The cadherin-catenin system: implications for growth and differentiation of endocrine tissues

Recent advances of therapeutic targets based on the molecular signature in breast cancer: genetic mutations and implications for current treatment paradigms

Breast cancer is the most common malignancy in women all over the world. Genetic background of women contributes to her risk of having breast cancer. Certain inherited DNA mutations can dramatically increase the risk of developing certain cancers and are responsible for many of the cancers that run in some families. Regarding the widespread multigene panels, whole exome sequencing is capable of providing the evaluation of genetic function mutations for development novel strategy in clinical trials. Targeting the mutant proteins involved in breast cancer can be an effective therapeutic approach for developing novel drugs. This systematic review discusses gene mutations linked to breast cancer, focusing on signaling pathways that are being targeted with investigational therapeutic strategies, where clinical trials could be potentially initiated in the future are being highlighted.

Role of N-cadherin in proliferation, migration, and invasion of germ cell tumours

Germ cell tumors (GCTs) are the most common malignancies in young men. Most patients with GCT can be cured with cisplatin-based combination chemotherapy, even in metastatic disease. In case of therapy resistance, prognosis is usually poor. We investigated the potential of N-cadherin inhibition as a therapeutic strategy. We analyzed the GCT cell lines NCCIT, NTERA-2, TCam-2, and the cisplatin-resistant sublines NCCIT-R and NTERA-2R. Effects of a blocking antibody or siRNA against N-cadherin on proliferation, migration, and invasion were investigated. Mouse xenografts of GCT cell lines were analyzed by immunohistochemistry for N-cadherin expression. All investigated GCT cell lines were found to express N-cadherin protein in vitro and in vivo. Downregulation of N-cadherin in vitro leads to a significant inhibition of proliferation, migration, and invasion. N-cadherin-downregulation leads to a significantly higher level of pERK. N-cadherin-inhibition resulted in significantly higher rates of apoptotic cells in caspase-3 staining. Expression of N-cadherin is preserved in cisplatin-resistant GCT cells, pointing to an important physiological role in cell survival. N-cadherin-downregulation results in a significant decrease of proliferation, migration, and invasion and stimulates apoptosis in cisplatin-naive and resistant GCT cell lines. Therefore, targeting N-cadherin may be a promising therapeutic approach, particularly in cisplatin-resistant, therapy refractory and metastatic GCT.

Investigation of N-cadherin/β-catenin expression in adrenocortical tumors

β-catenin is a multifunctional protein; it is a key component of the Wnt signaling, and it plays a central role in cadherin-based adhesions. Cadherin loss promotes tumorigenesis by releasing membrane-bound β-catenin, hence stimulating Wnt signaling. Cadherins seem to be involved in tumor development, but these findings are limited in adrenocortical tumors (ACTs). The objective of this study was to evaluate alterations in key components of cadherin/catenin adhesion system and of Wnt pathway. This study included eight normal adrenal samples (NA) and 95 ACT: 24 adrenocortical carcinomas (ACCs) and 71 adrenocortical adenomas (ACAs). β-catenin mutations were evaluated by sequencing, and β-catenin and cadherin (E-cadherin and N-cadherin) expression was analyzed by quantitative reverse transcription PCR (qRT-PCR) and by immunohistochemistry (IHC). We identified 18 genetic alterations in β-catenin gene. qRT-PCR showed overexpression of β-catenin in 50 % of ACC (12/24) and in 48 % of ACA (21/44). IHC data were in accordance with qRT-PCR results: 47 % of ACC (7/15) and 33 % of ACA (11/33) showed increased cytoplasmic or nuclear β-catenin accumulation. N-cadherin downregulation has been found in 83 % of ACC (20/24) and in 59 % of ACA (26/44). Similar results were obtained by IHC: N-cadherin downregulation was observed in 100 % (15/15) of ACC and in 55 % (18/33) of ACA. β-catenin overexpression together with the aberrant expression of N-cadherin may play important role in ACT tumorigenesis. The study of differentially expressed genes (such as N-cadherin and β-catenin) may enhance our understanding of the biology of ACT and may contribute to the discovery of new diagnostic and prognostic tools.

SATB1 overexpression regulates the development and progression in bladder cancer through EMT

The global gene regulator Special AT-rich sequence-binding protein-1 (SATB1) has been reported to induce EMT-like changes and be associated with poor clinical outcome in several cancers. This study aims to evaluate whether SATB1 affects the biological behaviors of bladder transitional cell carcinoma (BTCC) and further elucidate if this effect works through an epithelial-mesenchymal transition (EMT) pathway. The expression of SATB1, E-cadherin (epithelial markers), vimentin (mesenchymal markers) in BTCC tissues and adjacent noncancerous tissues, as well as in two cell lines of bladder cancer were investigated. Whether the SATB1 expression is associated with clinicopathological factors or not was statistically analyzed. Cell invasion and migration, cell cycle, cell proliferation and apoptosis were evaluated in SATB1 knockdown and overexpressed cell lines. Our results showed that the expression of SATB1 was remarkably up-regulated both in BTCC tissues and in bladder cancer cell lines with high potential of metastasis. The results were also associated with EMT markers and poor prognosis of BTCC patients. Moreover, SATB1 induced EMT processes through downregulation of E-cadherin, upregulation of E-cadherin repressors (Snail, Slug and vimentin). SATB1 also promoted cell cycle progression, cell proliferation, cell invasion and cell migration, but did not alter cell survival. In conclusion, our results suggest that SATB1 plays a crucial role in the progression of bladder cancer by regulating genes controlling EMT processes. Further, it may be a novel therapeutic target for aggressive bladder cancers.

Genome-wide DNA methylation profiles and their relationships with mRNA and the microRNA transcriptome in bovine muscle tissue (Bos taurine)

DNA methylation is a key epigenetic modification in mammals and plays important roles in muscle development. We sampled longissimus dorsi muscle (LDM) from a well-known elite native breed of Chinese Qinchuan cattle living within the same environment but displaying distinct skeletal muscle at the fetal and adult stages. We generated and provided a genome-wide landscape of DNA methylomes and their relationship with mRNA and miRNA for fetal and adult muscle studies. Integration analysis revealed a total of 77 and 1,054 negatively correlated genes with methylation in the promoter and gene body regions, respectively, in both the fetal and adult bovine libraries. Furthermore, we identified expression patterns of high-read genes that exhibit a negative correlation between methylation and expression from nine different tissues at multiple developmental stages of bovine muscle-related tissue or organs. In addition, we validated the MeDIP-Seq results by bisulfite sequencing PCR (BSP) in some of the differentially methylated promoters. Together, these results provide valuable data for future biomedical research and genomic and epigenomic studies of bovine skeletal muscle that may help uncover the molecular basis underlying economically valuable traits in cattle. This comprehensive map also provides a solid basis for exploring the epigenetic mechanisms of muscle growth and development.

Expression of SATB1 promotes the growth and metastasis of colorectal cancer

Special AT-rich sequence-binding protein-1 (SATB1) has been identified as a genome organizer that reprograms chromatin organization and transcription profiles. SATB1 promotes tumor growth and metastasis in breast cancer and is associated with poor prognosis in several cancer types. The association between SATB1 and colorectal cancer (CRC) has not been studied intensively. Therefore, this study aimed to investigate the effect of SATB1 on CRC growth and metastasis in vitro and in vivo and its correlation with overall survival and clinicopathological factors in CRC patients. Stable SATB1 knockdown and SATB1-overexpressing cell lines were established. SATB1 knockdown decreased cell growth, colony formation, migration, and invasion and increased apoptosis in CRC cells in vitro (p<0.05), whereas SATB1 overexpression had the opposite effect. SATB1 overexpression increased tumor growth and metastasis to lung and liver in vivo by using xenograft animal models (p<0.05). Thus, SATB1 promoted an aggressive CRC phenotype in vitro and in vivo. Immunohistochemical analysis of 560 CRC specimens showed that SATB1 expression was significantly higher in CRC tissues than in matched non-tumor mucosa (p<0.001). In addition, SATB1 expression was significantly higher in patients with poorly differentiated tumors, higher invasion depth, distant metastasis, and advanced TNM stage. SATB1-positive patients had a poorer prognosis than SATB1-negative patients, and SATB1 was identified as an independent prognostic factor for CRC (p = 0.009). Strikingly, we also evaluated SATB2 expression in CRC and found that SATB2 was more abundantly expressed in non-cancerous mucosa compared to colorectal cancer tissues (p<0.001). However, SATB2 expression had no influence on prognosis of CRC patients (p = 0.836). SATB1 expression was significantly associated with shorter survival time either in SATB2-positive patients or in SATB2-negative patients (p<0.001). In conclusion, our findings indicated an important role for SATB1 in CRC tumorigenesis and metastasis. Therefore, SATB1 may represent an important prognostic biomarker and therapeutic target for CRC.

Establishment of new clonal pancreatic β-cell lines (MIN6-K) useful for study of incretin/cyclic adenosine monophosphate signaling

Incretin/cyclic adenosine monophosphate (cAMP) signaling is critical for potentiation of insulin secretion. Although several cell lines of pancreatic β‐cells are currently available, there are no cell lines suitable for investigation of incretin/cAMP signaling. In the present study, we have newly established pancreatic β‐cell lines (named MIN6‐K) from the IT6 mouse, which develops insulinoma. MIN6‐K8 cells respond to both glucose and incretins, such as glucagon‐like peptide‐1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP), as is the case in pancreatic islets, whereas MIN6‐K20 cells respond to glucose, but not to incretins. Despite the difference in incretin‐potentiated insulin secretion between these two cell lines, the accumulation of cAMP after stimulation of GLP‐1 is comparable in these cells. Interestingly, we also found that incretin responsiveness is drastically induced by the formation of pseudoislets from MIN6‐K20 cells to a level comparable to that of pancreatic islets. Thus, these cell lines are useful for studying incretin/cAMP signaling in β‐cells. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00026.x, 2010)

Comparison of the genome-wide DNA methylation profiles between fast-growing and slow-growing broilers

INTRODUCTION

Growth traits are important in poultry production, however, little is known for its regulatory mechanism at epigenetic level. Therefore, in this study, we aim to compare DNA methylation profiles between fast- and slow-growing broilers in order to identify candidate genes for chicken growth. Methylated DNA immunoprecipitation-sequencing (MeDIP-seq) was used to investigate the genome-wide DNA methylation pattern in high and low tails of Recessive White Rock (WRR(h); WRR(l)) and that of Xinhua Chickens (XH(h); XH(l)) at 7 weeks of age. The results showed that the average methylation density was the lowest in CGIs followed by promoters. Within the gene body, the methylation density of introns was higher than that of UTRs and exons. Moreover, different methylation levels were observed in different repeat types with the highest in LINE/CR1. Methylated CGIs were prominently distributed in the intergenic regions and were enriched in the size ranging 200-300 bp. In total 13,294 methylated genes were found in four samples, including 4,085 differentially methylated genes of WRR(h) Vs. WRR(l), 5,599 of XH(h) Vs. XH(l), 4,204 of WRR(h) Vs. XH(h), as well as 7,301 of WRR(l) Vs. XH(l). Moreover, 132 differentially methylated genes related to growth and metabolism were observed in both inner contrasts (WRR(h) Vs. WRR(l) and XH(h) Vs. XH(l)), whereas 129 differentially methylated genes related to growth and metabolism were found in both across-breed contrasts (WRR(h) Vs. XH(h) and WRR(l) Vs. XH(l)). Further analysis showed that overall 75 genes exhibited altered DNA methylation in all four contrasts, which included some well-known growth factors of IGF1R, FGF12, FGF14, FGF18, FGFR2, and FGFR3. In addition, we validate the MeDIP-seq results by bisulfite sequencing in some regions.

CONCLUSIONS

This study revealed the global DNA methylation pattern of chicken muscle, and identified candidate genes that potentially regulate muscle development at 7 weeks of age at methylation level.

N-cadherin expression in malignant germ cell tumours of the testis

BACKGROUND

Testicular germ cell tumours (TGCTs) are the most common malignancy in young men aged 18-35 years. They are clinically and histologically subdivided into seminomas and non-seminomas. Cadherins are calcium-dependent transmembrane proteins of the group of adhesion proteins. They play a role in the stabilization of cell-cell contacts, the embryonic morphogenesis, in the maintenance of cell polarity and signal transduction. N-cadherin (CDH2), the neuronal cadherin, stimulates cell-cell contacts during migration and invasion of cells and is able to suppress tumour cell growth.

METHODS

Tumour tissues were acquired from 113 male patients and investigated by immunohistochemistry, as were the three TGCT cell lines NCCIT, NTERA-2 and Tcam2. A monoclonal antibody against N-cadherin was used.

RESULTS

Tumour-free testis and intratubular germ cell neoplasias (unclassified) (IGCNU) strongly expressed N-cadherin within the cytoplasm. In all seminomas investigated, N-cadherin expression displayed a membrane-bound location. In addition, the teratomas and yolk sac tumours investigated also differentially expressed N-cadherin. In contrast, no N-cadherin could be detected in any of the embryonal carcinomas and chorionic carcinomas examined. This expression pattern was also seen in the investigated mixed tumours consisting of seminomas, teratomas, and embryonal carcinoma.

CONCLUSIONS

N-cadherin expression can be used to differentiate embryonal carcinomas and chorionic carcinomas from other histological subtypes of TGCT.

N-cadherin is differentially expressed in histological subtypes of papillary renal cell carcinoma

Background

Papillary renal cell carcinoma (RCC) represents a rare tumor, which is divided, based on histological criteria, into two subtypes. In contrast to type I papillary RCC type II papillary RCC shows a worse prognosis. So far, reliable immunohistochemical markers for the distinction of these subtypes are not available.

Methods

In the present study the expression of N(neural)-, E(epithelial)-, P(placental)-, und KSP(kidney specific)-cadherin was examined in 22 papillary RCC of histological type I and 18 papillary RCC of histological type II (n = 40).

Results

All papillary RCC type II displayed a membranous expression for N-cadherin, whereas type I did not show any membranous positivity for N-cadherin. E-cadherin exhibited a stronger, but not significant, membranous as well as cytoplasmic expression in type II than in type I papillary RCC. A diagnostic relevant expression of P- and KSP-cadherin could not be demonstrated in both tumor entities.

Conclusion

Thus N-cadherin represents the first immunhistochemical marker for a clear cut differentiation between papillary RCC type I and type II and could be a target for therapy and diagnostic in the future.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2011556982761733

Molecular Interactions between MUC1 Epithelial Mucin, β-Catenin, and CagA Proteins

Interleukin (IL)-8-driven neutrophil infiltration of the gastric mucosa is pathognomonic of persistent Helicobacter pylori infection. Our prior study showed that ectopic over-expression of MUC1 in human AGS gastric epithelial cells reduced H. pylori-stimulated IL-8 production compared with cells expressing MUC1 endogenously. Conversely, Muc1 knockout (Muc1(-/-)) mice displayed an increased level of transcripts encoding the keratinocyte chemoattractant (KC), the murine equivalent of human IL-8, in gastric mucosa compared with Muc1(+/+) mice during experimental H. pylori infection. The current study tested the hypothesis that a decreased IL-8 level observed following MUC1 over-expression is mediated through the ability of MUC1 to associate with β-catenin, thereby inhibiting H. pylori-induced β-catenin nuclear translocation. Increased neutrophil infiltration of the gastric mucosa of H. pylori-infected Muc1(-/-) mice was observed compared with Muc1(+/+) wild type littermates, thus defining the functional consequences of increased KC expression in the Muc1-null animals. Protein co-immunoprecipitation (co-IP) studies using lysates of untreated or H. pylori-treated AGS cells demonstrated that (a) MUC1 formed a co-IP complex with β-catenin and CagA, (b) MUC1 over-expression reduced CagA/β-catenin co-IP, and (c) in the absence of MUC1 over-expression, H. pylori infection increased the nuclear level of β-catenin, (d) whereas MUC1 over-expression decreased bacteria-driven β-catenin nuclear localization. These results suggest that manipulation of MUC1 expression in gastric epithelia may be an effective therapeutic strategy to inhibit H. pylori-dependent IL-8 production, neutrophil infiltration, and stomach inflammation.

Prognostic gene signatures for patient stratification in breast cancer: accuracy, stability and interpretability of gene selection approaches using prior knowledge on protein-protein interactions

Background

Stratification of patients according to their clinical prognosis is a desirable goal in cancer treatment in order to achieve a better personalized medicine. Reliable predictions on the basis of gene signatures could support medical doctors on selecting the right therapeutic strategy. However, during the last years the low reproducibility of many published gene signatures has been criticized. It has been suggested that incorporation of network or pathway information into prognostic biomarker discovery could improve prediction performance. In the meanwhile a large number of different approaches have been suggested for the same purpose.

Methods

We found that on average incorporation of pathway information or protein interaction data did not significantly enhance prediction performance, but indeed greatly interpretability of gene signatures. Some methods (specifically network-based SVMs) could greatly enhance gene selection stability, but revealed only a comparably low prediction accuracy, whereas Reweighted Recursive Feature Elimination (RRFE) and average pathway expression led to very clearly interpretable signatures. In addition, average pathway expression, together with elastic net SVMs, showed the highest prediction performance here.

Results

The results indicated that no single algorithm to perform best with respect to all three categories in our study. Incorporating network of prior knowledge into gene selection methods in general did not significantly improve classification accuracy, but greatly interpretability of gene signatures compared to classical algorithms.

Epithelial to mesenchymal transition of mesothelial cells in tuberculous pleurisy

PURPOSE

Tuberculous pleurisy is the most frequent extrapulmonary manifestation of tuberculosis. In spite of adequate treatment, pleural fibrosis is a common complication, but the mechanism has not been elucidated. This study is to determine whether epithelial to mesenchymal transition (EMT) of mesothelial cells occurs in tuberculous pleurisy.

MATERIALS AND METHODS

Normal pleural mesothelial cells, isolated from irrigation fluids during operations for primary spontaneous pneumothorax, were characterized by immunofluorescence and reverse transcription polymerase chain reaction (RT-PCR). These cells were treated in vitro with various cytokines, which were produced in the effluents of tuberculous pleurisy. The isolated cells from the effluents of tuberculous pleurisy were analyzed by immunofluorescence and RT-PCR analysis.

RESULTS

The isolated cells from the irrigation fluid of primary spontaneous pneumothorax had epithelial characteristics. These cells, with transforming growth factor-β1 and/or interleukin-1β treatment, underwent phenotypic transition from epithelial to mesenchymal cells, with the loss of epithelial morphology and reduction in cytokeratin and E-cadherin expression. Effluent analysis from tuberculous pleurisy using immunofluorescence and RT-PCR demonstrated two phenotypes that showed mesenchymal characteristics and both epithelial & mesencymal characteristics.

CONCLUSION

Our results suggest that pleural mesothelial cells in tuberculous pleurisy have been implicated in pleural fibrosis through EMT.

Role of neural-cadherin in early osteoblastic differentiation of human bone marrow stromal cells cocultured with human umbilical vein endothelial cells

In our previous studies, roles of gap junction and vascular endothelial growth factor in the cross-talking of human bone marrow stromal cells (HBMSCs) and human umbilical vein endothelial cells (HUVECs) have been extensively studied. The present study focused on the investigation of the roles of neural (N)-cadherin in early differentiation of HBMSCs in direct-contact cocultures with HUVECs for 24 and 48 h. Quantitative real-time polymerase chain reaction, immunofluorescence, Western blot, as well as functional studies were applied to perform the studies at both protein and gene levels. Results showed that cocultured cells expressed much higher N-cadherin than monocultured cells after 24 and 48 h of culture. We observed that N-cadherin concentrated in the membrane of cocultured HBMSCs (co-HBMSCs) while distributed within the cytoplasm of monocultured HBMSCs, which indicated that the cell-cell adhesion was improved between cocultured cells. In addition, more beta-catenin was found to translocate into the cocultured cells nuclei and more T cell factor-1 (TCF-1) were detected in cocultured cells than in the monocultured cells. Moreover, mRNA levels of early osteoblastic markers including alkaline phosphatase (ALP) and type I collagen (Col-I) of co-HBMSCs were significantly upregulated, whereas neutralization of N-cadherin led to a downregulation of ALP and Col-I in both of the HBMSCs and co-HBMSCs compared with untreated cells. Taking our findings together it can be concluded that cocultures of HBMSCs with HUVECs increased N-cadherin expression and improved cell-cell adhesion. Whether this applies only to osteoprogenitor cells or to all the cell types in the culture will need to be determined by further studies. Subsequently, signaling transduction might be induced with the participation of beta-catenin and TCF-1. With the N-cadherin-mediated cell-cell adhesion and signaling transductions, the early osteoblastic differentiation of co-HBMSCs was significantly upregulated.

The expression of E-cadherin in somatotroph pituitary adenomas is related to tumor size, invasiveness, and somatostatin analog response

CONTEXT

Appropriate cell-to-cell adhesion is fundamental for the epithelial phenotype of pituitary cells. Loss of the adhesion protein E-cadherin has been associated with invasiveness, metastasis, and poor prognosis in cancers of epithelial origin. In somatotroph adenomas, a variable and reduced expression of E-cadherin has been demonstrated. In addition, nuclear translocation of E-cadherin was found to correlate with pituitary tumor invasion.

OBJECTIVE

The objective was to examine the protein expression of E-cadherin in somatotroph pituitary adenomas in relation to adenoma size, invasiveness, and somatostatin analog (SMS) efficacy.

PATIENTS AND METHODS

Eighty-three patients were included, and 29 were treated preoperatively with SMS. Adenoma E-cadherin protein expression was analyzed by Western blot (61 patients) and immunohistochemistry (IHC) (80 patients) with antibodies directed against both extracellular and intracellular domains (IHC). The acute (direct surgery group) and long-term (preoperatively treated group) SMS responses were evaluated. Baseline tumor volume and invasiveness were measured on magnetic resonance imaging scans.

RESULTS

Membranous E-cadherin was lost in several adenomas. Nine of these were nuclear E-cadherin positive. The E-cadherin protein expression correlated negatively to tumor size and positively to acute SMS response. Low E-cadherin levels (preoperatively treated group only) and loss of membranous E-cadherin correlated to tumor invasiveness. The E-cadherin level correlated positively to tumor reduction after SMS treatment, and adenomas with nuclear E-cadherin staining had lower IGF-I reduction and tumor shrinkage. Preoperatively treated adenomas had reduced E-cadherin protein levels, but the IHC expression was unaltered.

CONCLUSION

Reduced E-cadherin expression may correlate to a dedifferentiated phenotype in the somatotroph pituitary adenomas.

Effect of E-cadherin expression on hormone production in rat anterior pituitary lactotrophs in vitro

Cadherins are a family of transmembrane glycoproteins that mediate cell-to-cell adhesion. A change in cadherin type in cells, i.e., cadherin switching, induces changes in the character of the cell. Recent studies of the developing rat adenohypophysis found that primordial cells co-expressed E- and N-cadherins, but that hormone-producing cells lost E-cadherin and ultimately possessed only N-cadherin. In the present study, we examined the roles of cadherin switching in cytogenesis of anterior pituitary cells by observing prolactin mRNA and protein expression in lactotrophs that were transformed with an E-cadherin expression vector. In hormone-producing cells that were transfected with a pIRES2-ZsGreen1 plasmid with a full-length E-cadherin cDNA (rE-cad-IZ) insert in primary culture, we detected E- and N-cadherins on plasma membrane and E-cadherin in cytoplasm. In these rE-cad-IZ-transfected cells, in situ hybridization revealed prolactin mRNA signals that were at a level identical to that in control cells, while prolactin protein was barely detectable using immunocytochemistry. The mean signal intensity of prolactin protein in rE-cad-IZ-transfected cells was approximately one fourth that in intact cells and in null-IZ-transfected cells (P<0.01). These results suggest that the expression of E-cadherin does not affect prolactin mRNA transcription; rather, it reduces prolactin protein content, presumably by affecting trafficking of secretory granules.

Cell surface and secreted protein profiles of human thyroid cancer cell lines reveal distinct glycoprotein patterns

Cell surface proteins have been shown to be effective therapeutic targets. In addition, shed forms of these proteins and secreted proteins can serve as biomarkers for diseases, including cancer. Thus, identification of cell surface and secreted proteins has been a prime area of interest in the proteomics field. Most cell surface and secreted proteins are known to be glycosylated, and therefore, a proteomics strategy targeting these proteins was applied to obtain proteomic profiles from various thyroid cancer cell lines that represent the range of thyroid cancers of follicular cell origin. In this study, we oxidized the carbohydrates of secreted proteins and those on the cell surface with periodate and isolated them via covalent coupling to hydrazide resin. The glycoproteins obtained were identified from tryptic peptides and N-linked glycopeptides released from the hydrazide resin using two-dimensional liquid chromatography-tandem mass spectrometry in combination with the gas phase fractionation. Thyroid cancer cell lines derived from papillary thyroid cancer (TPC-1), follicular thyroid cancer (FTC-133), Hurthle cell carcinoma (XTC-1), and anaplastic thyroid cancer (ARO and DRO-1) were evaluated. An average of 150 glycoproteins were identified per cell line, of which more than 57% are known cell surface or secreted glycoproteins. The usefulness of the approach for identifying thyroid cancer associated biomarkers was validated by the identification of glycoproteins (e.g., CD44, galectin 3 and metalloproteinase inhibitor 1) that have been found to be useful markers for thyroid cancer. In addition to glycoproteins that are commonly expressed by all of the cell lines, we identified others that are only expressed in the more well-differentiated thyroid cancer cell lines (follicular, Hurthle cell and papillary), or by cell lines derived from undifferentiated tumors that are uniformly fatal forms of thyroid cancer (i.e., anaplastic). On the basis of the results obtained, a set of glycoprotein biomarker candidates for thyroid cancer is proposed.

Functional characterization of E- and P-cadherin in invasive breast cancer cells

Background

Alterations in the cadherin-catenin adhesion complexes are involved in tumor initiation, progression and metastasis. However, the functional implication of distinct cadherin types in breast cancer biology is still poorly understood.

Methods

To compare the functional role of E-cadherin and P-cadherin in invasive breast cancer, we stably transfected these molecules into the MDA-MB-231 cell line, and investigated their effects on motility, invasion and gene expression regulation.

Results

Expression of either E- and P-cadherin significantly increased cell aggregation and induced a switch from fibroblastic to epithelial morphology. Although expression of these cadherins did not completely reverse the mesenchymal phenotype of MDA-MB-231 cells, both E- and P-cadherin decreased fibroblast-like migration and invasion through extracellular matrix in a similar way. Moreover, microarray gene expression analysis of MDA-MB-231 cells after expression of E- and P-cadherins revealed that these molecules can activate signaling pathways leading to significant changes in gene expression. Although the expression patterns induced by E- and P-cadherin showed more similarities than differences, 40 genes were differentially modified by the expression of either cadherin type.

Conclusion

E- and P-cadherin have similar functional consequences on the phenotype and invasive behavior of MDA-MB-231 cells. Moreover, we demonstrate for the first time that these cadherins can induce both common and specific gene expression programs on invasive breast cancer cells. Importantly, these identified genes are potential targets for future studies on the functional consequences of altered cadherin expression in human breast cancer.

RET/PTC1-driven neoplastic transformation and proinvasive phenotype of human thyrocytes involve Met induction and beta-catenin nuclear translocation

Activation of the RET gene by chromosomal rearrangements generating RET/PTC oncogenes is a frequent, early, and causative event in papillary thyroid carcinoma (PTC). We have previously shown that, in human primary thyrocytes, RET/PTC1 induces a transcriptional program including the MET proto-oncogene. In PTCs, beta-catenin is frequently mislocated to the cytoplasm nucleus. We investigated the interplay between Ret/ptc1 signaling and Met in regulating the proinvasive phenotype and beta-catenin localization in cellular models of human PTC. Here, we show that Met protein is expressed and is constitutively active in human thyrocytes exogenously expressing RET/PTC1 as well as a mutant (Y451F) devoid of the main Ret/ptc1 multidocking site. Both in transformed thyrocytes and in the human PTC cell line TPC-1, Ret/ptc1-Y451-dependent signaling and Met cooperated to promote a proinvasive phenotype. Accordingly, gene/functional silencing of either RET/PTC1 or MET abrogated early branching morphogenesis in TPC-1 cells. The same effect was obtained by blocking the common downstream effector Akt. Y451 of Ret/ptc1 was required to promote proliferation and nuclear translocation of beta-catenin, suggesting that these oncogene-driven effects are Met-independent. Pharmacologic inhibition of Ret/ptc1 and Met tyrosine kinases by the multitarget small molecule RPI-1 blocked cell proliferation and invasive ability and dislocated beta-catenin from the nucleus. Altogether, these results support that Ret/ptc1 cross talks with Met at transcriptional and signaling levels and promotes beta-catenin transcriptional activity to drive thyrocyte neoplastic transformation. Such molecular network, promoting disease initiation and acquisition of a proinvasive phenotype, highlights new options to design multitarget therapeutic strategies for PTCs.

Caveolin-1: an ambiguous partner in cell signalling and cancer

Caveolae are small plasma membrane invaginations that have been implicated in a variety of functions including transcytosis, potocytosis and cholesterol transport and signal transduction. The major protein component of this compartment is a family of proteins called caveolins. Experimental data obtained in knockout mice have provided unequivocal evidence for a requirement of caveolins to generate morphologically detectable caveolae structures. However, expression of caveolins is not sufficient per seto assure the presence of these structures. With respect to other roles attributed to caveolins in the regulation of cellular function, insights are even less clear. Here we will consider, more specifically, the data concerning the ambiguous roles ascribed to caveolin-1 in signal transduction and cancer. In particular, evidence indicating that caveolin-1 function is cell context dependent will be discussed.

Role of cadherin-mediated cell-cell adhesion in pancreatic exocrine-to-endocrine transdifferentiation

Although pancreatic exocrine acinar cells have the potential to transdifferentiate into pancreatic endocrine cells, the mechanisms are poorly understood. Here we report that intracellular signaling pathways, including those involving MAPK and phosphatidylinositol 3 (PI3)-kinase, are activated by enzymatic dissociation of pancreatic acinar cells and that spherical cell clusters are formed by cadherin-mediated cell-cell adhesion during transdifferentiation. Inhibition of PI3-kinase by LY294002 prevents spheroid formation by degrading E-cadherin and beta-catenin, blocking transdifferentiation into insulin-secreting cells. In addition, neutralizing antibody against E-cadherin suppresses the induction of genes characteristic of pancreatic beta-cells. We also show that loss of cadherin-mediated cell-cell adhesion induces and maintains a dedifferentiated state in isolated pancreatic acinar cells. Thus, disruption and remodeling of cadherin-mediated cell-cell adhesion is critical in pancreatic exocrine-to-endocrine transdifferentiation, in which the PI3-kinase pathway plays an essential role.

Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1alpha) upregulated E-cadherin expression in HepG2 cells

Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1alpha), a highly inducible transcriptional coactivator regulating energy homeostasis, is down-regulated in hepatoma tissues. To dissect its role in hepato-tumorigenesis, Ingenuity Pathway Analysis was applied to construct pathways affected by PGC-1alpha upregulation in HepG2 hepatoma cells based on our microarray data. Interestingly, migration of these cells was markedly diminished by PGC-1alpha overexpression in consistency with Ingenuity results. Moreover, a deduced expression increase of E-cadherin was also observed in PGC-1alpha-overexpressing HepG2 cells. Finally, transient transfection and chromatin-immunoprecipitation assays suggested that increased histone acetylation might be responsible for PGC-1alpha-mediated transactivation of a minimal E-cadherin promoter.

Hormonal heterogeneity of endometrial cancer

Endometrial cancer is the most common malignant tumor of the female genital tract in the developed world. Increasing evidence suggests that the majority of cases can be divided into two different types ofendometrial cancer based on clinico-pathological and molecular characteristics. Type I is associated with an endocrine milieu of estrogen predominance. These tumors are ofendometroid histology and develop from endometrial hyperplasia. They have good prognosis and are sensitive to endocrine treatment. Type II endometrial cancers are not associated with a history of unopposed estrogens and develop from the atrophic endometrium of elderly women. Mainly, they are of serous papillary or clear cell morphology, have a poor prognosis and do not react to endocrine treatment. Both types of endometrial cancer probably differ markedly with regard to the molecular mechanisms of transformation. The transition from normal endometrium to a malignant tumor is thought to involve a stepwise accumulation of alterations in cellular mechanisms leading to dysfunctional cell growth. This chapter reviews the current knowledge of the molecular mechanisms commonly associated with development of type I and type II endometrial cancer.

Transforming growth factor beta1 induces epithelial-to-mesenchymal transition of A549 cells

Idiopathic pulmonary fibrosis (IPF) comprises an aggregate of mesenchymal cells. However, the cellular origin of these mesenchymal phenotypes remains unclear. Transforming growth factor beta1 (TGF-beta1) has been known as the main cytokine involved in the pathogenesis of IPF. We examined whether the potent fibrogenic cytokine TGF-beta1 could induce the epithelial-to-mesenchymal transition (EMT) in the human alveolar epithelial cell line, A549, and determined whether snail expression is associated with the phenotypic changes observed in the A549 cells. EMT was investigated with cells morphology changes under phase-contrast microscopy, western blotting, and indirect immunofluorescence stains. E-cadherin and transcription factor, snail, were also evaluated by measuring mRNA levels using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. The data showed that TGF-beta1 induced A549 cells with epithelial cell characteristics to undergo EMT in a concentration-dependent manner. Following TGF-beta1 treatment, A549 cells induced EMT characterized by cells morphological changes, loss of epithelial markers Ecaherin and cytokeratin, increased stress fiber reorganization by F-actin, and cytokeratin replacement by vimentin. Although IL-1beta failed to induce A549 cells to undergo EMT, the combination of TGF-beta1 and IL-1beta showed synergy effects in cells morphology changes and the expression of mesenchymal markers. The snail expression study using RT-PCR analysis provided that loss of E-cadherin expression was associated with snail expression. Stimulation of A54 cells with TGF-beta1 plus IL-1beta revealed a higher level of snail expression. Our data showed that EMT of A549 cells might be closely associated with snail expression.

E-cadherin is required for caveolin-1-mediated down-regulation of the inhibitor of apoptosis protein survivin via reduced beta-catenin-Tcf/Lef-dependent transcription

Caveolin-1 reportedly acts as a tumor suppressor and promotes events associated with tumor progression, including metastasis. The molecular mechanisms underlying such radical differences in function are not understood. Recently, we showed that caveolin-1 inhibits expression of the inhibitor of apoptosis protein survivin via a transcriptional mechanism involving the beta-catenin-Tcf/Lef pathway. Surprisingly, while caveolin-1 expression decreased survivin mRNA and protein levels in HT29(ATCC) human colon cancer cells, this was not the case in metastatic HT29(US) cells. Survivin down-regulation was paralleled by coimmunoprecipitation and colocalization of caveolin-1 with beta-catenin in HT29(ATCC) but not HT29(US) cells. Unlike HT29(ATCC) cells, HT29(US) cells expressed small amounts of E-cadherin that accumulated in intracellular patches rather than at the cell surface. Re-expression of E-cadherin in HT29(US) cells restored the ability of caveolin-1 to down-regulate beta-catenin-Tcf/Lef-dependent transcription and survivin expression, as seen in HT29(ATCC) cells. In addition, coimmunoprecipitation and colocalization between caveolin-1 and beta-catenin increased upon E-cadherin expression in HT29(US) cells. In human embryonic kidney HEK293T and HT29(US) cells, caveolin-1 and E-cadherin cooperated in suppressing beta-catenin-Tcf/Lef-dependent transcription as well as survivin expression. Finally, mouse melanoma B16-F10 cells, another metastatic cell model with low endogenous caveolin-1 and E-cadherin levels, were characterized. In these cells, caveolin-1-mediated down-regulation of survivin in the presence of E-cadherin coincided with increased apoptosis. Thus, the absence of E-cadherin severely compromises the ability of caveolin-1 to develop activities potentially relevant to its role as a tumor suppressor.

MUC1 inhibits cell proliferation by a beta-catenin-dependent mechanism

beta-Catenin binds to the cytoplasmic region of the type 1 membrane glycoprotein MUC1. In the current study, we utilized HEK293T cells expressing the full-length MUC1 protein, or a CD8/MUC1 fusion protein containing only the MUC1 cytoplasmic tail, to investigate the effects of beta-catenin binding to MUC1 on downstream beta-catenin-dependent events. Compared with HEK293T cells transfected with empty vector or CD8 alone, expression of the MUC1 cytoplasmic tail inhibited beta-catenin binding to E-cadherin, decreased translocation of beta-catenin into the nucleus, reduced activation of the LEF-1 transcription factor, and blocked expression of the cyclin D1 and c-Myc proteins. Furthermore, expression of MUC1 was associated with decreased cell proliferation, either in the context of the transfected HEK293T cells, or when comparing wild type (Muc1(+/+)) vs. knockout (Muc1(-/-)) mouse primary tracheal epithelial cells. We conclude that MUC1 inhibits cell proliferation through a beta-catenin/LEF-1/cyclin D1/c-Myc pathway.

Thymosin β4 triggers an epithelial–mesenchymal transition in colorectal carcinoma by upregulating integrin-linked kinase

The epithelial-mesenchymal transition (EMT) is crucial for the invasion and metastasis of many epithelial tumors including colorectal carcinoma (CRC). In the present study, a scattering and fibroblastic morphology with reduced intercellular contacts was found in the SW480 colon cancer cells overexpressing the gene encoding thymosin beta4 (Tbeta4), which was accompanied by a loss of E-cadherin as well as a cytosolic accumulation of beta-catenin, two most prominent markers of EMT. Whereas E-cadherin downregulation was likely to be accounted by a ZEB1-mediated transcriptional repression, the accumulation of beta-catenin was a result of glycogen synthase kinase-3beta inactivation mediated by integrin-linked kinase (ILK) and/or its downstream effector, Akt. Intriguingly, ILK upregulation in Tbeta4-overexpressing SW480 cells seemed to be attributed mainly to a stabilization of this kinase by complexing with particularly interesting new Cys-His protein (PINCH) more efficiently. In the meantime, a strong correlation between the expression levels of Tbeta4, ILK and E-cadherin in CRC patients was also revealed by immunohistochemical analysis. Taken together, these data suggest a novel role of Tbeta4 in promoting CRC progression by inducing an EMT in tumor cells via upregulating ILK and consequentially its signal transduction.

Biochemical interactions among intercellular adhesion molecules expressed by airway epithelial cells

Intercellular adhesion between adjacent airway epithelial cells plays a critical role in maintaining the barrier function of the respiratory mucosa. In the current study, we examined the expression and interaction of cell surface adhesion molecules (E-cadherin, ICAM-1, and MUC1) and their intracellular binding partners (alpha-catenin, beta-catenin, gamma-catenin, and ezrin) in 16HBE14o-, HBE1, 1HAEo-, BEAS-2B, A549, and NCI-H292 human airway epithelial cells. Expression of E-cadherin and MUC1, both in whole cell lysates and biotinylated surface proteins, was observed in 16HBE14o-, HBE1, A549, and NCI-H292 cells, while ICAM-1 was detected only in NCI-H292. In contrast, alpha-, beta-, and gamma-catenin and ezrin were expressed in all of the cells. E-cadherin formed coimmunoprecipitation complexes with beta- and gamma-catenin, whereas MUC1 only associated with beta-catenin. ICAM-1, but not MUC1, coimmunoprecipitated with ezrin in NCI-H292 cells. We conclude that airway epithelial cell-cell adhesion involves a complex network of protein-protein interactions mediated by a diverse array of membrane-bound and cytosolic protein partners.

Interaction of nuclear receptors with the Wnt/beta-catenin/Tcf signaling axis: Wnt you like to know?

The cross-regulation of Wnt/beta-catenin/Tcf ligands, kinases, and transcription factors with members of the nuclear receptor (NR) family has emerged as a clinically and developmentally important area of endocrine cell biology. Interactions between these signaling pathways result in a diverse array of cellular effects including altered cellular adhesion, tissue morphogenesis, and oncogenesis. Analyses of NR interactions with canonical Wnt signaling reveal two broad themes: Wnt/beta-catenin modulation of NRs (theme I), and ligand-dependent NR inhibition of the Wnt/beta-catenin/Tcf cascade (theme II). Beta-catenin, a promiscuous Wnt signaling member, has been studied intensively in relation to the androgen receptor (AR). Beta-catenin acts as a coactivator of AR transcription and is also involved in co-trafficking, increasing cell proliferation, and prostate pathogenesis. T cell factor, a transcriptional mediator of beta-catenin and AR, engages in a dynamic reciprocity of nuclear beta-catenin, p300/CREB binding protein, and transcriptional initiation factor 2/GC receptor-interaction protein, thereby facilitating hormone-dependent coactivation and transrepression. Beta-catenin responds in an equally dynamic manner with other NRs, including the retinoic acid (RA) receptor (RAR), vitamin D receptor (VDR), glucocorticoid receptor (GR), progesterone receptor, thyroid receptor (TR), estrogen receptor (ER), and peroxisome proliferator-activated receptor (PPAR). The NR ligands, vitamin D(3), trans/cis RA, glucocorticoids, and thiazolidines, induce dramatic changes in the physiology of cells harboring high Wnt/beta-catenin/Tcf activity. Wnt signaling regulates, directly or indirectly, developmental processes such as ductal branching and adipogenesis, two processes dependent on NR function. Beta-catenin has been intensively studied in colorectal cancer; however, it is now evident that beta-catenin may be important in cancers of the breast, prostate, and thyroid. This review will focus on the cross-regulation of AR and Wnt/beta-catenin/Tcf but will also consider the dynamic manner in which RAR/RXR, GR, TR, VDR, ER, and PPAR modulate canonical Wnt signaling. Although many commonalities exist by which NRs interact with the Wnt/beta-catenin signaling pathway, striking cell line and tissue-specific differences require deciphering and application to endocrine pathology.

Expression of beta-catenin in human testes with spermatogenic defects

beta-catenin is a multifunctional molecule that functions in intercellular adhesion and signal transduction during assembly of AJs between Sertoli cells as well as between Sertoli cells and germ cells. To assess changes in the testicular beta-catenin in male infertility conditions, testicular tissues from obstructive azoospermia with normal spermatogenesis, spermatogenic arrest (SA) and Sertoli cell-only syndrome (SCO) patients were examined for immunohistochemical localization of beta-catenin. In normal spermatogenic tissue, expression of beta-catenin was largely found in the Sertoli cell-germ cell (primarily spermatocytes) contact areas. Interestingly, perinuclear localization of beta-catenin was found in spermatocytes and spermatids. In spermatogenic arrest, beta-catenin in cell contact areas between Sertoli cells and germ cells was greatly decreased, but perinuclear beta-catenin in spermatocytes was not. In SCO, weak or negligible immunoreactivity of beta-catenin was found in cell contacts between Sertoli cells. Nuclear localization of beta-catenin was found in myotubular cells in all samples. Taken together, altered expression of beta-catenin in cell contacts within the seminiferous epithelia in spermatogenic arrest and SCO suggests that interactions between Sertoli cells and germ cell are crucial for expression of beta-catenin, and thus functional development of AJs in seminiferous epithelia in human testis. It should be also emphasized that perinuclear beta-catenin in germ cells may play a specific role in spermatogenesis.

A novel organotypic culture model for normal human endometrium: regulation of epithelial cell proliferation by estradiol and medroxyprogesterone acetate

BACKGROUND

A novel organotypic culture system was established for modelling the hormonal responses of the normal human endometrium in vitro.

METHODS

Endometrial epithelial cells were cultured as glandular organoids within reconstituted extracellular matrix (Matrigel) in tissue culture inserts and stromal cells on plastic below the epithelial compartment. The effects of estradiol (E2) and E2 together with medroxyprogesterone acetate (MPA) on cell proliferation and the expression of estrogen receptor alpha (ERalpha) and progesterone receptor (PR) were studied in 10 epithelial-stromal co-cultures and in three parallel monocultures of epithelial organoids.

RESULTS

In co-cultures, E2 was shown to increase the percentage of Ki67-positive cells by approximately 2-fold relative to untreated controls. In the presence of MPA, a significant decrease in cell proliferation was detected. Similar results were obtained when the corresponding percentages of Ki67-positive organoids were calculated instead of individual cells. In the absence of stromal fibroblasts, Ki67 epithelial labelling remained below the control value after both hormonal treatments. Epithelial organoids retained their capacity to express estrogen and progesterone receptors in culture. E2 was shown to markedly increase and MPA to down-regulate the expression of PR. The expression of ERalpha was only slightly affected by either hormonal treatment.

CONCLUSIONS

The present organotypic model provides a novel in vitro system in which to study the effects of steroids in the normal human endometrium both in terms of cell proliferation and gene expression. The culture system holds promise as a useful method to screen novel steroid compounds and may help to circumvent problems related to the use of animal models.

PDX-1 haploinsufficiency limits the compensatory islet hyperplasia that occurs in response to insulin resistance

Inadequate compensatory beta cell hyperplasia in insulin-resistant states triggers the development of overt diabetes. The mechanisms that underlie this crucial adaptive response are not fully defined. Here we show that the compensatory islet-growth response to insulin resistance in 2 models--insulin receptor (IR)/IR substrate-1 (IRS-1) double heterozygous mice and liver-specific IR KO (LIRKO) mice--is severely restricted by PDX-1 heterozygosity. Six-month-old IR/IRS-1 and LIRKO mice both showed up to a 10-fold increase in beta cell mass, which involved epithelial-to-mesenchymal transition. In both models, superimposition of PDX-1 haploinsufficiency upon the background of insulin resistance completely abrogated the adaptive islet hyperplastic response, and instead the beta cells showed apoptosis resulting in premature death of the mice. This study shows that, in postdevelopmental states of beta cell growth, PDX-1 is a critical regulator of beta cell replication and is required for the compensatory response to insulin resistance.

CDH1 germline mutation in hereditary gastric carcinoma

This paper provides a bird’s-eye view both in preclinical and clinical aspects of E-cadherin germline gene (CDH1) in gastric cancer patients and their families. E-cadherin, a product of CDH1 gene, belonging to the functionally related trans-membrane glycoprotein family, is responsible for the Ca²⁺-dependent cell-cell adhesion mechanism and contributes to dissociation followed by acquisition of cell motility, which usually occurs in the first step of cancer invasion and metastasis. CDH1 gene germline mutation is common in many types of carcinoma, and occurs very frequent in hereditary gastric carcinoma (HGC) patients and their families. Recently, more and more researches support that E-cadherin plays an important role in the differentiation, growth and invasion of HGC. So it is of great value to clarify its mechanisms both for understanding HGC pathogenesis and for clinical therapy, especially in China, where there are a high risk population of gastric cancer and a high HGC incidence rate. In this paper, recent researches on CDH1 gene mutation, especially its role in tumor genesis and progress of HGC, are reviewed, and advances in evaluation of its mutation status for HGC diagnosis, therapy and prognosis, are also discussed briefly.

Sequential analysis of development of invasive thyroid follicular cell carcinomas in inflamed capsular regions of rats treated with sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation

A 2-stage thyroid follicular carcinogenesis model in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN) is widely used to detect modifying effects of chemicals on thyroid carcinogenesis. A number of goitrogens are known to strongly promote carcinogenesis, and the carcinomas often originate adjacent to the thyroid capsule and show invasive growth into the capsule or adjacent tissues. To clarify mechanisms of progression to invasive carcinomas, we sequentially evaluated histopathological and immunohistochemical characteristics of thyroids in male F344 rats treated with sulfadimethoxine (SDM, 0.1% in drinking water) for 0-10 weeks beginning 1 week after DHPN initiation (2800 mg/kg body weight, single s.c. injection). In DHPN-SDM-treated rats, multiple focal hyperplasias and adenomas developed in thyroid follicular parenchyma at weeks 4 to 6. Apart from the proliferative lesions, capsular thickening with inflammatory cell infiltration, mainly consisting of macrophages, and migration of follicular epithelium into the capsule were also observed. Focal hyperplasias/adenomas adjacent to the capsule progressively developed to invasive carcinomas at weeks 6 to 10. In thyroid parenchyma, malignant lesions were seldom observed. With SDM-treatment alone, although no neoplastic lesions were observed, capsular thickening with inflammation and epithelial migration resulted in intracapsular residual follicles. Intracapsular residual follicular cells as well as invasive and intrathyroidal carcinoma cells generally showed increased cell proliferative activity, coincidental with cytoplasmic/nuclear positivity for beta-catenin. These results suggested that beta-catenin activation related to capsular inflammation may play a role in development of invasive carcinomas but is insufficient for tumor formation by itself. Whether this is associated with mutations in the beta-catenin gene remains to be clarified.

The role of epithelial-to-mesenchymal transition in renal fibrosis

Epithelial-to-mesenchymal transition (EMT) involving injured epithelial cells plays an important role in the progression of fibrosis in the kidney. Tubular epithelial cells can acquire a mesenchymal phenotype, and enhanced migratory capacity enabling them to transit from the renal tubular microenvironment into the interstitial space and escape potential apoptotic cell death. EMT is a major contributor to the pathogenesis of renal fibrosis, as it leads to a substantial increase in the number of myofibroblasts, leading to tubular atrophy. However, recent findings suggest that EMT involving tubular epithelial cell is a reversible process, potentially determined by the surviving cells to facilitate the repopulation of injured tubules with new functional epithelia. Major regulators of renal epithelial cell plasticity in the kidney are two multifunctional growth factors, bone morphogenic protein-7 (BMP-7) and transforming growth factor beta1 (TGF-beta1). While TGF-beta1 is a well-established inducer of EMT involving renal tubular epithelial cells, BMP-7 reverses EMT by directly counteracting TGF-beta-induced Smad-dependent cell signaling in renal tubular epithelial cells. Such antagonism results in the repair of injured kidneys, suggesting that modulation of epithelial cell plasticity has therapeutic advantages.

A novel antigen sensitive to calcium chelation that is associated with the tip links and kinocilial links of sensory hair bundles

Tip links are extracellular, cell-surface-associated filaments of unknown molecular composition that are thought to gate the mechanotransducer channel of the sensory hair cell. They disappear from the hair bundle in response to calcium chelation and lanthanum treatment and resist degradation by the protease subtilisin. A monoclonal antibody derived from a hybridoma screen identified a novel antigen associated with tip links, the tip-link antigen. The tip-link antigen is also associated with kinocilial links, subtilisin-resistant filaments that are sensitive to calcium chelation and connect the kinocilium to the tallest stereocilia of the hair bundle. Furthermore, the tip-link antigen is expressed in the retina, where it is associated with the ciliary calyx, a ring of microvilli that surrounds the outer segment of the photoreceptor. The tip-link antigen rapidly disappears from the surface of the hair bundle in response to calcium chelation. It is also subtilisin resistant, relative to the ankle-link antigen, an antigen associated with another type of hair bundle link. The tip-link antigen is lanthanum sensitive and, like tip links, reappears on the surface of the hair bundle after calcium chelation. The monoclonal antibody to the tip-link antigen immunoprecipitates two concanavalin A-reactive polypeptides with apparent molecular masses of 200 and 250 kDa from detergent extracts of the retina. These results provide the first identification of a cell surface antigen associated with tip links, indicate that tip links share properties in common with kinocilial links, and reveal a second epitope that, along with the ankle-link antigen, is common to both sensory hair bundles and the ciliary calyx of photoreceptors.

Classical cadherin and catenin expression in normal myometrial tissues and uterine leiomyomas

Uterine leiomyomas are the most common benign uterine tumors in the women of reproductive age. Previous studies have suggested that uterine leiomyomas are monoclonal tumors derived from a single neoplastic myometrial cell. However, the neoplastic transformation of myometrium to leiomyomas remains to be elucidated. The classical cadherins are a gene family of integral membrane glycoproteins that mediate calcium-dependent cell-cell adhesion in a homophilic manner. These cell adhesion molecules (CAMs) have been shown to play pivotal roles in tumorigenesis. Catenins are intracellular proteins that link the cytoplasmic domains of the cadherins to the cytoskeletons to promote the biological functions of these CAMs. In this study, we compared the expression of E-, N-, and P-cadherins and alpha-, beta-, and gamma-catenins in the uterine leiomyomas and the counterparts of normal myometrium of the same patients by using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. Of these, E-cadherin (E-cad) was not detected in both uterine leiomyomas and myometrium, P-cadherin (P-cad) was similarly expressed in these two tissues, but N-cadherin (N-cad) mRNA and protein expression levels in uterine leiomyomas were significantly greater than those observed in the myometrium. Catenins were not differentially expressed in uterine myometrium and leiomyomas. The overexpression of N-cad in uterine leiomyomas suggests that this CAM may play a central role in the development of uterine leiomyomas.

Galpha12 and Galpha13 negatively regulate the adhesive functions of cadherin

Cadherins function to promote adhesion between adjacent cells and play critical roles in such cellular processes as development, tissue maintenance, and tumor suppression. We previously demonstrated that heterotrimeric G proteins of the G12 subfamily comprised of Galpha12 and Galpha13 interact with the cytoplasmic domain of cadherins and cause the release of the transcriptional activator beta-catenin (Meigs, T. E., Fields, T. A., McKee, D. D., and Casey, P. J. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 519-524). Because of the importance of beta-catenin in cadherin-mediated cell-cell adhesion, we examined whether G12 subfamily proteins could also regulate cadherin function. The introduction of mutationally activated G12 proteins into K562 cells expressing E-cadherin blocked cadherin-mediated cell adhesion in steady-state assays. Also, in breast cancer cells, the introduction of activated G12 proteins blocked E-cadherin function in a fast aggregation assay. Aggregation mediated by a mutant cadherin that lacks G12 binding ability was not affected by activated G12 proteins, indicating a requirement for direct G12-cadherin interaction. Furthermore, in wound-filling assays in which ectopic expression of E-cadherin inhibits cell migration, the expression of activated G12 proteins reversed the inhibition via a mechanism that was independent of G12-mediated Rho activation. These results validate the G12-cadherin interaction as a potentially important event in cell biology and suggest novel roles for G12 proteins in the regulation of cadherin-mediated developmental events and in the loss of cadherin function that is characteristic of metastatic tumor progression.

Immunohistochemical detection of E-cadherin, alpha- and beta-catenins in papillary thyroid carcinoma

E-cadherin and catenins play a major role in neoplastic cell behavior as a suppressor of invasion and/or metastasis. The aim of this study was to determine E-cadherin, alpha-catenin and beta-catenin expressions in papillary thyroid carcinoma (PTC) and to correlate the results of expression to initial clinicopathological parameters and clinical outcome. Forty-one cases (mean age 37.3 +/- 11.2 yr) with PTC were studied. Patients were followed-up with a mean period of 47.6 +/- 27.0 months. A retrospective immunohistochemical analysis of E-cadherin, alpha-catenin and beta-catenin was performed on paraffin-embedded tissue sections. Tissues from ten patients with benign goiter were used as controls. E-cadherin, alpha- and beta-catenin immunoreactivities were found in 80% (33/41), 76% (31/41) and 97% (40/41) of patients respectively. No correlation was found between E-cadherin, alpha- and beta-catenin immunoreactivities and sex, local invasion or lymphatic spread at the time of initial examination. Distant metastases and/or local recurrences developed in 6 patients during follow-up. Recurrences/metastases developed both E-cadherin, alpha- and beta-catenin positive and negative primary tumors. Disease-free survival curves according to Kaplan-Meier analysis and log-rank test did not show any significant differences between E-cadherin, alpha- and beta-catenin positive and negative patients. According to our findings, E-cadherin, alpha- and beta-catenin expressions may not add any valuable information to the follow-up in a subgroup of PTC patients with a relatively benign course.

Identification of the cadherin subtypes present in the human peritoneum and endometriotic lesions: potential role for P-cadherin in the development of endometriosis

Endometriosis is defined as endometrial tissue outside of the uterine cavity. The pathogenesis of this common disease remains poorly understood. However, the implantation and invasion of the viable cells from retrograde menstruation into the peritoneum is a widely accepted theory. To date, the mechanisms by which cell adhesion molecules mediate the development of human endometriosis remain unclear. Cadherins are a family of cell adhesion molecules that mediate cell-cell adhesion in a homophilic manner. In this study, the cadherins present in the peritoneum and endometriotic lesions were identified by RT-PCR using degenerate primers. In addition, differences in the levels of the cadherin mRNA transcripts present in eutopic endometrium and endometriotic lesions of the same patients were then compared by semiquantitative RT-PCR. Multiple cadherins were detected in the peritoneum and endometriotic lesions. Of these, P-cadherin appears to be the predominant cadherin subtype present in the peritoneum. Similarly, P-cadherin mRNA levels in endometriotic lesions were significantly greater than those observed in the corresponding eutopic endometrium. The expression of P-cadherin in both the human peritoneum and endometriotic lesions suggests that this cell adhesion molecule may play a central role in the development of endometriosis by mediating endometrial-peritoneal cell interactions in a homophilic manner.

Wnt signaling in the ovary: identification and compartmentalized expression of wnt-2, wnt-2b, and frizzled-4 mRNAs

Ovarian cadherins, in addition to acting as structural (adhesion) molecules, also function as modulators of gene activity. The dual role of beta-catenin as an intracellular component of the cadherin adhesion complex and as a transcription factor provides a possible explanation for these cadherin effects. Because the transcriptional activity of beta-catenin is dependent on activation by the wnt signaling cascade, we examined whether components of this cascade are expressed in the rat ovary. Using RT-PCR with degenerate primers on RNA from ovaries of hormone-stimulated immature rats, we identified transcripts for wnt-2 and wnt-2b. RT-PCR and in situ hybridization (ISH) demonstrated that granulosa cells express wnt-2 mRNA. Because the sequence for rat wnt-2b has not been reported, we obtained additional sequence by screening a rat ovarian cDNA library. RT-PCR analysis, using primers designed from this wnt-2b cDNA sequence, failed to detect transcripts in the ovarian follicular compartment (granulosa and oocyte). ISH revealed that the ovarian surface epithelium expresses wnt-2b mRNA. Using a similar degenerate RT-PCR approach, we detected expression of a putative wnt receptor, frizzled-4 (fzd-4), and a cytoplasmic component of the wnt signaling cascade, disheveled-2 (dsh-2), in the rat ovary. Further analyses using both RT-PCR and ISH indicated that granulosa cells express fzd-4 mRNA. The expression of wnt-2b transcripts in rat ovarian surface epithelium prompted us to examine whether the homologous gene is expressed in human ovarian cancer cell lines. RT-PCR, using degenerate and specific primers for wnts, on RNA from five ovarian cancer cell lines confirmed the expression of transcripts for wnt-2b. Two additional wnt transcripts (wnt-5a and wnt-11) were detected in the cancer cell lines and in the rat ovary. These results demonstrate that transcripts corresponding to components of the wnt signaling cascade are expressed in the immature rat ovary. The localization of these transcripts in specific ovarian compartments suggests that this signal transduction pathway may be involved in follicular development and ovarian function. Furthermore, because wnts have been implicated in the oncogenic transformation of epithelial cells, our results raise the possibility that aberrant wnt expression may be involved in ovarian tumorigenesis in humans.

Benzo(a)pyrene, but not 2,3,7,8-tetrachlorodibenzo-p-dioxin, alters cell adhesion proteins in human uterine RL95-2 cells

This study compared the effects of benzo(a)pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), two aryl hydrocarbon receptor agonists, on cell attachment and adherens junction proteins in RL95-2 human uterine endometrial cells. Exposure to 10 microM BaP significantly decreased cell attachment to Matrigel, whereas 10 nM TCDD had no effect. Immunocytochemistry and Western immunoblot analysis showed that BaP, but not TCDD, produced a marked loss of plasma membrane epidermal growth factor receptor (EGF-R) localized along intercellular boundaries. BaP-treated cells exhibited significant decreases in beta-catenin and cadherin protein levels, while vinculin levels remained unchanged relative to control. In contrast, TCDD treatment had no effect on the levels of beta-catenin, cadherin, or vinculin. Further studies using the fluorescein labeled peptide phalloidin showed the presence of continuous subcortical actin filaments in control cells, whereas BaP-treated cells had subcortical actin aggregates. Thus, in contrast to TCDD, BaP produces a loss of cell attachment involving decreased localization of molecules important for cell-cell interactions in RL95-2 cells.

Chlamydia trachomatis disrupts N-cadherin-dependent cell-cell junctions and sequesters beta-catenin in human cervical epithelial cells

The cadherin/catenin complex serves as an important structural component of adherens junctions in epithelial cells. Under certain conditions, beta-catenin can be released from this complex and interact with transcription factors in the nucleus to stimulate the expression of genes that regulate apoptosis and cell cycle control. While studying the effects of the bacterial pathogen Chlamydia trachomatis on human cervical epithelial cells in culture, we observed that C. trachomatis caused the epithelial cells to separate from each other without detaching from their growing surface. The objective of the present study was to determine if this effect might involve the disruption of the cadherin/catenin complex. Primary cultures of human cervical epithelial cells or HeLa cells were infected with C. trachomatis serovar E. Cadherin-like immunoreactive materials and beta-catenin were visualized by immunofluorescence. Preliminary studies showed that N-cadherin was the primary cadherin expressed in both the primary cultures and the HeLa cells. In noninfected cells, N-cadherin and beta-catenin were colocalized at the intercellular junctional complexes. By contrast, the infected cells showed a marked loss of both N-cadherin and beta-catenin labeling from the junctional complexes and the concomitant appearance of intense beta-catenin labeling associated with the chlamydial inclusion. The results of Western blot analyses of extracts of C. trachomatis showed no evidence of cross-reactivity with the beta-catenin antibody. These results indicate that C. trachomatis causes the breakdown of the N-cadherin/beta-catenin complex and that the organism can sequester beta-catenin within the chlamydial inclusion. This could represent an important mechanism by which C. trachomatis alters epithelial cell function.

Epithelial-type and neural-type cadherin expression in malignant noncarcinomatous neoplasms with epithelioid features that involve the soft tissues

CONTEXT

Transmembrane adhesion molecules, epithelial-type cadherin (ECAD) and neural-type cadherin (NCAD), help in regulating transformations between epithelial and mesenchymal cells in the developing embryo and in maintaining the epithelioid phenotype. Consequently, the presence of epithelioid cells in certain malignant noncarcinomatous neoplasms raises speculation that the expression of ECAD and NCAD in these neoplasms may have diagnostic significance.

OBJECTIVE

To investigate the utility of ECAD and NCAD immunoexpression in distinguishing malignant (noncarcinomatous) neoplasms with epithelioid features that involve the soft tissues.

DESIGN

Membranous immunoreactivity of anti-ECAD and anti-NCAD was evaluated on archived cases selected from the files of the Armed Forces Institute of Pathology.

RESULTS

Epithelial-type cadherin was found in biphasic synovial sarcoma (35 of 35 cases), malignant melanoma (13/21), monophasic fibrous synovial sarcoma (13/26), clear cell sarcoma (4/9), poorly differentiated synovial sarcoma (3/13), diffuse mesothelioma (4/20), malignant epithelioid peripheral nerve sheath tumor (1/6), and epithelioid sarcoma (5/62). Neural-type cadherin was observed in chordoma (11/11), biphasic synovial sarcoma (30/35), diffuse mesothelioma (14/20), malignant melanoma (14/25), epithelioid sarcoma (24/63), epithelioid angiosarcoma (1/4), poorly differentiated synovial sarcoma (2/13), clear cell sarcoma (1/10), and monophasic fibrous synovial sarcoma (1/26). Eighteen cases of primary cutaneous squamous cell carcinomas all tested positive for ECAD, whereas NCAD was focally observed in 5 cases. No expression of either molecule was observed in cases of epithelioid hemangioendothelioma (n = 9), alveolar soft part sarcoma (n = 8), and extraskeletal myxoid chondrosarcoma (n = 7).

CONCLUSIONS

Epithelial-type and neural-type cadherins are found in a variety of noncarcinomatous neoplasms with epithelioid features that involve the soft tissues and can be utilized, in association with other immunomarkers, in distinguishing chordoma (100% NCAD) from extraskeletal myxoid chondrosarcoma and conventional chondrosarcoma of bone (0% NCAD), squamous cell carcinoma (100% ECAD) from epithelioid sarcoma (8% ECAD), and biphasic synovial sarcoma (100% ECAD) from diffuse mesothelioma (20% ECAD).

Regulation of pancreatic cell differentiation and morphogenesis

Organogenesis requires tissue interactions to initiate the cascade of inductive and repressive signals necessary for normal organ development. Tissue interactions initiate the pancreatic lineage within the primitive foregut endodermal epithelium and continue to direct the morphogenesis and differentiation of the endocrine, exocrine and ductal portions of the pancreas. An understanding of the mechanisms controlling pancreatic growth would enable the development of alternative therapies for diseases such as type 1 diabetes.