beta-Catenin--one player, two games

Downregulated BIRC5 inhibits proliferation and metastasis of melanoma through the β-catenin/HIF-1α/VEGF/MMPs pathway

PURPOSE

Melanoma is a malignant skin tumor caused by melanocytes and associated with high mortality rates. This study aims to investigate the specific mechanism of ZWZ-3 in melanoma proliferation and metastasis.

METHODS

RNA sequencing was performed to identify the effect of ZWZ-3 on gene expression. siRNA was used to inhibit BIRC5 gene expression in the B16F10 cell line. A zebrafish tumor model was used to assess the therapeutic effect of ZWZ-3 in vivo. Mechanistic insights into the inhibition of tumor metastasis by ZWZ-3 were obtained through analysis of tumor tissue sections in mice.

RESULTS

Our findings demonstrated that ZWZ-3 suppressed melanoma cell proliferation and migration. We performed RNA sequencing in melanoma cells after the treatment with ZWZ-3 and found that Birc5, which is closely associated with tumor metastasis, was significantly down-regulated. Bioinformatics analysis and the immuno-histochemical results of tissue chips for melanoma further confirmed the high expression of BIRC5 in melanoma and its effect on disease progression. Moreover, Birc5 knock-down significantly inhibited melanoma cell proliferation and metastasis, which was correlated with the β-catenin/HIF-1α/VEGF/MMPs pathway. Additionally, ZWZ-3 significantly inhibited tumor growth in the zebrafish tumor model without any evident side effects. Histological and immuno-histochemical analyses revealed that ZWZ-3 inhibited tumor cell metastasis by down-regulating HIF-1α, VEGF, and MMP9.

CONCLUSION

Our findings revealed that ZWZ-3 could downregulate BIRC5 and inhibit melanoma proliferation and metastasis through the β-catenin/HIF-1α/VEGF/MMPs pathway. Therefore, BIRC5 represents a promising therapeutic target for the treatment of melanoma.

Prognostic significance of survivin, β-catenin and p53 expression in urothelial carcinoma

Survivin, β-catenin, and p53 are well-known cell-cycle and apoptosis regulators of tumorigenesis. Urothelial carcinomas (UCs) are the most common of the human cancers. Compared to superficial tumors (Ta, CIS, or T1), invasive UCs are important with regard to recurrence, progression, and mortality. Therefore, we examined whether survivin, β-catenin, and p53 could be used as the biomarkers for the early prediction of the invasiveness of UCs and the overall survival of the patients. We investigated the prognostic expressions of those biomarkers in UC (n=147) and in non-muscle invasive UC (NMI-UC) (n=113), using tissue microarray and immunohistochemistry. Spearman's correlation analysis and multivariate Cox regression analyses were used for statistical interpretation. High expressions of β-catenin, survivin, and p53 were associated with a high T stage, recurrence, progression, mortality, low recurrence-free survival, low progression-free survival and low overall survival (p <0.01). Similar findings were achieved for recurrence and progression in the NMI-UC group, except for mortality. Moreover, a positive correlation was shown between p53 and β-catenin and between p53 and survivin (r=0.221, p <0.01; r=0.236, p <0.01, respectively). Survivin, p53, and β-catenin overexpression, as prognostic markers, might suggest that the UCs are biologically aggressive with the poor prognosis. Thus, dysregulation of those these cell-cycle and apoptosis regulators in bladder carcinoma could be used as a molecular marker to determine the best treatment strategy and could contribute to the development of targeted therapies.

Survivin expression promotes VEGF-induced tumor angiogenesis via PI3K/Akt enhanced β-catenin/Tcf-Lef dependent transcription

Early in cancer development, tumour cells express vascular endothelial growth factor (VEGF), a secreted molecule that is important in all stages of angiogenesis, an essential process that provides nutrients and oxygen to the nascent tumor and thereby enhances tumor-cell survival and facilitates growth. Survivin, another protein involved in angiogenesis, is strongly expressed in most human cancers, where it promotes tumor survival by reducing apoptosis as well as favoring endothelial cell proliferation and migration. The mechanisms by which cancer cells induce VEGF expression and angiogenesis upon survivin up-regulation remain to be fully established. Since the PI3K/Akt signalling and β-catenin-Tcf/Lef dependent transcription have been implicated in the expression of many cancer-related genes, including survivin and VEGF, we evaluated whether survivin may favor VEGF expression, release from tumor cells and induction of angiogenesis in a PI3K/Akt-β-catenin-Tcf/Lef-dependent manner. Here, we provide evidence linking survivin expression in tumor cells to increased β-catenin protein levels, β-catenin-Tcf/Lef transcriptional activity and expression of several target genes of this pathway, including survivin and VEGF, which accumulates in the culture medium. Alternatively, survivin downregulation reduced β-catenin protein levels and β-catenin-Tcf/Lef transcriptional activity. Also, using inhibitors of PI3K and the expression of dominant negative Akt, we show that survivin acts upstream in an amplification loop to promote VEGF expression. Moreover, survivin knock-down in B16F10 murine melanoma cells diminished the number of blood vessels and reduced VEGF expression in tumors formed in C57BL/6 mice. Finally, in the chick chorioallantoid membrane assay, survivin expression in tumor cells enhanced VEGF liberation and blood vessel formation. Importantly, the presence of neutralizing anti-VEGF antibodies precluded survivin-enhanced angiogenesis in this assay. These findings provide evidence for the existance of a posititve feedback loop connecting survivin expression in tumor cells to PI3K/Akt enhanced β-catenin-Tcf/Lef-dependent transcription followed by secretion of VEGF and angiogenesis.

Beneficial effects of sulindac in focal cerebral ischemia: a positive role in Wnt/β-catenin pathway

BACKGROUND

Accumulated evidences have established that inflammatory damage plays an important role in cerebral ischemic pathogenesis and may represent a target for treatment. Sulindac is well known as a nonsteroidal anti-inflammatory drug. However, little is known regarding the effect of sulindac in acute cerebral ischemia. Here, we designed this study to investigate the potential protective effects of sulindac in focal cerebral ischemia and the mechanisms underlying in vivo.

METHODS

Focal cerebral ischemia was induced in male Sprague-Dawley rats by permanent middle cerebral artery occlusion (pMCAO). Sulindac was administrated at dose of 4, 10, or 20mg/kg at 30 min before the operation. Neurological deficit scores, brain water content and infarct volumes were measured at 24h after pMCAO. Immunohistochemistry, western blot and reverse transcription-polymerase chain reaction were used for examining the mediators involved in Wnt/β-catenin signaling pathway, including the positive regulators dishevelled (Dvl) and β-catenin, the negative regulators adenomatous polyposis coli (APC), and P-β-catenin, as well as the downstream targets Bcl-2, Bax and claudin-5.

RESULTS

Compared with Vehicle group, 20mg/kg sulindac reduced neurological deficits, brain water content and infarct volumes. The same dose of sulindac upregulated the expression of Dvl, β-catenin, Bcl2 and claudin-5, and downregulated APC, P-β-catenin and Bax compared with Vehicle group.

CONCLUSIONS

These results showed that sulindac had a significant beneficial effect in cerebral ischemia; this effect may be correlated with the activation of the Wnt/β-catenin signaling.

BMP-2-Modulated Chondrogenic Differentiation In Vitro Involves Down-Regulation of Membrane-Bound Beta-Catenin

Bone morphogenetic proteins (BMPs) are important regulators of cellular differentiation and embryonic development. Beta catenin mediated nuclear signaling has been implicated in BMP-2-modulated chondrogenic differentiation in the pluripotential stem cell line C3H10T1/2. However, there is little information on the functional role of beta catenin in BMP-2-modulated differentiation of primary nontransformed mesenchymal cells. Here, we present evidence to show that BMP-2-induced chondrogenic differentiation in high-density primary mesenchymal culture is associated with a significant decrease in membrane-bound beta catenin by 72 hours compared to controls. Nuclear localization of beta catenin is not detectable by immunofluorescence and the TCF-responsive reporter vector TOPFLASH shows only background activity during chondrogenic differentiation. BMP-2-treated cultures show reduced cell-cell adhesion by 72 hours, which correlates with the changes in levels of membrane-bound beta catenin. Up-regulation of membrane-bound beta catenin blocks the effect of BMP-2 on both chondrogenic differentiation and cell-cell adhesiveness. These findings suggest that BMP-2 can modulate the adhesivity of adherens junctions through regulation of membrane bound beta catenin.

Molecular analysis of the beta-catenin gene in patients with the Mayer-Rokitansky-Küster-Hauser syndrome

PURPOSE

To study the beta-catenin gene in a group of Mayer-Rokitansky-Küster-Hauser patients.

METHODS

Twelve patients with the Mayer-Rokitansky-Küster-Hauser syndrome were included in this study. DNA was extracted from peripheral blood and the region codifying beta-catenin GSK-3beta phosphorylation sites on exon 3 was amplified. PCR products were purified and directly sequenced.

RESULTS

No mutations were found in the GSK-3beta phosphorylation sites on exon 3 of beta-catenin gene in this group of patients with the MRKH syndrome.

CONCLUSIONS

beta-catenin gene mutations are an unlikely cause of the MRKH syndrome.

Beta-catenin overexpression augments angiogenesis and skeletal muscle regeneration through dual mechanism of vascular endothelial growth factor-mediated endothelial cell proliferation and progenitor cell mobilization

OBJECTIVE

Beta-catenin plays a critical role in directing cell fate during embryogenesis, and uncontrollable activation leads to cancers, suggesting its importance in cell survival and proliferation. However, little is known regarding its role in endothelial cell (EC) and skeletal muscle proliferation and progenitor cell mobilization.

METHODS AND RESULTS

Beta-catenin enhanced ECs proliferation, protected ECs from apoptosis, and increased the capillary forming capabilities, which was completely blocked by inhibition of its nuclear translocation. In addition, the increased proliferation by beta-catenin was associated with increased expression of cyclin E2. In skeletal myocytes, beta-catenin overexpression increased proliferation with cyclin D1 expression, decreased apoptosis, and induced hypertrophy. Furthermore, beta-catenin induced the expression of vascular endothelial growth factor (VEGF) in skeletal myocytes, resulting in EC proliferation. In a mouse hindlimb ischemia model, beta-catenin significantly increased recovery of blood perfusion, capillary density along with enhanced VEGF expression, and the number of proliferating ECs and myocytes. Local delivery of beta-catenin also promoted angiogenic progenitor cell mobilization and increased the number of satellite cells.

CONCLUSIONS

Beta-catenin may be an important modulator of angiogenesis and myocyte regeneration not only by directly enhancing proliferation and survival of ECs and skeletal myocytes but also by inducing VEGF expression and promoting angiogenic progenitor cell mobilization and muscle progenitor cell activation.

Biological relevance of E-cadherin-catenin complex proteins in primary epithelial ovarian tumours

This study analysed the biological relevance of E-cadherin, alpha-catenin, beta-catenin and gamma-catenin immunoexpression pattern (reduced vs. preserved phenotype) in epithelial ovarian tumours. Immunohistochemistry was used to evaluate the expression of these proteins in 154 epithelial ovarian tumours, consisting of 17 benign, 33 borderline and 104 malignant tumours. In borderline tumours, the immunoexpression pattern of E-cadherin (p = 0.014) and alpha-catenin (p = 0.030) associated with histological type. In malignant tumours, the immunoexpression pattern of E-cadherin was related with histological type (p = 0.001). The immunoexpression pattern of beta-catenin associated with histological type and tumour differentiation (p = 0.005, p = 0.025, respectively). The preserved phenotype of E-cadherin was most frequently observed in mucinous tumours, whereas reduced E-cadherin was most frequently observed in serous tumours. The preserved phenotype of beta-catenin associated with endometrioid carcinomas, while reduced beta-catenin associated with poorly differentiated serous and clear cell carcinomas. Although the reduced phenotype was the most frequent immunoexpression observed for all proteins of the E-cadherin-catenin complex in epithelial ovarian tumours, only beta-catenin showed a significant difference between benign, borderline and malignant tumours (p = 0.045), since borderline and malignant tumours most frequently showed the reduced phenotype. The immunohistochemical profile of beta-catenin was shown to be of biological relevance: reduced beta-catenin was correlated with loss of tumour differentiation and serous carcinomas that are known to depict aggressive biological behaviour in epithelial ovarian tumours.

Establishment of Vessel-Like Structures in Long-Term Three-Dimensional Tissue Culture of Myocardium: An Electron Microscopy Study

To assess whether long-term three-dimensional (3D) tissue culture of myocardium enables the in vitro establishment of vessel-like structures, myocardial tissue from newborn mice was incubated under conditions of 3D culture for at least 3 weeks, and studied by phase-contrast microscopy, conventional histology, immunohistochemistry, and electron microscopy. During 3 weeks of culture, a mean 24.35 +/- 3.74% of all aggregates contracted spontaneously. The contracting aggregates displayed a tissue-like architecture with small basal and apical zones, and a large central zone. The basal and apical zone consisted of immature mesenchymal cells. The underlying shell of the aggregate contained many cardiomyocytes. Vessel-like structures were found concentrated within the aggregates. Immunohistochemistry showed that up to 15% of the cells in the central zone of the aggregate were positive for the endothelial-specific BS-I lectin. Vessel-like structures were formed by cells, which often showed intracytoplasmatic lumena. Surrounding the neocapillaries, structures of a rudimentary basal membrane could be detected. A 3D culture of myocardial tissue permits the establishment of a rudimentary capillary network within the tissue aggregates, which presumably guarantees a sufficient tissue perfusion up to a maximum aggregate diameter of approximately 900 microm.

Tumour invasion and matrix metalloproteinases

Matrix metalloproteinases (MMPs) are proteolytic enzymes which play a major role in tumour invasion. They are mainly produced by host stromal cells in most carcinomas and their expression implies a close co-operation between tumour and stromal cells. Increasing data also demonstrate that, in association with a process of epithelial-to-mesenchymal transition, many MMPs can be expressed by tumour cell themselves. Their most well-known role is the degradation of extra-cellular matrix macromolecules which in turn may regulate tumour invasion in some conditions. This ECM degradation generates some matrikins which are also implicated in tumour invasion and angiogenesis. Moreover, MMPs are also implicated in the degradation of cell adhesion molecules and release and activation of growth factors.

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.

Association of E-cadherin and β-catenin immunoexpression with clinicopathologic features in primary ovarian carcinomas

Epithelial cadherin forms a complex with alpha-, beta-, and gamma-catenin proteins. Reduced expression of E-cadherin-catenins has been shown in human carcinomas and is associated with low histologic differentiation, increased risk of invasion, and metastatic disease. The immunoexpression pattern of E-cadherin and beta-catenin (reduced versus preserved phenotype) was evaluated in 104 primary ovarian carcinomas and related to clinicopathologic features of the tumors. The immunoexpression pattern of E-cadherin was associated with International Federation of Gynaecology and Obstetrics (FIGO) staging (P = 0.043), histologic subtype (P = 0.001), peritoneal metastasis (P = 0.006), and residual tumor (P = 0.036). The reduced phenotype of E-cadherin that was observed in 64% of the carcinomas (67/104) was associated with advanced stage tumors, serous carcinomas, presence of peritoneal metastasis, and residual tumor larger than 2 cm. The immunoexpression pattern of beta-catenin was associated with histologic subtype (P = 0.005), tumor differentiation (P = 0.025), and peritoneal metastasis (P = 0.041). The reduced phenotype of beta-catenin that was observed in 74% of the carcinomas (77/104) was associated with advanced stage tumors, poorly differentiated serous and clear cell carcinomas, presence of peritoneal metastasis, and residual tumor. The immunoexpression pattern of E-cadherin was correlated with beta-catenin (P = 0.001). The reduced phenotype for both E-cadherin and beta-catenin was associated with histologic subtype (P < 0.001) and peritoneal metastasis (P = 0.001). In conclusion, the immunohistochemical profile of E-cadherin and beta-catenin may be useful in identifying a particular subpopulation of ovarian cancer patients who are characterized by an adverse clinical outcome, because the reduced phenotype of these molecules was associated with poor tumor differentiation, peritoneal metastasis, and advanced FIGO stage tumors.

Frequent loss of the AXIN1 locus but absence of AXIN1 gene mutations in adenocarcinomas of the gastro-oesophageal junction with nuclear beta-catenin expression

Up to 60% of gastro-oesophageal junction (GEJ) adenocarcinomas show nuclear β-catenin expression, pointing to activated T-cell factor (TCF)/β-catenin-driven gene transcription. We demonstrate in five human GEJ adenocarcinoma cell lines that nuclear β-catenin expression indeed correlates with enhanced TCF-mediated transcription of a reporter gene. In several tumour types, TCF/β-catenin activation is caused by mutations in either adenomatous polyposis coli (APC), β-catenin exon 3, AXIN1, AXIN2 or β-transducin repeat-containing protein (β-TrCP). In GEJ adenocarcinomas, very few APC and β-catenin mutations have been found. Therefore, the mechanism of Wnt pathway activation remains unclear. In the present study, we did not find AXIN1 gene mutations in 17 GEJ tumours with nuclear β-catenin expression (without β-catenin exon 3 mutations). Six intragenic single nucleotide polymorphisms (SNPs) were identified. One of these, the AXIN1 gene T1942C SNP, has a frequency of 21% but is only very recently described despite numerous AXIN1 gene mutational studies. We provide evidence why this SNP was missed in single strand conformation polymorphism analyses. The AXIN1 gene G2063A variation was previously described as a gene mutation but we demonstrate that this is a polymorphism. With these six SNPs loss of heterozygosity (LOH) was found in 11 of 15 (73%) informative tumours. To investigate a possible AXIN1 gene dosage effect in GEJ tumours expressing nuclear β-catenin, AXIN1 locus LOH was determined in 20 tumours expressing membranous and no nuclear β-catenin. LOH was found in 10 of 13 (77%) informative cases. AXIN1 protein immunohistochemistry revealed cytoplasmic expression in all tumours irrespective of the presence of AXIN1 locus LOH. These data indicate that nuclear β-catenin expression is indicative for activated Wnt signalling and that neither AXIN1 gene mutations nor AXIN1 locus LOH are involved in Wnt pathway activation in GEJ adenocarcinomas.

Anti-Müllerian hormone, beta-catenin and Müllerian duct regression

The embryo is initially sexually indifferent, and correct sexual development is dependent on gonadal hormone production. Thus, in the male embryo, anti-Müllerian hormone (AMH), secreted by the Sertoli cells of the testis, induces regression of the Müllerian duct, the anlagen of female reproductive tract. This hormone causes ductal epithelial regression through a paracrine mechanism originating in periductal mesenchyme and the cross-talk between the mesenchymal and epithelial layers accounts for the cranial-to-caudal pattern of Müllerian regression. Here, we review and discuss recent developments concerning the relationship of apoptosis of Müllerian duct to tissue remodeling, mesenchymal-epithelial interactions, and involvement of beta-catenin in AMH signaling in periductal mesenchyme. Determining the role of beta-catenin/LEF-1 signaling is critical for understanding AMH action during Müllerian duct regression.

beta-Catenin gene mutation in human hair follicle-related tumors

beta-Catenin, a multifunctional protein related to the adherens junction and to signal transduction, is a key molecule of cell proliferation, and it is central to epithelial architecture, regulating the polarity of cells and tissues. beta-Catenin stabilization may play a key role in epidermal signaling leading to hair development, and its aberrant activation may be implicated in formation of hair tumors. Several investigators have shown that pilomatricomas are frequently associated with beta-catenin mutation. In this study, we confirmed beta-catenin gene (CTNNB1) mutation in human pilomatricomas (100% frequency) from which adequate DNA could be obtained for gene analysis. A novel mutation, D32N, was found in one case of pilomatricoma. A preliminary immunohistological study revealed prominent beta-catenin staining in basophilic cells of pilomatricomas, especially in nuclei. Benign tumors which were considered to be derived from hair matrix or hair follicles, and other benign skin tumors, were also investigated. beta-Catenin mutations were not detected in any of the these tumors. These results seem to indicate that hair matrix cells are key players in hair development. Investigation into gene abnormalities of hair-follicle tumors may elucidate the cause of their neoplastic transformation, and may provide a suggestion for the mechanism of hair development.

The pathology of essential fatty acid deficiency: is it cell adhesion mediated?

For almost 70 years, essential fatty acid deficiency has been known to be associated with skin disorders, vessel abnormalities, and increased tumorigenesis. However, the underlying molecular and cellular mechanism is largely unknown. Recently, it has been reported that essential fatty acids regulate cell adhesion by modifying the expression of cell adhesion molecules. These findings may provide molecular explanations for those phenomena seen in EFAD and this paper aims to discuss these relationships and raise points for further discussion.

Beta-catenin, an inducer of uncontrolled cell proliferation and migration in malignancies, is localized in the cytoplasm of vascular endothelium during neovascularization after myocardial infarction

Beta-catenin is a protein involved in cell-cell adhesion and proliferation. In neoplastic diseases, defects in the regulation of the cellular beta-catenin content and cytoplasmic accumulation of the protein contribute to the uncontrolled cell proliferation and migration. Whether beta-catenin plays a role in the controlled proliferative and migratory responses to injury, eg, of vascular endothelial cells during neovascularization after myocardial infarction (MI), is not known. In the present study, we examined the localization of beta-catenin in the infarcted rat heart at different time points after MI. Cytoplasmic beta-catenin was observed in the endothelial cells of the newly formed and pre-existing blood vessels in the infarct area in the first week after MI, but not in the uninjured parts of the heart and not at later time points. Adenomatous polyposis coli (APC) protein was also detected; interaction of APC with beta-catenin has been reported to be critical in epithelial tube formation in vitro. Moreover, the expression of dishevelled-1, an upstream regulatory molecule of the cellular beta-catenin content, was observed in vascular endothelial cells in the infarct area. These findings suggest a role for the beta-catenin-APC complex in the proliferation and migration of vascular endothelial cells during neovascularization of the infarct area.

Expression of E-, P-, n-cadherins and catenins in human bladder carcinoma cell lines

PURPOSE

Cadherins are cell surface glycoproteins that mediate Ca2+-dependent, homophilic cell-cell adhesion. The classical cadherins, E-, P- and N-cadherins, are known to self-associate from their extracellular domain, while their cytoplasmic domain interacts with either beta-catenin or plakoglobin (gamma-catenin), which in turn is bound to alpha-catenin that links the complex to the actin cytoskeleton. The aim of the present study was to analyze the expression of E-, P- and N-cadherins and catenins in human bladder carcinoma cells.

MATERIALS AND METHODS

Five human bladder carcinoma cell lines, representing a variety of differentiation states, were grown in cell culture. We performed a cell aggregation assay, specific for biological cadherin activity. The expression of cadherins and catenins was analyzed by immunocytochemistry, Western blotting and RT-PCR. The interactions between cadherins and catenins were assessed by immunoprecipitation.

RESULTS

We observed a reduced E-cadherin expression in the poorly differentiated and invasive-tumor derived cells. Interestingly, immunofluorescence study reveals the persistent localization of catenins at intercellular contacts in two E-cadherin deficient cell lines (T24 and TCCSUP) which yet exhibit an epithelial-like morphology and a calcium-dependent adhesive capacity. This suggests that other cadherin(s) are expressed in these both cell lines. P-cadherin, another epithelial cadherin, is expressed only in E-cadherin positive cells. On the other hand, N-cadherin is present at cell-cell borders in the very anaplastic cell lines, T24 and TCCSUP, and is able to link beta-catenin or plakoglobin.

CONCLUSION

These results indicate that N-cadherin may participate in intercellular adhesion, while facilitating bladder tumorigenesis.

Molecular mechanisms of hormone-mediated Mullerian duct regression: involvement of beta-catenin

Regression of the Mullerian duct in the male embryo is one unequivocal effect of anti-Mullerian hormone, a glycoprotein secreted by the Sertoli cells of the testis. This hormone induces ductal epithelial regression through a paracrine mechanism originating in periductal mesenchyme. To probe the mechanisms of action of anti-Mullerian hormone, we have studied the sequence of cellular and molecular events involved in duct regression. Studies were performed in male rat embryos and in transgenic mice overexpressing or lacking anti-Mullerian hormone, both in vivo and in vitro. Anti-Mullerian hormone causes regression of the cranial part of the Mullerian duct whereas it continues to grow caudally. Our work shows that this pattern of regression is correlated with a cranial to caudal gradient of anti-Mullerian hormone receptor protein, followed by a wave of apoptosis spreading along the Mullerian duct as its progresses caudally. Apoptosis is also induced by AMH in female Mullerian duct in vitro. Furthermore, apoptotic indexes are increased in Mullerian epithelium of transgenic mice of both sexes overexpressing the human anti-Mullerian hormone gene, exhibiting a positive correlation with serum hormone concentration. Inversely, apoptosis is reduced in male anti-Mullerian hormone-deficient mice. We also show that apoptosis is a decisive but not sufficient process, and that epitheliomesenchymal transformation is an important event of Mullerian regression. The most striking result of this study is that anti-Mullerian hormone action in peri-Mullerian mesenchyme leads in vivo and in vitro to an accumulation of cytoplasmic beta-catenin. The co-localization of beta-catenin with lymphoid enhancer factor 1 in the nucleus of peri-Mullerian mesenchymal cells, demonstrated in primary culture, suggests that overexpressed beta-catenin in association with lymphoid enhancer factor 1 may alter transcription of target genes and may lead to changes in mesenchymal gene expression and cell fate during Mullerian duct regression. To our knowledge, this is the first report that beta-catenin, known for its role in Wnt signaling, may mediate anti-Mullerian hormone action.

Presenilins and Alzheimer's disease: biological functions and pathogenic mechanisms

Alzheimer's disease (AD) is the most common cause of dementia in the elderly population. Dementia is associated with massive accumulation of fibrillary aggregates in various cortical and subcortical regions of the brain. These aggregates appear intracellularly as neurofibrillary tangles, extracellularly as amyloid plaques and perivascular amyloid in cerebral blood vessels. The causative factors in AD etiology implicate both, genetic and environmental factors. The large majority of early-onset familial Alzheimer's disease (FAD) cases are linked to mutations in the genes coding for presenilin 1 (PS1) and presenilin 2 (PS2). The corresponding proteins are 467 (PS1) and 448 (PS2) amino-acids long, respectively. Both are membrane proteins with multiple transmembrane regions. Presenilins show a high degree of conservation between species and a presenilin homologue with definite conservation of the hydrophobic structure has been identified even in the plant Arabidopsis thaliana. More than 50 missense mutations in PS1 and two missense mutations in PS2 were identified which are causative for FAD. PS mutations lead to the same functional consequence as mutations on amyloid precursor protein (APP), altering the processing of APP towards the release of the more amyloidogenic form 1-42 of Abeta (Abeta42). In this regard, the physical interaction between APP and presenilins in the endoplasmic reticulum has been demonstrated and might play a key role in Abeta42 production. It was hypothesized that PS1 might directly cleave APP. However, extracellular amyloidogenesis and Abeta production might not be the sole factor involved in AD pathology and several lines of evidence support a role of apoptosis in the massive neuronal loss observed. Presenilins were shown to modify the apoptotic response in several cellular systems including primary neuronal cultures. Some evidence is accumulating which points towards the beta-catenin signaling pathways to be causally involved in presenilin mediated cell death. Increased degradation of beta-catenin has been shown in brain of AD patients with PS1 mutations and reduced beta-catenin signaling increased neuronal vulnerability to apoptosis in cell culture models. The study of presenilin physiological functions and the pathological mechanisms underlying their role in pathogenesis clearly advanced our understanding of cellular mechanisms underlying the neuronal cell death and will contribute to the identification of novel drug targets for the treatment of AD.

c-Myb is critical for murine colon development

The mammalian colon develops from a simple tube of undifferentiated cells into a complex, highly ordered organ, with a continuously self-renewing epithelial layer. We have previously described c-Myb expression in the epithelia of murine and human colon crypts and documented increased expression in colorectal adenocarcinoma cells. To investigate the role of c-Myb in colonic epithelium development, we have used embryos with a disrupted c-myb gene. Prior to the in utero death of these embryos at E15, we excised colon tissue and transplanted it under the kidney capsule of recipient mice to allow further development and cyto-differentiation. Compared to the colons of wildtype and heterozygous littermates, the c-myb homozygous knockout colon is highly irregular with a disordered epithelium and abnormal crypts. In addition, the expression of Bcl-2, a known target of c-Myb, is reduced and apoptosis is increased, indicating a critical requirement for c-Myb in normal colon development.

Localization of the giant axonal neuropathy gene to chromosome 16q24

Giant axonal neuropathy (GAN) is a degenerative disorder of the peripheral nerves that is inherited as an autosomal recessive trait, presenting in early childhood and progressing to death, usually by late adolescence. Diagnosis is made by peripheral nerve biopsy, in which a striking pathological finding is seen--fibers distorted by giant axonal swellings filled with densely packed bundles of neurofilaments (the primary intermediate filament in neurons), with segregation of other axoplasmic organelles. In addition to disorganized neurofilaments in nerve, disorganization of other members of the intermediate filament family of proteins is seen in other tissues; this implies that the underlying defect is one of generalized intermediate filament organization, with neurofilaments predominantly affected. We have pursued a genomewide search for regions of homozygosity of descent in 5 consanguineous families. A 5.3-cM region of homozygosity, shared in all 5 families, was found on chromosome 16q24, and linkage was established to this locus with a LOD score of 4.18 at theta = 0.00 at the most tightly linked marker, D16S3098. Determination of this locus is the first step toward characterizing the gene responsible for a fundamental property of intermediate filament organization and may shed light on other disorders (such as amyotrophic lateral sclerosis) in which neurofilament pathology is prominent.