The Cell Adhesion Molecule Necl-4/CADM4 Serves as a Novel Regulator for Contact Inhibition of Cell Movement and Proliferation

The Role of Mechanotransduction in Contact Inhibition of Locomotion and Proliferation

Contact inhibition (CI) represents a crucial tumor-suppressive mechanism responsible for controlling the unbridled growth of cells, thus preventing the formation of cancerous tissues. CI can be further categorized into two distinct yet interrelated components: CI of locomotion (CIL) and CI of proliferation (CIP). These two components of CI have historically been viewed as separate processes, but emerging research suggests that they may be regulated by both distinct and shared pathways. Specifically, recent studies have indicated that both CIP and CIL utilize mechanotransduction pathways, a process that involves cells sensing and responding to mechanical forces. This review article describes the role of mechanotransduction in CI, shedding light on how mechanical forces regulate CIL and CIP. Emphasis is placed on filamin A (FLNA)-mediated mechanotransduction, elucidating how FLNA senses mechanical forces and translates them into crucial biochemical signals that regulate cell locomotion and proliferation. In addition to FLNA, trans-acting factors (TAFs), which are proteins or regulatory RNAs capable of directly or indirectly binding to specific DNA sequences in distant genes to regulate gene expression, emerge as sensitive players in both the mechanotransduction and signaling pathways of CI. This article presents methods for identifying these TAF proteins and profiling the associated changes in chromatin structure, offering valuable insights into CI and other biological functions mediated by mechanotransduction. Finally, it addresses unanswered research questions in these fields and delineates their possible future directions.

Nectins and Nectin-like molecules drive vascular development and barrier function

Angiogenesis, barriergenesis, and immune cell migration are all key physiological events that are dependent on the functional characteristics of the vascular endothelium. The protein family of Nectins and Nectin-like molecules (Necls) is a group of cell adhesion molecules that are widely expressed by different endothelial cell types. The family includes four Nectins (Nectin-1 to -4) and five Necls (Necl-1 to -5) that either interact with each other by forming homo- and heterotypical interactions or bind to ligands expressed within the immune system. Nectin and Necl proteins are mainly described to play a role in cancer immunology and in the development of the nervous system. However, Nectins and Necls are underestimated players in the formation of blood vessels, their barrier properties, and in guiding transendothelial migration of leukocytes. This review summarizes their role in supporting the endothelial barrier through their function in angiogenesis, cell-cell junction formation, and immune cell migration. In addition, this review provides a detailed overview of the expression patterns of Nectins and Necls in the vascular endothelium.

Clinicopathological Significance of Cell Adhesion Molecule 4 Expression in Gallbladder Cancer and Its Prognostic Role

Cell adhesion molecule 4 (CADM4) is involved in intercellular interactions and is a tumor-suppressor candidate. The role of CADM4 in gallbladder cancer (GBC) has not been reported. Therefore, the clinicopathological significance and prognostic value of CADM4 expression in GBC were evaluated in the present study. Immunohistochemistry (IHC) was performed on 100 GBC tissues to assess CADM4 expression at the protein level. The association between CADM4 expression and the clinicopathological characteristics of GBC was analyzed, and the prognostic significance of CADM4 expression was evaluated. Low CADM4 expression was significantly associated with advanced T category (p = 0.010) and high AJCC stage (p = 0.019). In a survival analysis, low CADM4 expression was associated with shorter overall survival (OS; p = 0.001) and recurrence-free survival (RFS; p = 0.018). In univariate analyses, low CADM4 expression was associated with shorter OS (p = 0.002) and RFS (p = 0.023). In multivariate analyses, low CADM4 expression was an independent prognostic factor of OS (p = 0.013). Low CADM4 expression was associated with tumor invasiveness and poor clinical outcomes in patients with GBC. CADM4 may play an important role in cancer progression and patient survival and can be used as a potential prognostic marker of GBC.

The Drp1-Mediated Mitochondrial Fission Protein Interactome as an Emerging Core Player in Mitochondrial Dynamics and Cardiovascular Disease Therapy

Mitochondria, the membrane-bound cell organelles that supply most of the energy needed for cell function, are highly regulated, dynamic organelles bearing the ability to alter both form and functionality rapidly to maintain normal physiological events and challenge stress to the cell. This amazingly vibrant movement and distribution of mitochondria within cells is controlled by the highly coordinated interplay between mitochondrial dynamic processes and fission and fusion events, as well as mitochondrial quality-control processes, mainly mitochondrial autophagy (also known as mitophagy). Fusion connects and unites neighboring depolarized mitochondria to derive a healthy and distinct mitochondrion. In contrast, fission segregates damaged mitochondria from intact and healthy counterparts and is followed by selective clearance of the damaged mitochondria via mitochondrial specific autophagy, i.e., mitophagy. Hence, the mitochondrial processes encompass all coordinated events of fusion, fission, mitophagy, and biogenesis for sustaining mitochondrial homeostasis. Accumulated evidence strongly suggests that mitochondrial impairment has already emerged as a core player in the pathogenesis, progression, and development of various human diseases, including cardiovascular ailments, the leading causes of death globally, which take an estimated 17.9 million lives each year. The crucial factor governing the fission process is the recruitment of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, from the cytosol to the outer mitochondrial membrane in a guanosine triphosphate (GTP)-dependent manner, where it is oligomerized and self-assembles into spiral structures. In this review, we first aim to describe the structural elements, functionality, and regulatory mechanisms of the key mitochondrial fission protein, Drp1, and other mitochondrial fission adaptor proteins, including mitochondrial fission 1 (Fis1), mitochondrial fission factor (Mff), mitochondrial dynamics 49 (Mid49), and mitochondrial dynamics 51 (Mid51). The core area of the review focuses on the recent advances in understanding the role of the Drp1-mediated mitochondrial fission adaptor protein interactome to unravel the missing links of mitochondrial fission events. Lastly, we discuss the promising mitochondria-targeted therapeutic approaches that involve fission, as well as current evidence on Drp1-mediated fission protein interactions and their critical roles in the pathogeneses of cardiovascular diseases (CVDs).

Decreased Expression of Cell Adhesion Molecule 4 in Gastric Adenocarcinoma and Its Prognostic Implications

Cell adhesion molecule 4 (CADM4) is a novel tumor suppressor candidate. The prognostic implications of CADM4 in gastric cancer have not been conclusively elucidated. Therefore, we evaluated the clinicopathological significance and prognostic value of CADM4 expression in a large series of patients with gastric adenocarcinoma. Immunohistochemical staining for CADM4 was performed on 534 gastric adenocarcinomas. We evaluated the associations between CADM4 expression and the clinicopathological and molecular characteristics of the adenocarcinomas. The prognostic effect of CADM4 expression was evaluated by survival analyses. Low CADM4 expression was significantly associated with young age (p = 0.046), aggressive histological type (p < 0.001), high pT category (p < 0.001), nodal metastasis (p < 0.001), high stage (p = 0.002), lymphovascular invasion (p = 0.001), and perineural invasion (p = 0.001). Low CADM4 expression was more frequently observed in tumors without human epidermal growth factor receptor 2 (HER2) amplification (p = 0.002). Low CADM4 expression was associated with worse overall survival (p = 0.007) and recurrence-free survival (p = 0.005) in the survival analyses. Low CADM4 expression was associated with aggressive clinicopathological features and poor clinical outcomes. CADM4 can act as a tumor suppressor in gastric adenocarcinoma and can be considered a prognostic biomarker.

Biomimetic Scaffolds Modulate the Posttraumatic Inflammatory Response in Articular Cartilage Contributing to Enhanced Neoformation of Cartilaginous Tissue In Vivo

Focal chondral lesions of the knee are the most frequent type of trauma in younger patients and are associated with a high risk of developing early posttraumatic osteoarthritis. The only current clinical solutions include microfracture, osteochondral grafting, and autologous chondrocyte implantation. Cartilage tissue engineering based on biomimetic scaffolds has become an appealing strategy to repair cartilage defects. Here, a chondrogenic collagen-chondroitin sulfate scaffold is tested in an orthotopic Lapine in vivo model to understand the beneficial effects of the immunomodulatory biomaterial on the full chondral defect. Using a combination of noninvasive imaging techniques, histological and whole transcriptome analysis, the scaffolds are shown to enhance the formation of cartilaginous tissue and suppression of host cartilage degeneration, while also supporting tissue integration and increased tissue regeneration over a 12 weeks recovery period. The results presented suggest that biomimetic materials could be a clinical solution for cartilage tissue repair, due to their ability to modulate the immune environment in favor of regenerative processes and suppression of cartilage degeneration.

Expression of cell adhesion molecule 1 in human and murine endometrial glandular cells and its increase during the proliferative phase by estrogen and cell density

AIMS

Cell adhesion molecule 1 (CADM1) mediates interepithelial adhesion and is upregulated in crowded epithelial monolayers. This study aimed to examine CADM1 expression in the human endometrium of proliferative and secretory phases, and its transcriptional regulation in terms of estrogen stimuli and higher cellularity.

MAIN METHODS

CADM1 immunohistochemistry was conducted on endometrial tissues from women in their 40s and adult mice subcutaneously injected with estradiol following ovariectomy. Dual-luciferase reporter assays were conducted using human endometrial HEC-50B and HEC-1B cells and reporter plasmids harboring the human CADM1 3.4-kb promoter and its deleted and mutated forms. Cells were transfected with estrogen receptor α cDNA and reporter plasmids, and treated with estradiol before luciferase activity measurement.

KEY FINDINGS

Immunohistochemistry revealed that CADM1 was clearly expressed on the lateral membranes of the simple columnar glandular cells in the proliferative phase, but not in the secretory phase, from both women and the mouse model. The glandular cell density increased two-fold in the proliferative phase. Reporter assays identified three Sp1-binding sites as estradiol-responsive elements in the proximal region (from -223 to -84) of the transcription start site (+1) in HEC-50B cells. When the cell culture was started at eight-fold higher cell density, the CADM1 3.4-kb promoter was transactivated at a two-fold higher level in HEC-50B cells. This cell density effect was not detected for the CADM1 2.3-kb or 1.6-kb promoter.

SIGNIFICANCE

Two (proximal and distal) promoter regions are suggested to function additively to transactivate CADM1 in endometrial glandular cells that crowd in the proliferative phase.

Emerging roles of the nectin family of cell adhesion molecules in tumour-associated pathways

Tumour cells achieve maximum survival by modifying cellular machineries associated with processes such as cell division, migration, survival, and apoptosis, resulting in genetically complex and heterogeneous populations. While nectin and nectin-like cell adhesion molecules control development and maintenance of multicellular organisation in higher vertebrates by mediating cell-cell adhesion and related signalling processes, recent studies indicate that they also critically regulate growth and development of different types of cancers. In this review, we detail current knowledge about the role of nectin family members in various tumours. Furthermore, we also analyse the seemingly opposing roles of some members of nectin family in tumour-associated pathways, as they function as both tumour suppressors and oncogenes. Understanding this functional duality of nectin family in tumours will further our knowledge of molecular mechanisms regulating tumour development and progression, and contribute to the advancement of tumour diagnosis and therapy.

Cell adhesion molecule 4 suppresses cell growth and metastasis by inhibiting the Akt signaling pathway in non-small cell lung cancer

Cell adhesion molecule 4 (CADM4) is downregulated in many human cancers. However, CADM4 expression levels in human non-small cell lung cancer (NSCLC) tissues and its roles in NSCLC progression remain unknown. Our study aims to address these issues. We examined CADM4 levels in NSCLC tissues using real-time PCR and western blot. A549 and NCI-H1299 cells were then transfected with pcDNA3.1-CADM4 plasmid or siCADM4 to overexpress or knock down CADM4. Cell proliferation, cell cycle distribution, migration, and invasion were evaluated. NSCLC cells transfected with pcDNA3.1-CADM4 plasmid or siCADM4 were treated with SC79 or LY294002, respectively, to investigate the involvement of the Akt signaling pathway. Male nude mice were subcutaneously injected with stably transfected cells (1 × 10⁶ cells/mice) to observe tumor growth. Stable transfectants were injected into nude mice (1 × 10⁶ cells/mice) via tail vein to observe tumor metastasis. The results showed that CADM4 gene and protein levels in NSCLC tissues were significantly lower than those in corresponding adjacent tissues. CADM4 overexpression markedly inhibited cell proliferation, migration, and invasion. We also found that matrix metalloproteinase 9 (MMP-9) and MMP-2 activities were reduced. Moreover, CADM4 overexpression arrested the cell cycle at G1 phase, with the changes in expression of cell cycle regulators. The Akt signaling pathway was inhibited by CADM4 overexpression. In contrast, CADM4 knockdown showed the opposite effects. Additionally, SC79 and LY294002 reversed the effects of CADM4 overexpression and CADM4 knockdown in vitro, respectively. In xenograft models, CAMD4 overexpression suppressed, while CADM4 knockdown promoted tumor growth, accompanied by changes in Ki67 expression. In in vivo metastasis assay, CADM4 overexpression decreased, while CADM4 knockdown increased numbers of metastatic nodules in lung and liver. These evidences suggest that CADM4 may regulate NSCLC progression via the Akt signaling pathway. CADM4 may be a potential therapeutic target for NSCLC.

PTPN13 induces cell junction stabilization and inhibits mammary tumor invasiveness

Clinical data suggest that the protein tyrosine phosphatase PTPN13 exerts an anti-oncogenic effect. Its exact role in tumorigenesis remains, however, unclear due to its negative impact on FAS receptor-induced apoptosis.

Methods: We crossed transgenic mice deleted for PTPN13 phosphatase activity with mice that overexpress human HER2 to assess the exact role of PTPN13 in tumor development and aggressiveness. To determine the molecular mechanism underlying the PTPN13 tumor suppressor activity we developed isogenic clones of the aggressive human breast cancer cell line MDA-MB-231 overexpressing either wild type or a catalytically-inactive mutant PTPN13 and subjected these to phosphoproteomic and gene ontology analyses.

We investigated the PTPN13 consequences on cell aggressiveness using wound healing and Boyden chamber assays, on intercellular adhesion using videomicroscopy, cell aggregation assay and immunofluorescence.

Results: The development, growth and invasiveness of breast tumors were strongly increased by deletion of the PTPN13 phosphatase activity in transgenic mice. We observed that PTPN13 phosphatase activity is required to inhibit cell motility and invasion in the MDA-MB-231 cell line overexpressing PTPN13. In vivo, the negative PTPN13 effect on tumor invasiveness was associated with a mesenchymal-to-epithelial transition phenotype in athymic mice xenografted with PTPN13-overexpressing MDA-MB-231 cells, as well as in HER2-overexpressing mice with wild type PTPN13, compared to HER2-overexpressing mice that lack PTPN13 phosphatase activity. Phosphoproteomic and gene ontology analyses indicated a role of PTPN13 in the regulation of intercellular junction-related proteins. Finally, protein localization studies in MDA-MB-231 cells and HER2-overexpressing mice tumors confirmed that PTPN13 stabilizes intercellular adhesion and promotes desmosome formation.

Conclusions: These data provide the first evidence for the negative role of PTPN13 in breast tumor invasiveness and highlight its involvement in cell junction stabilization.

Nectin-4 cis-interacts with ErbB2 and its trastuzumab-resistant splice variants, enhancing their activation and DNA synthesis

Nectin-4 cell adhesion molecule and ErbB2 tyrosine kinase receptor are upregulated in many cancers, including breast cancer, and promote cancer cell proliferation and metastasis. Using human breast cancer cell lines T47D and SUM190-PT, in which both nectin-4 and ErbB2 were upregulated, we showed here that nectin-4 cis-interacted with ErB2 and enhanced its dimerization and activation, followed by the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. The third immunoglobulin-like domain of nectin-4 cis-interacted with domain IV of ErbB2. This region differs from the trastuzumab-interacting region but is included in the trastuzumab-resistant splice variants of ErbB2, p95-ErbB2 and ErbB2ΔEx16. Nectin-4 also cis-interacted with these trastuzumab-resistant splice variants and enhanced the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. In addition, nectin-4 enhanced the activation of the p95-ErbB2-induced JAK-STAT3 signalling pathway, but not the ErbB2- or ErbB2ΔEx16-induced JAK-STAT3 signalling pathway. These results indicate that nectin-4 cis-interacts with ErbB2 and its trastuzumab-resistant splice variants and enhances the activation of these receptors and downstream signalling pathways in a novel mechanism.

Quantitative Analysis of Interaction Between CADM1 and Its Binding Cell-Surface Proteins Using Surface Plasmon Resonance Imaging

The cell adhesion molecule (CADM) family of the immunoglobulin superfamily (IgSF) comprises four members, CADM1-CADM4, and participates in the formation of epithelial and synaptic adhesion through cell-cell homophilic and heterophilic interactions. To identify the partners that interact with each member of the CADM family proteins, we set up a platform for multiple detection of the extracellular protein-protein interactions using surface plasmon resonance imaging (SPRi) and analyzed the interactions between the CADM family proteins and 10 IgSF of their structurally related cell adhesion molecules. SPRi analysis identified a new interaction between CADM1 and CADM4, where this heterophilic interaction was shown to be involved in morphological spreading of adult T-cell leukemia (ATL) cells expressing CADM1 when incubated on CADM4-coated glass. Moreover, class-I MHC-restricted T-cell-associated molecule (CRTAM) was identified to show the highest affinity to CADM1 among its binding partners by comparing the dissociation constants calculated from the SPR sensorgrams. These results suggest that the SPRi platform would provide a novel screening tool to characterize extracellular protein-protein interactions among cell-surface and secreted proteins, including IgSF molecules.

Clinicopathological significance of Necl-4 expression in pancreatic ductal adenocarcinoma

AIMS

The loss, or decreased expression, of nectin-like molecule 4 (Necl-4; an immunoglobulin-like cell adhesion molecule) is reported to be associated with the development and progression of certain types of cancer. We investigated the clinicopathological significance of Necl-4 expression in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

Immunohistochemical analyses of Necl-4 (n=258) and E-cadherin (n=256) expression were performed using tissue microarray blocks of PDAC samples. Necl-4 expression of 38 pancreatic intraepithelial neoplasia (PanIN) lesions included in tissue microarray cores was also evaluated. Necl-4 and E-cadherin expression was considered positive if >30% of cells were stained, and negative if ≤30% of cells were stained.

RESULTS

Necl-4 expression was positive in 45.7% (n=118) and negative in 54.3% (n=140) of PDAC cases. Necl-4 staining was positive in 96.7% (n=29) and negative in 3.3% (n=1) of low-grade PanIN cases, and positive in 62.5% (n=5) and negative in 37.5% (n=3) of high-grade PanIN cases. The number of cases with positive Necl-4 expression decreased in the order low-grade PanIN>high-grade PanIN>PDAC (p<0.001). Negative Necl-4 expression was significantly associated with a larger tumour size of >30 mm, perineural invasion, lymphatic involvement, lymph node metastasis (pN1), an advanced TNM (tumour, node, metastases) stage (stage IIB-IV), an advanced histological grade (G2/3), and shorter overall survival. E-cadherin staining was positive in 46.1% (n=118) and negative in 53.9% (n=138) of PDAC cases. Necl-4 expression correlated positively with E-cadherin expression (r=0.405, p<0.001).

CONCLUSIONS

The results suggest that Necl-4 is associated with carcinogenesis and aggressiveness of PDAC.

Nectin spot: a novel type of nectin-mediated cell adhesion apparatus

Nectins are Ca(2+)-independent immunoglobulin (Ig) superfamily cell adhesion molecules constituting a family with four members, all of which have three Ig-like loops at their extracellular regions. Nectins play roles in the formation of a variety of cell-cell adhesion apparatuses. There are at least three types of nectin-mediated cell adhesions: afadin- and cadherin-dependent, afadin-dependent and cadherin-independent, and afadin- and cadherin-independent. In addition, nectins trans-interact with nectin-like molecules (Necls) with three Ig-like loops and other Ig-like molecules with one to three Ig-like loops. Furthermore, nectins and Necls cis-interact with membrane receptors and integrins, some of which are associated with the nectin-mediated cell adhesions, and play roles in the regulation of many cellular functions, such as cell polarization, movement, proliferation, differentiation, and survival, co-operatively with these cell surface proteins. The nectin-mediated cell adhesions are implicated in a variety of diseases, including genetic disorders, neural disorders, and cancers. Of the three types of nectin-mediated cell adhesions, the afadin- and cadherin-dependent apparatus has been most extensively investigated, but the examples of the third type of apparatus independent of afadin and cadherin are recently increasing and its morphological and functional properties have been well characterized. We review here recent advances in research on this type of nectin-mediated cell adhesion apparatus, which is named nectin spot.

Nectin-2 (CD112) Is Expressed on Outgrowth Endothelial Cells and Regulates Cell Proliferation and Angiogenic Function

Outgrowth endothelial cells (OECs) are a subpopulation of endothelial progenitor cells (EPCs) that have the capacity for proliferation and the ability to promote angiogenesis. In this study, we identified Nectin-2 as a surface protein of OECs through unbiased quantitative proteomics analysis. Using immunocytochemistry and flow cytometry, we confirmed that Nectin-2 is highly expressed on OECs. Nectin-2 (CD112) expression was limited or lower on mononuclear cells (MNCs) and mature tube-forming endothelial cells (ECs). Blocking Nectin-2 with a neutralizing monoclonal antibody significantly increased the trans-well migration and tube forming capacity of OECs. Similarly, Nectin-2 knockdown resulted in enhanced tube formation, cell migration and proliferation with p-Erk activation. Moreover, Nectin-2 deficiency resulted in compensatory increase of other Nectin family genes including Nectin-3 and Necl-4 which promote VEGFR signaling. These results indicate that Nectin-2 is a surface marker and an important regulator of OECs, with significant implications for the isolation of OECs and blocking Nectin-2 on OECs by an antibody for angiogenic applications.

A Novel Nectin-mediated Cell Adhesion Apparatus That Is Implicated in Prolactin Receptor Signaling for Mammary Gland Development

Mammary gland development is induced by the actions of various hormones to form a structure consisting of collecting ducts and milk-secreting alveoli, which comprise two types of epithelial cells known as luminal and basal cells. These cells adhere to each other by cell adhesion apparatuses whose roles in hormone-dependent mammary gland development remain largely unknown. Here we identified a novel cell adhesion apparatus at the boundary between the luminal and basal cells in addition to desmosomes. This apparatus was formed by the trans-interaction between the cell adhesion molecules nectin-4 and nectin-1, which were expressed in the luminal and basal cells, respectively. Nectin-4 of this apparatus further cis-interacted with the prolactin receptor in the luminal cells to enhance the prolactin-induced prolactin receptor signaling for alveolar development with lactogenic differentiation. Thus, a novel nectin-mediated cell adhesion apparatus regulates the prolactin receptor signaling for mammary gland development.