Neural adhesion molecule L1 as a member of the immunoglobulin superfamily with binding domains similar to fibronectin

L1CAM mimetic compound duloxetine improves cognitive impairment in 5xFAD mice and protects Aβ1-42-damaged HT22 cells

BACKGROUND

Synapse loss and damage are underlying causes of Alzheimer's disease. Duloxetine has been identified as a mimetic of neural adhesion molecule L1CAM, a neuronal synapse component, suggesting duloxetine could be therapeutic for Alzheimer's disease.

METHODS

Cognitive function in 5xFAD mice was evaluated by open field, novel object recognition, and Morris water maze tests. Hippocampal and cortical Aβ1-40, Aβ1-42 and amyloid plaque deposition were quantified by ELISA and immunohistochemistry. RT-qPCR and western blotting quantified the effects of duloxetine treatment on L1CAM levels and PI3K/Akt/CREB signaling pathway activation. Apoptosis markers Bcl-2 and Bax were also measured by RT-qPCR and western blotting. HT22 cell survival was measured by CCK8 assay.

RESULTS

Duloxetine preserved learning and memory abilities, but had no effect on locomotor performance of 5xFAD mice. Duloxetine decreased Aβ1-42 expression levels, increased Aβ1-40 levels, reduced amyloid plaque formation, and activated the PI3K/Akt/CREB signaling pathway in both cortices and hippocampi of 5xFAD mice. Moreover, duloxetine increased the expression of L1CAM and Bcl-2, and inhibited the expression of Bax, as well as prevented Aβ1-42 cytotoxicity in wild-type, but not L1CAM-knockdown HT22 cells, suggesting a feed-forward mechanism for duloxetine-mediated neuroprotection, whereby duloxetine induces and activates L1CAM to exert neuroprotective effects.

CONCLUSIONS

Our findings demonstrate that duloxetine plays a neuroprotective role in 5xFAD mice and HT22 cells through activating L1CAM, likely by regulating the PI3K/Akt/CREB signaling pathway. These results suggest that duloxetine may be a potential reagent for the treatment of Alzheimer's disease.

Morphological, immunohistochemical and molecular analysis of follicular dendritic cell sarcomas: L1CAM as a new diagnostic marker

AIMS

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm exhibiting morphological and immunophenotypical features of follicular dendritic cells. Given its rarity and broad morphological spectrum, diagnosis can be challenging. Knowledge of the molecular basis of this rare tumour is still limited. To further refine the biological and diagnostic characteristics of these neoplasms, we performed a comprehensive morphological, immunohistochemical and molecular analysis.

METHODS AND RESULTS

As well as histopathological and immunohistochemical analysis, we performed molecular analysis by next-generation panel sequencing of 15 tissue samples from 13 patients diagnosed with FDCS. In the histomorphological analysis of this FDCS series, we observed a morphological spectrum with a mixture of spindled and epithelioid cells (six of 13), but also cases with predominant epithelioid cytomorphology (seven of 13). We identified the L1 cell adhesion molecule (L1CAM) as a novel immunomarker of FDCS, as it was variably expressed in all cases. Sequencing led to the identification of 170 variants (classes 3, 4 and 5) in 112 genes. The most frequently detected (likely) pathogenic mutations affected NFKBIA (five of 13), leading to activation of nuclear factor kappa B (NFκB) signalling. Notably, deleterious NFKBIA mutations were only found in cases with predominant epithelioid morphology (five of seven). Furthermore, TP53 mutations were detected in two cases with epithelioid morphology and high proliferation rate, and one of these cases relapsed twice.

CONCLUSIONS

The morphological and genetic landscape of FDCS in this series was heterogeneous. However, in line with previous data, we identified recurrent genetic alterations affecting NFkB signalling. The expression of the adhesion molecule L1CAM might aid in the diagnosis of this uncommon neoplasia.

Hetero Sandwich Immunoassay as Tool to Probe the Composition of the Extracellular Vesicles Membranes: The Case Study of L1CAM Localization

Lateral flow immunoassays (LFIAs) are widely used for point-of-care diagnostic devices due to their simplicity, low cost, and rapid results. In this work, we demonstrate that a heterosandwich design LFIA can be an effective tool for verifying the presence of different proteins on the same particles. As a case study, we address a recent controversy regarding the presence of the protein L1CAM on the extracellular vesicles (EVs). EVs are crucial for cell communication and may serve as valuable disease biomarkers, including for neurodegenerative disorders. EVs from neuronal cells can cross the blood-brain barrier and be selectively isolated from plasma. Although L1CAM has been suggested as a marker for neuron-derived EVs, recent studies report that L1CAM exists as a cleaved soluble protein in plasma, not associated with EVs. We propose a heterosandwich LFIA to detect and quantify L1CAM and a confirmed EV marker, tetraspanin CD63 or CD9, on the same EV. This assay, together with several control experiments on EVs isolated from plasma by size exclusion chromatography (SEC), demonstrates that although most L1CAM in plasma is present as soluble cleaved proteins, 13% of the EVs are strongly associated with this protein. This evidence is confirmed by dynamic light scattering measurements, showing a significant size increase of gold nanoparticles conjugated with L1CAM antibodies when exposed to EVs but not to cleaved soluble L1CAM. Our results validate the selective immune-isolation of L1CAM-EVs, resolving the controversy by confirming that L1CAM is indeed associated with a significant fraction of EVs despite the presence of its soluble form in plasma.

The mechanism of L1 cell adhesion molecule interacting with protein tyrosine kinase 2 to regulate the focal adhesion kinase-growth factor receptor-bound protein 2-son of sevenless-rat sarcoma pathway in the identification and treatment of type I high-risk endometrial cancer

Objective

The objective of this study was to investigate how L1 cell adhesion molecule (L1CAM) interacting with protein tyrosine kinase 2 (PTK2) affects endometrial cancer (EC) progression and determine its association with the focal adhesion kinase (FAK)-growth factor receptor-bound protein 2 (GRB2)-son of sevenless (SOS)-rat sarcoma (RAS) pathway. EC is a female cancer of major concern in the world, and its incidence has increased rapidly in recent years. L1CAM is considered a reliable marker of poor prognosis in patients with EC.

Material and Methods

A single-center and prospective study was conducted using data from the Cancer Genome Atlas and samples from normal and EC tissues to explore the differential expression of L1CAM. Additional experimental models included human immortalized endometrial epithelium cells (hEECs) and EC cell lines such as KLE, RL95-2, and Ishikawa. L1CAM expression was regulated using lentiviruses designed for either overexpression or interference, and PTK2/focal adhesion kinase (FAK) signaling was inhibited with PF431396. Transfected KLE cells were injected into mice, and tumor growth was monitored over 14 days. Cellular proliferation and survival were assessed using cell counting kit, colony formation, and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate (dUTP) nick-end labeling assays. Metastatic behavior was evaluated through Transwell assays for cell migration and invasion. The expression levels of matrix metallopeptidase (MMP) 2 and MMP9 were determined by Western blot. In addition, the activation of the FAK-GRB2-SOS-RAS pathway was examined by assessing the protein levels of FAK, GRB2, SOS, and RAS.

Results

There was a significant difference in L1CAM expression between EC tumor tissues and normal tissues, and L1CAM messenger RNA (1.85-fold) and L1CAM protein (2.59-fold) were significantly more expressed in EC tissues (P < 0.01) than in normal tissues. The tumor growth of L1CAM overexpressing EC cells was faster than that of negative control EC cells (6.43 fold; P < 0.001). L1CAM promoted the expression of FAK (1.43-2.72-fold; P < 0.001); enhanced EC cell proliferation (P < 0.01), survival and motility (P < 0.001), migration (P < 0.001), and invasion (P < 0.001); and activated the FAK-GRB2-SOS-RAS pathway, all of which were reversed when FAK expression was not upregulated (P < 0.001).

Conclusion

By upregulating PTK2 and its encoded protein FAK, L1CAM was found to promote tumor progression and increase the activation of the FAK-GRB2-SOS-RAS pathway. These findings establish L1CAM and PTK2 as reference genes for poor prognostic prediction in EC and as targets for EC therapy, providing a valuable basis for distinguishing between benign and malignant endometrial conditions and justifying the necessity of targeted therapeutic approaches.

KLF12 interacts with TRIM27 to affect cisplatin resistance and cancer metastasis in esophageal squamous cell carcinoma by regulating L1CAM expression

Krüppel-like factor 12 (KLF12) has been characterized as a transcriptional repressor, and previous studies have unveiled its roles in angiogenesis, neural tube defect, and natural killer (NK) cell proliferation. However, the contribution of KLF12 to cancer treatment remains undefined. Here, we show that KLF12 is downregulated in various cancer types, and KLF12 downregulation promotes cisplatin resistance and cancer metastasis in esophageal squamous cell carcinoma (ESCC). Mechanistically, KLF12 binds to the promoters of L1 Cell Adhesion Molecule (L1CAM) and represses its expression. Depletion of L1CAM abrogates cisplatin resistance and cancer metastasis caused by KLF12 loss. Moreover, the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) binds to the N-terminal region of KLF12 and ubiquitinates KLF12 at K326 via K33-linked polyubiquitination. Notably, TRIM27 depletion enhances the transcriptional activity of KLF12 and consequently inhibits L1CAM expression. Overall, our study elucidated a novel regulatory mechanism involving TRIM27, KLF12 and L1CAM, which plays a substantial role in cisplatin resistance and cancer metastasis in ESCC. Targeting these genes could be a promising approach for ESCC treatment.

Synaptic cell adhesion molecules contribute to the pathogenesis and progression of fragile X syndrome

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and a monogenic cause of autism spectrum disorders. Deficiencies in the fragile X messenger ribonucleoprotein, encoded by the FMR1 gene, lead to various anatomical and pathophysiological abnormalities and behavioral deficits, such as spine dysmorphogenesis and learning and memory impairments. Synaptic cell adhesion molecules (CAMs) play crucial roles in synapse formation and neural signal transmission by promoting the formation of new synaptic contacts, accurately organizing presynaptic and postsynaptic protein complexes, and ensuring the accuracy of signal transmission. Recent studies have implicated synaptic CAMs such as the immunoglobulin superfamily, N-cadherin, leucine-rich repeat proteins, and neuroligin-1 in the pathogenesis of FXS and found that they contribute to defects in dendritic spines and synaptic plasticity in FXS animal models. This review systematically summarizes the biological associations between nine representative synaptic CAMs and FMRP, as well as the functional consequences of the interaction, to provide new insights into the mechanisms of abnormal synaptic development in FXS.

Characterization of a novel T cell-engaging bispecific antibody for elimination of L1CAM-positive tumors

Neural cell adhesion molecule L1 (L1CAM) is a cell-surface glycoprotein involved in cancer occurrence and migration. Up to today, L1CAM-targeted therapy appeared limited efficacy in clinical trials although quite a few attempts by monoclonal antibody (mAb) or chimeric antigen receptor T-cell therapy (CAR-T) have been reported. Therefore, the development of new effective therapies targeting L1CAM is highly desirable. It has been demonstrated that T cell-engaging bispecific antibody (TCE) plays an effective role in cancer immunotherapy by redirecting the cytotoxic activity of CD3+ T cells to tumor cells, resulting in tumor cell death. In this study, we designed and characterized a novel bispecific antibody (CE7-TCE) based on the IgG-(L)-ScFv format, which targets L1CAM and CD3 simultaneously. In vitro, CE7-TCE induced specific killing of L1CAM-positive tumor cells through T cells. In vivo, CE7-TCE inhibited tumor growth in human peripheral blood mononuclear cell/tumor cell co-grafting models. To overcome the adaptive immune resistance (AIR) that impairs the efficacy of TCEs, we conducted a combination therapy of CE7-TCE with Pembrolizumab (anti-PD1 mAb), which enhanced the anti-tumor activity of CE7-TCE. Our results confirmed the feasibility of using L1CAM as a TCE target for the treatment of solid tumors and revealed the therapeutic potential of CE7-TCE combined with immune checkpoint inhibitors.

The role of L1CAM as predictor of poor prognosis in stage I endometrial cancer: a systematic review and meta-analysis

INTRODUCTION

Molecular and genomic profiling in endometrial cancer is increasing popularity. L1 cell adhesion molecule (L1CAM) is frequently mutated in endometrial cancer. In this paper, we aim to evaluate the prognostic role of L1CAM in patients with stage I endometrial cancer.

METHODS

We performed a systematic review and meta-analysis searching in PubMed (MEDLINE), EMBASE, and Web of Science database to identify studies reporting the expression of L1CAM in endometrial cancer. The primary endpoint measure was to assess and evaluate the impact of L1CAM on survival outcomes. This study was performed according to the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) statement.

RESULTS

Five studies were included. The pooled results suggested that L1CAM expression influences survival outcomes in stage I endometrial cancer. High L1CAM expression correlated with worse disease-free survival (HR 4.11, 95% CI 1.02-16.59, p = 0.047) and overall survival (HR 3.62, 95% CI 1.32-9.31, p = 0.012). High L1CAM level was also associated with a more aggressive FIGO grade and with older age.

CONCLUSION

This systematic review supported that L1CAM have a prognostic role in stage I endometrial cancer, thus providing a potential useful tool for tailoring the need of adjuvant therapy.

Recommendations for reproducibility of cerebrospinal fluid extracellular vesicle studies

Cerebrospinal fluid (CSF) is a clear, transparent fluid derived from blood plasma that protects the brain and spinal cord against mechanical shock, provides buoyancy, clears metabolic waste and transports extracellular components to remote sites in the brain. Given its contact with the brain and the spinal cord, CSF is the most informative biofluid for studies of the central nervous system (CNS). In addition to other components, CSF contains extracellular vesicles (EVs) that carry bioactive cargoes (e.g., lipids, nucleic acids, proteins), and that can have biological functions within and beyond the CNS. Thus, CSF EVs likely serve as both mediators of and contributors to communication in the CNS. Accordingly, their potential as biomarkers for CNS diseases has stimulated much excitement for and attention to CSF EV research. However, studies on CSF EVs present unique challenges relative to EV studies in other biofluids, including the invasive nature of CSF collection, limited CSF volumes and the low numbers of EVs in CSF as compared to plasma. Here, the objectives of the International Society for Extracellular Vesicles CSF Task Force are to promote the reproducibility of CSF EV studies by providing current reporting and best practices, and recommendations and reporting guidelines, for CSF EV studies. To accomplish this, we created and distributed a world-wide survey to ISEV members to assess methods considered 'best practices' for CSF EVs, then performed a detailed literature review for CSF EV publications that was used to curate methods and resources. Based on responses to the survey and curated information from publications, the CSF Task Force herein provides recommendations and reporting guidelines to promote the reproducibility of CSF EV studies in seven domains: (i) CSF Collection, Processing, and Storage; (ii) CSF EV Separation/Concentration; (iii) CSF EV Size and Number Measurements; (iv) CSF EV Protein Studies; (v) CSF EV RNA Studies; (vi) CSF EV Omics Studies and (vii) CSF EV Functional Studies.

Flow cytometry-based quantification of genome editing efficiency in human cell lines using the L1CAM gene

CRISPR/Cas9 is a powerful genome editing system that has remarkably facilitated gene knockout and targeted knock-in. To accelerate the practical use of CRISPR/Cas9, however, it remains crucial to improve the efficiency, precision, and specificity of genome editing, particularly targeted knock-in, achieved with this system. To improve genome editing efficiency, researchers should first have a molecular assay that allows sensitive monitoring of genome editing events with simple procedures. In the current study, we demonstrate that genome editing events occurring in L1CAM, an X-chromosome gene encoding a cell surface protein, can be readily monitored using flow cytometry (FCM) in multiple human cell lines including neuroblastoma cell lines. The abrogation of L1CAM was efficiently achieved using Cas9 nucleases which disrupt exons encoding the L1CAM extracellular domain, and was easily detected by FCM using anti-L1CAM antibodies. Notably, L1CAM-abrogated cells could be quantified by FCM in four days after transfection with a Cas9 nuclease, which is much faster than an established assay based on the PIGA gene. In addition, the L1CAM-based assay allowed us to measure the efficiency of targeted knock-in (correction of L1CAM mutations) accomplished through different strategies, including a Cas9 nuclease-mediated method, tandem paired nicking, and prime editing. Our L1CAM-based assay using FCM enables rapid and sensitive quantification of genome editing efficiencies and will thereby help researchers improve genome editing technologies.

Single-Cell RNA Sequencing (scRNA-seq) Identifies L1CAM as a Key Mediator between Epithelial Tuft Cell and Innate Lymphoid Cell in the Colon of Hnrnp I Knockout Mice

(1) Background: Knockout (KO) of heterogeneous nuclear ribonucleoprotein I (Hnrnp I) in mouse intestinal epithelial cells (IECs) induced a severe inflammatory response in the colon, followed by hyperproliferation. This study aimed to investigate the epithelial lineage dynamics and cell-cell communications that underlie inflammation and colitis. (2) Methods: Single cells were isolated from the colons of wildtype (WT) and KO mice and used in scRNA-seq. Whole colons were collected for immunofluorescence staining and cytokine assays. (3) Results: from scRNA-seq, the number of DCLK1 + colonic tuft cells was significantly higher in the Hnrnp I KO mice compared to the WT mice. This was confirmed by immunofluorescent staining of DCLK1. The DCLK1 + colonic tuft cells in KO mice developed unique communications with lymphocytes via interactions between surface L1 cell adhesion molecule (L1CAM) and integrins. In the KO mice colons, a significantly elevated level of inflammatory cytokines IL4, IL6, and IL13 were observed, which marks type-2 immune responses directed by group 2 innate lymphoid cells (ILC2s). (4) Conclusions: This study demonstrates one critical cellular function of colonic tuft cells, which facilitates type-2 immune responses by communicating with ILC2s via the L1CAM-integrins interaction. This communication promotes pro-inflammatory signaling pathways in ILC2, leading to the increased secretion of inflammatory cytokines.

L1cam alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice

Hirschsprung disease (HSCR) is a congenital disorder of functional bowel obstruction due to the absence of enteric ganglia in distal bowel. Different L1cam variants were reportedly associated with L1cam syndrome and HSCR, whose phenotypes lacked predictable relevance to their genotypes. Using next-generation sequencing (NGS), we found an L1CAM de novo frameshift mutation in a female with mild hydrocephalus and skip-type HSCR. A nearly identical L1cam variant was introduced into FVB/NJ mice via the CRISPR-EZ method. A silent mutation was created via ssODN to gain an artificial Ncol restriction enzyme site for easier genotyping. Six L1cam protein-coding alternative transcripts were quantitatively measured. Immunofluorescence staining with polyclonal and monoclonal L1cam antibodies was used to characterize L1cam isoform proteins in enteric ganglia. Fifteen mice, seven males and eight females, generated via CRISPR-EZ, were confirmed to carry the L1cam frameshift variant, resulting in a premature stop codon. There was no prominent hydrocephalus nor HSCR-like presentation in these mice, but male infertility was noticed after observation for three generations in a total of 176 mice. Full-length L1cam transcripts were detected at a very low level in the intestinal tissues and almost none in the brain of these mice. Alternative shorter transcripts encoding the extracellular domains were overexpressed in the intestine of L1cam knockdown mice. Immunofluorescence confirmed no fulllength L1cam protein in enteric ganglia. These shorter L1cam isoform proteins might play a role in protecting L1cam knockdown mice from HSCR.

L1CAM deployed perivascular tumor niche promotes vessel wall invasion of tumor thrombus and metastasis of renal cell carcinoma

The survival of tumor cells in the bloodstream, and vasculature adhesion at metastatic sites are crucial for tumor metastasis. Perivascular invasion aids tumor cell self-renewal, survival, and formation of metastases by facilitating readily available oxygen, nutrients, and endothelial-derived paracrine factors. Renal cell carcinoma (RCC) is among the most prevalent tumors of the urinary system, and the formation of venous tumor thrombus (VTT) is a characteristic feature of RCC. We observed high expression of L1CAM in the VTT with vessel wall invasion. L1CAM promotes the adhesion, migration, and invasion ability of RCC and enhances metastasis by interacting with ITGA5, which elicits activation of signaling downstream of integrin α5β1. L1CAM promotes ADAM17 transcription to facilitate transmembrane ectodomain cleavage and release of soluble L1CAM. In response to soluble L1CAM, vascular endothelial cells release several cytokines and chemokines. Endothelial-derived CXCL5 and its receptor CXCR2 promote the migration and intravasation of RCC toward endothelial cells suggesting that crosstalk between endothelial cells and tumor cells has a direct guiding role in driving the metastatic spread of RCC. LICAM plays a crucial role in the invasive ability of RCC, and regulation of L1CAM expression may contribute therapeutically to preventing RCC progression.

N-BAR and F-BAR proteins-endophilin-A3 and PSTPIP1-control clathrin-independent endocytosis of L1CAM

Recent advances in the field demonstrate the high diversity and complexity of endocytic pathways. In the current study, we focus on the endocytosis of L1CAM. This glycoprotein plays a major role in the development of the nervous system, and is involved in cancer development and is associated with metastases and poor prognosis. Two L1CAM isoforms are subject to endocytosis: isoform 1, described as a clathrin-mediated cargo; isoform 2, whose endocytosis has never been studied. Deciphering the molecular machinery of isoform 2 internalisation should contribute to a better understanding of its pathophysiological role. First, we demonstrated in our cellular context that both isoforms of L1CAM are mainly a clathrin-independent cargo, which was not expected for isoform 1. Second, the mechanism of L1CAM endocytosis is specifically mediated by the N-BAR domain protein endophilin-A3. Third, we discovered PSTPIP1, an F-BAR domain protein, as a novel actor in this endocytic process. Finally, we identified galectins as endocytic partners and negative regulators of L1CAM endocytosis. In summary, the interplay of the BAR proteins endophilin-A3 and PSTPIP1, and galectins fine tune the clathrin-independent endocytosis of L1CAM.

X-ray structure and function of fibronectin domains two and three of the neural cell adhesion molecule L1

The cell adhesion molecule L1 (L1CAM, L1 in short) plays crucial roles during neural development, regeneration after injury, synapse formation, synaptic plasticity and tumor cell migration. L1 belongs to the immunoglobulin superfamily and comprises in its extracellular part six immunoglobulin (Ig)-like domains and five fibronectin type III homologous repeats (FNs). The second Ig-like domain has been validated for self- (so-called homophilic) binding between cells. Antibodies against this domain inhibit neuronal migration in vitro and in vivo. The fibronectin type III homologous repeats FN2 and FN3 bind small molecule agonistic L1 mimetics and contribute to signal transduction. FN3 has a stretch of 25 amino acids that can be triggered with a monoclonal antibody, or the L1 mimetics, to enhance neurite outgrowth and neuronal cell migration in vitro and in vivo. To correlate the structural features of these FNs with function, we determined a high-resolution crystal structure of a FN2FN3 fragment, which is functionally active in cerebellar granule cells and binds several mimetics. The structure illustrates that both domains are connected by a short linker sequence allowing a flexible and largely independent organization of both domains. This becomes further evident by comparing the X-ray crystal structure with models derived from Small-Angle X-ray Scattering (SAXS) data for FN2FN3 in solution. Based on the X-ray crystal structure, we identified five glycosylation sites which we believe are crucial for folding and stability of these domains. Our study signifies an advance in the understanding of structure-functional relationships of L1.

A review on comparative studies addressing exosome isolation methods from body fluids

Exosomes emerged as valuable sources of disease biomarkers and new therapeutic tools. However, extracellular vesicles isolation with exosome-like characteristics from certain biofluids is still challenging which can limit their potential use in clinical settings. While ultracentrifugation-based procedures are the gold standard for exosome isolation from cell cultures, no unique and standardized method for exosome isolation from distinct body fluids exists. The complexity, specific composition, and physical properties of each biofluid constitute a technical barrier to obtain reproducible and pure exosome preparations, demanding a detailed characterization of both exosome isolation and characterization methods. Moreover, some isolation procedures can affect downstream proteomic or RNA profiling analysis. This review compiles and discussed a set of comparative studies addressing distinct exosome isolation methods from human biofluids, including cerebrospinal fluid, plasma, serum, saliva, and urine, also focusing on body fluid specific challenges, physical properties, and other potential variation sources. This summarized information will facilitate the choice of exosome isolation methods, based on the type of biological samples available, and hopefully encourage the use of exosomes in translational and clinical research.

Extracellular vesicles in the study of Alzheimer's and Parkinson's diseases: Methodologies applied from cells to biofluids

Extracellular vesicles (EVs) are gaining increased importance in fundamental research as key players in disease pathogenic mechanisms, but also in translational and clinical research due to their value in biomarker discovery, either for diagnostics and/or therapeutics. In the first research scenario, the study of EVs isolated from neuronal models mimicking neurodegenerative diseases can open new avenues to better understand the pathological mechanisms underlying these conditions or to identify novel molecular targets for diagnosis and/or therapeutics. In the second research scenario, the easy availability of EVs in body fluids and the specificity of their cargo, which can reflect the cell of origin or disease profiles, turn these into attractive diagnostic tools. EVs with exosome-like characteristics, circulating in the bloodstream and other peripheral biofluids, constitute a non-invasive and rapid alternative to study several conditions, including brain-related disorders. In both cases, several EVs isolation methods are already available, but each neuronal model or biofluid presents its own challenges. Herein, a literature overview on EVs isolation methodologies from distinct neuronal models (cellular culture and brain tissue) and body fluids (serum, plasma, cerebrospinal fluid, urine and saliva) was carried out. Focus was given to approaches employed in the context of Alzheimer's and Parkinson's diseases, and the main research findings discussed. The topics here revised will facilitate the choice of EVs isolation methodologies and potentially prompt new discoveries in EVs research and in the neurodegenerative diseases field.

Functional Diversity of Neuronal Cell Adhesion and Recognition Molecule L1CAM through Proteolytic Cleavage

The neuronal cell adhesion and recognition molecule L1 does not only 'keep cells together' by way of homophilic and heterophilic interactions, but can also promote cell motility when cleaved into fragments by several proteases. It has largely been thought that such fragments are signs of degradation. Now, it is clear that proteolysis contributes to the pronounced functional diversity of L1, which we have reviewed in this work. L1 fragments generated at the plasma membrane are released into the extracellular space, whereas other membrane-bound fragments are internalised and enter the nucleus, thus conveying extracellular signals to the cell interior. Post-translational modifications on L1 determine the sequence of cleavage by proteases and the subcellular localisation of the generated fragments. Inside the neuronal cells, L1 fragments interact with various binding partners to facilitate morphogenic events, as well as regenerative processes. The stimulation of L1 proteolysis via injection of L1 peptides or proteases active on L1 or L1 mimetics is a promising tool for therapy of injured nervous systems. The collective findings gathered over the years not only shed light on the great functional diversity of L1 and its fragments, but also provide novel mechanistic insights into the adhesion molecule proteolysis that is active in the developing and diseased nervous system.

The Signaling Pathways Controlling the Efficacy of Glioblastoma Therapy

The resistance of glioblastoma to existing therapies puts limits on quality-of-life improvements and patient survival with a glioblastoma diagnosis. The development of new effective glioblastoma therapies is based on knowledge about the mechanisms governing tumor resistance to therapeutic agents. Virotherapy is one of the most actively developing approaches to the treatment of malignant neoplasms: glioblastoma in particular. Previously, we demonstrated that the recombinant vaccinia virus VV-GMCSF-Lact exhibits in vitro cytotoxic activity and in vivo antitumor efficacy against human glioblastoma. However, the studied glioblastoma cell cultures had different sensitivities to the oncotoxic effect of the virus. In this study, we investigated cancer stem cell (CSC) surface markers in glioblastoma cells with different sensitivities to VV-GMCSFLact using flow cytometry and we assessed the levels of proteins affecting viral entry into cells and virus infection efficiency by western blotting. We showed that cell cultures more sensitive to VV-GMCSF-Lact are characterized by a greater number of cells with CSC markers and a lower level of activated Akt kinase. Akt probably inhibits lactaptin-induced apoptosis in virus-resistant cells. Hence, we suggest that the sensitivity of glioblastoma cells to the oncotoxic effect of VV-GMCSF-Lact is determined by the nature and extent of the disturbances in cell death regulation in various cultures. Further investigation of the factors affecting glioblastoma resistance to virotherapy will test this hypothesis and identify targets for antitumor therapy, combined with VV-GMCSF-Lact.

Inhibiting L1CAM Reverses Cisplatin Resistance of Triple Negative Breast Cancer Cells by Blocking AKT Signaling Pathway

DDP-resistant MDA-MB-231 cells (MDA-MB-231/DDP) cells had higher expression of L1CAM than their parental cells. L1CAM siRNA decreased the IC50 of MDA-MB-231/DDP cells to DDP. L1CAM inhibition down-regulated p-AKT/AKT in MDA-MB-231/DDP cells; meanwhile, it could promote MDA-MB-231/DDP cell apoptosis, inhibit cell EMT, invasion, and migration. Moreover, SC79 (an AKT activator) increased the DDP-resistance of MDA-MB-231/DDP cells, which was reversed by L1CAM inhibition. Furthermore, co-treatment of L1CAM shRNA and cisplatin injection had better anti-tumor effects in vivo than these two single treatments with decreased p-AKT/AKT. Thus, silencing L1CAM reversed the DDP resistance by inhibiting the AKT pathway.

Prenatal diagnosis of a nonsense mutation in the L1CAM gene resulting in congenital hydrocephalus: A case report and literature review

Congenital hydrocephalus is frequently caused by mutations in the L1 cell adhesion molecule (L1CAM) gene. The purpose of the present study was to identify possible causes of fetal hydrocephalus in a Chinese family. The samples from the parents and the hydrocephalic fetus were collected. Whole-exome sequencing and in-depth mutation analysis were performed. The identified variant, c.1267C>T.(p.Q423X), is situated on exon 11 of L1CAM gene (chromosome X:153134975). The fetus was confirmed to be hemizygous for the nonsense mutation and the mother was a heterozygous carrier. The mutation turns a glutamine into a premature stop codon at amino acid position 423. In conclusion, in the present study, a nonsense mutation in the L1CAM gene was identified during the prenatal diagnosis of a congenital hydrocephalic fetus from a Chinese family. The diagnosis highlighted the necessity of genetic screening for prenatal diagnosis.

L1CAM is not a reliable predictor for lymph node metastases in endometrial cancer, but L1CAM positive patients benefit from radiotherapy

Purpose: Several studies evidenced the potential of L1CAM as a prognostic marker in endometrial cancer. The aim of this study was to investigate whether L1CAM can predict lymph node metastasis and could therefore be used preoperatively to identify patients with low to high-intermediate risk endometrial cancer who would profit from a lymphadenectomy and an adjuvant treatment. To avoid unnecessary morbidity, de-escalating strategies are still required.

Methods: Immunohistochemistry for L1CAM was performed on curettage or hysterectomy specimens from 212 patients diagnosed with endometrial cancer who were treated at the University Hospital Basel during 2011-2019. L1CAM expression was correlated with clinicopathological features such as histological subtype, FIGO stage, lymph node metastasis, lymphadenectomy, adjuvant treatment and outcome.

Results: Using a cut off ≥10%, L1CAM was positive in 41/212 patients (19.3%) and negative in 171/212 patients (80.7%). L1CAM was associated with high-risk features such as non-endometrioid histology, high tumour grade, and high FIGO stage. There was no significant correlation between L1CAM expression and lymph node metastasis. However, patients with L1CAM positive tumours showed improved disease-specific survival if treated with adjuvant radiotherapy.

Conclusion: Although L1CAM expression pointed towards aggressive tumour biology, preoperative L1CAM analysis did not add any substantial predictive information regarding lymph node metastasis in low to high-intermediate risk groups. Therefore, L1CAM status is not suitable to tailor the surgical algorithm for lymph node staging. Nevertheless, our results suggest that L1CAM could be used as a predictive biomarker to select patients who may benefit the most from adjuvant radiotherapy.

L1CAM promotes ovarian cancer stemness and tumor initiation via FGFR1/SRC/STAT3 signaling

BACKGROUND

Cancer stem cells (CSC) have been implicated in tumor progression. In ovarian carcinoma (OC), CSC drive tumor formation, dissemination and recurrence, as well as drug resistance, thus contributing to the high death-to-incidence ratio of this disease. However, the molecular basis of such a pathogenic role of ovarian CSC (OCSC) has been elucidated only to a limited extent. In this context, the functional contribution of the L1 cell adhesion molecule (L1CAM) to OC stemness remains elusive.

METHODS

The expression of L1CAM was investigated in patient-derived OCSC. The genetic manipulation of L1CAM in OC cells provided gain and loss-of-function models that were then employed in cell biological assays as well as in vivo tumorigenesis experiments to assess the role of L1CAM in OC cell stemness and in OCSC-driven tumor initiation. We applied antibody-mediated neutralization to investigate L1CAM druggability. Biochemical approaches were then combined with functional in vitro assays to study the molecular mechanisms underlying the functional role of L1CAM in OCSC.

RESULTS

We report that L1CAM is upregulated in patient-derived OCSC. Functional studies showed that L1CAM promotes several stemness-related properties in OC cells, including sphere formation, tumor initiation and chemoresistance. These activities were repressed by an L1CAM-neutralizing antibody, pointing to L1CAM as a druggable target. Mechanistically, L1CAM interacted with and activated fibroblast growth factor receptor-1 (FGFR1), which in turn induced the SRC-mediated activation of STAT3. The inhibition of STAT3 prevented L1CAM-dependent OC stemness and tumor initiation.

CONCLUSIONS

Our study implicate L1CAM in the tumorigenic function of OCSC and point to the L1CAM/FGFR1/SRC/STAT3 signaling pathway as a novel driver of OC stemness. We also provide evidence that targeting this pathway can contribute to OC eradication.

Neuronally-derived tau is increased in experienced breachers and is associated with neurobehavioral symptoms

Military and law enforcement breachers are exposed to many low-level blasts during their training and occupational experiences in which they detonate explosives to force entry into secured structures. There is a concern that exposure to these repetitive blast events in career breachers could result in cumulative neurological effects. This study aimed to determine concentrations of neurofilament light (NF-L), tau, and amyloid-beta 42 (Aβ42) in serum and in neuronal-derived extracellular vesicles (EVs) in an experienced breacher population, and to examine biomarker associations with neurobehavioral symptoms. Thirty-four participants enrolled in the study: 20 experienced breachers and 14 matched military or civilian law enforcement controls. EV tau concentrations were significantly elevated in experienced breachers (0.3301 ± 0.5225) compared to controls (-0.4279 ± 0.7557; F = 10.43, p = 0.003). No statistically significant changes were observed in EV levels of NF-L or Aβ42 or in serum levels of NF-L, tau, or Aβ42 (p's > 0.05). Elevated EV tau concentrations correlated with increased Neurobehavioral Symptom Inventory (NSI) score in experienced breachers (r = 0.596, p = 0.015) and predicted higher NSI score (F(1,14) = 7.702, p = 0.015, R² = 0.355). These findings show that neuronal-derived EV concentrations of tau are significantly elevated and associated with neurobehavioral symptoms in this sample of experienced breachers who have a history of many low-level blast exposures.

Amelioration of the abnormal phenotype of a new L1 syndrome mouse mutation with L1 mimetics

L1 syndrome is a rare developmental disorder characterized by hydrocephalus of varying severity, intellectual deficits, spasticity of the legs, and adducted thumbs. Therapy is limited to symptomatic relief. Numerous gene mutations in the L1 cell adhesion molecule (L1CAM, hereafter abbreviated L1) were identified in L1 syndrome patients, and those affecting the extracellular domain of this transmembrane type 1 glycoprotein show the most severe phenotypes. Previously analyzed rodent models of the L1 syndrome focused on L1-deficient animals or mouse mutants with abrogated cell surface expression of L1, making it difficult to test L1 function-triggering mimetic compounds with potential therapeutic value. To overcome this impasse, we generated a novel L1 syndrome mouse with a mutation of aspartic acid at position 201 in the extracellular part of L1 (p.D201N, hereafter termed L1-201) that displays a cell surface-exposed L1 accessible to the L1 mimetics. Behavioral assessment revealed an increased neurological deficit score and increased locomotor activity in male L1-201 mice carrying the mutation on the X-chromosome. Histological analyses of L1-201 mice showed features of the L1 syndrome, including enlarged ventricles and reduced size of the corpus callosum. Expression levels of L1-201 protein as well as extent of cell surface biotinylation and immunofluorescence labelling of cultured cerebellar neurons were normal. Importantly, treatment of these cultures with the L1 mimetic compounds duloxetine, crotamiton, and trimebutine rescued impaired cell migration and survival as well as neuritogenesis. Altogether, the novel L1 syndrome mouse model provides a first experimental proof-of-principle for the potential therapeutic value of L1 mimetic compounds.

Molecular characterization of endometrial cancer and therapeutic implications

PURPOSE OF REVIEW

The present article reviews molecular subtyping and genomic characterization of endometrial carcinoma, and the associated therapeutic and prognostic implications.

RECENT FINDINGS

Endometrial cancer has historically been classified through histology into endometrioid and nonendometrioid subtypes with poor prognostic predictability. Molecular classification through genomic analysis now allows for a major advance in characterization. Four distinct subgroups have been identified: polymerase (POLE) ultramutated, microsatellite unstable, copy number-low--microsatellite stable, and copy number-high-'serous-like'. These subtypes have prognostic implications and may aid in the identification of early-stage patients who are at high risk for recurrence. Through analysis of surrogate markers (POLE, MSI, and p53) and other validated molecular alterations (L1CAM), it is possible to obtain an integrated molecular risk profile that relates to prognosis. Studies utilizing this risk profile in order to identify patients who may benefit from adjuvant treatment for early-stage disease are on-going.

SUMMARY

Molecular characterization of endometrial cancer into subgroups has enhanced prognostic and therapeutic implications, contrary to traditional risk stratification. Further development of an integrated molecular risk profile may identify patients who could most benefit from adjuvant treatment following surgery and tailor treatment decisions in the recurrent setting.

Planet of the AAVs: The Spinal Cord Injury Episode

The spinal cord injury (SCI) is a medical and life-disrupting condition with devastating consequences for the physical, social, and professional welfare of patients, and there is no adequate treatment for it. At the same time, gene therapy has been studied as a promising approach for the treatment of neurological and neurodegenerative disorders by delivering remedial genes to the central nervous system (CNS), of which the spinal cord is a part. For gene therapy, multiple vectors have been introduced, including integrating lentiviral vectors and non-integrating adeno-associated virus (AAV) vectors. AAV vectors are a promising system for transgene delivery into the CNS due to their safety profile as well as long-term gene expression. Gene therapy mediated by AAV vectors shows potential for treating SCI by delivering certain genetic information to specific cell types. This review has focused on a potential treatment of SCI by gene therapy using AAV vectors.

The Life of a Trailing Spouse

In 1981, I published a paper in the first issue of the Journal of Neuroscience with my postdoctoral mentor, Alan Pearlman. It reported a quantitative analysis of the receptive field properties of neurons in reeler mouse visual cortex and the surprising conclusion that although the neuronal somas were strikingly malpositioned, their receptive fields were unchanged. This suggested that in mouse cortex at least, neuronal circuits have very robust systems in place to ensure the proper formation of connections. This had the unintended consequence of transforming me from an electrophysiologist into a cellular and molecular neuroscientist who studied cell adhesion molecules and the molecular mechanisms they use to regulate axon growth. It took me a surprisingly long time to appreciate that your science is driven by the people around you and by the technologies that are locally available. As a professional puzzler, I like all different kinds of puzzles, but the most fun puzzles involve playing with other puzzlers. This is my story of learning how to find like-minded puzzlers to solve riddles about axon growth and regeneration.

Ovarian Cancer-Associated Mesothelial Cells: Transdifferentiation to Minions of Cancer and Orchestrate Developing Peritoneal Dissemination

Ovarian cancer has one of the poorest prognoses among carcinomas. Advanced ovarian cancer often develops ascites and peritoneal dissemination, which is one of the poor prognostic factors. From the perspective of the "seed and soil" hypothesis, the intra-abdominal environment is like the soil for the growth of ovarian cancer (OvCa) and mesothelial cells (MCs) line the top layer of this soil. In recent years, various functions of MCs have been reported, including supporting cancer in the OvCa microenvironment. We refer to OvCa-associated MCs (OCAMs) as MCs that are stimulated by OvCa and contribute to its progression. OCAMs promote OvCa cell adhesion to the peritoneum, invasion, and metastasis. Elucidation of these functions may lead to the identification of novel therapeutic targets that can delay OvCa progression, which is difficult to cure.

L1CAM overexpression promotes tumor progression through recruitment of regulatory T cells in esophageal carcinoma

OBJECTIVE

L1 cell adhesion molecule (L1CAM) exhibits oncogenic activity in tumors. However, the link between L1CAM and the tumor microenvironment remains poorly understood in patients with esophageal squamous cell carcinoma (ESCC). In this study, we investigated how L1CAM expression in ESCC affects the oncogenic characteristics of tumor cells and the tumor microenvironment.

METHODS

Human ESCC samples were collected, and the mRNA and protein levels of L1CAM were examined by real-time PCR and immunohistochemistry. Overexpression and knockdown gene expression assays were used for mechanistic studies. The cell proliferation and cell cycle were measured with CCK-8 assays and flow cytometry. Cell migration and invasion ability were measured with Transwell assays. Multiplex bead-based assays were performed to identity the factors downstream of L1CAM. Xenograft studies were performed in nude mice to evaluate the effects of L1CAM on tumor growth and regulatory T cell (Treg) recruitment.

RESULTS

L1CAM expression was significantly elevated in ESCC tissues (P < 0.001) and correlated with poorer prognosis (P < 0.05). Ablation of L1CAM in ESCC cells inhibited tumor growth and migration, and increased tumor cell apoptosis (P < 0.05). In the tumor microenvironment, L1CAM expression correlated with Treg infiltration in ESCC by affecting CCL22 secretion. Mechanistically, L1CAM facilitated CCL22 expression by activating the PI3K/Akt/NF-κB signaling pathway. Furthermore, CCL22 promoted Treg recruitment to the tumor site; the Tregs then secreted TGF-β, which in turn promoted L1CAM expression via Smad2/3 in a positive feedback loop.

CONCLUSIONS

Our findings provide new insight into the mechanism of immune evasion mediated by L1CAM, suggesting that targeting L1CAM-CCL22-TGF-β crosstalk between tumor cells and Tregs may offer a unique means to improve treatment of patients with ESCC.

The 5-HT4 receptor interacts with adhesion molecule L1 to modulate morphogenic signaling in neurons

Morphological remodeling of dendritic spines is critically involved in memory formation and depends on adhesion molecules. Serotonin receptors are also implicated in this remodeling, though the underlying mechanisms remain enigmatic. Here, we uncovered a signaling pathway involving the adhesion molecule L1CAM (L1) and serotonin receptor 5-HT₄ (5-HT₄R, encoded by HTR4). Using Förster resonance energy transfer (FRET) imaging, we demonstrated a physical interaction between 5-HT₄R and L1, and found that 5-HT₄R-L1 heterodimerization facilitates mitogen-activated protein kinase activation in a G_s-dependent manner. We also found that 5-HT₄R-L1-mediated signaling is involved in G₁₃-dependent modulation of cofilin-1 activity. In hippocampal neurons in vitro, the 5-HT₄R-L1 pathway triggers maturation of dendritic spines. Thus, the 5-HT₄R-L1 signaling module represents a previously unknown molecular pathway regulating synaptic remodeling.

X-linked partial corpus callosum agenesis with mild intellectual disability: identification of a novel L1CAM pathogenic variant

Pathogenic variants in L1CAM, the gene encoding the L1 cell adhesion molecule, are responsible for a wide clinical spectrum including X-linked hydrocephalus with stenosis of the Sylvius aqueduct, MASA syndrome (mental retardation, aphasia, shuffling gait, adducted thumbs), and a form of spastic paraplegia (SPG1). A moderate phenotype with mild intellectual disability (ID) and X-linked partial corpus callosum agenesis (CCA) has only been related to L1CAM in one family. We report here a second family, including 5 patients with mild to moderate ID and partial CCA without signs usually associated with L1CAM pathogenic variations (such as hydrocephalus, pyramidal syndrome, thumb adductus, aphasia). We identified a previously unreported c.3226A > C transversion leading to a p.Thr1076Pro amino acid substitution in the fifth fibronectin type III domain (FnIII) of the protein which co-segregates with the phenotype within the family. We performed in vitro assays to assess the pathogenic status of this variation. First, the expression of the novel p.Thr1076Pro mutant in COS7 cells resulted in endoplasmic reticulum (ER) retention and reduced L1CAM cell surface expression, which is expected to affect both L1CAM-mediated cell-cell adhesion and neurite growth. Second, immunoblotting techniques showed that the immature form of the L1CAM protein was increased, indicating that this variation led to a lack of maturation of the protein. ID associated with CCA is not a common clinical presentation of L1CAM pathogenic variants. Genome-wide analyses will identify such variations and it is important to acknowledge this atypical phenotype.

A truncation mutation in the <i>L1CAM</i> gene in a child with hydrocephalus

<abstract> <p>Hydrocephalus is a neurodevelopmental, X-linked recessive disorder caused by mutations in the <italic>L1CAM</italic> gene. The <italic>L1CAM</italic> gene encodes for L1CAM protein which is essential for the nervous system development including adhesion between neurons, Myelination, Synaptogenesis etc. Herein, the present study has reported mutations in L1 syndrome patient with Hydrocephalus and Adducted thumb. Genomic DNA was extracted from patients whole blood (n = 18). The 11 exons of the <italic>L1CAM</italic> gene were amplified using specific PCR primers. The sequenced data was analysed and the pathogenicity of the mutation was predicted using the various bioinformatics programs: PROVEAN, PolyPhen2, and MUpro. The results revealed that the proband described here had nonsense mutation G1120→T at position 1120 in exon 9 which is in extracellular immunoglobulin domain (Ig4) of the <italic>L1CAM</italic> gene. This nonsense mutation is found to be truncated with a deleterious effect on developing brain of the child, and this is the first report of this novel mutation in patient with X-linked Hydrocephalus in India.</p> </abstract>

Circulating Levels of L1-cell Adhesion Molecule as a Serum Biomarker for Early Detection of Gastric Cancer and Esophagogastric Junction Adenocarcinoma

Background: Low serum L1 cell adhesion molecule (L1CAM) has been found in several malignant tumors. Here, we aimed to evaluate the diagnostic potential for serum L1CAM in patients with gastric cancers (GC) and esophagogastric junction adenocarcinoma (EJA). Methods: Enzyme-linked immunosorbent assay (ELISA) was carried out to detect L1CAM level in sera of 148 GC patients, 59 EJA patients and 148 healthy controls. Receiver operating characteristics (ROC) was employed to evaluate diagnostic accuracy. Results: The concentrations of serum L1CAM were significantly lower in GC and EJA than those in healthy controls (P<0.001). Detection of L1CAM provided a sensitivity of 83.1%, a specificity of 62.2%, and an area under the curve (AUC) of 0.769 (95% CI: 0.715-0.823) in diagnosing GC, and a sensitivity of 66.1%, a specificity of 62.2%, and an AUC of 0.672 (95% CI: 0.590-0.755) in diagnosing EJA. Similar results were observed in the diagnosis of early-stage GC (0.681 (95%CI: 0.596-0.766)) and early-stage EJA (0.674 (95%CI: 0.528-0.820)). Analysis of clinical data showed that the levels of L1CAM were significantly associated with lymph node metastasis in GC (P<0.05). Conclusions: Our study showed that serum L1CAM might be a diagnostic biomarker for GC and EJA.

Zwitterionic Polymer Coating Suppresses Microglial Encapsulation to Neural Implants In Vitro and In Vivo

For brain computer interfaces (BCI), the immune response to implanted electrodes is a major biological cause of device failure. Bioactive coatings such as neural adhesion molecule L1 have been shown to improve the biocompatibility, but are difficult to handle or produce in batches. Here, a synthetic zwitterionic polymer coating, poly(sulfobetaine methacrylate) (PSBMA) is developed for neural implants with the goal of reducing the inflammatory host response. In tests in vitro, the zwitterionic coating inhibits protein adsorption and the attachment of fibroblasts and microglia, and remains stable for at least 4 weeks. In vivo two-photon microscopy on CX3CR1-GFP mice shows that the zwitterionic coating significantly suppresses the microglial encapsulation of neural microelectrodes over a 6 h observation period. Furthermore, the lower microglial encapsulation on zwitterionic polymer-coated microelectrodes is revealed to originate from a reduction in the size but not the number of microglial end feet. This work provides a facile method for coating neural implants with zwitterionic polymers and illustrates the initial interaction between microglia and coated surface at high temporal and spatial resolution.

Different Shades of L1CAM in the Pathophysiology of Cancer Stem Cells

L1 cell adhesion molecule (L1CAM) is aberrantly expressed in several tumor types where it is causally linked to malignancy and therapy resistance, acting also as a poor prognosis factor. Accordingly, several approaches have been developed to interfere with L1CAM function or to deliver cytotoxic agents to L1CAM-expressing tumors. Metastatic dissemination, tumor relapse and drug resistance can be fueled by a subpopulation of neoplastic cells endowed with peculiar biological properties that include self-renewal, efficient DNA repair, drug efflux machineries, quiescence, and immune evasion. These cells, known as cancer stem cells (CSC) or tumor-initiating cells, represent, therefore, an ideal target for tumor eradication. However, the molecular and functional traits of CSC have been unveiled only to a limited extent. In this context, it appears that L1CAM is expressed in the CSC compartment of certain tumors, where it plays a causal role in stemness itself and/or in biological processes intimately associated with CSC (e.g., epithelial-mesenchymal transition (EMT) and chemoresistance). This review summarizes the role of L1CAM in cancer focusing on its functional contribution to CSC pathophysiology. We also discuss the clinical usefulness of therapeutic strategies aimed at targeting L1CAM in the context of anti-CSC treatments.

Schwann cell interactions during the development of the peripheral nervous system

Schwann cells play a critical role in the development of the peripheral nervous system (PNS), establishing important relationships both with the extracellular milieu and other cell types, particularly neurons. In this review, we discuss various Schwann cell interactions integral to the proper establishment, spatial arrangement, and function of the PNS. We include signals that cascade onto Schwann cells from axons and from the extracellular matrix, bidirectional signals that help to establish the axo-glial relationship and how Schwann cells in turn support the axon. Further, we speculate on how Schwann cell interactions with other components of the developing PNS ultimately promote the complete construction of the peripheral nerve.

Choline ameliorates ethanol induced alterations in tyrosine phosphorylation and distribution in detergent-resistant membrane microdomains of L1 cell adhesion molecule in vivo

BACKGROUND

Exposure to ethanol during pregnancy is the cause of fetal alcohol spectrum disorder. The function of L1 cell adhesion molecule (L1), critical for proper brain development, is dependent on detergent-resistant membrane microdomains (DRM). Ethanol at low concentrations disrupts L1 function measured by inhibition of downstream signaling and alterations in L1-DRM distribution in cerebellum in vivo and in cerebellar granule neurons (CGN) in vitro. We have previously shown that choline pretreatment of CGN partially prevents ethanol toxicity through improving L1 function in vitro. Here we show that choline supplementation reduces the impact of ethanol on L1 in cerebellum in vivo.

METHODS

Pregnant rat dams were placed on choline free diet on gestational Day 5 (G5). Pups were treated with saline or choline from postnatal day (P) 1-5. On P5, pups were intubated twice 2 hr apart with ethanol or Intralipid® for a total dose of 6 g/kg/d and sacrificed 1 hr after the last intubation. The cerebella were harvested and L1 phosphorylation/dephosphorylation status and distribution in DRM were analyzed.

RESULTS

Ethanol reduced L1 tyrosine phosphorylation and L1-Y1176 dephosphorylation in cerebella, and caused an increase in the percent of L1 in DRM. Choline supplementation of pups reduced the ethanol-induced changes in L1 phosphorylation status and ameliorated ethanol-induced redistribution of L1 into DRM.

CONCLUSION

Choline supplementation before an acute dose of ethanol ameliorates changes in L1 in vivo.

The Diagnostic Value of Serum L1CAM in Patients With Colorectal Cancer

OBJECTIVE

Colorectal cancer is one of the most important malignant cancer in the world with high incidence and mortality. Some studies have found that the expression of low serum L1 cell adhesion molecule is associated with poor prognosis in some malignancies. It is suggested that L1 cell adhesion molecule is a candidate serum marker for certain tumors. However, the relationship between serum L1 cell adhesion molecule and colorectal cancer, especially about the diagnostic value, is rarely reported. Therefore, this study aimed to evaluate the diagnostic potential of serum L1 cell adhesion molecule in patients with colorectal cancer.

METHODS

Enzyme-linked immunosorbent assay was carried out to detect L1 cell adhesion molecule level in sera of 229 patients with colorectal cancer and 145 normal controls. Receiver operating characteristic curves were employed to calculate the accuracy of diagnosis.

RESULTS

The levels of serum L1 cell adhesion molecule in the colorectal cancer group were significantly lower than that in normal controls (P < .05). In the normal group, the area under the receiver operating characteristic curve (area under the curve) of all colorectal cancer was 0.781 (95% confidence interval: 0.734-0.828) and early-stage colorectal cancer was 0.764 (95% confidence interval: 0.705-0.823). With optimized cutoff of 17.760 ng/mL, L1 cell adhesion molecule showed certain diagnostic value with specificity of 90.3% and sensitivities of 43.2% and 36.2% in colorectal cancer and early-stage colorectal cancer, respectively. Clinical data analysis showed that the levels of L1 cell adhesion molecule were significantly correlated with gender (P < .05) and early and late stages (P < .05). Furthermore, when compared with carcinoembryonic antigen, serum L1 cell adhesion molecule had significantly improved diagnostic accuracy for both colorectal cancer and early-stage colorectal cancer.

CONCLUSIONS

Our study demonstrated that serum L1 cell adhesion molecule might be served as a potential biomarker for the diagnosis of colorectal cancer.

Molecular characterization of endometrial cancer and therapeutic implications

PURPOSE OF REVIEW

The present article reviews genomic subtyping of endometrial carcinoma and new molecular markers with therapeutic and prognostic implications.

RECENT FINDINGS

Endometrial cancer has historically been classified through histology into endometrioid (type 1) and nonendometrioid (type II, mainly serous) subtypes. Molecular classification through genomic analysis now allows for a major advance in characterization; four distinct subgroups have been identified: polymerase ε (POLE) ultramutated, microsatellite unstable, copy number low/microsatellite stable, and copy number high/'serous-like'. These subtypes have prognostic implications and may aid in the identification of early-stage patients who are at high risk for recurrence. Through analysis of surrogate markers (POLE, MSI, and p53) and other validated molecular alterations (L1CAM), it may be possible to obtain an integrated molecular risk profile. Ongoing studies are utilizing this risk profile in order to identify patients who may benefit from additional treatment for early-stage disease.

SUMMARY

Molecular characterization of endometrial cancer into subgroups has prognostic and therapeutic implications. Further development of an integrated molecular risk profile may identify patients who could benefit from additional treatment because of a higher risk of recurrence.

A new frameshift mutation in L1CAM producing X-linked hydrocephalus

Background

X‐linked hydrocephalus (XLH), characterized by mental retardation and bilateral adducted thumbs, often come out to be a genetic disorder of L1CAM. It codes the protein L1 cell adhesion molecule (L1CAM), playing a crucial role in the development of the nervous system. The objective of the study was to report a new disease‐causing mutation site of L1CAM, and gain further insight into the pathophysiology of hydrocephalus.

Methods

We collect the samples of a couple and their second hydrocephalic fetus. Then, the whole‐exome sequencing and in‐depth mutation analysis were performed.

Results

The variant c.2491delG (p.V831fs), located in the exon 19 of L1CAM (chrX:153131214), could damage the L1CAM function by producing a frameshift in the translation of fibronectin type‐III of L1CAM.

Conclusion

We identified a novel disease‐causing mutation in L1CAM for the first time, which further confirmed L1CAM as a gene underlying XLH cases.

L1 Cell Adhesion Molecule in Cancer, a Systematic Review on Domain-Specific Functions

L1 cell adhesion molecule (L1CAM) is a glycoprotein involved in cancer development and is associated with metastases and poor prognosis. Cellular processing of L1CAM results in expression of either full-length or cleaved forms of the protein. The different forms of L1CAM may localize at the plasma membrane as a transmembrane protein, or in the intra- or extracellular environment as cleaved or exosomal forms. Here, we systematically analyze available literature that directly relates to L1CAM domains and associated signaling pathways in cancer. Specifically, we chart its domain-specific functions in relation to cancer progression, and outline pre-clinical assays used to assess L1CAM. It is found that full-length L1CAM has both intracellular and extracellular targets, including interactions with integrins, and linkage with ezrin. Cellular processing leading to proteolytic cleavage and/or exosome formation results in extracellular soluble forms of L1CAM that may act through similar mechanisms as compared to full-length L1CAM, such as integrin-dependent signals, but also through distinct mechanisms. We provide an algorithm to guide a step-wise analysis on L1CAM in clinical samples, to promote interpretation of domain-specific expression. This systematic review infers that L1CAM has an important role in cancer progression that can be attributed to domain-specific forms. Most studies focus on the full-length plasma membrane L1CAM, yet knowledge on the domain-specific forms is a prerequisite for selective targeting treatment.

Ectopic expression of L1CAM ectodomain alters differentiation and motility, but not proliferation, of human neural progenitor cells

Adult human neural progenitor and stem cells have been implicated as a potential source of brain cancer causing cells, but specific events that might cause cells to progress towards a transformed phenotype remain unclear. The L1CAM (L1) cell adhesion/recognition molecule is expressed abnormally by human glioma cancer cells and is released as a large extracellular ectodomain fragment, which stimulates cell motility and proliferation. This study investigates the effects of ectopic overexpression of the L1 long ectodomain (L1LE; ˜180 kDa) on the motility, proliferation, and differentiation of human neural progenitor cells (HNPs). L1LE was ectopically expressed in HNPs using a lentiviral vector. Surprisingly, overexpression of L1LE resulted in reduced HNP motility in vitro, in stark contrast to the effects on glioma and other cancer cell types. L1LE overexpression resulted in a variable degree of maintenance of HNP proliferation in media without added growth factors but did not increase proliferation. In monolayer culture, HNPs expressed a variety of differentiation markers. L1LE overexpression resulted in loss of glutamine synthetase (GS) and β3-tubulin expression in normal HNP media, and reduced vimentin and increased GS expression in the absence of added growth factors. When co-cultured with chick embryonic brain cell aggregates, HNPs show increased differentiation potential. Some HNPs expressed p-neurofilaments and oligodendrocytic O4, indicating differentiation beyond that in monolayer culture. Most HNP-L1LE cells lost their vimentin and GFAP (glial fibrillary acidic protein) staining, and many cells were positive for astrocytic GS. However, these cells rarely were positive for neuronal markers β3-tubulin or p-neurofilaments, and few HNP oligodendrocyte progenitors were found. These results suggest that unlike for glioma cells, L1LE does not increase HNP cell motility, but rather decreases motility and influences the differentiation of normal brain progenitor cells. Therefore, the effect of L1LE on increasing motility and proliferation appears to be limited to already transformed cells.

Proteogenomics Uncovers Critical Elements of Host Response in Bovine Soft Palate Epithelial Cells Following In Vitro Infection with Foot-And-Mouth Disease Virus

Foot-and-mouth disease (FMD) is the most devastating disease of cloven-hoofed livestock, with a crippling economic burden in endemic areas and immense costs associated with outbreaks in free countries. Foot-and-mouth disease virus (FMDV), a picornavirus, will spread rapidly in naïve populations, reaching morbidity rates of up to 100% in cattle. Even after recovery, over 50% of cattle remain subclinically infected and infectious virus can be recovered from the nasopharynx. The pathogen and host factors that contribute to FMDV persistence are currently not understood. Using for the first time primary bovine soft palate multilayers in combination with proteogenomics, we analyzed the transcriptional responses during acute and persistent FMDV infection. During the acute phase viral RNA and protein was detectable in large quantities and in response hundreds of interferon-stimulated genes (ISG) were overexpressed, mediating antiviral activity and apoptosis. Although the number of pro-apoptotic ISGs and the extent of their regulation decreased during persistence, some ISGs with antiviral activity were still highly expressed at that stage. This indicates a long-lasting but ultimately ineffective stimulation of ISGs during FMDV persistence. Furthermore, downregulation of relevant genes suggests an interference with the extracellular matrix that may contribute to the skewed virus-host equilibrium in soft palate epithelial cells.

Diagnostic and prognostic value of serum L1-cell adhesion molecule in esophageal squamous cell carcinoma

OBJECTIVE

L1 cell adhesion molecule (L1CAM) has been found to be dysregulated in several types of human cancers. Here, we aimed to determine the level of soluble L1CAM in serum of patients with esophageal squamous cell carcinoma (ESCC).

METHODS

Serum levels of L1CAM were determined by an enzyme-linked immunosorbent assay (ELISA) in 191 patients with ESCC and 94 normal controls. Receiver operating characteristics (ROC) was employed to calculate diagnostic accuracy. Cumulative survival time was calculated by the Kaplan-Meier method and analyzed by the logrank test.

RESULTS

Levels of L1CAM were significantly lower in all ESCC patients than in normal controls (P < 0.001). Detection of serum L1CAM provided a sensitivity of 28.3%, a specificity of 90.4% and an area under the curve (AUC) of 0.644 (95% CI: 0.579-0.710) in diagnosing ESCC. Similar results were observed in the diagnosis of early-stage ESCC (26.2% sensitivity, 90.4% specificity, and an AUC of 0.629). Moreover, decreased level of L1CAM was correlated with depth of tumor invasion (P < 0.05). Kaplan-Meier analysis showed that lower serum L1CAM level was significantly related to shorter overall survival time (P = 0.036) and disease-free survival time (P = 0.021) of ESCC patients.

CONCLUSIONS

Our study demonstrated that serum L1CAM might serve as a potential biomarker for the diagnosis and prognosis of ESCC.

Increased L1CAM (CD171) levels are associated with glioblastoma and metastatic brain tumors

L1 cell adhesion molecule (L1CAM) is a member of the immunoglobulin-like cell-adhesion molecule family that was shown to be associated with a worse prognosis in several human cancers. L1 ectodomain shedding via vesicles or exosomes has been detected in extracellular fluids after cleavage from the cell surface by metalloproteases. We evaluated the presence of L1CAM in cyst fluid and tissue from glioblastomas or brain metastases.The amount of L1CAM in cyst fluid of 9 glioblastomas and 11 brain metastases was assessed using enzyme-linked immunosorbent assay (ELISA). Corresponding tumor tissue slices were stained immunohistochemically for L1CAM. Cerebrospinal fluid of 20 non-tumor patients served as controls.Mean levels of L1CAM in tumor cyst fluid were significantly higher in glioblastoma (6118 ± 4095 ng/mL) and metastasis patients (8001 ± 6535 ng/mL) than in CSF of control patients (714 ± 22 ng/mL). The immunohistochemical expression of L1CAM in corresponding tissue was significantly higher in metastases than in glioblastomas.The present study demonstrates high levels of L1CAM in cyst fluid of glioblastoma and metastatic brain tumors. Soluble L1CAM may represent a motility promoting molecule in cancer progression, a co-factor for development of tumor cysts and a target for new treatment strategies.

Expression of neural cell adhesion molecule L1 (CD171) in neuroectodermal and other tumors: An immunohistochemical study of 5155 tumors and critical evaluation of CD171 prognostic value in gastrointestinal stromal tumors

The neural cell adhesion molecule L1 (CD171) is a multidomain type 1 membrane glycoprotein of the immunoglobulin superfamily important in the nervous system development, kidney morphogenesis, and maintenance of the immune system. Recent studies reported CD171 expression being associated with adverse clinical outcome in different types of cancer and there has been a growing interest in targeting this cell membrane molecule on neoplastic cells by chimeric antigen receptor redirected T lymphocytes or specific antibodies. Nevertheless, conflicting results regarding the prognostic value of CD171 expression in renal cell carcinomas and gastrointestinal stromal tumors were published. In this study, CD171 expression was immunohistochemically analyzed in 5155 epithelial, mesenchymal, melanocytic, and lymphohematopoietic tumors to assess its utility in diagnostic pathology and to pinpoint potential targets for CD171-targeting therapy. A newly developed anti-CD171 rabbit monoclonal antibody, clone 014, was selected from the panel of commercially available CD171 antibodies. Immunohistochemistry was performed using Leica Bond Max automation and multitumor blocks containing up to 60 tumor samples. CD171 was constitutively and strongly expressed in neuroectodermal tumors such as schwannoma, neuroblastoma, and paraganglioma, whereas other mesenchymal tumors including schwannoma mimics showed only rarely CD171 positivity. Frequent CD171-expression was also detected in ovarian serous carcinoma, malignant mesothelioma, and testicular embryonal carcinoma. CD171 immunohistochemistry may have some role in immunophenotypic differential diagnosis of neurogenic tumors and pinpointing potential candidates for anti-CD171 therapy. Though, because of its rare expression and lack of predictive value, CD171 is neither a diagnostic nor prognostic marker for gastrointestinal stromal tumors.

Knockdown of L1CAM significantly reduces metastasis in a xenograft model of human melanoma: L1CAM is a potential target for anti-melanoma therapy

Finding additional functional targets for combination therapy could improve the outcome for melanoma patients. In a spontaneous metastasis xenograft model of human melanoma a shRNA mediated knockdown of L1CAM more than sevenfold reduced the number of lung metastases after the induction of subcutaneous tumors for two human melanoma cell lines (MeWo, MV3). Whole genome expression arrays of the initially L1CAM high MeWo subcutaneous tumors revealed unchanged or downregulated genes involved in epithelial to mesenchymal transition (EMT) except an upregulation of Jagged 1, indicating a compensatory change in Notch signaling especially as Jagged 1 expression showed an increase in MeWo L1CAM metastases and Jagged 1 was expressed in metastases of the initially L1CAM low MV3 cells as well. Expression of 17 genes showed concordant regulation for L1CAM knockdown tumors of both cell lines. The changes in gene expression indicated changes in the EMT network of the melanoma cells and an increase in p53/p21 and p38 activity contributing to the reduced metastatic potential of the L1CAM knockdowns. Taken together, these data make L1CAM a highly interesting therapeutic target to prevent further metastatic spread in melanoma patients.

Clinical impact of L1CAM expression measured on the transcriptome level in ovarian cancer

Background

High expression of L1 cell adhesion molecules (L1CAM) has been repeatedly shown to be associated with aggressive disease behavior, which translates in poor clinical outcome in various cancer entities. However, in ovarian cancer results based either on immunohistochemistry or cytosolic protein quantifications remained conflicting regarding clinical behavior. In the present work we assessed L1CAM expression on the transcriptome level with the highly sensitive quantitative real-time PCR (qRT-PCR) to define its relevance in ovarian cancer biology.

Results

There was a significant difference in L1CAM high and low mRNA expressing cancers with regard to disease-free (p=0.002) and overall survival (p=0.008). L1CAM proofed to be an independent predictor for disease progression (HR 1.8, p=0.01) and overall survival (HR 1.6, p=0.04). Furthermore, a significant positive correlation between the level of L1CAM and the grade of tumor differentiation (p=0.04), the FIGO stage (p=0.025) as well as the histological subtype (p= 0.002) was found.

Methods

This study included fresh frozen tissue samples of 138 patients with FIGO I-IV stage ovarian cancer. L1CAM mRNA expression was determined using qRT-PCR. In the calculations special attention was put on the various histological subtypes. In survival analysis median L1CAM mRNA expression obtained in the entire cohort of ovarian cancer samples was used as a cut-off to distinguish between high and low L1CAM mRNA expression.

Conclusion

L1CAM mRNA expression appears to play a substantial role in the pathophysiology of ovarian cancer that is translated into poor clinical outcome. Additionally humanized L1CAM antibodies, which can serve as potential future treatment options are under testing.

L1CAM drives oncogenicity in esophageal squamous cell carcinoma by stimulation of ezrin transcription

L1 cell adhesion molecule (L1CAM) is highly expressed in various types of human cancers, displaying yet unknown molecular mechanisms underlying their oncogenic potential. Here, we found that L1CAM expression was significantly increased in esophageal squamous cell carcinoma (ESCC; n = 157) lesions compared with non-cancerous tissues. High tumorous L1CAM expression significantly correlated with reduced overall survival. Experimentally, L1CAM knockdown led to decreased cell growth, migration, and invasiveness in vitro, whereas overexpression of L1CAM showed the opposite effect. In nude mice, L1CAM depletion attenuated tumorigenesis and ability to penetrate the tissues surrounding ESCC cells. Gene set enrichment analysis (GSEA) and SubpathwayMiner analysis on gene expression profiles (microarray data on ESCC tissues, GSE53625; cDNA microarray data on L1CAM-knockdown ESCC cell line, GSE86268) suggested that L1CAM-co-expression genes were related to cell motility, cell proliferation, and regulation of actin cytoskeleton, validating the above experimental findings. Further mechanistical analysis showed that L1CAM upregulated the expression of the cytoskeletal protein ezrin via activating integrin β1/MAPK/ERK/AP1 signaling and thus led to the malignant phenotypes of ESCC cells. Together, our findings suggest that L1CAM may be employed as a valuable prognosis marker and a therapeutic target for ESCC patients and that L1CAM promotes ESCC tumorigenicity by upregulating ezrin expression.

KEY MESSAGES

L1CAM promotes growth and invasiveness of ESCC cells in vitro and in vivo. L1CAM upregulates the expression of ezrin by integrin α5β1/MAPK/ERK/AP1 pathway. Ezrin is a key downstream effector in the L1CAM-promoted malignant phenotypes. High expression levels of both L1CAM and ezrin significantly correlated with reduced overall survival. Nuclear L1CAM is an independent prognosis marker for esophageal squamous cell carcinoma.