursors of neutrophils specifically associated with leukemia progression. An important event during development of these neutrophils is upregulation MMP genes which facilitated mobilization of these precursors from the BM in response to cancer progression, suggesting a possible therapeutic approach to suppress the development of immune tolerance.

World Health Organization and International Consensus Classification of eosinophilic disorders: 2024 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of non-hematologic (secondary or reactive) and hematologic (primary or clonal) disorders with the potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 109/L, and may be associated with tissue damage. After the exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of various tests. They include morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, molecular testing and flow immunophenotyping to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2022 World Health Organization and International Consensus Classification endorse a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions" (MLN-eo-TK), and the MPN subtype, "chronic eosinophilic leukemia" (CEL). Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (e.g., <1.5 × 109/L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Pemigatinib was recently approved for patients with relapsed or refractory FGFR1-rearranged neoplasms. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, is approved by the U.S Food and Drug Administration for patients with idiopathic HES. Cytotoxic chemotherapy agents, and hematopoietic stem cell transplantation have been used for aggressive forms of HES and CEL, with outcomes reported for limited numbers of patients. Targeted therapies such as the IL-5 receptor antibody benralizumab, IL-5 monoclonal antibody depemokimab, and various tyrosine kinase inhibitors for MLN-eo-TK, are under active investigation.

Hematological Neoplasms with Eosinophilia

Eosinophils in peripheral blood account for 0.3-5% of leukocytes, which is equivalent to 0.05-0.5 × 109/L. A count above 0.5 × 109/L is considered to indicate eosinophilia, while a count equal to or above 1.5 × 109/L is defined as hypereosinophilia. In bone marrow aspirate, eosinophilia is considered when eosinophils make up more than 6% of the total nuclear cells. In daily clinical practice, the most common causes of reactive eosinophilia are non-hematologic, whether they are non-neoplastic (allergic diseases, drugs, infections, or immunological diseases) or neoplastic (solid tumors). Eosinophilia that is associated with a hematological malignancy may be reactive or secondary to the production of eosinophilopoietic cytokines, and this is mainly seen in lymphoid neoplasms (Hodgkin lymphoma, mature T-cell neoplasms, lymphocytic variant of hypereosinophilic syndrome, and B-acute lymphoblastic leukemia/lymphoma). Eosinophilia that is associated with a hematological malignancy may also be neoplastic or primary, derived from the malignant clone, usually in myeloid neoplasms or with its origin in stem cells (myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions, acute myeloid leukemia with core binding factor translocations, mastocytosis, myeloproliferative neoplasms, myelodysplastic/myeloproliferative neoplasms, and myelodysplastic neoplasms). There are no concrete data in standardized cytological and cytometric procedures that could predict whether eosinophilia is reactive or clonal. The verification is usually indirect, based on the categorization of the accompanying hematologic malignancy. This review focuses on the broad differential diagnosis of hematological malignancies with eosinophilia.

Pemigatinib for the treatment of myeloid/lymphoid neoplasms with FGFR1 rearrangement

INTRODUCTION

Myeloid/lymphoid neoplasms with fibroblast growth factor receptor-1 (FGFR1) rearrangements (MLN^FGFR1) are rare entities with aggressive features and poor prognosis. Presentation is heterogeneous, ranging from myeloproliferative neoplasms (with or without eosinophilia) to T-cell lymphoma and acute leukemia. Historical treatments have been guided by the presenting phenotype with induction chemotherapy frequently used. Pemigatinib is a FGFR1-3 tyrosine kinase inhibitor that has demonstrated high complete hematologic and cytogenetic response rates in MLN^FGFR1.

AREAS COVERED

We discuss the pathogenesis, presentation, and historical treatments for MLN^FGFR1, in addition to clinical data using pemigatinib and other targeted therapies. Discussion of the mechanism of action and adverse events are also included.

EXPERT OPINION

Pemigatinib represents a significant advance in the management of MLN^FGFR1. High rates of complete hematologic and cytogenetic response have been observed. While direct comparative data are unavailable, outcomes appear favorable compared to conventional approaches. Long term efficacy and tolerability are not yet known, and allogeneic hematopoietic stem cell transplant (alloHSCT) has been and continues to be the treatment with the highest chance of long term disease free survival in responding patients. Combinations of pemigatinib and chemotherapy, particularly for more aggressive phenotypes, warrant future investigation as does the use of pemigatinib maintenance following alloHSCT.

Biologic therapies for hypereosinophilic disorders: From tyrosine kinase inhibitors to monoclonal antibodies. Towards an increasingly customized management?

Hypereosinophilic syndromes (HES) encompass a wide range of disorders characterized by persistent peripheral blood hypereosinophilia (HE) (i.e., an eosinophil count ≥1.5 × 10⁹/L and ≥ 10% eosinophils preferably with a minimal duration of 6 months if documentation is available) associated with organ damage and/or dysfunction attributable to tissue eosinophilic infiltrate and release of granule contents. In most cases, HE is associated with atopic conditions/allergies, parasitic infections, medications, autoimmune disorders and/or solid tumors in most cases. More rarely, it can be one of the dominant manifestations of an underlying myeloid/lymphoid neoplasm. With regard to hematological forms, in recent decades the advances in understanding the pathogenic aspects of HES have led to a growing interest in these diseases, and in the 2016 WHO classification multiple subgroups were defined according to the molecular profile with the aim of better characterizing these syndromes and establishing which patients will benefit from specific pharmacological targeted therapies. This review article will provide a comprehensive overview of possible therapeutic approaches for HES in the light of each specific molecular alteration, considering both tyrosine kinase inhibitors and monoclonal antibodies, either implemented in clinical practice or currently still under development.

Ponatinib Drives Cardiotoxicity by S100A8/A9-NLRP3-IL-1β Mediated Inflammation

BACKGROUND

The tyrosine kinase inhibitor ponatinib is the only treatment option for chronic myelogenous leukemia patients with T315I (gatekeeper) mutation. Pharmacovigilance analysis of Food and Drug Administration and World Health Organization datasets has revealed that ponatinib is the most cardiotoxic agent among all Food and Drug Administration-approved tyrosine kinase inhibitors in a real-world scenario. However, the mechanism of ponatinib-induced cardiotoxicity is unknown.

METHODS

The lack of well-optimized mouse models has hampered the in vivo cardio-oncology studies. Here, we show that cardiovascular comorbidity mouse models evidence a robust cardiac pathological phenotype upon ponatinib treatment. A combination of multiple in vitro and in vivo models was employed to delineate the underlying molecular mechanisms.

RESULTS

An unbiased RNA sequencing analysis identified the enrichment of dysregulated inflammatory genes, including a multifold upregulation of alarmins S100A8/A9, as a top hit in ponatinib-treated hearts. Mechanistically, we demonstrate that ponatinib activates the S100A8/A9-TLR4 (Toll-like receptor 4)-NLRP3 (NLR family pyrin domain-containing 3)-IL (interleukin)-1β signaling pathway in cardiac and systemic myeloid cells, in vitro and in vivo, thereby leading to excessive myocardial and systemic inflammation. Excessive inflammation was central to the cardiac pathology because interventions with broad-spectrum immunosuppressive glucocorticoid dexamethasone or specific inhibitors of NLRP3 (CY-09) or S100A9 (paquinimod) nearly abolished the ponatinib-induced cardiac dysfunction.

CONCLUSIONS

Taken together, these findings uncover a novel mechanism of ponatinib-induced cardiac inflammation leading to cardiac dysfunction. From a translational perspective, our results provide critical preclinical data and rationale for a clinical investigation into immunosuppressive interventions for managing ponatinib-induced cardiotoxicity.

Massive Loss of Transcription Factors Promotes the Initial Diversification of Placental Mammals

As one of the most successful group of organisms, mammals occupy a variety of niches on Earth as a result of macroevolution. Transcription factors (TFs), the fundamental regulators of gene expression, may also have evolved. To examine the relationship between TFs and mammalian macroevolution, we analyzed 140,821 de novo-identified TFs and their birth and death histories from 96 mammalian species. Gene tree vs. species tree reconciliation revealed that placental mammals experienced an upsurge in TF losses around 100 million years ago (Mya) and also near the Cretaceous–Paleogene boundary (K–Pg boundary, 66 Mya). Early Euarchontoglires, Laurasiatheria and marsupials appeared between 100 and 95 Mya and underwent initial diversification. The K-Pg boundary was associated with the massive extinction of dinosaurs, which lead to adaptive radiation of mammals. Surprisingly, TF loss decelerated, rather than accelerated, molecular evolutionary rates of their target genes. As the rate of molecular evolution is affected by the mutation rate, the proportion of neutral mutations and the population size, the decrease in molecular evolution may reflect increased functional constraints to survive target genes.

A truncated derivative of FGFR1 kinase cooperates with FLT3 and KIT to transform hematopoietic stem cells in syndromic and de novo AML

Background

Myeloid and lymphoid malignancies associated with chimeric FGFR1 kinases are the hallmark of stem cell leukemia and lymphoma syndrome (SCLL). In all cases, FGFR1 kinase is constitutively phosphoactivated as a result of chromosome translocations, which lead to acquisition of dimerization motifs in the chimeric proteins. Recently, we demonstrated that these chimeric kinases could be cleaved by granzyme B to generate a truncated derivative, tnFGFR1, which localized exclusively into the nucleus and was not phosphorylated.

Methods

Stem cell transduction and transplantation in syngeneic mice was used to assess the transforming ability of tnFGFR1 in bone marrow stem cells, and RPPA and RNA-Seq was used to examine the related signaling pathways and regulated target genes.

Results

For the first time, we show that this non-classical truncated form of FGFR1 can independently lead to oncogenic transformation of hematopoietic stem cells in an animal model in vivo. These leukemia cells show a mixed immunophenotype with a B-cell B220 + Igm- profile in the majority of cells and Kit+ in virtually all cells, suggesting a stem cell disease. tnFGFR1, however, does not activate classic FGFR1 downstream signaling pathways but induces a distinct profile of altered gene expression with significant upregulation of transmembrane signaling receptors including FLT3 and KIT. We further show that de novo human AML also express tnFGFR1 which correlates with upregulation of FLT3 and KIT as in mouse leukemia cells. ChIP analysis demonstrates tnFGFR1 occupancy at the Flt3 and Kit promoters, suggesting a direct transcriptional regulation. Cells transformed with tnFGFR1 are insensitive to FGFR1 inhibitors but treatment of these cells with the Quizartinib (AC220) FLT3 inhibitor, suppresses in vitro growth and development of leukemia in vivo. Combined treatment with FGFR1 and FLT3 inhibitors provides increased survival compared to FGFR1 inhibition alone.

Conclusions

This study demonstrates a novel model for transformation of hematopoietic stem cells by chimeric FGFR1 kinases with the combined effects of direct protein activation by the full-length kinases and transcriptional regulation by the truncated nuclear tnFGFR1 derivative, which is associated with GZMB expression levels. Genes significantly upregulated by tnFGFR1 include Flt3 and Kit which promote a leukemia stem cell phenotype. In human AML, tnFGFR1 activation leads to increased FLT3 and KIT expression, and higher FLT3 and GZMB expression levels are associated with an inferior prognosis. These observations provide insights into the relative therapeutic value of targeting FGFR1 and FLT3 in treating AML with this characteristic gene expression profile.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01628-3.

Identification of a novel HOOK3-FGFR1 fusion gene involved in activation of the NF-kappaB pathway

Background

Rearrangements involving the fibroblast growth factor receptor 1 (FGFR1) gene result in 8p11 myeloproliferative syndrome (EMS), which is a rare and aggressive hematological malignancy that is often initially diagnosed as myelodysplastic syndrome (MDS). Clinical outcomes are typically poor due to relative resistance to tyrosine kinase inhibitors (TKIs) and rapid transformation to acute leukemia. Deciphering the transcriptomic signature of FGFR1 fusions may open new treatment strategies for FGFR1 rearrangement patients.

Methods

DNA sequencing (DNA-seq) was performed for 20 MDS patients and whole exome sequencing (WES) was performed for one HOOK3-FGFR1 fusion positive patient. RNA sequencing (RNA-seq) was performed for 20 MDS patients and 8 healthy donors. Fusion genes were detected using the STAR-Fusion tool. Fluorescence in situ hybridization (FISH), quantitative real-time PCR (qRT-PCR), and Sanger sequencing were used to confirm the HOOK3-FGFR1 fusion gene. The phosphorylation antibody array was performed to validate the activation of nuclear factor-kappaB (NF-kappaB) signaling.

Results

We identified frequently recurrent mutations of ASXL1 and U2AF1 in the MDS cohort, which is consistent with previous reports. We also identified a novel in-frame HOOK3-FGFR1 fusion gene in one MDS case with abnormal monoclonal B-cell lymphocytosis and ring chromosome 8. FISH analysis detected the FGFR1 break-apart signal in myeloid blasts only. qRT-PCR and Sanger sequencing confirmed the HOOK3-FGFR1 fusion transcript with breakpoints located at the 11th exon of HOOK3 and 10th exon of FGFR1, and Western blot detected the chimeric HOOK3-FGFR1 fusion protein that is presumed to retain the entire tyrosine kinase domain of FGFR1. The transcriptional feature of HOOK3-FGFR1 fusion was characterized by the significant enrichment of the NF-kappaB pathway by comparing the expression profiling of FGFR1 fusion positive MDS with 8 healthy donors and FGFR1 fusion negative MDS patients. Further validation by phosphorylation antibody array also showed NF-kappaB activation, as evidenced by increased phosphorylation of p65 (Ser 536) and of IKBalpha (Ser 32).

Conclusions

The HOOK3-FGFR1 fusion gene may contribute to the pathogenesis of MDS and activate the NF-kappaB pathway. These findings highlight a potential novel approach for combination therapy for FGFR1 rearrangement patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02451-y.

World Health Organization-defined eosinophilic disorders: 2022 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of nonhematologic (secondary or reactive) and hematologic (primary or clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 10⁹ /L. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next generation sequencing gene assays, and flow immunophenotyping to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the myeloproliferative neoplasm subtype, "chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (eg, < 1.5 × 10⁹ /L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, was recently approved by the US Food and Drug Administration for patients with idiopathic HES. The use of the IL-5 receptor antibody benralizumab, as well as other targeted therapies such as JAK2 and FGFR1 inhibitors, is under active investigation.

IRAK1-regulated IFN-γ signaling induces MDSC to facilitate immune evasion in FGFR1-driven hematological malignancies

BACKGROUND

Stem Cell leukemia/lymphoma syndrome (SCLL) presents as a myeloproliferative disease which can progress to acute myeloid leukemia and is associated with the coincident development of B-cell and T-cell lymphomas. SCLL is driven by the constitutive activation of fibroblast growth factor receptor-1 (FGFR1) as a result of chromosome translocations with poor outcome. Mouse models have been developed which faithfully recapitulate the human disease and have been used to characterize the molecular genetic events that are associated with development and progression of the disease.

METHODS

CRISPR/Cas9 approaches were used to generate SCLL cells null for Interleukin receptor associated kinase 1 (IRAK1) and interferon gamma (IFNG) which were introduced into syngeneic hosts through tail vein injection. Development of the disease and changes in immune cell composition and activity were monitored using flow cytometry. Bead-based immunoassays were used to compare the cytokine and chemokine profiles of control and knock out (KO) cells. Antibody mediated, targeted depletion of T cell and MDSCs were performed to evaluate their role in antitumor immune responses.

RESULTS

In SCLL, FGFR1 activation silences miR-146b-5p through DNMT1-mediated promoter methylation, which derepresses the downstream target IRAK1. IRAK1 KO SCLL cells were xenografted into immunocompetent syngeneic mice where the typical rapid progression of disease was lost and the mice remained disease free. IRAK1 in this system has no effect on cell cycle progression or apoptosis and robust growth of the KO cells in immunodeficient mice suggested an effect on immune surveillance. Depletion of T-cells in immunocompetent mice restored leukemogenesis of the KO cells, and tumor killing assays confirmed the role of T cells in tumor clearance. Analysis of the immune cell profile in mice transplanted with the IRAK1 expressing mock control (MC) cells shows that there is an increase in levels of myeloid-derived suppressor cells (MDSCs) with a concomitant decrease in CD4+/CD8+ T-cell levels. MDSC suppression assays and depletion experiments showed that these MDSCs were responsible for suppression of the T cell mediated leukemia cell elimination. Immuno-profiling of a panel of secreted cytokines and chemokines showed that activation of IFN-γ is specifically impaired in the KO cells. In vitro and in vivo expression assays and engraftment with interferon gamma receptor-1 (IFNGR1) null mice and IFNG KO SCLL cells, showed the leukemia cells produced IFN-γ directly participating in the induction of MDSCs to establish immune evasion. Inhibition of IRAK1 using pacritinib suppresses leukemogenesis with impaired induction of MDSCs and attenuated suppression of CD4+/CD8+ T-cells.

CONCLUSIONS

IRAK1 orchestrates a previously unknown FGFR1-directed immune escape mechanism in SCLL, through induction of MDSCs via regulation of IFN-γ signaling from leukemia cells, and targeting IRAK1 may provide a means of suppressing tumor growth in this syndrome by restoring immune surveillance.

Mechanisms of resistance to FGFR1 inhibitors in FGFR1-driven leukemias and lymphomas: implications for optimized treatment

Myeloid and lymphoid neoplasms with eosinophilia and FGFR1 rearrangements (MLN-eo FGFR1) disease is derived from a pluripotent hematopoietic stem cell and has a complex presentation with a myeloproliferative disorder with or without eosinophilia and frequently presents with mixed lineage T- or B-lymphomas. The myeloproliferative disease frequently progresses to AML and lymphoid neoplasms can develop into acute lymphomas. No matter the cell type involved, or clinical presentation, chromosome translocations involving the FGFR1 kinase and various partner genes, which leads to constitutive activation of downstream oncogenic signaling cascades. These patients are not responsive to treatment regimens developed for other acute leukemias and survival is poor. Recent development of specific FGFR1 inhibitors has suggested an alternative therapeutic approach but resistance is likely to evolve over time. Mouse models of this disease syndrome have been developed and are being used for preclinical evaluation of FGFR1 inhibitors. Cell lines from these models have now been developed and have been used to investigate the mechanisms of resistance that might be expected in clinical cases. So far, a V561M mutation in the kinases domain and deletion of PTEN have been recognized as leading to resistance and both operate through the PI3K/AKT signaling axis. One of the important consequences is the suppression of PUMA, a potent enforcer of apoptosis, which operates through BCL2. Targeting BCL2 in the resistant cells leads to suppression of leukemia development in mouse models, which potentially provides an opportunity to treat patients that become resistant to FGFR1 inhibitors. In addition, elucidation of molecular mechanisms underlying FGFR1-driven leukemias and lymphomas also provides new targets for combined treatment as another option to bypass the FGFR1 inhibitor resistance and improve patient outcome.

Oncogenic FGFR Fusions Produce Centrosome and Cilia Defects by Ectopic Signaling

A single primary cilium projects from most vertebrate cells to guide cell fate decisions. A growing list of signaling molecules is found to function through cilia and control ciliogenesis, including the fibroblast growth factor receptors (FGFR). Aberrant FGFR activity produces abnormal cilia with deregulated signaling, which contributes to pathogenesis of the FGFR-mediated genetic disorders. FGFR lesions are also found in cancer, raising a possibility of cilia involvement in the neoplastic transformation and tumor progression. Here, we focus on FGFR gene fusions, and discuss the possible mechanisms by which they function as oncogenic drivers. We show that a substantial portion of the FGFR fusion partners are proteins associated with the centrosome cycle, including organization of the mitotic spindle and ciliogenesis. The functions of centrosome proteins are often lost with the gene fusion, leading to haploinsufficiency that induces cilia loss and deregulated cell division. We speculate that this complements the ectopic FGFR activity and drives the FGFR fusion cancers.

Avadomide induces degradation of ZMYM2 fusion oncoproteins in hematologic malignancies

Thalidomide analogs exert their therapeutic effects by binding to the CRL4^CRBN E3 ubiquitin ligase, promoting ubiquitination and subsequent proteasomal degradation of specific protein substrates. Drug-induced degradation of IKZF1 and IKZF3 in B-cell malignancies demonstrates the clinical utility of targeting disease-relevant transcription factors for degradation. Here, we found that avadomide (CC-122) induces CRBN-dependent ubiquitination and proteasomal degradation of ZMYM2 (ZNF198), a transcription factor involved in balanced chromosomal rearrangements with FGFR1 and FLT3 in aggressive forms of hematologic malignancies. The minimal drug-responsive element of ZMYM2 is a zinc-chelating MYM domain and is contained in the N-terminal portion of ZMYM2 that is universally included in the derived fusion proteins. We demonstrate that avadomide has the ability to induce proteasomal degradation of ZMYM2-FGFR1 and ZMYM2-FLT3 chimeric oncoproteins, both in vitro and in vivo. Our findings suggest that patients with hematologic malignancies harboring these ZMYM2 fusion proteins may benefit from avadomide treatment.

[Ponatinib inhibits growth of patient-derived xenograft of cholangiocarcinoma expressing FGFR2-CCDC6 fusion protein in nude mice]

OBJECTIVE

To investigate the antitumor effect of ponatinib on the growth of cholangiocarcinoma xenograft derived from a clinical patient in a mouse model expressing FGFR2-CCDC6 fusion protein.

METHODS

Lung metastatic tumor tissue was collected from a patient with advanced intrahepatic cholangiocarcinoma and implanted subcutaneously a NOD/SCID/ Il2rg-knockout (NSG) mouse. The tumor tissues were harvested and transplanted in nude mice to establish mouse models bearing patient-derived xenograft (PDX) of cholangiocarcinoma expressing FGFR2-CCDC6 fusion protein. The PDX mouse models were divided into 4 groups for treatment with citrate buffer (control group), intragastric administration of 20 mg/kg ponatinib dissolved in citrate buffer (ponatinib group), weekly intraperitoneal injections of 50 mg/kg gemcitabine and 2.5 mg/ kg cisplatin (gemcitabine group), or ponatinib combined with gemcitabine and cisplatin at the same doses (10 mice in each group, and 9 mice were evaluated in ponatinib group). The expressions of p-FGFR, p-FRS2, p-AKT, p-ERK, CD31, and Ki-67 in the xenografts were evaluated with immunohistochemistry, and cell apoptosis was analyzed with cleaved caspase-3 (CC3) staining and TUNEL staining. Western blotting was used to detect the expressions of FGFR2, p-FGFR, AKT, p-AKT, ERK, p-ERK, FRS2 and p-FRS2 in the tumor tissues.

RESULTS

Compared with those in the control group, the mice in ponatinib group showed a significantly reduced tumor volume (P < 0.0001) and suppressed tumor cell proliferation with significantly increased cell apoptosis. Western blotting and immunohistochemistry revealed obviously lowered phosphorylation level of FGFR and its downstream signal markers FRS2, AKT and ERK in the xenografts from ponatinib-treated mice. Gemcitabine treatment combined with cisplatin more effectively inhibited tumor growth than ponatinib alone (P < 0.0001) but did not further decrease the phosphorylation levels of FGFR or its downstream signaling molecules FRS2, AKT and ERK.

CONCLUSIONS

Ponatinib can regulate FGFR signaling to inhibit the proliferation and induce apoptosis of tumor cells in mice bearing patient-derived cholangiocarcinoma xenograft with FGFR2 fusion. FGFR inhibitor can serve as a treatment option for patients with cholangiocarcinoma with FGFR2 fusion.

Downregulation of PUMA underlies resistance to FGFR1 inhibitors in the stem cell leukemia/lymphoma syndrome

Resistance to molecular therapies frequently occur due to genetic changes affecting the targeted pathway. In myeloid and lymphoid leukemias/lymphomas resulting from constitutive activation of FGFR1 kinases, resistance has been shown to be due either to mutations in FGFR1 or deletions of PTEN. RNA-Seq analysis of the resistant clones demonstrates expression changes in cell death pathways centering on the p53 upregulated modulator of apoptosis (Puma) protein. Treatment with different tyrosine kinase inhibitors (TKIs) revealed that, in both FGFR1 mutation and Pten deletion-mediated resistance, sustained Akt activation in resistant cells leads to compromised Puma activation, resulting in suppression of TKI-induced apoptosis. This suppression of Puma is achieved as a result of sequestration of inactivated p-Foxo3a in the cytoplasm. CRISPR/Cas9 mediated knockout of Puma in leukemic cells led to an increased drug resistance in the knockout cells demonstrating a direct role in TKI resistance. Since Puma promotes cell death by targeting Bcl2, TKI-resistant cells showed high Bcl2 levels and targeting Bcl2 with Venetoclax (ABT199) led to increased apoptosis in these cells. In vivo treatment of mice xenografted with resistant cells using ABT199 suppressed leukemogenesis and led to prolonged survival. This in-depth survey of the underlying genetic mechanisms of resistance has identified a potential means of treating FGFR1-driven malignancies that are resistant to FGFR1 inhibitors.

Cardiotoxicity of the BCR-ABL1 tyrosine kinase inhibitors: Emphasis on ponatinib

The advent of tyrosine kinase inhibitors (TKIs) targeted therapy revolutionized the treatment of chronic myeloid leukemia (CML) patients. However, cardiotoxicity associated with these targeted therapies puts the cancer survivors at higher risk. Ponatinib is a third-generation TKI for the treatment of CML patients having gatekeeper mutation T315I, which is resistant to the first and second generation of TKIs, namely, imatinib, nilotinib, dasatinib, and bosutinib. Multiple unbiased screening from our lab and others have identified ponatinib as most cardiotoxic FDA approved TKI among the entire FDA approved TKI family (total 50+). Indeed, ponatinib is the only treatment option for CML patients with T315I mutation. This review focusses on the cardiovascular risks and mechanism/s associated with CML TKIs with a particular focus on ponatinib cardiotoxicity. We have summarized our recent findings with transgenic zebrafish line harboring BNP luciferase activity to demonstrate the cardiotoxic potential of ponatinib. Additionally, we will review the recent discoveries reported by our and other laboratories that ponatinib primarily exerts its cardiotoxicity via an off-target effect on cardiomyocyte prosurvival signaling pathways, AKT and ERK. Finally, we will shed light on future directions for minimizing the adverse sequelae associated with CML-TKIs.

Ponatinib-induced cardiotoxicity: delineating the signalling mechanisms and potential rescue strategies

AIMS

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myelogenous leukaemia (CML). However, cardiotoxicity of these agents remains a serious concern. The underlying mechanism of these adverse cardiac effects is largely unknown. Delineation of the underlying mechanisms of TKIs associated cardiac dysfunction could guide potential prevention strategies, rescue approaches, and future drug design. This study aimed to determine the cardiotoxic potential of approved CML TKIs, define the associated signalling mechanism and identify potential alternatives.

METHODS AND RESULTS

In this study, we employed a zebrafish transgenic BNP reporter line that expresses luciferase under control of the nppb promoter (nppb:F-Luciferase) to assess the cardiotoxicity of all approved CML TKIs. Our in vivo screen identified ponatinib as the most cardiotoxic agent among the approved CML TKIs. Then using a combination of zebrafish and isolated neonatal rat cardiomyocytes, we delineated the signalling mechanism of ponatinib-induced cardiotoxicity by demonstrating that ponatinib inhibits cardiac prosurvival signalling pathways AKT and extra-cellular-signal-regulated kinase (ERK), and induces cardiomyocyte apoptosis. As a proof of concept, we augmented AKT and ERK signalling by administration of Neuregulin-1β (NRG-1β), and this prevented ponatinib-induced cardiomyocyte apoptosis. We also demonstrate that ponatinib-induced cardiotoxicity is not mediated by inhibition of fibroblast growth factor signalling, a well-known target of ponatinib. Finally, our comparative profiling for the cardiotoxic potential of CML approved TKIs, identified asciminib (ABL001) as a potentially much less cardiotoxic treatment option for CML patients with the T315I mutation.

CONCLUSION

Herein, we used a combination of in vivo and in vitro methods to systematically screen CML TKIs for cardiotoxicity, identify novel molecular mechanisms for TKI cardiotoxicity, and identify less cardiotoxic alternatives.

DNA methyltransferase 1-mediated CpG methylation of the miR-150-5p promoter contributes to fibroblast growth factor receptor 1-driven leukemogenesis

MicroRNA-150-5p (miR-150-5p) plays a complex role in normal early hematopoietic development and is also implicated in the development of various different leukemias. We have reported previously that, in myeloid and lymphoid malignancies associated with dysregulated fibroblast growth factor receptor 1 (FGFR1) activities, miR-150-5p is down-regulated compared with healthy cells. Here, using murine cells, we found that this down-regulation is accompanied by CpG methylation of the miR-150-5p promoter region. Of note, analysis of human acute lymphoblastic leukemia (ALL) cohorts also revealed an inverse relationship between miR-150-5p expression and disease progression. We also found that the DNA methyltransferase 1 (DNMT1) enzyme is highly up-regulated in FGFR1-driven leukemias and lymphomas and that FGFR1 inhibition reduces DNMT1 expression. DNMT1 knockdown in stem cell leukemia/lymphoma (SCLL) cells increased miR-150-5p levels and reduced levels of the MYB proto-oncogene transcription factor, a key regulator of leukemogenesis. FGFR1 directly activates the MYC proto-oncogene basic helix-loop-helix transcription factor, which, as we show here, binds and activates the DNMT1 promoter. MYC knockdown decreased DNMT1 expression, which, in turn, increased miR-150-5p expression. One of the known targets of miR-150-5p is MYB, and treatment of leukemic cells with the MYB inhibitor mebendazole dose-dependently increased apoptosis and reduced cell viability. Moreover, mebendazole treatment of murine xenografts models of FGFR1-driven leukemias enhanced survival. These findings provide evidence that MYC activates MYB by up-regulating DNMT1, which silences miR-150-5p and promotes SCLL progression. We propose that inclusion of mebendazole in a combination therapy with FGFR1 inhibitors may be a valuable option to manage SCLL.

Critical individual roles of the BCR and FGFR1 kinase domains in BCR-FGFR1-driven stem cell leukemia/lymphoma syndrome

Constitutive activation of FGFR1, as a result of diverse chromosome translocations, is the hallmark of stem cell leukemia/lymphoma syndrome. The BCR-FGFR1 variant is unique in that the BCR component contributes a serine-threonine kinase (STK) to the N-terminal end of the chimeric FGFR1 kinase. We have deleted the STK domain and mutated the critical Y177 residue and demonstrate that the transforming activity of these mutated genes is reduced compared to the BCR-FGFR1 parental kinase. In addition, we demonstrate that deletion of the FGFR1 tyrosine kinase domain abrogates transforming ability, which is not compensated for by BCR STK activity. Unbiased screening for proteins that are inactivated as a result of loss of the BCR STK identified activated S6 kinase and SHP2 kinase. Genetic and pharmacological inhibition of SHP2 function in SCLL cells expressing BCR-FGFR1 in vitro leads to reduced viability and increased apoptosis. In vivo treatment of SCLL in mice with SHP099 leads to suppression of leukemogenesis, supporting an important role for SHP2 in FGFR1-driven leukemogenesis. In combination with the BGJ398 FGFR1 inhibitor, cell viability in vitro is further suppressed and acts synergistically with SHP099 in vivo suggesting a potential combined targeted therapy option in this subtype of SCLL disease.

World Health Organization-defined eosinophilic disorders: 2019 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of non-hematologic (secondary or reactive) and hematologic (primary, clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 10⁹ /L, and may be associated with tissue damage. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of various tests. They include morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ-hybridization, flow immunophenotyping, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the MPN subtype, "chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant hypereosinophilia is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (eg, <1.5 × 10⁹ /L) without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES. Hydroxyurea and interferon-alfa have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. In addition to hydroxyurea, second line cytotoxic chemotherapy agents, and hematopoietic stem cell transplantation have been used for aggressive forms of HES and CEL, with outcomes reported for limited numbers of patients. The use of antibodies against interleukin-5 (IL-5) (mepolizumab), the IL-5 receptor (benralizumab), as well as other targets on eosinophils remains an active area of investigation.

Thrombotic microangiopathy as a cause of cardiovascular toxicity from the BCR-ABL1 tyrosine kinase inhibitor ponatinib

The third-generation tyrosine kinase inhibitor (TKI) ponatinib has been associated with high rates of acute ischemic events. The pathophysiology responsible for these events is unknown. We hypothesized that ponatinib produces an endothelial angiopathy involving excessive endothelial-associated von Willebrand factor (VWF) and secondary platelet adhesion. In wild-type mice and ApoE-/- mice on a Western diet, ultrasound molecular imaging of the thoracic aorta for VWF A1-domain and glycoprotein-Ibα was performed to quantify endothelial-associated VWF and platelet adhesion. After treatment of wild-type mice for 7 days, aortic molecular signal for endothelial-associated VWF and platelet adhesion were five- to sixfold higher in ponatinib vs sham therapy (P < .001), whereas dasatinib had no effect. In ApoE-/- mice, aortic VWF and platelet signals were two- to fourfold higher for ponatinib-treated compared with sham-treated mice (P < .05) and were significantly higher than in treated wild-type mice (P < .05). Platelet and VWF signals in ponatinib-treated mice were significantly reduced by N-acetylcysteine and completely eliminated by recombinant ADAMTS13. Ponatinib produced segmental left ventricular wall motion abnormalities in 33% of wild-type and 45% of ApoE-/- mice and corresponding patchy perfusion defects, yet coronary arteries were normal on angiography. Instead, a global microvascular angiopathy was detected by immunohistochemistry and by intravital microscopy observation of platelet aggregates and nets associated with endothelial cells and leukocytes. Our findings reveal a new form of vascular toxicity for the TKI ponatinib that involves VWF-mediated platelet adhesion and a secondary microvascular angiopathy that produces ischemic wall motion abnormalities. These processes can be mitigated by interventions known to reduce VWF multimer size.

FGFR1 Expression and Role in Migration in Low and High Grade Pediatric Gliomas

The heterogeneous and invasive nature of pediatric gliomas poses significant treatment challenges, highlighting the importance of identifying novel chemotherapeutic targets. Recently, recurrent Fibroblast growth factor receptor 1 (FGFR1) mutations in pediatric gliomas have been reported. Here, we explored the clinical relevance of FGFR1 expression, cell migration in low and high grade pediatric gliomas and the role of FGFR1 in cell migration/invasion as a potential chemotherapeutic target. A high density tissue microarray (TMA) was used to investigate associations between FGFR1 and activated phosphorylated FGFR1 (pFGFR1) expression and various clinicopathologic parameters. Expression of FGFR1 and pFGFR1 were measured by immunofluorescence and by immunohistochemistry (IHC) in 3D spheroids in five rare patient-derived pediatric low-grade glioma (pLGG) and two established high-grade glioma (pHGG) cell lines. Two-dimensional (2D) and three-dimensional (3D) migration assays were performed for migration and inhibitor studies with three FGFR1 inhibitors. High FGFR1 expression was associated with age, malignancy, tumor location and tumor grade among astrocytomas. Membranous pFGFR1 was associated with malignancy and tumor grade. All glioma cell lines exhibited varying levels of FGFR1 and pFGFR1 expression and migratory phenotypes. There were significant anti-migratory effects on the pHGG cell lines with inhibitor treatment and anti-migratory or pro-migratory responses to FGFR1 inhibition in the pLGGs. Our findings support further research to target FGFR1 signaling in pediatric gliomas.

Potent antiproliferative effect of fatty-acid derivative AIC-47 on leukemic mice harboring BCR-ABL mutation

Therapy based on targeted inhibition of BCR‐ABL tyrosine kinase has greatly improved the prognosis for patients with Philadelphia chromosome (Ph)‐positive leukemia and tyrosine kinase inhibitors (TKI) have become standard therapy. However, some patients acquire resistance to TKI that is frequently associated with point mutations in BCR‐ABL. We previously reported that a medium‐chain fatty‐acid derivative AIC‐47 induced transcriptional suppression of BCR‐ABL and perturbation of the Warburg effect, leading to growth inhibition in Ph‐positive leukemia cells. Herein, we showed that AIC‐47 had anti‐leukemic effects in either wild type (WT)‐ or mutated‐BCR‐ABL‐harboring cells. AIC‐47 suppressed transcription of BCR‐ABL gene regardless of the mutation through downregulation of transcriptional activator, c‐Myc. Reprogramming of the metabolic pathway has been reported to be associated with resistance to anti‐cancer drugs; however, we found that a point mutation of BCR‐ABL was independent of the profile of pyruvate kinase muscle (PKM) isoform expression. Even in T315I‐mutated cells, AIC‐47 induced switching of the expression profile of PKM isoforms from PKM2 to PKM1, suggesting that AIC‐47 disrupted the Warburg effect. In a leukemic mouse model, AIC‐47 greatly suppressed the increase in BCR‐ABLmRNA level and improved hepatosplenomegaly regardless of the BCR‐ABL mutation. Notably, the improvement of splenomegaly by AIC‐47 was remarkable and might be equal to or greater than that of TKI. These findings suggest that AIC‐47 might be a promising agent for overcoming the resistance of Ph‐positive leukemia to therapy.

Recent Studies on Ponatinib in Cancers Other Than Chronic Myeloid Leukemia

Ponatinib is a third line drug for the treatment of chronic myeloid leukemia patients, especially those that develop the gatekeeper mutation T315I, which is resistant to the first and the second line drugs imatinib, nilotinib, dasatinib and bosutinib. The compound was first identified as a pan Bcr-Abl and Src kinase inhibitor. Further studies have indicated that it is a multitargeted inhibitor that is active on FGFRs, RET, AKT, ERK1/2, KIT, MEKK2 and other kinases. For this reason, the compound has been evaluated on several cancers in which these kinases play important roles, including thyroid, breast, ovary and lung cancer, neuroblastoma, rhabdoid tumours and in myeloproliferative disorders. Ponatinib is also being tested in clinical trials to evaluate its activity in FLT3-ITD acute myelogenous leukemia, head and neck cancers, certain type of lung cancer, gastrointestinal stromal tumours and other malignancies. In this review we report the most recent preclinical and clinical studies on ponatinib in cancers other than CML, with the aim of giving a complete overview of this interesting compound.

Loss of the BCR-FGFR1 GEF Domain Suppresses RHOA Activation and Enhances B-Lymphomagenesis in Mice

Transformation of hematopoietic stem cells by the BCR-FGFR1 fusion kinase found in a variant of stem cell leukemia/lymphoma (SCLL) syndrome leads to development of B-lymphomas in syngeneic mice and humans. In this study, we show that the relatively rapid onset of this leukemia is potentially related to oncogenic domains within the BCR component. BCR recruited a guanidine nucleotide exchange factor (GEF) domain to the fusion kinase to facilitate activation of small GTPases such as the Ras homology gene family, member A (RHOA). Deletion of this GEF domain increased leukemogenesis, enhanced cell survival and proliferation, and promoted stem cell expansion and lymph node metastasis. This suggests that, in an SCLL context, the presence of the endogenous GEF motif leads to reduced leukemogenesis. Indeed, loss of the GEF domain suppressed activation of RHOA and PTEN, leading to increased activation of AKT. Loss of the GEF domain enhanced cell proliferation and invasion potential, which was also observed in cells in which RHOA is knocked down, supported by the observation that overexpression of RHOA leads to reduced viability and invasion. In vivo depletion of RHOA in SCLL cells significantly increased disease progression and shortened latency. Collectively, these data show that the BCR GEF domain affects phenotypes associated with progression of SCLL through suppression of RHOA signaling. SIGNIFICANCE: RHOA activation is a critical event in the progression of BCR-FGFR1-driven leukemogenesis in stem cell leukemia and lymphoma syndrome and is regulated by the BCR GEF domain.

FGFR1 fusion kinase regulation of MYC expression drives development of stem cell leukemia/lymphoma syndrome

Oncogenic transformation of hematopoietic stem cells by chimeric fusion kinases causing constitutive activation of FGFR1 leads to a stem cell leukemia/lymphoma (SCLL) syndrome, accompanied by widespread dysregulation of gene activity. We now show that FGFR1 activation is associated with upregulation of MYC and pharmacological suppression of FGFR1 activation leads to downregulation of MYC and suppression of MYC target genes. Luciferase reporter assays demonstrate that FGFR1 can directly regulate MYC expression and this effect is enhanced in the presence of chimeric FGFR1 kinases. In SCLL cells, a truncated form of FGFR1 is generated by granzyme B cleavage of the chimeric kinases, producing a nucleus-restricted derivative that can bind MYC regulatory regions. Mutation of the granzyme B cleavage site prevents relocation to the nucleus but does not suppress MYC activation, suggesting additional mechanisms of MYC activation in the presence of cytoplasm-restricted chimeric kinases. We show that one of these mechanisms involves activating cytoplasmic STAT5, which upregulates MYC independent of the truncated FGFR1 kinase. Targeting MYC function using shRNA knockdown and 10054-F8 in SCLL cells leads to inhibition of cell proliferation and synergizes with the BGJ398 FGFR1 inhibitor, suggesting a combination therapy that could be used in the treatment of SCLL.

Novel multiple tyrosine kinase inhibitor ponatinib inhibits bFGF-activated signaling in neuroblastoma cells and suppresses neuroblastoma growth in vivo

Neuroblastoma (NB) is one of the most common pediatric malignancies in children. Abnormal activation of receptor tyrosine kinases contributes to the pathological development of NB. Therefore, targeting tyrosine kinase receptors to cure NB is a promising strategy. Here, we report that a multi-targeted tyrosine kinase inhibitor ponatinib inhibited NB cell proliferation and induced NB cell apoptosis in a dose-dependent manner. In addition, ponatinib suppressed the colony formation ability of NB cells. Mechanistically, ponatinib effectively inhibited the FGFR1-activated signaling pathway. Ponatinib also enhanced the cytotoxic effects of doxorubicin on NB cells. Furthermore, ponatinib demonstrated anti-tumor efficacy in vivo by inhibiting tumor growth in an orthotopic xenograft NB mouse model. In summary, our results showed that ponatinib inhibited NB growth both in vitro and in vivo.

SCLLTargeting FGFR1 to suppress leukemogenesis in syndromic and de novo AML in murine models

Although over expression of chimeric FGFR1 kinase consistently leads to the development of AML in the rare Stem Cell Leukemia and Lymphoma syndrome, we now show that overexpression of FGFR1 is also seen in up to 20% of non-syndromic, de novo AML. To determine whether targeting FGFR1 in both of these AML subtypes can suppress leukemogenesis, we evaluated the effects of different FGFR1 inhibitors in a side-by-side comparison for their ability to affect in vitro proliferation in FGFR1 overexpressing murine and human cells lines. Three newly developed pan-FGFR inhibitors, AZD4547, BGJ398 and JNJ42756493, show a significantly improved efficacy over the more established FGFR inhibitors, PD173074 and TKI258. To examine whether targeting FGFR1 suppresses leukemogenesis in de novo AML in vivo, we created xenografts in immunocompromized mice from primary, de novo AML that showed > 3-fold increased expression of FGFR1. Using BGJ398, the most potent inhibitor identified in the in vitro studies, AML progression in these mice was significantly suppressed compared with vehicle treated animals and overall survival improved. Importantly, no difference in disease course or survival was seen in AML xenografts that did not show overexpression of FGFR1. These observations support the idea that FGFR1 is a driver oncogene in de novo, FGFR1-overexpressing AML and that molecularly targeted therapies using FGFR1 inhibitors may provide a valuable therapeutic regimen for all FGFR1-overexpressing AML.

World Health Organization-defined eosinophilic disorders: 2017 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of nonhematologic (secondary or reactive) and hematologic (primary, clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia has generally been defined as a peripheral blood eosinophil count greater than 1500/mm³ and may be associated with tissue damage. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of morphologic review of the blood and marrow, standard cytogenetics, fluorescent in situ-hybridization, flow immunocytometry, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic myeloid or lymphoproliferative disorder.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes which includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2," and the "MPN subtype, chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant hypereosinophilia is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (e.g., < 1500/mm³ ) without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES. Hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and steroid-refractory cases of HES. In addition to hydroxyurea, second line cytotoxic chemotherapy agents and hematopoietic cell transplant have been used for aggressive forms of HES and CEL with outcomes reported for limited numbers of patients. The use of antibodies against interleukin-5 (IL-5) (mepolizumab), the IL-5 receptor (benralizumab), and CD52 (alemtuzumab), as well as other targets on eosinophils remains an active area of investigation.

YM155 inhibits topoisomerase function

YM155 (sepantronium bromide) has been evaluated in clinical trials as a survivin suppressant, but despite positive signals from early work, later studies were negative. Clarification of the mechanism of action of YM155 is important for its further development. YM155 affects cells in a cell cycle-specific manner. When cells are in G1, YM155 prevented their progression through the S phase, leaving the cells at G1/S when exposed to YM155. Passage through mitosis from G2 is also defective following YM155 exposure. In this study, YM155 did not behave like a typical DNA intercalator in viscosity, circular dichroism, and absorption spectroscopy studies. In addition, molecular modeling experiments ruled out YM155 DNA interaction to produce DNA intercalation. We show that YM155 inhibited topoisomerase 2α decatenation and topoisomerase 1-mediated cleavage of DNA, suggesting that YM155 inhibits the enzyme function. Consistent with these findings, DNA double-strand break repair was also inhibited by YM155.

Mutation in the FGFR1 tyrosine kinase domain or inactivation of PTEN is associated with acquired resistance to FGFR inhibitors in FGFR1-driven leukemia/lymphomas

Stem cell leukemia/lymphoma syndrome (SCLL) is driven by constitutive activation of chimeric FGFR1 kinases generated by chromosome translocations. We have shown that FGFR inhibitors significantly suppress leukemia and lymphoma development in vivo, and cell viability in vitro. Since resistance to targeted therapies is a major reason for relapse, we developed FGFR1-overexpressing mouse and human cell lines that are resistant to the specific FGFR inhibitors AZD4547 and BGJ398, as well as non-specific inhibitors, such as ponatinib, TKI258 and E3810. Two mutually exclusive mechanisms for resistance were demonstrated; an activating V561M mutation in the FGFR1 kinase domain and mutational inactivation of PTEN resulting in increased PI3K/AKT activity. Ectopic expression of PTEN in the PTEN-mutant cells resensitizes them to FGFR inhibitors. Treatment of resistant cells with BGJ398, in combination with the BEZ235 PI3K inhibitor, shows an additive effect on growth in vitro and prolongs survival in xenograft models in vivo. These studies provide the first direct evidence for both the involvement of the FGFR1 V561M mutation and PTEN inactivation in the development of resistance in leukemias overexpressing chimeric FGFR1. These studies also provide a potential strategy to treat leukemias and lymphomas driven by FGFR1 activation that become resistant to FGFR1 inhibitors.

Response to Tyrosine Kinase Inhibitors in Myeloproliferative Neoplasia with 8p11 Translocation and CEP110-FGFR1 Rearrangement

This brief communication reports on a patient with an exceedingly rare "8p11 (eight-p-eleven) myeloproliferative syndrome" (EMS) with CEP110-FGFR1 rearrangement who responded to treatment with the multi-tyrosine kinase inhibitor (TKI) dasatinib. Dasatinib improved quality of life substantially by increasing blood counts and reducing the need for transfusions. This report demonstrates that the second-generation TKI may provide a therapeutic option for elderly and frail EMS patients who cannot be offered aggressive therapy, including allogeneic hematopoietic cell transplantation. The Oncologist 2017;22:480-483.

Activity of fibroblast growth factor receptor inhibitors TKI258, ponatinib and AZD4547 against TPR‑FGFR1 fusion

8p11 myeloproliferative syndrome (EMS) is a rare disease characterized by the constitutive activation of fibroblast growth factor receptor 1 (FGFR1). To date, four cases of EMS with the chromosomal translocation, t(1;8)(q25;p11.2), have been reported. In the present study, TPR-FGFR1-expressing Baf3 cells were established and confirmed by polymerase chain reaction. To identify the most promising drug for EMS, the activities and associated mechanism of three tyrosine kinase inhibitors (TKIs), TKI258, ponatinib and AZD4547, against TPR-FGFR1 were tested by MTT assay, flow cytometry and western blot. The data demonstrated that TPR-FGFR1 was localized in the cytoplasm, and was able to transform interleukin-3-dependent hematopoietic Baf3 cells into growth factor-independent cells. All of the three TKIs markedly inhibited the proliferation of TPR-FGFR1-expressing Baf3 cells, and the activation of FGFR1 and the downstream signaling molecules, extracellular signal-regulated kinase 1/2, phospholipiase Cγ and signal transducer and activator of transcription 5. AZD4547 was the most efficient drug, and TKI258 was the least. By contrast, no significant difference was found among the three drugs on their effect on cell apoptosis. Taken together, the data obtained in the present study suggested that AZD4547 had increased potency, compared with TKI258 and ponatinib, for the treatment of EMS.

Antitumor effects and molecular mechanisms of ponatinib on endometrial cancer cells harboring activating FGFR2 mutations

Aberrant mutational activation of FGFR2 is associated with endometrial cancers (ECs). AP24534 (ponatinib) currently undergoing clinical trials has been known to be an orally available multi-targeted tyrosine kinase inhibitor. Our biochemical kinase assay showed that AP24534 is potent against wild-type FGFR1-4 and 5 mutant FGFRs (V561M-FGFR1, N549H-FGFR2, K650E-FGFR3, G697C-FGFR3, N535K-FGFR4) and possesses the strongest kinase-inhibitory activity on N549H-FGFR2 (IC50 of 0.5 nM) among all FGFRs tested. We therefore investigated the effects of AP24534 on endometrial cancer cells harboring activating FGFR2 mutations and explored the underlying molecular mechanisms. AP24534 significantly inhibited the proliferation of endometrial cancer cells bearing activating FGFR2 mutations (N549K, K310R/N549K, S252W) and mainly induced G1/S cell cycle arrest leading to apoptosis. AP24534 also diminished the kinase activity of immunoprecipitated FGFR2 derived from MFE-296 and MFE-280 cells and reduced the phosphorylation of FGFR2 and FRS2 on MFE-296 and AN3CA cells. AP24534 caused substantial reductions in ERK phosphorylation, PLCγ signaling and STAT5 signal transduction on ECs bearing FGFR2 activating mutations. Akt signaling pathway was also deactivated by AP24534. AP24534 causes the chemotherapeutic effect through mainly the blockade of ERK, PLCγ and STAT5 signal transduction on ECs. Moreover, AP24534 inhibited migration and invasion of endometrial cancer cells with FGFR2 mutations. In addition, AP24534 significantly blocked anchorage-independent growth of endometrial cancer cells. We, for the first time, report the molecular mechanisms by which AP24534 exerts antitumor effects on ECs with FGFR2 activating mutations, which would provide mechanistic insight into ongoing clinical investigations of AP24534 for ECs.

Transformation of human CD34+ hematopoietic progenitor cells with DEK-NUP214 induces AML in an immunocompromised mouse model

Acute myeloid leukemia (AML) is a heterogeneous disease comprising a large number of subtypes defined by specific chromosome abnormalities. One such subtype carries the t(6;9)(p22;q34) chromosome rearrangement, which leads to expression of the DEK-NUP214 chimeric gene, and has a particularly poor outcome. To provide a better understanding of the molecular etiology of these relatively rare individual AML variants, it is necessary to generate in vivo models, which can also serve as a means to evaluate targeted therapies based on their specific genetic abnormalities. Here, we describe the development of a human cell AML, generated in CD34+ human hematopoietic progenitor cells xenografted into immunocompromised mice that express human myeloid cell growth factors. Within 6 months, these mice develop a human cell AML with phenotypic characteristics of the primary t(6;9) disease and a CD45+CD13+CD34+CD38+ immunophenotype. Gene expression studies show that members of the HOX family of genes (HOXA9, 10, B3, B4 and PBX3) are highly upregulated in the AML from this mouse model as well as from primary human t(6;9) AML. Gene expression analysis also identified several other significantly disregulated pathways involving KRAS, BRCA1 and ALK, for example. This is the first report of a humanized model of the DEK-NUP214 disease and provides a means to study the development and treatment of this particular subtype of AML.

Antitumor effect of FGFR inhibitors on a novel cholangiocarcinoma patient derived xenograft mouse model endogenously expressing an FGFR2-CCDC6 fusion protein

Cholangiocarcinoma is a highly lethal cancer with limited therapeutic options. Recent genomic analysis of cholangiocarcinoma has revealed the presence of fibroblast growth factor receptor 2 (FGFR2) fusion proteins in up to 13% of intrahepatic cholangiocarcinoma (iCCA). FGFR fusions have been identified as a novel oncogenic and druggable target in a number of cancers. In this study, we established a novel cholangiocarcinoma patient derived xenograft (PDX) mouse model bearing an FGFR2-CCDC6 fusion protein from a metastatic lung nodule of an iCCA patient. Using this PDX model, we confirmed the ability of the FGFR inhibitors, ponatinib, dovitinib and BGJ398, to modulate FGFR signaling, inhibit cell proliferation and induce cell apoptosis in cholangiocarcinoma tumors harboring FGFR2 fusions. In addition, BGJ398 appeared to be superior in potency to ponatinib and dovitinib in this model. Our findings provide a strong rationale for the investigation of FGFR inhibitors, particularly BGJ398, as a therapeutic option for cholangiocarcinoma patients harboring FGFR2 fusions.

Development of ZMYM2-FGFR1 driven AML in human CD34+ cells in immunocompromised mice

Acute myelogenous leukemia (AML) has an overall poor survival rate and shows considerable molecular heterogeneity in its etiology. In the WHO classification there are >50 cytogenetic subgroups of AML, many showing highly specific chromosome translocations that lead to constitutive activation of individual kinases. In a rare stem cell leukemia/lymphoma syndrome, translocations involving 8p11 lead to constitutive activation of the fibroblast growth factor receptor 1 (FGFR1) kinase. This disorder shows myeloproliferative disease with almost invariable progresses to AML and conventional therapeutic strategies are largely unsuccessful. Because of the rare nature of this syndrome, models that faithfully recapitulate the human disease are needed to evaluate therapeutic strategies. The t(8;13)(p11;q12) chromosome translocation is most common rearrangement seen in this syndrome and creates a ZMYM2-FGFR1 chimeric kinase. To understand more about the molecular etiology of AML induced by this particular rearrangement, we have created a model human CD34+ cells transplanted into immunocompromized mice which develop myeloproliferative disease that progresses to AML with a long (>12 months) latency period. As in humans, these mice show hepatospenomegaly, hypercellular bone marrow and a CD45 + CD34 + CD13+ immunophenotype. Molecular studies demonstrate upregulation of genes such as KLF4 and FLT3 that promote stemness, and overexpression of MYC, which is associated with suppression of myeloid cell differentiation. This murine model, therefore, provides an opportunity to develop therapeutic strategies against the most common subtype within these FGFR1 driven neoplasms and study the molecular etiology in more depth.

World Health Organization-defined eosinophilic disorders: 2015 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of non-hematologic (secondary or reactive) and hematologic (primary, clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia has generally been defined as a peripheral blood eosinophil count greater than 1,500/mm(3) and may be associated with tissue damage. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of morphologic review of the blood and marrow, standard cytogenetics, fluorescent in situ-hybridization, flow immunocytometry, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic myeloid or lymphoproliferative disorder.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2008 World Health Organization establishes a semi-molecular classification scheme of disease subtypes including 'myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1', chronic eosinophilic leukemia, not otherwise specified, (CEL, NOS), lymphocyte-variant hypereosinophilia, and idiopathic hypereosinophilic syndrome (HES), which is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of the therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (e.g. < 1,500/mm(3) ) without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES. Hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and steroid-refractory cases of HES. In addition to hydroxyurea, second line cytotoxic chemotherapy agents and hematopoietic cell transplant have been used for aggressive forms of HES and CEL with outcomes reported for limited numbers of patients. Although clinical trials have been performed with anti IL-5 (mepolizumab) and anti-CD52 (alemtuzumab) antibodies, their therapeutic role in primary eosinophilic diseases and HES has yet to be established.

Ponatinib as first-line treatment for patients with chronic myeloid leukaemia in chronic phase: a phase 2 study

BACKGROUND

Ponatinib has shown efficacy in patients with refractory chronic myeloid leukaemia (CML) and in those with CML with a Thr315Ile mutation. We aimed to investigate the activity and safety of ponatinib as first-line treatment for patients with chronic-phase CML.

METHODS

We did a single-arm, phase 2 trial at MD Anderson Cancer Center in Houston, TX, USA. Between May 3, 2012, and Sept 24, 2013, we enrolled patients with early (<6 months) chronic-phase CML and treated them with oral ponatinib once a day. Patients enrolled before July 25, 2013, were given a starting dose of 45 mg per day; we lowered this due to tolerability issues and patients enrolled after this date were given a starting dose of 30 mg per day. After a warning by the US Food and Drug Administration (FDA) in Oct 6, 2013, for vascular complications with ponatinib, we started all patients on aspirin 81 mg daily and reduced the dose of ponatinib to 30 mg or 15 mg per day for all patients. The primary endpoint was the proportion of patients who achieved complete cytogenetic response by 6 months in the per-protocol population. This trial is registered with ClinicalTrials.gov, number NCT01570868.

FINDINGS

We enrolled 51 patients. Median follow-up was 20·9 months (IQR 14·9–25·2). 43 patients were started on 45 mg ponatinib every day; eight patients were started on 30 mg per day. 43 (94%) of 46 evaluable patients achieved complete cytogenetic response at 6 months. Most frequent toxicities included skin-related effects (n=35; 69%) and elevated lipase (n=32; 63%). Cardiovascular events (mainly hypertension) occurred in 25 (49%) patients. Grade 3–4 myelosuppression occurred in 15 (29%) patients. Five (10%) patients developed cerebrovascular or vaso-occlusive disease. 43 (85%) patients needed treatment interruptions at some time and 45 (88%) needed dose reductions. The study was terminated June 18, 2014, at the recommendation of the FDA due to concern about the increased risk of thromboembolism with ponatinib.

INTERPRETATION

Patients with newly diagnosed CML in chronic phase respond well to treatment with ponatinib, with most achieving a complete cytogenetic response. Dose adjustment, extensive monitoring, and counselling of the patients for thromboembolic events is needed for patients on ponatinib therapy. However, due to the risk of vascular thrombotic events and the availability of alternative options for these patients, other drugs should be considered first in the frontline setting.

FUNDING

MD Anderson Cancer Center, National Cancer Institute, ARIAD Pharmaceutical.

[Clinical and gene involved of one case of 8p11 myeloproliferative syndrome with ins(13;8)(q12;p11p23)]

OBJECTIVE

To improve the understanding of patients with 8p11 myeloproliferative syndrome (EMS) harboring ins(13;8)(q12;p11p23)/ZNF198 -FGFR1.

METHODS

We reported here a 8p11 EMS case and provided more details on the clinical and molecular features of ins(13;8)(q12;p11p23)/ZNF198-FGFR1，full length ZNF198-FGFR1 was cloned by overlap extension PCR method，and the literatures on this topic were reviewed.

RESULTS

Clinically, the case with ins(13;8)(q12;p11p23)/ZNF198-FGFR1 had distinct hematological and clinical characteristics: hyperleukocytosis, myeloid hyperplasia，widespread adenopathy and lymphoma; Fluorescence in situ hybridization (FISH) disclosed the positive FGFR1 gene rearrangement; Further molecular studies confirmed a mRNA in-frame fusion between exon 17 of the ZNF198 gene and exon 9 of FGFR1 gene ，the full length ZNF198-FGFR1 was composed of a NH2 terminus of ZNF198 including the ZNF and proline-rich domains, whereas the COOH terminus of FGFR1 included 2 tyrosine kinase domains.

CONCLUSION

EMS with ins(13;8)(q12;p11p23)/ZNF198 -FGFR1 was a very rare， distinct myeloproliferative neoplasm, the fusion gene and chimeric protein with constitutive activation of the FGFR1 tyrosine kinase.