CLDN8, an androgen-regulated gene, promotes prostate cancer cell proliferation and migration

Expression and Targeted Application of Claudins Family in Hepatobiliary and Pancreatic Diseases

Hepatobiliary and pancreatic diseases are becoming increasingly common worldwide and associated cancers are prone to recurrence and metastasis. For a more accurate treatment, new therapeutic strategies are urgently needed. The claudins (CLDN) family comprises a class of membrane proteins that are the main components of tight junctions, and are essential for forming intercellular barriers and maintaining cellular polarity. In mammals, the claudin family contains at least 27 transmembrane proteins and plays a major role in mediating cell adhesion and paracellular permeability. Multiple claudin proteins are altered in various cancers, including gastric cancer (GC), esophageal cancer (EC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), colorectal cancer (CRC) and breast cancer (BC). An increasing number of studies have shown that claudins are closely associated with the occurrence and development of hepatobiliary and pancreatic diseases. Interestingly, claudin proteins exhibit different effects on cancer progression in different tumor tissues, including tumor suppression and promotion. In addition, various claudin proteins are currently being studied as potential diagnostic and therapeutic targets, including claudin-3, claudin-4, claudin-18.2, etc. In this article, the functional phenotype, molecular mechanism, and targeted application of the claudin family in hepatobiliary and pancreatic diseases are reviewed, with an emphasis on claudin-1, claudin-4, claudin-7 and claudin-18.2, and the current situation and future prospects are proposed.

Significance and Possible Biological Mechanism for CLDN8 Downregulation in Kidney Renal Clear Cell Carcinoma Tissues

Background

The clinical role of claudin 8 (CLDN8) in kidney renal clear cell carcinoma (KIRC) remains unclarified. Herein, the expression level and potential molecular mechanisms of CLDN8 underlying KIRC were determined.

Methods

High-throughput datasets of KIRC were collected from GEO, ArrayExpress, SRA, and TCGA databases to determine the mRNA expression level of the CLDN8. In-house tissue microarrays and immunochemistry were performed to examine CLDN8 protein expression. A summary receiver operating characteristic curve (SROC) and standardized mean difference (SMD) forest plot were generated using Stata v16.0. Single-cell analysis was conducted to further prove the expression level of CLDN8. A clustered regularly interspaced short palindromic repeats knockout screen analysis was executed to assess the growth impact of CLDN8. Functional enrichment analysis was conducted using the Metascape database. Additionally, single-sample gene set enrichment analysis was implied to explore immune cell infiltration in KIRC.

Results

A total of 17 mRNA datasets comprising 1,060 KIRC samples and 452 non-cancerous control samples were included in this study. Additionally, 105 KIRC and 16 non-KIRC tissues were analyzed using in-house immunohistochemistry. The combined SMD was -5.25 (95% confidence interval (CI): -6.13 to -4.37), and CLDN8 downregulation yielded an SROC area under the curve (AUC) close to 1.00 (95% CI: 0.99 - 1.00). CLDN8 downregulation was also confirmed at the single-cell level. Knocking out CLDN8 stimulated KIRC cell proliferation. Lower CLDN8 expression was correlated with worse overall survival of KIRC patients (hazard ratio of CLDN8 downregulation = 1.69, 95% CI: 1.2 - 2.4). Functional pathways associated with CLDN8 co-expressed genes were centered on carbon metabolism obstruction, with key hub genes ACADM, ACO2, NDUFS1, PDHB, SDHD, SUCLA2, SUCLG1, and SUCLG2.

Conclusions

CLDN8 is downregulated in KIRC and is considered a potential tumor suppressor. CLDN8 deficiency may promote the initiation and progression of KIRC, potentially in conjunction with metabolic dysfunction.

CircSCNN1A inhibits the proliferation, migration and invasion of renal cell carcinoma cells by decreasing CLDN8 expression through miR-590-5p

BACKGROUND

Increasing evidence suggests that circular RNA (circRNA) plays a regulatory role in the progression of renal cell carcinoma (RCC). However, the precise function and underlying mechanism of circSCNN1A in RCC progression still remain unclear.

METHODS

The expression levels of circSCNN1A, microRNA-590-5p (miR-590-5p), claudin 8 (CLDN8), cyclin D1, matrix metalloprotein 2 (MMP2), MMP9, E-cadherin, N-cadherin and vimentin were detected by a quantitative real-time polymerase chain reaction and Western blotting analysis. Immunohistochemistry assay was performed to analyze the positive expression rate of CLDN8. Cell proliferation was investigated by cell colony formation, 5-Ethynyl-2'-deoxyuridine and DNA content quantitation assays. Cell migration and invasion were assessed by wound-healing and transwell invasion assays. Interactions among circSCNN1A, miR-590-5p and CLDN8 were identified by dual-luciferase reporter assay, RNA immunoprecipitation assay and RNA pull-down assay. Xenograft mouse model assay was conducted to verify the effect of circSCNN1A on tumor formation in vivo.

RESULTS

CircSCNN1A and CLDN8 expression were significantly downregulated, while miR-590-5p was upregulated in both RCC tissues and cells. CircSCNN1A overexpression inhibited RCC cell proliferation, migration and invasion, accompanied by decreases of cyclin D1, MMP2, MMP9, N-cadherin and vimentin expression and an increase of E-cadherin expression. CircSCNN1A acted as a miR-590-5p sponge and regulated RCC cell processes by binding to miR-590-5p. CLDN8, a target gene of miR-590-5p, was involved in the regulation of the biological behaviors of RCC cells by miR-590-5p. In addition, circSCNN1A induced CLDN8 production by interacting with miR-590-5p. Further, circSCNN1A suppressed tumor formation in vivo.

CONCLUSION

CircSCNN1A inhibited RCC cell proliferation, migration and invasion by regulating the miR-590-5p/CLDN8 pathway.

Claudins in genitourinary tract neoplasms: mechanisms, prognosis, and therapeutic prospects

Genitourinary (GU) cancers are among the most prevalent neoplasms in the world, with bladder cancers constituting 3% of global cancer diagnoses. However, several pathogenetic mechanisms remain controversial and unclear. Claudins, for example, have been shown to play a significant role in several cancers of the human body. Their role in GU cancers has not been extensively studied. Aberrant expression of claudins -1, -2, -3, -4, -7, and -11 has been expressed in urothelial cell carcinomas. In prostate cancers, altered levels of claudins -1, -2, -3, -4, and -5 have been reported. Furthermore, the levels of claudins -1, -2, -3, -4, -6, -7, -8, and -10 have been studied in renal cell carcinomas. Specifically, claudins -7 and -8 have proven especially useful in differentiating between chromophobe renal cell carcinomas and oncocytomas. Several of these claudins also correlate with clinicopathologic parameters and prognosis in GU cancers. Although mechanisms underpinning aberrant expression of claudins in GU cancers are unclear, epigenetic changes, tumor necrosis factor-ɑ, and the p63 protein have been implicated. Claudins also provide therapeutic value through tailored immunotherapy via molecular subtyping and providing therapeutic targets, which have shown positive outcomes in preclinical studies. In this review, we aim to summarize the literature describing aberrant expression of claudins in urothelial, prostatic, and renal cell carcinomas. Then, we describe the mechanisms underlying these changes and the therapeutic value of claudins. Understanding the scope of claudins in GU cancers paves the way for several diagnostic, prognostic, and therapeutic innovations.

Expression patterns of claudins in cancer

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

Tight junction proteins related to blood-brain barrier and their regulatory signaling pathways in ischemic stroke

Tight junctions (TJs) are crucial for intercellular connections. The abnormal expression of proteins related to TJs can result in TJ destruction, structural damage, and endothelial and epithelial cell dysfunction. These factors are associated with the occurrence and progression of several diseases. Studies have shown that blood-brain barrier (BBB) damage and dysfunction are the prominent pathological features of stroke. TJs are directly associated with the BBB integrity. In this article, we first discuss the structure and function of BBB TJ-related proteins before focusing on the crucial events that cause TJ dysfunction and BBB damage, as well as the regulatory mechanisms that affect the qualitative and quantitative expression of TJ proteins during ischemic stroke. Multiple regulatory mechanisms, including phosphorylation, matrix metalloproteinases (MMPs), and microRNAs, regulate TJ-related proteins and affect BBB permeability. Some signaling pathways and mechanisms have been demonstrated to have dual functions. Hopefully, our understanding of the regulation of BBB TJs in ischemic stroke will be applied to the development of targeted medications and therapeutic therapies.

DNA Methylation Landscapes of Prostate Cancer Brain Metastasis Are Shaped by Early Driver Genetic Alterations

Metastases from primary prostate cancers to rare locations, such as the brain, are becoming more common due to longer life expectancy resulting from improved treatments. Epigenetic dysregulation is a feature of primary prostate cancer, and distinct DNA methylation profiles have been shown to be associated with the mutually exclusive SPOP-mutant or TMPRSS2-ERG fusion genetic backgrounds. Using a cohort of prostate cancer brain metastases (PCBM) from 42 patients, with matched primary tumors for 17 patients, we carried out a DNA methylation analysis to examine the epigenetic distinction between primary prostate cancer and PCBM, the association between epigenetic alterations and mutational background, and particular epigenetic alterations that may be associated with PCBM. Multiregion sampling of PCBM revealed epigenetic stability within metastases. Aberrant methylation in PCBM was associated with mutational background and PRC2 complex activity, an effect that is particularly pronounced in SPOP-mutant PCBM. While PCBM displayed a CpG island hypermethylator phenotype, hypomethylation at the promoters of genes involved in neuroactive ligand-receptor interaction and cell adhesion molecules such as GABRB3, CLDN8, and CLDN4 was also observed, suggesting that cells from primary tumors may require specific reprogramming to form brain metastasis. This study revealed the DNA methylation landscapes of PCBM and the potential mechanisms and effects of PCBM-associated aberrant DNA methylation.

SIGNIFICANCE

DNA methylation analysis reveals the molecular characteristics of PCBM and may serve as a starting point for efforts to identify and target susceptibilities of these rare metastases.

Differential DNA-binding and cofactor recruitment are possible determinants of the synthetic steroid YK11-dependent gene expression by androgen receptor in breast cancer MDA-MB 453 cells

Recently, selective androgen receptor modulators (SARMs), which bind to AR and act in a tissue/effect-specific manner, have been developed, but the selective mechanism is not well understood. In this study, we investigated the selective mechanism using the synthetic steroid YK11, which showed AR-mediated gene-selective transactivation. In the AR-positive human breast cancer MDA-MB-453 cells, different patterns of AR-mediated target gene expression and AR recruitment to their enhancer regions were observed between DHT and YK11. A docking study suggested the helices 11 and 12 was moved by the sterically hindered C17-group of YK11. Furthermore, the mutational studies of AR Gln902 and mammalian two-hybrid assays suggested different cofactor recruitment between DHT and YK11. The results of this study suggest that gene selective regulation by SARMs results from differential DNA-binding and/or cofactor recruitment by ligands. These results provide novel insights into the mechanism of action of SARMs.

Histone methyltransferase KMT2C plays an oncogenic role in prostate cancer

PURPOSE

Prostate cancer (PCa) is a leading cause of morbidity and mortality in males. Epigenetic modifier abnormalities are becoming a driving event in PCa. The specific role of KMT2C, a histone methyltransferase that is frequently aberrant in various tumors, is poorly understood in PCa. This study aimed to reveal the potential carcinogenic role of KMT2C in PCa.

METHODS

We first examined the expression levels of KMT2C in prostate cancer tissues. Then, we assessed the function of KMT2C in prostate cancer cell proliferation, colony formation, and migration. To explore the mechanism of the biological consequences, RNA-seq and CHIP-qPCR were performed. We also analyzed the effects of overexpression of the KMT2C downstream genes CLDN8 and ITGAV to reverse the effects of KMT2C on prostate cancer cells.

RESULTS

Herein, we first confirmed KMT2C overexpression in PCa at the transcript and protein levels. Knocking down KMT2C in VCaP and LNCaP cells inhibited cell viability, colony formation, and migration. Consistently, stable KMT2C depletion effectively decreased tumor growth by approximately 70% in vivo. Mechanistically, the results suggested that CLDN8 and ITGAV are two key downstream genes of KMT2C and further regulate the MAPK/ERK and EMT pathways.

CONCLUSION

Our study suggests that KMT2C plays an oncogenic role in PCa. One of the mechanisms may be the epigenetic regulation of CLDN8 and ITGAV by KMT2C to modulate tumor-signaling pathways. Therefore, KMT2C may serve as a potential therapeutic target for PCa patients.

Dysregulated expression of claudins in cancer

Claudins are adhesion molecules located at the tight junctions between epithelial cells. A series of studies have now reported aberrant expression of claudin proteins in the context of neoplastic transformation, suggesting its role in tumorigenesis. However, the precise mechanisms are still not well understood. Studies on expression alterations of claudins have revealed a range of outcomes that reflect the complexity of claudins in terms of spatial localization, tumor type and stage of disease. The diverse and dynamic expression patterns of claudins in cancer are tightly controlled by a wide range of regulatory mechanisms, which are commonly modulated by oncogenic signaling pathways. The present review summarizes the recent knowledge describing the dysregulation of claudin expression in cancer and discusses the intrinsic and extrinsic determinants of the context-specific expression patterns of claudins.

Colon epithelial cell TGFβ signaling modulates the expression of tight junction proteins and barrier function in mice

Defective barrier function is a predisposing factor in inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Although TGFβ signaling defects have been associated with IBD and CAC, few studies have examined the relationship between TGFβ and intestinal barrier function. Here, we examine the role of TGFβ signaling via SMAD4 in modulation of colon barrier function. The Smad4 gene was conditionally deleted in the intestines of adult mice and intestinal permeability assessed using an in vivo 4 kDa FITC-Dextran (FD4) permeability assay. Mouse colon was isolated for gene expression (RNA-sequencing), Western blot, and immunofluorescence analysis. In vitro colon organoid culture was utilized to assess junction-related gene expression by qPCR and transepithelial resistance (TER). In silico analyses of human IBD and colon cancer databases were performed. Mice lacking intestinal expression of Smad4 demonstrate increased colonic permeability to FD4 without gross mucosal damage. mRNA/protein expression analyses demonstrate significant increases in Cldn2/Claudin 2 and Cldn8/Claudin 8, and decreases in Cldn3, Cldn4, and Cldn7/Claudin 7 with intestinal SMAD4 loss in vivo without changes in Claudin protein localization. TGFβ1/BMP2 treatment of polarized SMAD4+ colonoids increases TER. Cldn2, Cldn4, Cldn7, and Cldn8 are regulated by canonical TGFβ signaling, and TGFβ-dependent regulation of these genes is dependent on nascent RNA transcription (Cldn2, Cldn4, Cldn8) but not nascent protein translation (Cldn4, Cldn8). Human IBD/colon cancer specimens demonstrate decreased SMAD4, CLDN4, CLDN7, and CLDN8 and increased CLDN2 compared with healthy controls. Canonical TGFβ signaling modulates the expression of tight junction proteins and barrier function in mouse colon.NEW & NOTEWORTHY We demonstrate that canonical TGFβ family signaling modulates the expression of critical tight junction proteins in colon epithelial cells, and that expression of these tight junction proteins is associated with maintenance of colon epithelial barrier function in mice.

Gene Regulation Network Analysis on Human Prostate Orthografts Highlights a Potential Role for the JMJD6 Regulon in Clinical Prostate Cancer

Simple Summary

Prostate cancer is a very common malignancy worldwide. Treatment resistant prostate cancer poses a big challenge to clinicians and is the second most common cause of premature death in men with cancer. Gene expression analysis has been performed on clinical tumours but to date none of the gene expression-based biomarkers for prostate cancer have been successfully integrated to into clinical practice to improve patient management and treatment choice. We applied a novel laboratory prostate cancer model to mimic clinical hormone responsive and resistant prostate cancer and tested whether a network of genes similarly regulated by transcription factors (gene products that control the expression of target genes) are associated with patient outcome. We identified regulons (networks of genes similarly regulated) from our preclinical prostate cancer models and further evaluated the top ranked JMJD6 gene related regulated network in three independent clinical patient cohorts.

Abstract

Background: Prostate cancer (PCa) is the second most common tumour diagnosed in men. Tumoral heterogeneity in PCa creates a significant challenge to develop robust prognostic markers and novel targets for therapy. An analysis of gene regulatory networks (GRNs) in PCa may provide insight into progressive PCa. Herein, we exploited a graph-based enrichment score to integrate data from GRNs identified in preclinical prostate orthografts and differentially expressed genes in clinical resected PCa. We identified active regulons (transcriptional regulators and their targeted genes) associated with PCa recurrence following radical prostatectomy. Methods: The expression of known transcription factors and co-factors was analysed in a panel of prostate orthografts (n = 18). We searched for genes (as part of individual GRNs) predicted to be regulated by the highest number of transcriptional factors. Using differentially expressed gene analysis (on a per sample basis) coupled with gene graph enrichment analysis, we identified candidate genes and associated GRNs in PCa within the UTA cohort, with the most enriched regulon being JMJD6, which was further validated in two additional cohorts, namely EMC and ICGC cohorts. Cox regression analysis was performed to evaluate the association of the JMJD6 regulon activity with disease-free survival time in the three clinical cohorts as well as compared to three published prognostic gene signatures (TMCC11, BROMO-10 and HYPOXIA-28). Results: 1308 regulons were correlated to transcriptomic data from the three clinical prostatectomy cohorts. The JMJD6 regulon was identified as the top enriched regulon in the UTA cohort and again validated in the EMC cohort as the top-ranking regulon. In both UTA and EMC cohorts, the JMJD6 regulon was significantly associated with cancer recurrence. Active JMJD6 regulon also correlated with disease recurrence in the ICGC cohort. Furthermore, Kaplan–Meier analysis confirmed shorter time to recurrence in patients with active JMJD6 regulon for all three clinical cohorts (UTA, EMC and ICGC), which was not the case for three published prognostic gene signatures (TMCC11, BROMO-10 and HYPOXIA-28). In multivariate analysis, the JMJD6 regulon status significantly predicted disease recurrence in the UTA and EMC, but not ICGC datasets, while none of the three published signatures significantly prognosticate for cancer recurrence. Conclusions: We have characterised gene regulatory networks from preclinical prostate orthografts and applied transcriptomic data from three clinical cohorts to evaluate the prognostic potential of the JMJD6 regulon.

A modern era of personalized medicine in the diagnosis, prognosis, and treatment of prostate cancer

The present era is witnessing rapid advancements in the field of medical informatics and modern healthcare management. The role of translational bioinformatics (TBI), an infant discipline in the field of medical informatics, is pivotal in this revolution. The development of high-throughput technologies [e.g., microarrays, next-generation sequencing (NGS)] has propelled TBI to the next stage in this modern era of medical informatics. In this review, we assess the promising translational outcomes of microarray- and NGS-based discovery of genes, proteins, micro RNAs, and other active biological compounds aiding in the diagnosis, prognosis, and therapy of prostate cancer (PCa) to improve treatment strategies at the localized and/or metastatic stages in patients. Several promising candidate biomarkers in circulating blood (miR-25-3p and miR-18b-5p), urine (miR-95, miR-21, miR-19a, and miR-19b), and prostatic secretions (miR-203) have been identified. AURKA and MYCN, novel candidate biomarkers, were found to be specifically expressed in neuroendocrine PCa. The use of BTNL2 gene mutations and inflammasomes as biomarkers in immune function-mediated, inherited PCa has also been elucidated based on NGS data. Although TBI discoveries can benefit clinical performance metrics, the translational potential and the in vivo performance of TBI outcomes need to be verified. In conclusion, TBI aids in the effective clinical management of PCa; furthermore, the fate of personalized/precision medicine mostly relies on the enhanced diagnostic, prognostic, and therapeutic potential of TBI.

Prognostic Value and Potential Biological Functions of CLDN8 in Patients with Clear Cell Renal Cell Carcinoma

Purpose

Clear cell renal cell carcinoma (ccRCC) is among the most common malignant tumors worldwide, with a high incidence rate and poor prognosis. Currently, there are no biomarkers that can accurately guide prognostic evaluation and therapeutic strategy for ccRCC. The prognostic value and potential biological function of claudin-8 (CLDN8), a critical component of tight junctions in ccRCC, remain unclear.

Methods

Sequencing data were obtained from The Cancer Genome Atlas, International Cancer Genome Consortium, and Gene Expression Omnibus databases. R packages were used to explore CLDN8 mRNA expression levels and analyze differentially expressed genes. Results were validated in clinical specimens and cell lines, and bioinformatics analyses were conducted to explore the potential biological functions of CLDN8. Finally, functional analyses were carried out using 786–O ccRCC cell line.

Results

Both CLDN8 mRNA and protein expression levels were significantly lower in ccRCC compared with the normal control tissues. Kaplan–Meier analyses showed that low CLDN8 expression levels were associated with the poor overall survival, while univariate and multivariate Cox regression indicated that CLDN8 could serve as an independent prognostic factor in patient with ccRCC. Bioinformatic and Western blot analyses showed that CLDN8 suppressed proliferation, migration, and invasion of 786–O ccRCC cells through the epithelial–mesenchymal transition and AKT pathways.

Conclusion

CLDN8 could serve as an independent prognostic factor in ccRCC, in which it suppresses 786–O proliferation, migration, and invasion through EMT and AKT pathways.

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.

CLDN6-mediates SB431542 action through MMPs to regulate the invasion, migration, and EMT of breast cancer cells

Our previous research confirmed the repression of SMADs signaling pathway inhibits the invasion, migration, and EMT in breast cancer MCF-7 and SKBR-3 cell lines by DNMT1 up-regulating CLDN6, but the mechanism is unclear. Western blot was performed to detect the expression of SMAD2, SMAD3, P-SMAD2, and P-SMAD3. Then RT-PCR was carried out to examine the expression of tight junctions and cell adhesion molecule E-cadherin. According to the gene sequence of Claudin6, shRNA was linked with the green fluorescent protein-expressing eukaryotic expression vector pGC silencer TMΜ6/Neo/GFP, and it was transfected into breast cancer MCF-7 cells and SKBR-3 cells. RT-PCR and western blot were applied to verify the Claudin6 gene-silencing effect. We observed cellular morphology with inverted microscope, analyzed the capacity for clone formation, and detected transepithelial electrical resistance. The level of MMP2, and MMP9 in the cells treated with or without SB431542 and MCF-7-shGFP, MCF-7-shClaudin-6, SKBR-3-shGFP, and SKBR-3-shClaudin-6 cells pretreated with SB431542 were examined by RT-PCR and western blot. The expressions of Claudin-6, occludin, and cell adhesion molecule E-cadherin were enhanced by SB431542. SB431542 transformed mesenchymal cell morphology into epithelial cell morphology, inhibited capacity for clone formation, increased transepithelial electrical resistance, and downregulated the expression of MMP2 and MMP9. Knock down of Claudin6 can abolish SB431542 effects. We conclude that Claudin6 mediates the effects of SB431542 on the biologic phenotypes of the breast cancer cells we studied. We speculate Claudin6-mediated the SB431542 inhibition of invasion, migration, and EMT in breast cancer cells via MMP2/9.

The Expression and Prognostic Significance of Claudin-8 and Androgen Receptor in Breast Cancer

Purpose

Claudin-8 (CLDN8) has been identified as an androgen-regulated gene in prostate cancer. However, the role of CLDN8 has not been fully explored in breast cancer. We aimed to explore the expression of CLDN8 and androgen receptor (AR), determine the correlation between CLDN8 and AR, assess the prognostic value of CLDN8 and AR co-expression, and investigate the possible CLDN8 expression molecular mechanism in breast cancer.

Materials and Methods

Twenty-eight pairs of fresh tumor tissues and adjacent noncancerous tissues were evaluated by Western blot for CLDN8. Then, 142 breast cancer samples were determined by immunohistochemistry for CLDN8 and AR. The association of clinicopathological features with CLDN8, AR and CLDN8, and AR co-expression was examined. The Cancer Genome Atlas (TCGA) was used to demonstrate the expression of CLDN8 and correlation between CLDN8 and AR. Kaplan–Meier survival analysis was performed to assess the prognostic impact of CLDN8 and AR co-expression. The mechanisms related to CLDN8 expression in breast cancer were explored by Gene Set Enrichment Analysis (GSEA).

Results

CLDN8 was downregulated in breast cancer tissues and positively correlated with none lymph node metastasis (P=0.016), low histological grade (P=0.006), positive ER (P=0.014), positive PR (P=0.003), low Ki-67 index (P=0.017) and molecular subtypes (P=0.012). CLDN8 level was significantly associated with AR level (r=0.348; P<0.001). CLDN8 and AR co-expression was positively correlated with none lymph node metastasis (P=0.007), low histological grade (P=0.017), positive ER (P=0.019), positive PR (P=0.015) and low Ki-67 index group (P=0.038). CLDN8 and AR co-expression had a better clinical prognosis.

Conclusion

The expression of CLDN8 is directly related to the expression of AR. CLDN8 and AR co-expression might be a potential prognostic evaluation factor for breast cancer patients.

Differential Expression and Function of Bicellular Tight Junctions in Skin and Oral Wound Healing

Bicellular tight junctions are multiprotein complexes that are required for maintenance of barrier function and fence function in epithelial tissues. Wound healing in the oral cavity leads to minimal scar formation compared to the skin, and the precise mechanisms for this regenerative response remain to be elucidated. We hypothesized that oral and skin tissues express a different tight junction repertoire both at baseline and during the wound healing response, and that these molecules may be critical to the differential repair between the two tissues. We re-analyzed a mouse skin and palate epithelium microarray dataset to identify the tight junction repertoire of these tissue types. We then re-analyzed a skin and tongue wound healing microarray dataset to see how expression levels of tight junction genes change over time in response to injury. We performed in vitro scratch assays on human oral and skin keratinocyte cell lines to assay for tight junction expression over time, tight junction expression in response to lipopolysaccharide and histamine treatment, and the effects of siRNA knockdown of claudin 1 or occludin on migration and proliferation. Our data showed that oral and skin epithelium expressed different tight junction genes at baseline and during the wound healing response. Knockdown of claudin 1 or occludin led to changes in proliferation and migration in human skin keratinocytes but not oral keratinocytes. Furthermore, we also showed that skin keratinocytes were more permeable than oral keratinocytes upon histamine treatment. In conclusion, this study highlights a specific subset of functional tight junction genes that are differentially expressed between the oral and skin tissues, which may contribute to the mechanisms leading to distinct healing phenotypes in response to injury in the two tissues.

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.

Claudins: New Players in Human Fertility and Reproductive System Cancers

Claudins are major integral proteins of tight junctions (TJs), the apical cell-cell adhesions that enable maintaining polarity of epithelial cells, their differentiation, and cell signaling. A number of studies have indicated that claudins might play a crucial role in both physiology and pathogenesis. Their tissue-specific expression was originally linked to the development of different types of cancer and triggered a hope to use them as diagnostic or prognostic markers. However, it seems that their expression is more complex than that, and undoubtedly, claudins participate in one of the most important molecular events in cells. This review summarizes the recent research evaluating the role of claudins in fertility and the most common endocrine-dependent cancers in the reproductive system and highlights the crucial role of claudins both in human fertility and the most common cancers.

The detection and analysis of differential regulatory communities in lung cancer

The tumorgenesis process of lung cancer involves the regulatory dysfunctions of multiple pathways. Although many signaling pathways have been identified to be associated with lung cancer, there are little quantitative models of how inactions between genes change during the process from normal to cancer. These changes belong to different dynamic co-expressions patterns. We quantitatively analyzed differential co-expression of gene pairs in four datasets. Each dataset included a large number of lung cancer and normal samples. By overlapping their results, we got 14 highly confident gene pairs with consistent co-expression change patterns. Some of they, such as ARHGAP30 and GIMAP4, had been recorded in STRING network database while some of them were novel discoveries, such as C9orf135 and MORN5, TEKT1 and TSPAN1 were positively correlated in both normal and cancer but more correlated in normal than cancer. These gene pairs revealed the underlying mechanisms of lung cancer occurrence.

MiR-361-5p inhibits cell proliferation and induces cell apoptosis in retinoblastoma by negatively regulating CLDN8

PURPOSE

MiR-361-5p has been reported to act as tumor suppressor in several types of cancers. Retinoblastoma (RB) is the most common ocular tumor in childhood. The current study aimed to investigate the expression pattern and biological function of miR-361-5p in RB.

METHODS

Quantitative real time was utilized to determine and compare the expression of miR-361-5p in RB cells and normal retinal pigment epithelial cell line ARPE-19. CCK-8 and Edu assay were performed to assess cell proliferation. Cell apoptosis was evaluated using flow cytometry assay. Bioinformatics databases and luciferase reporter assay were applied to predict and confirm the target gene of miR-361-5p in RB cells.

RESULTS

Here, we found miR-361-5p was significantly downregulated in RB cells compared with normal retinal pigment epithelial cell line ARPE-19. MiR-361-5p overexpression significantly inhibited or silencing promoted cell proliferation in Y79 and SO-RB50 cells, respectively. Flow cytometry assay showed a significantly decreased cell apoptosis in miR-361-5p silencing Y79 cells and increased cell apoptosis in miR-361-5p overexpressing SO-RB50 cells. Moreover, miR-361-5p directly bound to the 3' untranslated region of claudin 8 (CLDN8) and inhibited the expression of CLDN8. Furthermore, we found knockdown of CLDN8 photocopied the effect of miR-361-5p on cell proliferation and apoptosis in RB cells.

CONCLUSION

These results indicated that overexpression of miR-361-5p might act as a suppressor in RB by targeting CLDN8 to inhibit the cellular function.

Claudin-18 expression in oesophagogastric adenocarcinomas: a tissue microarray study of 523 molecularly profiled cases

BACKGROUND

Claudin-18 (CLDN18) is a highly specific tight junction protein of the gastric mucosa. An isoform of CLDN18, the Claudin 18.2, has recently emerged as an innovative drug target for metastatic gastric cancer.

METHODS

We investigated the immunohistochemical profile of CLDN18, p53, p16, E-cadherin, MSH2, MSH6, MLH1, PSM2, HER2, and PDL-1 in a large series of 523 primary gastric carcinomas (GCs; n = 408) and gastro-oesophageal carcinomas (GECs; n = 115) and 135 matched and synchronous nodal metastases. The status of HER2 and EBER by means of chromogenic in situ hybridisation (CISH) was also evaluated.

RESULTS

High membranous CLDN18 expression was present in 150/510 (29.4%) primary cases and in 45/132 (34.1%) metastases. An abnormal expression (i.e. nuclear and/or cytoplasmic) was observed in 115 (22.5%) primary cases and in 33 (25.0%) metastases. A 38.8% of the cases showed significant CLDN18 intratumoural variability among the different tissue microarray cores obtained from the same tumour. Positive membrane CLDN18 expression was statistically associated with non-antral GCs (p = 0.016), Lauren diffuse type (p = 0.009), and with EBV-associated cancers (p < 0.001).

CONCLUSIONS

CLDN18 is frequently expressed in gastric and gastro-oesophageal cancers; further studies should investigate the prognostic significance of CLDN18 heterogeneity in order to implement its test into clinical practice.

Claudin Family Participates in the Pathogenesis of Inflammatory Bowel Diseases and Colitis-Associated Colorectal Cancer

Claudins are a multigene transmembrane protein family comprising at least 27 members. In gastrointestinal tract, claudins are mainly located in the intestinal epithelia; many types of claudins form a network of strands in tight junction plaques within the intercellular space of neighboring epithelial cells and build paracellular selective channels, while others act as signaling proteins and mediates cell behaviors. Claudin dysfunction may contribute to epithelial permeation disorder and multiple intestinal diseases. Over recent years, the importance of claudins in the pathogenesis of inflammatory bowel diseases (IBD) has gained focus and is being investigated. This review analyzes the expression pattern and regulatory mechanism of claudins based on existing evidence and elucidates the fact that claudin dysregulation correlates with increased intestinal permeability, sustained activation of inflammation, epithelial-to-mesenchymal transition (EMT), and tumor progression in IBD as well as consequent colitis-associated colorectal cancer (CAC), possibly shedding new light on further etiologic research and clinical treatments.

CLDN8 promotes colorectal cancer cell proliferation, migration, and invasion by activating MAPK/ERK signaling

Background

Claudin 8 (CLDN8), an integral membrane protein that constitutes tight junctions in cell membranes, was recently implicated in tumor progression. However, its roles in colorectal cancer (CRC) progression and metastasis remain unknown.

Methods

In this study, we examined the effect of CLDN8 on the progression of CRC, including cell proliferation, migration, and invasion, and determines its underlying molecular mechanism using in vitro CRC cell lines and in vivo mouse xenograft models.

Results

We found that CLDN8 expression in human CRC tissues was significantly higher than that in adjacent normal tissues. The knockdown of CLDN8 markedly suppressed the proliferation, migration, and invasion of SW480 and HT-29 CRC cells, whereas the overexpression of CLDN8 notably promoted tumor progression in SW480 and HT-29 CRC cells. Mechanistic studies revealed that CLDN8 upregulated p-ERK (p-PKB/AKT) and MMP9 in CRC cells. Notably, the MAPK/ERK inhibitor PD98095 dramatically attenuated the effects of CLDN8 on p-ERK and MMP9. Moreover, PD98095 remarkably blocked the tumor-promoting activity of CLDN8. The knockdown of CLDN8 also inhibited the in vivo tumor growth in a nude mouse xenograft model. Collectively, CLDN8 promoted CRC cell proliferation, migration, and invasion, at least in part, by activating the MAPK/ERK signaling pathway.

Conclusion

These findings suggest that CLDN8 exhibits an oncogenic effect in human CRC progression.

The effects of flutamide on cell-cell junctions in the testis, epididymis, and prostate

In this review, we summarize recent findings on the effect of the anti-androgen flutamide on cell-cell junctions in the male reproductive system. We outline developmental aspects of flutamide action on the testis, epididymis, and prostate, and describe changes in junction protein expression and organization of junctional complexes in the adult boar following prenatal and postnatal exposure. We also discuss findings on the mechanisms by which flutamide induces alterations in cell-cell junctions in reproductive tissues of adult males, with special emphasis on cytoplasmic effects. Based on the results from in vivo and in vitro studies in the rat, we propose that flutamide affects the expression of junction proteins and junction complex structure not only by inhibiting androgen receptor activity, but equally important by modulating protein kinase-dependent signaling in testicular cells. Additionally, results from studies on prostate cancer cell lines point to a role for the cellular molecular outfit in response to flutamide.

Delineation of the androgen-regulated signaling pathways in prostate cancer facilitates the development of novel therapeutic approaches

Although androgen deprivation therapy (ADT) is initially effective for the treatment of progressive prostate cancer, it inevitably fails due to the onset of diverse resistance mechanisms that restore androgen receptor (AR) signaling. Thus, AR remains a desired therapeutic target even in the relapsed stages of the disease. Given the difficulties in stopping all AR reactivation mechanisms, we propose that the identification of the driver signaling events downstream of the receptor offer viable, alternative therapeutic targets. Here, we summarize recently described, AR-regulated processes that have been demonstrated to promote prostate cancer. By highlighting these signaling events and describing some of the ongoing efforts to pharmacologically modulate these pathways, our goal is to advocate potential new therapeutic targets that would represent an alternative approach for blocking AR actions.

Expression profiles analysis identifies a novel three-mRNA signature to predict overall survival in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) remains to be a challenging public health problem worldwide. However, the underlying molecular mechanism regulating the carcinogenesis of OSCC is poorly known. Gene expression profiles of GSE13601, GSE30784, GSE37991 and The Cancer Genome Atlas (TCGA) head and neck cancer were downloaded from gene expression omnibus (GEO) and TCGA database respectively. R software and bioconductor packages were used to compare and identify the differentially expressed genes (DEGs) between OSCC tissues and normal controls. The common DEGs were then subjected to gene ontology (GO) enrichment analysis, ingenuity pathway analysis (IPA), protein-protein interaction (PPI) network analysis as well as survival analysis. A total of 76 up- and 102 down-regulated DEGs were identified. Functional analysis revealed that these DEGs were associates with increased oncostatin M signaling, cell diapedesis and extravasation as well as reduced calcium signaling and loss of adherens junctions and tight junctions. A set of robust prognostic signatures including PLAU, CLDN8 and CDKN2A were identified from DEGs and could predict overall survival in OSCC patients from TCGA cohort. This three-gene signature was further successfully validated as a prognostic marker for overall survival prediction in another independent cohort GSE41613. In conclusion, our study has identified a registry of novel genes and pathways that play important roles in regulating the initiation and development of OSCC. A set of robust molecular signature is identified for prognostic prediction, which will provide useful guidance for therapeutic applications.

CLDN8, an androgen-regulated gene, promotes prostate cancer cell proliferation and migration

The proliferation of prostate cancer cells is controlled by the androgen receptor (AR) signaling pathway. However, the function of AR target genes has not been fully elucidated. In previous studies, we have identified global AR binding sites and AR target genes in prostate cancer cells. Here, we focused on Claudin 8 (CLDN8), a protein constituting tight junctions in cell membranes. We found one AR binding site in the promoter region and two functional androgen‐responsive elements in the sequence. Reporter assay revealed that transcriptional activation of the CLDN8 promoter by androgen is dependent on these androgen‐responsive elements. Furthermore, CLDN8 mRNA is induced by androgen time‐dependently and the induction is blocked by AR inhibitor, suggesting that AR is involved in the transcriptional activation. In addition, our functional analyses by overexpression and knockdown of CLDN8 mRNA indicate that CLDN8 promotes prostate cancer cell proliferation and migration. Claudin 8 was overexpressed in prostate cancer clinical samples compared to benign tissues. Furthermore, we found that CLDN8 regulates intracellular signal transduction and stabilizes the cytoskeleton. Taken together, these results indicate that CLDN8 functions as an AR downstream signal to facilitate the progression of prostate cancer. Claudin 8 may be a novel molecular target for prostate cancer therapy.