Activation Of Fibroblast Growth Factor Receptor Research Articles

Abstract 992: IL-6/STAT3-mediated inflammatory signaling results in dysregulated fibroblast growth factor receptor activation and tumor cell signaling in human pancreatic adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy characterized by delayed diagnosis and the lowest five-year survival amongst all cancer sites. PDAC development and progression are attributed to chronic inflammation and associated tissue repair mechanisms which contribute to high density tumor formation and chemoresistance. PDAC-associated inflammation is, in part, owed to high levels of interleukin 6 (IL-6) and its activated pathways including JAK/STAT3. In Addition, Fibroblast growth factor (FGF) signaling pathways are known to be dysregulated in cancer and have been implicated in various malignancies including PDAC. As such, we sought to explore the association between IL-6-induced inflammatory signaling and FGF signaling activation. To observe this effect as it pertains to carcinogenesis and cancer progression we used four human cell lines ranging from healthy pancreatic ductal epithelial (HPDE) cells to various grade (G) PDAC cells. Cells were treated with IL-6 at a concentration of 100 ng/mL for 24 hours. The results showed increased phosphorylation of STAT3 in BxPC-3 (G2) and PANC-1 (G3) cells with no change noted in HPDE and SW1990 (G2, metastatic) cells. IL-6 stimulation likewise resulted in markedly increased phosphorylation of the fibroblast growth factor receptor substrate 2-alpha (FRS2-α) and its downstream component Erk1/2 in BxPC3 cells, indicating activation of FGF signaling through the MAPK/Erk pathway in our low grade PDAC cell model. In conclusion, the results demonstrate a potential link between IL-6 induced inflammatory signaling and dysregulation of FGF signaling in human PDAC. Activated STAT3 signaling seems to be involved in this process. Existing cancer therapies aimed at controlling growth factor signaling broadly target vascular endothelial or epithelial growth factor receptors (VEGF/EGFR) with marginal efficacy and adverse side effects in PDAC. Identifying the pivotal link between inflammatory signaling and dysregulation of fibroblast growth factor signaling will allow for the development of more precisely targeted and effective cancer therapy in pancreatic cancer. This may minimize clinically observed exaggerated fibrotic events within the tumor and may hence result in higher vulnerability for established chemotoxic therapies in the tumor cells. Citation Format: Karol Nawalaniec, Yuxiang Wang, Romana Moench, Minghua Cao, Yueming Luo, Li-Li Hsiao, Ana Maria Waaga-Gasser. IL-6/STAT3-mediated inflammatory signaling results in dysregulated fibroblast growth factor receptor activation and tumor cell signaling in human pancreatic adenocarcinoma [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 992.

Novel therapeutic approaches for the treatment of achondroplasia.

Achondroplasia is the most common form of human dwarfism. The molecular basis of achondroplasia was elucidated in 1994 with the identification of the fibroblast growth factor receptor 3 (FGFR3) as the causative gene. Missense mutations causing achondroplasia result in activation of FGFR3 and its downstream signaling pathways, disturbing chondrogenesis, osteogenesis, and long bone elongation. A more accurate understanding of the clinical and molecular aspects of achondroplasia has allowed new therapeutic approaches to be developed. These are based on: clear understanding of the natural history of the disease; proof-of-concept preclinical studies in mouse models; and the current state of knowledge regarding FGFR3 and related growth plate homeostatic pathways. This review provides a brief overview of the preclinical mouse models of achondroplasia that have led to new, non-surgical therapeutic strategies being assessed and applied to children with achondroplasia through pioneering clinical trials.

HSP90 overexpression potentiates the B-cell receptor and fibroblast growth factor receptor survival signals in chronic lymphocytic leukemia cells.

Chronic lymphocytic leukemia (CLL) is still an incurable disease despite aggressive chemotherapies including the B-cell receptor (BCR) targeted-inhibitors. Therefore, we assessed the expression status of key signal mediators of the BCR pathway in CLL cells. Indeed, we detected aberrantly elevated levels of CD79a, B-cell adaptor for PI3K (BCAP) and phospholipase C (PLC)γ2, key mediators of BCR signal, in CLL cells. As HSP90 is also overexpressed in CLL cells, we hypothesized that HSP90 could potentiate the BCR signal via stabilization of multiple key components of the BCR-signalosome. We found that HSP90 formed a multi-molecular complex with CD79a, BCAP, PLCγ2, LYN, SYK, Bruton tyrosine kinase (BTK) and AKT and that, pharmacologic inhibition or partial depletion of HSP90 reduced the expression of these signal mediators in CLL cells. In addition, our findings also demonstrated that HSP90 could stabilize the tyrosine phosphatase, PTPN22 which positively regulates AKT phosphorylation, and the constitutively active fibroblast growth factor receptor 3 (FGFR3) in CLL cells. Finally, HSP90 inhibition induced apoptosis in CLL cells in a dose-dependent manner likely via downregulation of anti-apoptotic proteins MCL-1 and XIAP, but not BCL2, reported to be overexpressed in CLL cells. In total, our findings suggest that HSP90-inhibition may sensitize the leukemic B-cells to BCR-targeted agents, particularly those become resistant to these therapies.

89-OR: FGFR1/MAPKs/AP-1 Signaling Mediates Cardiomyopathy in Streptozotocin-Induced Type 1 Diabetes

Diabetic cardiomyopathy is a complex entity associated with multiple contributing mechanisms and consequent manifestations in the clinic. Emerging evidence implicates that increased activity of fibroblast growth factor receptor 1 (FGFR1) is required during induced cardiac damage and remodeling. However, little is known about the roles of FGFR1 on diabetic cardiomyopathy (DCM). We hypothesized that the high-concentration glucose (HG)/diabetes induced cardiac pathophysiological and malfunctional alterations are linked to the activation of FGFR1. We tested this hypothesis by challenging cultured cardiomyocytes with high-concentration glucose and myocardium of streptozotocin (STZ)-induced type 1 diabetic mice (T1D). This study indicated that FGFR1 phosphorylation was increased in myocardium of streptozotocin (STZ)-induced type 1 diabetic mice (T1D) and cultured cardiomyocytes to high-concentration glucose. The inactivation of FGFR1 by selective inhibitors AZD4547, neutralized the increased FGFR1 phosphorylation and significantly reduced myocardial structural and functional deficits in type 1 diabetic mice. In vitro, overexpression of FGFR1 by lentivirus-transfection aggravated HG-induced fibrosis and hypertrophy in cardiomyocytes. Blocking FGFR1 by AZD4547 or CRISPER-Cas9 knockout, HG-induced fibrosis and hypertrophy in cardiomyocytes were significantly decreased. Then, GSEA analysis of RNA-sequencing implied that collagen5a1(Col5a1) and periostin (Postn) were associated with fibrosis and myosin heavy chain 4/7/8/9 (Myh4/7/8/9) were associated with hypertrophy. Analysis by PASTAA database and confirmatory tests by inhibiting FGFR1 or MAPKs indicated that MAPKs/AP-1 plays a crucial role in FGkFR1-mediated cardiomyocyte injuries challenged by HG. These results reveal an unrecognized FGFR1/MAPKs/AP-1 signaling axis involved in the development and progression of DCM and suggest that AZD4547 might be a potential agent for treating DCM. Disclosure X. Chen: None. Y. Wang: None. F. Shen: None. Funding National Natural Science Foundation of China (81700335)

The relationship between leptin, leptin receptor, and FGFR1 in primary human breast tumors.

e13578 Background: General/overall obesity and visceral/central obesity are associated with increased breast cancer risk and poorer cancer outcomes; however, the precise etiology of these observations is not fully known. Our previous research suggests that adipose tissue-derived fibroblast growth factor 2 (FGF2) promotes malignant transformation of mammary epithelial cells through the activation of its primary receptor, fibroblast growth factor receptor 1 (FGFR1). Both FGF2 and leptin have been shown to be elevated in the serum in obesity (body mass index (BMI) > 25kg/m2). It is well established that elevated sera leptin promotes breast cancer through multiple mechanisms. Therefore, we hypothesized that tumors that express elevated FGFR1 and leptin receptor (LepR) may have a poorer prognosis in obese patients. Methods: Databases that house gene-sequenced breast cancer tumors and normal breast tissue were analyzed to discern relationships between gene copy number and mRNA levels of leptin, leptin receptor, FGFR1 and janus kinase 2 (Jak2), as Jak2 was shown to be a common downstream mediator of both FGFR1 and leptin receptor activation by Cytoscape network analysis. Furthermore, we tested the efficacy of Jak2 inhibitors for preventing mammary epithelial cell malignant transformation using our well-established models of adipose tissue-stimulated growth in soft agar. The anchorage-independent growth in soft agar is a surrogate marker for malignant transformation. Results: A much stronger significant relationship exists between FGFR1 mRNA and leptin mRNA in primary breast cancer (p = 3.17*10−9) compared with normal breast epithelium (p = 0.0013). In primary breast tumors, gene copy number of FGFR1 positively correlates with leptin copy number (p = 8.956*10−8, r = 0.19). Moreover, two separate Jak2 inhibitors attenuated both leptin+FGF2-stimulated and mouse adipose tissue-stimulated MCF-10A cell transformation. Conclusions: Taken together, these results suggest that elevated sera FGF2 and leptin in obese patients may promote breast tumorigenesis in tumors that express elevated FGFR1 and LepR and that Jak2 inhibitors may be a novel therapeutic option for adiposity-driven breast cancers. Future work will examine the relationship between FGFR1/leptin receptor expression and survival and how these relationships are influenced by BMI status.

Can Patients with Muscle-invasive Bladder Cancer and Fibroblast Growth Factor Receptor-3 Alterations Still Be Considered for Neoadjuvant Pembrolizumab? A Comprehensive Assessment from the Updated Results of the PURE-01 Study

In the PURE-01 study, patients with muscle-invasive bladder cancer (MIBC) who achieved a pathological complete response (CR; ypT0N0) had tumor features suggesting that pre-existing immunity may promote response. We focused on fibroblast growth factor receptor-3 (FGFR3) genomic alterations (GAs) as potential tumor resistance features. The primary endpoint of our study was CR. FGFR3 GAs were assessed via comprehensive genomic profiling of sequenced DNA (N = 112), a transcriptome-based FGFR3 activity signature, an FGFR3 subtyping model based on long noncoding RNA (lncRNA), and gene expression profiling (N = 84 for all three). We used Wilcoxon rank-sum tests, Fisher’s exact test, and logistic regression analyses to analyze the associations between the various FGFR3 alterations and CR. High FGFR3 activity was defined as a signature score that was higher than the median value. Cases that were positive for lncRNA-FGFR3 subtype (lncRNA-FGFR3 active, N = 11) had consistent biology with published data: low epithelial-mesenchymal transition and immune-signature scores, high p53 activity, FGFR3 activity, and sonic hedgehog activity. In total, 17 (15.2%), 42 (50%), and 11 patients (13%) showed FGFR3 GAs or high FGFR3 signature scores, or had lncRNA-FGFR3–active tumors. Despite an association of high FGFR3 gene expression with a lower CR rate (p = 0.01), we did not find a correlation between FGFR3 activity or mutation/fusion and CR (p = 0.2 and p = 0.8). We conclude that the association of FGFR3 expression with pathological response is balanced by multiple factors. Overall, FGFR3-altered tumors should not be excluded from neoadjuvant immunotherapy studies at this time. Patient summaryIn patients with muscle-invasive bladder cancer treated within the PURE-01 trial, we analyzed the role of fibroblast growth factor receptor-3 (FGFR3) alterations, at the DNA and RNA levels, in association with the pathological response. We did not find any robust association, mainly when analyzing the landscape of alterations defining tumors with higher biological FGFR activity. Overall, FGFR3 activity and gene alterations did not provide sufficiently robust data to exclude patients whose tumors harbor these alterations from neoadjuvant immunotherapy trials.

Imaging the fibroblast growth factor receptor network on the plasma membrane with DNA-assisted single-molecule super-resolution microscopy.

Fibroblast growth factor receptors (FGFRs) are a subfamily of receptor tyrosine kinases and central players in health and disease. Following ligand binding and the formation of homo- and heteromeric complexes, FGFRs initiate a cellular response. Challenges in studying FGFR activation are inner-subfamily interactions and a complex heterogeneity of these in the cell membrane, which demand for observation techniques that can resolve individual protein complexes and that are compatible with endogenous protein levels. Here, we established an imaging and analysis pipeline for multiplexed single-molecule localization microscopy (SMLM) of the FGFR network at the plasma membrane. Using DNA-labeled primary antibodies, we visualize all four FGFRs in the same cell with near-molecular spatial resolution. From the super-resolution imaging data, we extract information on FGFR density, spatial distribution, and inner-subfamily colocalization. Our approach is straightforward and easily adaptable to other multiplexed SMLM data of membrane proteins.

A Generalizable Optogenetic Strategy to Regulate Receptor Tyrosine Kinases during Vertebrate Embryonic Development

Ligand-independent activation of receptor tyrosine kinases (RTKs) allows for dissecting out the receptor-specific signaling outcomes from the pleiotropic effects of the ligands. In this regard, RTK intracellular domains (ICD) are of interest due to their ability to recapitulate signaling activity in a ligand-independent manner when fused to chemical or optical dimerizing domains. A common strategy for synthetic activation of RTKs involves membrane tethering of dimerizer–RTK ICD fusions. Depending on the intrinsic signaling capacity, however, this approach could entail undesirable baseline signaling activity in the absence of stimulus, thereby diminishing the system's sensitivity. Here, we observed toxicity in early Xenopus laevis embryos when using such a conventional optogenetic design for the fibroblast growth factor receptor (FGFR). To surpass this challenge, we developed a cytoplasm-to-membrane translocation approach, where FGFR ICD is recruited from the cytoplasm to the plasma membrane by light, followed by its subsequent activation via homo-association. This strategy results in the optical activation of FGFR with low background activity and high sensitivity, which allows for the light-mediated formation of ectopic tail-like structures in developing X. laevis embryos. We further generalized this strategy by developing optogenetic platforms to control three neurotrophic tropomyosin receptor kinases, TrkA, TrkB, and TrkC. We envision that these ligand-independent optogenetic RTKs will provide useful toolsets for the delineation of signaling sub-circuits in developing vertebrate embryos.

New developments in the management of achondroplasia

SummaryAchondroplasia is the most common form of disproportionate short stature. A dominantly inherited FGFR3 mutation permanently activates the fibroblast growth factor receptor 3 (FGFR3) and its downstream mitogen-activated protein kinase (MAPK) signalling pathway. This inhibits chondrocyte differentiation and puts a break on growth plate function, in addition to causing serious medical complications such as foramen magnum and spinal stenosis and upper airway narrowing. A great deal has been learned about complications and consequences of FGFR3 activation and management guidance is evolving aimed to reduce the increased mortality and morbidity in this condition, particularly deaths from spinal cord compression and sleep apnoea in infants and small children. To date, no drugs are licensed for treatment of achondroplasia. Here, we report on the various substances in the drug development pipeline which target elements in molecular disease mechanism such as FGF (fibroblast growth factor) ligands, FGFR3, MAPK signalling as well as the C‑type natriuretic peptide receptor NPR‑B (natriuretic peptide receptor B).

FGF21 Attenuated LPS-Induced Depressive-Like Behavior via Inhibiting the Inflammatory Pathway.

Major depressive disorder is a serious neuropsychiatric disorder with high rates of recurrence and mortality. Many studies have supported that inflammatory processes play a central role in the etiology of depression. Fibroblast growth factor 21 (FGF21), a member of the fibroblast growth factors (FGFs) family, regulates a variety of pharmacological activities, including energy metabolism, glucose and lipid metabolism, and insulin sensitivity. In addition, recent studies showed that the administration of FGF21, a regulator of metabolic function, had therapeutic effects on mood stabilizers, indicating that FGF21 could be a common regulator of the mood response. However, few studies have highlighted the antidepressant effects of FGF21 on lipopolysaccharide (LPS)-induced mice, and the anti-inflammatory mechanism of FGF21 in depression has not yet been elucidated. The purpose of the current study was to determine the antidepressant effects of recombinant human FGF21 (rhFGF21). The effects of rhFGF21 on depression-like behaviors and the inflammatory signaling pathway were investigated in both an LPS-induced mouse model and primary microglia in vitro. The current study demonstrated that LPS induced depressive-like behaviors, upregulated proinflammatory cytokines, and activated microglia in the mouse hippocampus and activated the inflammatory response in primary microglia, while pretreatment with rhFGF21 markedly improved depression-like behavior deficits, as shown by an increase in the total distance traveled and number of standing numbers in the open field test (OFT) and a decrease in the duration of immobility in the tail suspension test (TST) and forced swimming test (FST). Furthermore, rhFGF21 obviously suppressed expression levels of the proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) and inhibited microglial activation and the nuclear factor-κB (NF-κB) signing pathway. Moreover, coadministration of rhFGF21 with the fibroblast growth factor receptor 1 (FGFR1) inhibitor PD173074 significantly reversed these protective effects, indicating that the antidepressant effects of rhFGF21 occur through FGFR1 activation. Taken together, the results of the current study demonstrated for the first time that exogenous rhFGF21 ameliorated LPS-induced depressive-like behavior by inhibiting microglial expression of proinflammatory cytokines through NF-κB suppression. This new discovery suggests rhFGF21 as a new therapeutic candidate for depression treatment.

Fibroblast growth factor signaling in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis: Paving the way to hepatocellular carcinoma.

Metabolic disorders are increasingly leading to non-alcoholic fatty liver disease, subsequent steatohepatitis, cirrhosis and hepatocellular carcinoma. Fibroblast growth factors and their receptors play an important role in maintaining metabolic homeostasis also in the liver and disorders in signaling have been identified to contribute to those pathophysiologic conditions leading to hepatic lipid accumulation and chronic inflammation. While specific and well tolerated inhibitors of fibroblast growth factor receptor activity are currently developed for (non-liver) cancer therapy, treatment of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis is still limited. Fibroblast growth factor-mimicking or restoring approaches have recently evolved as a novel therapeutic option and the impact of such interactions with the fibroblast growth factor receptor signaling network during non-alcoholic fatty liver disease/non-alcoholic steatohepatitis development is reviewed here.

Crosstalk between SHH and FGFR Signaling Pathways Controls Tissue Invasion in Medulloblastoma.

In the Sonic Hedgehog (SHH) subgroup of medulloblastoma (MB), tumor initiation and progression are in part driven by smoothened (SMO) and fibroblast growth factor (FGF)-receptor (FGFR) signaling, respectively. We investigated the impact of the SMO-FGFR crosstalk on tumor growth and invasiveness in MB. We found that FGFR signaling represses GLI1 expression downstream of activated SMO in the SHH MB line DAOY and induces MKI67, HES1, and BMI1 in DAOY and in the group 3 MB line HD-MBO3. FGFR repression of GLI1 does not affect proliferation or viability, whereas inhibition of FGFR is necessary to release SMO-driven invasiveness. Conversely, SMO activation represses FGFR-driven sustained activation of nuclear ERK. Parallel activation of FGFR and SMO in ex vivo tumor cell-cerebellum slice co-cultures reduced invasion of tumor cells without affecting proliferation. In contrast, treatment of the cells with the SMO antagonist Sonidegib (LDE225) blocked invasion and proliferation in cerebellar slices. Thus, sustained, low-level SMO activation is necessary for proliferation and tissue invasion, whereas acute, pronounced activation of SMO can repress FGFR-driven invasiveness. This suggests that the tumor cell response is dependent on the relative local abundance of the two factors and indicates a paradigm of microenvironmental control of invasion in SHH MB through mutual control of SHH and FGFR signaling.

The cardenolides ouabain and reevesioside A promote FGF2 secretion and subsequent FGFR1 phosphorylation via converged ERK1/2 activation

Na+/K+-ATPase α1 was reported to directly interact with and recruit FGF2 (fibroblast growth factor 2), a vital cell signaling protein implicated in angiogenesis, to the inner plasma membrane for subsequent secretion. Cardenolides, a class of cardiac glycosides, were reported to downregulate FGF2 secretion upon binding to Na+/K+-ATPase α1 in a cell system with ectopically expressed FGF2 and Na+/K+-ATPase α1. Herein, we disclose that the cardenolides ouabain and reevesioside A significantly enhance the secretion/release of FGF2 and the phosphorylation of FGFR1 (fibroblast growth factor receptor 1) in a time- and dose-dependent manner, in A549 carcinoma cells. A pharmacological approach was used to elucidate the pertinent upstream effectors. Only the ERK1/2 inhibitor U0126 but not the other inhibitors examined (including those inhibiting the unconventional secretion of FGF2) was able to reduce ouabain-induced FGF2 secretion and FGFR1 activation. ERK1/2 phosphorylation was increased upon ouabain treatment, a process found to be mediated through upstream effectors including ouabain-induced phosphorylated EGFR and a reduced MKP1 protein level. Therefore, at least two independent lines of upstream effectors are able to mediate ouabain-induced ERK1/2 phosphorylation and the subsequent FGF2 secretion and FGFR1 activation. These finding constitute unprecedent insights into the regulation of FGF2 secretion by cardenolides.

Role of the N-Terminal Transmembrane Helix Contacts in the Activation of FGFR3.

Fibroblast growth factor receptor 3 (FGFR3) is a member of receptor tyrosine kinases, which is involved in skeletal cell growth, differentiation, and migration. FGFR3 transduces biochemical signals from the extracellular ligand-binding domain to the intracellular kinase domain through the conformational changes of the transmembrane (TM) helix dimer. Here, we apply generalized replica exchange with solute tempering method to wild type (WT) and G380R mutant (G380R) of FGFR3. The dimer interface in G380R is different from WT and the simulation results are in good agreement with the solid-state nuclear magnetic resonance (NMR) spectroscopy. TM helices in G380R are extended more than WT, and thereby, G375 in G380R contacts near the N-termini of the TM helix dimer. Considering that both G380R and G375C show the constitutive activation, the formation of the N-terminal contacts of the TM helices can be generally important for the activation mechanism. © 2019 Wiley Periodicals, Inc.

Abstract A077: FIGHT-207: Phase 2 study of pemigatinib in patients with previously treated, locally advanced/metastatic or unresectable solid tumor malignancies harboring activating fibroblast growth factor receptor (FGFR) gene alterations

Abstract Introduction: Activating mutations, rearrangements, and amplifications of FGFR, resulting in either ligand-independent or aberrant ligand-dependent FGFR signaling have been identified in many tumor types. A recent large-scale sequencing study across tumor types identified FGFR alterations in 7.1% of cancers, including gene amplification (66%), mutations (26%), and rearrangements (8%) (Helsten CCR 2016). Pemigatinib (INCB054828) is a selective, potent, oral inhibitor of FGFR1–3 that has demonstrated antitumor activity in FGFR-driven tumors in phase 1/2 (FIGHT-101) and phase 2 (FIGHT-201, -202, and -203) studies. FIGHT-207 is a phase 2, open-label, single-arm, tumor-agnostic study that will evaluate the efficacy and safety of pemigatinib monotherapy in patients with advanced/metastatic or surgically unresectable solid tumor malignancies with activating FGFR mutations, fusions or rearrangements (NCT03822117). Methods: Eligible patients (aged ≥18 years) have histologically or cytologically confirmed solid tumor malignancy that is advanced/metastatic or is surgically unresectable; radiographically measurable disease (per Response Evaluation Criteria in Solid Tumors version 1.1 [RECIST v1.1] or Response Assessment in Neuro-Oncology [RANO] for primary brain tumors); documented FGFR1–3 mutation or translocation; objective progression after at least 1 prior therapy, and no therapy available that is likely to provide clinical benefit; Eastern Cooperative Oncology Group performance status 0 to 2; and no prior receipt of a selective FGFR inhibitor. Patients are assigned to 1 of 3 cohorts based on FGFR status: Cohort A (n ~ 60): FGFR1–3 in-frame fusions or FGFR2 intron 17 rearrangements; Cohort B (n ~ 90): known/predicted activating point mutations in FGFR1–3; and Cohort C (n ~ 20): any FGFR1–3 point mutations in the kinase domain, variants of unknown significance or FGFR1/FGFR3 rearrangements without an identified partner gene. All patients receive a starting dose of pemigatinib 13.5 mg once daily on a 21-day cycle. Patients with no grade ≥2 treatment-related adverse events and no hyperphosphatemia (serum phosphate >5.5 mg/dL) during cycle 1 are allowed to increase dose to pemigatinib 18 mg from cycle 2. Treatment continues as long as patients are receiving benefit or until treatment withdrawal criteria are met. Hyperphosphatemia is managed with diet modifications, phosphate binders, and diuretics, or pemigatinib dose reduction/interruption. The primary endpoint is objective response rate (assessed by independent review committee [IRC] per RECIST v1.1 or RANO) in Cohorts A and B. Secondary endpoints are progression-free survival, duration of response, and overall survival in Cohorts A and B; safety and tolerability in all cohorts. Biopsies will be obtained for select tumors at screening, on-treatment, and at end of treatment. Additional biomarkers that may be indicative of clinical response, resistance, and safety may also be investigated. The study is currently recruiting. Citation Format: Luis Féliz, Ekaterine Asatiani, Christine Lihou, Huiling Zhen, Ian Silverman, Jordi Rodon Ahnert. FIGHT-207: Phase 2 study of pemigatinib in patients with previously treated, locally advanced/metastatic or unresectable solid tumor malignancies harboring activating fibroblast growth factor receptor (FGFR) gene alterations [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A077. doi:10.1158/1535-7163.TARG-19-A077

Adaptive Resistance to Dual BRAF/MEK Inhibition in BRAF-Driven Tumors through Autocrine FGFR Pathway Activation.

Combined MAPK pathway inhibition using dual BRAF and MEK inhibitors has prolonged the duration of clinical response in patients with BRAFV600E-driven tumors compared with either agent alone. However, resistance frequently arises. We generated cell lines resistant to dual BRAF/MEK inhibition and utilized a pharmacologic synthetic lethal approach to identify a novel, adaptive resistance mechanism mediated through the fibroblast growth factor receptor (FGFR) pathway. In response to drug treatment, transcriptional upregulation of FGF1 results in autocrine activation of FGFR, which potentiates extracellular signal-regulated kinases (ERK) activation. FGFR inhibition overcomes resistance to dual BRAF/MEK inhibitors in both cell lines and patient-derived xenograft (PDX) models. Abrogation of this bypass mechanism in the first-line setting enhances tumor killing and prevents the emergence of drug-resistant cells. Moreover, clinical data implicate serum FGF1 levels in disease prognosis. Taken together, these results describe a new, adaptive resistance mechanism that is more commonly observed in the context of dual BRAF/MEK blockade as opposed to single-agent treatment and reveal the potential clinical utility of FGFR-targeting agents in combination with BRAF and MEK inhibitors as a promising strategy to forestall resistance in a subset of BRAF-driven cancers.

Basic Fibroblast Growth Factor Reduces Permeability and Apoptosis of Human Brain Microvascular Endothelial Cells in Response to Oxygen and Glucose Deprivation Followed by Reoxygenation via the Fibroblast Growth Factor Receptor 1 (FGFR1)/ERK Pathway.

BackgroundDisruption of the blood–brain barrier (BBB) is a mechanism in the pathogenesis of traumatic brain injury. Basic fibroblast growth factor (bFGF) is expressed in angiogenesis, neurogenesis, and neuronal survival. This study aimed to investigate the role of bFGF in vitro in human brain microvascular endothelial cells (HBMECs) challenged by oxygen-glucose deprivation/reperfusion (OGD/R).Material/MethodsHBMECs were cultured in glucose-free medium and an environment with <0.5% oxygen in an anaerobic chamber. Immunocytochemistry, Western blot, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were used to measure the protein and mRNA expression levels of bFGF, tight junction, adherens junction, apoptotic proteins, and matrix metalloproteinases (MMPs). The effects of bFGF on the viability of HBMECs was evaluated using the cell counting kit-8 (CCK-8) assay. Cell apoptosis was evaluated using the TUNEL assay, and endothelial permeability was quantified using a transwell migration assay with fluorescein isothiocyanate (FITC) conjugated with dextran. The effects of bFGF were evaluated following inhibition of fibroblast growth factor receptor 1 (FGFR1) with PD173074 and inhibition of ERK with PD98059.ResultsFollowing OGD/R of HBMECs, bFGF significantly reduced cell permeability and apoptosis and significantly inhibited the down-regulation of the expressions of proteins associated with tight junctions, adherens junctions, apoptosis and matrix metalloproteinases (MMPs). The effects of bFGF were mediated by the activation of FGFR1 and ERK, as they were blocked by FGFR1 and ERK inhibitors.ConclusionsPermeability and apoptosis of HBMECs challenged by OGD/R were reduced by bFGF by activation of the FGFR1 and the ERK pathway.

Targeting Autophagy by MPT0L145, a Highly Potent PIK3C3 Inhibitor, Provides Synergistic Interaction to Targeted or Chemotherapeutic Agents in Cancer Cells.

Anticancer therapies reportedly promote pro-survival autophagy in cancer cells that confers drug resistance, rationalizing the concept to combine autophagy inhibitors to increase their therapeutic potential. We previously identified that MPT0L145 is a PIK3C3/FGFR inhibitor that not only increases autophagosome formation due to fibroblast growth factor receptor (FGFR) inhibition but also perturbs autophagic flux via PIK3C3 inhibition in bladder cancer cells harboring FGFR activation. In this study, we hypothesized that combined-use of MPT0L145 with agents that induce pro-survival autophagy may provide synthetic lethality in cancer cells without FGFR activation. The results showed that MPT0L145 synergistically sensitizes anticancer effects of gefitinib and gemcitabine in non-small cell lung cancer A549 cells and pancreatic cancer PANC-1 cells, respectively. Mechanistically, drug combination increased incomplete autophagy due to impaired PIK3C3 function by MPT0L145 as evidenced by p62 accumulation and no additional apoptotic cell death was observed. Meanwhile, drug combination perturbed survival pathways and increased vacuolization and ROS production in cancer cells. In conclusion, the data suggest that halting pro-survival autophagy by targeting PIK3C3 with MPT0L145 significantly sensitizes cancer cells to targeted or chemotherapeutic agents, fostering rational combination strategies for cancer therapy in the future.

Medial Temporal Lobe Dysgenesis and More in a Man with Hypochondroplasia and Epilepsy

Hypochondroplasia, achondroplasia, and thanatophoric dysplasia are related at the molecular level, all caused by fibroblast growth factor receptor 3 (FGFR3) gene mutations. They differ in severity. FGFR3 has critical roles in fibroblast growth factor (FGF) signalling pathways during bone growth and cerebral cortical development. Mutations of the FGFR3 gene lead to constitutive activation of FGFR3. The well-described brain malformation in thanatophoric dysplasia is characterized by gross abnormalities of temporal lobe patterning and severe dysplasia of the hippocampus. Experimental models suggest that increased proliferation, abnormal migration, and decreased apoptosis are involved. However, reports of the brain findings in hypochondroplasia are based solely on radiologic imaging.We present the neuropathology of a 44 year-old man with hypochondroplasia, epilepsy, and significant intellectual disability. The temporal lobes are enlarged, prominent fissures traverse the inferior temporal surface, and the hippocampus is abnormally folded. Microscopically, the dentate gyrus is variably small or thin and is located near the edge of a gyrus. Ammon’s horn is displaced and meandering. Subicular-like clusters are profuse. Complex gyri resemble microgyria. White matter forms a subpial border in some gyri. In summary: medial temporal lobe dysgenesis.This individual also had many autistic features including stereotypies and head banging. The latter could explain another surprising set of brain abnormalities unrelated to the presumed FGFR3-related syndrome.LEARNING OBJECTIVESThis presentation will enable the learner to:1.Summarize current theories on the pathogenesis of FGFR3-related cortical malformation2.Describe the brain abnormalities in hypochondroplasia3.Identify the neuropathology resulting from head banging

Inhibition of FGF Receptor-1 Suppresses Alcohol Consumption: Role of PI3 Kinase Signaling in Dorsomedial Striatum.

Excessive alcohol intake leads to mesostriatal neuroadaptations, and to addiction phenotypes. We recently found in rodents that alcohol increases fibroblast growth factor 2 (FGF2) expression in the dorsomedial striatum (DMS), which promotes alcohol consumption. Here, we show that systemic or intra-DMS blockade of the FGF2 receptor, FGF receptor-1 (FGFR1), suppresses alcohol consumption, and that the effects of FGF2-FGFR1 on alcohol drinking are mediated via the phosphoinositide 3 kinase (PI3K) signaling pathway. Specifically, we found that sub-chronic alcohol treatment (7 d × 2.5 g/kg, i.p.) increased Fgfr1 mRNA expression in the dorsal hippocampus and dorsal striatum. However, prolonged and excessive voluntary alcohol consumption in a two-bottle choice procedure increased Fgfr1 expression selectively in DMS. Importantly, systemic administration of the FGFR1 inhibitor PD173074 to mice, as well as its infusion into the DMS of rats, decreased alcohol consumption and preference, with no effects on natural reward consumption. Finally, inhibition of the PI3K, but not of the mitogen-activated protein kinase (MAPK) signaling pathway, blocked the effects of FGF2 on alcohol intake and preference. Our results suggest that activation of FGFR1 by FGF2 in the DMS leads to activation of the PI3K signaling pathway, which promotes excessive alcohol consumption, and that inhibition of FGFR1 may provide a novel therapeutic target for alcohol use disorder.SIGNIFICANCE STATEMENT Long-term alcohol consumption causes neuroadaptations in the mesostriatal reward system, leading to addiction-related behaviors. We recently showed that alcohol upregulates the expression of fibroblast growth factor 2 (FGF2) in dorsomedial striatum (DMS) or rats and mice, and in turn, FGF2 increases alcohol consumption. Here, we show that long-term alcohol intake also increases the expression of the FGF2 receptor, FGFR1 in the DMS. Importantly, inhibition of FGFR1 activity by a selective receptor antagonist reduces alcohol drinking, when given systemically or directly into the DMS. We further show that the effects of FGF2-FGFR1 on alcohol drinking are mediated via activation of the PI3K intracellular signaling pathway, providing an insight on the mechanism for this effect.