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Tight junction (TJ) formation is vital for epidermal barrier function. We aimed to specifically manipulate TJ barriers in the reconstructed human epidermis (RHE) by claudin-1 and -4 knockdown (KD) and by claudin-binding fusion proteins of glutathione S-transferase and modified C-terminal fragments of Clostridium perfringens enterotoxin (GST-cCPE). Impedance spectroscopy and tracer permeability imaging were employed for functional barrier assessment and investigation of claudin contribution. KD of claudin-1, but not claudin-4, impaired the paracellular barrier in vitro. Similarly, claudin-binding GST-cCPE variants weakened the paracellular but not the stratum corneum barrier. Combining both TJ targeting methods, we found that claudin-1 targeting by GST-cCPE after claudin-4 KD led to a marked decrease in paracellular barrier properties. Conversely, after claudin-1 KD, GST-cCPE did not further impair the barrier. Comparison of GST-cCPE variants with different claudin-1/claudin-4 affinities, NHS-fluorescein tracer detection, and immunostaining of RHE paraffin sections showed that GST-cCPE variants bind to extrajunctional claudin-1 and -4, which are differentially distributed along the stratum basale-stratum granulosum axis. GST-cCPE binding blocks these claudins, thereby specifically opening the paracellular barrier of RHE. The data indicate a critical role for claudin-1 in regulating paracellular permeability for ions and small molecules in the viable epidermis. Claudin targeting is presented as a proof-of-concept for precise barrier modulation.

Objectives To investigate the effects of radiation on paracellular pathway of rat submandibular glands (SMGs) and the mechanism of increasing secretion following treatment with pilocarpine. Materials and methods In situ irradiation models of SMGs in Wistar rats were conducted, and the glands were exposed to X-radiation at a single dose of 20 Gy. Pilocarpine was intraperitoneally injected 60 min prior to radiation and continuous 6 days postirradiation for a total of 7 days. Salivary secretion, histological changes, pro-inflammatory cytokines, alterations in tight junctions (TJs), and functional membrane proteins aquaporin-5 (AQP5) and claudin-4 mediated by the muscarinic acetylcholine M3 subtype receptor were determined at 1 and 12 weeks after irradiation. Results Salivary secretion of the irradiated glands was reduced at 1 and 12 weeks. As well, acinar cell numbers, TJ width, and the levels of M3 receptor and AQP5 were decreased. In contrast, tumor necrosis factor-α, interleukin 6, interleukin 1α, and the expression of the TJ protein claudin-4 were significantly increased in irradiated SMGs. Notably, all the alterations were attenuated by pilocarpine treatment. Conclusions Pilocarpine could improve the secretory function of irradiated rat SMGs via reducing inflammation, ameliorating the structural injury of TJs, and attenuating the up-regulation of claudin-4 expression.

Clostridium perfringens enterotoxin (CPE) can be used to eliminate carcinoma cells that overexpress on their cell surface CPE receptors – a subset of claudins (e.g., Cldn3 and Cldn4). However, CPE cannot target tumors expressing solely CPE‐insensitive claudins (such as Cldn1 and Cldn5). To overcome this limitation, structure‐guided modifications were used to generate CPE variants that can strongly bind to Cldn1, Cldn2 and/or Cldn5, while maintaining the ability to bind Cldn3 and Cldn4. This enabled (a) targeting of the most frequent endocrine malignancy, namely, Cldn1‐overexpressing thyroid cancer, and (b) improved targeting of the most common cancer type worldwide, non‐small‐cell lung cancer (NSCLC), which is characterized by high expression of several claudins, including Cldn1 and Cldn5. Different CPE variants, including the novel mutant CPE‐Mut3 (S231R/S313H), were applied on thyroid cancer (K1 cells) and NSCLC (PC‐9 cells) models. In vitro, CPE‐Mut3, but not CPEwt, showed Cldn1‐dependent binding and cytotoxicity toward K1 cells. For PC‐9 cells, CPE‐Mut3 improved claudin‐dependent cytotoxic targeting, when compared to CPEwt. In vivo, intratumoral injection of CPE‐Mut3 in xenograft models bearing K1 or PC‐9 tumors induced necrosis and reduced the growth of both tumor types. Thus, directed modification of CPE enables eradication of tumor entities that cannot be targeted by CPEwt, for instance, Cldn1‐overexpressing thyroid cancer by using the novel CPE‐Mut3., Clostridium perfringens enterotoxin (CPE) is used to target carcinomas overexpressing a claudin subset serving as CPE receptors. CPE‐based pores in membrane cause cell death. Structure‐guided CPE modifications (CPE‐S231R/S313H) enabled also claudin‐1 binding and growth reduction of claudin‐1‐expressing papillary thyroid carcinoma (mouse xenotransplants) that could not be targeted by CPEwt. Furthermore, CPE‐S231R/S313H improved targeting of lung cancer (NSCLC) expressing multiple claudins.

The functional state (FS) of adult pancreatic islets is regulated by a large array of regulatory molecules including numerous transcription factors. Whether any islet structural molecules play such a role has not been well understood. Here, multiple technologies including bioinformatics analyses were used to explore such molecules. The tight junction family molecule claudin 4 (Cldn4) was the highest enriched amongst over 140 structural genes analysed. Cldn4 expression was ~75‐fold higher in adult islets than in exocrine tissues and was mostly up‐regulated during functional maturation of developing islet cells. Cldn4 was progressively down‐regulated in functionally compromised, dedifferentiating insulin‐secreting β cells and in db/db type 2 diabetic islets. Furthermore, the genetic deletion of Cldn4 impaired significantly the FS without apparently affecting pancreas morphology, islet architectural structure and cellular distribution, and secretion of enteroendocrine hormones. Thus, we suggest a previously unidentified role for Cldn4 in regulating the FS of islets, with implications in translational research for better diabetes therapies., Claudin 4 (Cldn4) is developmentally up‐regulated in developing pancreatic islet cells, is involved in sustaining the functional state (FS) in mature islets and is pathologically down‐regulated to compromise the FS in diabetic β cells.

BACKGROUND Oral lichen planus (OLP) is a chronic T-cell-mediated inflammatory disease, which is associated with increased risk of developing oral squamous cell carcinoma. Epithelial-to-mesenchymal transition is a physiological phenomenon occurring during growth and organogenesis, but it has also an important role in tumorigenesis. In the present work, we studied the expression of known epithelial-to-mesenchymal transition markers in oral lichen planus. METHODS In total, 54 oral lichen planus and 22 control samples were analyzed for epithelial-to-mesenchymal transition markers. Samples were immunohistochemically stained for claudin-1, claudin-4 and claudin-7, cadherin-1 (E-cadherin), Twist-related protein 1 (TWIST1) and zinc finger E-box-binding homeobox 1 (ZEB1). RESULTS The expression of claudin-1, claudin-4 and E-cadherin was significantly weaker in oral lichen planus epithelium compared to controls (P

Piglets must acquire passive immunity through colostrum within hours after birth to survive. How colostral macromolecules traverse the small intestinal epithelium may include nonselective pinocytosis and paracellular transport through tight junction proteins located between epithelial cells. Claudin proteins‐3 and ‐4 contribute to the epithelial tight junctions (TJs) on the apical aspect of lateral surfaces of intestinal epithelial cells (IECs) where they help regulate ion and macromolecule movement across the intestinal epithelium. Throughout the small intestine of newborn piglets, Claudin‐3 was localized to the lateral and basolateral surface of intestinal epithelial cells as well as the membrane of large vacuoles. In the duodenum and jejunum, Claudin‐4 was localized to the apical surface independent of tight junction regions. In the ileum, Claudin‐4 was localized to the lateral and basolateral surfaces indicating region‐specific differences and noncanonical patterns of Claudin‐4 localization independent of tight junction regions. Understanding the timing of changes in surface localization of Claudin‐3 and Claudin‐4 and how they may coincide with changes in small intestinal permeability may help develop new protective strategies against infectious diseases within newborn piglets., The newborn piglet small intestine epithelial cells do not exclusively express Claudin‐3 and Claudin‐4 at the tight junction region which may lead to leaky gut.

Background Odontogenic sinusitis (OS) presents more satisfactory therapeutic effect after endoscopic surgery compared with chronic rhinosinusitis (CRS) of other origin. The aim of the present study was to investigate the clinical characteristics, morphological features, and epithelial barrier function of sinus mucosa of OS and discuss the possible relationship with good prognosis. Methods A total of 25 subjects with OS, 7 CRS without nasal polyps (CRSsNP), 10 CRS with nasal polyps (CRSwNP), and 9 control subjects were recruited. The biopsy specimens were stained with hematoxylin and eosin for general observation of cytomorphologic features. Epithelial tight junctions (TJs) protein claudin-4 expression was determined to evaluate the epithelial barrier integrity by using immunofluorescence and Image-Pro Plus software analysis. The representative cytokine profiles regarding T helper 1 (Th1) (interferon [IFN]-γ), Th2 (interleukin [IL]-5), and Th17 (IL-17) were examined by reverse transcription-polymerase chain reaction (RT-PCR). Results Extensively small papillary protrusions could be seen in the maxillary sinus mucosa of OS patients under nasal endoscopy, similar to the morphological behavior, which also presented as papillary folds in the surface of the epithelium. The epithelium in OS kept an increased claudin-4 expression compared with that seen in CRSsNP, CRSwNP, and control subjects. The inflammatory pattern analysis demonstrated that OS belonged to the lymphocyte and plasma cell-dominant cellular phenotypes, whereas IL-17 was dominant compared with IFN-γ as well as IL-5. Conclusion The odontogenic infections might induce the formation of papillary mucosa folds and enhance the epithelial TJ barrier function. OS exhibited as lymphocyte and plasma cell-dominant cellular phenotypes and Th17 cytokine profiles.

The airway epithelium plays a crucial role in the pathogenesis of asthma. The functions of leukotriene B4 receptor 2 (BLT2) on the airway epithelial cells remains unknown. In our study, BLT2 expression in 16HBE bronchial epithelial cells were manipulated by transfection with BLT2 overexpression plasmid or BLT2 small interference RNA. 16HBE cells were then exposed to BLT2 antagonist (LY255283) or BLT2 agonist (12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid [12-HHT] or CAY10583). The results showed that BLT2 overexpression, 12-HHT stimulation, or CAY10583 treatment resulted in the enhanced proliferation and migration of 16HBE cells. In addition, BLT2 showed an inhibitory effect on epithelial permeability as illustrated by the measurement of transepithelial electrical resistance (TER) and epithelial permeability, and a promoting effect on the levels of tight junction proteins (occludin and claudin-4) and phosphorylated p38 as demonstrated by real-time PCR and Western blotting analyses. These results suggest BLT2 as a key determinant of airway epithelial barrier integrity. On the contrary, RNAi-mediated knockdown or LY255283 treatment had reversed effects on the proliferation, migration, and epithelial barrier integrity. Together, our findings suggest the critical roles of BLT2 on the functions of bronchial epithelial cells and that BLT2 agonists are potential therapeutic agents for asthma treatment.

Background and objective The discovery of highly accurate pleural fluid (PF) biomarkers of malignancy remains elusive. We assessed the operating characteristics of the PF epithelial cell adhesion molecule (EpCAM), claudin 4 (CL4) and human epididymis protein 4 (HE4) as potential markers of epithelial malignancies. Methods The three markers were quantified by immunoassays in the supernatants (s) and cell lysates (cl) of 175 PF samples. The cut-off values with 100% specificity were selected for malignant-benign discrimination. An immunocytochemical staining index score for each marker was also evaluated on PF cell blocks. The resulting best biomarker was further validated in two independent populations of 73 and 48 patients with pleural effusions (PE). Results An EpCAM(cl) >98 pg/g total lysate protein yielded 75% sensitivity, 100% specificity, negative likelihood ratio of 0.25 and area under the curve of 0.94 for labelling adenocarcinomatous effusions. Sensitivity reached 88% if EpCAM(cl) was combined with EpCAM immunostaining. One-third or more of the malignant effusions exhibiting a false-negative cytological fluid examination were correctly classified by EpCAM(cl) concentrations. Immunoassays for CL4 and HE4 were diagnostically useless. Conclusion EpCAM(cl) is a new biomarker of adenocarcinomatous PE with meaningful discriminating properties.

GPCRs are involved in numerous physiologic functions and are important drug targets. Although the epithelial barrier is important for protection from invading pathogens, the correlation between GPCRs and epithelial barrier function remains unknown. Leukotriene B4 (LTB4) receptor type 2 (BLT2), mainly expressed in epithelial cells, is a GPCR for 12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) and LTB4. In our study, BLT2 localized at the lateral membrane in BLT2-overexpressing Madin-Darby canine kidney (MDCK) II cells and in the small intestine of BLT2-transgenic mice. BLT2-deficient mice exhibited higher transepidermal water loss and were more sensitive to epicutaneous sensitization. MDCK-BLT2 cells recovered transepithelial electrical resistance (TER) after a calcium switch faster than did MDCK-Mock cells, and 12-HHT stimulation accelerated TER recovery only in MDCK-BLT2 cells. Quantitative PCR and immunoblot analyses revealed that the 12-HHT/BLT2 axis up-regulated claudin-4 (CLDN4) expression in MDCK-BLT2 cells and human primary keratinocytes, and CLDN4 knockdown abolished 12-HHT-dependent TER recovery. Acceleration of TER recovery and induction of CLDN4 expression by 12-HHT stimulation were abolished by inhibition of Gαi protein or p38 MAPK. These results show that 12-HHT/BLT2 enhances epithelial barrier function by increasing CLDN4 expression via the Gαi protein-p38 MAPK pathway.

Background Claudins are transmembrane proteins of tight junctions emerging as targets for diagnosis, prediction of prognosis, disease recurrence, and metastasis. Our goal was to evaluate expression of claudin-4 in the most common benign and malignant salivary gland neoplasms. Methods Claudin-4 gene levels and protein expression were determined by real-time polymerase chain reaction (PCR), and immunohistochemistry in a total of 30 specimens containing normal salivary tissue, pleomorphic adenoma, Warthin's tumor, mucoepidermoid carcinoma, and adenoid cystic carcinoma. Results We identified down-regulation of claudin-4 gene levels and protein expression from normal control to benign salivary gland neoplasms and reached their lowest values in the malignant salivary gland neoplasms. Conclusions Low claudin-4 expression could be considered as a sign of increasing cellular disorientation and invasion of salivary gland tumors.

Mutations in the ATP2C1 gene encoding Ca(2+) /Mn(2+) ATPase SPCA1 cause Hailey-Hailey disease (HHD, OMIM 16960). HHD is characterized by epidermal acantholysis. We attempted to model HHD using normal keratinocytes, in which the SPCA1 mRNA was down-regulated with the small inhibitory RNA (siRNA) method. SiRNA inhibition significantly down-regulated the SPCA1 mRNA, as demonstrated by qPCR, and decreased the SPCA1 protein beyond detectable level, as shown by Western analysis. The expression of selected desmosomal, adherens and tight junction (TJ) proteins was then studied in the SPCA1-deficient and control keratinocytes cultured in low (0.06 mm) or high (1.2 mm) calcium concentration. The mRNA and protein levels of most TJ components were up-regulated in non-treated control keratinocyte cultures upon switch from low to high calcium concentration. In contrast, SPCA1-deficient keratinocytes displayed high levels of TJ proteins claudins 1 and 4 even in low calcium. ZO-1 did not, however, follow similar expression patterns. Protein levels of occludin, beta-catenin, E-cadherin, desmoplakin, desmogleins 1-3, desmocollin 2/desmocollin 3 and plakoglobin did not show marked changes in SPCA1-deficient keratinocytes. Indirect immunofluorescence labelling revealed delayed translocation of desmoplakin and desmoglein 3 in desmosomes and increased intracellular pools of TJ and desmosomal components in SPCA1-inhibited keratinocytes. The results show that SPCA1 regulates the levels of claudins 1 and 4, but does not affect desmosomal protein levels, indicating that TJ proteins are differently regulated. The results also suggest a potential role for claudins in HHD.

Terminal progression of colorectal cancer (CRC) culminates in liver metastasis. To identify genes that are involved in the metastatic phenotype, cDNA microarrays were used to analyse mRNA expression profiles of colorectal carcinoma (CC)531 rat colon adenocarcinoma cells for changes related to their homing into the liver. Briefly, CC531 cells were intraportally implanted into the liver of Wag-Rij rats and re-isolated after 3, 6, 9, 14 and 21 days. Compared to control CC531 cells, claudin1 and claudin4 were among the ≥8-fold initially down-regulated genes. The co-culture of tumour cells with isolated rat hepatocytes and Kupffer cells did not induce down-regulation of either claudin1 or 4. When the environment effective on circulating tumour cells was simulated by cell culture conditions favouring their adhesion, only claudin4 showed augmented expression. Knockdown of claudin1 and claudin4 mediated by small interfering RNA caused significantly increased migration and decreased clonogenic growth of tumour cells (P < 0.05), but had no effect on their proliferation. These experimental results were paralleled by increased claudin1 and claudin4 expression in human CRC samples in Union for International Cancer Control (UICC) stages I–III, as evaluated by real-time PCR. Increased claudin4 levels were correlated with significantly reduced overall survival (log-rank test, P= 0.018). Further, significantly (P < 0.05) reduced expression of claudin1 and claudin4 was observed in stage IV and liver metastasis by immunohistochemistry. In conclusion, sequential biphasic changes in claudin1 and claudin4 expression occur during the homing of rat CC531 CRC cells to the liver. This modulation is reflected by significant changes in claudin expression in human primary and metastatic CRC.

Claudin-4 regulates ion permeability via a paracellular pathway in renal epithelial cells, but its other physiological functions have not been examined. We found that hyperosmotic stress increases claudin-4 expression in Madin-Darby canine kidney cells. Here, we examined whether claudin-4 affects cell motility, cell association, and the intracellular distribution of endogenous junctional proteins. Doxycycline-inducible expression of claudin-4 did not change endogenous levels of claudin-1, claudin-2, claudin-3, occludin, E-cadherin, and ZO-1. Claudin-4 overexpression increased cell association and decreased cell migration without affecting cell proliferation. Doxycycline did not change cell junctional protein levels, cell association or cell migration in mock-transfected cells. The insolubility of claudin-1 and -3 in Triton X-100 was increased by claudin-4 overexpression, but that of claudin-2, occludin, ZO-1, and E-cadherin was unchanged. Immunocytochemistry showed that claudin-4 overexpression increases the accumulation of claudin-1 and -3 in tight junctions (TJs). Furthermore, claudin-4 overexpression increased the association of claudin-4 with claudin-1 and -3. These results suggest that claudin-4 accumulates claudin-1 and -3 in TJs to enhance cell-cell contact in renal tubular epithelial cells.

The elevated expression of claudins (CLDN) and E-cadherin (CDH-1) was found to correlate with poor prognostic features. Our aim was to perform a comprehensive analysis to assess their potential to predict prognosis in breast cancer. The expression of CLDN-1, -3-5, -7, -8, -10, -15, -18, and E-cadherin at the mRNA level was evaluated in correlation with survival in datasets containing expression measurements of 1809 breast cancer patients. The breast cancer tissues of 197 patients were evaluated with tissue microarray technique and immunohistochemical method for CLDN-1-5, -7, and E-cadherin protein expression. An additional validation set of 387 patients was used to test the accuracy of the resulting prognostic score. Based on the bioinformatic screening of publicly-available datasets, the metagene of CLDN-3, -4, -7, and E-cadherin was shown to have the most powerful predictive power in the survival analyses. An immunohistochemical protein profile consisting of CLDN-2, -4, and E-cadherin was able to predict outcome in the most effective manner in the training set. Combining the overlapping members of the above two methods resulted in the claudin-4 and E-cadherin score (CURIO), which was able to accurately predict relapse-free survival in the validation cohort (P = 0.029). The multivariate analysis, including clinicopathological variables and the CURIO, showed that the latter kept its predictive power (P = 0.040). Furthermore, the CURIO was able to further refine prognosis, separating good versus poor prognosis subgroups in luminal A, luminal B, and triple-negative breast cancer intrinsic subtypes. In breast cancer, the CURIO provides additional prognostic information besides the routinely utilized diagnostic approaches and factors.

BACKGROUND:Thesmallintestinalepitheliumfunctionsbothtoabsorbnutrients,andtoprovideabarrierbetweentheoutside, luminal, world and the human body. One of the passageways across the intestinal epithelium is paracellular diffusion, which is controlled by the properties of tight junction complexes. We used a differentiated Caco-2 monolayer as a model for small intestinal epithelium to study the effect of crude apple extracts on paracellular permeability. RESULTS: Exposure of crude apple homogenate to the differentiated Caco-2 cells increased the paracellular resistance, determined as trans-epithelial electrical resistance (TEER). This increase was linearly related to the concentration of apple present. The TEER-enhancing effect of apple extract was due to factors mainly present in the cortex, and the induction was not inhibited by protein kinase inhibitors. Apple-induced resistance was accompanied by increased expression of several tight junction related genes, including claudin 4 (CLDN4). CONCLUSION: Crude apple extract induces a higher paracellular resistance in differentiated Caco-2 cells. Future research will determine whether these results can be extrapolated to human small intestinal epithelia. c � 2011 Society of Chemical Industry

The effect of diallyl disulfide (DADS), a major component of an oil-soluble allyl sulfide garlic (Allium sativum) derivative, on the correlation between anti-invasive activity and tightening of tight junctions (TJs) was investigated in human gastric adenocarcinoma AGS cells. Our data indicated that the inhibitory effects of DADS on cell motility and invasiveness were found to be associated with increased tightness of the TJs, which was demonstrated by an increase in transepithelial electrical resistance. Activities of matrix metalloprotease (MMP)-2 and -9 in AGS cells were dose-dependently inhibited by treatment with DADS, and this was also correlated with a decrease in expression of their mRNA and proteins; however, tissue inhibitor of metalloproteinase (TIMP)-1 and -2 mRNA levels and proteins were increased. Additionally, immunoblotting results indicated that DADS repressed the levels of claudin proteins (claudin-2, -3, and -4), major components of TJs that play key roles in control and selectivity of paracellular transport. Although further studies are needed, these results suggest that DADS treatment may inhibit tumor cell motility and invasion and, therefore, act as a dietary source to decrease the risk of cancer metastasis.

Hatakeyama S, Ishida K, Takeda Y. Changes in cell characteristics due to retinoic acid; specifically, a decrease in the expression of claudin-1 and increase in claudin-4 within tight junctions in stratified oral keratinocytes. J Periodont Res 2010; doi: 10.1111/j.1600-0765.2009.01219.x. © 2009 The Authors. Journal compilation © 2009 Blackwell Munksgaard Background and Objective: It has been reported that retinoic acid disintegrates the desmosome formation of squamous epithelium, resulting in inhibition of stratification. In contrast, it is not known whether retinoic acid influences the integration of tight junctions. Therefore, our objective of this study is to disclose effects of retinoic acid on the formation and maintenance of tight junction. Material and Methods: In the present study, the alteration of expression of tight junction constituent proteins and keratin peptides in immortalized oral mucosal epithelial cells (GE1) induced by 1 μm retinoic acid was analyzed by immunofluorescence, electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR). Results: The stratifying GE1 cells expressed claudin-1, claudin-4, claudin-5, occludin and zonula occludens 1 in the control culture. The RT-PCR showed that retinoic acid significantly reduced the expression of claudin-1 mRNA, whereas it dramatically enhanced expression of claudin-4 mRNA. Immunofluorescence showed that claudin-1 was present at cell-to-cell contact sites in the flattened uppermost layers of the control culture. In the culture with retinoic acid, the flattened uppermost cells were absent and there claudin-1 was less present, but claudin-4 was prominently present in all layers. Claudin-5 was present in a variety of patterns, regardless of the presence of retinoic acid. Along with the change of claudin species, the expressions of keratin 7, keratin 8 and keratin 18, as markers for the simple epithelium, were clearly stimulated by retinoic acid. Conclusion: Retinoic acid changed the expression of tight junction constituent molecules, such as claudin-1 and claudin-4, in oral keratinocytes. These findings suggest that long-term application of retinoids in clinical therapy should be carefully performed.

Claudin-4 (CLDN4) is a tetraspanin transmembrane protein of tight junction structure and is highly expressed in pancreatic and ovarian cancers. In this study, we aimed to generate an anti-Claudin-4 monoclonal antibody (mAb) and evaluate its antitumor efficacy in vitro and in vivo. To isolate specific mAb, we generated CLDN3, 4, 5, 6, and 9, expressing Chinese hamster ovary (CHO) cells, and then used them as positive and negative targets through cell-based screening. As a result, we succeeded in isolating KM3900 (IgG2a), which specifically bound to CLDN4, from BXSB mice immunized with pancreatic cancer cells. Immunoprecipitation and flow cytometry analysis revealed that KM3900 recognized the conformational structure and bound to extracellular loop 2 of CLDN4. Furthermore, binding of KM3900 was detected on CLDN4-expressing pancreatic and ovarian cancer cells, but not on negative cells. Next, we made the mouse-human chimeric IgG1 (KM3934) and evaluated its antitumor efficacy. KM3934 induced dose-dependent antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro, and significantly inhibited tumor growth in MCAS or CFPAC-1 xenograft SCID mice in vivo (P < 0.05). These results suggest that mAb therapy against CLDN4 is promising for pancreatic and ovarian cancers.

Background and Aims: Cancer invasion and metastasis are critical events for patient prognosis; however, the most important step in the whole process of lymph node (LN) metastasis in gastric cancer remains obscure. In this study, the significance of cancer cell behaviors, such as cell detachment, stromal invasion and lymphatic invasion on regional LN metastasis in gastric cancer was investigated by comprehensive immunohistochemistry. Methods: A total of 210 cases with gastric cancer were selected. These consisted of 105 cases with regional LN metastasis (LN[+] group) and 105 cases without LN metastasis (LN[–] group). Both groups exhibited the same depth of invasion. Cancer tissues were subjected to immunohistochemistry with antibodies against claudin-3, claudin-4, β-catenin, matrix metalloproteinase (MMP)-1, and MMP-2, as well as endothelial markers of lymphatic vessel endothelial hyaluronan receptor-1 and von Willebrand factor for the objective discrimination between lymphatics and blood vessels. The expression of each protein as well as the histopathological parameters were compared between LN(+) and LN(−) groups. Results: Along with lymphatic invasion by cancer cells and gross tumor size, MMP-1 expression in cancer cells at the invasive front of the primary tumor was a significant, independent predictor of LN metastasis. The expression of claudins and β-catenin was associated with the histopathological type of cancer, but not with LN status. Conclusion: Among the cancer invasion-related proteins examined, MMP-1 plays a vital role in LN metastasis of gastric cancer. Tumor size, lymphatic invasion and MMP-1 expression level at the invasive front were the predictive factors of LN metastasis of gastric cancer.

The role of intercellular tight junctions in breast epithelial cells is traditionally thought to be in maintaining polarity and barrier function. However, claudin-4, a tight junction protein, is overexpressed in breast tumour cells compared to normal epithelial cells, which generally corresponds to a loss in polarity. The aim of this study was to investigate the distribution and potential clinical value of claudin-4 in breast cancer, and to evaluate its usefulness as a prognostic and predictive biomarker. Expression of claudin-4 was initially examined by Western blot analysis in a cohort of 88 breast tumours, and was found to correlate positively with tumour grade and negatively with ER. Claudin-4 expression was then evaluated by immunohistochemistry in a larger cohort of 299 tumours represented on a tissue microarray. Claudin-4 expression correlated positively with tumour grade and Her2, and negatively with ER. High claudin-4 expression was also associated with worse breast cancer-specific survival (p = 0.003), recurrence-free survival (p = 0.025) and overall survival (p = 0.034). Multivariate analysis revealed that claudin-4 independently predicted survival in the entire cohort (HR 1.95; 95%CI 1.01-3.79; p = 0.047) and in the ER positive subgroup treated with adjuvant tamoxifen (HR 4.34; 95%CI 1.14-16.53; p = 0.032). This relationship between increased claudin-4 expression and adverse outcome was validated at the mRNA level in a DNA microarray dataset of 295 breast tumours. We conclude that high levels of claudin-4 protein are associated with adverse outcome in breast cancer patients, including the subgroup of patients treated with adjuvant tamoxifen.

According to the expression of gastric (claudin-18) and intestinal claudins (claudin-3 and claudin-4), the authors have previously proposed a new phenotypic classification of gastric carcinoma (GC): the gastric (G-CLDN), intestinal (I-CLDN) and unclassified claudin (U-CLDN) phenotypes. The aim of the present study was to examine the role of Cdx2, the caudal-related transcription factor, on the regulation of intestinal claudins expression in vitro and in vivo. It was confirmed on immunohistochemistry that non-neoplastic gastric mucosa with intestinal metaplasia (IM) expressed Cdx2 with increased levels of intestinal claudin expression. In addition, Cdx2 expression was detected in 28 (30%) of 94 GC at the invasive front. Interestingly, Cdx2 expression had a significant association with the I-CLDN phenotype (P < 0.001), which was almost identical to the established gastric and intestinal mucin-based GC classification. Furthermore, the transfection of a recombinant human CDX2-expressing vector into TMK-1 (Cdx2-negative) GC cells specifically elevated the expression of claudin-3 and claudin-4 at the mRNA (CLDN3, 3.9-fold; CLDN4, 2.8-fold) and protein levels (claudin-3, 8.6-fold; claudin-4, 9.8-fold), whereas no induction of the other claudins was detected. These findings suggest that Cdx2 plays an important role in the regulation of intestinal claudin expression not only in gastric mucosa with IM but also GC.

BACKGROUND. Early colorectal cancer (ECC) is curable by endoscopic local resection; however, 10% of patients with ECC exhibit lymph node (LN) metastasis. In the current study, accurate predictors for LN metastasis in patients with ECC were examined by using immunohistochemistry with the lymphatic endothelial hyaluronan receptor 1 (LYVE-1) antibody to discriminate between lymphatics and blood vessels. METHODS. Colorectal tissue specimens obtained from 71 patients with ECC, including 28 patients with regional LN metastasis, were immunostained with antibodies against LYVE-1, β-catenin, claudin-3, claudin-4, and cytokeratin. The significance of the histopathologic variables for LN metastasis in ECC was investigated on the basis of specific histopathologic parameters. RESULTS. Lymphatic invasion confirmed by LYVE-1 immunohistochemistry was observed mainly in the submucosal area around the primary tumor and rarely was observed in the tumor. Expression patterns of β-catenin, claudin-3, and claudin-4 in cancer cells at the invasive front were irrelevant to LN status. Tumor size, depth of invasion, histologic tumor type, budding formation, and lymphatic invasion were statistically significant to LN status in univariate analysis; however, only 2 factors—lymphatic invasion and budding formation at the invasive front—were independent predictors of LN metastasis in ECC. CONCLUSIONS. LYVE-1 immunohistochemistry appeared to be a useful method for detecting lymphatics invaded by cancer cells, and detailed examination of the submucosa around the tumor may be important for predicting LN metastasis. When lymphatic invasion and budding formation are observed histopathologically in patients with ECC, additional therapy, such as adjuvant chemotherapy or a curative resection of the regional LN, may be required. Cancer 2008. © 2008 American Cancer Society.

Tight junctions (TJs) create a paracellular permeability barrier to restrict the passage of ions, small solutes, and water. Ameloblasts are enamel-forming cells that sequentially differentiate into preameloblasts, secretory, transition, and ruffle-ended and smooth-ended maturation ameloblasts (RAs and SAs). TJs are located at the proximal and distal ends of ameloblasts. TJs at the distal ends of secretory ameloblasts and RAs are well-developed zonula occludens, but other TJs are moderately developed but incomplete zonula occludens (ZO) or less-developed macula occludens. We herein examined the immunofluorescence localization of TJ proteins, 10 claudin isoforms, occludin, ZO-1, and PAR3, a cell polarity-related protein, in ameloblasts of rat upper incisors. ZO-1 and claudin-1 were detected at both ends of all ameloblasts except for the distal ends of SAs. Claudin-4 and occludin were detected at both ends of transition and maturation ameloblasts except for the distal ends of SAs. PAR3 was detected at the proximal TJs of all ameloblasts and faintly at the distal TJs of early RAs. These results indicate that functional zonula occludens formed at the distal ends of the secretory ameloblasts and RAs consisted of different TJ proteins. Therefore, the distal TJs of secretory ameloblasts and RAs may differentially regulate the paracellular permeability to create a microenvironment suitable for enamel deposition and enamel maturation, respectively. In addition, PAR3 may be principally involved in the formation and maintenance of the proximal, but not distal, TJs.

p38 mitogen-activated protein kinases (MAPK) contribute to the loss of cell-cell contact and the round cell shape characteristic of poorly differentiated gastric cancer. In the present study it is demonstrated that phospho-p38 MAPK level significantly increased in poorly differentiated gastric cancers in comparison to differentiated cancers and normal gastric mucosa by immunohistochemistry. Next, the pathophysiological roles of p38 MAPK activation were investigated in differentiated gastric cancer cell lines MKN7 and MKN28 and poorly differentiated gastric cancer cell lines KATO-III and MKN45 cells by incubating with specific p38 inhibitor SB203580 or inactivating analog SB202474. The distribution of F-actin on phalloidin staining was identified as fine cytoskeletal filaments in MKN7 and MKN28, but as dense membranous accumulation in KATO-III and MKN45 cells. The treatment with SB203580 but not SB202474 reduced irregular accumulation of F-actin in KATO-III and MKN45 cells. The expression of E-cadherin, ZO-1, occludin and claudin 4 was higher in MKN7 and MKN28 than KATO-III and MKN45 cells. The expression of E-cadherin in KATO-III cells was increased following treatment with SB203580, suggesting the suppression of E-cadherin at the transcriptional level independent of its genetic alterations. Thus, p38 MAPK signaling might contribute to the acquisition of malignant properties in poorly differentiated phenotypes.

The aim of the study was to elucidate the significance of claudins in surgically treated esophageal carcinoma. The expression of claudins 1, 3, 4, 5 and 7 was studied by immunohistochemistry. Tumor proliferation was assessed with Ki67 immunostaining and apoptosis by the TUNEL method and immunostaining of fragmented caspase 3. Adenocarcinomas showed significantly more cases with moderate or strong claudin 3 (p

Recent research suggests that tight junctions (TJs) are located in the stratum granulosum, where they contribute to the barrier function of the epidermis. In this study, we investigated the formation of functional TJs in cultured normal human epidermal keratinocytes. We observed the development of permeability barrier function through the process of Ca(2+)-induced differentiation. Immunofluorescence analyses at 96 h after Ca(2+)-induced differentiation revealed concentrated portions of occludin, a TJ-specific marker, arranged as continuous lines circumscribing individual flattened suprabasal cells in areas with high concentrations of claudin-1 and -4. Transient Ca(2+) depletion reversibly disrupted the continuous network of TJ proteins and the permeability barrier. We also found that the addition of ochratoxin A weakened the permeability barrier and the expression of claudin-4. Our findings suggest that TJ proteins contribute to the permeability barrier in epidermal keratinocytes.

Tight junctions operate as semipermeable barriers in epithelial tissue, separating the apical from the basolateral sides of the cells. Membrane proteins of the claudin family represent the major tight junction constituents, and some reinforce permeability barriers, whereas others create pores based on solute size and ion selectivity. To outline paracellular permeability pathways in gustatory tissue, all claudins expressed in mouse taste buds and in human fungiform papillae have been characterized. Twelve claudins are expressed in murine taste-papillae-enriched tissue, and five of those are expressed in human fungiform papillae. A subset of the claudins expressed in mouse papillae is uniquely found in taste buds. By immunohistochemistry, claudin 4 has been found in mouse taste epithelium, with high abundance around the taste pore. Claudin 6 is explicitly detected inside the pore, claudin 7 was found at the basolateral side of taste cells, and claudin 8 was found around the pore. With the ion permeability features of the different claudins, a highly specific permeability pattern for paracellular diffusion is apparent, which indicates a peripheral mechanism for taste coding.

Aims : Claudins are adhesion molecules present in tight junctions. To evaluate their usefulness as differentiation markers claudins 1, 2, 3, 4, 5 and 7 were studied in 116 epithelial and 92 non-epithelial tumours. Methods and results : Immunoreactivity for all claudins could be seen in different carcinomas. There were, however, tumour type-specific differences in their expression. Lower expression of claudin 2 was seen in breast and prostatic carcinomas, while hepatocellular and renal carcinomas expressed lower levels of claudins 4 and 5. In contrast to epithelial tumours, lymphomas did not express claudins and most soft tissue tumours and naevocytic lesions were negative or showed weaker, mainly cytoplasmic positivity for some claudins. Of non-epithelial tumours, claudin 5 was found only in angiosarcomas and benign vascular tumours, which also showed reactivity for claudins 2, 3 and 7, but was not expressed in any other soft tissue lesions or lymphomas. Conclusions : The results show that claudins 1, 2, 3, 4, 5 and 7 can be used as markers for epithelial differentiation and to distinguish epithelial neoplasms from lymphomas and selectively also from soft tissue and naevocytic lesions. Since these claudins show type-specific differential expression in epithelial tumours, they may also be of some value in distinguishing different epithelial tumours from each other. Additionally, claudin 5 shows promise as a marker for endothelial lesions compared with other soft tissue lesions.

The expression of claudin-4 was investigated in human pancreas, pancreatic ductal adenocarcinomas, and intraductal papillary-mucinous tumors of the pancreas (IPMT), and compared with that of claudin-1. In human adult pancreatic specimens, both claudin-1 and claudin-4 were immunohistochemically found in main and branching pancreatic ducts, terminal ductules and acinic cells, with the exception of endocrine cells. Of 12 cases of pancreatic ductal adenocarcinoma, 11 (92%) had positive immunostaining for claudin-4, and seven (58%) for claudin-1. In 44 lesions of 22 cases of IPMT, including six hyperplastic foci distant from the main lesions, clauidin-1 was positive in three out of six (50%) hyperplastic foci, 14 out of 17 (82%) adenomas, three out of 10 (30%) borderline tumors, two out of six (33%) non-invasive carcinomas, and one out of five (20%) invasive carcinomas, producing a statistically negative correlation with histological tumor grades. In contrast, claudin-4 was negative in the six hyperplastic foci, and positive in four out of the 17 (24%) adenomas, five out of the 10 (50%) borderline tumors, five out of the six (83%) non-invasive carcinomas, and four out of the five (80%) invasive carcinomas, producing a statistically positive correlation with histological tumor grades. On study of IPMT subtypes, claudin-1 was positive in nine out of 10 (90%) clear-cell types, seven out of 20 (35%) dark-cell types, and four out of eight (50%) compact-cell types. In contrast, claudin-4 was positive in two out of the 10 (20%) clear-cell types, 13 out of the 20 (65%) dark-cell types, and three out of the eight (38%) compact-cell types. These distinct expression patterns of claudin-1 and claudin-4 suggest that both claudins serve as useful molecular markers for the tumor classification of IPMT.

Tight junctions (TJs) are essential features of endothelial barrier membranes and of fluid-secreting epithelial cells, such as in the salivary glands. Novel integral membrane proteins have been identified as components of TJs, namely claudins and occludin. The aim of the present study was to determine the distribution of occludin and claudins in the large salivary glands of the rat. The parotid, submandibular and sublingual salivary glands were harvested from adult Sprague–Dawley rats and cryostat sections were stained using immunoperoxidase and immunofluorescence methods. Claudin-1 was expressed in endothelial cells of microvessels and in short selected segments of the duct system. Claudin-3 was expressed principally in the acinar cells and intercalated ducts, while claudin-4 was principally expressed by the striated and interlobular ducts. Claudin-5 was specific to endothelial cells of microvessels. Occludin was ubiquitously detected in the duct system. Double labelling and confocal microscopy showed some co-localization of claudin-3 with claudin-4, and minimal co-localization of occludin with claudin-4, in the striated ducts. Claudin 2 was not detected in any of the salivary glands. The results indicate specificity of the chemical composition of tight junctions in the rat salivary glands, and may reflect different physiological roles for TJs in the glandular and duct epithelial cells, and in endothelial cells of salivary gland microvessels.

Recent remarkable progress in genomic novel drug discovery enables us to prepare drug candidates with tremendous diversity in a high-throughput-manner. In clinical use of these candidates, they should be effectively delivered to a target-tissue in body. But delivery systems suitable for the high-throughput discovery of drugs have never been established. Tight junctions (TJs) play a pivotal role in compartmentation of each tissues and maintenance of their intra-circumstances. Claudin, a membrane protein with four trans-membrane domains, have recently found to be responsible for the barrier-function of TJs. Claudin is constituted of 24 family members, and expression profiles and barrier-function of claudin differ interestingly among the family members. These findings indicate that a modulator of the unique barrier-function of claudin may be used for drug delivery. In this respect, we have investigated whether a claudin is a target for drug delivery. A claudin modulator (C-terminal fragment of Clostridium perfringens enterotoxin, C-CPE) had 400-fold jejunal absorption-enhancing activity to a clinically used absorption-enhancer, and interaction between C-CPE and claudin was essential for the enhancing activity. We have already prepared a screening system for claudin-targeting molecule. Now we are performing functional domain mapping of C-CPE, and we will attempt to prepare a various type of claudin modulator in a future. In the current review, I introduce our recent works on development of a novel strategy for drug delivery system using claudin modulator, and I discuss also possibility of claudin modulator in drug delivery system.