Stachydrine inhibits TGF-β1-induced epithelial-mesenchymal transition in hepatocellular carcinoma cells through the TGF-β/Smad and PI3K/Akt/mTOR signaling pathways

Stachydrine is a bioactive alkaloid that has been found to exert tumor-suppressive potential. However, the effect of stachydrine on hepatocellular carcinoma (HCC) has not been previously investigated. In the present study, we investigated the effect of transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in HepG2 cells. Our results showed that stachydrine significantly suppressed TGF-β1-induced HepG2 cell migration and invasion in a dose-dependent manner. Stachydrine prevented TGF-β1-induced EMT in HepG2 cells, as proved by the increased expression level of E-cadherin and decreased expression levels of N-cadherin and vimentin. In addition, stachydrine attenuated TGF-β1-induced upregulation of TGF-β receptor I (TβRI) in both protein and mRNA levels. Further mechanism investigations proved that stachydrine prevented TGF-β1-induced activation of Smad2/3 and phosphoinositol-3-kinase (PI3K)/Akt/mTOR signaling pathways in HepG2 cells. In conclusion, these findings demonstrated that stachydrine prevented TGF-β1-induced EMT in HCC cells through Smad2/3 and PI3K/Akt/mTOR signaling pathways. Thus, stachydrine might be a potential therapeutic agent for the treatment of HCC.

Overexpression of heat shock protein 70 inhibits epithelial-mesenchymal transition and cell migration induced by transforming growth factor-β in A549 cells

Heat shock protein 70 (HSP70) is a key member of the HSP family that contributes to a pre-cancerous environment; however, its role in lung cancer remains poorly understood. The present study used geranylgeranylacetone (GGA) to induce HSP70 expression, and transforming growth factor-β (TGF-β) was used to construct an epithelial-mesenchymal transition (EMT) model by stimulating A549 cells in vitro. Western Blot was performed to detect protein levels of NADPH oxidase 4 (NOX4) and the EMT-associated proteins E-cadherin and vimentin both before and after HSP70 expression. Cell morphological changes were observed, and the effect of HSP70 on cell migration ability was detected via the wound healing. The results demonstrated that GGA at 50 and 200 μmol/L could significantly induce HSP70 expression in A549 cells (P < 0.05). Furthermore, HSP70 induced by 200 μmol/L GGA significantly inhibited the changes of E-cadherin, vimentin, and cell morphology induced by TGF-β (P < 0.05), while HSP70 induced by 50 μmol/L GGA did not. The results of the wound healing assay indicated that 200 μmol/L GGA significantly inhibited A549 cell migration induced by TGF-β. Taken together, the results of the present study demonstrated that overexpression of HSP70 inhibited the TGF-β induced EMT process and changed the cell morphology and migratory ability induced by TGF-β in A549 cells.

Evodiamine inhibits vasculogenic mimicry in HCT116 cells by suppressing hypoxia-inducible factor 1-alpha-mediated angiogenesis

Evodiamine (Evo), a quinazoline alkaloid and one of the most typical polycyclic heterocycles, is mainly isolated from Evodia rugulosa. Vasculogenic mimicry (VM) is a newly identified way of angiogenesis during tumor neovascularization, which is prevalent in a variety of highly invasive tumors. The purpose of this study was to investigate the effect and mechanism of Evo on VM in human colorectal cancer (CRC) cells. The number of VM structures was calculated by the three-dimensional culture of human CRC cells. Wound-healing was used to detect the migration of HCT116 cells. Gene expression was detected by reverse transcription-quantitative PCR assay. CD31/PAS staining was used to identify VM. Western blotting and immunofluorescence were used to detect protein levels. The results showed that Evo inhibited the migration of HCT116 cells, as well as the formation of VM. Furthermore, Evo reduced the expression of hypoxia-inducible factor 1-alpha (HIF-1α), VE-cadherin, VEGF, MMP2, and MMP9. In a model of subcutaneous xenotransplantation, Evo also inhibited tumor growth and VM formation. Our study demonstrates that Evo could inhibit VM in CRC cells HCT116 and reduce the expression of HIF-1α, VE-cadherin, VEGF, MMP2, and MMP9.

Dissecting the Cellular Mechanism of Prostacyclin Analog Iloprost in Reversing Vascular Dysfunction in Scleroderma

OBJECTIVE

Intravenous iloprost improves Raynaud's phenomenon (RP) and promotes healing of digital ulcers in systemic sclerosis (SSc; scleroderma). Despite a short half-life, its clinical efficacy lasts weeks. Endothelial adherens junctions, which are formed by VE-cadherin clustering between endothelial cells (ECs), regulate endothelial properties including barrier function, endothelial-to-mesenchymal transition (EndoMT), and angiogenesis. We undertook this study to investigate the hypothesis that junctional disruption contributes to vascular dysfunction in SSc, and that the protective effect of iloprost is mediated by strengthening of those junctions.

METHODS

Dermal ECs from SSc patients and healthy controls were isolated. The effect of iloprost on ECs was examined using immunofluorescence, permeability assays, Matrigel tube formation, and quantitative polymerase chain reaction.

RESULTS

Adherens junctions in SSc were disrupted compared to normal ECs, as indicated by reduced levels of VE-cadherin and increased permeability in SSc ECs (P < 0.05). Iloprost increased VE-cadherin clustering at junctions and restored junctional levels of VE-cadherin in SSc ECs (mean ± SD 37.3 ± 4.3 fluorescence units) compared to normal ECs (mean ± SD 29.7 ± 3.4 fluorescence units; P < 0.05), after 2 hours of iloprost incubation. In addition, iloprost reduced permeability of monolayers, increased tubulogenesis, and blocked EndoMT in both normal and SSc ECs (n ≥ 3; P < 0.05). The effects in normal ECs were inhibited by a function-blocking antibody that prevents junctional clustering of VE-cadherin.

CONCLUSION

Our data suggest that the long-lasting effects of iloprost reflect its ability to stabilize adherens junctions, resulting in increased tubulogenesis and barrier function and reduced EndoMT. These findings provide a mechanistic basis for the use of iloprost in treating SSc patients with RP and digital ulcers.

Rikkunshito attenuates induction of epithelial-mesenchymal switch via activation of Sirtuin1 in ovarian cancer cells

Rikkunshito, a traditional Japanese herbal medicine, improves appetite via activation of gastrointestinal hormone ghrelin pathway. The function of ghrelin is mediated by growth hormone secretagogue receptor (GHSR1a), and ghrelin has been known to possess diverse physiological functions including growth suppression of some cancer cells. Considering that increased ghrelin signaling by Rikkunshito could enhance sirtuin1 (SIRT1) activity in nervous system, we aimed to investigate the effect of Rikkunshito in ovarian cancer cells. Ovarian cancer cell lines were treated with Rikkunshito, and cellular viability, gene expressions and epithelial-mesenchymal transition (EMT) status were investigated. To investigate the involvement of SIRT1 by Rikkunshito in SKOV3 cancer cells, endogenous expression of SIRT1 was depleted using small interfering RNA (siRNA). Treatment with Rikkunshito elevated ghrelin, GHSR1a and SIRT1, while cellular viability was decreased. The treatment of Rikkunshito also inhibited cellular migration and invasion status in a dose-dependent manner, and these effects were translated to the enhanced EMT status, although the role of SIRT1 was not determined. Our study revealed a novel function of Rikkunshito in enhancing EMT status of ovarian cancer cells. Therefore, we would like to propose that Rikkunshito may be used as a novel adjunctive therapy in chemotherapy of ovarian cancer because platinum-based chemotherapy frequently used for the treatment of ovarian cancer inevitably impairs appetite.

Fucosyltransferase 2 induced epithelial-mesenchymal transition via TGF-β/Smad signaling pathway in lung adenocarcinaoma

Fucosyltransferase 2 (FUT2), the enzyme catalyzing α-1,2-fucosylation in mammals, has been implicated in cancer. The up-regulation of FUT2 has been observed in lung adenocarcinoma (LUAD), and FUT2 can enhance the cell migration and invasion of LUAD cell lines. However, the underlying mechanism of FUT2 in LUAD remains largely unknown. Abundant studies have revealed that epithelial-mesenchymal transition (EMT) played a pivotal role during lung cancer metastasis and progression. In the present study, we showed that knocking down FUT2 in LUAD cell lines increased the expression of E-cadherin and reduced the expression of Vimentin, N-cadherin, TβRII, p-Smad2, p-Smad3 and Snail, which were the makers of EMT. Meanwhile, the expression of E-cadherin was decreased, and the expression of Vimentin was increased by restoring the expression of FUT2 in RNA interference FUT2 (RNAi-FUT2) cells, suggesting that FUT2 enhanced the EMT process in LUAD. Additionally, silencing FUT2 expression can up-regulate E-cadherin and down-regulate Vimentin, significantly attenuated EMT in vivo. Treated with the SIS3, a new-type inhibitor of p-Smad3 of TGF-β signaling, the expression of E-cadherin, Vimentin and Snail were not affected by RNAi-FUT2 cells, indicating that the effect of FUT2 on EMT depended on TGF-β/Smad signaling. Overall, the current results indicated that FUT2 might promote LUAD metastasis through the EMT initiated by TGF-β/Smad signaling. Therefore, FUT2 might be a prognostic factor and therapeutic target for LUAD.

Vitamin D Attenuates Endothelial Dysfunction in Uremic Rats and Maintains Human Endothelial Stability

Background Dysfunctional endothelium may contribute to the development of cardiovascular complications in chronic kidney disease ( CKD ). Supplementation with active vitamin D has been proposed to have vasoprotective potential in CKD , not only by direct effects on the endothelium but also by an increment of α-Klotho. Here, we explored the capacity of the active vitamin D analogue paricalcitol to protect against uremia-induced endothelial damage and the extent to which this was dependent on increased α-Klotho concentrations. Methods and Results In a combined rat model of CKD with vitamin D deficiency, renal failure induced vascular permeability and endothelial-gap formation in thoracic aorta irrespective of baseline vitamin D, and this was attenuated by paricalcitol. Downregulation of renal and serum α-Klotho was found in the CKD model, which was not restored by paricalcitol. By measuring the real-time changes of the human endothelial barrier function, we found that paricalcitol effectively improved the recovery of endothelial integrity following the addition of the pro-permeability factor thrombin and the induction of a wound. Furthermore, immunofluorescence staining revealed that paricalcitol promoted vascular endothelial-cadherin-based cell-cell junctions and diminished F-actin stress fiber organization, preventing the formation of endothelial intracellular gaps. Conclusions Our results demonstrate that paricalcitol attenuates the CKD -induced endothelial damage in the thoracic aorta and directly mediates endothelial stability in vitro by enforcing cell-cell interactions.

[Effect of a novel EZH2 inhibitor GSK126 on prostate cancer cells]

Objective: To investigate the effect of a novel EZH2 inhibitor GSK126 on cell growth, apoptosis and migration of prostate cancer cells. Methods: Prostate cancer PC-3 and DU145 cells were treated with GSK126 at different doses. Cell growth was detected by sulforhodamine assay. Cell apoptosis was assayed by Annexin V-/PI kit. Transwell chamber and wound healing assays were conducted to detect cell migration. The mRNA level was detected by quantitative PCR, and protein expression was detected by Western blot analysis. Results: GSK126 showed significant effect on cell growth and apoptosis when the dose was higher than 50 μmol/L. Wound healing assay revealed that scratch space in PC-3 cells was significantly increased in a dose-dependent manner in GSK126-treated groups[(247.2±24.4),(347.2±19.2) and (410.5±18.1) μm in low, medium and high dose (5.0, 20.0, 50.0 μmol/L), respectively] as compared with the control group[(171.3±17.8) μm](all P<0.05). Transwell assay showed that migrated PC-3 cells in control group was 322.0±17.9,while those in GSK126-treated groups were 198.3±15.4 (low),82.7±6.2 (medium) and 30.2±4.1 (high), and the differences between the control group and GSK126-treated groups were significant(all P<0.05). In addition, GSK126 up-regulated E-cadherin mRNA expression and down-regulated N-cadherin and Vimentin mRNA expression, whereas had no significant effect on Snail, Fibronectin and VEGF-A mRNA expression. The protein expression of E-cadherin was elevated but VEGF-A protein did not change in GSK126-treated groups. Similar results were exhibited in DU145 cell. Conclusion: GSK126 can significantly inhibit cell migration and invasion in prostate cancer PC-3 and DU145 cells, which may be resulted from its effect on epithelial-mesenchymal transition. GSK126 may be used as a potential anti-prostate cancer dug in clinic.

Effect of estrogen on growth and apoptosis in esophageal adenocarcinoma cells

The epidemiology of esophageal adenocarcinoma demonstrates a strong gender bias with a sex ratio of 8-9:1 in favor of males. A potential explanation for this is that estrogen might protect against esophageal adenocarcinoma. Estrogen has previously been shown to stimulate apoptosis in esophageal squamous cancer cells. However, the effect of estrogen on esophageal adenocarcinoma cells has not been determined. We used immunoblotting analysis to determine the expression of estrogen receptors, cell adhesion marker E-cadherin, and proliferation marker Ki-67 in cell lines derived from esophageal adenocarcinoma (OE-19, OE-33) and Barrett's esophagus (QhTRT, ChTRT, GihTRT). Estrogen and selective estrogen receptor modulator (SERM)-dependent effects on cell growth were determined by the CellTiter-96 Aqueous Proliferation Assay. Apoptosis was determined by Annexin V/Propidium Iodide cell labeling and flow cytometry. We detected that physiological and supra-physiological concentrations of 17β-estradiol and SERM decreased cell growth in esophageal adenocarcinoma cells. In Barrett's esophagus cells (QhTRT, ChTRT), decreased growth was also detected in response to estrogen/SERM. The level of estrogen receptor expression in the cell lines correlated with the level of anti-growth effects induced by the receptor agonists. Flow cytometry analysis confirmed estrogen/SERM stimulated apoptosis in esophageal adenocarcinoma cells. Estrogen/SERM treatments were associated with a decrease in the expression of Ki-67 and an increase in E-cadherin expression in esophageal adenocarcinoma cells. This study suggests that esophageal adenocarcinoma and Barrett's esophagus cells respond to treatment with selective estrogen receptor ligands, resulting in decreased cell growth and apoptosis. Further research to explore potential therapeutic applications is warranted.

β-Catenin regulates deiodinase levels and thyroid hormone signaling in colon cancer cells

BACKGROUND & AIMS

Activation of the β-catenin/T-cell factor (TCF) complex occurs in most colon tumors, and its actions correlate with the neoplastic phenotype of intestinal epithelial cells. Type 3 deiodinase (D3), the selenoenzyme that inactivates thyroid hormone (3,5,3' triiodothyronine [T3]), is frequently expressed by tumor cells, but little is known about its role in the regulation of T3 signaling in cancer cells.

METHODS

We measured D3 expression in 6 colon cancer cell lines and human tumors and correlated it with the activity of the β-catenin/TCF complex. We also determined the effects of D3 loss on local thyroid hormone signaling and colon tumorigenesis.

RESULTS

We show that D3 is a direct transcriptional target of the β-catenin/TCF complex; its expression was higher in human intestinal adenomas and carcinomas than in healthy intestinal tissue. Experimental attenuation of β-catenin reduced D3 levels and induced type 2 deiodinase (the D3 antagonist that converts 3,5,3',5' tetraiodothyronine into active T3) thereby increasing T3-dependent transcription. In the absence of D3, excess T3 reduced cell proliferation and promoted differentiation in cultured cells and in xenograft mouse models. This occurred via induction of E-cadherin, which sequestered β-catenin at the plasma membrane and promoted cell differentiation.

CONCLUSIONS

Deiodinases are at the interface between the β-catenin and the thyroid hormone pathways. Their synchronized regulation of intracellular T3 concentration is a hitherto unrecognized route by which the multiple effects of β-catenin are generated and may be targeted to reduce the oncogenic effects of β-catenin in intestinal cells.

Rac1 and RhoA GTPases have antagonistic functions during N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts

BACKGROUND INFORMATION

N-cadherin, a member of the Ca(2+)-dependent cell-cell adhesion molecule family, plays an essential role in the induction of the skeletal muscle differentiation programme. However, the molecular mechanisms which govern the formation of N-cadherin-dependent cell-cell contacts in myoblasts remain unexplored.

RESULTS

In the present study, we show that N-cadherin-dependent cell contact formation in myoblasts is defined by two stages. In the first phase, N-cadherin is highly mobile in the lamellipodia extensions between the contacting cells. The second stage corresponds to the formation of mature N-cadherin-dependent cell contacts, characterized by the immobilization of a pool of N-cadherin which appears to be clustered in the interdigitated membrane structures that are also membrane attachment sites for F-actin filaments. We also demonstrated that the formation of N-cadherin-dependent cell-cell contacts requires a co-ordinated and sequential activity of Rac1 and RhoA. Rac1 is involved in the first stage and facilitates N-cadherin-dependent cell-cell contact formation, but it is not absolutely required. Conversely, RhoA is necessary for N-cadherin-dependent cell contact formation, since, via ROCK (Rho-associated kinase) signalling and myosin 2 activation, it allows the stabilization of N-cadherin at the cell-cell contact sites.

CONCLUSIONS

We have shown that Rac1 and RhoA have opposite effects on N-cadherin-dependent cell-cell contact formation in C2C12 myoblasts and act sequentially to allow its formation.

Diesel exhaust particle exposure causes redistribution of endothelial tube VE-cadherin

Whether diesel exhaust particles (DEPs) potentially have a direct effect on capillary endothelia was examined by following the adherens junction component, vascular endothelial cell cadherin (VE-cadherin). This molecule is incorporated into endothelial adherens junctions at the cell surface, where it forms homodimeric associations with adjacent cells and contributes to the barrier function of the vasculature (Dejana et al., 2008; Venkiteswaran et al., 2002; Villasante et al., 2007). Human umbilical vein endothelial cells (HUVECs) that were pre-formed into capillary-like tube networks in vitro were exposed to DEPs for 24h. After exposure, the integrity of VE-cadherin in adherens junctions was assessed by immunofluorescence analysis, and demonstrated that increasing concentrations of DEPs caused increasing redistribution of VE-cadherin away from the cell-cell junctions toward intracellular locations. Since HUVEC tube networks are three-dimensional structures, whether particles entered the endothelial cells or tubular lumens was also examined. The data indicate that translocation of the particles does occur. The results, obtained in a setting that removes the confounding effects of inflammatory cells or blood components, suggest that if DEPs encounter alveolar capillaries in vivo, they may be able to directly affect the endothelial cell-cell junctions.

Distinct Patterns of Microvascular Endothelial Cell Morphology Are Determined by Extracellular Matrix Composition

Endothelial interactions with the extracellular matrix (ECM) play important roles in angiogenesis but whether specific ECM signals can determine specific cellular morphologies is unclear. The authors compared in vitro ECM-induced morphological responses of the phenotypically distinct human placental microvascular endothelial cells (HPMECs) with large vessel endothelial cells (HUVECs). HPMECs showed distinct patterns of reorganization in response to collagen-I or collagen-IV (monolayer disruption, sprouting, migration) and Matrigel or laminin-A (intussusception, cord formation, tubulogenesis), and an intermediate response to fibrin; whereas HUVECs responded similarly to collagen-1 and Matrigel (elongation, lattice formation, vacuolation) and showed little response to fibrin. Although the extent of collagen and Matrigel responses of HPMECs were increased by serum, acidic or basic fibroblast growth factor (aFGF, bFGF), or vascular endothelial growth factor (VEGF), and varied with matrix protein concentration, the basic patterns were matrix specific, and were independent of fibronectin. The collagen responses correlated with disruption of adherens and tight junctions and the formation of filopodial protrusions. Matrigel responses were associated with up-regulated junctional localization of VE-cadherin, and tubulogenesis developed mainly through paracellular remodeling rather than intracellular vacuolation. Overall, these findings suggest that distinct ECM interactions stimulate specific morphological responses. These signals may regulate morphological behaviour in the angiogenesis cycle, switching endothelial cells between migratory and vasculogenic phenotypes.

Interferon (IFN)-ß1a and IFN-ß1b Block IFN-?-Induced Disintegration of Endothelial Junction Integrity and Barrier

Recent clinical trials indicate the efficacy of interferon (IFN)-beta 1b in reducing relapse rate in relapsing-remitting multiple sclerosis (MS), whereas a surge of IFN-gamma precedes and provokes acute relapses. Disruption of the cerebral endothelial barrier and transendothelial migration of inflammatory cell migration into the brain play a significant role in pathogenesis of MS and may be driven by this surge in IFN-gamma. However, the molecular mechanisms underlying the beneficial effects of IFN-beta 1b against the deleterious effects of IFN-gamma on the barrier formed by the junctional proteins remain to be characterized. The authors investigated the effects of IFN-beta 1b, IFN-beta 1a, and IFN-gamma on the integrity of two endothelial junctional proteins, occludin and vascular endothelial-cadherin (VE-cadherin). Human umbilical vein endothelial cell (HUVEC) layers were treated with IFN-beta 1b, IFN-beta 1a, IFN-gamma, IFN-beta 1b plus IFN-gamma, or IFN-beta 1a plus IFN-gamma. IFN-beta 1b, IFN-beta 1a, and IFN-gamma effects on occludin and VE-cadherin integrity and electrical resistance were assessed by Western blotting and immunofluorescence. IFN-gamma significantly reduced occludin expression and produced gaps in endothelial monolayers. VE-cadherin expression was decreased to a lesser extent in endothelial cells exposed to IFN-gamma. IFN-beta 1b significantly attenuated the IFN-gamma-induced decrease in occludin and VE-cadherin expression. The protective effects of IFN-beta 1a on IFN-gamma-treated endothelial cells were similar to those of IFN-beta 1b. IFN-gamma also significantly reduced endothelial monolayer electrical resistance; this effect was blocked by either IFN-beta 1a or IFN-beta 1b. IFN-beta 1a and IFN-beta 1b effectively prevent the IFN-gamma-induced disintegration of the endothelial tight junctions and sustain barrier against the effects of IFN-gamma. The protective effects of IFN-beta on occludin and VE-cadherin stability appear to represent molecular mechanisms for the therapeutic effects of the IFN-beta on blood brain barrier in MS.

Modifying influence of prolonged action of interferon on phenotypic characteristics of human lung cancer cells in vitro

AIM

To study modifying influence of interferon (IFN) on some phenotypic properties of human non-small-cell lung cancer cells (NSCLC) upon prolonged exposition of the cells with IFN.

MATERIALS AND METHODS

A-549 cells were cultivated with IFN at increasing concentrations for a long period of time (up to 1 year). Cell morphology and ultrastructure were studied by light and electron microscopy. Expression of adhesion protein E-cadherin, and vimentin, cytosceleton protein associated with tumor cell migration and invasion, antigen of proliferating cells Ki-67, angiogenesis-stimulating protein VEGF were studied using the method of immunocytochemistry. Autonomity of the cell growth was studied with the use of colony formation in soft agar, platting efficiency assay, and growth in serum-free medium.

RESULTS

It has been shown that prolonged action of IFN results in significant and irreversible inhibition of manifestation of malignant phenotype: decreased of proliferative potential and inhibited autonomy of the cells; in complicated cell ultrastructure; in decreased expression vimentin and in increased expression of E-cadherin. Also, an inhibiting influence of IFN on expression of EGF receptors and VEGF in tumor cells have been shown.

CONCLUSIONS

The data are showing that prolonged exposition of NSCLC cells to IFN is accompanied by stable phenotypic alterations of the cells directed on significant loss of malignancy and their shift to more differentiated phenotype.

Ether lipid 1-O-octadecyl-2-O-methyl-3-glycero-phosphocholine inhibits cell-cell adhesion through translocation and clustering of E-cadherin and episialin in membrane microdomains

The ether lipid 1-O-octadecyl-2-O-methyl-3-glycero-phosphocholine (ET-18-OMe) inhibits cell-cell adhesion and induces invasiveness of breast cancer cells. Previously, we showed that a loss of cell-cell adhesion was due to sterical hindrance of E-cadherin by the anti-adhesive properties of the cell surface mucin episialin. Here, we demonstrated that the ether lipid ET-18-OMe induced the translocation of E-cadherin and episialin to membrane microdomains, enriched in glycosphingolipids, known to be involved in cell-cell adhesion and cell signaling. In addition, it was found that E-cadherin and clusters of episialin colocalized and associated with the glycosphingolipid, MSGb5, upon treatment with ET-18-OMe. Together, these results suggest that ET-18-OMe inhibits cell-cell adhesion by inducing the translocation of E-cadherin and episialin into MSGb5-enriched membrane microdomains, which leads to clustering and colocalization of the pro-adhesive E-cadherin and the anti-adhesive episialin thereby inhibiting cell-cell adhesion.

Activation of FOXO3a by the green tea polyphenol epigallocatechin-3-gallate induces estrogen receptor alpha expression reversing invasive phenotype of breast cancer cells

Previously, we showed that the bioactive green tea polyphenol epigallocatechin-3-gallate (EGCG) inhibits growth in soft agar of breast cancer cells with Her-2/neu overexpression. Using gene expression profiling, here we show that EGCG treatment of Her-2/neu-driven mammary tumor cells alters the expression of key regulators in the epithelial to mesenchymal transition (EMT) pathway, reducing invasive phenotype. Specifically, the epithelial genes E-cadherin, gamma-catenin, MTA3, and estrogen receptor alpha (ERalpha) were up-regulated by EGCG, whereas the proinvasive snail gene was down-regulated. Consistently, EGCG inhibited branching colony growth and invasion in Matrigel. EGCG treatment similarly inhibited invasive phenotype of mouse mammary tumor cells driven by Nuclear Factor-kappaB c-Rel and protein kinase CK2, frequently found overexpressed in human breast disease. Recently, we identified the Forkhead box O transcription factor FOXO3a as a major transcriptional regulator of ERalpha. Given the pivotal role of ERalpha in preventing EMT, we hypothesized that the activation of FOXO3a by EGCG plays an important role in the observed reversal of invasive phenotype in ERalpha-positive breast cancer cells. EGCG treatment activated FOXO3a. Ectopic expression of a constitutively active FOXO3a overrode transforming growth factor-beta1-mediated invasive phenotype and induced a more epithelial phenotype, which was dependent on ERalpha expression and signaling. Conversely, a dominant negative FOXO3a reduced epithelial phenotype of ERalpha-low breast cancer cells. These results identify, for the first time, a role for FOXO3a in the inhibition of invasive phenotype in breast cancer cells with active ERalpha signaling and elucidate a novel mechanism whereby EGCG represses EMT of breast cancer cells.

Possible involvement of SDF-1α/CXCR4-DPPIV axis in TGF-β1-induced enhancement of migratory potential in human peritoneal mesothelial cells

We have previously reported that human peritoneal mesothelial cells (HPMCs) express a large amount of dipeptidyl peptidase IV (DPPIV) and that its expression is regulated by a variety of bioactive substances in malignant ascites from ovarian cancer patients. The aim of this study has been to examine the expression and role of the SDF-1alpha/CXCR4-DPPIV axis in HPMCs. We have demonstrated that the expression levels of DPPIV and E-cadherin in HPMCs decrease, following TGF-beta1-induced morphological change, in a time- and concentration-dependent manner. Additionally, we show that both SDF-1alpha (a chemokine and substrate for DPPIV) and its receptor, CXCR4, are expressed on HPMCs, and that their expression levels are upregulated by TGF-beta1 treatment, resulting in an increased migratory potential of HPMCs. Furthermore, the migratory potential of HPMCs is significantly enhanced in the presence of SDF-1alpha or DPPIV-specific inhibitor in the wound-healing assay. These results suggest that DPPIV and SDF-1alpha/CXCR4 play crucial roles in regulating the migratory potential of HPMCs, which may be involved in the re-epithelialization of denuded basement membrane at the site of peritoneal injury.

Dual effects of sodium lauryl sulphate on human oral epithelial structure

Sodium lauryl sulphate (SLS) is a common detergent known to cause irritation and inflammatory reactions in skin. SLS is also the most commonly used toothpaste detergent and has been related to intraoral adverse effects. However, its specific biological effects on the oral mucosa (OM) have not yet been identified. The objective of this study was to investigate the putative effects of SLS on human oral epithelium using a novel in vitro reconstructed three-dimensional cell culture model. Reconstructed human OM, generated from primary normal human oral keratinocytes and fibroblasts, was exposed to clinically relevant concentrations of SLS (range 0.015-1.5%). The cultured tissues were evaluated by histomorphometry, immunohistochemistry (Ki-67, epithelial (E)-cadherin, alpha6-, beta1-integrins, cleaved caspase-3) and the TUNEL method. Increased epithelial thickness, enhanced proliferation (Ki-67), a more pronounced expression of E-cadherin throughout all epithelial cell layers and single TUNEL-positive cells in the middle spinous cell layers were observed in cultures exposed to low concentrations (0.015%) of SLS. At exposure to higher SLS concentrations (>or=0.15%), epithelial thickness, cell proliferation and E-cadherin expression gradually decreased and in the central areas of exposed regions, cells detached from each other and underwent cell death. In conclusion, clinically relevant concentrations of SLS have dual effects on reconstituted human OM; although occasional cell death within the epithelium was also observed, the increased epithelial thickness, proliferation and E-cadherin expression induced at lower concentrations might be associated with a protective mucosal response, whereas at higher concentrations a more destructive type of reaction predominated.

Clostridium sordellii lethal toxin kills mice by inducing a major increase in lung vascular permeability

When intraperitoneally injected into Swiss mice, Clostridium sordellii lethal toxin reproduces the fatal toxic shock syndrome observed in humans and animals after natural infection. This animal model was used to study the mechanism of lethal toxin-induced death. Histopathological and biochemical analyses identified lung and heart as preferential organs targeted by lethal toxin. Massive extravasation of blood fluid in the thoracic cage, resulting from an increase in lung vascular permeability, generated profound modifications such as animal dehydration, increase in hematocrit, hypoxia, and finally, cardiorespiratory failure. Vascular permeability increase induced by lethal toxin resulted from modifications of lung endothelial cells as evidenced by electron microscopy. Immunohistochemical analysis demonstrated that VE-cadherin, a protein participating in intercellular adherens junctions, was redistributed from membrane to cytosol in lung endothelial cells. No major sign of lethal toxin-induced inflammation was observed that could participate in the toxic shock syndrome. The main effect of the lethal toxin is the glucosylation-dependent inactivation of small GTPases, in particular Rac, which is involved in actin polymerization occurring in vivo in lungs leading to E-cadherin junction destabilization. We conclude that the cells most susceptible to lethal toxin are lung vascular endothelial cells, the adherens junctions of which were altered after intoxication.

Tumor necrosis factor-alpha damages tumor blood vessel integrity by targeting VE-cadherin

BACKGROUND

Isolated limb perfusion using high-dose human tumor necrosis factor-alpha with melphalan is effective therapy for bulky extremity in-transit melanoma and sarcoma.

OBJECTIVE

While it is widely accepted that melphalan is a DNA alkylating agent, the mechanism of selective antitumor effect of tumor necrosis factor-alpha is unclear.

METHODS AND RESULTS

Electron microscopic analyses of human melanoma biopsies, pre- and post-melphalan perfusion, showed that the addition of tumor necrosis factor-alpha caused gapping between endothelial cells by 3 to 6 hours post-treatment followed by vascular erythrostasis in treated tumors. In human melanoma xenografts raised in mice, tumor necrosis factor-alpha selectively increased tumor vascular permeability by 3 hours and decreased tumor blood flow by 6 hours post-treatment relative to treated normal tissue. In an in vitro tumor endothelial cell model, tumor necrosis factor-alpha caused vascular endothelial adherens junction protein, VE-cadherin, to relocalize within the cell membrane away from cell-cell junctions leading to gapping between endothelial cells by 3 to 6 hours post-treatment. Phosphotyrosinylation was a prerequisite for movement of VE-cadherin away from endothelial cell junctions and for gapping between endothelial cells. Clinical isolated limb perfusion tumor specimens, at 3 hours postperfusion, showed a discontinuous and irregular pattern of VE-cadherin expression at endothelial cell junctions when compared with normal (skin) or pretreatment tumor tissue.

CONCLUSIONS

Together, the data suggest that tumor necrosis factor-alpha selectively damages the integrity of tumor vasculature by disrupting VE-cadherin complexes at vascular endothelial cell junctions leading to gapping between endothelial cells, causing increased vascular leak and erythrostasis in tumors. VE-cadherin appears to be a potentially good target for selective antitumor therapy.

Chemoprevention of colon carcinogenesis by polyethylene glycol: suppression of epithelial proliferation via modulation of SNAIL/beta-catenin signaling

Polyethylene glycol (PEG) is one of the most potent chemopreventive agents against colorectal cancer; however, the mechanisms remain largely unexplored. In this study, we assessed the ability of PEG to target cyclin D1-beta-catenin-mediated hyperproliferation in the azoxymethane-treated rat model and the human colorectal cancer cell line, HT-29. Azoxymethane-treated rats were randomized to AIN-76A diet alone or supplemented with 5% PEG-8000. After 30 weeks, animals were euthanized and biopsies of aberrant crypt foci and uninvolved crypts were subjected to immunohistochemical and immunoblot analyses. PEG markedly suppressed both early and late markers of azoxymethane-induced colon carcinogenesis (fractal dimension by 80%, aberrant crypt foci by 64%, and tumors by 74%). In both azoxymethane-treated rats and HT-29 cells treated with 5% PEG-3350 for 24 hours, PEG decreased proliferation (45% and 52%, respectively) and cyclin D1 (78% and 56%, respectively). Because beta-catenin is the major regulator of cyclin D1 in colorectal cancer, we used the T-cell factor (Tcf)-TOPFLASH reporter assay to show that PEG markedly inhibited beta-catenin transcriptional activity. PEG did not alter total beta-catenin expression but rather its nuclear localization, leading us to assess E-cadherin expression (a major determinant of beta-catenin subcellular localization), which was increased by 73% and 71% in the azoxymethane-rat and HT-29 cells, respectively. We therefore investigated the effect of PEG treatment on levels of the negative regulator of E-cadherin, SNAIL, and observed a 50% and 75% decrease, respectively. In conclusion, we show, for the first time, a molecular mechanism through which PEG imparts its antiproliferative and hence profound chemopreventive effect.

The C-terminal region of Bacteroides fragilis toxin is essential to its biological activity

To evaluate the role of the C-terminal region in Bacteroides fragilis toxin (BFT) activity, processing, and secretion, sequential C-terminal truncation and point mutations were created by site-directed mutagenesis. Determination of BFT activity on HT29/C1 cells, cleavage of E-cadherin, and the capacity to induce interleukin-8 secretion by wild-type BFT and C-terminal deletion mutants showed that deletion of only 2 amino acid residues at the C terminus significantly reduced BFT biological activity and deletion of eight or more amino acid residues obliterated BFT biologic activity. Western blot and reverse transcription-PCR analyses indicated that BFT mutants lacking seven or fewer amino acid residues in the C-terminal region are processed and expressed similar to wild-type BFT. However, BFT mutants lacking eight or more amino acids at the C terminus are expressed similar to wild-type BFT but are unstable. We concluded that the C terminus of BFT is not tolerant of modest amino acid deletions, suggesting that it is biologically important for BFT activity.

The influence of tamoxifen on growth behavior and cell-cell adhesion in OSCC in vitro

The aim of this study was to evaluate the influence of tamoxifen on the growth and aggregation behavior, focusing on the expression pattern of E-cadherin and beta-catenin, in oral squamous cell carcinoma (OSCC) in vitro. Oral squamous cancer cell lines (UM-SCC-14A, UM-SCC-14B and UM-SCC-14C) were treated with various concentrations of tamoxifen. Growth and aggregation behavior as well as the protein expression and its changes were analysed. All cell lines are estrogen receptor (ER) positive. Tamoxifen induced a significant growth inhibition and induced the ability to form cell aggregates. This phenomena was not accompanied by a change in E-cadherin or beta-catenin expression or due to transcriptional changes. beta-catenin showed isolated membrane staining and nuclear distribution in all cell lines. A defective Ecadherin/beta-catenin complex was seen in UM-SCC-14C with no restoration through tamoxifen treatment. The cell-cell formation is increased in all cell lines without any alterations in the functional and quantitative status of E-cadherin or beta-catenin, indicating that novel cell-cell adhesion complexes not involving the classical E-cadherin/beta-catenin influence cell growth and intercellular adhesion in OSCC.

Paricalcitol attenuates renal interstitial fibrosis in obstructive nephropathy

Deficiency in vitamin D and its active metabolites is a pathologic feature of chronic kidney diseases. Despite that tubular epithelial cells are the major sites of active vitamin D synthesis, little is known about the role of vitamin D in maintaining the structural and functional integrity of tubular epithelium. This study investigated the effects of paricalcitol (19-nor-1,25-hydroxy-vitamin D(2)), a synthetic vitamin D analogue, on obstructive nephropathy, a model that is characterized by predominant tubulointerstitial lesions. Compared with vehicle controls, paricalcitol significantly attenuated renal interstitial fibrosis in mouse kidney after ureteral obstruction, as demonstrated by a reduced interstitial volume, decreased collagen deposition, and repressed mRNA expression of fibronectin and type I and type III collagens. Paricalcitol largely preserved E-cadherin and reduced alpha-smooth muscle actin expression in vivo. In addition, paricalcitol suppressed renal TGF-beta1 and its type I receptor expression, restored vitamin D receptor abundance, and inhibited cell proliferation and apoptosis after obstructive injury. In vitro, paricalcitol abolished TGF-beta1-mediated E-cadherin suppression and alpha-smooth muscle actin and fibronectin induction in tubular epithelial cells, underscoring its ability to block directly the epithelial to mesenchymal transition (EMT). It is interesting that paricalcitol almost completely suppressed renal induction of Snail, a critical transcription factor that is implicated in EMT programming. Furthermore, paricalcitol inhibited the TGF-beta1-mediated Snail induction in vitro, and ectopic expression of Snail repressed E-cadherin promoter activity and downregulated E-cadherin expression in tubular epithelial cells. These studies suggest that paricalcitol is able to ameliorate renal interstitial fibrosis in obstructive nephropathy, possibly by preserving tubular epithelial integrity through suppression of EMT.

Regionalized cadherin-7 expression by radial glia is regulated by Shh and Pax7 during chicken spinal cord development

During development, several genes that specify neuronal subtype identity are expressed in distinct dorsoventral domains of the spinal cord and hindbrain. Cadherin-7 (Cad7), a member of the cadherin family of adhesion molecules, is expressed by radial glia in a dorsal domain of the spinal cord basal plate in chicken. To study the regulation of the Cad7 gene, we ectopically expressed two known dorsoventral patterning genes, Shh and Pax7, in the caudal neural tube and in two brain regions at different stages of development by in vivo electroporation. Results showed that Shh regulated the expression of Cad7 by radial glia in a concentration-dependent manner. Shh induced or repressed the expression of Cad7, at low and high concentrations, respectively. Furthermore, Pax7 inhibited the expression of Cad7. These results are compatible with a role of Shh and Pax7 in regulating endogenous Cad7 expression during spinal cord and hindbrain development. Our data show, for the first time, that Shh can regulate the expression not only of other gene regulatory factors, but also of Cad7, a morphoregulatory molecule that plays a role in axon elongation and neural circuit formation.

TNF-alpha increases tyrosine phosphorylation of vascular endothelial cadherin and opens the paracellular pathway through fyn activation in human lung endothelia

Tumor necrosis factor (TNF)-alpha is a key mediator of sepsis-associated multiorgan failure, including the acute respiratory distress syndrome. We examined the role of protein tyrosine phosphorylation in TNF-alpha-induced pulmonary vascular permeability. Postconfluent human lung microvascular and pulmonary artery endothelial cell (EC) monolayers exposed to human recombinant TNF-alpha displayed a dose- and time-dependent increase in transendothelial [(14)C]albumin flux in the absence of EC injury. TNF-alpha also increased tyrosine phosphorylation of EC proteins, and several substrates were identified as the zonula adherens proteins vascular endothelial (VE)-cadherin, and beta-catenin, gamma-catenin, and p120 catenin (p120(ctn)). Prior protein tyrosine kinase (PTK) inhibition protected against the TNF-alpha effect. TNF-alpha activated multiple PTKs, including src family PTKs. Prior PTK inhibition with the src-selective agents PP1 and PP2 each protected against approximately 60% of the TNF-alpha-induced increment in [(14)C]albumin flux. PP2 also blocked TNF-alpha-induced tyrosine phosphorylation of VE-cadherin, gamma-catenin, and p120(ctn). To identify which src family kinase(s) was required for TNF-alpha-induced vascular permeability, small interfering RNA (siRNA) targeting each of the three src family PTKs expressed in human EC, c-src, fyn, and yes, were introduced into the barrier function assay. Only fyn siRNA protected against the TNF-alpha effect, whereas the c-src and yes siRNAs did not. These combined data suggest that TNF-alpha regulates the pulmonary vascular endothelial paracellular pathway, in part, through fyn activation.

Purification of a novel aminopeptidase from the pollen of Parietaria judaica that alters epithelial integrity and degrades neuropeptides

BACKGROUND

Parietaria judaica pollen is a common cause of pollinosis in the Mediterranean area.

OBJECTIVE

This study sought to purify and characterize the peptidase responsible for the majority of proteolytic activity present in the pollen extract of P judaica, and to investigate its contribution to the allergic response.

METHODS

A serial of chromatographic steps was applied to isolate the peptidase from P judaica's pollen, and its biochemical properties were determined. Bioactive peptides present in the airways were incubated with the peptidase, and their degradation was visualized by direct protein sequencing. In addition, we measured the cellular detachment, by methylene blue binding assay, of an airway-derived epithelial cell line (A549) in the presence of the peptidase, and visualized, by Western blot, the degradation of proteins from intercellular junctions.

RESULTS

We purified a 98-kDa peptidase from the pollen of P judaica that was classified as an aminopeptidase on the basis of its biochemical properties and internal amino acid sequence. The aminopeptidase was able to degrade bioactive peptides. Moreover, the aminopeptidase caused cellular detachment of A549 cell line and degradation of occludin and E-cadherin.

CONCLUSION

Our results suggest that the P judaica aminopeptidase can alter the integrity of the epithelium barrier by degrading occludin as well as E-cadherin. In addition, P judaica aminopeptidase can degrade bioactive peptides, which can exacerbate the overall bronchoconstrictive effect detected in asthmatic lungs.

CLINICAL IMPLICATIONS

The novel aminopeptidase described here could constitute a relevant therapeutic target in the treatment of allergic disorders induced by the pollen of P judaica.

Positional cloning, association analysis and expression studies provide convergent evidence that the cadherin gene FAT contains a bipolar disorder susceptibility allele

A susceptibility locus for bipolar disorder was previously localized to chromosome 4q35 by genetic linkage analysis. We have applied a positional cloning strategy, combined with association analysis and provide evidence that a cadherin gene, FAT, confers susceptibility to bipolar disorder in four independent cohorts (allelic P-values range from 0.003 to 0.024). In two case-control cohorts, association was identified among bipolar cases with a family history of psychiatric illness, whereas in two cohorts of parent-proband trios, association was identified among bipolar cases who had exhibited psychosis. Pooled analysis of the case-control cohort data further supported association (P=0.0002, summary odds ratio=2.31, 95% CI: 1.49-3.59). We localized the bipolar-associated region of the FAT gene to an interval that encodes an intracellular EVH1 domain, a domain that interacts with Ena/VASP proteins, as well as putative beta-catenin binding sites. Expression of Fat, Catnb (beta-catenin), and the three genes (Enah, Evl and Vasp) encoding the Ena/VASP proteins, were investigated in mice following administration of the mood-stabilizing drugs, lithium and valproate. Fat was shown to be significantly downregulated (P=0.027), and Catnb and Enah were significantly upregulated (P=0.0003 and 0.005, respectively), in response to therapeutic doses of lithium. Using a protein interaction map, the expression of genes encoding murine homologs of the FAT (ft)-interacting proteins was investigated. Of 14 interacting molecules that showed expression following microarray analysis (including several members of the Wnt signaling pathway), eight showed significantly altered expression in response to therapeutic doses of lithium (binomial P=0.004). Together, these data provide convergent evidence that FAT and its protein partners may be components of a molecular pathway involved in susceptibility to bipolar disorder.

A pharmacodynamic study of 5-azacytidine in the P39 cell line

OBJECTIVE

5-azacytidine (azacytidine), a DNA hypomethylating agent, was recently approved as the first therapeutic agent for the treatment of myelodysplastic syndromes. The present subcutaneous dosing schedule, 75 mg/m(2) for 7/28 days, is based on early clinical studies and may constitute a practical problem for patients. The present in vitro study aimed at evaluating the pharmacodynamics of azacytidine, thereby providing a rationale for clinical dose-finding studies.

METHODS

P39 cells were incubated with 0.1, 0.5, and 1 microM azacytidine daily for 24, 48, and 72 hours, followed by 48 hours in drug-free medium. The effects of azacytidine on cell growth, proliferation, apoptosis, cell cycle status, and promoter methylation of E-cadherin, ER, and HIC genes were studied.

RESULTS

Azacytidine decreased cell growth and proliferation, increased apoptosis, and affected cell cycle status in a dose-dependent manner. However, the exposure time, 24 to 72 hours, at doses between 0.5 and 1 microM, did not significantly affect any of these variables. Using first-order exponential pharmacokinetic model, we found that the effect of 1, 2, or 3 microM over 24 hours did not differ from that of 0.5 to 1 microM given over 48 to 72 hours. Induction of promoter hypomethylation was observed already after 24 hours of exposure with >or=0.5 microM azacytidine with no clear dose-effect relationship.

CONCLUSION

Our results indicate that optimal cellular effects of azacytidine might be achieved by shorter exposure times. The model provides information about the relation between azacytidine dose intensity and exposure time on malignant myeloid cells, which could serve as a rationale for further clinical development of practical, safe, and cost-effective dosing schedules.

Matrix metalloproteinase inhibitors suppress transforming growth factor-beta-induced subcapsular cataract formation

The pleotropic morphogen transforming growth factor-beta (TGFbeta) plays an important role in the development of fibrotic pathologies, including anterior subcapsular cataracts (ASCs). ASC formation involves increased proliferation and transition of lens epithelial cells into myofibroblasts, through epithelial-mesenchymal transformation that results in opaque plaques beneath the lens capsule. In this study, we used a previously established TGFbeta-induced rat cataract model to explore the role of matrix metalloproteinases (MMPs) in ASC formation. Treatment of excised rat lenses with TGFbeta resulted in enhanced secretion of MMP-2 and MMP-9. Importantly, co-treatment with two different MMP inhibitors (MMPIs), the broad spectrum inhibitor GM6001 and an MMP-2/9-specific inhibitor, suppressed TGFbeta-induced ASC changes, including the epithelial-mesenchymal transformation of lens epithelial cells. Using an anti-E-cadherin antibody, we revealed that conditioned media from lenses treated with TGFbeta contained a 72-kd E-cadherin fragment, indicative of E-cadherin shedding. This was accompanied by attenuated levels of E-cadherin mRNA. Conditioned media from lenses co-treated with TGFbeta and MMPIs exhibited attenuated levels of the E-cadherin fragment compared with those from TGFbeta-treated lenses. Together, these findings demonstrate that TGFbeta-induced E-cadherin shedding in the lens is mediated by MMPs and that suppression of this phenomenon might explain the mechanism by which MMPIs inhibit ASC plaque formation.

Targeted suppression of E-cadherin gene expression in bovine preimplantation embryo by RNA interference technology using double-stranded RNA

RNA interference (RNAi) has become acknowledged as an effective and useful tool to study gene function in diverse groups of cells. We aimed to suppress the expression of the E-cadherin gene during in vitro development of bovine preimplantation embryos using RNAi approach. In this experiment the effect of microinjection of E-cadherin and Oct-4 (as control) double-stranded (ds) RNA on the mRNA and protein expression level of the target E-cadherin gene was investigated. For this, a 496 bp long bovine E-cadherin and 341 bp long Oct-4 dsRNA sample were prepared using in vitro transcription. In vitro produced bovine zygotes were categorized into four treatment groups including those injected with E-cadherin dsRNA, Oct-4 dsRNA, RNase-free water, and uninjected controls. While the injection of E-cadherin dsRNA resulted in the reduction of E-cadherin mRNA and protein levels at the morula and blastocyst stage, the transcript and protein product remained unaffected in the Oct-4 dsRNA, water injected and uninjected control groups. The relative abundance of E-cadherin mRNA in the E-cadherin dsRNA injected morula stage embryos was reduced by 80% compared to the control group (P < 0.05). The Western blot analysis also showed a significant decrease in the E-cadherin protein (119 kDa) in E-cadherin dsRNA injected embryos compared to the other three groups. Microinjection of E-cadherin dsRNA has resulted only 22% blastocyst rate compared to 38%-40% in water injected and uninjected controls. In conclusion, our results indicated the suppression of E-cadherin mRNA and protein has resulted in lower blastocyst rate and the RNAi technology is a promising approach to study the function of genes in early bovine embryogenesis.

Rho GTPase activation by cell-cell adhesion

Cell-cell adhesion can occur in a calcium-dependent or calcium-independent manner, depending on the type of receptor involved. Establishment of cell contacts by either type of cell-cell adhesion (calcium-dependent or calcium-independent) has been shown to activate Rho GTPases in different cells. In this chapter, we describe the method used to assess the activation of Rho GTPases by cadherins, the prototype calcium-dependent adhesion receptor in epithelial cells. We cover the optimal cell culture conditions and controls to ensure that the activation of the GTPases is specifically triggered by the formation of cadherin-dependent cell-cell contacts. Controls described herein determine the specificity of activation of Rho proteins with respect to cadherin adhesion and exclude the contribution of other adhesive receptors, calcium-signaling, cell spreading, and migration. Although we focus on cadherin receptors and normal human keratinocytes as our model system, the methods described can be easily adapted to other adhesion receptors and different cell types.

Modulation of E-cadherin by hepatocyte growth factor induces aggressiveness of gastric carcinoma

OBJECTIVE

Hepatocyte growth factor (HGF) is well known as a scatter factor because it can disperse cells. E-cadherin is a protein that plays a main role in the establishment of cell-cell adhesion. This study focused on the role of HGF on the expression and distribution of E-cadherin. Furthermore, we found induction of aggressiveness of gastric carcinoma by modulation of E-cadherin by HGF.

MATERIALS AND METHODS

Tumor tissues from 50 patients with gastric carcinoma were evaluated for the expression of HGF, its receptor c-Met, and E-cadherin. Western blot analysis and invasion assay were performed to confirm the role of HGF on the modulation of E-cadherin using human gastric cancer cell lines.

RESULTS

Seventy-eight percent of the gastric carcinoma tissues showed overexpression of c-Met. E-cadherin expression was found in 86%, which could be further classified as membranous type (52%) or nonmembranous type (48%). The levels of HGF in tumor tissues increased significantly according to the tumor progression. The levels of HGF in tumors with nonmembranous type E-cadherin expression were significantly higher than those in tumors with membranous expression. A striking morphologic change from epithelial shape to fibroblastic shape was observed in SNU-16 cells after 3 days' exposure to HGF, accompanied by down-regulation of functional E-cadherin in the membrane. Treatment of the cells with HGF induced significant invasion into the matrigel.

CONCLUSION

We can conclude that HGF can modulate the expression of E-cadherin in gastric carcinoma, which was accompanied by more aggressive phenotype.

Lithium stimulates proliferation in cultured thyrocytes by activating Wnt/beta-catenin signalling

BACKGROUND

Lithium, clinically used in the treatment of bipolar disorders, is well known to induce thyroid growth. However, the mechanism involved is only incompletely characterized. Although it is conventionally believed that thyroid proliferation depends on the thyroid-stimulating hormone (TSH)/cAMP/cAMP response element binding protein (CREB) pathway, recent data indicate that Wnt/beta-catenin signalling may be of critical importance. In other cell types lithium activates canonical Wnt signalling by GSK-3beta inhibition, which in turn stabilizes cytosolic free beta-catenin. Here we investigated the potential modulation of Wnt/beta-catenin signalling under lithium treatment in primary and neoplastic human thyrocytes.

METHODS

Primary (S18) and neoplastic (NPA, FTC133) thyrocytes treated with and without LiCl were analysed using Western blotting, immunoprecipitation, reporter-gene assay, MTT proliferation assay and transfection studies.

RESULTS

LiCl dose-dependently inhibited GSK-3beta, stabilized free beta-catenin and inhibited beta-catenin degradation. Furthermore, LiCl altered the assembly of adherens junction by upregulating the E-cad-herin repressor, Snail, and downregulated E-cadherin expression. At a dose of 5 mM, LiCl significantly increased the proliferative potency of thyrocytes, which appeared to be mediated by beta-catenin, since nuclear beta-catenin stimulated T-cell factor/lymphoid enhancer factor (TCF/LEF)-mediated transcription and upregulated downstream targets like cyclin D1. To characterize the specificity of Wnt/beta-catenin-driven thyrocyte proliferation, we transfected primary thyrocytes and FTC133 cells with dominant negative TCF4 to block Wnt-dependent pathways or with dominant negative CREB to inhibit the TSH/cAMP cascade. In cells transfected with dominant negative CREB lithium-stimulated proliferation was unchanged whereas blocking Wnt/beta-catenin by dominant negative TCF4 reduced proliferation by approx. 50%.

CONCLUSION

Our data indicate that Wnt/beta-catenin signalling is of major importance in the control of lithium-dependent thyrocyte proliferation.

Phosphorylation of ezrin enhances microvillus length via a p38 MAP-kinase pathway in an immortalized mouse hepatic cell line

The apical microvilli are closely related with the development and the maintenance of cell polarization, and the length of microvilli varies in a regular way among cell types. Ezrin, a member of the ezrin/radixin/moesin (ERM) family, seems to be involved in the formation and stabilization of the apical microvilli. We found that phosphorylation of ezrin caused elongation of microvilli via a p38 MAP-kinase signaling pathway in an immortalized mouse hepatic cell line. When, in the oncogenic Raf-1-transfected mouse hepatic cell line, epithelial to mesenchymal transition (EMT) indicated as down-regulation of E-cadherin and up-regulation of Snail occurred, loss of microvilli and down-regulation of ezrin but not radixin and moesin were also observed. In the Raf-1 transfectants treated with the MAP-kinase inhibitor PD98059 and the p38 MAP-kinase inhibitor SB203580, the numbers of microvilli and the expression of ezrin, E-cadherin and Snail were recovered. More interestingly, treatment with SB203580 induced elongation of microvilli and increased phosphorylation of ezrin (at Thr-567 and Tyr-353). Phosphorylated ezrin-positive dots were colocalized with actin-positive dots on the surface of some Raf-1 transfectants treated with SB203580. These results suggested that phosphorylation of ezrin via the p38 MAP-kinase signaling pathway might be involved in the formation of microvilli during development of epithelial cell polarization.

Discrepancy between E-cadherin protein expression and morphology in human gastric carcinoma cells

BACKGROUND/AIMS

The E-cadherin-mediated cell adhesion system is now considered to be an "invasion suppressor system" in cancer cells. The purpose of this study is to examine the effect of E-cadherin on morphogenesis of MKN28 human gastric carcinoma cell line in the course of E-cadherin antisense S-oligodeoxynucleotide (ODN) treatment.

METHODOLOGY

The effect of E-cadherin antisense or random S-ODN treatment on cell growth, morphology in monolayer culture, and E-cadherin protein expression of MKN28 cells were evaluated. Further, immunohistochemical examination was performed.

RESULTS

Cell growth under 3-microM and 6-microM E-cadherin antisense S-ODN treatment did not differ from that under random S-ODN treatment. Although the expression of E-cadherin was decreased assuredly at the time of 6 days after 3-microM E-cadherin antisense S-ODN treatment by immunohistochemical examination, cell-cell adhesion was still observed until Day 10 after the treatment. On Day 15, the cells lost the cell-cell adhesion and showed the detachment and intercellular slits at least. Expression of the insoluble fraction of E-cadherin protein decreased in E-cadherin antisense S-ODN treatment cells at 6 days.

CONCLUSIONS

In this study, we demonstrated that discrepancy between E-cadherin protein expression and morphology exists in MKN28 cells treated with E-cadherin antisense S-ODN treatment.

1alpha,25-Dihydroxyvitamin D3 regulates the expression of Id1 and Id2 genes and the angiogenic phenotype of human colon carcinoma cells

1alpha,25-Dihydroxyvitamin D3 (1alpha,25(OH)2D3) has antitumor activity in addition to its classical action on calcium metabolism and bone tissue biology. It is thought to regulate the expression of multiple target genes and thus modulate processes critical for tumor growth and metastases. Here we show that 1alpha,25(OH)2D3 differentially regulates the expression of Id1 and Id2 genes, members of a family of transcriptional regulators of cell proliferation and differentiation. 1alpha,25(OH)2D3 induced epithelial differentiation in SW480-ADH human colon carcinoma cell line by promoting expression of the proteins implicated in adherent junction formation, including E-cadherin, and by inhibiting beta-catenin transcriptional activity. 1alpha,25(OH)2D3 activated the human Id1 gene promoter and rapidly induced Id1 RNA and protein. Ectopic overexpression of Id1 was not sufficient to induce E-cadherin, which was critical for the morphological changes induced by 1alpha,25(OH)2D3 in SW480-ADH cells. Conversely, Id2 transcription rate, RNA and protein levels were decreased by 1alpha,25(OH)2D3. Id2 downregulation by 1alpha,25(OH)2D3 mediated the antiproliferative effect of 1alpha,25(OH)2D3 on SW480-ADH cells. In addition, we showed that 1alpha,25(OH)2D3 changed the levels of the inducer of angiogenesis, vascular endothelial growth factor and the potent antiangiogenic factor thrombospondin-1, leading to a balanced change in the angiogenic potential of SW480-ADH human colon carcinoma cells.

Differentiation of circulating endothelial progenitor cells to a cardiomyogenic phenotype depends on E-cadherin

Progenitor cells may contribute to cardiac regeneration. Here, we investigated the role of cadherins and integrins for differentiation of human adult circulating endothelial progenitor cells (EPCs) into cardiomyocytes (CM) in a co-culture system. N- and E-cadherin were expressed in EPCs and were localized at the interface between EPCs and CM. Incubation of a blocking antibody against E-cadherin reduced the expression of CM marker protein in EPCs. Blocking antibodies against N- or P-cadherin or the beta1- and beta2-integrins were not effective. These data suggested that cell-to-cell communication mediated by E-cadherin contributes to the acquirement of a cardiomyogenic phenotype of human endothelial progenitor cells.

Promotion of adenoma growth by dietary inulin is associated with increase in cyclin D1 and decrease in adhesion proteins in Min/+ mice mucosa

We have earlier shown that dietary fructo-oligosaccharide inulin enhances adenoma growth in multiple intestinal neoplasia (Min/+) mice. To further explore inulin-induced early biochemical changes in the normal-appearing mucosa, Min/+ mice were fed from the age of 5 weeks to the ages of 8 and 15 weeks a control diet or an inulin-enriched diet (10% w/w). In addition, the wild-type littermates were fed with the same diets until the age of 8 weeks, in order to determine whether similar changes happen both in the wild-type and Min/+ mice. The mucosa without adenomas was collected and fractionated to nuclear, cytosolic and membrane pools. The protein levels of beta-catenin, cyclin D1 and E-cadherin were determined by Western blotting at both time points, and immunohistochemical stainings were done for 8-week-old mice. The promotion of adenoma growth by inulin (week 15, 1.3-fold increase, P=.0004) was associated with accumulation of cytosolic and nuclear beta-catenin, and increased amount of cytosolic cyclin D1 (1.5-fold increase, P=.003) in the normal-appearing mucosa of the Min/+ mice. Furthermore, inulin feeding reduced the membranous pools of beta-catenin and E-cadherin. Also in the wild-type mice the drop in membranous beta-catenin was clear (P=.015), and, moreover, a subset of crypts had enhanced nuclear beta-catenin staining. These data indicate that dietary inulin can already activate in the normal-appearing mucosa beta-catenin signaling, which in the presence of Apc mutation induces adenoma growth and even in the wild-type mice direction of the changes is similar.

Loss of functional E-cadherin renders cells more resistant to the apoptotic agent taxol in vitro

Experimental evidence supports a role for E-cadherin in suppressing invasion, metastasis, and proliferation. Germline mutations of the E-cadherin represent the genetic cause of hereditary diffuse gastric cancer (HDGC). In this type of tumor, isolated cancer cells permeate the basal membrane and paradoxically survive in the gastric wall in the absence of contact with neighbor epithelial cells or with the extracellular matrix. This suggests that upon E-cadherin deregulation, cells acquired resistance to apoptosis. To test this hypothesis, CHO cells stably expressing either wild-type E-cadherin or the HDGC-related germline mutations T340A and V832M were seeded either on a thin layer of collagen type I or on plastic and then subjected to the apoptotic agent taxol. We found that in vitro functional E-cadherin renders cells more sensitive to the effect of taxol. Our results also indicate that this effect is associated to decreased level of the anti-apoptotic bcl-2 protein.

Extracellular cleavage of E-cadherin by leukocyte elastase during acute experimental pancreatitis in rats

BACKGROUND & AIMS

Cadherins play an important role in cell-cell contact formation at adherens junctions. During the course of acute pancreatitis, adherens junctions are known to dissociate-a requirement for the interstitial accumulation of fluid and inflammatory cells-but the underlying mechanism is unknown.

METHODS

Acute pancreatitis was induced in rats by supramaximal cerulein infusion. The pancreas and lungs were either homogenized for protein analysis or fixed for morphology. Protein sequencing was used to identify proteolytic cleavage sites and freshly prepared acini for ex vivo studies with recombinant proteases. Results were confirmed in vivo by treating experimental pancreatitis animals with specific protease inhibitors.

RESULTS

A 15-kilodalton smaller variant of E-cadherin was detected in the pancreas within 60 minutes of pancreatitis, was found to be the product of E-cadherin cleavage at amino acid 394 in the extracellular domain that controls cell-contact formation, and was consistent with E-cadherin cleavage by leukocyte elastase. Employing cell culture and ex vivo acini leukocyte elastase was confirmed to cleave E-cadherin at the identified position, followed by dissociation of cell contacts and the internalization of cleaved E-cadherin to the cytosol. Inhibition of leukocyte elastase in vivo prevented E-cadherin cleavage during pancreatitis and reduced leukocyte transmigration into the pancreas.

CONCLUSIONS

These data provide evidence that polymorphonuclear leukocyte elastase is involved in, and required for, the dissociation of cell-cell contacts at adherens junctions, the extracellular cleavage of E-cadherin, and, ultimately, the transmigration of leukocytes into the epithelial tissue during the initial phase of experimental pancreatitis.

Anthrax lethal toxin induces endothelial barrier dysfunction

Hemorrhage and pleural effusion are prominent pathological features of systemic anthrax infection. We examined the effect of anthrax lethal toxin (LT), a major virulence factor of Bacillus anthracis, on the barrier function of primary human lung microvascular endothelial cells. We also examined the distribution patterns of cytoskeletal actin and vascular endothelial-cadherin (VE-cadherin), both of which are involved in barrier function regulation. Endothelial monolayers cultured on porous membrane inserts were treated with the LT components lethal factor (LF) and protective antigen (PA) individually, or in combination. LT induced a concentration- and time-dependent decrease in transendothelial electrical resistance that correlated with increased permeability to fluorescently labeled albumin. LT also produced a marked increase in central actin stress fibers and significantly altered VE-cadherin distribution as revealed by immunofluorescence microscopy and cell surface enzyme-linked immunosorbent assay. Treatment with LF, PA, or the combination of an inactive LF mutant and PA did not alter barrier function or the distribution of actin or VE-cadherin. LT-induced barrier dysfunction was not dependent on endothelial apoptosis or necrosis. The present findings support a possible role for LT-induced barrier dysfunction in the vascular permeability changes accompanying systemic anthrax infection.

Characterization of a new allele of Ames waltzer generated by ENU mutagenesis

Mutation in the protocadherin 15 (Pcdh15) gene causes hair cell dysfunction and is associated with abnormal stereocilia development. We have characterized the first allele (Pcdh15(av-nmf19)) of Ames waltzer (av) obtained by N-ethyl-N-nitrosourea (ENU) mutagenesis. Pcdh15(av-nmf19) was generated in the Neuroscience Mutagenesis Facility (NMF) at The Jackson Lab (Bar Habor, USA). Pcdh15(av-nmf19) mutants display circling and abnormal swimming behavior along with lack of auditory-evoked brainstem response at the highest intensities tested. Mutation analysis shows base substitution (A--> G) in the consensus splice donor sequence linked to exon 14 resulting in the skipping of exon 14 and the splicing of exon 13-15. This results in the introduction of a stop codon in the coding sequence of exon 15 due to shift in the reading frame. The effect of nmf19 mutation is expected to be severe since the expressed Pcdh15 protein is predicted to truncate in the 5th cadherin domain. Abnormalities of cochlear hair cell stereocilia are apparent in Pcdh15(av-nmf19) mutants near the time of birth and by about P15 (15 days after birth) there is evidence of sensory cell degeneration. Disorganization of outer hair cell stereocilia is observed as early as P2. Inner hair cell stereocilia are also affected, but less severely than those of the outer hair cells. These results are consistent with characteristics of the mutation in the Pcdh15(av-nmf19) allele and they support our previous finding that Protocadherin 15 plays an important role in hair-bundle morphogenesis.

The nonsteroidal anti-inflammatory drug, nabumetone, differentially inhibits beta-catenin signaling in the MIN mouse and azoxymethane-treated rat models of colon carcinogenesis

The mechanisms through which beta-catenin signaling is inhibited during colorectal cancer chemoprevention by nonsteroidal anti-inflammatory agents is incompletely understood. We report that nabumetone decreased uninvolved intestinal mucosal beta-catenin levels in the MIN mouse with a concomitant increase in glycogen synthase kinase (GSK)-3beta levels, an enzyme that targets beta-catenin for destruction. However, in the azoxymethane-treated rat, where beta-catenin is frequently rendered GSK-3beta-insensitive, nabumetone failed to alter beta-catenin levels but did decrease beta-catenin nuclear localization and transcriptional activity as gauged by cyclin D1. In conclusion, we demonstrate that the differential mechanisms for beta-catenin suppression may be determined, at least partly, by GSK-3beta.

Influence of retinoic acid on adhesion complexes in human hepatoma cells: a clue to its antiproliferative effects

Retinoic acid exerts antiproliferative and differentiative effects in normal and transformed in vitro hepatocytes. In order to verify whether these effects are related to a modulation of adhesion molecules, we used Western blot analysis and immunofluorescence microscopy to investigate the E-cadherinl/beta-catenin complex, the main system of adherens junctions, and the occludin/ZO-1 complex present in the tight junctions in HepG2 cells cultured in the presence or absence of retinoic acid. Results showed that retinoic acid treatment increases the amount of beta-catenin bound to E-cadherin by decreasing its tyrosine-phosphorylation level. Similar results were obtained with the tight junction system, in which the amount of occludin/ZO-1 complex is increased by a similar mechanism that reduced the level of ZO-1 phosphorylation on tyrosine. Immunofluorescence images also confirm these results, showing the localization on the cell surface of both adhesion complexes. Their insertion into the plasma membrane could be suggestive of an optimal reassembly and function of adherens and tight junctions in hepatoma cells, indicating that retinoic acid, besides inhibiting cell proliferation, improves cell-cell adhesion, sustaining or inducing the expression of a more differentiated phenotype.

CCL25 Enhances CD103-Mediated Lymphocyte Adhesion to E-Cadherin

Our results demonstrate that (1) CD103 is upregulated on CD8(+) T cells subsequent to their entry into the small intestinal epithelium, and (2) that the chemokine CCL25 enhances CD103-mediated adhesion to E-cadherin. These results suggest a novel role for chemokines in modulating interactions between lymphocytes and epithelial cells at mucosal surfaces.

Expression of cell adhesion molecules in the adriamycin-induced esophageal atresia rat model

Cell adhesion molecules are well-known membrane glycoproteins widely expressed during embryonic development that play a crucial role in cell division, migration and differentiation. We investigated the cell-matrix relationship using N-CAM and pan-cadherin adhesion molecules in the adriamycin-induced esophageal atresia (EA) rat model in the hope of finding a clue to the mechanisms of this unique anomaly.Time-mated pregnant Sprague-Dawley rats were given either saline or adriamycin on days 8 and 9 of gestation. Embryos were harvested on the 18th day of gestation. Esophageal specimens obtained from adriamycin-exposed embryos with (EA+) or without esophageal atresia (EA-) and from saline-exposed embryos were immunostained with N-CAM and pan-cadherin primary antisera. The esophageal specimens from control and EA- groups revealed similar immunostaining properties: weak N-CAM and pan-cadherin immunoreactivity. In contrast, the EA+ group showed intense immunoreactivity. Our study demonstrated an increased synthesis of N-CAM and pan-cadherin in the epithelial cells of the atretic esophagus and trachea. These results suggest that embryonic cell-cell and cell-matrix interactions may play a crucial role in the development of adriamycin-induced EA.

Induction of apoptosis in cultured endothelial cells by a cadherin antagonist peptide: involvement of fibroblast growth factor receptor-mediated signalling

Cadherins are a family of transmembrane glycoproteins mediating calcium-dependent, homophilic cell-cell adhesion. In addition, these molecules are involved in signaling events, regulating such processes as cell motility, proliferation, and apoptosis. Members of the cadherin subfamily, called either classical or type I cadherins, contain a highly conserved sequence at their homophilic binding site consisting of the three amino acids--histidine-alanine-valine (HAV). Previous studies have shown that peptides containing the HAV motif inhibit cadherin-dependent events such as cell aggregation, compaction, and neurite outgrowth. We report here that a cyclic peptide, N-Ac-CHAVC-NH2 can perturb cadherin-mediated endothelial cell interactions, resulting in a progressive apoptotic cell death. This effect depends on cell density, as it is only observed when dense cultures are treated with the peptide. Adherens junction (AJ)-associated cadherin and catenins are differentially affected by the N-Ac-CHAVC-NH2 treatment, as judged by double immunofluorescence labeling followed by immunofluorescence-ratio imaging. However, cell-cell adhesions are largely retained during the first few hours after addition of the peptide. It was also observed that following treatment, actin filaments partially lose their plasma membrane anchorage at AJs and translocate towards the cell center. Interestingly, addition of basic fibroblast growth factor to confluent, peptide-treated, endothelial cell cultures, completely blocks apoptosis and the inhibitory peptide reduce the phosphorylation of the FGF receptor target protein FRS2, suggesting that the peptide exerts its effect by inhibiting cadherin-mediated activation of fibroblast growth factor receptor signaling. We propose that cadherin-mediated signaling is essential for maintaining viability of confluent endothelial cells, and that its perturbation by N-Ac-CHAVC-NH2 drives these cells to apoptosis.