Claudin-3 Inhibits Lung Squamous Cell Carcinoma Cell Epithelial-mesenchymal Transition and Invasion via Suppression of the Wnt/β-catenin Signaling Pathway

Prinsepia utilis Royle polysaccharides promote skin barrier repair through the Claudin family

BACKGROUND

Plant polysaccharides have various biological activities. However, few studies have been conducted on the skin barrier of Prinsepia utilis Royle polysaccharide extract (PURP).

MATERIALS AND METHODS

The proportions of polysaccharides, monosaccharides and proteins were determined by extracting polysaccharides from fruit meal using water. The healing rate was measured by cell scratch assays. SDS-damaged reconstructed human epidermal models, an acetone-ether-induced mouse model and an IL-4-induced cellular inflammation model were used to detect the effects of polysaccharides on the phenotype, HA, TEWL, and TEER, with further characterizations performed using QRT-PCR, Western blotting, immunofluorescence (IF) assays.

RESULTS

PURP contained 35.73% polysaccharides and 11.1% proteins. PURP promoted cell migration and increased skin thickness in a reconstructed human epidermis model. The TEWL significantly decreased, and the HA content significantly increased. PURP significantly increased the TEER and decreased the permeability of the SDS-damaged reconstructed human epidermis model. Claudin-3, Claudin-4, and Claudin-5 were significantly upregulated. IF and Western blot analysis revealed that the Claudin-4 level significantly increased after treatment with PURP. Claudin-1, Claudin-3, Claudin-4, and Claudin-5 gene expression and IF and immunohistochemical staining were significantly increased in mice treated with acetone-ether. PURP promoted the expression of Claudin-1, Claudin-3, Claudin-4, and Claudin-5 after treatment with 100 ng/mL IL-4. PURP also downregulated the expression of NO, IL6, TNFα and NFκB in Raw 264.7 cells and in a mouse model.

CONCLUSION

We hypothesize that PURP may repair the skin barrier by promoting the expression of the claudin family and can assist in skin therapy.

Claudins in Cancer: A Current and Future Therapeutic Target

Claudins are a family of 27 proteins that have an important role in the formation of tight junctions. They also have an important function in ion exchange, cell mobility, and the epithelial-to-mesenchymal transition, the latter being very important in cancer invasion and metastasis. Therapeutic targeting of claudins has been investigated to improve cancer outcomes. Recent evidence shows improved outcomes when combining monoclonal antibodies against claudin 18.2 with chemotherapy for patients with gastroesophageal junction cancer. Currently, chimeric antigen receptor T-cells targeting claudin 18 are under investigation. In this review, we will discuss the major functions of claudins, their distribution in the normal as well as cancerous tissues, and their effect in cancer metastasis, with a special focus on the therapeutic targeting of claudins to improve cancer outcomes.

Dynamic tuft cell expansion during gastric metaplasia and dysplasia

Tuft cells are chemosensory cells associated with luminal homeostasis, immune response, and tumorigenesis in the gastrointestinal tract. We aimed to elucidate alterations in tuft cell populations during gastric atrophy and tumorigenesis in humans with correlative comparison to relevant mouse models. Tuft cell distribution was determined in human stomachs from organ donors and in gastric pathologies including Ménétrier's disease, Helicobacter pylori gastritis, intestinal metaplasia (IM), and gastric tumors. Tuft cell populations were examined in Lrig1-KrasG12D , Mist1-KrasG12D , and MT-TGFα mice. Tuft cells were evenly distributed throughout the entire normal human stomach, primarily concentrated in the isthmal region in the fundus. Ménétrier's disease stomach showed increased tuft cells. Similarly, Lrig1-Kras mice and mice overexpressing TGFα showed marked foveolar hyperplasia and expanded tuft cell populations. Human stomach with IM or dysplasia also showed increased tuft cell numbers. Similarly, Mist1-Kras mice had increased numbers of tuft cells during metaplasia and dysplasia development. In human gastric cancers, tuft cells were rarely observed, but showed positive associations with well-differentiated lesions. In mouse gastric cancer xenografts, tuft cells were restricted to dysplastic well-differentiated mucinous cysts and were lost in less differentiated cancers. Taken together, tuft cell populations increased in atrophic human gastric pathologies, metaplasia, and dysplasia, but were decreased in gastric cancers. Similar findings were observed in mouse models, suggesting that, while tuft cells are associated with precancerous pathologies, their loss is most associated with the progression to invasive cancer.

Expression patterns of claudins in cancer

Claudins are four-transmembrane proteins, which were found in tight junctions. They maintain cell barriers and regulate cell differentiation and proliferation. They are involved in maintaining cellular polarity and normal functions. Different claudins show different expression patterns. The expression level and localization of claudins are altered in various cancers. They promote or inhibit proliferation, invasion, and migration of cancer cells through multiple signaling pathways. Therefore, claudins may serve as diagnostic markers, novel therapeutic targets, and prognostic risk factors. The important roles of claudins in cancer aroused our great interest. In the present review, we provide a summary of insights into expression patterns of claudins in cancer, which is more comprehensive and provides new ideas for further research.

Claudin-3 facilitates the progression and mediates the tumorigenic effects of TGF-β in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a significantly malignant and lethal brain tumor with an average survival time of less than 12 months. Several researches had shown that Claudin-3 (CLDN3) is overexpressed in various cancers and might be important in their growth and spread. In this study, we used qRT-PCR, western blotting, immunohistochemistry, and immunofluorescence staining assays to investigate the expression levels of various proteins. To explore the proliferation abilities of GBM cells, we conducted the CCK-8 and EdU-DNA formation assays. Wound healing and transwell assays were used to investigate the capacities of invasion and migration of GBM cells. Additionally, we constructed an intracranial xenograft model of GBM to study the in vivo role of CLDN3. Our study devoted to investigate the function of CLDN3 in the pathogenesis and progression of GBM. Our study revealed that CLDN3 was upregulated in GBM and could stimulate tumor cell growth and epithelial-mesenchymal transition (EMT) in both laboratory and animal models. We also discovered that CLDN3 expression could be triggered by transforming growth factor-β (TGF-β) and reduced by specific inhibitors of the TGF-β signaling pathway, such as ITD-1. Further analysis revealed that increased CLDN3 levels enhanced TGF-β-induced growth and EMT in GBM cells, while reducing CLDN3 levels weakened these effects. Our study demonstrated the function of CLDN3 in facilitating GBM growth and metastasis and indicated its involvement in the tumorigenic effects of TGF-β. Developing specific inhibitors of CLDN3 might, therefore, represent a promising new approach for treating this devastating disease.

Tight Junction Protein Signaling and Cancer Biology

Tight junctions (TJs) are intercellular protein complexes that preserve tissue homeostasis and integrity through the control of paracellular permeability and cell polarity. Recent findings have revealed the functional role of TJ proteins outside TJs and beyond their classical cellular functions as selective gatekeepers. This is illustrated by the dysregulation in TJ protein expression levels in response to external and intracellular stimuli, notably during tumorigenesis. A large body of knowledge has uncovered the well-established functional role of TJ proteins in cancer pathogenesis. Mechanistically, TJ proteins act as bidirectional signaling hubs that connect the extracellular compartment to the intracellular compartment. By modulating key signaling pathways, TJ proteins are crucial players in the regulation of cell proliferation, migration, and differentiation, all of which being essential cancer hallmarks crucial for tumor growth and metastasis. TJ proteins also promote the acquisition of stem cell phenotypes in cancer cells. These findings highlight their contribution to carcinogenesis and therapeutic resistance. Moreover, recent preclinical and clinical studies have used TJ proteins as therapeutic targets or prognostic markers. This review summarizes the functional role of TJ proteins in cancer biology and their impact for novel strategies to prevent and treat cancer.

The role and mechanism of claudins in cancer

Claudins are a tetraspan membrane protein multigene family that plays a structural and functional role in constructing tight junctions. Claudins perform crucial roles in maintaining cell polarity in epithelial and endothelial cell sheets and controlling paracellular permeability. In the last two decades, increasing evidence indicates that claudin proteins play a major role in controlling paracellular permeability and signaling inside cells. Several types of claudins are dysregulated in various cancers. Depending on where the tumor originated, claudin overexpression or underexpression has been shown to regulate cell proliferation, cell growth, metabolism, metastasis and cell stemness. Epithelial-to-mesenchymal transition is one of the most important functions of claudin proteins in disease progression. However, the exact molecular mechanisms and signaling pathways that explain why claudin proteins are so important to tumorigenesis and progression have not been determined. In addition, claudins are currently being investigated as possible diagnostic and treatment targets. Here, we discuss how claudin-related signaling pathways affect tumorigenesis, tumor progression, and treatment sensitivity.

Claudin-3 inhibits tumor-induced lymphangiogenesis via regulating the PI3K signaling pathway in lymphatic endothelial cells

Claudin-3 is a tight junction protein that has often been associated with the progression and metastasis of various tumors. Here, the role of claudin-3 in tumor-induced lymphangiogenesis is investigated. We found an increased lymphangiogenesis in the B16F10 tumor in claudin-3 knockout mice, accompanied by augmented melanoma cell metastasis into sentinel lymph nodes. In vitro, the overexpression of claudin-3 on lymphatic endothelial cells inhibited tube formation by suppressing cell migration, resulting in restricted lymphangiogenesis. Further experiments showed that claudin-3 inhibited lymphatic endothelial cell migration by regulating the PI3K signaling pathway. Interestingly, the expression of claudin-3 in lymphatic endothelial cells is down-regulated by vascular endothelial growth factor C that is often present in the tumor microenvironment. This study indicates that claudin-3 plays an important role as a signaling molecule in lymphatic endothelial cell activity associated with tumor lymphangiogenesis, which may further contribute to melanoma metastasis.

Research progress of tight junction protein claudin-3 in hepatobiliary systemic diseases

Claudin-3 is an important member of the claudin family of tight junction proteins and is the most abundant tight junction protein in the hepatobiliary system. It plays an important role in building tight junctions of hepatobiliary cells, and maintaining cellular barrier function and molecular delivery function. Dysregulation of hepatic claudin-3 expression leads to disruption of hepatobiliary system junctions, metabolic function, barrier function, proliferation capacity, and molecular delivery function, and is closely related to the development of various hepatobiliary diseases such as hepatic malignancies, cholesterol stones, and chronic liver diseases. In this paper, we review the progress in the research of claudin-3 in hepatobiliary diseases.

Claudin-18.2 as a therapeutic target in cancers: cumulative findings from basic research and clinical trials

Claudins are major components of tight junctions that maintain cell polarity and intercellular adhesion. The dynamics of claudins in cancer cells have attracted attention as a therapeutic target. During carcinogenesis, claudin expression is generally downregulated; however, overexpression of claudin-18.2 has been observed in several types of cancers. Upregulated and mislocalized claudin-18.2 expression in cancer cells has been suggested as a therapeutic target. Research on claudin-18.2 has revealed its involvement in carcinogenesis. Clinical trials using zolbetuximab, a monoclonal antibody targeting claudin-18.2, for patients with advanced cancer yielded positive results with few high-grade adverse events; thus, it is expected to be a novel and effective therapeutic. Here, we review current insights into the role that claudin-18.2 plays in basic cancer research and clinical applications. A better understanding of these roles will facilitate the development of new treatment strategies for cancer patients with poor prognoses.

CLDN6 Suppresses c-MYC-Mediated Aerobic Glycolysis to Inhibit Proliferation by TAZ in Breast Cancer

Claudin 6 (CLDN6) was found to be a breast cancer suppressor gene, which is lowly expressed in breast cancer and inhibits breast cancer cell proliferation upon overexpression. However, the mechanism by which CLDN6 inhibits breast cancer proliferation is unclear. Here, we investigated this issue and elucidated the molecular mechanisms by which CLDN6 inhibits breast cancer proliferation. First, we verified that CLDN6 was lowly expressed in breast cancer tissues and that patients with lower CLDN6 expression had a worse prognosis. Next, we confirmed that CLDN6 inhibited breast cancer proliferation through in vitro and in vivo experiments. As for the mechanism, we found that CLDN6 inhibited c-MYC-mediated aerobic glycolysis based on a metabolomic analysis of CLDN6 affecting cellular lactate levels. CLDN6 interacted with a transcriptional co-activator with PDZ-binding motif (TAZ) and reduced the level of TAZ, thereby suppressing c-MYC transcription, which led to a reduction in glucose uptake and lactate production. Considered together, our results suggested that CLDN6 suppressed c-MYC-mediated aerobic glycolysis to inhibit the proliferation of breast cancer by TAZ, which indicated that CLDN6 acted as a novel regulator of aerobic glycolysis and provided a theoretical basis for CLDN6 as a biomarker of progression in breast cancer.

Role of tight junction-associated MARVEL protein marvelD3 in migration and epithelial-mesenchymal transition of hepatocellular carcinoma

MarvelD3, a recently identified tight junction membrane protein, could be associated with hepatocellular carcinoma (HCC). We aimed to investigate the role of marvelD3 in Epithelial-Mesenchymal Transition (EMT) and migration of HCC and explore the underlying molecular mechanisms. First, we assessed marvlD3 expression in HCC and normal liver tissues and found loss of marvelD3 expression was significantly correlated with the occurrence and TNM stage of HCC. Second, we detected that marvelD3 was downregulated in HCC cells with transforming growth factor β1 and snail/slug-induced EMT. Finally, we analyzed expression of marvelD3 protein was significantly associated with EMT and the NF-κB signaling pathway. Our study demonstrated that MarvelD3 inhibited EMT and migration of HCC cells along with inhibiting NF-κB signaling pathway.Abbreviations: HCC, Hepatocellular carcinoma; TJ, Tight junction; MARVEL, MAL and related proteins for vesicle trafficking and membrane link; EMT, Epithelial-mesenchymal transition; NF-κB, Nuclear factor kappa B; TAMPs, Tight junction-associated marvel proteins; TGF-β1, Transforming growth factor-β1; MMP9, matrix metallopeptidase 9; RT-PCR, Real-time PCR; IHC, Immunohistochemistry; IF, Immunofluorescence.

GPC3 affects the prognosis of lung adenocarcinoma and lung squamous cell carcinoma

Background

Glypican 3 (GPC3) is a heparin sulphate proteoglycan whose expression is associated with several malignancies. However, its expression in non-small-cell lung carcinoma (NSCLC) is limited and ambiguous. This study aimed to comprehensively evaluate the expression of GPC3 in NSCLC and develop a risk-score model for predicting the prognosis of NSCLC.

Methods

The gene expression profiles of lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) were downloaded from the UCSC Xena database. Using the limma package, the differentially expressed genes (DEGs) between different comparison groups were analysed and the differential expression of GPC3 was calculated. A functional enrichment analysis was conducted for GPC3-associated genes using the DAVID tool. For the GPC3-associated genes shared by the four comparison groups, a protein–protein interaction network was built using the Cytoscape software. After conducting a survival analysis and a Cox regression analysis, the genes found to be significantly correlated with prognosis were selected to construct a risk-score model. Besides, the gene and protein levels of GPC3 were examined by quantitative reverse transcriptase-PCR (qRT-PCR) and immunohistochemistry (IHC) in LUSC tissues and paracancer tissues.

Results

The differential expression of GPC3 was significant (adjusted P < 0.05) in the NSCLC vs. normal, LUAD vs. normal, LUSC versus normal, and LUAD versus. LUSC comparison groups. GPC3 directly interacted with SERPINA1, MFI2, and FOXM1. Moreover, GPC3 expression was significantly correlated with pathologic N, pathologic T, gender, and tumour stage in LUAD samples. Finally, the risk-score model (involving MFI2, FOXM1, and GPC3) for LUAD and that (involving SERPINA1 and FOXM1) for LUSC were established separately. The qRT-PCR result showed that GPC3 expression was much higher in the LUSC tissues than that in the normal group. The IHC results further showed that GPC3 is highly expressed in LUSC tissues, but low in paracancer tissues.

Conclusion

The three-gene risk-score model for LUAD and the two-gene risk-score model for LUSC might be valuable in improving the prognosis of these carcinomas.

Dipeptidyl peptidase like 6 promoter methylation is a potential prognostic biomarker for pancreatic ductal adenocarcinoma

Background: Hypermethylation of gene promoters plays an important role in tumorigenesis. The present study aimed to identify and validate promoter methylation-driven genes (PMDGs) for pancreatic ductal adenocarcinoma (PDAC). Methods: Based on GSE49149 and the PDAC cohort of The Cancer Genome Atlas (TCGA), differential analyses of promoter methylation, correlation analysis, and Cox regression analysis were performed to identify PMDGs. The promoter methylation level was assessed by bisulfite sequencing polymerase chain reaction (BSP) in paired tumor and normal tissues of 72 PDAC patients. Kaplan−Meier survival analyses were performed to evaluate the clinical value of PMDGs. Results: In GSE49149, the β-value of the dipeptidyl peptidase like 6 (DPP6) promoter was significantly higher in tumor compared with normal samples (0.50 vs. 0.24, P<0.001). In the PDAC cohort of TCGA, the methylation level of the DPP6 promoter was negatively correlated with mRNA expression (r = −0.54, P<0.001). In a multivariate Cox regression analysis, hypermethylation of the DPP6 promoter was an independent risk factor for PDAC (hazard ratio (HR) = 543.91, P=0.002). The results of BSP revealed that the number of methylated CG sites in the DPP6 promoter was greater in tumor samples than in normal samples (7.43 vs. 2.78, P<0.001). The methylation level of the DPP6 promoter was moderately effective at distinguishing tumor from normal samples (area under ROC curve (AUC) = 0.74, P<0.001). Hypermethylation of the DPP6 promoter was associated with poor overall (HR = 3.61, P<0.001) and disease-free (HR = 2.01, P=0.016) survivals for PDAC patients. Conclusion: These results indicate that DPP6 promoter methylation is a potential prognostic biomarker for PDAC.

Comprehensive analysis of expression and prognostic value of the claudin family in human breast cancer

Claudins (CLDN) are structural components of tight junctions that function in paracellular transport and maintain the epithelial barrier function. Altered expression and distribution of members of the claudin family have been implicated in several cancers including breast cancer (BC). We performed a comprehensive analysis of the expression and prognostic value of claudins in BC using various online databases. Compared with normal tissues, CLDN3, 4, 6, 7, 9, and 14 were upregulated in BC tissues, whereas CLDN2, 5, 8, 10, 11, 15, 19, and 20 were downregulated. A high expression of CLDN2, 5, 6, 9, 10, 11, and 14–20 was associated with better relapse-free survival (RFS), whereas a high CLDN3 expression correlated with poor RFS. In addition, a high expression of CLDN3, 4, 14, and 20 was associated with poor overall survival (OS), whereas that of CLDN5 and CLDN11 was linked to a better OS. Although METABRIC and TCGA datasets revealed 22% and 27% gene alterations, respectively, in the members of the claudin family, these were not associated with survival. These findings suggest CLDN3, 5, and 11 could be promising therapeutic targets for patients with BC.

Integrative analysis of genomic, epigenomic and transcriptomic data identified molecular subtypes of esophageal carcinoma

Esophageal cancer (EC) involves many genomic, epigenetic and transcriptomic disorders, which play key roles in the heterogeneous progression of cancer. However, the study of EC with multi-omics has not been conducted. This study identified a high consistency between DNA copy number variations and abnormal methylations in EC by analyzing genomics, epigenetics and transcriptomics data and investigating mutual correlations of DNA copy number variation, methylation and gene expressions, and stratified copy number variation genes (CNV-Gs) and methylation genes (MET-Gs). The methylation, CNVs and expression profiles of CNV-Gs and MET-Gs were analyzed by consistent clustering using iCluster integration, here, we determined three subtypes (iC1, iC2, iC3) with different molecular traits, prognostic characteristics and tumor immune microenvironment features. We also identified 4 prognostic genes (CLDN3, FAM221A, GDF15 and YBX2) differentially expressed in the three subtypes, and could therefore be used as representative biomarkers for the three subtypes of EC. In conclusion, by performing comprehensive analysis on genomic, epigenetic and transcriptomic regulations, the current study provided new insights into the multilayer molecular and pathological traits of EC, and contributed to the precision medication for EC patients.

Tumor necrosis factor-α induces claudin-3 upregulation in kidney tubular epithelial cells through NF-κB and CREB1

Claudins are essential for tight junction formation and paracellular transport, and they affect key cellular events including proliferation and migration. The properties of tight junctions are dynamically modulated by a variety of inputs. We previously showed that the inflammatory cytokine tumor necrosis factor-α (TNFα), a major pathogenic factor in kidney disease, alters epithelial permeability by affecting the expression of claudin-1, -2, and -4 in kidney tubular cells. Here, we explored the effect of TNFα on claudin-3 (Cldn-3), a ubiquitous barrier-forming protein. We found that TNFα elevated Cldn-3 protein expression in tubular epithelial cells (LLC-PK1 and IMCD3) as early as 3 h post treatment. Bafilomycin A and bortezomib, inhibitors of lysosomal and proteasomes, respectively, reduced Cldn-3 degradation. However, TNFα caused a strong upregulation of Cldn-3 in the presence of bafilomycin, suggesting an effect independent from lysosomes. Blocking protein synthesis using cycloheximide prevented Cldn-3 upregulation by TNFα, verifying the contribution of de novo Cldn-3 synthesis. Indeed, TNFα elevated Cldn-3 mRNA levels at early time points. Using pharmacological inhibitors and siRNA-mediated silencing, we determined that the effect of TNFα on Cldn-3 was mediated by extracellular signal regulated kinase (ERK)-dependent activation of NF-κB and PKA-induced activation of CREB1. These two pathways were turned on by TNFα in parallel and both were required for the upregulation of Cldn-3. Because Cldn-3 was suggested to modulate cell migration and epithelial-mesenchymal transition (EMT), and TNFα was shown to affect these processes, Cldn-3 upregulation may modulate regeneration of the tubules following injury.

Pre-exposure to hydrogen sulfide modulates the innate inflammatory response to organic dust

Animal production units produce and store many contaminants on-site, including organic dust (OD) and hydrogen sulfide (H₂S). Workers in these settings report various respiratory disease symptoms. Both OD and H₂S have shown to induce lung inflammation. However, impact of co-exposure to both H₂S and OD has not been investigated. Therefore, we tested a hypothesis that pre-exposure to H₂S modulates the innate inflammatory response of the lungs to organic dust. In a mouse model of H₂S and organic dust extract (ODE) exposure, we assessed lung inflammation quantitatively. We exposed human airway epithelial and monocytic cells to medium or H₂S alone or H₂S followed by ODE and measured cell viability, oxidative stress, and other markers of inflammation. Exposure to 10 ppm H₂S followed by ODE increased the lavage fluid leukocytes. However, exposure to 10 ppm H₂S alone resulted in changes in tight junction proteins, an increase in mRNA levels of tlr2 and tlr4 as well as ncf1, ncf4, hif1α, and nrf2. H₂S alone or H₂S and ODE exposure decreased cell viability and increased reactive nitrogen species production. ODE exposure increased the transcripts of tlr2 and tlr4 in both in vitro and in vivo models, whereas increased nfkbp65 transcripts following exposure to ODE and H₂S was seen only in in vitro model. H₂S alone and H₂S followed by ODE exposure increased the levels of IL-1β. We conclude that pre-exposure to H₂S modulates lung innate inflammatory response to ODE.

Clinical Implications of HSC70 Expression in Clear Cell Renal Cell Carcinoma

Purpose: The role of heat shock protein 70 (HSC70) in the progression of clear cell renal cell carcinoma (ccRCC) is unclear. This study explored the effect of the HSC70 on the survival of ccRCC patients. Methods: Immunohistochemical analysis was performed to determine HSC70 expression in samples obtained from 121 ccRCC patients with at least 5 years of follow-up. We also analyzed the association between HSC70 expression and clinicopathological characteristics. Furthermore, the association of overall survival (OS) with HSC70 expression was analyzed using Kaplan-Meier curves. Finally, we used the Oncomine and CCLE databases to determine the effects of HSC70 mRNA expression on ccRCC. Results: HSC70 expression was associated with distant metastasis and death of ccRCC patients. HSC70 was expressed in the nucleus and/or cytoplasm of ccRCC cells. The incidence of distant organ metastasis and death was higher in patients with HSC70 expression than in those without it. Survival analysis revealed that patients with HSC70 expression had significantly shorter OS. Oncomine analyses also showed that the HSC70 mRNA was significantly upregulated in ccRCC tissues. Conclusions: HSC70 expression was related to adverse prognosis, and patients with HSC70 expression had a worse prognosis than those without HSC70 expression. HSC70 may thus serve as a potential therapeutic target for ccRCC.

Role of tight junctions in the epithelial-to-mesenchymal transition of cancer cells

The epithelial-mesenchymal transition (EMT) is an essential step in cancer progression. Epithelial cells possess several types of cell-cell junctions, and tight junctions are known to play important roles in maintaining the epithelial program. EMT is characterized by a loss of epithelial markers, including E-cadherin and tight junction proteins. Somewhat surprisingly, the evidence is accumulating that upregulated expression of tight junction proteins plays an important role in the EMT of cancer cells. Tight junctions have distinct tissue-specific and cancer-specific regulatory mechanisms, enabling them to play different roles in EMT. Tight junctions and related signaling pathways are attractive targets for cancer treatments; signal transduction inhibitors and monoclonal antibodies for tight junction proteins may be used to suppress EMT, invasion, and metastasis. Here we review the role of bicellular and tricellular tight junction proteins during EMT. Further investigation of regulatory mechanisms of tight junctions during EMT in cancer cells will inform the development of biomarkers for predicting prognosis as well as novel therapies.

MicroRNA-200c promotes tumor cell proliferation and migration by directly targeting dachshund family transcription factor 1 by the Wnt/β-catenin signaling pathway in nasopharyngeal carcinoma

The purpose of the present study was to determine the crucial role of microRNAs (miRNAs/miRs) involved in the proliferation and migration of nasopharyngeal carcinoma (NPC) and to investigate their underlying mechanisms. In this study, we focused on the expression and function of miR-200c in NPC. First, we found the expression level of miR-200c in NPC cells and tissues was upregulated, and it was suggested that the high expression of miR-200c accelerated the proliferation and migration of NPC cells in vitro. Notably, a result of the present study was that the cell fate determination factor dachshund family transcription factor 1 (DACH1) was identified as a direct target of miR-200c. Suppression of miR-200c expression in NPC cells increased endogenous DACH1 mRNA and protein levels, which was negatively correlated with miR-200c. Meanwhile, DACH1 was shown to regulate the Wnt/β-catenin signaling pathway. Accordingly, it was concluded that miR-200c exerted a tumor-promoting role in NPC development by targeting DACH1, which may contribute to the increase in the rates of NPC proliferation and migration. miR-200c may be a potential diagnostic and prognostic biomarker for NPC.

Identification and validation of core genes for serous ovarian adenocarcinoma via bioinformatics analysis

Ovarian cancer is a fatal gynaecological malignancy in women worldwide, and serous ovarian cancer (SOC) is considered the most common histological subtype of this malignancy. Thus, the present study aimed to identify the core genes for SOC via bioinformatics analysis. The GSE18520 and GSE14407 datasets were downloaded from the Gene Expression Omnibus (GEO) database to screen for differentially expressed genes (DEGs) and perform gene set enrichment analysis (GSEA). A protein-protein interaction (PPI) network was constructed to identify the core genes, while The Cancer Genome Atlas (TCGA) database was used to screen for prognosis-associated DEGs. Furthermore, clinical samples were collected for further validation of kinesin family member 11 (KIF11) gene. In the GEO analysis, a total of 198 DEGs were identified, including 81 upregulated and 117 downregulated genes compared SOC to normal tissue. GSEA across the two datasets demonstrated that 16 gene sets, including those involved in the cell cycle and DNA replication, were notably associated with SOC. A PPI network of the DEGs was constructed with 130 nodes and 387 edges. Subsequently, 20 core genes involved in the same top-ranked module were filtered out by submodule analysis. Survival analysis identified three predictive genes for SOC prognosis, including KIF11, CLDN3 and FGF13. KIF11 was identified as a core and predictive gene and thus was further validated using clinical samples. The results demonstrated that KIF11 was upregulated in tumour tissues compared with adjacent normal tissues and was associated with aggressive factors, including tumour grade, TNM stage and lymph node invasion. In conclusions, the present study identified the core genes and gene sets for SOC, thus extending the understanding of SOC occurrence and progression. Furthermore, KIF11 was identified as a promising tumour-promoting gene and a potential target for the diagnosis and treatment of SOC.

CLDN3 expression and function in pregnancy-induced hypertension

This aim of the present study was to investigate the expression and function of claudin 3 (CLDN3) in pregnancy-induced hypertension. The mRNA expression levels of CLDN3 in the placental tissue and peripheral blood of patients with pregnancy-induced hypertension were measured using reverse transcription-quantitative PCR. Human trophoblast HTR8/SVneo cells overexpressing CLDN3 were generated using a lentiviral vector. Cell Counting kit-8 (CCK-8) assay, flow cytometry, Transwell chamber assays, confocal laser scanning microscopy and western blot analysis were performed to detect cell proliferation, invasion, migration and apoptosis, in addition to matrix metalloproteinase (MMP) expression and ERK1/2 phosphorylation. The mRNA expression levels of CLDN3 were significantly reduced in the placental tissues and peripheral blood samples of patients with pregnancy-induced hypertension compared with healthy pregnant controls. CLDN3 overexpression significantly increased HTR8/SVneo cell proliferation, invasion and migration whilst reducing apoptosis. HTR8/SVneo cells overexpressing CLDN3 also exhibited increased myofiber levels, increased MMP-2 and MMP-9 expression and increased ERK1/2 signaling activity. CLDN3 downregulation may be associated with the pathogenesis of pregnancy-induced hypertension. In conclusion, CLDN3 promotes the proliferative and invasive capabilities of human trophoblast cells, with the underlying mechanisms possibly involving upregulation of MMP expression via the ERK1/2 signaling pathway.

Puerarin Enhances the Anti-Tumor Effect of Cisplatin on Drug-Resistant A549 Cancer in vivo and in vitro Through Activation of the Wnt Signaling Pathway

Objective

The effect of PUE on enhancing the anti-cancerous efficacy of DDP on drug-resistant A549/DDP cancer and the underlying mechanisms were thoroughly investigated.

Materials and Methods

The cytotoxicity of PUE, DDP, and PUE + DDP to A549 cells and A549/DDP cells, respectively, is determined by cell apoptosis experiments. Anti-proliferation effect of PUE, DDP, and PUE + DDP on A549 cells and A549/DDP cells is evaluated by the cell cloning assay. Qualitative and quantitative analysis of the levels of PUE, DDP, and PUE + DDP of cell proliferation-related genes and proteins expressions in A549/DDP cells are determined by Western blot assay. The levels of VEGF in A549/DDP cells after different treatment strategies are determined by ELISA assay. Qualitative and quantitative determination of VEGF expression in tumor tissues are done by immunohistochemical staining.

Results

In vitro cellular experiments revealed that co-incubation of A549/DDP cells with PUE and DDP led to a dramatically decreased cell viability and cell survival rate compared with the cells only treated by DDP. Such a stimulating effect of PUE on DDP was further confirmed in vivo with results shown that the A549/DDP cancer-bearing mice treaded by combination therapy achieved the lowest tumor growth rate and longest survival time.

Conclusion

Taking these results together, we can draw the conclusion that the PUE enhances the anti-tumor effect of DDP on the drug-resistant A549 cancer in vivo and in vitro through activation of the Wnt signaling pathway.

Localization of claudin-2 and claudin-3 in eutopic and ectopic endometrium is highly similar

PURPOSE

Claudins as the major components of tight junctions are important in maintaining cell-cell integrity and thus function as a barrier. Dysregulation of the claudins is often associated with loss of the epithelial phenotype, a process called epithelial-mesenchymal transition (EMT), which most often results in gain of migrative and invasive properties. However, the role of claudins in the endometrium or endometriosis has only rarely been examined.

METHODS

In this study, we investigated localization of claudin-2 and claudin-3 in the eutopic and ectopic endometrium with immunohistochemistry. A detailed quantification with HSCORE was performed for claudin-2 and claudin-3 in endometrium without endometriosis and in cases with endometriosis compared to the three endometriotic entities: peritoneal, ovarian, and deep-infiltrating endometriosis.

RESULTS

We found a preferential localization of both claudins in the glandular and the luminal epithelial cells in the endometrium with and without endometriosis. Quantification of localization of both claudins showed no differences in eutopic endometrium of control cases compared to cases with endometriosis. Furthermore, both claudins are localized highly similar in the ectopic compared to the eutopic endometrium, which is in clear contrast to previously published data for claudin-3.

CONCLUSION

From our results, we conclude that localization of claudin-2 and claudin-3 is highly stable in eutopic and ectopic endometrium without any loss of the epithelial phenotype and thus do not contribute to the pathogenesis of endometriosis.

Role of Claudin Proteins in Regulating Cancer Stem Cells and Chemoresistance-Potential Implication in Disease Prognosis and Therapy

Claudins are cell–cell adhesion proteins, which are expressed in tight junctions (TJs), the most common apical cell-cell adhesion. Claudin proteins help to regulate defense and barrier functions, as well as differentiation and polarity in epithelial and endothelial cells. A series of studies have now reported dysregulation of claudin proteins in cancers. However, the precise mechanisms are still not well understood. Nonetheless, studies have clearly demonstrated a causal role of multiple claudins in the regulation of epithelial to mesenchymal transition (EMT), a key feature in the acquisition of a cancer stem cell phenotype in cancer cells. In addition, claudin proteins are known to modulate therapy resistance in cancer cells, a feature associated with cancer stem cells. In this review, we have focused primarily on highlighting the causal link between claudins, cancer stem cells, and therapy resistance. We have also contemplated the significance of claudins as novel targets in improving the efficacy of cancer therapy. Overall, this review provides a much-needed understanding of the emerging role of claudin proteins in cancer malignancy and therapeutic management.

Claudin-2: Roles beyond Permeability Functions

Claudin-2 is expressed in the tight junctions of leaky epithelia, where it forms cation-selective and water permeable paracellular channels. Its abundance is under fine control by a complex signaling network that affects both its synthesis and turnover in response to various environmental inputs. Claudin-2 expression is dysregulated in many pathologies including cancer, inflammation, and fibrosis. Claudin-2 has a key role in energy-efficient ion and water transport in the proximal tubules of the kidneys and in the gut. Importantly, strong evidence now also supports a role for this protein as a modulator of vital cellular events relevant to diseases. Signaling pathways that are overactivated in diseases can alter claudin-2 expression, and a good correlation exists between disease stage and claudin-2 abundance. Further, loss- and gain-of-function studies showed that primary changes in claudin-2 expression impact vital cellular processes such as proliferation, migration, and cell fate determination. These effects appear to be mediated by alterations in key signaling pathways. The specific mechanisms linking claudin-2 to these changes remain poorly understood, but adapters binding to the intracellular portion of claudin-2 may play a key role. Thus, dysregulation of claudin-2 may contribute to the generation, maintenance, and/or progression of diseases through both permeability-dependent and -independent mechanisms. The aim of this review is to provide an overview of the properties, regulation, and functions of claudin-2, with a special emphasis on its signal-modulating effects and possible role in diseases.

The Cytoplasmic Expression Of CLDN12 Predicts An Unfavorable Prognosis And Promotes Proliferation And Migration Of Osteosarcoma

Background

To date, the impact and potential molecular mechanisms of CLDN12 and its association with malignancy in osteosarcoma have not been determined.

Materials and methods

In the present study, the expression profiles of CLDN12 in osteosarcoma cell lines and tissues were explored by immunohistochemistry. A fetal osteoblast cell line was transfected with a eukaryotic expression plasmid, and endogenous CLDN12 in osteosarcoma cells were silenced through an RNA interference (RNAi) method. These transfections were verified, and the activation state of Thr308 site in protein kinase B (Akt) was explored by Western blotting. Moreover, the malignant phenotype of osteosarcoma cells was evaluated by cell counting kit-8 (CCK-8), colony formation, Transwell, and wound-healing assays. Furthermore, osteoblast cells were treated with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 to determine the impact of the PI3K/Akt signaling pathway on cell migration ability.

Results

The results revealed that CLDN12 was overexpressed and localized in the cytoplasm of osteosarcoma cells, and its overexpression was associated with an unfavorable prognosis, irrespective of tumor node metastasis stage. In addition, the knockdown of CLDN12 in cultured osteosarcoma cells markedly attenuated cell proliferation and migration, as indicated by the Cell Counting Kit-8 assay, colony formation assay, scratch wound healing assay and Transwell migration assay. The results also demonstrated that the overexpression of CLDN12 increased the activation of Thr308 site in Akt in fetal osteoblast cells, and the PI3K inhibitor LY294002 partially decreased CLDN12-promoted proliferation and metastasis.

Conclusion

In conclusion, the results of the present study indicated that CLDN12 promoted cell proliferation and migration through the PI3K/Akt signaling pathway in osteosarcoma cells, suggesting that CLDN12 may be a potential agent in the treatment of patients with osteosarcoma.

Claudin-2 suppresses GEF-H1, RHOA, and MRTF, thereby impacting proliferation and profibrotic phenotype of tubular cells

The tight junctional pore-forming protein claudin-2 (CLDN-2) mediates paracellular Na⁺ and water transport in leaky epithelia and alters cancer cell proliferation. Previously, we reported that tumor necrosis factor-α time-dependently alters CLDN-2 expression in tubular epithelial cells. Here, we found a similar expression pattern in a mouse kidney injury model (unilateral ureteral obstruction), consisting of an initial increase followed by a drop in CLDN-2 protein expression. CLDN-2 silencing in LLC-PK¹ tubular cells induced activation and phosphorylation of guanine nucleotide exchange factor H1 (GEF-H1), leading to Ras homolog family member A (RHOA) activation. Silencing of other claudins had no such effects, and re-expression of an siRNA-resistant CLDN-2 prevented RHOA activation, indicating specific effects of CLDN-2 on RHOA. Moreover, kidneys from CLDN-2 knockout mice had elevated levels of active RHOA. Of note, CLDN-2 silencing reduced LLC-PK1 cell proliferation and elevated expression of cyclin-dependent kinase inhibitor P27 (P27KIP1) in a GEF-H1/RHOA-dependent manner. P27KIP1 silencing abrogated the effects of CLDN-2 depletion on proliferation. CLDN-2 loss also activated myocardin-related transcription factor (MRTF), a fibrogenic RHOA effector, and elevated expression of connective tissue growth factor and smooth muscle actin. Finally, CLDN-2 down-regulation contributed to RHOA activation and smooth muscle actin expression induced by prolonged tumor necrosis factor-α treatment, because they were mitigated by re-expression of CLDN-2. Our results indicate that CLDN-2 suppresses GEF-H1/RHOA. CLDN-2 down-regulation, for example, by inflammation, can reduce proliferation and promote MRTF activation through RHOA. These findings suggest that the initial CLDN-2 elevation might aid epithelial regeneration, and CLDN-2 loss could contribute to fibrotic reprogramming.

Increased expression of claudin-12 promotes the metastatic phenotype of human bronchial epithelial cells and is associated with poor prognosis in lung squamous cell carcinoma

A prior study by our group using cDNA array analysis identified the tight junction component claudin-12 (CLDN12) to be an upregulated gene in lung squamous cell carcinoma (SqCC) cells compared with normal human bronchial epithelial cells. The present study aimed to explore the effect and underlying molecular mechanism of CLDN12 with regard to the malignant phenotype of SqCC. Firstly, the expression patterns of CLDN12 in SqCC tissues, lung adenocarcinoma tissues and histologically non-neoplastic lung epithelial tissues were investigated by immunohistochemistry and western blotting. Additionally, associations between CLDN12 expression and clinicopathological indicators were examined in patients with SqCC. Furthermore, the impact of CLDN12 on the malignant phenotype of the human bronchial epithelial cell line BEAS-2B in vitro was assessed using the Cell Counting kit-8 assay, Transwell assay and a wound-healing experiment. Western blotting and immunofluorescence were also used to detect the impact of CLDN12 on the epithelial-mesenchymal transition (EMT) of BEAS-2B cells. Tyrosine kinase 2 (Tyk2) RNA interference was further utilized to determine the impact of the Tyk2/signal transducer and activator of transcription 1 (Stat1) signaling pathway on the EMT of BEAS-2B cells. To conclude, it was indicated that the expression of CLDN12 was upregulated in SqCC tissues and was associated with the extent of lymphatic metastasis in patients with SqCC. Furthermore, CLDN12 promoted the EMT of human bronchial epithelial cells in vitro. The findings indicated that the induction of Tyk2/Stat1 signaling appears to be an important mechanism by which CLDN12 promotes the EMT of SqCC cells.

Specific knockdown of HOXB7 inhibits cutaneous squamous cell carcinoma cell migration and invasion while inducing apoptosis via the Wnt/β-catenin signaling pathway

Metastatic cutaneous squamous cell carcinoma (CSCC) is a major cause of death associated with nonmelanoma skin cancer. The involvement of homeobox B7 ( HOXB7) in cancers has been reported. Thus, the current study intends to explore the effect of HOXB7 on CSCC and its relationship with the Wnt/β-catenin signaling pathway. Initially, microarray-based gene expression profiling of CSCC was performed, and HOXB7 was identified as an upregulated gene based on the microarray data of GSE66359 . Following this, the experimental results indicated that HOXB7 and β-catenin formed a composite, demonstrating that endogenous HOXB7 binds to β-catenin. Subsequently, CSCC cells were treated with siRNA against HOXB7 or an inhibitor of the Wnt/β-catenin signaling pathway to analyze any underlying regulatory mechanism of HOXB7 on the CSCC cells. Tumor growth involving xenografts in nude mice was also observed so as to explore whether or not HOXB7 could regulate subcutaneous tumor growth through in vivo culturing. To investigate the potential effects of HOXB7 on the Wnt/β-catenin signaling pathway, we determined the expression of HOXB7 and downstream genes of the Wnt/β-catenin signaling pathway. Notably, siRNA-mediated knockdown of HOXB7 inhibited the activation of the Wnt/β-catenin signaling pathway, thereby impeding the progression of cell viability, migration, and invasion as well as of the tumor growth, although contrarily facilitating cell apoptosis. Taken together, silencing of the HOXB7 has the mechanism of inactivating the Wnt/β-catenin signaling pathway, thereby accelerating cell apoptosis and suppressing cell migration and invasion in CSCC, which could provide a candidate target for the CSCC treatment.