NCAM-derived peptides function as agonists for the fibroblast growth factor receptor

A head-to-head comparison of [68Ga]Ga-DOTA-FGFR1 and [18F]FDG PET/CT in the diagnosis of lung cancer

PURPOSE

This study aimed to compare the diagnostic value of [68Ga]Ga-DOTA-FGFR1 and [18F]FDG PET/CT in the evaluation of lung cancer patients.

METHODS

A prospective study was conducted between March 2023 and July 2023. Patients with high clinical suspicion of lung cancer were recruited. Each participant underwent PET/CT scanning using [68Ga]Ga-DOTA-FGFR1 and [18F]FDG within 6 days. Histopathology and clinical follow-up results serve as reference criteria for final diagnosis. We used a paired samples t-test or a Wilcoxon signed-rank test to compare the uptake of [68Ga]Ga-DOTA-FGFR1 and [18F]FDG. The diagnostic performance between the two tracers was compared using the McNemar χ² test.

RESULTS

A total of 101 participants were included (mean age 63.267 ± 9.344 [range 39-86 years]). In benign lung lesions, [68Ga]Ga-DOTA-FGFR1 had lower TBR and SUVmax than [18F]FDG (2.924 vs. 5.705, P < 0.001;1.395 vs. 4.014, P < 0.001). The TBR of [68Ga]Ga-DOTA-FGFR1 in benign lymph nodes was also lower than [18F]FDG (0.880 vs. 1.25, P < 0.001). [68Ga]Ga-DOTA-FGFR1 had a higher diagnostic specificity for primary tumors than [18F]FDG (52% vs. 28%, P = 0.031). The specificity, accuracy, and PPV of [68Ga]Ga-DOTA-FGFR1 for detecting lymph node metastasis were 82.54%, 78.66%, and 53.73%, respectively, higher than that of [18F]FDG (53.80%, P < 0.001, 63.15%, P < 0.001 and 38.35%, P = 0.003). However, its sensitivity in the diagnosis of lymph node and distant metastasis was not as good as [18F]FDG PET/CT (P < 0.001, P = 0.016, respectively). There was a significant correlation between [68Ga]Ga-DOTA-FGFR1 uptake and FGFR1 expression (Spearman r = 0.6901, p < 0.0001).

CONCLUSIONS

[68Ga]Ga-DOTA-FGFR1 PET/CT had higher specificity than [18F]FDG PET/CT for the detection of primary lung cancer. In addition, [68Ga]Ga-DOTA-FGFR1 PET/CT also had higher diagnostic accuracy, specificity, and NPV for lymph node metastasis, but its diagnostic sensitivity for metastatic lesions was lower than [18F]FDG PET/CT. Therefore, [68Ga]Ga-DOTA-FGFR1 can be used as an effective supplement to [18F]FDG to a certain extent.

Human Biodistribution and Radiation Dosimetry of the Targeting Fibroblast Growth Factor Receptor 1-Positive Tumors Tracer [68Ga]Ga-DOTA-FGFR1-Peptide

Objective: [68Ga]Ga-DOTA-FGFR1-peptide is a novel positron emission tomography (PET) radiotracer targeting fibroblast growth factor receptor 1 (FGFR1). This study evaluated the safety, biodistribution, radiation dosimetry, and imaging potential of [68Ga]Ga-DOTA-FGFR1-peptide. Methods: The FGFR1-targeting peptide DOTA-(PEG2)-KAEWKSLGEEAWHSK was synthesized by manual solid-phase peptide synthesis with high-performance liquid chromatography purification, and labeled with 68Ga with DOTA as chelating agent. We recruited 14 participants and calculated the radiation dose of 4 of these pathologically confirmed nontumor subjects using OLINDA/EXM 2.2.0 software. At the same time, the imaging potential in 10 of these lung cancer patients was evaluated. Results: The biodistribution of [68Ga]Ga-DOTA-FGFR1-peptide in 4 subjects showed the highest uptake in the bladder and kidney. Dosimetry analysis indicated that the bladder wall received the highest effective dose (3.73E-02 mSv/MBq), followed by the lungs (2.36E-03 mSv/MBq) and red bone marrow (2.09E-03 mSv/MBq). No normal organs were found to have excess specific absorbed doses. The average systemic effective dose was 4.97E-02 mSv/MBq. The primary and metastatic tumor lesions were clearly visible on PET/computed tomography (CT) images in 10 patients. Conclusion: Our results indicate that [68Ga]Ga-DOTA-FGFR1-peptide has a good dosimetry profile and can be used safely in humans, and it has significant potential value for clinical PET/CT imaging.

A view of the genetic and proteomic profile of extracellular matrix molecules in aging and stroke

Introduction

Modification of the extracellular matrix (ECM) is one of the major processes in the pathology of brain damage following an ischemic stroke. However, our understanding of how age-related ECM alterations may affect stroke pathophysiology and its outcome is still very limited.

Methods

We conducted an ECM-targeted re-analysis of our previously obtained RNA-Seq dataset of aging, ischemic stroke and their interactions in young adult (3-month-old) and aged (18-month-old) mice. The permanent middle cerebral artery occlusion (pMCAo) in rodents was used as a model of ischemic stroke. Altogether 56 genes of interest were chosen for this study.

Results

We identified an increased activation of the genes encoding proteins related to ECM degradation, such as matrix metalloproteinases (MMPs), proteases of a disintegrin and metalloproteinase with the thrombospondin motifs (ADAMTS) family and molecules that regulate their activity, tissue inhibitors of metalloproteinases (TIMPs). Moreover, significant upregulation was also detected in the mRNA of other ECM molecules, such as proteoglycans, syndecans and link proteins. Notably, we identified 8 genes where this upregulation was enhanced in aged mice in comparison with the young ones. Ischemia evoked a significant downregulation in only 6 of our genes of interest, including those encoding proteins associated with the protective function of ECM molecules (e.g., brevican, Hapln4, Sparcl1); downregulation in brevican was more prominent in aged mice. The study was expanded by proteome analysis, where we observed an ischemia-induced overexpression in three proteins, which are associated with neuroinflammation (fibronectin and vitronectin) and neurodegeneration (link protein Hapln2). In fibronectin and Hapln2, this overexpression was more pronounced in aged post-ischemic animals.

Conclusion

Based on these results, we can conclude that the ratio between the protecting and degrading mechanisms in the aged brain is shifted toward degradation and contributes to the aged tissues' increased sensitivity to ischemic insults. Altogether, our data provide fresh perspectives on the processes underlying ischemic injury in the aging brain and serve as a freely accessible resource for upcoming research.

18F-labeled FGFR1 peptide: a new PET probe for subtype FGFR1 receptor imaging

Introduction

The fibroblast growth factor receptor (FGFR) family is highly expressed in a variety of tumor types and represents a new target for cancer therapy. Different FGFR subtype aberrations have been found to exhibit highly variable sensitivity and efficacy to FGFR inhibitors.

Methods

The present study is the first to suggest an imaging method for assessing FGFR1 expression. The FGFR1-targeting peptide NOTA-PEG2-KAEWKSLGEEAWHSK was synthesized by manual solid-phase peptide synthesis and high-pressure liquid chromatography (HPLC) purification and then labeled with fluorine-18 using NOTA as a chelator. In vitro and in vivo experiments were conducted to evaluate the stability, affinity and specificity of the probe. Tumor targeting efficacy and biodistribution were evaluated by micro-PET/CT imaging in RT-112, A549, SNU-16 and Calu-3 xenografts.

Results

The radiochemical purity of [18F]F-FGFR1 was 98.66% ± 0.30% (n = 3) with excellent stability. The cellular uptake rate of [18F]F-FGFR1 in the RT-112 cell line (FGFR1 overexpression) was higher than that in the other cell lines and could be blocked by the presence of excess unlabeled FGFR1 peptide. Micro-PET/CT imaging revealed a significant concentration of [18F]F-FGFR1 in RT-112 xenografts with no or very low uptake in nontargeted organs and tissues, which demonstrated that [18F]F-FGFR1 was selectively taken up by FGFR1-positive tumors.

Conclusion

[18F]F-FGFR1 showed high stability, affinity, specificity and good imaging capacity for FGFR1-overexpressing tumors in vivo, which provides new application potential in the visualization of FGFR1 expression in solid tumors.

NCAM2 Fibronectin type-III domains form a rigid structure that binds and activates the Fibroblast Growth Factor Receptor

NCAM1 and NCAM2 have ectodomains consisting of 5 Ig domains followed by 2 membrane-proximal FnIII domains. In this study we investigate and compare the structures and functions of these FnIII domains. The NCAM1 and -2 FnIII2 domains both contain a Walker A motif. In NCAM1 binding of ATP to this motif interferes with NCAM1 binding to FGFR. We obtained a structural model of the NCAM2 FnIII2 domain by NMR spectroscopy, and by titration with an ATP analogue we show that the NCAM2 Walker A motif does not bind ATP. Small angle X-ray scattering (SAXS) data revealed that the NCAM2 FnIII1-2 double domain exhibits a very low degree of flexibility. Moreover, recombinant NCAM2 FnIII domains bind FGFR in vitro, and the FnIII1-2 double domain induces neurite outgrowth in a concentration-dependent manner through activation of FGFR. Several synthetic NCAM1-derived peptides induce neurite outgrowth via FGFR. Only 2 of 5 peptides derived from similar regions in NCAM2 induce neurite outgrowth, but the most potent of these peptides stimulates neurite outgrowth through FGFR-dependent activation of the Ras-MAPK pathway. These results reveal that the NCAM2 FnIII domains form a rigid structure that binds and activates FGFR in a manner related to, but different from NCAM1.

GDNF/GFRα1 Complex Abrogates Self-Renewing Activity of Cortical Neural Precursors Inducing Their Differentiation

The balance between factors leading to proliferation and differentiation of cortical neural precursors (CNPs) determines the correct cortical development. In this work, we show that GDNF and its receptor GFRα1 are expressed in the neocortex during the period of cortical neurogenesis. We show that the GDNF/GFRα1 complex inhibits the self-renewal capacity of mouse CNP cells induced by fibroblast growth factor 2 (FGF2), promoting neuronal differentiation. While GDNF leads to decreased proliferation of cultured cortical precursor cells, ablation of GFRα1 in glutamatergic cortical precursors enhances its proliferation. We show that GDNF treatment of CNPs promoted morphological differentiation even in the presence of the self-renewal-promoting factor, FGF2. Analysis of GFRα1-deficient mice shows an increase in the number of cycling cells during cortical development and a reduction in dendrite development of cortical GFRα1-expressing neurons. Together, these results indicate that GDNF/GFRα1 signaling plays an essential role in regulating the proliferative condition and the differentiation of cortical progenitors.

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GFRα1 receptor is expressed in the neocortex during the period of neurogenesis

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GDNF/GFRα1 complex inhibits self-renewing of cortical neuronal precursors

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GDNF and GFRα1 promote neurogenic differentiation of cortical neural progenitors

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Requirement of GFRα1 for proper dendrite development of cortical neurons

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.

Neuroprotective role of fibronectin in neuron-glial extrasynaptic transmission

Most hypotheses concerning the mechanisms underlying Parkinson's disease are based on altered synaptic transmission of the nigrostriatal system. However, extrasynaptic transmission was recently found to affect dopamine neurotransmitter delivery by anisotropic diffusion in the extracellular matrix, which is modulated by various extracellular matrix components such as fibronectin. The present study reviewed the neuroprotective effect of fibronectin in extrasynaptic transmission. Fibronectin can regulate neuroactive substance diffusion and receptor activation, and exert anti- neuroinflammatory, adhesive and neuroprotective roles. Fibronectin can bind to integrin and growth factor receptors to transactivate intracellular signaling events such as the phosphatidylinositol 3-kinase/protein kinase B pathway to regulate or amplify growth factor-like neuroprotective actions. Fibronectin is assembled into a fibrillar network around cells to facilitate cell migration, molecule and ion diffusion, and even drug delivery and treatment. In addition, the present study analyzed the neuroprotective mechanism of fibronectin in the pathogenesis of Parkinson's disease, involving integrin and growth factor receptor interactions, and discussed the possible therapeutic and diagnostic significance of fibronectin in Parkinson's disease.

Screening of bioactive peptides using an embryonic stem cell-based neurodifferentiation assay

Differentiation of pluripotent stem cells, PSCs, towards neural lineages has attracted significant attention, given the potential use of such cells for in vitro studies and for regenerative medicine. The present experiments were designed to identify bioactive peptides which direct PSC differentiation towards neural cells. Fifteen peptides were designed based on NCAM, FGFR, and growth factors sequences. The effect of peptides was screened using a mouse embryonic stem cell line expressing luciferase dual reporter construct driven by promoters for neural tubulin and for elongation factor 1. Cell number was estimated by measuring total cellular DNA. We identified five peptides which enhanced activities of both promoters without relevant changes in cell number. We selected the two most potent peptides for further analysis: the NCAM-derived mimetic FGLL and the synthetic NCAM ligand, Plannexin. Both compounds induced phenotypic neuronal differentiation, as evidenced by increased neurite outgrowth. In summary, we used a simple, but sensitive screening approach to identify the neurogenic peptides. These peptides will not only provide new clues concerning pathways of neurogenesis, but they may also be interesting biotechnology tools for in vitro generation of neurons.

NCAM function in the adult brain: lessons from mimetic peptides and therapeutic potential

Neural cell adhesion molecules (NCAMs) are complexes of transmembranal proteins critical for cell-cell interactions. Initially recognized as key players in the orchestration of developmental processes involving cell migration, cell survival, axon guidance, and synaptic targeting, they have been shown to retain these functions in the mature adult brain, in relation to plastic processes and cognitive abilities. NCAMs are able to interact among themselves (homophilic binding) as well as with other molecules (heterophilic binding). Furthermore, they are the sole molecule of the central nervous system undergoing polysialylation. Most interestingly polysialylated and non-polysialylated NCAMs display opposite properties. The precise contributions each of these characteristics brings in the regulations of synaptic and cellular plasticity in relation to cognitive processes in the adult brain are not yet fully understood. With the aim of deciphering the specific involvement of each interaction, recent developments led to the generation of NCAM mimetic peptides that recapitulate identified binding properties of NCAM. The present review focuses on the information such advances have provided in the understanding of NCAM contribution to cognitive function.

The adhesion molecule NCAM promotes ovarian cancer progression via FGFR signalling

Epithelial ovarian carcinoma (EOC) is an aggressive neoplasm, which mainly disseminates to organs of the peritoneal cavity, an event mediated by molecular mechanisms that remain elusive. Here, we investigated the expression and functional role of neural cell adhesion molecule (NCAM), a cell surface glycoprotein involved in brain development and plasticity, in EOC. NCAM is absent from normal ovarian epithelium but becomes highly expressed in a subset of human EOC, in which NCAM expression is associated with high tumour grade, suggesting a causal role in cancer aggressiveness. We demonstrate that NCAM stimulates EOC cell migration and invasion in vitro and promotes metastatic dissemination in mice. This pro-malignant function of NCAM is mediated by its interaction with fibroblast growth factor receptor (FGFR). Indeed, not only FGFR signalling is required for NCAM-induced EOC cell motility, but targeting the NCAM/FGFR interplay with a monoclonal antibody abolishes the metastatic dissemination of EOC in mice. Our results point to NCAM-mediated stimulation of FGFR as a novel mechanism underlying EOC malignancy and indicate that this interplay may represent a valuable therapeutic target.

Neuritogenic and neuroprotective properties of peptide agonists of the fibroblast growth factor receptor

Fibroblast growth factor receptors (FGFRs) interact with their cognate ligands, FGFs, and with a number of cell adhesion molecules (CAMs), such as the neural cell adhesion molecule (NCAM), mediating a wide range of events during the development and maintenance of the nervous system. Determination of protein structure, in silico modeling and biological studies have recently resulted in the identification of FGFR binding peptides derived from various FGFs and NCAM mimicking the effects of these molecules with regard to their neuritogenic and neuroprotective properties. This review focuses on recently developed functional peptide agonists of FGFR with possible therapeutic potential.

Exploiting Surface Plasmon Resonance (SPR) Technology for the Identification of Fibroblast Growth Factor-2 (FGF2) Antagonists Endowed with Antiangiogenic Activity

Angiogenesis, the process of new blood vessel formation, is implicated in various physiological/pathological conditions, including embryonic development, inflammation and tumor growth. Fibroblast growth factor-2 (FGF2) is a heparin-binding angiogenic growth factor involved in various physiopathological processes, including tumor neovascularization. Accordingly, FGF2 is considered a target for antiangiogenic therapies. Thus, numerous natural/synthetic compounds have been tested for their capacity to bind and sequester FGF2 in the extracellular environment preventing its interaction with cellular receptors. We have exploited surface plasmon resonance (SPR) technique in search for antiangiogenic FGF2 binders/antagonists. In this review we will summarize our experience in SPR-based angiogenesis research, with the aim to validate SPR as a first line screening for the identification of antiangiogenic compounds.

Portrait of an enzyme, a complete structural analysis of a multimodular {beta}-N-acetylglucosaminidase from Clostridium perfringens

Common features of the extracellular carbohydrate-active virulence factors involved in host-pathogen interactions are their large sizes and modular complexities. This has made them recalcitrant to structural analysis, and therefore our understanding of the significance of modularity in these important proteins is lagging. Clostridium perfringens is a prevalent human pathogen that harbors a wide array of large, extracellular carbohydrate-active enzymes and is an excellent and relevant model system to approach this problem. Here we describe the complete structure of C. perfringens GH84C (NagJ), a 1001-amino acid multimodular homolog of the C. perfringens micro-toxin, which was determined using a combination of small angle x-ray scattering and x-ray crystallography. The resulting structure reveals unprecedented insight into how catalysis, carbohydrate-specific adherence, and the formation of molecular complexes with other enzymes via an ultra-tight protein-protein interaction are spatially coordinated in an enzyme involved in a host-pathogen interaction.