SEMP1, a senescence-associated cDNA isolated from human mammary epithelial cells, is a member of an epithelial membrane protein superfamily

Developmental stage and infection status may affect drug distribution in the prostate of rats

Prostate inflammation is often treated with drugs which are ineffective. Antibacterial agents fail to reach the prostate epithelium, and the blood-prostate barrier (BPB) may affect the drug transport process. Factors affecting drug efficacy remain unclear.Rats were categorised into groups A and B, corresponding to adulthood and puberty, respectively. Group C included the model of chronic prostate infection. Dialysates of levofloxacin and cefradine were collected from the prostate gland and jugular vein and evaluated. Pharmacokinetic analysis was conducted.The free concentrations of antimicrobials in the prostate and plasma samples of all groups peaked at 20 min, then gradually decreased. The mean AUC0-tprostate/AUC0-tplasma ratio in the levofloxacin group were 0.86, 0.53, and 0.95, and the mean values of AUC0-∞prostate/AUC0-∞plasma ratio were 0.85, 0.63, and 0.97. The corresponding values in the cefradine group were 0.67, 0.30 and 0.84, and 0.66, 0.31, and 0.85, respectively. The mean values in group B were lower than those in group A, and those in group C were higher than those in group B.The maturity of the prostate may affect the ability of the drug to cross the BPB. Infection may disrupt the BPB, affecting drug permeability.

Research progress of Claudin-low breast cancer

Claudin-low breast cancer (CLBC) is a subgroup of breast cancer discovered at the molecular level in 2007. Claudin is one of the primary proteins that make up tight junctions, and it plays crucial roles in anti-inflammatory and antitumor responses as well as the maintenance of water and electrolyte balance. Decreased expression of claudin results in the disruption of tight junction structures and the activation of downstream signaling pathways, which can lead to tumor formation. The origin of Claudin-low breast cancer is still in dispute. Claudin-low breast cancer is characterized by low expression of Claudin3, 4, 7, E-cadherin, and HER2 and high expression of Vimentin, Snai 1/2, Twist 1/2, Zeb 1/2, and ALDH1, as well as stem cell characteristics. The clinical onset of claudin-low breast cancer is at menopause age, and its histological grade is higher. This subtype of breast cancer is more likely to spread to lymph nodes than other subtypes. Claudin-low breast cancer is frequently accompanied by increased invasiveness and a poor prognosis. According to a clinical retrospective analysis, claudin-low breast cancer can achieve low pathological complete remission. At present, although several therapeutic targets of claudin-low breast cancer have been identified, the effective treatment remains in basic research stages, and no animal studies or clinical trials have been designed. The origin, molecular biological characteristics, pathological characteristics, treatment, and prognosis of CLBC are extensively discussed in this article. This will contribute to a comprehensive understanding of CLBC and serve as the foundation for the individualization of breast cancer treatment.

In Vivo Ultrafast Doppler Imaging Combined with Confocal Microscopy and Behavioral Approaches to Gain Insight into the Central Expression of Peripheral Neuropathy in Trembler-J Mice

The main human hereditary peripheral neuropathy (Charcot-Marie-Tooth, CMT), manifests in progressive sensory and motor deficits. Mutations in the compact myelin protein gene pmp22 cause more than 50% of all CMTs. CMT1E is a subtype of CMT1 myelinopathy carrying micro-mutations in pmp22. The Trembler-J mice have a spontaneous mutation in pmp22 identical to that present in CMT1E human patients. PMP22 is mainly (but not exclusively) expressed in Schwann cells. Some studies have found the presence of pmp22 together with some anomalies in the CNS of CMT patients. Recently, we identified the presence of higher hippocampal pmp22 expression and elevated levels of anxious behavior in TrJ/+ compared to those observed in wt. In the present paper, we delve deeper into the central expression of the neuropathy modeled in Trembler-J analyzing in vivo the cerebrovascular component by Ultrafast Doppler, exploring the vascular structure by scanning laser confocal microscopy, and analyzing the behavioral profile by anxiety and motor difficulty tests. We have found that TrJ/+ hippocampi have increased blood flow and a higher vessel volume compared with the wild type. Together with this, we found an anxiety-like profile in TrJ/+ and the motor difficulties described earlier. We demonstrate that there are specific cerebrovascular hemodynamics associated with a vascular structure and anxious behavior associated with the TrJ/+ clinical phenotype, a model of the human CMT1E disease.

Effects of resistance training, palm pollen grain extracts, and testosterone injection on luteinizing hormone receptors, claudin-1, cingulin, and zonula occludens in the prostate tissues of adult male rats

The present study aimed to investigate the effects of resistance training, Phoenix dactylifera extract, and testosterone enanthate injection on luteinizing hormone receptor, claudin-1, cingulin, and zonula occludens in the prostate tissues of adult rats. 30 male rats were divided into six groups: (1) control, (2) resistance training, (3) Phoenix dactylifera extract, (4) testosterone enanthate, (5) resistance training+Phoenix dactylifera extract, and (6) resistance training + testosterone enanthate. After completing the treatments and resistance training, all rats were sacrificed via anaesthesia. The results showed that resistance training, Phoenix dactylifera, and testosterone enanthate significantly increased the luteinizing hormone receptor, claudin-1, cingulin, and zonula occludens gene expression levels in the prostate. The resistance training treatment, along with Phoenix dactylifera + testosterone enanthate, exerted synergic effects on the prostate luteinizing hormone receptor levels and claudin-1 gene expression. In conclusion, Phoenix dactylifera, as a natural compound with fewer side effects than testosterone injection, can be used to enhance athletic performance. Besides, considering the potential benefits of Phoenix dactylifera, it can be considered in the treatment of testosterone deficiency; however, further research is needed.

Cell type diversity in scallop adductor muscles revealed by single-cell RNA-Seq

Studies on cell atlas in marine invertebrates provide a better understanding of cell types, stem cell maintenance, and lineages of cell differentiation. To investigate the molecular features of various cell types in molluscan muscles, we performed single-cell RNA sequencing (scRNA-seq) to map cell types in scallop adductor muscles. We uncovered the cell type-specific features of 20 cell clusters defined by the expression of multiple specific molecular markers. These cell clusters are mainly classified into four broad classes, including mesenchymal stem cells, muscle cells, neurons, and haemolymph cells. In particular, we identified a diverse repertoire of neurons in the striated adductor muscle, but not in the smooth muscle. We further reconstructed the cell differentiation events using all the cell clusters by single-cell pseudotemporal trajectories. By integrating dual BrdU-PCNA immunodetection, neuron-specific staining and electron microscopy observation, we showed the spatial distribution of mesenchymal stem cells and neurons in striated adductor muscle of scallops. The present findings will not only be useful to address the cell type-specific gene expression profiles in scallop muscles, but also provide valuable resources for cross-species comparison of marine organisms.

Claudin 1 inhibits cell migration and increases intercellular adhesion in triple-negative breast cancer cell line

Triple-negative "claudin 1 low" subtype represents around 15% of breast cancer and displays poor prognosis. The loss of claudin 1 is correlated with increased invasiveness and higher recurrence of the disease. Claudin 1 constitutes the backbone of the tight junction and is involved in cell-cell adhesion and migration processes. However, studies showed a controversial role of claudin 1 in cell migration. In this study, we aimed to clarify the effect of claudin 1 on migration of mesenchymal triple-negative breast cancer cells (TNBC). We reported that transient over expression of claudin 1 in MDA-MB-231 and Hs578T "claudin 1 low" TNBC cells inhibited cell migration using wound healing and transwell migration assays. In order to investigate more specifically the involvement of claudin 1, we generated stable MDA-MB-231 clones overexpressing claudin 1. Interestingly, the level of claudin 1 was correlated to the inhibition of cell migration and to the increase of cell-cell aggregation associated with enhanced formation of β-catenin adherens junction and occludin tight junction. Finally, we reported for the first time the key role of claudin 1 in the inhibition of cell migration process associated with the disappearance of stress fibers. These data suggest that re-expression of claudin 1 could be a promising strategy for regulating the migration of TNBC which no longer express claudin 1.

IL-21 mediates microRNA-423-5p /claudin-5 signal pathway and intestinal barrier function in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of chronic and recurrent nonspecific inflammatory disorders, including Crohn's disease (CD) and ulcerative colitis (UC). Due to the persistent inflammation of intestinal mucosa caused by immune disorders, barrier dysfunction may be an essential cause of the pathogenesis of IBD. Therefore, exploring the mechanism is very important to clarify the pathogenesis of IBD. In our research, we provided evidence of IL-21 function in IBD. The junction complex protein claudin-5 may be a downstream gene of the IL-21. Anti-IL-21 administrated prevented DSS-simulative colitis via recovering claudin-5 expression in the human colonic epithelial cells. Meanwhile, we described that miR-423-5p could be involved in IL-21/ claudin-5 pathway by regulating NF-κB/MAPKs/JNK signaling pathway, which may provide a new therapeutic target for IBD.

miR-155 Regulates claudin1 Expression in Humans With Intestinal Mucosa Dysfunction After Brain Injury

Patients with craniocerebral trauma often have intestinal mucosal dysfunction, and the claudin1 protein plays an important role in intestinal mucosal function. Our previous work has shown that the expression of microRNA-155 (miR-155) in the peripheral blood of patients with craniocerebral trauma is decreased. Animal experiments also suggest that the expression of miR-155 is increased in the intestinal mucosa of mice with brain injury and the expression of claudin1 is decreased. We recruited 56 samples (35 patients with traumatic brain injury [TBI] and 21 patients without history of head trauma) to detect the expression of miR-155 on claudin1 regulation by quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, and so on. We also used the receiver operating characteristic curve (ROC) to further evaluate the diagnostic value of the 2 biomarkers. From the results, we found that the expression level of miR-155 and claudin1 in the case group was lower than that in the control group. Human miR-155 (Hsa-miR-155) may positively regulate intestinal mucosal function by inhibiting the expression of claudin1, leading to intestinal mucosal barrier dysfunction. Combining the ROC curve data, the results further prove that miR-155 and claudin1 might be the new clinical diagnostic markers and treatment targets for the intestinal mucosal barrier dysfunction after TBI.

Claudin-1, A Double-Edged Sword in Cancer

Claudins, a group of membrane proteins involved in the formation of tight junctions, are mainly found in endothelial or epithelial cells. These proteins have attracted much attention in recent years and have been implicated and studied in a multitude of diseases. Claudins not only regulate paracellular transepithelial/transendothelial transport but are also critical for cell growth and differentiation. Not only tissue-specific but the differential expression in malignant tumors is also the focus of claudin-related research. In addition to up- or down-regulation, claudin proteins also undergo delocalization, which plays a vital role in tumor invasion and aggressiveness. Claudin (CLDN)-1 is the most-studied claudin in cancers and to date, its role as either a tumor promoter or suppressor (or both) is not established. In some cancers, lower expression of CLDN-1 is shown to be associated with cancer progression and invasion, while in others, loss of CLDN-1 improves the patient survival. Another topic of discussion regarding the significance of CLDN-1 is its localization (nuclear or cytoplasmic vs perijunctional) in diseased states. This article reviews the evidence regarding CLDN-1 in cancers either as a tumor promoter or suppressor from the literature and we also review the literature regarding the pattern of CLDN-1 distribution in different cancers, focusing on whether this localization is associated with tumor aggressiveness. Furthermore, we utilized expression data from The Cancer Genome Atlas (TCGA) to investigate the association between CLDN-1 expression and overall survival (OS) in different cancer types. We also used TCGA data to compare CLDN-1 expression in normal and tumor tissues. Additionally, a pathway interaction analysis was performed to investigate the interaction of CLDN-1 with other proteins and as a future therapeutic target.

DNA Methylation Profiling Reveals Prognostically Significant Groups in Pediatric Adrenocortical Tumors: A Report From the International Pediatric Adrenocortical Tumor Registry

PURPOSE

Pediatric adrenocortical carcinomas (ACCs) are aggressive; the overall survival of patients with ACCs is 40%-50%. Appropriate staging and histologic classification are crucial because children with incomplete resections, metastases, or relapsed disease have a dismal prognosis. The clinical course of pediatric adrenocortical tumors (ACTs) is difficult to predict using the current classification schemas, which rely on subjective microscopic and gross macroscopic variables. Recent advances in adult ACT studies have revealed distinct DNA methylation patterns with prognostic significance that have not been systematically interrogated in the pediatric population.

PATIENTS AND METHODS

We performed DNA methylation analyses on 48 newly diagnosed ACTs from the International Pediatric Adrenocortical Tumor Registry and 12 pediatric adrenal controls to evaluate for distinct methylation groups. Pediatric methylation data were also compared systematically with the adult ACC cohort from The Cancer Genome Atlas (TCGA).

RESULTS

Two pediatric ACT methylation groups were identified and showed differences in selected clinicopathologic and outcome characteristics. The A1 group was enriched for CTNNB1 variants and unfavorable outcome. The A2 group was enriched for TP53 germline variants, younger age at onset, and favorable outcome. Pediatric ACT methylation groups were maintained when International Pediatric Adrenocortical Tumor Registry cohort data were combined with TCGA cohort data. The CpG-island hypermethylator phenotype characterizing the TCGA cohort was not identified in the pediatric patients. When methylome findings were combined with independent histopathologic review using the Wieneke criteria, a high-risk population was identified with uniform fatal outcome.

CONCLUSION

Our results indicate DNA methylation analysis can enhance current diagnostic algorithms. A combination of methylation and histologic classification produced the strongest prediction model and may prove useful in future risk-adapted therapeutic trials.

HOXA5 determines cell fate transition and impedes tumor initiation and progression in breast cancer through regulation of E-cadherin and CD24

Loss of HOXA5 expression occurs frequently in breast cancer and correlates with higher pathological grade and poorer disease outcome. However, how HOX proteins drive differentiation in mammalian cells is poorly understood. In this paper, we investigated cellular and molecular consequences of loss of HOXA5 in breast cancer, and the role played by retinoic acid in HOXA5 function. Analysis of global gene expression data from HOXA5-depleted MCF10A breast epithelial cells, followed by validation, pointed to a role for HOXA5 in maintaining several molecular traits typical of the epithelial lineage such as cell-cell adhesion, tight junctions and markers of differentiation. Depleting HOXA5 in immortalized MCF10A or transformed MCF10A-Kras cells reduced their CD24⁺/CD44^lo population, enhanced self-renewal capacity and reduced expression of E-cadherin (CDH1) and CD24. In the case of MCF10A-Kras, HOXA5 loss increased branching and protrusive morphology in Matrigel, all features suggestive of epithelial to basal transition. Further, orthotopically implanted xenografts of MCF10A-Kras-scr grew as well-differentiated pseudo-luminal carcinomas, while MCF10A-Kras-shHOXA5 cells formed aggressive, poorly differentiated carcinomas. Conversely, ectopic expression of HOXA5 in aggressive SUM149 or SUM159 breast cancer cells reversed the cellular and molecular alterations observed in the HOXA5-depleted cells. Retinoic acid is a known upstream regulator of HOXA5 expression. HOXA5 depletion in MCF10A cells engineered to express doxycycline-induced shHOXA5 slowed transition of cells from a less differentiated CD24^-/CD44⁺ to the more differentiated CD24⁺/CD44⁺ state. This transition was promoted by retinal treatment, which upregulated endogenous HOXA5 expression and caused re-expression of occludin and claudin-7 (CLDN7). Expression of CDH1 and CD24 was transcriptionally upregulated by direct binding of HOXA5 to their promoter sequences as demonstrated by luciferase and ChIP analyses. Thus, loss of HOXA5 in mammary cells leads to loss of epithelial traits, an increase in stemness and cell plasticity, and the acquisition of more aggressive phenotypes.

Opening tight junctions may be key to opening the blood-prostate barrier

The blood-prostate barrier could be the major factor that preventing delivery of drugs to prostate tissue and leads to the failure of treatment. Studies indicate that ultrasonic sonoporation can break the blood-prostate barrier and increase the concentration of drugs, but the mechanism is still unclear. Tight junctions exist widely in the endothelial and epithelial cells of mammalians, and form the biological barrier, along with other factors. Through studies on the mechanism of ultrasound microbubbles opening the blood-brain barrier, researchers found that the main mechanism is to change the expression level of TJs proteins. Since there might be some similarities between the blood-brain barrier and the blood-prostate barrier, changing the expression level of TJs proteins may also be the main mechanism by which ultrasound microbubbles opens the blood-prostate barrier, which is worth further study.

Distinct claudin expression characterizes BRCA1-related breast cancer

AIMS

Members of the claudin family are involved in cancer progression and are differentially expressed in subtypes of breast cancer. Breast cancers in BRCA1 germ line mutation carriers have distinct clinicopathological characteristics. Biomarkers that discriminate between BRCA1-related and sporadic breast cancer cases are needed to improve early identification of mutation carriers. In this study we evaluated protein expression of five major claudins in BRCA1-related breast cancers in comparison with sporadic controls.

METHODS AND RESULTS

Forty breast cancers in BRCA1 mutation carriers and 40 age-matched sporadic breast cancers were immunohistochemically stained for claudins 1, 3, 4, 6 and 7. Total intratumoural expression levels were compared to those in the surrounding normal tissue. In addition, subcellular claudin expression was scored. Higher overexpression rates were observed for all five claudins in BRCA1-related breast cancers when compared to sporadic controls. In multivariate analysis, overexpression of claudin 3, 4, and 7 was mainly dependent on ER-status, whereas overexpression of claudin 6 and high membranous expression of claudin 1 were independent of other characteristics.

CONCLUSIONS

BRCA1-related breast cancers are characterized by frequent overexpression of claudins. Especially claudin 1 and 6 expression may help to discriminate mutation carriers from sporadic breast cancer cases.

Anti-apoptotic effect of claudin-1 on TNF-α-induced apoptosis in human breast cancer MCF-7 cells

Accumulating evidence reveals that aberrant expression of claudins manifests in various tumors; however, their biological functions are poorly understood. Here, we report on the elevated expression of claudin-1 in human breast cancer MCF-7 cells under tumor necrosis factor (TNF)-α treatment. Interestingly, the increased expression of claudin-1 contributes to an anti-apoptotic role in TNF-α-induced apoptosis. In line with this, upon TNF-α stimulus, downregulation of claudin-1 by siRNA knockdown results in a significant increase in cleavage of caspase-8 and poly (ADP-ribose) polymerase, a decrease of cyclinD1 expression, and DNA fragmentation. Consistently, TdT-mediated dUTP nick end labeling assay also shows that loss of claudin-1 increases the susceptibility of MCF-7 cells to TNF-α-induced apoptosis. However, there is no obvious effect on the expression of Bax and p53 after the treatment aforementioned. In addition, TNF-α increases the amount of claudin-1 and the cytoplasmic accumulation of β-catenin, while claudin-1 siRNA increases the amount of β-catenin in the cell membrane as well as the amount of E-cadherin in the cytoplasm. In conclusion, our data reveal a novel role of claudin-1 in regulating apoptosis in MCF-7 cells.

High claudin-7 expression is associated with a poor response to platinum-based chemotherapy in epithelial ovarian carcinoma

BACKGROUND

Claudin-7 (CLDN-7) is a tight junction protein that has been shown overexpressed in several human cancers. We investigated prognostic significance of CLDN-7 overexpression in patients with epithelial ovarian carcinoma (EOC) and its functional role on cell proliferation in ovarian carcinoma cell lines.

PATIENTS AND METHODS

CLDN-7 expression was evaluated by real-time RT-PCR and immunohistochemical analysis in 71 patients with EOC. We assessed the association of CLDN-7 expressions with prognosis of the patients including sensitivity to platinum-based chemotherapy. In vitro experiment was performed with and without inhibition of CLDN-7 by its siRNA to evaluate the sensitivity of the human ovarian cancer cells to cisplatin chemotherapy.

RESULTS

CLDN-7 transcripts in EOCs were significantly up-regulated compared with normal ovarian tissues (P<0.001). The expression of CLDN-7 protein was observed in majority (69/71, 97.1%) of the EOCs but not in normal ovarian tissues (P<0.001). High CLDN-7 expression in primary tumour correlated with shorter progression-free survival (PFS) of the patients (P=0.005) and poor sensitivity to platinum-based chemotherapy (P=0.024). Moreover, CLDN-7 was highly expressed in 2774 and HeyA8 human ovarian cancer cells and inhibition of CLDN-7 by its siRNA significantly enhanced the sensitivity of 2774 and HeyA8 cells to cisplatin treatment.

CONCLUSION

These findings suggest CLDN-7 expression is an independent prognostic factor for PFS and it may play a role in regulating response to platinum-based chemotherapy in the treatment of EOC.

Specificity of interaction between clostridium perfringens enterotoxin and claudin-family tight junction proteins

Clostridium perfringens enterotoxin (CPE), a major cause of food poisoning, forms physical pores in the plasma membrane of intestinal epithelial cells. The ability of CPE to recognize the epithelium is due to the C-terminal binding domain, which binds to a specific motif on the second extracellular loop of tight junction proteins known as claudins. The interaction between claudins and CPE plays a key role in mediating CPE toxicity by facilitating pore formation and by promoting tight junction disassembly. Recently, the ability of CPE to distinguish between specific claudins has been used to develop tools for studying roles for claudins in epithelial barrier function. Moreover, the high affinity of CPE to selected claudins makes CPE a useful platform for targeted drug delivery to tumors expressing these claudins.

On the interaction of Clostridium perfringens enterotoxin with claudins

Clostridium perfringens causes one of the most common foodborne illnesses, which is largely mediated by the Clostridium perfringens enterotoxin (CPE). The toxin consists of two functional domains. The N-terminal region mediates the cytotoxic effect through pore formation in the plasma membrane of the mammalian host cell. The C-terminal region (cCPE) binds to the second extracellular loop of a subset of claudins. Claudin-3 and claudin-4 have been shown to be receptors for CPE with very high affinity. The toxin binds with weak affinity to claudin-1 and -2 but contribution of these weak binding claudins to CPE-mediated disease is questionable. cCPE is not cytotoxic, however, it is a potent modulator of tight junctions. This review describes recent progress in the molecular characterization of the cCPE-claudin interaction using mutagenesis, in vitro binding assays and permeation studies. The results promote the development of recombinant cCPE-proteins and CPE-based peptidomimetics to modulate tight junctions for improved drug delivery or to treat tumors overexpressing claudins.

Claudin 1 in breast tumorigenesis: revelation of a possible novel "claudin high" subset of breast cancers

Claudins are the major component of the tight junctions in epithelial cells and as such play a key role in the polarized location of ion channels, receptors, and enzymes to the different membrane domains. In that regard, claudins are necessary for the harmonious development of a functional epithelium. Moreover, defective tight junctions have been associated with the development of neoplastic phenotype in epithelial cells. Breakdown of cell-cell interactions and deregulation of the expression of junctional proteins are therefore believed to be key steps in invasion and metastasis. Several studies suggest that the claudins are major participants in breast tumorigenesis. In this paper, we discuss recent advances in our understanding of the potential role of claudin 1 in breast cancer. We also discuss the significance of a subset of estrogen receptor negative breast cancers which express “high” levels of the claudin 1 protein. We propose that claudin 1 functions both as a tumor suppressor as well as a tumor enhancer/facilitator in breast cancer.

Tight junctions: a barrier to the initiation and progression of breast cancer?

Breast cancer is a complex and heterogeneous disease that arises from epithelial cells lining the breast ducts and lobules. Correct adhesion between adjacent epithelial cells is important in determining the normal structure and function of epithelial tissues, and there is accumulating evidence that dysregulated cell-cell adhesion is associated with many cancers. This review will focus on one cell-cell adhesion complex, the tight junction (TJ), and summarize recent evidence that TJs may participate in breast cancer development or progression. We will first outline the protein composition of TJs and discuss the functions of the TJ complex. Secondly we will examine how alterations in these functions might facilitate breast cancer initiation or progression; by focussing on the regulatory influence of TJs on cell polarity, cell fate and cell migration. Finally we will outline how pharmacological targeting of TJ proteins may be useful in limiting breast cancer progression. Overall we hope to illustrate that the relationship between TJ alterations and breast cancer is a complex one; but that this area offers promise in uncovering fundamental mechanisms linked to breast cancer progression.

Altered serotonin physiology in human breast cancers favors paradoxical growth and cell survival

Introduction

The breast microenvironment can either retard or accelerate the events associated with progression of latent cancers. However, the actions of local physiological mediators in the context of breast cancers are poorly understood. Serotonin (5-HT) is a critical local regulator of epithelial homeostasis in the breast and other organs. Herein, we report complex alterations in the intrinsic mammary gland serotonin system of human breast cancers.

Methods

Serotonin biosynthetic capacity was analyzed in human breast tumor tissue microarrays using immunohistochemistry for tryptophan hydroxylase 1 (TPH1). Serotonin receptors (5-HT1-7) were analyzed in human breast tumors using the Oncomine database. Serotonin receptor expression, signal transduction, and 5-HT effects on breast cancer cell phenotype were compared in non-transformed and transformed human breast cells.

Results

In the context of the normal mammary gland, 5-HT acts as a physiological regulator of lactation and involution, in part by favoring growth arrest and cell death. This tightly regulated 5-HT system is subverted in multiple ways in human breast cancers. Specifically, TPH1 expression undergoes a non-linear change during progression, with increased expression during malignant progression. Correspondingly, the tightly regulated pattern of 5-HT receptors becomes dysregulated in human breast cancer cells, resulting in both ectopic expression of some isoforms and suppression of others. The receptor expression change is accompanied by altered downstream signaling of 5-HT receptors in human breast cancer cells, resulting in resistance to 5-HT-induced apoptosis, and stimulated proliferation.

Conclusions

Our data constitutes the first report of direct involvement of 5-HT in human breast cancer. Increased 5-HT biosynthetic capacity accompanied by multiple changes in 5-HT receptor expression and signaling favor malignant progression of human breast cancer cells (for example, stimulated proliferation, inappropriate cell survival). This occurs through uncoupling of serotonin from the homeostatic regulatory mechanisms of the normal mammary epithelium. The findings open a new avenue for identification of diagnostic and prognostic markers, and valuable new therapeutic targets for managing breast cancer.

CIIA induces the epithelial-mesenchymal transition and cell invasion

Epithelial-mesenchymal transition (EMT) and the acquisition of invasive potential are key events in tumor progression. We now show that CIIA, originally identified as an anti-apoptotic protein, induces the EMT and promotes cell migration and invasion. Ectopic expression of CIIA induced down-regulation of E-cadherin and claudin-1 as well as up-regulation of N-cadherin in MDCK cells. It also disrupted the differentiated epithelial morphology of MDCK cells grown in three-dimensional Matrigel cultures as well as increased the migration and invasion of MDCK cells in vitro. Furthermore, depletion of endogenous CIIA by RNA interference inhibited the migration and invasion of HeLa cells, and this inhibition was abolished by RNA interference-mediated depletion of claudin-1. These results suggest that CIIA functions as an inducer of cell invasion, and this effect is mediated, at least in part, through down-regulation of claudin-1.

Expression of claudin-1, -2, -3, -4, -5 and -7 proteins in benign and malignant canine mammary gland epithelial tumours

Claudins are tight junction proteins expressed by epithelial and endothelial cells. The present study has evaluated the expression of claudin-1, -2, -3, -4, -5 and -7 in 115 hyperplastic and neoplastic lesions of the canine mammary gland and compared this expression with that of normal mammary epithelium. The lesions studied included lobular hyperplasia (n=15), simple adenoma (n=20), non-infiltrating carcinoma in situ (n=20) and infiltrating carcinomas of histological grades I, II and III (n=20 of each). There was strong expression of claudin-1, -3, -4, -5 and -7 by epithelia within examples of lobular hyperplasia and simple adenoma, and strong expression of claudin-3 and -4 by non-infiltrating carcinomas and all three grades of infiltrating carcinoma. By contrast, there was reduced expression of claudin-5 and -7 by non-infiltrating and infiltrating carcinomas and the expression of these two molecules was inversely correlated with histological grade. Claudin-1 was expressed focally within carcinoma in situ, but this molecule was not detected in any invasive carcinoma. Claudin-2 was weakly expressed within areas of lobular hyperplasia and by simple adenomas, but was not expressed by any carcinoma cells. These results suggest that loss or reduction of expression of claudin-1, -2, -5 and -7 may lead to cellular disorientation, detachment and invasion in canine mammary neoplasia.

Expression and localisation of claudin-1, -2, -3, -4, -5, -7 and -10 proteins in the normal canine mammary gland

The recently identified claudins are dominant components of tight junctions, responsible for cell adhesion, polarity and paracellular permeability. Certain claudins have been shown to have relevance in tumour development. The aim of the present study was to analyse the expression of claudin-1, -2, -3, -4, -5, -7 and -10 in normal canine mammary glands. Samples from the inguinal mammary regions of 20 non-castrated, 1-13 years old female dogs were studied. Immunohistochemical analysis was performed on conventional specimens and tissue microarrays. The results of the immunohistochemical reactions detecting claudins in tissue sections were photodocumented. The immunoreactivity of claudins was quantitatively analysed on digital images using Leica QWin morphometry software. Intense membranous immunolabelling was found for claudin-1, -3 and -7, intense membranous with non-granular cytoplasmic immunolabelling for claudin-2, moderate membranous immunolabelling for claudin-4 and -5, and weak membranous immunolabelling for claudin-10. The occurrence of tight junctions was confirmed by ultrathin section electron microscopy. The available data suggested that claudins might be proteins preserved throughout the evolution of mammals. The results of our study support the concept that they are indeed preserved, since the same type of claudins, in identical distribution, could be detected in our canine mammary tissue samples as could be found in human mammary tissue.

Down-regulation of claudin-2 in breast carcinomas is associated with advanced disease

AIMS

Claudin 2 (CLDN2) is a family of integral membrane tight junctions. The aim was to determine the influence of CLDN2 expression on tumour behaviour and its role in breast carcinogenesis.

METHOD AND RESULTS

Thirty-seven invasive breast carcinomas and corresponding normal breast tissues were examined for CLDN2 protein and mRNA expression using Western blotting and semiquantitative reverse transcriptase-polymerase chain reaction. The expression of CLDN2 protein in 118 cases of breast carcinoma was further studied with immunohistochemistry and related to various clinicopathological parameters. CLDN2 protein expression was significantly down-regulated (0.4-fold) in tumours compared with corresponding normal breast tissue (P < 0.0001). Down-regulation of CLDN2 was significantly associated with lymph node metastasis (P = 0.047) by Western blot analysis, and with high clinical stage (P = 0.040) by immunohistochemistry. The expression levels of CLDN2 mRNA in high clinical stages (stages II and III) were lower than those in low clinical stage (stage I) and normal tissue, but not statistically significantly so.

CONCLUSIONS

These results suggest that CLDN2 is implicated in the progression as well as the development of breast carcinoma, indicating that CLDN2 is a possible tumour suppressor gene product.

Tight junctions and the modulation of barrier function in disease

Tight junctions create a paracellular barrier in epithelial and endothelial cells protecting them from the external environment. Two different classes of integral membrane proteins constitute the tight junction strands in epithelial cells and endothelial cells, occludin and members of the claudin protein family. In addition, cytoplasmic scaffolding molecules associated with these junctions regulate diverse physiological processes like proliferation, cell polarity and regulated diffusion. In many diseases, disruption of this regulated barrier occurs. This review will briefly describe the molecular composition of the tight junctions and then present evidence of the link between tight junction dysfunction and disease.

Claudin-1 and claudin-5 expression patterns differentiate lung squamous cell carcinomas from adenocarcinomas

We investigated the expression of tight junction proteins in human lung squamous cell carcinomas and adenocarcinomas by immunohistochemistry and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). We found a statistically significant correlation between diagnosis and positivity of tumors with either claudin (CLDN)-1 or CLDN-5. Squamous cell carcinomas and basal cells of bronchial epithelium were positive for CLDN-1 and negative for CLDN-5, whereas adenocarcinomas, normal cylindrical cells and pneumocytes were positive for CLDN-5 and negative for CLDN-1, suggesting different pathways in tumor development and progression. CLDN-4 and ZO-1 staining were detected in both types of tumors, whereas cingulin (CGN) was not detected in squamous cell carcinomas. Quantitative RT-PCR was used to evaluate changes in transcript levels for a large panel of tight junction proteins. In squamous cell carcinomas, we observed statistically significant decreases in the mRNA levels of JAM-1, occludin, CLDN-3, CLDN-4, CLDN-7, CGN, ZO-2 and ZO-3, and an increase in CLDN-1 mRNA. In adenocarcinomas, when transcript levels were compared with bronchial cells, we observed statistically significant decreases in the mRNA levels of CLDN-1, CLDN-3, CLDN-4, CLDN-7, ZO-2 and ZO-3. These results indicate that characterization of tight junction protein expression in human lung tumors can be an additional diagnostic tool and provide new insights on their histogenesis.

Claudin-1 immunohistochemistry for distinguishing malignant from benign epithelial lesions of prostate

BACKGROUND

Claudins are a family of approximately 23 integral membrane tight junction (TJ) proteins that maintain cell polarity and paracellular barrier functions in epithelial and endothelial cells. Although Claudin-1 was demonstrated to be typically downregulated in various cancers, the precise expression patterns of this protein in normal and neoplastic tissues remain poorly characterized.

METHODS

Using immunohistochemistry, the expression of Claudin-1 was investigated in prostate tissue samples arranged in a tissue microarray (TMA) format and comprising elements of normal prostatic epithelium (n = 6), benign prostatic hyperplasia (BPH; n = 38), prostatic intraepithelial neoplasia (PIN; n = 11), and prostate adenocarcinoma (n = 48). The Claudin-1 expression pattern was compared with that of the basal cell-specific markers, p63, and HMW cytokeratin (34betaE12), by employing double-labeling techniques in conjunction with image analysis methods utilizing color deconvolution algorithms.

RESULTS

In benign prostatic epithelium, pronounced Claudin-1 expression was observed in the basal cell layer with no staining in luminal cells. Prostate adenocarcinoma specimens from 98% (47/48) patients lacked Claudin-1 immunostaining, and no cases contained >5% immunopositive tumor cells.

CONCLUSIONS

Claudin-1 immunohistochemistry should be considered for use as a new diagnostic tool for distinguishing malignant from benign lesions of the prostate.

Histone Deacetylase 2 Modulates p53 Transcriptional Activities through Regulation of p53-DNA Binding Activity

Histone deacetylase (HDAC) inhibitors are emerging as promising cancer therapeutics. HDAC inhibitors have been found to induce cellular activities that are strikingly similar to p53-mediated responses to genotoxic stress. For example, HDAC inhibitors induce cell cycle arrest, apoptosis, and cellular senescence. Because at least 11 HDACs are affected by the current HDAC inhibitors, the HDAC critical for tumor cell survival and proliferation remains unknown. Thus, we sought to characterize the distinct roles of HDACs in the p53 pathway. Through the use of stable MCF7 cell lines which inducibly express short hairpin RNA targeting HDAC2, we found that HDAC2 plays important roles in the p53 pathway. Specifically, we found that knockdown of HDAC2 inhibited cellular proliferation in a dose-dependent manner which was also partly p53-dependent. Furthermore, knockdown of HDAC2 induced cellular senescence. Importantly, we found that knockdown of HDAC2 enhanced p53-dependent trans-repression and trans-activation of a subset of target genes. We found that the enhancement was due to increased p53-DNA binding activity but not alterations in p53 stability or posttranslational modification(s). Thus, for the first time, our data suggest that HDAC inhibitors function through the p53 pathway, at least in part, by activating p53-DNA binding activity.

Expression patterns of claudin family of tight-junction proteins in the mouse prostate

Claudins are the transmembrane proteins forming the backbone of tight junctions, and consist of over 20 members of a gene family. Claudins are expressed in a tissue- and cell-type specific fashion, and changes in their abundance and/or distribution are proposed to play important roles in the pathophysiology of numerous disorders. In the prostate, claudin-1, -3, -4 and -7 transcripts are known to be expressed, but it is unknown regarding mRNA expression of other claudins or concerning expression and localization of claudin proteins in this organ. We herein show, by RT-PCR and Western blotting analyses, that not only these four claudins but also claudin-5, -8 and -10 are expressed in the normal mouse prostate. Claudin-3, -4, -5, -8 and -10 were primarily localized at the apicalmost sites of lateral membranes of luminal epithelial cells in the prostate gland, whereas claudin-1 and -7 were distributed along the basolateral membranes of the epithelium. These findings provide basic information for elucidating the significance of claudins in prostate diseases, including prostate cancers.

Activation of an SP binding site is crucial for the expression of claudin 1 in rat epididymal principal cells

Claudin 1 (CLDN1) is a tight junctional protein present in the epididymis. Limited information exists regarding the regulation of Cldn1 transcription. In the epididymis, the regulation of the 5' flanking region of genes coding for tight junctional proteins is unknown. The present objectives were to investigate the transcriptional regulation of the Cldn1 gene in the rat epididymis. A 1.8-kb sequence of the 5' flanking region of the rat Cldn1 gene was cloned. The transcriptional start site is an adenine located at the -198 position relative to the first codon, and 26 bp downstream of the putative TATA box. It is the only start site for the Cldn1 gene transcription in the rat epididymis. The Cldn1 promoter was inserted into a luciferase gene expression vector and transfected into a rat caput epididymal cell line (RCE-1). Sequential deletion analysis revealed that minimal promoter activity was achieved with the construct containing -61 to +164 bp of the promoter. This sequence contained a TATA box and two consensus SP1 binding sites. Electrophoretic mobility shift and supershift assays confirmed that SP1 and SP3 were present in RCE-1 cells and epididymal nuclear extracts, and that they bind to the 5' SP1 binding motif of the promoter. Site-directed mutagenesis of the 5' SP1 binding site resulted in a 4-fold decrease in transactivation of the minimal promoter sequence. These findings indicate that SP1 and SP3 bind to the Cldn1 promoter region, and that this interaction influences the expression of Cldn1 in the rat epididymis.

In utero exposure to tributyltin alters the expression of e-cadherin and localization of claudin-1 in intercellular junctions of the rat ventral prostate

Tributyltin (TBT) is an environmental contaminant, exhibiting well-established toxicity to reproductive systems in aquatic organisms. Little information exists regarding the effects of TBT on mammalian reproduction. Cellular junctions are crucial for sperm development and maturation. Intercellular tight junctions are formed by transmembrane proteins such as claudins (Cldns), while the formation of tight junctions involves signaling components of adhering junctions, comprised of cadherins. The objectives of this study were to determine the effects of in utero exposure to TBT on the rat ventral prostate. Pregnant Sprague-Dawley rats were given doses of TBT (2.5, 10, or 20 mg/kg) throughout gestation and sacrificed at Day 91. Ventral prostate weights of TBT-treated rats were decreased in all treatment groups. Results of gene expression macro-array analysis indicated that numerous genes related to cellular adhesion and cell polarity were affected. Cldn-1 mRNA levels decreased after exposure to TBT. Cldn-1 was immunolocalized to the apical lateral margins of adjacent prostatic epithelial cells in controls, but was increasingly dispersed along the lateral plasma membrane with increasing TBT dose, suggesting that the targeting of Cldn-1 or its localization to tight junctions was altered as a result of fetal TBT exposure. E-cadherin mRNA levels and immunolocalization were decreased in a dose-dependent manner. These data indicate that in utero TBT exposure results in permanent alterations in ventral prostate and that these are associated with alterations in the expression and distribution of cell adhesion and tight junctional proteins.

Large DNA palindromes as a common form of structural chromosome aberrations in human cancers

Breakage-fusion-bridge cycles contribute to chromosome aberrations and generate large DNA palindromes that facilitate oncogene amplification in cancer cells. At the molecular level, large DNA palindrome formation is initiated by chromosome breaks, and genomic architecture such as short inverted repeat sequences facilitates this process in mammalian cells. However, the prevalence of DNA palindromes in cancer cells is currently unknown. To determine the prevalence of DNA palindromes in human cancer cells, we have developed a new microarray-based approach called Genome-wide Analysis of Palindrome Formation (GAPF, Tanaka et al., Nat Genet 2005; 37: 320-7). This approach is based on a relatively simple and efficient method to purify "snap-back DNA" from large DNA palindromes by intramolecular base-pairing, followed by elimination of single-stranded DNA by nuclease S1. Comparison of Genome-wide Analysis of Palindrome Formation profiles between cancer and normal cells using microarray can identify genome-wide distributions of somatic palindromes. Using a human cDNA microarray, we have shown that DNA palindromes occur frequently in human cancer cell lines and primary medulloblastomas. Significant overlap of the loci containing DNA palindromes between Colo320DM and MCF7 cancer cell lines suggests regions in the genome susceptible to chromosome breaks and palindrome formation. A subset of loci containing palindromes is associated with gene amplification in Colo320DM, indicating that the location of palindromes in the cancer genome serves as a structural platform that supports subsequent gene amplification.

The transcription factors Slug and Snail act as repressors of Claudin-1 expression in epithelial cells

Claudin-1 is an integral membrane protein component of tight junctions. The Snail family of transcription factors are repressors that play a central role in the epithelial-mesenchymal transition, a process that occurs during cancer progression. Snail and Slug members are direct repressors of E-cadherin and act by binding to the specific E-boxes of its proximal promoter. In the present study, we demonstrate that overexpression of Slug or Snail causes a decrease in transepithelial electrical resistance. Overexpression of Slug and Snail in MDCK (Madin-Darby canine kidney) cells down-regulated Claudin-1 at protein and mRNA levels. In addition, Snail and Slug are able to effectively repress human Claudin-1-driven reporter gene constructs containing the wild-type promoter sequence, but not those with mutations in two proximal E-box elements. We also demonstrate by band-shift assay that Snail and Slug bind to the E-box motifs present in the human Claudin-1 promoter. Moreover, an inverse correlation in the levels of Claudin-1 and Slug transcripts were observed in breast cancer cell lines. E-box elements in the Claudin-1 promoter were found to play a critical negative regulatory role in breast cancer cell lines that expressed low levels of Claudin-1 transcript. Significantly, in invasive human breast tumours, high levels of Snail and Slug correlated with low levels of Claudin-1 expression. Taken together, these results support the hypothesis that Claudin-1 is a direct downstream target gene of Snail family factors in epithelial cells.

Differential expression of claudin 1, 3, and 4 during normal mammary gland development in the mouse

The claudins are a family of tight junction proteins that display varied tissue distribution and preferential specificity. We recently identified by microarray analysis, members of this family, particularly claudin 1 (cldn1), as highly upregulated genes in the mouse mammary gland during early involution. Gene expression was confirmed by immunohistochemistry and real-time PCR. We then examined gene and protein expression throughout normal mammary gland development. The cldn3 gene showed a steady increase in expression from pregnancy to involution, while cldn1 and cldn4 gene expression increased during pregnancy, but decreased sharply by D10 of lactation, and once again was significantly increased by D1 of involution (P < 0.001 for both genes). The different patterns of gene expression observed between cldn3, and cldn1, and 4 suggest that different family members may be functionally important at different times during mouse mammary gland development. All three genes exhibited a high level of expression at day 1 (D1) of involution, followed by a dramatic decrease in gene expression to day 10 of involution. Immunostaining with the cldn3 antibody showed intense staining of epithelial cells; however, a lesser degree of staining was evident with the cldn1 antibody. In addition to the lateral staining of epithelial cells, basal staining was evident at D1 and D2 of involution and cytoplasmic staining was evident during lactation. Since claudins are known to play a role as tight junction proteins, lateral and basal staining may suggest a role in other functions such as vesicle trafficking or remodeling of tight junctions at different stages of mammary gland development. Cldn1 and 3 antibodies also stained epithelial cells in mouse mammary tumors. In summary, cldn1, 3, and 4 are differentially expressed in the mammary gland during pregnancy, lactation, and involution, suggesting different roles for these proteins at different stages of mammary gland function. In addition, cldn1 and cldn3 are detected in mammary tumors and the wide distribution of cldn3 in particular, suggest specific roles for these proteins in mammary tumorigenesis.

Alterations in heart looping induced by overexpression of the tight junction protein Claudin-1 are dependent on its C-terminal cytoplasmic tail

In vertebrates, the positioning of the internal organs relative to the midline is asymmetric and evolutionarily conserved. A number of molecules have been shown to play critical roles in left-right patterning. Using representational difference analysis to identify genes that are differentially expressed on the left and right sides of the chick embryo, we cloned chick Claudin-1, an integral component of epithelial tight junctions. Here, we demonstrate that retroviral overexpression of Claudin-1, but not Claudin-3, on the right side of the chick embryo between HH stages 4 and 7 randomizes the direction of heart looping. This effect was not observed when Claudin-1 was overexpressed on the left side of the embryo. A small, but reproducible, induction of Nodal expression in the perinodal region on the right side of the embryo was noted in embryos that were injected with Claudin-1 retroviral particles on their right sides. However, no changes in Lefty,Pitx2 or cSnR expression were observed. In addition, Flectin expression remained higher in the left dorsal mesocardial folds of embryos with leftwardly looped hearts resulting from Claudin-1 overexpression on the right side of the embryo. We demonstrated that Claudin-1's C-terminal cytoplasmic tail is essential for this effect: mutation of a PKC phosphorylation site in the Claudin-1 C-terminal cytoplasmic domain at threonine-206 eliminates Claudin-1's ability to randomize the direction of heart looping. Taken together, our data provide evidence that appropriate expression of the tight junction protein Claudin-1 is required for normal heart looping and suggest that phosphorylation of its cytoplasmic tail is responsible for mediating this function.

Differences in expression patterns of the tight junction proteins,claudin 1, 3, 4 and 5, in human ovarian surface epithelium as compared to epithelia in inclusion cysts and epithelial ovarian tumours

Human ovarian surface epithelium (OSE), regarded as the precursor cell of epithelial ovarian adenocarcinoma, is not a fully developed epithelium when situated on the ovarian surface. It lacks epithelial characteristics such as the cell-cell adhesion factor epithelial (E)-cadherin, but as we have shown earlier, this OSE can form functional tight junctions (TJs) in culture. Recent gene-expression data on ovarian adenocarcinoma has pointed out a family of TJ proteins, the claudins, to be highly expressed in malignant compared to benign ovarian tumours. The purpose of this study was to investigate the distribution of claudin 1-5 proteins in cultured OSE (n=4), normal ovarian (n=11), benign (n=8), borderline (n=7) and ovarian cancer (n=22) tissues. We found that a weak or absence of expression of claudin 3 and claudin 4 in surface OSE changed to typical cell-border localisation in OSE of inclusion cysts in the normal ovarian stroma. Semiquantitative estimations of immunoblots showed that claudin 3 was significantly increased in ovarian adenocarcinomas compared to benign and borderline-type tumours. Claudin 4 was significantly increased in both borderline-type and ovarian adenocarcinomas compared to benign tumours, whereas no changes were found for claudin 1 or 5. Concerning relation to Federation for International Gynaecology and Obstetrics (FIGO) grade, claudin 3, but not claudin 4, was significantly increased in moderately, poorly and undifferentiated adenocarcinomas compared to well-differentiated and borderline-type tumours. No significant changes were noticed for any claudin with regard to FIGO stages. We conclude that both claudin 3 and 4, even though they differ in expression during ovarian malignant transformation, might be used as novel markers for ovarian tumours. The observations of lack of claudin 4 and low expression of claudin 3 in OSE strengthen our current knowledge about the biological nature of these cells as an undeveloped epithelium.

Antimetastatic gene expression profiles mediated by retinoic acid receptor beta 2 in MDA-MB-435 breast cancer cells

Background

The retinoic acid receptor beta 2 (RARβ2) gene modulates proliferation and survival of cultured human breast cancer cells. Previously we showed that ectopic expression of RARβ2 in a mouse xenograft model prevented metastasis, even in the absence of the ligand, all-trans retinoic acid. We investigated both cultured cells and xenograft tumors in order to delineate the gene expression profiles responsible for an antimetastatic phenotype.

Methods

RNA from MDA-MB-435 human breast cancer cells transduced with RARβ2 or empty retroviral vector (LXSN) was analyzed using Agilent Human 1A Oligo microarrays. The one hundred probes with the greatest differential intensity (p < 0.004, jointly) were determined by selecting the top median log ratios from eight-paired microarrays. Validation of differences in expression was done using Northern blot analysis and quantitative RT-PCR (qRT-PCR). We determined expression of selected genes in xenograft tumors.

Results

RARβ2 cells exhibit gene profiles with overrepresentation of genes from Xq28 (p = 2 × 10^-8), a cytogenetic region that contains a large portion of the cancer/testis antigen gene family. Other functions or factors impacted by the presence of exogenous RARβ2 include mediators of the immune response and transcriptional regulatory mechanisms. Thirteen of fifteen (87%) of the genes evaluated in xenograft tumors were consistent with differences we found in the cell cultures (p = 0.007).

Conclusion

Antimetastatic RARβ2 signalling, direct or indirect, results in an elevation of expression for genes such as tumor-cell antigens (CTAG1 and CTAG2), those involved in innate immune response (e.g., RIG-I/DDX58), and tumor suppressor functions (e.g., TYRP1). Genes whose expression is diminished by RARβ2 signalling include cell adhesion functions (e.g, CD164) nutritional or metabolic processes (e.g., FABP6), and the transcription factor, JUN.

Widespread and nonrandom distribution of DNA palindromes in cancer cells provides a structural platform for subsequent gene amplification

Breakage-fusion-bridge cycles contribute to chromosome instability and generate large DNA palindromes that facilitate gene amplification in human cancers. The prevalence of large DNA palindromes in cancer is not known. Here, by using a new microarray-based approach called genome-wide analysis of palindrome formation, we show that palindromes occur frequently and are widespread in human cancers. Individual tumors seem to have a nonrandom distribution of palindromes in their genomes, and a subset of palindromic loci is associated with gene amplification. This indicates that the location of palindromes in the cancer genome can serve as a structural platform that supports subsequent gene amplification. Genome-wide analysis of palindrome formation is a new approach to identify structural chromosome aberrations associated with cancer.

Increased expression of claudins in cervical squamous intraepithelial neoplasia and invasive carcinoma

Claudins (CLDNs), of which 24 types have been identified, are integral transmembrane proteins of the tight junctions that are critical for maintaining cell adhesion and polarity. They also act as selective barriers. Cells and tissues are characterized by individual CLDN patterns; the composition and levels of expression change during differentiation and tumor formation. Alterations in the expression of individual CLDNs have been detected in several carcinomas and shown to be related to progression and invasion; however, their role in carcinogenesis is controversial. Using a panel of polyclonal (CLDNs 1, 3, and 7) and monoclonal (CLDNs 2 and 4) antibodies, CLDN pattern and expression were studied by immunohistochemistry in 105 cervical tissue specimens, including normal epithelia (n = 20), cervical intraepithelial neoplasias (CINs; CIN 1/2, n = 27; CIN 3, n = 10), carcinoma in situ (CIS, n = 15), and 33 squamous keratinizing and nonkeratinizing invasive carcinomas. No CLDN 3 was observed in normal or intraepithelial neoplastic cells, but significantly increased expression of CLDNs 1, 2, 4, and 7 was detected in the CIN/CIS lesions and invasive carcinomas compared with the normal tissues (P < .001) and reduced reactivity of CLDNs 1 and 2 was observed in invasive cervical cancers compared with CIN 3/CIS (P = .0001) and of CLDNs 2, 4, and 7 compared with CIN 1/2. These results indicate increased expression of CLDNs in the early phase of carcinogenesis in intraepithelial lesions, which decreases during progression to invasive disease. Expression of CLDN 1 was strongest in premalignant stages; thus, it may serve as a good diagnostic marker for the detection of CIN.

Claudin-1, -3 and -4 proteins and mRNA expression in benign and malignant breast lesions: a research study

INTRODUCTION

We compared levels of protein and mRNA expression of three members of the claudin (CLDN) family in malignant breast tumours and benign lesions.

METHODS

Altogether, 56 sections from 52 surgically resected breast specimens were analyzed for CLDN1, CLDN3 and CLDN4 expression by immunohistochemistry. mRNA was also analyzed using real-time PCR in 17 of the 52 cases.

RESULTS

CLDNs were rarely observed exclusively at tight junction structures. CLDN1 was present in the membrane of normal duct cells and in some of the cell membranes from ductal carcinoma in situ, and was frequently observed in eight out of nine areas of apocrine metaplasia, whereas invasive tumours were negative for CLDN1 or it was present in a scattered distribution among such tumour cells (in 36/39 malignant tumours). CLDN3 was present in 49 of the 56 sections and CLDN4 was present in all 56 tissue sections. However, CLDN4 was highly positive in normal epithelial cells and was decreased or absent in 17 out of 21 ductal carcinoma grade 1, in special types of breast carcinoma (mucinous, papillary, tubular) and in areas of apocrine metaplasia. CLDN1 mRNA was downregulated by 12-fold in the sample (tumour) group as compared with the control group using GAPDH as the reference gene. CLDN3 and CLDN4 mRNA exhibited no difference in expression between invasive tumours and surrounding tissue.

CONCLUSIONS

The significant loss of CLDN1 protein in breast cancer cells suggests that CLDN1 may play a role in invasion and metastasis. The loss of CLDN4 expression in areas of apocrine metaplasia and in the majority of grade 1 invasive carcinomas also suggests a particular role for this protein in mammary glandular cell differentiation and carcinogenesis.

The molecular physiology of tight junction pores

Tight junctions form selective barriers that regulate paracellular transport across epithelia. A large family of tetraspanning cell-cell adhesion proteins called claudins create the barrier and regulate electrical resistance, size, and ionic charge selectivity. Study of inherited human claudin diseases and the outcome of the genetic manupulation of claudins in mice, Drosophila, and Caenorhabditis elegans are furthering our understanding of paracellular physiology.

Barriers built on claudins

The fundamental functions of epithelia and endothelia in multicellular organisms are to separate compositionally distinct compartments and regulate the exchange of small solutes and other substances between them. Tight junctions (TJs) between adjacent cells constitute the barrier to the passage of ions and molecules through the paracellular pathway and function as a 'fence' within the plasma membrane to create and maintain apical and basolateral membrane domains. How TJs achieve this is only beginning to be understood. Recently identified components of TJs include the claudins, a family of four-transmembrane-span proteins that are prime candidates for molecules that function in TJ permeability. Their identification and characterization have provided new insight into the diversity of different TJs and heterogeneity of barrier functions in different epithelia and endothelia.

Comparative mapping of human claudin-1 (CLDN1) in great apes

The gene encoding claudin-1 (CLDN1) has been mapped to human chromosome 3 (HSA3; 3q28-->q29) using a radiation hybrid panel. Employing fluorescence in situ hybridization (FISH) we here show that a human P1-derived artificial chromosome (PAC) containing CLDN1 detects the orthologous sites in chromosomes of the great apes, chimpanzee, gorilla, and orangutan. Furthermore, the chromosomal position of CLDN1 was determined in mouse chromosomes by FISH. The position of fluorescent signals is confined to a single chromosomal site in both great apes and mouse and in each case maps to the chromosomal region that has conserved synteny with HSA3 (PTR2q28, GGO2q28, PPY2q38 and MMU16B1). Using a gene-specific probe our results are consistent with reports of the striking similarity of great ape and human genomes as illustrated previously by chromosome painting.

Tight junction-associated proteins (occludin, ZO-1, claudin-1, claudin-4) in squamous cell carcinoma and Bowen's disease

BACKGROUND

The epidermis, which is a typical stratified epithelium, has tight junctions (TJs) in the granular layer, as do simple epithelia. So far, abnormalities of TJs and involvement of claudin-1 have been reported in tumours of simple epithelia.

OBJECTIVES

To examine the expression of TJ-associated proteins (occludin, ZO-1, claudin-1 and claudin-4) in normal human epidermis and in malignant disorders of keratinization.

METHODS

Expression of the proteins in normal human epidermis, five cases of squamous cell carcinoma (SCC) of the skin and five cases of Bowen's disease (BD) was examined by immunofluorescence staining.

RESULTS

In normal human epidermis, occludin, ZO-1 and claudin-4 were expressed at the cell-cell borders in the granular layer specifically or dominantly, whereas claudin-1 was expressed in the whole epithelium. In SCC, occludin, ZO-1, claudin-1 and claudin-4 were strongly expressed in tumour cells with keratinization such as cancer pearls. Claudin-1 was heterogeneously expressed in unkeratinized tumour cells, whereas expression of occludin, ZO-1 and claudin-4 was decreased or absent. In BD, aberrant expression of occludin, ZO-1, claudin-1 and claudin-4 was observed at the cell-cell borders in addition to their expression patterns observed in normal epidermis.

CONCLUSIONS

Expression of occludin, ZO-1 and claudin-4 is associated with keratinization in SCC and BD. However, the heterogeneous expression of claudin-1 in SCC is not determined only by keratinization.

Relevance of breast cancer cell lines as models for breast tumours: an update

The number of available breast cancer cell (BCC) lines is small, and only a very few of them have been extensively studied. Whether they are representative of the tumours from which they originated remains a matter of debate. Whether their diversity mirrors the well-known inter-tumoural heterogeneity is another essential question. While numerous similarities have long been found between cell lines and tumours, recent technical advances, including the use of micro-arrays and comparative genetic analysis, have brought new data to the discussion. This paper presents most of the BCC lines that have been described in some detail to date. It evaluates the accuracy of the few of them widely used (MCF-7, T-47D, BT-474, SK-BR-3, MDA-MB-231, Hs578T) as tumour models. It is concluded that BCC lines are likely to reflect, to a large extent, the features of cancer cells in vivo. The importance of oestrogen receptor-alpha (gene ESR1 ) and Her-2/ neu ( ERBB2 ) as classifiers for cell lines and tumours is underlined. The recourse to a larger set of cell lines is suggested since the exact origin of some of the widely used lines remains ambiguous. Investigations on additional specific lines are expected to improve our knowledge of BCC and of the dialogue that these maintain with their surrounding normal cells in vivo.

Functional crosstalk between Wnt signaling and Cdx-related transcriptional activation in the regulation of the claudin-2 promoter activity

Assembly of tight junctions at the most apical part of the lateral cell membrane is a key event in the differentiation of polarized epithelial cells. Claudin-2, a transmembrane protein involved in tight junction strand formation, has turned out to play a crucial role for the paracellular barrier function by opening pores for small cations. Physiological and pathological variations of epithelial barrier function are accompanied by differential expression of tight junction proteins. Therefore, we characterized molecular mechanisms regulating claudin-2 gene expression. Genomic DNA containing the transcription start point of human claudin-2 was isolated and functionally characterized by reporter gene assays. Activity of the claudin-2 promoter was elevated in mouse mammary epithelial C57 cells expressing Wnt-1. LEF-1, a nuclear effector of the Wnt signaling pathway which is involved in the regulation of cell differentiation and polarization, was found to bind directly to the claudin-2 promoter as revealed by electrophoretic mobility shift assays. Expression of LEF-1 and beta-catenin both enhanced claudin-2 promoter activity. This increase was reduced after mutation of LEF-1 binding sites within the claudin-2 promoter. Furthermore, claudin-2 promoter activity was found to be enhanced by the TCF-4/beta-catenin transcription complex. Therefore, we conclude that gene expression mediated by the promoter of the human tight junction protein claudin-2 is regulated by factors involved in Wnt signaling. Moreover, a functional crosstalk between Wnt signaling and transcriptional activation related to caudal-related homeobox (Cdx) proteins could be demonstrated in the regulation of claudin-2 promoter-mediated gene expression.

Reexpression of the TJ protein CLDN1 induces apoptosis in breast tumor spheroids

Members of the claudin family together with occludin are the major constituents of the tight junction (TJ) complex. The human homologue of the murine CLDN1, previously called SEMP1, was identified by differential expression analysis, and the CLDN1 mRNA was found to be downregulated or completely lost in human breast cancer cells in vitro. Retroviral-induced CLDN1 reexpression in breast cancer cells results in plasma membrane homing of the protein and reconstitution of paracellular flux inhibition, which is not dependent on the presence of occludin protein. In this report, we investigated the physiologic role of CLDN1 in CLDN1-transduced MDA-MB 361 breast tumor cells in adherent 2D and suspension 3D spheroid cell cultures. Retroviral-transduced bulk cultures were FACS-sorted to enrich for 100% CLDN1-positive clonal derivatives with similar expression levels of CLDN1 mRNA and protein. There was no difference in proliferation and cell death characteristics in 2D adherent cell cultures of CLDN1-positive compared to control CLDN1-negative and mock-transduced cell cultures. In contrast, the majority of the CLDN1-transduced derivatives displayed a significant elevation of apoptosis that became evident as early as 2 days after 3D spheroid culture onset. This elevated apoptosis was independent of the volume of established spheroids. The cellular immunofluorescence analysis of CLDN1 protein expression in transduced bulk cultures revealed a CLDN1-positive subfraction with a heterogeneous pattern of membrane and cytosolic immunostaining. In the clonal MDA-MB 361 CLDN1-positive cultures, we found that a more prominent cell membrane localization correlated with a pronounced increase of apoptosis in tumor spheroids. In parallel, inhibition of the paracellular flux rate was observed. These findings support a potential role of the TJ protein CLDN1 in restricting nutrient and growth factor supplies in breast cancer cells, and they indicate that the loss of the cell membrane localization of the TJ protein CLDN1 in carcinomas may be a crucial step during tumor progression.

Gene expression profile analysis of 4-phenylbutyrate treatment of IB3-1 bronchial epithelial cell line demonstrates a major influence on heat-shock proteins

Most individuals with cystic fibrosis (CF) carry one or two mutations that result in a maturation defect of the full-length CFTR protein. The ΔF508 mutation results in a mutant protein that is degraded by the proteosome instead of progressing to the apical membrane where it functions as a cAMP-regulated chloride channel. 4-Phenylbutyrate (PBA) modulates heat-shock protein expression and promotes trafficking of ΔF508, thus permitting maturation and membrane insertion. The goal of this study was to gain insight into the genetic mechanism of PBA action through a large-scale analysis of gene expression. The Affymetrix genome-spanning U133 microarray set was used to compare mRNA expression levels in untreated IB3-1 cell line cultures with cultures treated with 1 mM PBA for 12 and 24 h. The most notable changes in mRNA levels were transient elevations in heat-shock proteins. The majority of genes downregulated throughout the application period were functionally associated with control of gene expression. Another set of genes increased in expression starting at 24 h, suggesting these are downstream effects of altered gene expression initiated by PBA. More than one-third of the genes in this late expressing set were identified as having potential significance in understanding the pathology of CF. Our results demonstrate the usefulness of gene expression profile analysis in understanding the consequences of PBA treatment and provide insights in how this drug exerts its effect on the trafficking of CFTR.

The organization of tight junctions in epithelia: implications for mammary gland biology and breast tumorigenesis

Tight junctions (TJs), the most apical components of the cell-cell junctional complexes, play a crucial role in the establishment and maintenance of cell polarity within tissues. In secretory glandular tissues, such as the mammary gland, TJs are crucial for separating apical and basolateral domains. TJs also create the variable barrier regulating paracellular movement of molecules through epithelial sheets, thereby maintaining tissue homeostasis. Recent advances reveal that TJs exist as macromolecular complexes comprised of several types of membrane proteins, cytoskeletal proteins, and signaling molecules. Many of these components are regulated during mammary gland development and pregnancy cycles, and several have received much attention as possible "tumor suppressors" during progression to breast cancer.