Prevention of neutrophil extravasation by α2-adrenoceptor-mediated endothelial stabilization.

Adrenergic receptors are expressed on the surface of inflammation-mediating cells, but their potential role in the regulation of the inflammatory response is still poorly understood. The objectives of this work were to study the effects of α2-adrenergic agonists on the inflammatory response in vivo and to determine their mechanism of action. In two mouse models of inflammation, zymosan air pouch and thioglycolate-induced peritonitis models, the i.m. treatment with xylazine or UK14304, two α2-adrenergic agonists, reduced neutrophil migration by 60%. The α2-adrenergic antagonist RX821002 abrogated this effect. In flow cytometry experiments, the basal surface expression of L-selectin and CD11b was modified neither in murine nor in human neutrophils upon α2-agonist treatment. Similar experiments in HUVEC showed that UK14304 prevented the activation-dependent upregulation of ICAM-1. In contrast, UK14304 augmented electrical resistance and reduced macromolecular transport through a confluent HUVEC monolayer. In flow chamber experiments, under postcapillary venule-like flow conditions, the pretreatment of HUVECs, but not neutrophils, with α2-agonists decreased transendothelial migration, without affecting neutrophil rolling. Interestingly, α2-agonists prevented the TNF-α-mediated decrease in expression of the adherens junctional molecules, VE-cadherin, ß-catenin, and plakoglobin, and reduced the ICAM-1-mediated phosphorylation of VE-cadherin by immunofluorescence and confocal analysis and Western blot analysis, respectively. These findings indicate that α2-adrenoceptors trigger signals that protect the integrity of endothelial adherens junctions during the inflammatory response, thus pointing at the vascular endothelium as a therapeutic target for the management of inflammatory processes in humans.

Deferoxamine enhances cell migration and invasion through promotion of HIF-1α expression and epithelial-mesenchymal transition in colorectal cancer.

Deferoxamine (DFX), a metal chelator, has been previously reported to induce hypoxia and hypoxia-inducible factor-1α (HIF-1α) expression. HIF-1α is a common inducer of epithelial-mesenchymal transition (EMT) in many solid tumors. However, the effect of DFX on cancer metastasis and the related mechanisms are not well established. In the present study, we aimed to ascertain whether DFX enhances EMT and cancer metastasis in colorectal cancer. After confirmation of DFX-inducing HIF-1α expression, we examined the effect of DFX on cell adhesion, migration and invasion abilities and found a positive effect on the above functions. Consequently, cell morphology, cell growth and expression of EMT markers were assessed in cells with or without DFX treatment. We found that cells exposed to DFX were more isolated. They were spindle-shaped and looked similar to fibroblast-like cells, accompanied by increased anchorage-independent growth. DFX-treated cells expressed E-cadherin and plakoglobin at a higher level, and vimentin and N-cadherin at a lower level, when compared with these levels in control cells. Furthermore, the expression of E-cadherin in the cell membrane was markedly decreased in DFX-treated cells. These results suggest that DFX promotes cancer migration and invasion via a process consistent with EMT in colorectal cancer.

Assessment of desmosomal components (desmoglein 1-3, plakoglobin) in cardia mucosa in relation to gastroesophageal reflux disease and Helicobacter pylori infection.

Gastroesophageal reflux disease is associated with impaired epithelial barrier function and abnormal expression of proteins forming cell-cell contacts by tight junctions and desmosomes in distal esophageal squamous mucosa. Although gastroesophageal reflux disease and Helicobacter pylori are both associated with chronic inflammation of the adjacent cardia mucosa, it is not known whether these lead to derangements of the desmosomal complexes. Here, we assessed the expression of 4 proteins (plakoglobin and desmoglein 1, 2, and 3) forming epithelial desmosomal complexes by quantitative reverse transcription polymerase chain reaction and immunohistochemistry in biopsies from 67 patients with gastroesophageal reflux disease and 23 gastroesophageal reflux disease-negative controls. Plakoglobin and desmoglein 2 were ubiquitously expressed in all samples, whereas desmoglein 1 and 3 were not expressed in cardia mucosa. Gastroesophageal reflux disease was specifically associated with elevated transcript levels of desmoglein 2 and plakoglobin. These were significantly increased from 2.0- to 2.7-fold in patients with gastroesophageal reflux disease compared with controls (P < .01), and significantly increased immunohistochemical scores for both proteins were observed (P < .05) as well. The combined presence of gastroesophageal reflux disease and Helicobacter pylori infection had no additional effect on desmosomal gene expression. Taken together, the up-regulation of plakoglobin and desmoglein 2 in cardia mucosa of patients with gastroesophageal reflux disease supports the concept that the "transition zone" between distal esophagus and proximal stomach is affected by gastroesophageal reflux disease as well, and architectural and molecular changes in the desmosomal compartment contribute to the pathogenesis of gastroesophageal reflux disease in the cardia mucosa.

The EMT status in the primary tumor does not predict postoperative recurrence or disease-free survival in lung adenocarcinoma.

BACKGROUND: The epithelial to mesenchymal transition (EMT) is an important contributor to the invasion and metastasis of epithelial cell-derived cancer. However, whether or not the expression of EMT-related molecules can be used as a biomarker for the prognosis of lung cancer has yet to be fully determined. PATIENTS AND METHODS: Tumor specimens were collected from 183 consecutive patients who underwent a complete resection for lung adenocarcinoma. We analyzed the E-cadherin, gamma-catenin, vimentin, and fibronectin expression levels in the primary lung adenocarcinoma by immunohistochemical analysis. RESULTS: A positive expression of E-cadherin, gamma-catenin, vimentin, and fibronectin was observed in 94 (51.4%), 82 (40.4%), 32 (17.5%) and 1 (0.5%) patient, respectively. A significant association between E-cadherin expression and the pathological stage, T status, N status, tumor grade, and carcinoembryonic antigen was identified. The rate of gamma-catenin positivity was higher in patients with a smoking history than in never smokers. Moreover, a significant correlation was observed between vimentin expression and the pathological stage, N status, and tumor grade. However, an association between EMT-related molecules and postoperative recurrence of lung adenocarcinoma is lacking. Based on a Kaplan-Meier analysis, the expression of EMT-related molecules is not associated with the survival of lung adenocarcinoma patients. CONCLUSION: The EMT status in the primary tumor does not predict postoperative recurrence or disease-free survival in lung cancer patients. Our findings indicate that immunocytochemical markers related to EMT do not provide relevant prognostic information about lung adenocarcinoma. Future research is therefore expected to clarify the clinical usefulness of EMT-related molecules.

Sex differences in expression and subcellular localization of heart rhythm determinant proteins.

To evaluate sex differences in protein expression in the heart, we performed Western blot studies on a subset of Heart Rhythm Determinant (HRD) proteins. We examined key components of a variety of types of mechanical and electrical junctions including, connexin43, plakophilin-2, N-cadherin and plakoglobin, ankyrin-2 and actin. We describe novel findings in sex differences in cardiac protein expression and membrane localization. For most proteins examined, sex differences were significantly more pronounced in the membrane compartment than in overall expression. These studies extend our previous findings in microarray studies to demonstrate that sex differences in gene expression are likely to confer distinct functional properties on male and female myocardium.

Regulation of sonic hedgehog-GLI1 downstream target genes PTCH1, Cyclin D2, Plakoglobin, PAX6 and NKX2.2 and their epigenetic status in medulloblastoma and astrocytoma.

BACKGROUND: The Sonic hedgehog (Shh) signaling pathway is critical for cell growth and differentiation. Impairment of this pathway can result in both birth defects and cancer. Despite its importance in cancer development, the Shh pathway has not been thoroughly investigated in tumorigenesis of brain tumors. In this study, we sought to understand the regulatory roles of GLI1, the immediate downstream activator of the Shh signaling pathway on its downstream target genes PTCH1, Cyclin D2, Plakoglobin, NKX2.2 and PAX6 in medulloblastoma and astrocytic tumors. METHODS: We silenced GLI1 expression in medulloblastoma and astrocytic cell lines by transfection of siRNA against GLI1. Subsequently, we performed RT-PCR and quantitative real time RT-PCR (qRT-PCR) to assay the expression of downstream target genes PTCH1, Cyclin D2, Plakoglobin, NKX2.2 and PAX6. We also attempted to correlate the pattern of expression of GLI1 and its regulated genes in 14 cell lines and 41 primary medulloblastoma and astrocytoma tumor samples. We also assessed the methylation status of the Cyclin D2 and PTCH1 promoters in these 14 cell lines and 58 primary tumor samples. RESULTS: Silencing expression of GLI1 resulted up-regulation of all target genes in the medulloblastoma cell line, while only PTCH1 was up-regulated in astrocytoma. We also observed methylation of the cyclin D2 promoter in a significant number of astrocytoma cell lines (63%) and primary astrocytoma tumor samples (32%), but not at all in any medulloblastoma samples. PTCH1 promoter methylation was less frequently observed than Cyclin D2 promoter methylation in astrocytomas, and not at all in medulloblastomas. CONCLUSIONS: Our results demonstrate different regulatory mechanisms of Shh-GLI1 signaling. These differences vary according to the downstream target gene affected, the origin of the tissue, as well as epigenetic regulation of some of these genes.

2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) induces degradation of adherens junction proteins and inhibits beta-catenin-dependent transcription in liver epithelial cells.

The toxic modes of action of non-dioxin-like polychlorinated biphenyls (PCBs) in liver cells are still only partially understood. Several recent studies have indicated that PCBs may interfere with cell membrane protein functions. Therefore, we analyzed in the present study the effects of di-ortho-substituted 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) on proteins involved in the formation of adherens junctions in a model of rat liver progenitor cells - WB-F344 cell line. PCB 153, at micromolar concentrations, induced a gradual degradation of E-cadherin, beta-catenin or plakoglobin (gamma-catenin) proteins. This effect was not due to changes in gene expression, as PCB 153 had no effect on mRNA levels of the above mentioned proteins. Moreover, apart from the reduction of total beta-catenin pool, PCB 153 also decreased levels of the active beta-catenin form, dephosphorylated at residues Ser37 and Thr41, which is the key co-activator of Wnt-induced TCF/LEF-dependent gene expression. Therefore, we also evaluated the impact of PCB 153 on expression of Axin2, a known transcriptional target of canonical Wnt signaling. PCB 153 reduced basal Axin2 mRNA levels and it inhibited induction of Axin2 expression by recombinant mouse Wnt3a. Nevertheless, PCB 153 had no effect on phosphorylation of glycogen synthase kinase-3beta (GSK-3beta), which is supposed to target beta-catenin for its proteasomal degradation. This suggested that GSK-3beta activity is not modulated by PCB 153 and, consequently, not involved in the observed PCB 153-induced decrease of both total and active beta-catenin levels. Protein levels of E-cadherin and beta-catenin were partially restored with lysosomal inhibitor leupeptin, thus suggesting a possible role of lysosomes in the observed degradation of adherens junction proteins. Taken together, the present data suggest that PCB 153 may interfere with functions of adherens junction proteins involved in both cell-to-cell communication and intracellular signaling. Such mechanisms might be involved in the effects of non-dioxin-like PCBs contributing to liver tumor promotion.

DNMT3A and DNMT3B mediate autocrine hGH repression of plakoglobin gene transcription and consequent phenotypic conversion of mammary carcinoma cells.

Directed by microarray analyses, we report that autocrine human growth hormone (hGH) increased the mRNA and protein expression of DNA methyltransferase 1 (DNMT1), DNMT3A and DNMT3B in mammary carcinoma cells. Autocrine hGH stimulation of DNMT3A and DNMT3B expression was mediated by JAK2 and Src kinases, and treatment of mammary carcinoma cells with the DNMT inhibitor, 5'-aza-2'-deoxycytidine (AZA), abrogated autocrine hGH-stimulated cellular proliferation, apoptosis and anchorage-independent growth. AZA reversed the epitheliomesenchymal transition of mammary carcinoma cells induced by autocrine hGH, to an epithelioid morphology and abrogated cell migration stimulated by autocrine hGH. Autocrine hGH-stimulated hypermethylation of the first exon of the PLAKOGLOBIN gene and AZA abrogated the ability of autocrine hGH to repress plakoglobin gene transcription. Small interfering RNA (siRNA)-mediated depletion of the individual DNMT molecules did not release autocrine hGH repression of PLAKOGLOBIN promoter activity nor did individual DNMT depletion affect autocrine hGH-stimulated migration. However, concomitant siRNA-mediated depletion of both DNMT3A and DNMT3B abrogated hypermethylation of the PLAKOGLOBIN gene stimulated by autocrine hGH and subsequent repression of plakoglobin gene transcription and increased cell migration. Thus, the autocrine hGH-stimulated increases in DNMT3A and DNMT3B expression mediate repression of plakoglobin gene transcription by direct hypermethylation of its promoter and consequent phenotypic conversion of mammary carcinoma cells. Autocrine hGH, therefore, utilizes DNA methylation as a mechanism to exert its oncogenic effects in mammary carcinoma cells.

Robinson cytologic grading in invasive ductal carcinoma of the breast: correlation with E-cadherin and alpha-, beta- and gamma-catenin expression and regional lymph node metastasis.

OBJECTIVE: To correlate the cytologic grade of breast carcinoma with the expression of E-cadherin/catenin system molecules and the presence of metastasis in regional lymph nodes. STUDY DESIGN: Aspirate smears were examined together with histologic sections from the corresponding neoplasms taken from 100 patients with invasive ductal carcinoma. In 50 cases, > or = 1 metastatic nodes were identified. Cytologic grading of the smears was performed using the Robinson method. Immunohistochemical expression of E-cadherin and of alpha-, beta- and gamma-catenin was studied. RESULTS: A statistically significant relationship was observed between E-cadherin/catenin expression and cytologic grade (p < 0.0005). This association was particularly relevant to the cell dissociation parameter (p < 0.0005). CONCLUSION: The cytological grade established in preoperative studies may provide relevant information on the aggressiveness of invasive ductal carcinoma and its tendency to produce regional metastasis. This finding could be particularly useful in cases of breast carcinoma in which neoadjuvant therapy is the method of choice.

Plakoglobin is differentially expressed in alveolar and embryonal rhabdomyosarcoma and is regulated by DNA methylation and histone acetylation.

Plakoglobin (gamma-catenin) and beta-catenin are pivotal components of cell-cell adherent junctions that link cadherin receptors to the actin cytoskeleton. Whereas beta-catenin overexpression induces cell proliferation and tumor formation, plakoglobin induces tumor suppressor activity. We investigated the expression of plakoglobin in alveolar (ARMS) and embryonal (ERMS) rhabdomyosarcoma (RMS) cell lines and tumors, and found that plakoglobin is present both in the cytoplasm and in the nucleus of ERMS cells, whereas it is absent or detectable at extremely low levels in ARMS. As gene silencing can be mediated by methylation and/or deacetylation of promoter regions, we assessed the effects of the DNA demethylating agent 5-Aza-2'-deoxycytidine (5AzadC) and of the histone deacetylase inhibitor Trichostatin A (TSA), and obtained restoration of plakoglobin expression in ARMS cells cultivated in the presence of 5AzadC and TSA. By methylation-specific PCR, ARMS cells were shown to contain methylated CpG dinucleotides in CpG islands located around the transcriptional start site of one or both alleles, whereas ERMS cells did not. Furthermore, we demonstrated that promoter regions (P1-P3) of plakoglobin gene were associated with hypoacetylated H4 histone in ARMS cells RH4, suggesting that aberrant DNA methylation of the 5' CpG island and histone deacetylation play key roles in silencing the plakoglobin gene. These results demonstrate that plakoglobin is differentially expressed in ARMS and ERMS and that its expression depends on the methylation and acetylation status of the gene.

Expression of E-cadherin and alpha-, beta-, gamma-catenins in patients with bladder cancer: identification of gamma-catenin as a new prognostic marker of neoplastic progression in T1 superficial urothelial tumors.

Loss of intercellular adhesion facilitates tumor invasion. To clarify the relation between altered expression of cell adhesion molecules and progression of T1 superficial bladder tumors, 101 cases (71 T1 tumors, 30 T2/T3 tumors) were examined immunohistochemically for E-cadherin and alpha-, beta-, and gamma-catenins. A highly significant correlation was observed between the decreased expression of all molecules and increased TNM stage (P < .001). Univariate analysis, performed in cases of T1 tumors, revealed association of abnormal E-cadherin with beta-catenin diminution. Survival curves were established with the Kaplan-Meier method and analyzed according to clinical and histopathologic parameters using the log-rank test. Cox multivariate analysis revealed only gamma-catenin as an independent predictor of progression-free survival in patients with stage T1 bladder urothelial tumors. The characterization of T1 tumors that will progress could lead to the identification of patients who might benefit from surgery to avoid vesical muscle invasion and, consequently, metastasis.

The Brn-3b POU family transcription factor represses plakoglobin gene expression in human breast cancer cells.

The Brn-3b transcription factor has been shown to be overexpressed in human breast cancer cells and contributes toward cell growth regulation. Using micro-arrays, more than 50 cancer-related genes regulated by Brn-3b in human breast cancer cells have been identified. For example, Brn-3b activates the cell cycle regulator CDK4 that provides a mechanism by which Brn-3b controls the growth of breast cancer cells. Here, we show that Brn-3b regulates plakoglobin (gamma-catenin), a member of the catenin family involved in cell-cell adhesion and signal transduction. Brn-3b expression inversely correlates with plakoglobin expression at both mRNA and protein levels in breast cancer cell lines and human breast biopsies. In contrast, no significant correlation was observed between Brn-3b expression and beta-catenin, or between Brn-3b expression and E-cadherin expression. Brn-3b represses the plakoglobin promoter via a Brn-3 consensus binding site contained within the region -965 to -593 relative to the transcriptional start site. Both repression of the promoter and binding of Brn-3b are lost when this site is mutated. To our knowledge, this is the first time that a Brn-3b POU family transcription factor has been shown to regulate a member of the catenin family, which provides insight into the molecular mechanisms by which Brn-3b expression may favour breast cancer progression and tumor invasion.