The distinct expression patterns of claudin-10, -14, -17 and E-cadherin between adjacent non-neoplastic tissues and gastric cancer tissues

Role of tight junction proteins in shaping the immune milieu of malignancies

INTRODUCTION

Tight junctions (TJs) and their constituent proteins play pivotal roles in cellular physiology and anatomy by establishing functional boundaries within and between neighboring cells. While the involvement of TJ proteins, such as claudins, in cancer is extensively studied, studies highlighting their interaction with immune system are still meager. Studies indicate that alterations in cytokines and immune cell populations can affect TJ proteins, compromising TJ barrier function and exacerbating pro-inflammatory conditions, potentially leading to epithelial cell malignancy. Disrupted TJs in established tumors may foster a pro-tumor immune microenvironment, facilitating tumor progression, invasion, epithelial-to-mesenchymal transition and metastasis. Although previous literature contains many studies describing the involvement of TJs in pathogenesis of malignancies their role in modulating the immune microenvironment of tumors is just beginning to be unleashed.

AREAS COVERED

This article for the first time attempts to discern the importance of interaction between TJs and immune microenvironment in malignancies. To achieve the above aim a thorough search of databases like PubMed and Google Scholar was conducted to identify the recent and relevant articles on the topic.

EXPERT OPINION

Breaking the vicious cycle of dysbiosis/infections/chemical/carcinogen-induced inflammation-TJ remodeling-malignancy-TJ dysregulation-more inflammation can be used as a strategy to complement the effect of immunotherapies in various malignancies.

Downregulation of chemoresistance by claudin-14 silencing in human colorectal cancer cells

An exceptional expression of claudins (CLDNs), tight junction (TJ) proteins, is observed in various solid cancer tissues. However, the pathophysiological roles of CLDNs have not been clarified in detail. CLDN14 is highly expressed in human colorectal cancer (CRC) tissues and cultured cancer epithelial cells. We found CLDN14 silencing decreased cell viability without affecting spheroid size in the three-dimensional (3D) spheroid model of DLD-1 cells derived from human CRC. Mitochondria activity and oxidative stress level were reduced by CLDN14 silencing. Furthermore, CLDN14 silencing decreased the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and its target antioxidative genes. CLDN14 was colocalized with ZO-1, a scaffolding protein in the TJ. CLDN14 silencing induced the disruption of TJ barrier such as the reduction of transepithelial electrical resistance and elevation of fluxes of small molecules including glucose in two-dimensional (2D) cultured model,. The depletion of glucose induced the elevation of ROS generation, mitochondria activity, and Nrf2 expression. These results suggest that CLDN14 increases Nrf2 expression in spheroids mediated via the formation of paracellular barrier to glucose. The cytotoxicities of doxorubicin, an anthracycline anticancer drug, and oxaliplatin, a platinum-based agent, were augmented by an Nrf2 activator in 2D cultured cells. The anticancer drug-induced toxicity was enhanced by CLDN14 silencing in 3D spheroids. We suggest that CLDN14 may potentiate chemoresistance mediated by the suppression of paracellular glucose permeability and activation of the Nrf2 signaling pathway in CRC cells.

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.

Claudins-Promising Biomarkers for Selected Gastrointestinal (GI) Malignancies?

Despite recent() improvements in diagnostic ability() and treatment() strategies for patients() with neoplastic disease(), gastrointestinal (GI) cancers(), such() as colorectal, gastric, pancreatic, and oesophageal cancers(), are still common() malignancies and the leading() cause() of cancer() deaths worldwide(), with a high frequency of recurrence and metastasis as well as poor patient() prognosis. There is a link() between the secretion of proteolytic enzymes that degrade the extracellular matrix and the pathogenesis of GI tumours. Recent() findings have focused() on the potential() significance() of selected claudins (CLDNs) in the pathogenesis and prognosis of GI cancers(). Tight junctions (TJs) have been proven to play an important role() in maintaining cell() polarity and permeability. A number of authors have recently() revealed that TJ proteins, particularly() selected CLDNs, are related() to inflammation and the development() of various tumours, including GI malignancies. This review() presents general() characteristics and the involvement() of selected CLDNs in the progression() of GI malignancies, with a focus() on the potential() application() of these proteins in the diagnosis() and prognosis of colorectal cancer() (CRC), gastric cancer() (GC), pancreatic cancer() (PC), and oesophageal cancer() (EC). Our review() indicates that selected CLDNs, particularly() CLDN1, 2, 4, 7, and 18, play a significant() role() in the development() of GI tumours and in patient() prognosis. Furthermore, selected CLDNs may be of value() in the design() of therapeutic() strategies for the treatment() of recurrent tumours.

CircKIF4A promotes non-small cell lung cancer proliferation and metastasis through MiR-1238/CLDN14 axis

As the leading cause of cancer-related death worldwide, non-small-cell lung cancer (NSCLC) is still in need of improved therapeutic strategies. CircKIF4A has been found to be involved in the progression of multiple cancers while its role in NSCLC remains unclear. To investigate the functions of circKIF4A, we assessed the expression of circKIF4A in NSCLC cells and tissues and performed experiments to determine the detailed functions of circKIF4A in NSCLC, including migration and proliferation. We found CircKIF4A expressed more heavily in the cells and tissues of NSCLC patients, and functional studies showed that inhibition of circKIF4A reduced NSCLC cells metastasis and proliferation. Furthermore, we seek to identify the underlying regulatory effect of circKIF4A in NSCLC. Studies revealed that circKIF4A sponged miR-1238 to promote NSCLC progression by up-regulating claudin14 (CLDN14) expression. In conclusion, circKIF4A is a potential diagnostic and therapeutic target in the circKIF4A/miR-1238/CLDN14 axis that plays an important role in NSCLC progression.

Claudin-17 Deficiency in Mice Results in Kidney Injury Due to Electrolyte Imbalance and Oxidative Stress

The multi-gene claudin (CLDN) family of tight junction proteins have isoform-specific roles in blood–tissue barrier regulation. CLDN17, a putative anion pore-forming CLDN based on its structural characterization, is assumed to regulate anion balance across the blood-tissue barriers. However, our knowledge about CLDN17 in physiology and pathology is limited. The current study investigated how Cldn17 deficiency in mice affects blood electrolytes and kidney structure. Cldn17^−/− mice revealed no breeding abnormalities, but the newborn pups exhibited delayed growth. Adult Cldn17^−/− mice displayed electrolyte imbalance, oxidative stress, and injury to the kidneys. Ingenuity pathway analysis followed by RNA-sequencing revealed hyperactivation of signaling pathways and downregulation of SOD1 expression in kidneys associated with inflammation and reactive oxygen species generation, demonstrating the importance of Cldn17 in the maintenance of electrolytes and reactive oxygen species across the blood-tissue barrier.

Long non-coding RNA TTTY15 silencing inhibits gastric cancer progression by sponging microRNA-98-5p to down-regulate cyclin D2 expression

Gastric cancer is the most common malignant tumor in the digestive system. However, the detection rate of early gastric cancer is low, resulting in delayed prognosis and poor outcomes. The identification of effective therapeutic targets for gastric cancer is, therefore, of profound significance. Recently, various lncRNAs have been shown to be biomarkers for different cancers. This study investigated the role of long non-coding RNA (lncRNA) TTTY15 in gastric cancer. The expression level of TTTY15, miR-98-5p, and cyclin D2 (CCND2) were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot assay using tumor and non-tumor tissues collected from 30 patients with gastric cancer, gastric cancer cell lines (AGS, SNU-5, and NCI-N87), and the normal gastric epithelial cell line GES-1. The interaction between TTTY15 and miR-98-5p and between miR-98-5p and CCND2 were predicted by bioinformatics and then further verified by dual-luciferase and RNA pull-down analyses. Cell proliferation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide (MTT) assay, and apoptosis was measured using flow cytometry and caspase-3 assay. The results indicate that TTTY15 and CCND2 expression increased and miR-98-5p expression decreased in gastric cancer tumor tissues and cell lines. TTTY15 knockdown inhibited gastric cancer cell proliferation but promoted apoptosis by sponging miR-98-5p, which acted as a tumor suppressor gene by reducing the expression of its target gene CCND2 in gastric cancer. In conclusion, lncRNA TTTY15 is a potential oncogene involved in gastric cancer and may be a novel therapeutic target for gastric cancer treatment.

Claudins and Gastric Cancer: An Overview

Simple Summary

Gastric cancer (GC) is one of the most common cancers and the third leading cause of cancer deaths worldwide, with a high frequency of recurrence and metastasis, and a poor prognosis. This review presents novel biological and clinical significance of claudin (CLDN) expression in GC, especially CLDN18, and clinical trials centered around CLDN18.2. It also presents new findings for other CLDNs.

Abstract

Despite recent improvements in diagnostic ability and treatment strategies, advanced gastric cancer (GC) has a high frequency of recurrence and metastasis, with poor prognosis. To improve the treatment results of GC, the search for new treatment targets from proteins related to epithelial–mesenchymal transition (EMT) and cell–cell adhesion is currently being conducted. EMT plays an important role in cancer metastasis and is initiated by the loss of cell–cell adhesion, such as tight junctions (TJs), adherens junctions, desmosomes, and gap junctions. Among these, claudins (CLDNs) are highly expressed in some cancers, including GC. Abnormal expression of CLDN1, CLDN2, CLDN3, CLDN4, CLDN6, CLDN7, CLDN10, CLDN11, CLDN14, CLDN17, CLDN18, and CLDN23 have been reported. Among these, CLDN18 is of particular interest. In The Cancer Genome Atlas, GC was classified into four new molecular subtypes, and CLDN18–ARHGAP fusion was observed in the genomically stable type. An anti-CLDN18.2 antibody drug was recently developed as a therapeutic drug for GC, and the results of clinical trials are highly predictable. Thus, CLDNs are highly expressed in GC as TJs and are expected targets for new antibody drugs. Herein, we review the literature on CLDNs, focusing on CLDN18 in GC.

Transcriptional and Epigenetic Bioinformatic Analysis of Claudin-9 Regulation in Gastric Cancer

Gastric cancer is a heterogeneous disease that represents 5% to 10% of all new cancer cases worldwide. Advances in histological diagnosis and the discovery of new genes have admitted new genomic classifications. Nevertheless, the bioinformatic analysis of gastric cancer databases has favored the detection of specific differentially expressed genes with biological significance. Claudins, a family of proteins involved in tight junction physiology, have emerged as the key regulators of cellular processes, such as growth, proliferation, and migration, associated with cancer progression. The expression of Claudin-9 in the gastric cancer tissue has been linked to poor prognosis, however, its transcriptional and epigenetic regulations demand a more comprehensive analysis. Using the neural network promoter prediction, TransFact, Uniprot-KB, Expasy-SOPMA, protein data bank, proteomics DB, Interpro, BioGRID, String, and the FASTA protein sequence databases and software, we found the following: (1) the promoter sequence has an unconventional structure, including different transcriptional regulation elements distributed throughout it, (2) GATA 4, GATA 6, and KLF5 are the key regulators of Claudin-9 expression, (3) Oct1, NF-κB, AP-1, c-Ets-1, and HNF-3β have the higher binding affinity to the CLDN9 promoter, (4) Claudin-9 interacts with cell differentiation and development proteins, (5) CLDN9 is highly methylated, and (6) Claudin-9 expression is associated with poor survival. In conclusion, Claudin-9 is a protein that should be considered a diagnostic marker as its gene promoter region binds to the transcription factors associated with the deregulation of cell control, enhanced cell proliferation, and metastasis.

Tight junction protein CLDN17 serves as a tumor suppressor to reduce the invasion and migration of oral cancer cells by inhibiting epithelial-mesenchymal transition

OBJECTIVE

To investigate claudin-17 (CLDN17) expression in oral cancer and its effect on epithelial-mesenchymal transition (EMT), invasion and migration in oral cancer cells.

METHODS

The GEO2R tool was used to analyze gene expression in two microarray datasets (GSE74530 and GSE146483) derived from the Gene Expression Omnibus (GEO) database. Gene Expression Profiling Interactive Analysis (GEPIA) verified CLDN17 expression in head and neck squamous cell carcinoma (HNSC) patients. Moreover, oral cancer cells were transfected with CLDN17 overexpression plasmid or CLDN17 shRNA to evaluate cell invasion and migration. Gene and protein expression was detected by qRT-PCR, immunohistochemistry and western blotting.

RESULTS

CLDN17 was one of the top 200 differentially expressed genes in the GSE74530 and GSE146483 datasets and was downregulated in oral cancer. CLDN17 expression was higher in HNSC tissues, and it was related to TNM staging. In HNSC tumors, CLDN17 expression was positively correlated with CDH1 but negatively related to VIM, SNAIL1, SNAIL2, and TWIST1. Meanwhile, we found that CLDN17 expression was lower in oral cancer tissues; it declined with higher T status, N status, M status and staging, lower differentiation grade, and a worse prognosis. Upregulation of CLDN17 inhibited the invasion and migration of oral cancer cells, with elevated CDH1 and reduced VIM, SNAIL1, SNAIL2, and TWIST1, while CLDN17 downregulation had the opposite effects.

CONCLUSION

CLDN17 may serve as a tumor suppressor in oral cancer since it could reduce the invasion and migration of cells by inhibiting the EMT process, thus becoming a potential therapeutic target in oral cancer.

Intestinal Barrier, Claudins and Mycotoxins

The intestinal barrier is the main barrier against all of the substances that enter the body. Proper functioning of this barrier guarantees maintained balance in the organism. Mycotoxins are toxic, secondary fungi metabolites, that have a negative impact both on human and animal health. It was postulated that various mycotoxins may affect homeostasis by disturbing the intestinal barrier. Claudins are proteins that are involved in creating tight junctions between epithelial cells. A growing body of evidence underlines their role in molecular response to mycotoxin-induced cytotoxicity. This review summarizes the information connected with claudins, their association with an intestinal barrier, physiological conditions in general, and with gastrointestinal cancers. Moreover, this review also includes information about the changes in claudin expression upon exposition to various mycotoxins.

Role of Barrier Integrity and Dysfunctions in Maintaining the Healthy Gut and Their Health Outcomes

Mucosal surface layers are the critical borders throughout epithelial membranes. These epithelial cells segregate luminal material from external environments. However, mucosal linings are also accountable for absorbing nutrients and requiring specific barrier permeability. These functional acts positioned the mucosal epithelium at the epicenter of communications concerning the mucosal immune coordination and foreign materials, such as dietary antigens and microbial metabolites. Current innovations have revealed that external stimuli can trigger several mechanisms regulated by intestinal mucosal barrier system. Crucial constituents of this epithelial boundary are physical intercellular structures known as tight junctions (TJs). TJs are composed of different types transmembrane proteins linked with cytoplasmic adaptors which helps in attachment to the adjacent cells. Disruption of this barrier has direct influence on healthy or diseased condition, as barrier dysfunctions have been interrelated with the initiation of inflammation, and pathogenic effects following metabolic complications. In this review we focus and overview the TJs structure, function and the diseases which are able to influence TJs during onset of disease. We also highlighted and discuss the role of phytochemicals evidenced to enhance the membrane permeability and integrity through restoring TJs levels.

Claudin 10 acts as a novel biomarker for the prognosis of patients with ovarian cancer

Ovarian cancer (OC) is one of the most fatal gynecological malignancies in the world and confers a poor 5-year survival rate. The present study was designed to discover novel prognostic markers for patients with OC in order to estimate disease metastasis or recurrence. Based on the large cohorts of transcriptome data from multicenter sources, a comprehensive analysis was performed to explore potential prognostic markers. A total of 269 differentially expressed genes were identified, of which 32 were upregulated and 237 downregulated in OC tissues compared with the corresponding expression in normal tissues. Kaplan-Meier analysis, log-rank test and nomogram analysis were employed to demonstrate that low expression levels of claudin 10 (CLDN10) were associated with a less favorable disease prognosis. The most promising prognostic marker for OC was subsequently selected. Additionally, the prognostic nomogram was constructed in order to assess the 5-year survival rate using CLDN10 expression as a prognostic marker for OC. Furthermore, gene set enrichment analysis and analysis of the tumor-associated competing endogenous RNA network were performed to elucidate the potential biological processes associated with CLDN10 expression. The current results indicated that CLDN10 may influence OC progression via transforming growth factor-β (TGF-β)- or WNT/β-catenin-induced epithelial-to-mesenchymal transition (EMT). The associations among CLDN10, microRNA-486-5p, TGF-β, WNT/β-catenin and EMT should be further investigated in future studies.

Relationship between apical junction proteins, gene expression and cancer

The apical junctional complex (AJC) is a cell-cell adhesion system present at the upper portion of the lateral membrane of epithelial cells integrated by the tight junction (TJ) and the adherens junction (AJ). This complex is crucial to initiate and stabilize cell-cell adhesion, to regulate the paracellular transit of ions and molecules and to maintain cell polarity. Moreover, we now consider the AJC as a hub of signal transduction that regulates cell-cell adhesion, gene transcription and cell proliferation and differentiation. The molecular components of the AJC are multiple and diverse and depending on the cellular context some of the proteins in this complex act as tumor suppressors or as promoters of cell transformation, migration and metastasis outgrowth. Here, we describe these new roles played by TJ and AJ proteins and their potential use in cancer diagnostics and as targets for therapeutic intervention.

Claudin-9 enhances the metastatic potential of hepatocytes via Tyk2/Stat3 signaling

BACKGROUND/AIMS

We have previously identified a tight junction protein claudin-9 (CLDN9) as an upregulated gene in hepatocellular carcinoma (HCC) through an immunohistochemistry analysis. Here, we explore its function and clinical relevance in human HCC.

MATERIALS AND METHODS

Stable transfection of the hepatocyte line HL7702 with CLDN9 was confirmed by the real-time polymerase chain reaction (PCR), western blotting, and immunofluorescence. The impact of CLDN9 on the cell invasion and migration was assessed in vitro by a transwell assay and wound-healing experiment. Western blotting was used to determine the activation state of the Tyk2 (tyrosine kinase 2)/Stat3 (signal transducer and activator of transcription 3) pathway. Moreover, we used a Tyk2-RNAi assay to silence the expression of Tyk2 in CLDN9 expressing hepatocytes; subsequently, the impact of the Tyk2/Stat3 signaling pathway on the cell invasion and migration in vitro was assessed by a transwell assay and a wound-healing experiment. Furthermore, an immunohistochemistry method was utilized to explore the expression levels of CLDN9 and p-Stat3 in the HCC tissues and histologically non-neoplastic hepatic tissues.

RESULTS

We confirmed that the expression of CLDN9 significantly enhanced the metastatic ability of hepatocytes in vitro, and the activation of the Stat3 pathway by Tyk2 was an important mechanism by which CLDN9 promoted hepatocyte aggressiveness in HCC.

CONCLUSION

As an HCC proto-oncogene, CLDN9 affected the Stat3 signaling pathway via Tyk2 and ultimately enhanced the metastatic ability of hepatocytes.

Mouse Models of Human Claudin-Associated Disorders: Benefits and Limitations

In higher organisms, epithelia separate compartments in order to guarantee their proper function. Such structures are able to seal but also to allow substances to pass. Within the paracellular pathway, a supramolecular structure, the tight junction transport is largely controlled by the temporospatial regulation of its major protein family called claudins. Besides the fact that the expression of claudins has been identified in different forms of human diseases like cancer, clearly defined mutations in the corresponding claudin genes have been shown to cause distinct human disorders. Such disorders comprise the skin and its adjacent structures, liver, kidney, the inner ear, and the eye. From the phenotype analysis, it has also become clear that different claudins can cause a complex phenotype when expressed in different organs. To gain deeper insights into the physiology and pathophysiology of claudin-associated disorders, several mouse models have been generated. In order to model human disorders in detail, they have been designed either as full knockouts, knock-downs or knock-ins by a variety of techniques. Here, we review human disorders caused by CLDN mutations and their corresponding mouse models that have been generated thus far and assess their usefulness as a model for the corresponding human disorder.

Identification of claudin-2, -6, -11 and -14 as prognostic markers in human breast carcinoma

The development of cancer occurs with various genomic and epigenetic modifications that act as indicators for early diagnosis and treatment. Recent data have shown that the abnormal expression of the claudin (CLDN) tight junction (TJ) proteins is involved in the tumorigenesis of numerous human cancers. Real-time quantitative PCR and western blotting were used to explore the differences in the expression of the CLDN TJ proteins in breast carcinoma tissues and non-neoplastic tissues. The results showed that CLDN5, CLDN9, CLDN12 and CLDN13 were not expressed in breast carcinoma tissues or non-neoplastic tissues. CLDN1, CLDN3, CLDN8 and CLDN10 were expressed in breast carcinoma and non-neoplastic tissues, but there was no significant difference between the expression of these CLDN proteins among them. The expression of CLDN2, -6, -11 and -14 varied between the breast carcinoma and non-neoplastic tissues. Moreover, 86 samples of breast carcinoma and non-neoplastic tissues were examined for the expression of CLDN2, -6, -11 and -14 by streptavidin-peroxidase immunohistochemical staining. The data revealed that the CLDN2, CLDN6, and CLDN14 were expressed in the cell membrane and the expression levels of these proteins were downregulated in breast carcinoma. The CLDN11 was expressed in cell cytoplasm and the expression level of CLDN11 was upregulated compared with those in non-neoplastic tissues. Consistent with these findings, the expression of CLDN2, CLDN6 and CLDN14 were downregulated, while the expression of CLDN11 was upregulated in breast carcinoma compared with those in non-neoplastic tissues. Furthermore, the associations between these CLDNs and clinicopathologic indicators were analyzed, and these CLDN expressions were revealed to be associated with distant metastasis and to predict a poor prognosis. In conclusion, our data showed that the expression levels of CLDN2, -6, -11 and -14 differed between breast carcinoma tissues and histologically non-neoplastic tissues, and the expression levels of these CLDNs may be useful as molecular markers for the diagnosis of breast carcinoma as well as for the determination of metastasis and prognosis.

Identification of claudin‑1, ‑3, ‑7 and ‑8 as prognostic markers in human laryngeal carcinoma

Various genomic and epigenetic modifications that occur during the development of cancer act as potential biomarkers for early diagnosis and treatment. Previous studies have demonstrated abnormal expression of the claudin (CLDN) tight junction (TJ) proteins in numerous types of human cancer. Reverse transcription-quantitative polymerase chain reaction and western blotting were employed to investigate variations in the expression of the CLDN TJ proteins in laryngeal non-neoplastic tissues and laryngeal squamous carcinoma tissues. It was revealed that CLDN2, CLDN4, CLDN5, CLDN6, CLDN9, CLDN11 and CLDN12 were undetectable in laryngeal squamous carcinoma tissues and laryngeal non-neoplastic tissues. Additionally, CLDN10 was expressed in laryngeal squamous carcinoma tissues and laryngeal non-neoplastic tissues; however, no significant difference was reported. Conversely, the expression levels of CLDN1 and CLDN7 mRNA and protein were downregulated in laryngeal squamous carcinoma tissues compared with in adjacent non-neoplastic tissues, whereas those of CLDN3 and CLDN8 were upregulated. A total of 80 samples of laryngeal squamous carcinoma and non-neoplastic tissues were analyzed for the expression of CLDN1, −3, −7 and −8 via streptavidin-peroxidase immunohistochemical staining. It was revealed that the expression levels of CLDN1 and CLDN7 were downregulated in laryngeal squamous carcinoma tissues compared with in non-neoplastic mucosal tissues, whereas those of CLDN3 and CLDN8 were upregulated. Furthermore, the associations between CLDN expression and the clinicopathological factors of patients were analyzed. The expression levels of CLDN3 and CLDN7 were reported to be associated with distant metastasis and serve as potential predictors of poor prognosis. In conclusion, the findings of the present study demonstrated that the expression levels of CLDN1, −3, −7 and −8 varied between laryngeal squamous carcinoma tissues and non-neoplastic tissues. The expression levels of these CLDNs may be useful molecular markers for the diagnosis of laryngeal carcinoma, and determining the metastasis and prognosis of this disease.

Tight Junction Proteins and Signaling Pathways in Cancer and Inflammation: A Functional Crosstalk

The ability of epithelial cells to organize through cell–cell adhesion into a functioning epithelium serves the purpose of a tight epithelial protective barrier. Contacts between adjacent cells are made up of tight junctions (TJ), adherens junctions (AJ), and desmosomes with unique cellular functions and a complex molecular composition. These proteins mediate firm mechanical stability, serves as a gatekeeper for the paracellular pathway, and helps in preserving tissue homeostasis. TJ proteins are involved in maintaining cell polarity, in establishing organ-specific apical domains and also in recruiting signaling proteins involved in the regulation of various important cellular functions including proliferation, differentiation, and migration. As a vital component of the epithelial barrier, TJs are under a constant threat from proinflammatory mediators, pathogenic viruses and bacteria, aiding inflammation and the development of disease. Inflammatory bowel disease (IBD) patients reveal loss of TJ barrier function, increased levels of proinflammatory cytokines, and immune dysregulation; yet, the relationship between these events is partly understood. Although TJ barrier defects are inadequate to cause experimental IBD, mucosal immune activation is changed in response to augmented epithelial permeability. Thus, the current studies suggest that altered barrier function may predispose or increase disease progression and therapies targeted to specifically restore the barrier function may provide a substitute or supplement to immunologic-based therapies. This review provides a brief introduction about the TJs, AJs, structure and function of TJ proteins. The link between TJ proteins and key signaling pathways in cell proliferation, transformation, and metastasis is discussed thoroughly. We also discuss the compromised intestinal TJ integrity under inflammatory conditions, and the signaling mechanisms involved that bridge inflammation and cancer.

[Expression and significance of tight junction proteins in the kidney in a mouse model of renal ischemia-reperfusion injury]

OBJECTIVE

To study the expression and significance of tight junction proteins (claudin-2, claudin-10, and claudin-17) in a mouse model of renal ischemia-reperfusion injury.

METHODS

A total of 152 male C57BL/6 mice were randomly assigned to control group (n=8), sham-operation group (n=72), and model group (n=72). The renal pedicles at both sides were clamped for 30 minutes to establish a mouse model of renal ischemia-reperfusion injury. According to the time points of reperfusion (0, 3, 6, 12, 24, 48, and 72 hours and 5 and 7 days), the sham-operation group and the model group were further divided into 9 subgroups, with 8 mice in each subgroup. RT-PCR and immunohistochemistry were used to measure the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue.

RESULTS

The control and sham-operation groups had no significant changes in the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue over the time of reperfusion (P>0.05). Compared with the control and sham-operation groups, the model group had decreased mRNA and protein expression of claudin-2 and claudin-10 after reperfusion, and the expression decreased gradually over the time of reperfusion, with the lowest levels at 24 hours of reperfusion (P<0.05). Compared with the control and sham-operation groups, the model group had increased mRNA and protein expression of claudin-17 after reperfusion, and the expression increased gradually over the time of reperfusion, with the highest mRNA level at 12 hours and the highest protein level at 24 hours of reperfusion (P<0.05).

CONCLUSIONS

Renal ischemia-reperfusion injury is closely associated with abnormal expression of tight junction proteins claudin-2, claudin-10, and claudin-17.

[Expression and significance of tight junction proteins in the kidney in a mouse model of renal ischemia-reperfusion injury]

OBJECTIVE

To study the expression and significance of tight junction proteins (claudin-2, claudin-10, and claudin-17) in a mouse model of renal ischemia-reperfusion injury.

METHODS

A total of 152 male C57BL/6 mice were randomly assigned to control group (n=8), sham-operation group (n=72), and model group (n=72). The renal pedicles at both sides were clamped for 30 minutes to establish a mouse model of renal ischemia-reperfusion injury. According to the time points of reperfusion (0, 3, 6, 12, 24, 48, and 72 hours and 5 and 7 days), the sham-operation group and the model group were further divided into 9 subgroups, with 8 mice in each subgroup. RT-PCR and immunohistochemistry were used to measure the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue.

RESULTS

The control and sham-operation groups had no significant changes in the mRNA and protein expression of claudin-2, claudin-10, and claudin-17 in renal tissue over the time of reperfusion (P>0.05). Compared with the control and sham-operation groups, the model group had decreased mRNA and protein expression of claudin-2 and claudin-10 after reperfusion, and the expression decreased gradually over the time of reperfusion, with the lowest levels at 24 hours of reperfusion (P<0.05). Compared with the control and sham-operation groups, the model group had increased mRNA and protein expression of claudin-17 after reperfusion, and the expression increased gradually over the time of reperfusion, with the highest mRNA level at 12 hours and the highest protein level at 24 hours of reperfusion (P<0.05).

CONCLUSIONS

Renal ischemia-reperfusion injury is closely associated with abnormal expression of tight junction proteins claudin-2, claudin-10, and claudin-17.

CLDN10 is Associated with Papillary Thyroid Cancer Progression

The incidence of thyroid cancer is staying at a high level. Claudin family is a skelemin contacting with the intercellular junction and can keep a dynamic balance between cells. Recently, many types of research indicated that the expression level of claudins is closely related to various cancer types and they can be novel diagnostic markers. For instance, Claudin-10(CLDN10) is the high expression in primary hepatocellular carcinoma, papillary thyroid cancer (PTC) and so on. But the biological role and function of CLDN10 in PTC are unclear. In our study, we measured the expression of CLDN10 in human normal tissues and matched PTC tissues by quantitative real-time polymerase chain reaction (qRT-PCR) and this observation was consistent with that in the TCGA cohort. We discovered that high expression of CLDN10 was correlated with lymph node metastasis, age and Histological type in TCGA cohorts. Kaplan-Meier analysis showed that patients with higher CLDN10 expression had a worse overall survival. In vitro, CLDN10 could promote cellular proliferation, migration, and invasion in PTC cell lines. In a word, CLDN10 is a functionally gene facilitating tumorgenesis in PTC and acts as an oncogene in PTC.

Increased expression of claudin-17 promotes a malignant phenotype in hepatocyte via Tyk2/Stat3 signaling and is associated with poor prognosis in patients with hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the second leading cause of cancer death in Asia; however, the molecular mechanism in its tumorigenesis remains unclear. Abnormal expression of claudins (CLDNs), a family of tight junction (TJ) proteins, plays an important role in the metastatic phenotype of epithelial-derived tumors by affecting tight junction structure, function and related cellular signaling pathways. In a previous study, we used a tissue chip assay to identify CLDN17 as an upregulated gene in HCC. Here we aimed to use molecular biology technology to explore the effect of CLDN17 on the malignant phenotype of HCC and the underlying molecular mechanism, with the objective of identifying a new target for HCC treatment and the control of HCC metastasis.

Method

The expression levels of CLDN17 in HCC tissues and histologically non-neoplastic hepatic tissues were explored by immunohistochemistry. Stable transfection of the hepatocyte line HL7702 with CLDN17 was detected by real-time polymerase chain reaction (PCR), western blotting and immunofluorescence. The impact of CLDN17 on the malignant phenotype of HL7702 cells in vitro was assessed by a Cell Counting Kit-8 (CCK8) assay, a Transwell assay and a wound-healing experiment. Western blotting was utilized to detect the activation state of Tyrosine kinase 2 (Tyk2) / signal transducer and activator of transcription3 (Stat3) pathway. A Tyk2 RNA interference (RNAi) was utilized to determine the impact of the Tyk2/Stat3 signaling pathway on the malignant phenotype of hepatocytes.

Results

In this work, our research group first found that CLDN17 was highly expressed in HCC tissues and was associated with poor prognosis. In addition, we demonstrated that CLDN17 affected the Stat3 signaling pathway via Tyk2 and ultimately enhanced the migration ability of hepatocytes.

Conclusion

In conclusion, we confirmed that the upregulated expression of CLDN17 significantly enhances the migration ability of hepatocytes in vitro and we found that the activation of the Stat3 pathway by Tyk2 may an important mechanism by which CLDN17 promotes aggressiveness in hepatocytes.

Differences in the expression profiles of claudin proteins in human gastric carcinoma compared with non‑neoplastic mucosa

Numerous genetic alterations associated with cancer progression have the potential to serve as biomarkers for the early diagnosis of cancer. Numerous studies have suggested that claudin proteins, which are the primary components of tight junction structures, are associated with the regulation of cell polarity and cell differentiation. To investigate the expression profiles of the tight junction proteins claudin-2, −5, −7 and −8 in gastric carcinoma, immunohistochemical analysis, western blotting and reverse transcription-quantitative polymerase chain reaction analysis was used to detect the expression profiles of these claudin proteins in gastric carcinoma tissues and in homologous non-neoplastic mucosal tissues. According to the present study, the expression levels of claudin-7 and claudin-8 were downregulated, while the expression of claudin-5 was upregulated in gastric carcinoma tissues compared with in non-neoplastic mucosal tissues. Additionally, no notable difference was observed between claudin-2 expression in gastric carcinoma tissues and non-neoplastic mucosae. Correlations between claudin-7 and −8 expression and lymphatic metastasis in gastric carcinoma tissues were additionally reported. In summary, the present study revealed the distinct expression profiles of claudin-5, −7 and −8 in non-neoplastic mucosal tissues and gastric carcinoma tissues. Furthermore, the expression of these claudin proteins was highly associated with metastatic progression and prognosis in patients with gastric carcinoma, and had predictive value for the metastasis and survival of patients with gastric carcinoma.

12-Lipoxygenase promotes invasion and metastasis of human gastric cancer cells via epithelial-mesenchymal transition

The role of 12-lipoxygenase (12-LOX) in tumorigenesis has been well established in several types of human cancer, including gastric cancer. It was reported that epithelial-mesenchymal transition (EMT) contributes to tumor invasion and metastasis. However, whether 12-LOX promotes the invasion and metastasis of human gastric cancer cells via EMT remains to be elucidated. In the present study, the expression of 12-LOX and EMT markers, N-cadherin and E-cadherin, was evaluated in gastric cancer and adjacent normal mucosa samples by immunohistochemical analysis. 12-LOX-overexpressing gastric cancer cells were established via lentiviral transfection of SCG-7901 cells. Wound-healing and Transwell assays were performed to examine the regulation of cell metastasis and invasion by 12-LOX. Furthermore, the regulation of N-cadherin expression by 12-LOX was evaluated using reverse transcription-quantitative polymerase chain reaction and western blotting. The results revealed that the expression of 12-LOX and N-cadherin was significantly higher in gastric cancer compared with that in adjacent normal mucosa tissues (P<0.05). By contrast, the expression of E-cadherin was significantly decreased in gastric cancer compared with that in adjacent normal mucosa tissues (P<0.05). Furthermore, the expression of 12-LOX was positively associated with N-cadherin expression in gastric cancer tissues. 12-LOX-overexpressing gastric cancer cells exhibited significantly increased invasion and migration abilities compared with the empty vector and control groups. The expression of N-cadherin in 12-LOX-overexpressing gastric cancer cells was increased compared with that in the empty vector and control groups. The present study suggests that EMT may be involved in the promotion of the invasion and metastasis of human gastric cancer cells by 12-LOX.

Differences in the expression profiles of claudin proteins in human nasopharyngeal carcinoma compared with non-neoplastic mucosa

Background

Several studies have suggested that claudin proteins, which are the main components of tight junction structures, are related to the regulation of cell polarity and cell differentiation.

Method

To explore the expression profiles of the tight junction proteins claudin-2, − 5, − 8 and − 9 in nasopharyngeal carcinoma, IHC (immunohistochemical analysis), Western blot and real-time PCR were used to detect the expression profiles of these claudin proteins in nasopharyngeal carcinoma tissues and in non-neoplastic mucosal tissues.

Results

According to our study, the expression levels of claudin-2 and claudin-5 were reduced, while the expression of claudin-8 was increased in nasopharyngeal carcinoma tissues in comparison with non-neoplastic mucosal tissues. Correlations between claudin-2 and -5 expression and metastatic progression in nasopharyngeal carcinoma patients were also found.

Conclusion

In summary, our research reveals distinct expression profiles of claudin-2, − 5 and − 8 in non-neoplastic mucosal tissues and nasopharyngeal carcinoma tissues. In addition, the expression of these claudin proteins was highly correlated with metastatic progression and prognosis in patients with nasopharyngeal carcinoma and had predictive value for the metastasis and survival of nasopharyngeal carcinoma patients.

EXPRESSION OF E-CADHERIN AND WNT PATHWAY PROTEINS BETACATENIN, APC, TCF-4 AND SURVIVIN IN GASTRIC ADENOCARCINOMA: CLINICAL AND PATHOLOGICAL IMPLICATION

Background

Gastric cancer is the fifth most frequent cancer and the third most common cause of cancer-related deaths worldwide.It has been reported that Wnt/ betacatenin pathway is activated in 30-50% of these tumors. However,the deregulation of this pathway has not been fully elucidated.

Aim

To determine the expression of E-cadherin, betacatenin, APC, TCF-4 and survivin proteins in gastric adenocarcinoma tissues and correlate with clinical and pathological parameters.

Method

Seventy-one patients with gastric adenocarcinoma undergoing gastrectomy were enrolled. The expression of E-cadherin, betacatenin, APC, TCF-4 and survivin proteins was detected by immunohistochemistryand related to the clinical and pathological parameters.

Results

The expression rates of E-cadherin in the membrane was 3%; betacatenin in the cytoplasm and nucleus were 23,4% and 3,1% respectively; APC in the cytoplasm was 94,6%; TCF-4 in the nucleus was 19,4%; and survivin in the nucleus 93,9%. The expression rate of E-cadherin was correlated with older patients (p=0,007), while betacatenin with tumors <5 cm (p=0,041) and APC with proximal tumors (p=0,047). Moreover, the expression of TCF-4 was significantly higher in the diffuse type (p=0,017) and T4 tumors (p=0,002).

Conclusion

The Wnt/betacatenin is not involved in gastric carcinogenesis. However, the high frequency of survivin allows to suggest that other signaling pathways must be involved in the transformation of gastric tissue.

Genome-wide transcriptome analysis in the ovaries of two goats identifies differentially expressed genes related to fecundity

The goats are widely kept as livestock throughout the world. Two excellent domestic breeds in China, the Laiwu Black and Jining Grey goats, have different fecundities and prolificacies. Although the goat genome sequences have been resolved recently, little is known about the gene regulations at the transcriptional level in goat. To understand the molecular and genetic mechanisms related to the fecundities and prolificacies, we performed genome-wide sequencing of the mRNAs from two breeds of goat using the next-generation RNA-Seq technology and used functional annotation to identify pathways of interest. Digital gene expression analysis showed 338 genes were up-regulated in the Jining Grey goats and 404 were up-regulated in the Laiwu Black goats. Quantitative real-time PCR verified the reliability of the RNA-Seq data. This study suggests that multiple genes responsible for various biological functions and signaling pathways are differentially expressed in the two different goat breeds, and these genes might be involved in the regulation of goat fecundity and prolificacy. Taken together, our study provides insight into the transcriptional regulation in the ovaries of 2 species of goats that might serve as a key resource for understanding goat fecundity, prolificacy and genetic diversity between species.

Tight junction disruption: Helicobacter pylori and dysregulation of the gastric mucosal barrier

Long-term chronic infection with Helicobacter pylori (H. pylori) is a risk factor for gastric cancer development. In the multi-step process that leads to gastric cancer, tight junction dysfunction is thought to occur and serve as a risk factor by permitting the permeation of luminal contents across an otherwise tight mucosa. Mechanisms that regulate tight junction function and structure in the normal stomach, or dysfunction in the infected stomach, however, are largely unknown. Although conventional tight junction components are expressed in gastric epithelial cells, claudins regulate paracellular permeability and are likely the target of inflammation or H. pylori itself. There are 27 different claudin molecules, each with unique properties that render the mucosa an intact barrier that is permselective in a way that is consistent with cell physiology. Understanding the architecture of tight junctions in the normal stomach and then changes that occur during infection is important but challenging, because most of the reports that catalog claudin expression in gastric cancer pathogenesis are contradictory. Furthermore, the role of H. pylori virulence factors, such as cytotoxin-associated gene A and vacoulating cytotoxin, in regulating tight junction dysfunction during infection is inconsistent in different gastric cell lines and in vivo, likely because non-gastric epithelial cell cultures were initially used to unravel the details of their effects on the stomach. Hampering further study, as well, is the relative lack of cultured cell models that have tight junction claudins that are consistent with native tissues. This summary will review the current state of knowledge about gastric tight junctions, normally and in H. pylori infection, and make predictions about the consequences of claudin reorganization during H. pylori infection.

Expression and significance of annexin A2 in patients with gastric adenocarcinoma and the association with E-cadherin

Annexin A2 is a calcium-dependent phospholipid-binding protein, involved in invasion, angiogenesis and migration in cancer cells. The aims of the present study were to evaluate the expression levels of annexin A2 and E-cadherin in gastric adenocarcinoma (GAC), and to investigate the association between the expression of annexin A2 and that of E-cadherin and Ki67, in addition to various clinicopathological factors. This study included 126 patients that were histopathologically diagnosed with GAC. Tissue samples were acquired by surgical resection, and annexin A2 mRNA expression levels were determined using reverse transcription-quantitative polymerase chain reaction. Annexin A2, E-cadherin and Ki67 protein expression levels were detected using western blot analysis and/or immunohistochemical staining. The expression of annexin A2 mRNA and protein was significantly upregulated in the GAC tissues. Annexin A2 expression was detected in 52/126 cases (41.3%) of gastric cancer (GC), and correlations were identified between annexin A2 expression and Tumor, Node, Metastasis (TNM) stage (P=0.002), lymph node metastasis (P=0.016) and distal metastasis (P=0.005). The positive expression rates of E-cadherin and Ki67 in the tumor tissue of patients with GAC were 27.8% (35/126) and 56.2% (71/126), respectively. A negative correlation was observed between the expression of annexin A2 and E-cadherin (P<0.001). No significant association was detected between the expression levels of annexin A2 and Ki67 (P=0.801). In conclusion, upregulated annexin A2 expression was associated with lymph node metastasis, distal metastasis, advanced TNM stage and E-cadherin expression in patients with GAC. The association between the expression of annexin A2 and that of E-cadherin may indicate an underlying mechanism by which annexin A2 contributes to the metastasis in GC, and thus annexin A2 may represent a potential target for the treatment of GAC.

High expression of DEK predicts poor prognosis of gastric adenocarcinoma

BACKGROUND

DEK, as an oncoprotein, plays an important role in cancer development and progression. This study aimed to investigate the clinicopathological significance of DEK overexpression in patients with gastric cancer.

MATERIALS AND METHODS

The expression of DEK protein was evaluated by immunohistochemical (IHC) staining of 172 gastric cancer samples with complete clinicopathological features, and the correlation between DEK expression and clinicopathological features was examined. Survival rates were also calculated using the Kaplan-Meier method in gastric cancer patients with complete survival data.

RESULTS

DEK protein showed a strictly nuclear staining pattern in gastric cancers with IHC and immunofluorescence. The strongly positive rate of DEK protein was 60.5% (104/172) in gastric cancers, which was significantly higher than that in either gastric dysplasia (19.4%, 7/36) or adjacent normal mucosa (0%, 0/27). DEK expression in gastric cancer correlated to tumor size, differentiation, clinical stage, disease-free survival, and overall survival rates. Further analysis showed that patients with early-stage gastric cancer and high DEK expression had shorter disease-free survival and overall survival duration than those with low DEK expression.

CONCLUSION

High level of DEK protein expression predicts the poor prognosis of patients with gastric cancer. DEK expression might be potentially used as an independent effective biomarker for prognostic evaluation of gastric cancers.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5050145571193097.

Activation of P21-activated protein kinase 2 is an independent prognostic predictor for patients with gastric cancer

Objective

p21-activated kinase (PAK) 2, as a member of the PAK family kinases, is involved in a number of hallmark processes including cell proliferation, survival, mitosis, apoptosis, motility and angiogenesis. However, the clinical significance of the activation of PAK2 in human gastric cancer has not been fully elucidated. The aim of this study was to investigate whether PAK2 expression and its phosphorylation status are correlated with tumor progression and prognosis in gastric cancer.

Methods

Expression patterns and subcellular localizations of PAK2 and Ser20-phosphorylated PAK2 (pSer20PAK2) in 82 gastric cancer patients were detected by immunohistochemistry.

Results

Both PAK2 and pSer20PAK2 immunostainings were localized in the cytoplasm of tumor cells of gastric cancer tissues. Compared with the normal gastric mucosa, the expression levels of PAK2 and pSer20PAK2 proteins were both significantly increased (both P < 0.001). Additionally, the patients displaying the over-expression of PAK2 and pSer20PAK2 proteins were dramatically associated with unfavorable clinicopathologic variables including higher tumor depth (P = 0.022 and 0.036, respectively), greater extent of lymph node metastasis ((P = 0.022 and 0.036, respectively), positive distant metastasis (P = 0.025 and 0.038, respectively) and advanced tumor stage (P = 0.018 and 0.031, respectively). Moreover, the patients overexpressing PAK2 and pSer20PAK2 proteins have poor overall survival rates relative to those without overexpression of these proteins. Furthermore, cox multi-factor analysis showed that PAK2 (p = 0.012) and pSer20PAK2 (p = 0.010) were independent prognosis factors for human gastric cancer.

Conclusion

Our data suggest for the first time that PAK2 activation may be associated with advanced tumor progression and poor prognosis of gastric cancer.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1236344107120406.