Src activation plays an important key role in lymphomagenesis induced by FGFR1 fusion kinases

Formyl-peptide receptor 2 signalling triggers aerobic metabolism of glucose through Nox2-dependent modulation of pyruvate dehydrogenase activity

The human formyl-peptide receptor 2 (FPR2) is activated by an array of ligands. By phospho-proteomic analysis we proved that FPR2 stimulation induces redox-regulated phosphorylation of many proteins involved in cellular metabolic processes. In this study, we investigated metabolic pathways activated in FPR2-stimulated CaLu-6 cells. The results showed an increased concentration of metabolites involved in glucose metabolism, and an enhanced uptake of glucose mediated by GLUT4, the insulin-regulated member of GLUT family. Accordingly, we observed that FPR2 transactivated IGF-IRβ/IRβ through a molecular mechanism that requires Nox2 activity. Since cancer cells support their metabolism via glycolysis, we analysed glucose oxidation and proved that FPR2 signalling promoted kinase activity of the bifunctional enzyme PFKFB2 through FGFR1/FRS2- and Akt-dependent phosphorylation. Furthermore, FPR2 stimulation induced IGF-IRβ/IRβ-, PI3K/Akt- and Nox-dependent inhibition of pyruvate dehydrogenase activity, thus preventing the entry of pyruvate in the tricarboxylic acid cycle. Consequently, we observed an enhanced FGFR-dependent lactate dehydrogenase (LDH) activity and lactate production in FPR2-stimulated cells. As LDH expression is transcriptionally regulated by c-Myc and HIF-1, we demonstrated that FPR2 signalling promoted c-Myc phosphorylation and Nox-dependent HIF-1α stabilization. These results strongly indicate that FPR2-dependent signalling can be explored as a new therapeutic target in treatment of human cancers.

Ruscogenin ameliorates dasatinib-induced intestinal barrier dysfunction via ErbB4/YAP and ROCK/MLC pathways

Dasatinib is effective in the treatment of chronic and acute myeloid leukemia, which could cause the side effect of gastrointestinal bleeding by overdose or longtime use. Ruscogenin (RUS) from the traditional Chinese medicine Ophiopogon japonicas could protect endothelial microvascular barrier function. In this study, the therapeutic effect and underlying mechanisms of RUS were investigated on intestinal barrier dysfunction induced by dasatinib. Male C57BL/6 J mice were given three doses of dasatinib (70, 140, 210 mg/kg, ig) and RUS (3, 10, 30 μg/kg, ip) to explore the effect of dasatinib on intestinal barrier and the intervention of RUS. It was proved that dasatinib could reduce intestinal blood flow, inhibit phosphorylation of EGFR family member v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 4 (ErbB4)/YES-associated protein (YAP) and activation of Rho-associated coiled coil-containing protein kinase (ROCK)/phosphorylation of (myosin light chain) MLC. RUS could significantly increase intestinal blood flow, improve intestinal injury, reduce Evans blue leakage and serum content of FITC-dextran 4 kDa, and increase the expression of connexin (ZO-1, Occludin and VE-cadherin). Meanwhile, the in vitro effect of RUS (0.01, 0.1, 1 μM) on the dysfunction of the endothelial barrier was observed in dasatinib (150 nM)-pretreated HUVECs. The results showed that RUS suppressed dasatinib-induced the leakage of Evans blue, and degradation of F-actin and connexin. Furthermore, RUS could significantly increase the phosphorylation of ErbB4 at Tyr1284 site and YAP at Ser397 site, and inhibit ROCK expression and phosphorylation of MLC at Ser19 site in vivo and in vitro. In conclusion, the present research proved that RUS could suppress the side effects of dasatinib-induced intestinal barrier dysfunction by regulating ErbB4/YAP and ROCK/MLC pathways.

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.

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.

Chronic exposure to FGF2 converts iPSCs into cancer stem cells with an enhanced integrin/focal adhesion/PI3K/AKT axis

We previously demonstrated the conversion of normal stem cells, including induced pluripotent stem cells (iPSCs), into cancer stem cells (CSCs) without genetic manipulation. Herein, we designed a meta-analysis to assess gene expression profiles in different breast cancer cell lines focusing on the secretory factors responsible for conversion. As a result, fibroblast growth factor 2 (FGF2) was found to be the best candidate in T47D and BT549 cells, of which conditioned medium was previously successful in inducing CSCs. When treated with 3.1 μg/ml FGF2, mouse iPSCs not only maintained survival without LIF for three weeks but also acquired growth ability independent of FGF2. The resultant cells exhibited expression of stemness and cancer stem cell markers, sphere-forming ability, differentiation, and tumorigenicity with malignancy. The primary cultures of the tumor confirmed the signatures of CSCs with two different phenotypes with or without GFP expression under control of the Nanog promoter. Bioinformatic analysis of gene expression profiles suggested constitutive autocrine activation of the FGF receptor, integrins, focal adhesions, and PI3K/AKT pathways. FGF2 could potently initiate cancer as a component of the inflammatory microenvironment.

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.

IDDkin: Network-based influence deep diffusion model for enhancing prediction of kinase inhibitors

MOTIVATION

Protein kinases have been the focus of drug discovery research for many years because they play a causal role in many human diseases. Understanding the binding profile of kinase inhibitors is a prerequisite for drug discovery, and traditional methods of predicting kinase inhibitors are time-consuming and inefficient. Calculation-based predictive methods provide a relatively low-cost and high-efficiency approach to the rapid development and effective understanding of the binding profile of kinase inhibitors. Particularly, the continuous improvement of network pharmacology methods provides unprecedented opportunities for drug discovery, network-based computational methods could be employed to aggregate the effective information from heterogeneous sources, which have become a new way for predicting the binding profile of kinase inhibitors.

RESULTS

In this study, we proposed a network-based influence deep diffusion model, named IDDkin, for enhancing the prediction of kinase inhibitors. IDDkin uses deep graph convolutional networks, graph attention networks and adaptive weighting methods to diffuse the effective information of heterogeneous networks. The updated kinase and compound representations are used to predict potential compound-kinase pairs. The experimental results show that the performance of IDDkin is superior to the comparison methods, including the state-of-the art kinase inhibitor prediction method and the classic model widely used in relationship prediction. In experiments conducted to verify its generalizability and in case studies, the IDDkin model also shows excellent performance. All of these results demonstrate the powerful predictive ability of the IDDkin model in the field of kinase inhibitors.

AVAILABILITY AND IMPLEMENTATION

Source code and data can be downloaded from https://github.com/ CS-BIO/IDDkin.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

A new FGFR inhibitor disrupts the TGF-β1-induced fibrotic process

Pulmonary fibrosis (PF) is chronic and irreversible damage to the lung characterized by fibroblast activation and matrix deposition. Although recently approved novel anti‐fibrotic agents can improve the lung function and survival of patients with PF, the overall outcomes remain poor. In this study, a novel imidazopurine compound, 3‐(2‐chloro‐6‐fluorobenzyl)‐1,6,7‐trimethyl‐1H‐imidazo[2,1‐f]purine‐2,4(3H,8H)‐dione (IM‐1918), markedly inhibited transforming growth factor (TGF)‐β‐stimulated reporter activity and reduced the expression of representative fibrotic markers, such as connective tissue growth factor, fibronectin, collagen and α‐smooth muscle actin, on human lung fibroblasts. However, IM‐1918 neither decreased Smad‐2 and Smad‐3 nor affected p38MAPK and JNK. Instead, IM‐1918 reduced Akt and extracellular signal‐regulated kinase 1/2 phosphorylation increased by TGF‐β. Additionally, IM‐1918 inhibited the phosphorylation of fibroblast growth factor receptors 1 and 3. In a bleomycin‐induced murine lung fibrosis model, IM‐1918 profoundly reduced fibrotic areas and decreased collagen and α‐smooth muscle actin accumulation. These results suggest that IM‐1918 can be applied to treat lung fibrosis.

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.

Enhanced cell-cell contact stability and decreased N-cadherin-mediated migration upon fibroblast growth factor receptor-N-cadherin cross talk

N-cadherin adhesion has been reported to enhance cancer and neuronal cell migration either by mediating actomyosin-based force transduction or initiating fibroblast growth factor receptor (FGFR)-dependent biochemical signalling. Here we show that FGFR1 reduces N-cadherin-mediated cell migration. Both proteins are co-stabilised at cell-cell contacts through direct interaction. As a consequence, cell adhesion is strengthened, limiting the migration of cells on N-cadherin. Both the inhibition of migration and the stabilisation of cell adhesions require the FGFR activity stimulated by N-cadherin engagement. FGFR1 stabilises N-cadherin at the cell membrane through a pathway involving Src and p120. Moreover, FGFR1 stimulates the anchoring of N-cadherin to actin. We found that the migratory behaviour of cells depends on an optimum balance between FGFR-regulated N-cadherin adhesion and actin dynamics. Based on these findings we propose a positive feed-back loop between N-cadherin and FGFR at adhesion sites limiting N-cadherin-based single-cell migration.

Identification of metabolic vulnerabilities of receptor tyrosine kinases-driven cancer

One of the biggest hurdles for the development of metabolism-targeted therapies is to identify the responsive tumor subsets. However, the metabolic vulnerabilities for most human cancers remain unclear. Establishing the link between metabolic signatures and the oncogenic alterations of receptor tyrosine kinases (RTK), the most well-defined cancer genotypes, may precisely direct metabolic intervention to a broad patient population. By integrating metabolomics and transcriptomics, we herein show that oncogenic RTK activation causes distinct metabolic preference. Specifically, EGFR activation branches glycolysis to the serine synthesis for nucleotide biosynthesis and redox homeostasis, whereas FGFR activation recycles lactate to fuel oxidative phosphorylation for energy generation. Genetic alterations of EGFR and FGFR stratify the responsive tumors to pharmacological inhibitors that target serine synthesis and lactate fluxes, respectively. Together, this study provides the molecular link between cancer genotypes and metabolic dependency, providing basis for patient stratification in metabolism-targeted therapies.

Cancer subtypes may have distinct metabolic vulnerabilities that can be exploited for therapeutic interventions. Here, the authors show that in lung cancer, genetic activation of distinct oncogenic receptor tyrosine kinases results in unique metabolic liabilities and, in particular, EGFR aberrant cancers rely on the serine biosynthetic pathway while FGFR aberrant cancers rely on glycolysis.

Fibroblast growth factor receptor 1 antagonism attenuates lipopolysaccharide-induced activation of hepatic stellate cells via suppressing inflammation

Activated hepatic stellate cells (HSCs) serve key roles in hepatic fibrosis by producing excessive extracellular matrix (ECM) components. Lipopolysaccharide (LPS) has been found to be associated with hepatic fibrogenesis through direct interactions with HSCs. Recently, the fibroblast growth factor receptor 1 (FGFR1) signalling system was identified as a key player in the process of liver fibrosis. In the present study it was evaluated whether FGFR1 mediated LPS-induced HSCs activation. In cultured cells, FGFR1 was inhibited by either siRNA silencing or by a small-molecule inhibitor in LPS-stimulated HSCs. The blockade of FGFR1 decreased LPS-induced nuclear factor-κB (NF-κB) activation, inflammatory cytokine release, fibrosis, and cell proliferation in HSCs. It was further indicated that LPS triggered FGFR1 phosphorylation via TLR4/c-Src. These findings confirmed the detrimental effect of FGFR1 activation in the pathogenesis of LPS-related HSC activation and revealed that FGFR1 may be an ideal therapeutic target for LPS-induced liver fibrosis.

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.

The miR-17/92 cluster is involved in the molecular etiology of the SCLL syndrome driven by the BCR-FGFR1 chimeric kinase

MicroRNAs (miRNAs) have pathogenic roles in the development of a variety of leukemias. Here we identify miRNAs that have important roles in the development of B lymphomas resulting from the expression of the chimeric BCR-FGFR1 kinase. The miR-17/92 cluster was particularly implicated and forced expression resulted in increased cell proliferation, while inhibiting its function using miRNA sponges reduced cell growth and induced apoptosis. Cells treated with the potent BGJ389 FGFR1 inhibitor led to miR-17/92 downregulation, suggesting regulation by FGFR1. Transient luciferase reporter assays and qRT-PCR detection of endogenous miR-17/92 expression in stable transduced cell lines demonstrated that BCR-FGFR1 can regulate miR-17/92 expression. This positive association of miR-17/92 with BCR-FGFR1 was also confirmed in primary mouse SCLL tissues and primary human CLL samples. miR-17/92 promotes cell proliferation and survival by targeting CDKN1A and PTEN in B-lymphoma cell lines and primary tumors. An inverse correlation in expression levels was seen between miR-17/92 and both CDKN1A and PTEN in two cohorts of CLL patients. Finally, in vivo engraftment studies demonstrated that manipulation of miR-17/92 was sufficient to affect BCR-FGFR1-driven leukemogenesis. Overall, our results define miR-17/92 as a downstream effector of FGFR1 in BCR-FGFR1-driven B-cell lymphoblastic leukemia.

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.

Identification of novel peptoid agonists of fibroblast growth factor receptor using microarray-based screening

Drug development targeting fibroblast growth factor receptors (FGFRs) represents an emerging theme in the field of medicinal chemistry. Considering the fact that most of the currently identified FGFR agonists are long chain peptides with limited stability, the discovery of novel non-peptide FGFR ligands is still highly demanded. A linear one-bead-one-compound peptoid (oligomers of N-substituted glycine units) library with a theoretical diversity of 10⁶ was designed and synthesized. Microarray-based screening led to the identification of four hit sequences 1-4 as FGFR1α ligands, which were further confirmed using both solution-phase and solid-phase binding assays. Western blot results indicated that peptoids 2-4 activated FGFR signaling pathways, resulting in increased levels of p-Akt and p-ERK in different cell lines. Our work discovered novel peptoid ligands as FGFR agonists, shedding new light on FGFR-based drug discovery.

[A rare case of myeloproliferative disease with t(8;13)(p11;q12) associated with eosinophilia and lymphadenopathy]

Myeloproliferative disease associated with FGFR1 rearrangement (8p11), which is included in the 2008 WHO Classification of Myeloid Neoplasms, is a rare and extremely aggressive abnormality. The paper describes a clinical case of a 39-year-old female patient who was detected to have leukocytosis (as high as 47.2·109/l), absolute eosinophilia (as high as 3.1·109/l), and enlarged peripheral lymph nodes during her visit to a doctor. The bone marrow (BM) showed the changes typically encountered in myeloproliferative disease with eosinophilia. The patient was found to have t(8;13)(p11;q12) translocation associated with the rearrangement of the FGFR1 gene located at the 8p11 locus. Molecular and cytogenetic examinations failed to reveal BCR-ABL chimeric transcript, Jak2 V617F mutation, and deletions and translocations involving PDGFRA (4q12) and PDGFRB (5q32-33). The similar changes in the karyotype were also found in the lymph node cells. The undertaken treatment with hydroxyurea and the tyrosine kinase inhibitor dasatinib turned out to be ineffective. The patient underwent allogeneic BM transplantation from a HLA-identical sibling. Graft rejection occurred 6 months later. Allogeneic BM transplantation from the same donor (100% donor chimerism; FGFR1/8р11 translocation was not detected), which was complicated by the development of chronic graft-versus-host reaction, was performed again in March 2015. The patient is being followed up and continues to receive immunosuppressive therapy.

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.

Src family kinases and their role in hematological malignancies

The Src family protein tyrosine kinases (SFKs) are non-receptor intracellular kinases that have important roles in both hematopoiesis and leukemogenesis. The derangement of their expression or activation has been demonstrated to contribute to hematological malignancies. This review first examines the mechanisms of SFK overexpression and hyperactivation, emphasizing the dysregulation of the upstream modulators. Subsequently, the role of SFK up-regulation in the initiation, progression and therapy resistance of many hematological malignancies is also analyzed. The presented evidence endeavors to highlight the influence of SFK up-regulation on an extensive number of hematological malignancies and the need to consider them as candidates in targeted anticancer therapy.

Sepantronium is a DNA damaging agent that synergizes with PLK1 inhibitor volasertib

In a search for novel agents that boost the anti-neoplastic effects of polo-like kinase 1 (PLK1) inhibitor volasertib, we found that a sepantronium and volasertib combination at the nano mole concentration potently inhibited growth of various non-small cell lung cancer (NSCLC) cell lines than either drug alone in vitro. Combination use of volasertib with sepantronium inhibited adaptation of cells to polo arrest. Addition of sepantronium to volasertib prevented accumulation of survivin and cyclin B protein at a concentration causing no appreciable survivin down regulation. Sepantronium induced cell cycle arrest from G1 or G2/M phase. Further studies demonstrated DNA damage of cancer cells when they are treated with sepantronium, which is evidenced by induction of phospho-γH2AX. In line with induction of a DNA damage response in cancer cells, known DNA damage response sensors and transducers ATM, ATR, CHK1, CHK2, p53 are phosphorylated following drug treatment. Meanwhile, expression of CDKN1A, BAX and XRCC5 are induced at the mRNA level as determined by quantitative real time PCR. A single cell electrophoresis assay (Comet assay) of cells treated with sepantronium revealed severe DNA strand breaks. M-phase arrest does not increase the lethality of DNA damage by sepantronium as compared to G1 phase arrest. Knock down of survivin did not cause DNA damage. Hence, sepantronium is a DNA damaging agent that synergizes with volasertib and down-regulation of survivin is likely the consequence of DNA damage induced by sepantronium.

Integrated genomic characterization reveals novel, therapeutically relevant drug targets in FGFR and EGFR pathways in sporadic intrahepatic cholangiocarcinoma

Advanced cholangiocarcinoma continues to harbor a difficult prognosis and therapeutic options have been limited. During the course of a clinical trial of whole genomic sequencing seeking druggable targets, we examined six patients with advanced cholangiocarcinoma. Integrated genome-wide and whole transcriptome sequence analyses were performed on tumors from six patients with advanced, sporadic intrahepatic cholangiocarcinoma (SIC) to identify potential therapeutically actionable events. Among the somatic events captured in our analysis, we uncovered two novel therapeutically relevant genomic contexts that when acted upon, resulted in preliminary evidence of anti-tumor activity. Genome-wide structural analysis of sequence data revealed recurrent translocation events involving the FGFR2 locus in three of six assessed patients. These observations and supporting evidence triggered the use of FGFR inhibitors in these patients. In one example, preliminary anti-tumor activity of pazopanib (in vitro FGFR2 IC₅₀≈350 nM) was noted in a patient with an FGFR2-TACC3 fusion. After progression on pazopanib, the same patient also had stable disease on ponatinib, a pan-FGFR inhibitor (in vitro, FGFR2 IC₅₀≈8 nM). In an independent non-FGFR2 translocation patient, exome and transcriptome analysis revealed an allele specific somatic nonsense mutation (E384X) in ERRFI1, a direct negative regulator of EGFR activation. Rapid and robust disease regression was noted in this ERRFI1 inactivated tumor when treated with erlotinib, an EGFR kinase inhibitor. FGFR2 fusions and ERRFI mutations may represent novel targets in sporadic intrahepatic cholangiocarcinoma and trials should be characterized in larger cohorts of patients with these aberrations.

Cholangiocarcinoma is a cancer that affects the bile ducts. Unfortunately, many patients diagnosed with cholangiocarcinoma have disease that cannot be treated with surgery or has spread to other parts of the body, thus severely limiting treatment options. New advances in drug treatment have enabled treatment of these cancers with “targeted therapy” that exploits an error in the normal functioning of a tumor cell, compared to other cells in the body, thus allowing only tumor cells to be killed by the drug. We sought to identify changes in the genetic material of cholangiocarcinoma patient tumors in order to identify potential errors in cellular functioning by utilizing cutting edge genetic sequencing technology. We identified three patient tumors possessing an FGFR2 gene that was aberrantly fused to another gene. Two of these patients were able to receive targeted therapy for FGFR2 with resulting tumor shrinkage. A fourth tumor contained an error in a gene that controls a very important cellular mechanism in cancer, termed epidermal growth factor pathway (EGFR). This patient received therapy targeting this mechanism and also demonstrated response to treatment. Thus, we have been able to utilize cutting edge technology with targeted drug treatment to personalize medical treatment for cancer in cholangiocarcinoma patients.

Knocking down low molecular weight protein tyrosine phosphatase (LMW-PTP) reverts chemoresistance through inactivation of Src and Bcr-Abl proteins

The development of multidrug resistance (MDR) limits the efficacy of continuous chemotherapeutic treatment in chronic myelogenous leukemia (CML). Low molecular weight protein tyrosine phosphatase (LMW-PTP) is up-regulated in several cancers and has been associated to poor prognosis. This prompted us to investigate the involvement of LMW-PTP in MDR. In this study, we investigated the role of LMW-PTP in a chemoresistant CML cell line, Lucena-1. Our results showed that LMW-PTP is highly expressed and 7-fold more active in Lucena-1 cells compared to K562 cells, the non-resistant cell line. Knocking down LMW-PTP in Lucena-1 cells reverted chemoresistance to vincristine and imatinib mesylate, followed by a decrease of Src and Bcr-Abl phosphorylation at the activating sites, inactivating both kinases. On the other hand, overexpression of LMW-PTP in K562 cells led to chemoresistance to vincristine. Our findings describe, for the first time, that LMW-PTP cooperates with MDR phenotype, at least in part, through maintaining Src and Bcr-Abl kinases in more active statuses. These findings suggest that inhibition of LMW-PTP may be a useful strategy for the development of therapies for multidrug resistant CML.

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

Myeloid and lymphoid malignancies associated with FGFR1 abnormalities are characterized by constitutive activated FGFR1 kinase and rapid transformation to acute myeloid leukemia and lymphoblastic lymphoma. Molecular targeted therapies have not been widely used for SCLL. Ponatinib (AP24534), that potently inhibits native and mutant BCR-ABL, also targets the fibroblast growth factor receptor (FGFR) family. Using murine BaF3 cells stably transformed with six different FGFR1 fusion genes, as well as human KG1 cells expressing activated chimeric FGFR1 and five newly established murine SCLL cell lines, we show that Ponatinib (< 50 nM) can effectively inhibit phosphoactivation of the fusion kinases and their downstream effectors, such as PLCγ, Stat5 and Src. Ponatinib also significantly extended survival of mice transplanted with different SCLL cell lines. Ponatinib administered at 30 mg/kg daily also significantly delayed, or even prevented, tumorigenesis of KG1 cells in xenotransplanted mice. Furthermore, we demonstrate that Ponatinib specifically inhibits cell growth and clonogenicity of normal human CD34+ progenitor cells transformed by chimeric FGFR1 fusion kinases. Overall, our data provide convincing evidence to suggest that pharmacologic inhibition of FGFR1 fusion kinases with Ponatinib is likely to be beneficial for patients with SCLL and perhaps for other human disorders associated with dysregulated FGFR1 activity.