Role of tight junctions in cell proliferation and cancer

Comparative analysis of the growth differences between hybrid Ningdu Yellow chickens and their parentals

Although the local high quality chicken breed in China has excellent flavor, its growth rate is inferior to that of foreign breeds. To improve the growth rate of local chicken breeds, it is crucial to study the mechanism of chicken muscle development. Herein, Ningdu Yellow chicken was used as the research object, and a new hybrid breed (W) was obtained by crossing the G, H and D lines, which combined the excellent physiological characteristics of its parents. Combined analysis of Ningdu Yellow chickens and their parents was carried out. Chickens from 105-day-old lines (W, G, H) were selected, and breast meat and serum were extracted for transcriptome sequencing and metabolome determination to study their growth differences. The live weight, carcass weight, half-eviscerated weight, eviscerated weight, and breast muscle weight of W were significantly higher than those of G and H. Differential expression analysis identified 1700 differentially expressed genes (DEG), and gene ontology and kyoto encyclopedia of genes and genomes (KEGG) analyses identified 33 and 1 pathways related to growth and development and steroid biosynthesis, respectively. Next, pairwise analysis identified 57 KEGG pathways, among which the MAPK signaling, steroid hormone biosynthesis, tight junction, and PPAR signaling pathways were involved in growth and development. Cluster analysis found that genes highly expressed in the W group were associated with regulation of the actin cytoskeleton, riboflavin metabolism, steroid biosynthesis, and glycerophospholipid metabolism. The top 2 clusters obtained by protein-protein interaction analysis were important for the growth and development of chickens. Finally, the metabolomic analysis found key differentially accumulated metabolites (DAM) that might be account for the growth differences. Further integrated analysis identified key DEGs and DAMs that might be responsible for the observed growth differences. This study identified genes governing growth traits in Ningdu Yellow chickens, laying a theoretical foundation for the development of chicken breeding, the utilization of hybrid supporting lines, and promotion of the Chinese chicken industry.

JAM3 promotes cervical cancer metastasis by activating the HIF-1α/VEGFA pathway

Cervical cancer is the fourth most common cancer and the leading cause of mortality among women worldwide. Tumor metastasis is an important cause of poor prognosis. Determining the exact mechanisms of metastasis and potential targeted therapies is urgently needed. Junctional adhesion molecule 3 (JAM3) is an important member of the TJ tight junction (TJ) family, and its biological function in cervical cancer needs to be further clarified. We found that JAM3 was highly expressed in cervical cancer patients with lymph node metastasis and that high expression of JAM3 promoted cervical cancer cell metastasis both in vitro and in vivo. In addition, overexpression of JAM3 induces epithelial-mesenchymal transition (EMT). Moreover, silencing JAM3 suppressed cervical cancer cell migration and invasion in vitro. Finally, JAM3 overexpression activated the HIF-1α/VEGFA pathway. In conclusion, our results suggested that JAM3 promotes cervical cancer cell migration and invasion by activating the HIF-1α/VEGFA pathway. JAM3 may be a promising biomarker and effective therapeutic target for cervical cancer.

Modulation of hepatic cellular tight junctions via coculture with cholangiocytes enables non-destructive bile recovery

Estimation of the biliary clearance of drugs and their metabolites in humans is crucial for characterizing hepatobiliary disposition and potential drug-drug interactions. Sandwich-cultured hepatocytes, while useful for in vitro bile analysis, require cell destruction for bile recovery, limiting long-term or repeated dose drug effect evaluations. To overcome this limitation, we investigated the feasibility of coculturing a human hepatic carcinoma cell line (HepG2-NIAS cells) and a human cholangiocarcinoma cell line (TFK-1 cells) using the collagen vitrigel membrane in a variety of coculture configurations. The coculture configuration with physiological bile flow increased the permeability of fluorescein-labeled bile acids (CLF) across the HepG2-NIAS cell layer by approximately 1.2-fold compared to the HepG2-NIAS monoculture. This enhancement was caused by paracellular leakage due to the loosened tight junctions of HepG2-NIAS, confirmed by the use of an inhibitor for bile acid transporters, the increase of permeability of dextran, and the decrease of the transepithelial electrical resistance (TEER) value. Based on the results of loosening hepatic tight junctions via coculture with TFK-1 in the CLF permeability assay, we next attempted to collect the CLF accumulated in the bile canaliculi of HepG2-NIAS. The recovery of the CLF accumulated in the bile canaliculi was increased 1.4 times without disrupting hepatic tight junctions by the coculture of HepG2-NIAS cells and TFK-1 cells compared to the monoculture of HepG2-NIAS cells. This non-destructive bile recovery has the potential as a tool for estimating the biliary metabolite and provides valuable insights to improve in vitro bile analysis.

Functional Analysis of Membrane-Associated Scaffolding Tight Junction (TJ) Proteins in Tumorigenic Characteristics of B16-F10 Mouse Melanoma Cells

Tight junction (TJ) proteins (Tjps), Tjp1 and Tjp2, are tight junction-associated scaffold proteins that bind to the transmembrane proteins of tight junctions and the underlying cytoskeleton. In this study, we first analyzed the tumorigenic characteristics of B16-F10 melanoma cells, including cell proliferation, migration, invasion, metastatic potential, and the expression patterns of related proteins, after the CRISPR-Cas9-mediated knockout (KO) of Tjp genes. The proliferation of Tjp1 and Tjp2 KO cells significantly increased in vitro. Other tumorigenic characteristics, including migration and invasion, were significantly enhanced in Tjp1 and Tjp2 KO cells. Zonula occludens (ZO)-associated protein Claudin-1 (CLDN-1), which is a major component of tight junctions and functions in controlling cell-to-cell adhesion, was decreased in Tjp KO cells. Additionally, Tjp KO significantly stimulated tumor growth and metastasis in an in vivo mouse model. We performed a transcriptome analysis using next-generation sequencing (NGS) to elucidate the key genes involved in the mechanisms of action of Tjp1 and Tjp2. Among the various genes affected by Tjp KO-, cell cycle-, cell migration-, angiogenesis-, and cell-cell adhesion-related genes were significantly altered. In particular, we found that the Ninjurin-1 (Ninj1) and Catenin alpha-1 (Ctnna1) genes, which are known to play fundamental roles in Tjps, were significantly downregulated in Tjp KO cells. In summary, tumorigenic characteristics, including cell proliferation, migration, invasion, tumor growth, and metastatic potential, were significantly increased in Tjp1 and Tjp2 KO cells, and the knockout of Tjp genes significantly affected the expression of related proteins.

Extrahepatic manifestations of progressive familial intrahepatic cholestasis syndromes: Presentation of a case series and literature review

BACKGROUND AND AIMS

Progressive familial intrahepatic cholestasis (PFIC) is a collective term for a heterogenous group of rare, inherited cholestasis syndromes. The number of genes underlying the clinical PFIC phenotype is still increasing. While progressive liver disease and its sequelae such as portal hypertension, pruritus and hepatocellular carcinoma determine transplant-free survival, extrahepatic manifestations may cause relevant morbidity.

METHODS

We performed a literature search for extrahepatic manifestations of PFIC associated with pathogenic gene variants in ATP8B1, ABCB11, ABCB4, TJP2, NR1H4 and MYO5B. To illustrate the extrahepatic symptoms described in the literature, PFIC cases from our centres were revisited.

RESULTS

Extrahepatic symptoms are common in PFIC subtypes, where the affected gene is expressed at high levels in other tissues. While most liver-associated complications resolve after successful orthotopic liver transplantation (OLT), some extrahepatic symptoms show no response or even worsen after OLT.

CONCLUSION

The spectrum of extrahepatic manifestations in PFIC highlights essential, non-redundant roles of the affected genes in other organs. Extrahepatic features contribute towards low health-related quality of life (HRQOL) and morbidity in PFIC. While OLT is often the only remaining, curative treatment, potential extrahepatic manifestations need to be carefully monitored and addressed.

Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy

The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic.

ZO-1 Intracellular Localization Organizes Immune Response in Non-Small Cell Lung Cancer

Delocalization of zonula occludens-1 (ZO-1) from tight junctions plays a substantial role in epithelial cell plasticity observed during tumor progression. In vitro, we reported an impact of ZO-1 cyto-nuclear content in modulating the secretion of several pro-inflammatory chemokines. In vivo, we demonstrated that it promotes the recruitment of immune cells in mouse ear sponge assays. Examining lung cancers, we showed that a high density of CD8 cytotoxic T cells and Foxp3 immunosuppressive regulatory T cells in the tumor microenvironment correlated with a cyto-nuclear expression of ZO-1. Taken together, our results support that, by affecting tumor cell secretome, the cyto-nuclear ZO-1 pool may recruit immune cells, which could be permissive for tumor progression.

Transcriptomic profile of leg muscle during early growth and development in Haiyang yellow chicken

Skeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. This study aimed to identify candidate genes involved in chicken growth and development and to investigate the potential regulatory mechanisms of early growth in Haiyang yellow chicken. RNA sequencing was used to compare the transcriptomes of chicken muscle tissues at four developmental stages. In total, 6150 differentially expressed genes (DEGs) (|fold change| ≥ 2; false discovery rate (FDR) ≤ 0.05) were detected by pairwise comparison in female chickens. Functional analysis showed that the DEGs were mainly involved in the processes of muscle growth and development and cell differentiation. Many of the DEGs, such as MSTN, MYOD1, MYF6, MYF5, and IGF1, were related to chicken growth and development. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the DEGs were significantly enriched in four pathways related to growth and development: extracellular matrix (ECM)–receptor interaction, focal adhesion, tight junction, and insulin signalling pathways. A total of 42 DEGs assigned to these pathways are potential candidate genes for inducing the differences in growth among the four development stages, such as MYH1A, EGF, MYLK2, MYLK4, and LAMB3. This study identified a range of genes and several pathways that may be involved in regulating early growth.

Altered expression of junctional proteins as a potential biomarker in oral precancerous and cancerous patients

Due to a lower survival rate in patients with advanced clinical stages of oral cancer, discovering a biomarker that could diagnose and predict disease progression is vital. Cell-cell junctional proteins play a crucial role in the maintenance of tissue architecture but are often deregulated in different cancer. The present study investigates the expression of cell-cell junctional proteins viz: e-cadherin (E-cad) and zonula occludens-1 (ZO-1) in oral precancerous (OED) and cancerous (OSCC) patients to monitor if they can serve as practicable molecular markers. The ultrastructural junctional complex was studied by transmission electron microscopy, and the expression of proteins was performed by immunohistochemistry. The relationship between the expression of protein and clinicopathological features of the patients was checked by Pearson's correlation test. Furthermore, the survival curve of the follow-up data was estimated by the Kaplan-Meier method. We observed a disrupted junctional complex and a significantly decreased immunoexpression of E-cad and ZO-1 in OED and OSCC when compared to the adjacent non-cancerous tissues. The expression of ZO-1 was associated with TNM stages, whereas E-cad was associated with histological grades as well as TNM stages. A positive correlation was observed between the expression of ZO-1 and E-cad proteins in OED and OSCC. Further, follow-up studies revealed that high ZO-1 and E-cad expressing patients survived longer than their low expressed counterparts. The present study shows disruption of junctional complex and alteration of junctional proteins expression that could draw the attention of health professionals to explore junctional proteins as a possible therapeutic target in oral cancer.

Alterations in fecal short chain fatty acids (SCFAs) and branched short-chain fatty acids (BCFAs) in men with benign prostatic hyperplasia (BPH) and metabolic syndrome (MetS)

Gut microbiome-derived short-chain fatty acids (SCFAs) emerge in the process of fermentation of polysaccharides that resist digestion (dietary fiber, resistant starch). SCFAs have a very high immunomodulatory potential and ensure local homeostasis of the intestinal epithelium, which helps maintain the intestinal barrier. We analyzed the association between stool SCFAs levels acetic acid (C 2:0), propionic acid (C 3:0), isobutyric acid (C 4:0i), butyric acid (C 4:0n), isovaleric acid (C 5:0i) valeric acid (C 5:0n), isocaproic acid (C 6:0i), and caproic acid (C 6:0n)) in aging man with benign prostatic hyperplasia (BPH) and healthy controls. The study involved 183 men (with BPH, n = 103; healthy controls, n = 80). We assessed the content of SCFAs in the stool samples of the study participants using gas chromatography. The levels of branched SCFAs (branched-chain fatty acids, BCFAs): isobutyric acid (C4:0i) (p = 0.008) and isovaleric acid (C5:0i) (p < 0.001) were significantly higher in patients with BPH than in the control group. In healthy participants isocaproic acid (C6:0i) predominated (p = 0.038). We also analyzed the relationship between stool SCFA levels and serum diagnostic parameters for MetS. We noticed a relationship between C3:0 and serum lipid parameters (mainly triglycerides) in both healthy individuals and patients with BPH with regard to MetS. Moreover we noticed relationship between C4:0i, C5:0i and C6:0i and MetS in both groups. Our research results suggest that metabolites of the intestinal microflora (SCFAs) may indicate the proper function of the intestines in aging men, and increased BCFAs levels are associated with the presence of BPH.

Differential Splicing of Skipped-exons Predicts Drug Response in Cancer Cell Lines

Alternative splicing of pre-mRNA transcripts is an important regulatory mechanism that increases the diversity of gene products in eukaryotes. Various studies have linked specific transcript isoforms to altered drug response in cancer; however, few algorithms have incorporated splicing information into drug response prediction. In this study, we evaluated whether basal-level splicing information could be used to predict drug sensitivity by constructing doxorubicin-sensitivity classification models with splicing and expression data. We detailed splicing differences between sensitive and resistant cell lines by implementing quasi-binomial generalized linear modeling (QBGLM) and found altered inclusion of 277 skipped exons. We additionally conducted RNA-binding protein (RBP) binding motif enrichment and differential expression analysis to characterize cis- and trans-acting elements that potentially influence doxorubicin response-mediating splicing alterations. Our results showed that a classification model built with skipped exon data exhibited strong predictive power. We discovered an association between differentially spliced events and epithelial-mesenchymal transition (EMT) and observed motif enrichment, as well as differential expression of RBFOX and ELAVL RBP family members. Our work demonstrates the potential of incorporating splicing data into drug response algorithms and the utility of a QBGLM approach for fast, scalable identification of relevant splicing differences between large groups of samples.

In vitro renal toxicity evaluation of copper-based metal-organic framework HKUST-1 on human embryonic kidney cells

HKUST-1 is currently studied for a very diverse range of applications. Despite its exciting potential, significant concerns remain regarding the safety of HKUST-1. Therefore, human embryonic kidney 293 (HEK293) cells were used to verify the renal toxicity of HKUST-1. In this study, HKUST-1 induced concentration-dependent cytotoxic effects in HEK293 cells. The depolarization of mitochondrial membrane potential and formation of apoptotic bodies and autophagic vesicles were observed in HKUST-1-treated HEK293 cells. Oxidative (oxidative stress and haem oxygenase-1 activation) and inflammatory responses (NF-κB and NLRP3 activation) in HEK293 cells were induced by HKUST-1 exposure. In addition, the observed reduction in NAD(P)H levels in HKUST-1-treated HEK293 cells may be attributable to PARP-1 activation following DNA single- and double-strand breaks. The HKUST-1-induced depletion of zonula occludens proteins in HEK293 cells might lead to altered renal barrier integrity. The variations of α1-antitrypsin, oxidised α1-antitrypsin and NLRP3 protein expression in HEK293 cells suggested that HKUST-1 increases the risk of chronic kidney diseases. However, most of these adverse effects were significantly induced only by high HKUST-1 concentration (100 μg/mL), which do not reflect the actual exposure. Thus, the toxic risk of HKUST-1 appears to be negligible.

Nimbolide inhibits tumor growth by restoring hepatic tight junction protein expression and reduced inflammation in an experimental hepatocarcinogenesis

BACKGROUND

Altered tight junction (TJ) proteins are correlated with carcinogenesis and tumor development. Nimbolide is a tetranotriterpenoid that has been shown to have antioxidant and anti-proliferative properties; however, its anticancer effects and molecular mechanism in hepatocellular carcinoma (HCC) remains obscure.

AIM

To investigate the effect of nimbolide on TJ proteins, cell cycle progression, and hepatic inflammation in a mouse model of HCC.

METHODS

HCC was induced in male Swiss albino mice (CD-1 strain) by a single intraperitoneal injection of 100 mg/kg diethylnitrosamine (DEN) followed by 80 ppm N-nitrosomorpholine (NMOR) in drinking water for 28 wk. After 28 wk, nimbolide (6 mg/kg) was given orally for four consecutive weeks in DEN/NMOR induced HCC mice. At the end of the 32^nd week, all the mice were sacrificed and blood and liver samples were collected for various analyses. Macroscopic examinations of hepatic nodules were assessed. Liver histology and HCC tumor markers such as alpha-fetoprotein (AFP) and glypican-3 were measured. Expression of TJ proteins, cell proliferation, and cell cycle markers, inflammatory markers, and oxidative stress markers were analyzed. In silico analysis was performed to confirm the binding and modulatory effect of nimbolide on zonula occludens 1 (ZO-1), nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB), and tumor necrosis factor alpha (TNF-α).

RESULTS

We found nimbolide treatment at a concentration of 6 mg/kg to HCC mice reduced hepatic tumor size by 52.08% and tumor volume (P < 0.01), and delayed tumor growth in HCC mice with a concomitant reduction in tumor markers such as AFP levels (P < 0.01) and glypican-3 expression (P < 0.05). Furthermore, nimbolide treatment increased tight junction proteins such as ZO-1 and occludin expression (P < 0.05, respectively) and reduced ZO-1 associated nucleic acid binding protein expression (P < 0.001) in HCC mice liver. Nimbolide treatment to HCC mice also inhibited cell proliferation and suppressed cell cycle progression by attenuating proliferating cell nuclear antigen (P < 0.01), cyclin dependent kinase (P < 0.05), and CyclinD1 (P < 0.05) expression. In addition, nimbolide treatment to HCC mice ameliorated hepatic inflammation by reducing NF-κB, interleukin 1 beta and TNF-α expression (P < 0.05, respectively) and abrogated oxidative stress by attenuating 4-hydroxynonenal expression (P < 0.01). Molecular docking studies further confirmed that nimbolide interacts with ZO-1, NF-κB, and TNF-α.

CONCLUSION

Our current study showed for the first time that nimbolide exhibits anticancer effect by reducing tumor size, tumor burden and by suppressing cell cycle progression in HCC mice. Furthermore, nimbolide treatment to HCC mice ameliorated inflammation and oxidative stress, and improved TJ proteins expression. Consequently, nimbolide could be potentially used as a natural therapeutic agent for HCC treatment, however further human studies are warranted.

Junctional Adhesion Molecules in Cancer: A Paradigm for the Diverse Functions of Cell-Cell Interactions in Tumor Progression

Tight junction (TJ) proteins are essential for mediating interactions between adjacent cells and coordinating cellular and organ responses. Initial investigations into TJ proteins and junctional adhesion molecules (JAM) in cancer suggested a tumor-suppressive role where decreased expression led to increased metastasis. However, recent studies of the JAM family members JAM-A and JAM-C have expanded the roles of these proteins to include protumorigenic functions, including inhibition of apoptosis and promotion of proliferation, cancer stem cell biology, and epithelial-to-mesenchymal transition. JAM function by interacting with other proteins through three distinct molecular mechanisms: direct cell-cell interaction on adjacent cells, stabilization of adjacent cell surface receptors on the same cell, and interactions between JAM and cell surface receptors expressed on adjacent cells. Collectively, these diverse interactions contribute to both the pro- and antitumorigenic functions of JAM. In this review, we discuss these context-dependent functions of JAM in a variety of cancers and highlight key areas that remain poorly understood, including their potentially diverse intracellular signaling networks, their roles in the tumor microenvironment, and the consequences of posttranslational modifications on their function. These studies have implications in furthering our understanding of JAM in cancer and provide a paradigm for exploring additional roles of TJ proteins.

E7 oncoprotein from human papillomavirus 16 alters claudins expression and the sealing of epithelial tight junctions

Tight junctions (TJs) are cell-cell adhesion structures frequently altered by oncogenic transformation. In the present study the role of human papillomavirus (HPV) 16 E7 oncoprotein on the sealing of TJs was investigated and also the expression level of claudins in mouse cervix and in epithelial Madin-Darby Canine Kidney (MDCK) cells. It was found that there was reduced expression of claudins -1 and -10 in the cervix of 7-month-old transgenic K14E7 mice treated with 17β-estradiol (E₂), with invasive cancer. In addition, there was also a transient increase in claudin-1 expression in the cervix of 2-month-old K14E7 mice, and claudin-10 accumulated at the border of cells in the upper layer of the cervix in FvB mice treated with E₂, and in K14E7 mice treated with or without E₂. These changes were accompanied by an augmented paracellular permeability of the cervix in 2- and 7-monthold FvB mice treated with E₂, which became more pronounced in K14E7 mice treated with or without E₂. In MDCK cells the stable expression of E7 increased the space between adjacent cells and altered the architecture of the monolayers, induced the development of an acute peak of transepithelial electrical resistance accompanied by a reduced expression of claudins -1, -2 and -10, and an increase in claudin-4. Moreover, E7 enhances the ability of MDCK cells to migrate through a 3D matrix and induces cell stiffening and stress fiber formation. These observations revealed that cell transformation induced by HPV16 E7 oncoprotein was accompanied by changes in the pattern of expression of claudins and the degree of sealing of epithelial TJs.

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.

Sox2 maintains epithelial cell proliferation in the successional dental lamina

OBJECTIVES

The successional dental lamina is the distinctive structure on the lingual side of the vertebrate tooth germ. The aim of this study was to investigate the relationship among Sox2, Claudin10 and laminin5 and the role of Sox2 in successional dental lamina proliferation during vertebrate tooth development.

MATERIALS AND METHODS

To understand the successional dental lamina, two types of successional tooth formation, that in geckos (with multiple rounds of tooth generation) and that in mice (with only one round of tooth generation), were analysed.

RESULTS

Unique coexpression patterns of Sox2 and Claudin10 expression were compared in the successional dental lamina from the cap stage to the late bell stage in the mouse tooth germ and in juvenile gecko teeth to support continuous tooth replacement. Furthermore, Laminin5 expression was shown in the cap stage and decreased after the bell stage. Upon comparing the epithelial cell cycles and cell proliferation in successional dental lamina regions between mouse and gecko molars using BrdU and IdU staining and pulse-chase methods, distinctive patterns of continuous expression were revealed. Moreover, Sox2 overexpression with a lentiviral system resulted in hyperplastic dental epithelium in mouse molars.

CONCLUSIONS

Our findings indicate that the regulation of Sox2 in dental lamina proliferation is fundamental to the successional dental lamina in both species.

R40.76 binds to the α domain of ZO-1: role of ZO-1 (α+) in epithelial differentiation and mechano-sensing

The barrier function of epithelia and endothelia depends on tight junctions, which are formed by the polymerization of claudins on a scaffold of ZO proteins. Two differentially spliced isoforms of ZO-1 have been described, depending on the presence of the α domain, but the function of this domain is unclear. ZO-1 also contains a C-terminal ZU5 domain, which is involved in a mechano-sensitive intramolecular interaction with the central (ZPSG) region of ZO-1. Here we use immunoblotting and immunofluorescence to map the binding sites for commercially available monoclonal and polyclonal antibodies against ZO-1, and for a new polyclonal antibody (R3) that we developed against the ZO-1 C-terminus. We demonstrate that antibody R40.76 binds to the α domain, and the R3 antibody binds to the ZU5 domain. The (α+) isoform of ZO-1 shows higher expression in epithelial versus endothelial cells, and in differentiated versus undifferentiated primary keratinocytes, suggesting a link to epithelial differentiation and a potential molecular adaptation to junctions subjected to stronger mechanical forces. These results provide new tools and hypotheses to investigate the role of the α and ZU5 domains in ZO-1 mechano-sensing and dynamic interactions with the cytoskeleton and junctional ligands.

Joint detection of claudin-1 and junctional adhesion molecule-A as a therapeutic target in oral epithelial dysplasia and oral squamous cell carcinoma

Abnormal expression of claudin-1 (CLDN-1) and junctional adhesion molecule-A (JAM-A) has been described in certain malignancies but their clinical relevance is poorly understood. The present study aims to elucidate the role of CLDN-1 and JAM-A in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Changes in the expression of these proteins were identified immunohistochemically on tissue sections from patients with OED and OSCC and compared with control. A correlation between the expression level of proteins and clinicopathological features was analyzed by Pearson's correlation χ² test. The survival curve of the follow-up data was estimated by the Kaplan-Meier method followed by the log-rank test. CLDN-1 and JAM-A were highly expressed in OED and OSCC tissues when compared to control. Also, delocalization of CLDN-1 from the membrane to the cytoplasm to the nucleus was observed as the cell proceeds from normal to malignancy. Increased expression of CLDN-1 and JAM-A in both OED and OSCC were concomitant with histological grades. In addition, increased JAM-A was associated with perineural invasion of cancer cells. A positive correlation between the expression level of proteins was observed in OED (r = 0.733) and OSCC (r = 0.577). Kaplan-Meier analysis in patients with OSCC showed that the survival rate was lower in patients with high CLDN-1 and high JAM-A expression compared to low expressed patients. To conclude, the elevated level and delocalization of CLDN-1 and JAM-A suggest their use as tumor markers. A positive correlation between CLDN-1 and JAM-A suggests joint detection of these proteins as a future diagnostic tool in oral precancerous and cancerous conditions.

Effects of 17β-Estradiol on Colonic Permeability and Inflammation in an Azoxymethane/Dextran Sulfate Sodium-Induced Colitis Mouse Model

Background/Aims

Intestinal barrier dysfunction is a hallmark of inflammatory bowel diseases (IBDs) such as ulcerative colitis. This dysfunction is caused by increased permeability and the loss of tight junctions in intestinal epithelial cells. The aim of this study was to investigate whether estradiol treatment reduces colonic permeability, tight junction disruption, and inflammation in an azoxymethane (AOM)/dextran sodium sulfate (DSS) colon cancer mouse model.

Methods

The effects of 17β-estradiol (E2) were evaluated in ICR male mice 4 weeks after AOM/DSS treatment. Histological damage was scored by hematoxylin and eosin staining and the levels of the colonic mucosal cytokine myeloperoxidase (MPO) were assessed by enzyme-linked immunosorbent assay (ELISA). To evaluate the effects of E2 on intestinal permeability, tight junctions, and inflammation, we performed quantitative real-time polymerase chain reaction and Western blot analysis. Furthermore, the expression levels of mucin 2 (MUC2) and mucin 4 (MUC4) were measured as target genes for intestinal permeability, whereas zonula occludens 1 (ZO-1), occludin (OCLN), and claudin 4 (CLDN4) served as target genes for the tight junctions.

Results

The colitis-mediated induced damage score and MPO activity were reduced by E2 treatment (p<0.05). In addition, the mRNA expression levels of intestinal barrier-related molecules (i.e., MUC2, ZO-1, OCLN, and CLDN4) were decreased by AOM/DSS-treatment; furthermore, this inhibition was rescued by E2 supplementation. The mRNA and protein expression of inflammation-related genes (i.e., KLF4, NF-κB, iNOS, and COX-2) was increased by AOM/DSS-treatment and ameliorated by E2.

Conclusions

E2 acts through the estrogen receptor β signaling pathway to elicit anti-inflammatory effects on intestinal barrier by inducing the expression of MUC2 and tight junction molecules and inhibiting pro-inflammatory cytokines.

Junctional adhesion molecule-A is down-regulated in anaplastic thyroid carcinomas and reduces cancer cell aggressiveness by modulating p53 and GSK3 α/β pathways

Junctional adhesion molecule A (JAM-A) is a transmembrane protein that contributes to different biological process, including the epithelial to mesenchymal transition (EMT). Through an EMT profiler array, we explored the molecular players associated with human thyroid cancer progression and identified JAM-A as one of the genes mostly deregulated. The quantitative real-time polymerase chain reaction and immunohistochemistry analyses showed that downregulation of JAM-A occurred in anaplastic thyroid carcinoma (ATC) compared with normal thyroid (NT) and papillary thyroid carcinoma (PTC) tissues and correlated with extrathyroid infiltration, tumor size, and ATC histotype. In ATC cell lines, JAM-A restoration suppressed malignant hallmarks of transformation including cell proliferation, motility, and transendothelial migration. Accordingly, knockdown of JAM-A enhanced thyroid cancer cell proliferation and motility in PTC cells. Through the proteome profiler human phospho-kinase array, we demonstrated that higher expression of JAM-A was associated with a significant increased level of phosphorylation of p53 and GSK3 α/β proteins. In conclusion, our findings highlight a novel role of JAM-A in thyroid cancer progression and suggest that JAM-A restoration could have potential clinical relevance in thyroid cancer treatment.

Identification of nucleolar protein NOM1 as a novel nuclear IGF1R-interacting protein

The insulin-like growth factor-1 receptor (IGF1R) mediates the biological actions of both IGF1 and IGF2. In recent years, evidence has accumulated showing that, in addition to its classical cell-surface distribution, IGF1R translocates to cell nucleus via an apparently SUMO-1-dependent mechanism. While the role of IGF1R in nucleus has not yet been settled, available information suggests that the nuclear receptor displays activities usually linked to transcription factors, including DNA binding and transcription regulation. To gain insight into the biological pathways associated with nuclear IGF1R action we conducted a mass spectrometry-based proteomic analysis aimed at identifying interactors of IGF1R in nucleus of both benign and malignant breast cells. The nucleolar NOM1 molecule belongs to a family of proteins that contain the middle domain of eukaryotic initiation factor 4G (MIF4G) and/or interaction module (MA3), and functions in translation, cell growth and proliferation. Using a combination of co-immunoprecipitation and silencing assays we provide evidence of a complex, bi-directional interplay between nuclear IGF1R and nucleolar protein NOM1. Inhibition of nuclear IGF1R translocation by dansylcadaverine reduced NOM1 levels in nuclei of MCF7 cells. On the other hand, IGF1R overexpression enhanced NOM1 levels in the nuclear fraction. Of interest, NOM1 silencing led to a major increase in IGF1R biosynthesis. In summary, results are consistent with a physiologically-relevant interplay between the nuclear IGF1 signaling pathway and nucleolar protein NOM1.

Mutations in Chromatin Modifier and Ephrin Signaling Genes in Vein of Galen Malformation

Normal vascular development includes the formation and specification of arteries, veins, and intervening capillaries. Vein of Galen malformations (VOGMs) are among the most common and severe neonatal brain arterio-venous malformations, shunting arterial blood into the brain's deep venous system through aberrant direct connections. Exome sequencing of 55 VOGM probands, including 52 parent-offspring trios, revealed enrichment of rare damaging de novo mutations in chromatin modifier genes that play essential roles in brain and vascular development. Other VOGM probands harbored rare inherited damaging mutations in Ephrin signaling genes, including a genome-wide significant mutation burden in EPHB4. Inherited mutations showed incomplete penetrance and variable expressivity, with mutation carriers often exhibiting cutaneous vascular abnormalities, suggesting a two-hit mechanism. The identified mutations collectively account for ∼30% of studied VOGM cases. These findings provide insight into disease biology and may have clinical implications for risk assessment.

Claudin 1 Is Highly Upregulated by PKC in MCF7 Human Breast Cancer Cells and Correlates Positively with PKCε in Patient Biopsies

Recent studies provide compelling evidence to suggest that the tight junction protein claudin 1, aberrantly expressed in several cancer types, plays an important role in cancer progression. Dysregulation of claudin 1 has been shown to induce epithelial mesenchymal transition (EMT). Furthermore, activation of the ERK signaling pathway by protein kinase C (PKC) was shown to be necessary for EMT induction. Whether PKC is involved in regulating breast cancer progression has not been addressed. The PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA) was used to investigate the effect of PKC activity on claudin 1 transcription and protein levels, subcellular distribution, and alterations in EMT markers in human breast cancer (HBC) cell lines. As well, tissue microarray analysis (TMA) of a large cohort of invasive HBC biopsies was conducted to investigate correlations between claudin 1 and PKC isomers. TPA upregulated claudin 1 levels in all HBC cell lines analyzed. In particular, a high induction of claudin 1 protein was observed in the MCF7 cell line. TPA treatment also led to an accumulation of claudin 1 in the cytoplasm. Additionally, we demonstrated that the upregulation of claudin 1 was through the ERK signaling pathway. In patient biopsies, we identified a significant positive correlation between claudin 1, PKCα, and PKCε in ER+ tumors. A similar correlation between claudin 1 and PKCε was identified in ER- tumors, and high PKCε was associated with shorter disease-free survival. Collectively, these studies demonstrate that claudin 1 and the ERK signaling pathway are important players in HBC progression.

DNA demethylation of claudin-4 suppresses migration and invasion in laryngeal squamous carcinoma cells

Claudin-4 (CLDN4) is a member of the claudin transmembrane protein family, which consists of integral membrane proteins that are components of the epithelial cell tight junctions; these tight junctions regulate movement of solutes and ions through the paracellular space. CLDN4 is also a differentiation marker and is believed to indicate an epithelial phenotype. However, the role of CLDN4 in laryngeal squamous carcinoma is still unclear. Here, we showed that CLDN4 expression was down-regulated in laryngeal squamous carcinoma tissues and negatively correlated with methyl-CpG-binding protein 2. In addition, CLDN4 was hypermethylated in HEp-2 cells. DNA demethylation of CLDN4 by 5-aza-2'-deoxycytidine suppressed migration and invasion of HEp-2 cells, whereas CLDN4 silencing restored the migration and invasion of HEp-2 cells. Therefore, CLDN4 plays a key role in laryngeal squamous carcinoma progression.

Genome-wide profiling of Sus scrofa circular RNAs across nine organs and three developmental stages

The spatio-temporal expression patterns of Circular RNA (circRNA) across organs and developmental stages are critical for its function and evolution analysis. However, they remain largely unclear in mammals. Here, we comprehensively analysed circRNAs in nine organs and three skeletal muscles of Guizhou miniature pig (S. scrofa), a widely used biomedical model animal. We identified 5,934 circRNAs and analysed their molecular properties, sequence conservation, spatio-temporal expression pattern, potential function, and interaction with miRNAs. S. scrofa circRNAs show modest sequence conservation with human and mouse circRNAs, are flanked by long introns, exhibit low abundance, and are expressed dynamically in a spatio-temporally specific manner. S. scrofa circRNAs show the greatest abundance and complexity in the testis. Notably, 31% of circRNAs harbour well-conserved canonical miRNA seed matches, suggesting that some circRNAs act as miRNAs sponges. We identified 149 circRNAs potentially associated with muscle growth and found that their host genes were significantly involved in muscle development, contraction, chromatin modification, cation homeostasis, and ATP hydrolysis-coupled proton transport; moreover, this set of genes was markedly enriched in genes involved in tight junctions and the calcium signalling pathway. Finally, we constructed the first public S. scrofa circRNA database, allowing researchers to query comprehensive annotation, expression, and regulatory networks of circRNAs.

Evidence that gene expression of ovarian follicular tight junction proteins is regulated in vivo and in vitro in cattle

Tight junctions (TJ) are common paracellular sealing structures that control the transport of water, ions, and macromolecules across cell layers. Because the role of TJ in bovine follicular development is unknown, we investigated the developmental and hormonal regulation of the transmembrane TJ protein, occludin (OCLN), and the cytoplasmic TJ proteins, TJ protein 1 (TJP1) and cingulin (CGN) in bovine granulosa cells (GC) and theca cells (TC). For this purpose, bovine GC and TC were isolated from large (>8 mm) and/or small (1 to 5 mm) follicles and either extracted for real-time PCR (qPCR) or cultured in vitro. The abundances of both and mRNA were greater ( < 0.05) in TC than GC, whereas the mRNA abundance was greater ( < 0.05) in GC than TC. The abundance of mRNA in both GC and TC was greater ( < 0.05) in small follicles compared with large follicles, whereas the GC of large follicles had less ( < 0.05) mRNA abundance than the GC of small follicles. The abundance of mRNA in GC or TC did not differ ( > 0.10) among follicle sizes. In vitro treatment with various growth factors known to affect ovarian folliculogenesis indicated that , , and were hormonally regulated. Fibroblast growth factor 9 (FGF9) decreased ( < 0.05) the and mRNA abundances. Tumor necrosis factor α (TNFα) and vascular endothelial growth factor A (VEGFA) increased ( < 0.05) the mRNA abundance but decreased ( < 0.05) the mRNA abundance. Dexamethasone (DEX) increased ( < 0.05) and mRNA abundances. Epidermal growth factor (EGF) decreased ( < 0.05) and dihydrotestosterone (DHT) increased ( < 0.05) the abundances of , , and mRNA. We propose that the downregulation of OCLN and other TJ proteins during follicular development could reduce barrier function, thereby participating in increasing follicle size by allowing for an increase in the volume of follicular fluid as well as by allowing additional serum factors into the follicular fluid that potentially may directly impact GC functions. The results of the current study indicate the following in cattle: 1) gene expression of TJ proteins (i.e., , , and ) differs between GC and TC and changes with follicle size, and 2) autocrine, paracrine, and endocrine regulators, such as FGF9, EGF, DHT, TNFα, and glucocorticoids, modulate , , and mRNA abundance in TC in vitro.

Comparative analysis of the transcriptome of the overwintering desert beetle Microdera punctipennis

The cold tolerance mechanisms of insect have been studied extensively on the model species Drosophila and a few other species at the transcriptional level. However studies on insects that inherit strong cold tolerance are limited. Cold hardy Tenebrionid beetle Microdera punctipennis is endemic to Gurbantonggut Desert, northwest of China. However, its genomic information is lacking. To investigate the overwintering mechanisms of M. punctipennis adult, RNA-seq was performed on the winter adults and the control adults that were kept in laboratory at 30 °C. A total of 175,247 unigenes were acquired with an average length of 645 bp. By using DESeq package, we identified 3367 unigenes that were up-regulated and 7988 down-regulated in the winter adults compared with the controls. To further our understanding of these differentially expressed genes (DEGs), Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed. Pathway analysis showed that the "ECM-receptor interaction", "PI3K-Akt signaling pathway", "Estrogen signaling pathway", "Tight junction", and "Regulation of actin cytoskeleton", etc. might play important roles in M. punctipennis overwintering. The DEGs results from the RNA-Seq were confirmed partially by qRT-PCR for 13 DEGs, which showed high consistence with a Pearson's correlation coefficient of 0.851. Overall, the sequence data will provide basic information for subsequent bioinformatical analysis and mining of the genes responsible for cold tolerance in M. punctipennis, as well as for understanding the molecular mechanisms of desert beetle overwintering.

Celiac disease: From pathophysiology to treatment

Celiac disease, also known as "celiac sprue", is a chronic inflammatory disorder of the small intestine, produced by the ingestion of dietary gluten products in susceptible people. It is a multifactorial disease, including genetic and environmental factors. Environmental trigger is represented by gluten while the genetic predisposition has been identified in the major histocompatibility complex region. Celiac disease is not a rare disorder like previously thought, with a global prevalence around 1%. The reason of its under-recognition is mainly referable to the fact that about half of affected people do not have the classic gastrointestinal symptoms, but they present nonspecific manifestations of nutritional deficiency or have no symptoms at all. Here we review the most recent data concerning epidemiology, pathogenesis, clinical presentation, available diagnostic tests and therapeutic management of celiac disease.

Group B adenovirus enadenotucirev infects polarised colorectal cancer cells efficiently from the basolateral surface expected to be encountered during intravenous delivery to treat disseminated cancer

Enadenotucirev (EnAd) is a group B oncolytic adenovirus developed for systemic delivery and currently undergoing clinical evaluation for advanced cancer therapy. For differentiated carcinomas, systemic delivery would likely expose virus particles to the basolateral surface of cancer cells rather than the apical surface encountered during natural infection. Here, we compare the ability of EnAd and adenovirus type-5 (Ad5) to infect polarised colorectal carcinoma cells from the apical or basolateral surfaces. Whereas Ad5 infection was more efficient via the apical than basolateral surface, EnAd readily infected cells from either surface. Progeny particles from EnAd were released preferentially via the apical surface for all cell lines and routes of infection. These data further support the utility of group B adenoviruses for systemic delivery and suggest that progeny virus are more likely to be released into the tumour rather than back through the basolateral surface into the blood stream.

Exfoliated graphene nanosheets: pH-sensitive drug carrier and anti-cancer activity

A straightforward and facile method for the exfoliation of graphene sheets using poly(vinylpyrrolidone) nanoparticles of an average size of 42nm was developed and their dual role as pH-sensitive drug carrier and anti-cancer agent was evaluated. The cytotoxic impact of the exfoliated nanosheets (GRP-PVP-NP) was examined on various cells (HCT-116, HeLa, SCC-9, NIH-3T3 and HEK-293cells) by a series of assays. Their cytotoxic nature was attributed to affecting the mitochondrial enzyme activity, proliferation capability, and the formation of tight junctions in cancer cells. The endocytosis was found to be internalization mechanism for the cellular uptake of nanosheets. The generation of reactive oxygen species and elicitation of caspase-3 activity which was undoubtedly associated with triggering of oxidative stress speculated to be the dominant cause of the cytotoxic pattern of nanosheets against cancer cells. Additionally, the results also showed the role of the nanosheets as a pH-sensitive drug carrier through drug loading by supramolecular interaction. The efficient release of doxorubicin was seen at low pH and in an environment with a low oxygen concentration, thus under conditions mimicking the typical tumor microenvironment. Therefore, these findings provide the first evidence for a dual function of exfoliated graphene sheets and also elucidate the cytotoxic mechanism responsible for the cancer cell death.

Transcriptomic profile of leg muscle during early growth in chicken

The early growth pattern, especially the age of peak growth, of broilers affects the time to market and slaughter weight, which in turn affect the profitability of the poultry industry. However, the underlying mechanisms regulating chicken growth and development have rarely been studied. This study aimed to identify candidate genes involved in chicken growth and investigated the potential regulatory mechanisms of early growth in chicken. RNA sequencing was applied to compare the transcriptomes of chicken muscle tissues at three developmental stages during early growth. In total, 978 differentially expressed genes (DEGs) (fold change ≥ 2; false discovery rate < 0.05) were detected by pairwise comparison. Functional analysis showed that the DEGs are mainly involved in the processes of cell growth, muscle development, and cellular activities (such as junction, migration, assembly, differentiation, and proliferation). Many of the DEGs are well known to be related to chicken growth, such as MYOD1, GH, IGF2BP2, IGFBP3, SMYD1, CEBPB, FGF2, and IGFBP5. KEGG pathway analysis identified that the DEGs were significantly enriched in five pathways (P < 0.1) related to growth and development: extracellular matrix–receptor interaction, focal adhesion, tight junction, insulin signaling pathway, and regulation of the actin cytoskeleton. A total of 42 DEGs assigned to these pathways are potential candidate genes inducing the difference in growth among the three developmental stages, such as MYH10, FGF2, FGF16, FN1, CFL2, MAPK9, IRS1, PHKA1, PHKB, and PHKG1. Thus, our study identified a series of genes and several pathways that may participate in the regulation of early growth in chicken. These results should serve as an important resource revealing the molecular basis of chicken growth and development.

Nuclear localization of tricellulin promotes the oncogenic property of pancreatic cancer

Accumulating evidence has shown that dysregulation of tight junctions (TJs) is involved in tumor development and progression. In this study, we investigated the expression and subcellular distribution of tricellulin, which constitutes tricellular TJs, using human pancreatic adenocarcinomas. In well-differentiated pancreatic adenocarcinoma tissues, tricellulin immunostaining was prominent in the cytoplasm and the plasma membrane. In contrast, in poorly differentiated tissues, its immunostaining was predominantly observed in the nuclei and was almost absent in the plasma membrane. The distinct immunostaining of tricellulin successfully distinguished poorly differentiated adenocarcinoma from moderately and well-differentiated adenocarcinomas with high levels of sensitivity and specificity. Nuclear tricellulin expression significantly correlated with lymph node metastasis, lymphatic invasion and poor survival. In pancreatic cancer cell lines, tricellulin localization shifted from the membrane to nucleus with decreasing differentiation status. Nuclear localization of tricellulin promoted cell proliferation and invasiveness possibly in association with MAPK and PKC pathways in pancreatic cancers. Our results provide new insights into the function of tricellulin, and its nuclear localization may become a new prognostic factor for pancreatic cancers.

Claudin 8 Contributes to Malignant Proliferation in Human Osteosarcoma U2OS Cells

Human osteosarcoma (OS) represents one of the most common primary sarcomas often originating in the metaphyses of long bones. However, its underlying molecular pathogenesis is still only vaguely understood. Several tight junction proteins were shown to be associated with and involved in tumorigenesis. This study is aimed to evaluate the role of Claudin 8 (CLDN8) in human OS. Lentivirus-based short hairpin RNA targeting CLDN8 specifically depleted its endogenous expression in U2OS and SW1353 OS cells, with a reduction by 97.7% and 89.3%, respectively, in contrast to control. Depletion of CLDN8 led to a significant diminution in cell viability and proliferation. To test the mechanism by which CLDN8 modulates cell proliferation, the flow cytometry assay and apoptosis assay were performed and confirmed that G1-S transition was blocked and a strong proapoptotic effect was induced in U2OS cells by CLDN8 knockdown. These data demonstrate that CLDN8 plays an essential role in OS proliferation in vitro, which will provide a new opportunity for discovering and identifying novel effective treatment strategies.

Occludin S471 Phosphorylation Contributes to Epithelial Monolayer Maturation

Multiple organ systems require epithelial barriers for normal function, and barrier loss is a hallmark of diseases ranging from inflammation to epithelial cancers. However, the molecular processes regulating epithelial barrier maturation are not fully elucidated. After contact, epithelial cells undergo size-reductive proliferation and differentiate, creating a dense, highly ordered monolayer with high resistance barriers. We provide evidence that the tight junction protein occludin contributes to the regulation of epithelial cell maturation upon phosphorylation of S471 in its coiled-coil domain. Overexpression of a phosphoinhibitory occludin S471A mutant prevents size-reductive proliferation and subsequent tight junction maturation in a dominant manner. Inhibition of cell proliferation in cell-contacted but immature monolayers recapitulated this phenotype. A kinase screen identified G-protein-coupled receptor kinases (GRKs) targeting S471, and GRK inhibitors delayed epithelial packing and junction maturation. We conclude that occludin contributes to the regulation of size-reductive proliferation and epithelial cell maturation in a phosphorylation-dependent manner.

Resveratrol induces chemosensitization to 5-fluorouracil through up-regulation of intercellular junctions, Epithelial-to-mesenchymal transition and apoptosis in colorectal cancer

5-Fluorouracil (5-FU), a common chemotherapeutic agent used for the treatment of colorectal cancer (CRC), by itself has inadequate response rates; highlighting the need for novel and improved treatment regimens for these patients. Resveratrol, a naturally-occurring polyphenol, has been linked with chemosensitizing potential and anticancer properties; however, the underlying mechanisms for these effects remain poorly understood. The effect of resveratrol in parental CRC cell lines (HCT116, SW480) and their corresponding isogenic 5-FU-chemoresistant derived clones (HCT116R, SW480R) was examined by MTT assays, intercellular junction formation and apoptosis by electron- and immunoelectron microscopy, nuclear factor-kappaB (NF-κB) and NF-κB regulated gene products by western blot analysis in a 3D-alginate microenvironment. Resveratrol blocked the proliferation of all four CRC cell lines and synergized the invasion inhibitory effects of 5-FU. Interestingly, resveratrol induced a transition from 5-FU-induced formation of microvilli to a planar cell surface, which was concomitant with up-regulation of desmosomes, gap- and tight junctions (claudin-2) and adhesion molecules (E-cadherin) expression in HCT116 and HCT116R cells. Further, resveratrol significantly attenuated drug resistance through inhibition of epithelial-mesenchymal transition (EMT) factors (decreased vimentin and slug, increased E-cadherin) and down-regulation of NF-κB activation and its translocation to the nucleus and abolished NF-κB-regulated gene end-products (MMP-9, caspase-3). Moreover, this suppression was mediated through inhibition of IκBα kinase and IκBα phosphorylation and degradation. Our results demonstrate that resveratrol can potentiate the anti-tumor effects of 5-FU on CRC cells by chemosensitizing them, inhibiting an EMT phenotype via up-regulation of intercellular junctions and by down-regulation of NF-κB pathway.

The Expression of the Zonula Adhaerens Protein PLEKHA7 Is Strongly Decreased in High Grade Ductal and Lobular Breast Carcinomas

PLEKHA7 is a junctional protein, which participates in a complex that stabilizes E-cadherin at the zonula adhaerens. Since E-cadherin is involved in epithelial morphogenesis, signaling, and tumor progression, we explored PLEKHA7 expression in cancer. PLEKHA7 expression was assessed in invasive ductal and lobular carcinomas of the breast by immunohistochemistry, immunofluorescence and quantitative RT-PCR. PLEKHA7 was detected at epithelial junctions of normal mammary ducts and lobules, and of tubular and micropapillary structures within G1 and G2 ductal carcinomas. At these junctions, the localization of PLEKHA7 was along the circumferential belt (zonula adhaerens), and only partially overlapping with that of E-cadherin, p120ctn and ZO-1, as shown previously in rodent tissues. PLEKHA7 immunolabeling was strongly decreased in G3 ductal carcinomas and undetectable in lobular carcinomas. PLEKHA7 mRNA was detected in both ductal and lobular carcinomas, with no observed correlation between mRNA levels and tumor type or grade. In summary, PLEKHA7 is a junctional marker of epithelial cells within tubular structures both in normal breast tissue and ductal carcinomas, and since PLEKHA7 protein but not mRNA expression is strongly decreased or lost in high grade ductal carcinomas and in lobular carcinomas, loss of PLEKHA7 is a newly characterized feature of these carcinomas.

A non-tight junction function of claudin-7-Interaction with integrin signaling in suppressing lung cancer cell proliferation and detachment

Background

Claudins are a family of tight junction (TJ) membrane proteins involved in a broad spectrum of human diseases including cancer. Claudin-7 is a unique TJ membrane protein in that it has a strong basolateral membrane distribution in epithelial cells and in tissues. Therefore, this study aims to investigate the functional significance of this non-TJ localization of claudin-7 in human lung cancer cells.

Methods

Claudin-7 expression was suppressed or deleted by lentivirus shRNA or by targeted-gene deletion. Cell cycle analysis and antibody blocking methods were employed to assay cell proliferation and cell attachment, respectively. Electron microscopy and transepthelial electrical resistance measurement were performed to examine the TJ ultrastructure and barrier function. Co-immunolocalization and co-immunoprecipitation was used to study claudin-7 interaction with integrin β1. Tumor growth in vivo were analyzed using athymic nude mice.

Results

Claudin-7 co-localizes and forms a stable complex with integrin β1. Both suppressing claudin-7 expression by lentivirus shRNA in human lung cancer cells (KD cells) and deletion of claudin-7 in mouse lungs lead to the reduction in integrin β1 and phospho-FAK levels. Suppressing claudin-7 expression increases cell growth and cell cycle progression. More significantly, claudin-7 KD cells have severe defects in cell-matrix interactions and adhere poorly to culture plates with a remarkably reduced integrin β1 expression. When cultured on uncoated glass coverslips, claudin-7 KD cells grow on top of each other and form spheroids while the control cells adhere well and grow as a monolayer. Reintroducing claudin-7 reduces cell proliferation, upregulates integrin β1 expression and increases cell-matrix adhesion. Integrin β1 transfection partially rescues the cell attachment defect. When inoculated into nude mice, claudin-7 KD cells produced significantly larger tumors than control cells.

Conclusion

In this study, we identified a previously unrecognized function of claudin-7 in regulating cell proliferation and maintaining epithelial cell attachment through engaging integrin β1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0387-0) contains supplementary material, which is available to authorized users.

Claudins and cancer: Fall of the soldiers entrusted to protect the gate and keep the barrier intact

The role of the tight junctions (TJ) in controlling paracellular traffic of ions and molecules, through the regulation of claudin proteins, is now established. However, it has also become increasingly evident that claudin proteins, as integral components of the TJs, play crucial role in maintaining the cell-cell integrity. In conformity, deregulation of claudin expression and cellular distribution in cancer tissues has been widely documented and correlated with cancer progression and metastasis. However, this correlation is not unidirectional and rather suggests tissue specific regulations. Irrespective, if the widely described correlations between altered claudin expression and cancer initiation/progression could be established, they may serve as important markers for prognostic purposes and potential therapeutic targets. In this review, we summarize data from screening of the cancer tissues, manipulation of claudin expression in cells and animals subjected to cancer models, and how claudins are regulated in cancer. The focus of this article remains analysis of the association between cancer and the claudins and to decipher clinical relevance.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

Temporal and spatial expression of tight junction genes during zebrafish pronephros development

The kidney is comprised of nephrons - epithelial tubes with specialized segments that reabsorb and secrete solutes, perform osmoregulation, and produce urine. Different nephron segments exhibit unique combinations of ion channels, transporter proteins, and cell junction proteins that govern permeability between neighboring cells. The zebrafish pronephros is a valuable model to study the mechanisms of vertebrate nephrogenesis, but many basic features of segment gene expression in renal progenitors and mature nephrons have not been characterized. Here, we analyzed the temporal and spatial expression pattern of tight junction components during zebrafish kidney ontogeny. During nephrogenesis, renal progenitors show discrete expression domains of claudin (cldn) 15a, cldn8, occludin (ocln) a, oclnb, tight junction protein (tjp) 2a, tjp2b, and tjp3. Interestingly, transcripts encoding these genes exhibit dynamic spatiotemporal domains during the time when pronephros segment domains are established. These data provide a useful gene expression map of cell junction components during zebrafish nephrogenesis. As such, this information complements the existing molecular map of nephron segment characteristics, and can be used to characterize kidney development mutants as well as various disease models, in addition to aiding in the elucidation of mechanisms governing epithelial regeneration after acute nephron injury.

Targeting tight junctions during epithelial to mesenchymal transition in human pancreatic cancer

Pancreatic cancer continues to be a leading cause of cancer-related death worldwide and there is an urgent need to develop novel diagnostic and therapeutic strategies to reduce the mortality of patients with this disease. In pancreatic cancer, some tight junction proteins, including claudins, are abnormally regulated and therefore are promising molecular targets for diagnosis, prognosis and therapy. Claudin-4 and -18 are overexpressed in human pancreatic cancer and its precursor lesions. Claudin-4 is a high affinity receptor of Clostridium perfringens enterotoxin (CPE). The cytotoxic effects of CPE and monoclonal antibodies against claudin-4 are useful as novel therapeutic tools for pancreatic cancer. Claudin-18 could be a putative marker and therapeutic target with prognostic implications for patients with pancreatic cancer. Claudin-1, -7, tricellulin and marvelD3 are involved in epithelial to mesenchymal transition (EMT) of pancreatic cancer cells and thus might be useful as biomarkers during disease. Protein kinase C is closely related to EMT of pancreatic cancer and regulates tight junctions of normal human pancreatic duct epithelial cells and the cancer cells. This review focuses on the regulation of tight junctions via protein kinase C during EMT in human pancreatic cancer for the purpose of developing new diagnostic and therapeutic modalities for pancreatic cancer.

Epistemology of the origin of cancer: a new paradigm

Background

Carcinogenesis is widely thought to originate from somatic mutations and an inhibition of growth suppressors, followed by cell proliferation, tissue invasion, and risk of metastasis. Fewer than 10% of all cancers are hereditary; the ratio in gastric (1%), colorectal (3-5%) and breast (8%) cancers is even less. Cancers caused by infection are thought to constitute some 15% of the non-hereditary cancers. Those remaining, 70 to 80%, are called “sporadic,” because they are essentially of unknown etiology. We propose a new paradigm for the origin of the majority of cancers.

Presentation of hypothesis

Our paradigm postulates that cancer originates following a sequence of events that include (1) a pathogenic stimulus (biological or chemical) followed by (2) chronic inflammation, from which develops (3) fibrosis with associated changes in the cellular microenvironment. From these changes a (4) pre-cancerous niche develops, which triggers the deployment of (5) a chronic stress escape strategy, and when this fails to resolve, (6) a transition of a normal cell to a cancer cell occurs. If we are correct, this paradigm would suggest that the majority of the findings in cancer genetics so far reported are either late events or are epiphenomena that occur after the appearance of the pre-cancerous niche.

Testing the hypothesis

If, based on experimental and clinical findings presented here, this hypothesis is plausible, then the majority of findings in the genetics of cancer so far reported in the literature are late events or epiphenomena that could have occurred after the development of a PCN. Our model would make clear the need to establish preventive measures long before a cancer becomes clinically apparent. Future research should focus on the intermediate steps of our proposed sequence of events, which will enhance our understanding of the nature of carcinogenesis. Findings on inflammation and fibrosis would be given their warranted importance, with research in anticancer therapies focusing on suppressing the PCN state with very early intervention to detect and quantify any subclinical inflammatory change and to treat all levels of chronic inflammation and prevent fibrotic changes, and so avoid the transition from a normal cell to a cancer cell.

Implication of the hypothesis

The paradigm proposed here, if proven, spells out a sequence of steps, one or more of which could be interdicted or modulated early in carcinogenesis to prevent or, at a minimum, slow down the progression of many cancers.

DLG5 in cell polarity maintenance and cancer development

Failure in establishment and maintenance of epithelial cell polarity contributes to tumorigenesis. Loss of expression and function of cell polarity proteins is directly related to epithelial cell polarity maintenance. The polarity protein discs large homolog 5 (DLG5) belongs to a family of molecular scaffolding proteins called Membrane Associated Guanylate Kinases (MAGUKs). As the other family members, DLG5 contains the multi-PDZ, SH3 and GUK domains. DLG5 has evolved in the same manner as DLG1 and ZO1, two well-studied MAGUKs proteins. Just like DLG1 and ZO1, DLG5 plays a role in cell migration, cell adhesion, precursor cell division, cell proliferation, epithelial cell polarity maintenance, and transmission of extracellular signals to the membrane and cytoskeleton. Since the roles of DLG5 in inflammatory bowel disease (IBD) and Crohn's disease (CD) have been reviewed, here, our review focuses on the roles of DLG5 in epithelial cell polarity maintenance and cancer development.