Tyrosine Kinase Domain Of FGFR1 Research Articles

LGG-19. SLIPPED CAPITAL FEMORAL EPIPHYSIS (SCFE): A RARE ADVERSE EVENT ASSOCIATED WITH FGFR TYROSINE KINASE INHIBITOR THERAPY IN A CHILD

Abstract BACKGROUND FGFR tyrosine kinase inhibitors (FGFR-TKIs) are being increasingly used off-label in children with hard-to-treat tumors harboring specific FGFR alterations. We report a case of Slipped Capital Femoral Epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. METHODS Data was extracted from chart review of the patient and literature search for the use of FGFR-TKIs in children and their side effects. RESULTS A 13-year-old boy was diagnosed to have a optic pathway/ hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-Tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD) and was negative for BRAF mutation/ fusion. Two weeks later, he was treated for a VP shunt infection (surgical revision and 6 weeks antibiotics). He developed hypothalamic obesity with rapid weight gain and BMI >30. After a four-month delay from the initial diagnosis, he was started on erdafitinib a pan-FGFR1-4 inhibitor, through a special access program. At 12 weeks of treatment, he developed persistent knee pain. X-ray of the hips showed slipped capital femoral epiphysis (SCFE) of the right hip. Erdafitinib was discontinued and he underwent surgery with in-situ pinning of the right hip and prophylactic pinning of the left hip. MRI at the time of stopping the medication showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow up. CONCLUSIONS Based on our experience and literature review of pediatric patients who are treated with pan-FGFR TKIs, we recommend: a) monitoring both rate of weight gain/ BMI for obesity and growth velocity while on therapy and b) update the drug toxicity profile of FGFR TKIs to include skeletal toxicities and inform parents/ patients of these toxicities at the time of consent for therapy.

Case report: Slipped capital femoral epiphysis: a rare adverse event associated with FGFR tyrosine kinase inhibitor therapy in a child

We report a case of slipped capital femoral epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. A 13-year-old boy was diagnosed to have an optic pathway/hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD). He developed hypothalamic obesity with rapid weight gain and BMI >30. At 12 weeks of treatment with erdafitinib, he developed persistent knee pain. X-ray of the right hip showed SCFE. Erdafitinib was discontinued, and he underwent surgical pinning of the right hip. MRI at discontinuation of erdafitinib showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow-up. Our experience and literature review suggest that pediatric patients who are treated with pan-FGFR TKIs should be regularly monitored for skeletal side effects.

Abstract 3748: Tyrosine kinase inhibition of fibroblast growth factor receptor 1 in advanced prostate cancer

Abstract Advanced prostate cancer (PCa) is one of the leading causes of cancer death in men in the United States. The FGF/FGFR1 signaling axis has been implicated in the progression of PCa. Different isoforms of FGFR1 have been described in PCa (e.g., alpha and beta), which might account for the typical heterogeneity of PCa. The isoforms may also mediate different clinical responses to treatments targeting this pathway. Pan-FGFR tyrosine kinase inhibitor JNJ-42756493 (Janssen) has been demonstrated to have antiproliferative effects in FGFR pathway-activated cancer cell lines and in vivo mouse antitumor activity. Our goal was to study the effects of JNJ-42756493 in PCa growth and signaling in vitro and establish whether these effects differ according to the FGFR1 isoform (alpha or beta) expressed. Using transfected bone-derived PCa cell lines and patient-derived xenografts (PDXs), we measured the effects of FGFR1 expression on cell proliferation and activation of the FGFR1-pMAPK signaling pathway. We then performed drug treatment experiments on FGFR1-expressing sublines and high-FGFR1 PDXs and observed the response in FGFR1-pMAPK signaling pathway activation. Our results showed that FGFR1 isoforms alpha and beta trigger different biological effects (i.e., proliferation), possibly contributing to the heterogeneity of PCa. We found that targeting the tyrosine kinase domain of FGFR1 with JNJ-42756493 results in pMAPK inhibition in PCa sublines. These findings indicate that the presence of specific FGFR1 variants should be considered for treatment selection in advanced PCa. The results also suggest that FGFR1-pMAPK pathway blockade by JNJ-42756493 should be further studied as a strategy to guide the development of therapies to hinder PCa progression. Citation Format: Louise Medina Bengtsson, Estefania Labanca, Nora Navone. Tyrosine kinase inhibition of fibroblast growth factor receptor 1 in advanced prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3748.

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.

Multiplex ligation-dependent probe amplification analysis is useful for detecting a copy number gain of the FGFR1 tyrosine kinase domain in dysembryoplastic neuroepithelial tumors.

Dysembryoplastic neuroepithelial tumors (DNTs) are slow-growing glioneuronal tumors, and their genetic backgrounds are getting unveiled. Recently, fibroblast growth factor receptor 1 internal tandem duplication (FGFR1-ITD) of the tyrosine kinase domain (TKD) has been demonstrated by whole-genome sequencing. Here, we analyzed 22 DNTs using multiplex ligation-dependent probe amplification (MLPA) with formalin-fixed paraffin-embedded specimens and found a copy number gain in TKD of FGFR1 (13 cases, 59%), which suggested the presence of FGFR1-ITD. Another 5 DNTs harbored FGFR1 hot spot mutations including a double mutant case, and FGFR1 alterations were detected in 18 DNTs (82%). The BRAF V600E mutation, another important mutation in DNTs, was not observed. With recent findings of less frequent or absent FGFR1-ITD in pilocytic astrocytomas or rosette-forming glioneuronal tumors, the analysis of FGFR1 aberrations, especially FGFR1-ITD, was suggested to be helpful to discriminate DNTs from their histological mimics.

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.

Mosaic Activating Mutations in FGFR1 Cause Encephalocraniocutaneous Lipomatosis

Encephalocraniocutaneous lipomatosis (ECCL) is a sporadic condition characterized by ocular, cutaneous, and central nervous system anomalies. Key clinical features include a well-demarcated hairless fatty nevus on the scalp, benign ocular tumors, and central nervous system lipomas. Seizures, spasticity, and intellectual disability can be present, although affected individuals without seizures and with normal intellect have also been reported. Given the patchy and asymmetric nature of the malformations, ECCL has been hypothesized to be due to a post-zygotic, mosaic mutation. Despite phenotypic overlap with several other disorders associated with mutations in the RAS-MAPK and PI3K-AKT pathways, the molecular etiology of ECCL remains unknown. Using exome sequencing of DNA from multiple affected tissues from five unrelated individuals with ECCL, we identified two mosaic mutations, c.1638C>A (p.Asn546Lys) and c.1966A>G (p.Lys656Glu) within the tyrosine kinase domain of FGFR1, in two affected individuals each. These two residues are the most commonly mutated residues in FGFR1 in human cancers and are associated primarily with CNS tumors. Targeted resequencing of FGFR1 in multiple tissues from an independent cohort of individuals with ECCL identified one additional individual with a c.1638C>A (p.Asn546Lys) mutation in FGFR1. Functional studies of ECCL fibroblast cell lines show increased levels of phosphorylated FGFRs and phosphorylated FRS2, a direct substrate of FGFR1, as well as constitutive activation of RAS-MAPK signaling. In addition to identifying the molecular etiology of ECCL, our results support the emerging overlap between mosaic developmental disorders and tumorigenesis.

Abstract 1361: Fragment based drug discovery of selective inhibitors of Fibroblast Growth Factor Receptor (FGFR)

Abstract Recent data in a number of tumour types has implicated Fibroblast Growth Factor (FGF) and Fibroblast Growth Factor receptor (FGFR) signalling as being key to the molecular pathology of cancer. A fragment screening campaign was conducted against the tyrosine kinase domain of FGFR1 to detect low molecular weight compounds that bound to the hinge region of the kinase. The screening produced several fragment inhibitors (molecular weight <250 Da) in the micromolar range and their binding modes were confirmed by X-ray crystallography. We selected an imidazo[1,2-a]pyridine fragment that was 120 uM versus FGFR3 in the kinase inhibition bioassay. Subsequently, in the fragments-to-leads stage a detailed structural understanding of the binding interactions between the fragment and its protein kinase target, using X-ray crystallography, led to the identification of a 0.003 uM inhibitor of FGFR3 in the kinase bioassay, with significant selectivity versus VEGFR2 and FLT3. The poster will focus on the description of previously undescribed compounds bearing an imidazo[1,2-a]pyridine core scaffold where selectivity versus other protein kinases, for example FLT3, is obtained using the X-ray crystal structure and structure-based design. In summary we will illustrate how X-ray crystallography and fragment-based drug design (FBDD) can be used to discover compounds with activity in an FGFR driven xenograft model when dosed by the oral route. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1361. doi:10.1158/1538-7445.AM2011-1361

Structure of Lipid Kinase p110β/p85β Elucidates an Unusual SH2-Domain-Mediated Inhibitory Mechanism

SummaryPhosphoinositide 3-kinases (PI3Ks) are essential for cell growth, migration, and survival. The structure of a p110β/p85β complex identifies an inhibitory function for the C-terminal SH2 domain (cSH2) of the p85 regulatory subunit. Mutagenesis of a cSH2 contact residue activates downstream signaling in cells. This inhibitory contact ties up the C-terminal region of the p110β catalytic subunit, which is essential for lipid kinase activity. In vitro, p110β basal activity is tightly restrained by contacts with three p85 domains: the cSH2, nSH2, and iSH2. RTK phosphopeptides relieve inhibition by nSH2 and cSH2 using completely different mechanisms. The binding site for the RTK's pYXXM motif is exposed on the cSH2, requiring an extended RTK motif to reach and disrupt the inhibitory contact with p110β. This contrasts with the nSH2 where the pY-binding site itself forms the inhibitory contact. This establishes an unusual mechanism by which p85 SH2 domains contribute to RTK signaling specificities.

The Selectivity of Receptor Tyrosine Kinase Signaling Is Controlled by a Secondary SH2 Domain Binding Site

SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. However, the modest binding affinity of SH2 domains to pY containing peptides may not account for and likely represents an oversimplified mechanism for regulation of selectivity of signaling pathways in living cells. Here we describe the crystal structure of the activated tyrosine kinase domain of FGFR1 in complex with a phospholipase Cgamma fragment. The structural and biochemical data and experiments with cultured cells show that the selectivity of phospholipase Cgamma binding and signaling via activated FGFR1 are determined by interactions between a secondary binding site on an SH2 domain and a region in FGFR1 kinase domain in a phosphorylation independent manner. These experiments reveal a mechanism for how SH2 domain selectivity is regulated in vivo to mediate a specific cellular process.

Identification of four new translocations involving FGFR1 in myeloid disorders

The 8p11 myeloproliferative syndrome (EMS) is associated with three translocations, t(8;13)(p11;q12), t(8;9)(p11;q33), and t(6;8)(q27;p11), that fuse unrelated genes (ZNF198, CEP110, and FOP, respectively) to the entire tyrosine kinase domain of FGFR1. In all cases thus far examined (n = 10), the t(8;13) results in an identical mRNA fusion between ZNF198 exon 17 and FGFR1 exon 9. To determine if consistent fusions are also seen in the variant translocations, we performed RT-PCR on four cases and sequenced the products. For two patients with a t(8;9), we found that CEP110 exon 15 was fused to FGFR1 exon 9. For two patients with a t(6;8), we found that FOP exon 5 (n = 1) or exon 7 (n = 1) was fused to FGFR1 exon 9. To determine if FGFR1 might be involved in other myeloid disorders with translocations of 8p, we developed a two-color FISH assay using two differentially labeled PAC clones that flank FGFR1. Disruption of this gene was indicated in a patient with a t(8;17)(p11;q25) and Ph-negative chronic myeloid leukemia in association with systemic malignant mast cell disease, a patient with acute myeloid leukemia with a t(8;11)(p11;p15), and two cases with T-cell lymphoma, myeloproliferative disorder, and marrow eosinophilia with a t(8;12)(p11;q15) and ins(12;8)(p11;p11p21), respectively. For the patient with the t(8;11), the chromosome 11 breakpoint was determined to be in the vicinity of NUP98. We conclude that 1) all mRNA fusions in EMS result in splicing to FGFR1 exon 9 but breakpoints in FOP are variable, 2) two-color FISH can identify patients with EMS, and 3) the t(8;17)(p11;q25), t(8;11)(p11;p15), t(8;12)(p11;q15), and ins(12;8)(p11;p11p21) are novel karyotypic changes that most likely involve FGFR1.

Crystal structure of an angiogenesis inhibitor bound to the FGF receptor tyrosine kinase domain.

Angiogenesis, the sprouting of new blood vessels from pre-existing ones, is an essential physiological process in development, yet also plays a major role in the progression of human diseases such as diabetic retinopathy, atherosclerosis and cancer. The effects of the most potent angiogenic factors, vascular endothelial growth factor (VEGF), angiopoietin and fibroblast growth factor (FGF) are mediated through cell surface receptors that possess intrinsic protein tyrosine kinase activity. In this report, we describe a synthetic compound of the pyrido[2,3-d]pyrimidine class, designated PD 173074, that selectively inhibits the tyrosine kinase activities of the FGF and VEGF receptors. We show that systemic administration of PD 173074 in mice can effectively block angiogenesis induced by either FGF or VEGF with no apparent toxicity. To elucidate the determinants of selectivity, we have determined the crystal structure of PD 173074 in complex with the tyrosine kinase domain of FGF receptor 1 at 2.5 A resolution. A high degree of surface complementarity between PD 173074 and the hydrophobic, ATP-binding pocket of FGF receptor 1 underlies the potency and selectivity of this inhibitor. PD 173074 is thus a promising candidate for a therapeutic angiogenesis inhibitor to be used in the treatment of cancer and other diseases whose progression is dependent upon new blood vessel formation.

The t(8;13)(p11;q11-12) rearrangement associated with an atypical myeloproliferative disorder fuses the fibroblast growth factor receptor 1 gene to a novel gene RAMP.

A recently described atypical myeloproliferative disorder is invariably associated with reciprocal translocations involving 8p11-12. The most common rearrangement is a t(8;13)(p11;q11-12). Here we determine that this translocation results in the fusion of the fibroblast growth factor receptor 1 gene (FGFR1), a member of the receptor tyrosine kinase family at 8p11, to a novel gene at 13q11-12 designated RAMP . The predicted RAMP protein exhibits strong homology to the product of a recently cloned candidate gene for X-linked mental retardation, DXS6673E . We also provide the first report of a novel, putative metal-binding motif, present as five tandem repeats in both RAMP and DXS6673E. RT-PCR detected only one of the two possible fusion transcripts, encoding a product in which the N-terminal 641 amino acids of RAMP become joined to the tyrosine kinase domain of FGFR1. Receptor tyrosine kinases are not commonly involved in the formation of tumour-specific fusion proteins. However, the previous reports of involvement of receptor tyrosine kinases in fusion proteins in non-Hodgkin's lymphoma, chronic myelomonocytic leukaemia and papillary thyroid carcinoma described similar rearrangements. By analogy with these, we propose that the RAMP-FGFR1 fusion product will contribute to progression of this myeloproliferative disorder by constitutive activation of tyrosine kinase function.

Fibroblast growth factor-2 (FGF-2) is present in maternal and cord serum, and in the mother is associated with a binding protein immunologically related to the FGF receptor-1.

Fibroblast growth factor-2 (FGF-2) is expressed in human fetal tissues and placenta. We, therefore, determined whether FGF-2 appeared in either fetal or maternal circulations during normal pregnancies [fetuses appropriate for gestational age (AGA)] or those complicated by fetal growth restriction (small for gestational age). Cordocentesis was performed, and matched maternal blood was collected between 19-39 weeks gestation, whereas maternal and cord blood and amniotic fluid (AF) were collected at term. FGF-2 was extracted from maternal serum (MS), cord serum (CS), and AF by heparin-Sepharose affinity chromatography and subjected to Western blot analysis or quantified by specific RIA. Western blot analysis of MS, CS, and AF revealed, in each case, a single immunoreactive FGF-2 species of 18 kilodaltons (kDa), although this was not present in nonpregnant serum. In AGA pregnancies, immunoreactive FGF-2 was present in MS from at least 18 weeks gestation and rose to maximum values at the end of second trimester (weeks 28-31; mean +/- SEM, 342 +/- 62 pmol/L), but by term had declined (weeks 40-42; 104 +/- 24 pmol/L). In CS, FGF-2 immunoreactivity was highest at weeks 18-20 of gestation (662 +/- 144 pmol/L), but thereafter, slowly declined to term (weeks 40-42; 119 +/- 28 pmol/L). Immunoreactive FGF-2 levels in MS and CS of small for gestational age pregnancies in the second trimester tended to be lower than those in AGA pregnancies, but differences were not statistically significant. AF also contained immunoreactive FGF-2 at term (91 +/- 35 pmol/L). Neutral gel chromatography on Sephadex G-200 revealed that FGF-2 immunoreactivity eluted as a broad peak with an apparent molecular size of 55-160 kDa. These same fractions contained peptides of 55-60, 90-95, and 120-130 kDa, which were recognized by antisera against the extracellular domain of the high affinity FGF receptor, FGFR1, after Western blot. Ligand blot analysis of the same nitrocellulose filters using 125I-labeled FGF-2 revealed that the 55- to 60-kDa species specifically bound FGF-2. This binding species was not recognized during Western blot analysis using an antiserum raised against the intracellular tyrosine kinase domain of FGFR1, suggesting that it represents a truncated receptor form. Similar FGFR1 immunoreactive species were present in nonpregnant female and male sera, but were barely detectable in term CS or AF.(ABSTRACT TRUNCATED AT 400 WORDS)