Transforming growth factor-beta signaling during epithelial-mesenchymal transformation: implications for embryogenesis and tumor metastasis

The transcription factor Snail enhanced the degradation of E-cadherin and desmoglein 2 in oral squamous cell carcinoma cells

Epithelial-mesenchymal transition (EMT), a key process in the tumor metastatic cascade, is characterized by the loss of cell-cell junctions and cell polarity as well as the acquisition of migratory and invasive properties. However, the precise molecular events that initiate this complex EMT process are poorly understood. Snail is a regulator of EMT that represses E-cadherin transcription through its interaction with proximal E-boxes in the promoter region of target genes. To investigate the role of Snail in EMT, we generated stable Snail transfectants using the oral squamous cell carcinoma cell line HSC-4 (Snail/HSC-4). Snail/HSC-4 cells had a spindle-shaped mesenchymal morphology, and enhanced migration and invasiveness relative to control cells. Consistent with these EMT changes, the downregulation of epithelial marker proteins, E-cadherin and desmoglein 2, and the upregulation of mesenchymal marker proteins, vimentin and N-cadherin were detected. Despite these observations, the mRNA levels of E-cadherin and desmoglein 2 did not decrease significantly. Although E-cadherin and desmoglein 2 proteins were stable in parental HSC-4 cells, these proteins were rapidly degraded in Snail/HSC-4 cells. The degradation of E-cadherin, but not desmoglein 2, was inhibited by dynasore, an inhibitor of dynamin-dependent endocytosis. Therefore, in HSC-4 cells Snail regulates levels of these proteins both transcriptionally and post-translationally.

Extracellular signal-regulated kinase and Akt activation play a critical role in the process of hepatocyte growth factor-induced epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) has recently been studied to elucidate mechanisms of the liver metastatic process. We investigated EMT in the process of liver metastasis and the effects of chemotherapy on EMT cells as therapeutic strategy for colorectal liver metastasis. We used the CT26 murine colorectal carcinoma cell line to create an in vivo mouse liver metastasis model. Liver tumors were stained immuno-histochemically. Expression of proteins associated with TGF-β/Smad and hepatocyte growth factor (HGF)/c-Met pathways were investigated by western blotting. Cells with c-Met mRNA knockdown by siRNA techniques showed clearly reduced liver metastases compared with regular cells at 21 days. TGF-β and HGF induced EMT expression, but signal transduction was quite different. TGF-β induced ERK, but not Akt phosphory-lation. HGF mediated both ERK and Akt phosphorylation. Akt inhibitor blocked Akt phosphorylation but did not affect TGF-β-induced activation of ERK, Snail and Slug. U-0126 did not reduce Snail activity by TGF-β at a concentration to block ERK phosphorylation. However, Akt inhibitor and U-0126 completely inhibited HGF-induced Slug activation. 5-FU mediated cell death in the EMT process induced by TGF-β more effectively than HGF. ERK/Akt signaling, but not the Smad pathway, may be one of the main processes in HGF-induced EMT, despite the Smad pathway, but not ERK/Akt, being critical for TGF-β-induced EMT. The MAPK/Akt pathway is indispensable in HGF/c-Met signaling. The ERK/Akt pathway particularly may be critical in the HGF-induced EMT process. However, long-term use of chemotherapeutic agents may induce drug resistance and distant metastases through EMT-related signaling pathway activation.

Epithelial-mesenchymal transition in breast cancer progression and metastasis

Breast cancer is the most common cancer in women, and approximately 90% of breast cancer deaths are caused by local invasion and distant metastasis of tumor cells. Epithelial-mesenchymal transition (EMT) is a vital process for large-scale cell movement during morphogenesis at the time of embryonic development. Tumor cells usurp this developmental program to execute the multi-step process of tumorigenesis and metastasis. Several transcription factors and signals are involved in these events. In this review, we summarize recent advances in breast cancer researches that have provided new insights in the molecular mechanisms underlying EMT regulation during breast cancer progression and metastasis. We especially focus on the molecular pathways that control EMT.

New insights into the regulation of epithelial-mesenchymal transition and tissue fibrosis

Tissue fibrosis often presents as the final outcome of chronic disease and is a significant cause of morbidity and mortality worldwide. Fibrosis is driven by continuous expansion of fibroblasts and myofibroblasts. Epithelial-mesenchymal transition (EMT) is a form of cell plasticity in which epithelia acquire mesenchymal phenotypes and is increasingly recognized as an integral aspect of tissue fibrogenesis. In this review, we describe recent insight into the molecular and cellular factors that regulate EMT and its underlying signaling pathways. We also consider how mechanical cues from the microenvironment affect the regulation of EMT. Finally, we discuss the role of EMT in fibrotic diseases and propose approaches for detecting and treating fibrogenesis by targeting EMT.

Transcriptomic profiling reveals hepatic stem-like gene signatures and interplay of miR-200c and epithelial-mesenchymal transition in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocellular carcinoma (ICC) is the second most common type of primary liver cancer. However, its tumor heterogeneity and molecular characteristics are largely unknown. In this study, we conducted transcriptomic profiling of 23 ICC and combined hepatocellular cholangiocarcinoma tumor specimens from Asian patients using Affymetrix messenger RNA (mRNA) and NanoString microRNA microarrays to search for unique gene signatures linked to tumor subtypes and patient prognosis. We validated the signatures in an additional 68 ICC cases derived from Caucasian patients. We found that both mRNA and microRNA expression profiles could independently classify Asian ICC cases into two main subgroups, one of which shared gene expression signatures with previously identified hepatocellular carcinoma (HCC) with stem cell gene expression traits. ICC-specific gene signatures could predict survival in Asian HCC cases and independently in Caucasian ICC cases. Integrative analyses of the ICC-specific mRNA and microRNA expression profiles revealed that a common signaling pathway linking miR-200c signaling to epithelial-mesenchymal transition (EMT) was preferentially activated in ICC with stem cell gene expression traits. Inactivation of miR-200c resulted in an induction of EMT, whereas activation of miR-200c led to a reduction of EMT including a reduced cell migration and invasion in ICC cells. We also found that miR-200c and neural cell adhesion molecule 1 (NCAM1) expression were negatively correlated and their expression levels were predictive of survival in ICC samples. NCAM1, a known hepatic stem/progenitor cell marker, was experimentally demonstrated to be a direct target of miR-200c.

CONCLUSION

Our results indicate that ICC and HCC share common stem-like molecular characteristics and poor prognosis. We suggest that the specific components of EMT may be exploited as critical biomarkers and clinically relevant therapeutic targets for an aggressive form of stem cell-like ICC.

Recurrent oral cancer: current and emerging therapeutic approaches

Oral cavity cancer (OCC) is associated with high incidence of loco-regional recurrences, which account for the majority of treatment failures post-surgery and radiotherapy. The time-course of relapse manifestation and metastasis are unpredictable. Relapsed OCC represents a major clinical challenge in part due to their aggressive and invasive behaviors. Chemotherapy remains the only option for advanced OCC whenever salvage surgery or re-irradiation is not feasible, but its efficacy is limited as a result of the drug resistance development. Alternatives to use of different permutations of standard cytotoxic drugs or combinations with modulators of drug resistance have led to incremental therapeutic benefits. The introduction of targeted agents and biologics against selective targets that drive cancer progression has opened-up optimism to achieve superior therapeutic activity and overcome drug resistance because, unlike the non-selective cytotoxic, the target can be monitored at molecular levels to identify patients who can benefit from the drug. This review discusses the multifactorial aspects of clinical drug resistance and emerging therapeutic approaches in recurrent OCC, emphasizing recent advances in targeted therapies, immunotherapy, and potential relevance of new concepts such as epithelial-mesenchymal transition and cancer stem cell hypothesis to drug resistance.

Induction of palate epithelial mesenchymal transition by transforming growth factor β3 signaling

Transforming growth factor (TGFβ)3 is essential for palate development, particularly during the late phase of palatogenesis when the disintegration of the palatal medial edge seam (MES) occurs resulting in mesenchymal confluence. The MES is composed of medial-edge epithelium (MEE) of opposite palatal shelves; its complete disintegration is essential for mediating correct craniofacial morphogenesis. This phenomenon is initiated by TGFβ3 upon adherence of opposing palatal shelves, and subsequently epithelial-mesenchymal transition (EMT) instigates the loss of E-Cadherin, causing the MES to break into small epithelial islands forming confluent palatal mesenchyme; however, apoptosis and cell migration or in combination of all are other established mechanisms of seam disintegration. To investigate the molecular mechanisms that cause this E-Cadherin loss, we isolated and cultured murine embryonic primary MES cells from adhered palates and employed several biological approaches to explore the mechanism by which TGFβ3 facilitates palatal seam disintegration. Here, we demonstrate that TGFβ3 signals by activating both Smad-dependent and Smad-independent pathways. However, activation of the two most common EMT related transcription factors, Snail and SIP, was facilitated by Smad-independent pathways, contrary to the commonly accepted Smad-dependent pathway. Finally, we provide the first evidence that TGFβ3-activated Snail and SIP1, combined with Smad4, bind to the E-Cadherin promoter to repress its transcription in response to TGFβ3 signaling. These results suggest that TGFβ3 uses multiple pathways to activate Snail and SIP1 and these transcription factors repress the cell-cell adhesion protein, E-Cadherin, to induce palatal epithelial seam EMT. Manipulation and intervention of the pathways stimulated by TGFβ3 during palate development may have a significant therapeutic potential.

Phospho-specific Smad3 signaling: impact on breast oncogenesis

Members of the TGFβ superfamily are known to exert a myriad of physiologic and pathologic growth controlling influences on mammary development and oncogenesis. In epithelial cells, TGFβ signaling inhibits cell growth through cytostatic and pro-apoptotic activities but can also induce cancer cell EMT and, thus, has a dichotomous role in breast cancer biology. Mechanisms governing this switch are the subject of active investigation. Smad3 is a critical intracellular mediator of TGFβ signaling regulated through phosphorylation by the TGFβ receptor complex at the C terminus. Smad3 is also a substrate for several other kinases that phosphorylate additional sites within the Smad protein. This discovery has expanded the understanding of the significance and complexity of TGFβ signaling through Smads. This review highlights recent advances revealing the critical role of phospho-specific Smad3 in malignancy and illustrates the potential prognostic and therapeutic impact of Smad3 phospho-isoforms in breast cancer.

aV integrins and TGF-β-induced EMT: a circle of regulation

Transforming growth factor-β (TGF-β) has roles in embryonic development, the prevention of inappropriate inflammation and tumour suppression. However, TGF-β signalling also regulates pathological epithelial-to-mesenchymal transition (EMT), inducing or progressing a number of diseases ranging from inflammatory disorders, to fibrosis and cancer. However, TGF-β signalling does not proceed linearly but rather induces a complex network of cascades that mutually influence each other and cross-talk with other pathways to successfully induce EMT. Particularly, there is substantial evidence for cross-talk between αV integrins and TGF-β during EMT, and anti-integrin therapeutics are under development as treatments for TGF-β-related disorders. However, TGF-β's complex signalling network makes the development of therapeutics to block TGF-β-mediated pathology challenging. Moreover, despite our current understanding of integrins and TGF-β function during EMT, the precise mechanism of their role during physiological versus pathological EMT is not fully understood. This review focuses on the circle of regulation between αV integrin and TGF-β signalling during TGF-β induced EMT, which pose as a significant driver to many known TGF-β-mediated disorders.

Over-expression of integrin-linked kinase correlates with aberrant expression of Snail, E-cadherin and N-cadherin in oral squamous cell carcinoma: implications in tumor progression and metastasis

Integrin-linked kinase (ILK), an intracellular protein with serine/threonine protein kinase activities, plays a key role in integrin mediated cell-excellular matrix interactions, regulating cell proliferation, apoptosis, differentiation, and migration. ILK has been implicated in the development and progression in several malignancies. However, the role of ILK and ILK-mediated epithelial-mensenchymal transition (EMT) in the progression of oral squamous cell carcinoma (OSCC) has not been well understood. Here, by immunohistochemistry, we studied the expression of ILK, Snail, E-cadherin and N-cadherin in 98 primary OSCC specimens and analyzed their correlations with clinicopathologic profiles and clinical outcome. We also investigated the expression of ILK in 42 corresponding lymph node metastases. Positive expression of ILK protein was detected in 87.8 % of the primary tumors and 100 % of metastatic lesions. Increased ILK expression was correlated strongly with enhanced tumor invasion, higher tumor grade, advanced clinical stage, positive lymph node status and increased risk of recurrence. Higher ILK expression was also observed in lymph node metastases in comparison with the corresponding primary tumor. Moreover, up-regulation of Snail and N-cadherin and down-regulation of E-cadherin correlated significantly with both ILK over-expression and tumor invasion. Patients with higher ILK expression exhibited shorter disease-free survival while those with absent E-cadherin expression exhibited shorter overall and disease-free survival. Taken together, our results suggest that ILK may have an important role in progression and metastasis of OSCC, possibly through EMT involving up-regulation of Snail and consequent aberrant expression of E-cadherin and N-cadherin. ILK should be considered as a critical prognostic indicator for patients with OSCC.

Cigarette smoke extract stimulates epithelial-mesenchymal transition through Src activation

Epithelial-mesenchymal transition (EMT) is implicated in the pathogenesis of lung fibrosis and cancer metastasis, two conditions associated with cigarette smoke (CS). CS has been reported to promote the EMT process. CS is the major cause of lung cancer and nearly half of lung cancer patients are active smokers. Nonetheless, the mechanism whereby CS induces EMT remains largely unknown. In this study we investigated the induction of EMT by CS and explored the underlying mechanisms in the human non-small-cell lung carcinoma (H358) cell line. We demonstrate that exposure to an extract of CS (CSE) decreases E-cadherin and increases N-cadherin and vimentin, markers of EMT, in H358 cells cultured in RPMI 1640 medium with 1% fetal bovine serum. Pretreatment with N-acetylcysteine (NAC), a potent antioxidant and precursor of glutathione, abrogated changes in these EMT markers. In addition, CSE activated Src kinase (shown as increased phosphorylation of Src at Tyr418), and the Src kinase inhibitor PP2 inhibited CS-stimulated EMT changes, suggesting that Src is critical in CSE-stimulated EMT induction. Furthermore, NAC treatment abrogated CSE-stimulated Src activation. However, co-incubation with catalase had no effect on CSE-mediated Src activation. Finally, acrolein, an unsaturated aldehyde present in CSE, caused Src activation. Taken together, these data suggest that CSE initiates EMT through Src, which is activated by CS through redox modification.

Epithelial-mesenchymal transition in oral squamous cell carcinoma

Oral cancer is one of the drastic human cancers due to its aggressiveness and high mortality rate. Of all oral cancers, squamous cell carcinoma is the most common accounting for more than 90%. Epithelial-mesenchymal transition (EMT) is suggested to play an important role during cancer invasion and metastasis. Recently, emerging knowledge on EMT in carcinogenesis is explosive, tempting us to analyze previous studies on EMT in oral squamous cell carcinoma (OSCC). In this paper, we have first addressed the general molecular mechanisms of EMT, evidenced by alterations of cell morphology during EMT, the presence of cadherin switching, turning on and turning off of many specific genes, the activation of various signaling pathways, and so on. The remaining part of this paper will focus on recent findings of the investigations of EMT on OSCC. These include the evidence of EMT taking place in OSCC and the signaling pathways employed by OSCC cells during their invasion and metastasis. Collectively, with the large body of new knowledge on EMT in OSCC elaborated here, we are hopeful that targeting treatment for OSCC will be developed.

Intratumoral macrophages contribute to epithelial-mesenchymal transition in solid tumors

BACKGROUND

Several stromal cell subtypes including macrophages contribute to tumor progression by inducing epithelial-mesenchymal transition (EMT) at the invasive front, a mechanism also linked to metastasis. Tumor associated macrophages (TAM) reside mainly at the invasive front but they also infiltrate tumors and in this process they mainly assume a tumor promoting phenotype. In this study, we asked if TAMs also regulate EMT intratumorally. We found that TAMs through TGF-β signaling and activation of the β-catenin pathway can induce EMT in intratumoral cancer cells.

METHODS

We depleted macrophages in F9-teratocarcinoma bearing mice using clodronate-liposomes and analyzed the tumors for correlations between gene and protein expression of EMT-associated and macrophage markers. The functional relationship between TAMs and EMT was characterized in vitro in the murine F9 and mammary gland NMuMG cells, using a conditioned medium culture approach. The clinical relevance of our findings was evaluated on a tissue microarray cohort representing 491 patients with non-small cell lung cancer (NSCLC).

RESULTS

Gene expression analysis of F9-teratocarcinomas revealed a positive correlation between TAM-densities and mesenchymal marker expression. Moreover, immunohistochemistry showed that TAMs cluster with EMT phenotype cells in the tumors. In vitro, long term exposure of F9-and NMuMG-cells to macrophage-conditioned medium led to decreased expression of the epithelial adhesion protein E-cadherin, activation of the EMT-mediating β-catenin pathway, increased expression of mesenchymal markers and an invasive phenotype. In a candidate based screen, macrophage-derived TGF-β was identified as the main inducer of this EMT-associated phenotype. Lastly, immunohistochemical analysis of NSCLC patient samples identified a positive correlation between intratumoral macrophage densities, EMT markers, intraepithelial TGF-β levels and tumor grade.

CONCLUSIONS

Data presented here identify a novel role for macrophages in EMT-promoted tumor progression. The observation that TAMs cluster with intra-epithelial fibroblastoid cells suggests that the role of macrophages in tumor-EMT extends beyond the invasive front. As macrophage infiltration and pronounced EMT tumor phenotype correlate with increased grade in NSCLC patients, we propose that TAMs also promote tumor progression by inducing EMT locally in tumors.

Transforming growth factor-β is required for vasculogenic mimicry formation in glioma cell line U251MG

Both vasculogenic mimicry (VM) and transforming growth factor-β (TGFβ) are positively correlated with malignancy in glioma. Accordingly, we supposed that TGFβ might be related with VM, and aimed to detect whether TGFβ could influence VM formation in two glioma cell lines U251MG and SHG44, which were different in malignancy. We found that the VM-positive U251MG had a significantly higher TGFβ expression than the VM-negative SHG44. Downregulating TGFβ in U251MG by RNAi technology resulted in a significantly impaired VM formation, which could be rescued by rhTGFβ. However, adding rhTGFβ could not induce VM in SHG44. To investigate the possible mechanism, we detected the changes of some VM-related genes including EphA2, VE-cadherin, MMP-2, MMP-9, MT1-MMP and LAMC2 by RT-PCR and found that MT1-MMP transcript was affected by TGFβ expression. Gelatin zymography showed a declined MMP-2 activity in the TGFβ-inhibited cells. Further studies showed that MT1-MMP inhibition impaired VM formation in U251MG. Moreover, TGFβ induced MT1-MMP expression and VM formation in a dose-dependent manner. These findings indicated us that TGFβ was required for VM formation in U251MG. MT1-MMP was correlated with TGFβ-induced VM formation. Thus, TGFβ might be a potential target for VM inhibition in glioma.

Regulation of transforming growth factor-β1-driven lung fibrosis by galectin-3

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic dysregulated response to alveolar epithelial injury with differentiation of epithelial cells and fibroblasts into matrix-secreting myofibroblasts resulting in lung scaring. The prognosis is poor and there are no effective therapies or reliable biomarkers. Galectin-3 is a β-galactoside binding lectin that is highly expressed in fibrotic tissue of diverse etiologies.

OBJECTIVES

To examine the role of galectin-3 in pulmonary fibrosis.

METHODS

We used genetic deletion and pharmacologic inhibition in well-characterized murine models of lung fibrosis. Further mechanistic studies were performed in vitro and on samples from patients with IPF.

MEASUREMENTS AND MAIN RESULTS

Transforming growth factor (TGF)-β and bleomycin-induced lung fibrosis was dramatically reduced in mice deficient in galectin-3, manifest by reduced TGF-β1-induced EMT and myofibroblast activation and collagen production. Galectin-3 reduced phosphorylation and nuclear translocation of β-catenin but had no effect on Smad2/3 phosphorylation. A novel inhibitor of galectin-3, TD139, blocked TGF-β-induced β-catenin activation in vitro and in vivo and attenuated the late-stage progression of lung fibrosis after bleomycin. There was increased expression of galectin-3 in the bronchoalveolar lavage fluid and serum from patients with stable IPF compared with nonspecific interstitial pneumonitis and controls, which rose sharply during an acute exacerbation suggesting that galectin-3 may be a marker of active fibrosis in IPF and that strategies that block galectin-3 may be effective in treating acute fibrotic exacerbations of IPF.

CONCLUSIONS

This study identifies galectin-3 as an important regulator of lung fibrosis and provides a proof of principle for galectin-3 inhibition as a potential novel therapeutic strategy for IPF.

Epithelial to mesenchymal transition in early stage endometrioid endometrial carcinoma

Epithelial to mesenchymal transition is thought to be implicated in tumor invasion and metastasis. To investigate its role in myometrial invasion, samples from 42 stage I (confined to the corpus) endometrioid endometrial carcinomas were analyzed. All E-cadherin repressors (SNAI1, SNAI2 (SLUG), ZEB1, HMGA2, and TWIST1) had a higher expression in endometrioid endometrial carcinomas than in normal endometrium (P < .0001), whereas CDH1 (E-cadherin gene) tended to be lower. In comparison with nonmyoinvasive (stage IA) tumors, those with deep myometrial invasion (stage IC) had increased messenger RNA expression of SLUG, ZEB1, and HMGA2 (P < .001). Furthermore, samples from the myoinvasive front of deeply invasive tumors had higher levels of SLUG, ZEB1, and HMGA2 than the corresponding superficial samples. Immunohistochemical analysis of these cases revealed that the decrease in E-cadherin was concordant with an increase in Snail and Twist protein expression. Trying to induce epithelial to mesenchymal transition in endometrioid endometrial carcinomas, we initially produced persistent activation of this pathway in Ishikawa cells. The cell line was infected with lentiviruses carrying the V600E mutation of BRAF, inducing loss of β-catenin, E-cadherin, and cytokeratin and increase in vimentin and Snail. These changes were mediated by ERK1/2 phosphorylation, which was also increased at the myoinvasive front. Furthermore, MEK1/2 inhibitor UO126 reversed the mesenchymal phenotype. Our findings suggest that epithelial to mesenchymal transition regulators are implicated in myometrial invasion of endometrioid endometrial carcinoma and may be potential therapeutic targets through the MAPK/ERK pathway.

Potential role for SNAIL family transcription factors in the etiology of Crohn's disease-associated fistulae

BACKGROUND

Fistulae represent an important clinical complication of Crohn's disease (CD). The fistula tracts are covered by flat, myofibroblast-like cells with an epithelial origin (transitional cells, TC). We recently demonstrated a role of epithelial mesenchymal transition (EMT) in the pathogenesis of CD-associated fistulae. EMT is associated with an increased migratory and invasive potential of epithelial cells in different tissues. Here we investigated whether cytokines or growth factors as well as EMT-associated SNAIL family transcription factors are expressed in CD fistulae.

METHODS

By immunohistochemistry we analyzed seven perianal fistulae from seven CD and two perianal fistulae from two non-inflammatory bowel disease (IBD) control patients. Hematoxylin and eosin staining or immunohistochemistry for the expression of tumor necrosis factor (TNF), TNF-receptor I (TNF-RI), SNAIL1, SLUG, fibroblast growth factors (FGF) 1, 2, 4, 7, epidermal growth factor (EGF), and TWIST were performed using standard techniques.

RESULTS

Immunohistochemical staining of surgical specimens from CD patients revealed a strong expression of TNF and TNF-RI in and around fistula tracts. While SNAIL1 was also heavily expressed in the nuclei of TC, indicative of transcriptionally active protein, SLUG, FGF-1, and FGF-2 were detected rather in the fibrotic periphery of CD fistulae than in TC. In contrast, we did not detect considerable protein staining for FGF-4 and FGF-7 nor of EGF or the transcription factor, TWIST.

CONCLUSIONS

Our data demonstrate that SNAIL1 and TNF are strongly expressed in TC of CD-associated fistulae. These observations support our previous data and indicate the onset of EMT-associated events in the pathogenesis of CD fistulae.

Knockdown of β-Catenin through shRNA cause a reversal of EMT and metastatic phenotypes induced by HIF-1α

OBJECTIVE

Wnt/β-catenin signaling pathway regulates pattern formation during embryogenesis as well as tumor progression. Numbers of studies suggest that this signaling pathway may play an important role in Epithelial-Mesenchymal transition (EMT), however, there was no evidence that Wnt/β-catenin signaling pathway directly controlled the EMT occurrence. Our previous research has successfully proved that overexpression of hypoxia inducible factor-1α (HIF-1α) could induce EMT in LNCaP cells, but not in PC-3. Consistently, the expression of β-catenin protein increased in LNCaP/HIF-1α cells, but not in PC-3/HIF-1α. This study mainly aimed at exploring the essentiality and importance of Wnt/β-catenin signaling pathway in HIF-1α-induced EMT.

METHODS

Human prostate cancer cells (LNCaP) were stably transfected by recombinant plasmid pcDNA3.1(-)/HIF-1α. The positive clones were selected by G418 and confirmed through western blot analysis, reverse transcription-polymerase chain reaction (RT-PCR), and indirect immunofluoesence. Then LNCaP/HIF-1α was transiently transfected with β-catenin shRNA (shRNA1 and shRNA2) and negative shRNA (shRNA-scr). The epithelial markers, mesenchymal markers, and critical proteins in Wnt/β-catenin signaling pathway were separately detected by western blot analysis. Finally, the invasive potency of cells in different transfection group was examined by Matrgel transwell assay.

RESULT

We successfully established prostate cancer cell line LNCaP/HIF-1α and LNCaP/HIF-1α/β-catenin(-). LNCaP/HIF-1α displayed high expression of mesenchymal markers and low expression of epithelial markers. However, compared with LNCaP/HIF-1α, the epithelial marker E-cadherin was increased in LNCaP/HIF-1α/β-catenin(-), whereas the expression of mesenchymal marker N-cadherin, vimentin, MMP-2 were significantly decreased. Inhibition of Wnt signal activity through β-catenin shRNA cause a reversal of EMT induced by HIF-1α in human prostate cancer.

CONCLUSION

Overexpression of HIF-1α stimulates the invasion potency of human prostate carcinoma cells through EMT pathway and Wnt/β-catenin signaling pathway played a vital role in this process. Wnt/β-catenin signaling pathway might be a necessary endogenous signal that directly controlled the EMT occurrence induced by HIF-1α.

Advances and applications of oral cancer basic research

Cancer of the oral cavity accounts for almost 3% of cancer cases in the world. The incidence varies widely reflecting geographic differences in exposure to risk factors. The recent rise in younger age groups and females seen in many countries is of particular concern. Treatment and management of complications, locoregional recurrence and further primary tumors result in high morbidity and mortality especially when the disease is advanced stage at initial diagnosis. Progress in cancer research has provided abundant new knowledge about cellular processes and molecular biology underlying oral carcinogenesis and tumor progression. The present review attempts to summarize the current most widely-used research approaches and their application in the prevention, diagnosis, effective treatment, and improved outcome of oral cancer.

Transforming growth factor-β1 promotes lung adenocarcinoma invasion and metastasis by epithelial-to-mesenchymal transition

Lung cancer is a highly malignant carcinoma, and most deaths of lung cancer are caused by metastasis. The alterations associated with epithelial-to-mesenchymal transition (EMT) may be related to the cancer cell metastasis. Nevertheless, the mechanism of lung cancer metastasis remains unclear. We conducted a study in vitro to investigate whether transforming growth factor-β1 (TGF-β1) could induce changes of, such as cell morphology, expression of relative protein markers, and cellular motile and invasive activities. In this research, the changes of cell morphology were first investigated under a phase contrast microscope, then western blotting was employed to detect the expression of E-cadherin, vimentin, and fibronectin, and finally cell motility and invasion were evaluated by cell wound-healing as well as invasion assays. The data indicated that human lung adenocarcinoma cell lines, A-549 and PC-9 cells of epithelial cell characteristics, were induced to undergo EMT by TGF-β1. Following TGF-β1 treatment, cells showed dramatic morphological changes assessed by phase contrast microscopy, accompanied by decreased epithelial marker E-cadherin and increased mesenchymal markers vimentin and fibronectin. More importantly, cell motility and invasion were also enhanced in the EMT process. These results indicated that TGF-β1 may promote lung adenocarcinoma invasion and metastasis via the mechanism of EMT.

The role of TGF-β and epithelial-to mesenchymal transition in diabetic nephropathy

Transforming Growth Factor-beta (TGF-β) is a pro-sclerotic cytokine widely associated with the development of fibrosis in diabetic nephropathy. Central to the underlying pathology of tubulointerstitial fibrosis is epithelial-to-mesenchymal transition (EMT), or the trans-differentiation of tubular epithelial cells into myofibroblasts. This process is accompanied by a number of key morphological and phenotypic changes culminating in detachment of cells from the tubular basement membrane and migration into the interstitium. Ultimately these cells reside as activated myofibroblasts and further exacerbate the state of fibrosis. A large body of evidence supports a role for TGF-β and downstream Smad signalling in the development and progression of renal fibrosis. Here we discuss a role for TGF-β as the principle effector in the development of renal fibrosis in diabetic nephropathy, focusing on the role of the TGF-β1 isoform and its downstream signalling intermediates, the Smad proteins. Specifically we review evidence for TGF-β1 induced EMT in both the proximal and distal regions of the nephron and describe potential therapeutic strategies that may target TGF-β1 activity.

Role of Smad2/3 and p38 MAP kinase in TGF-β1-induced epithelial-mesenchymal transition of pulmonary epithelial cells

Idiopathic pulmonary fibrosis is characterized by myofibroblast accumulation, extracellular matrix (ECM) remodeling, and excessive collagen deposition. ECM-producing myofibroblasts may originate from epithelial cells through epithelial to mesenchymal transition (EMT). TGF-β1 is an inducer of EMT in pulmonary epithelial cells in vitro and in vivo, though the mechanisms are unclear. We hypothesized that TGF-β1 induced EMT through Smad-dependent and -independent processes. To test this hypothesis, we studied the roles and mechanisms of TGF-β1-induced Smad and p38 mitogen-activated protein kinase (MAPK) signaling in EMT-related changes in pulmonary epithelial cells. Exposure of pulmonary epithelial 1HAEo(-) cells to TGF-β1 resulted in morphological and molecular changes of EMT over a 96-h period; loss of cell-cell contact, cell elongation, down-regulation of E-cadherin, up-regulation of fibronectin, and up-regulation of collagen I. Both Smad2/3 and p38 MAPK signaling pathways were activated by TGF-β1. However, neither Smad2/3 nor p38 MAPK were required for the down-regulation of E-cadherin, yet p38 MAPK was associated with fibronectin up-regulation. Both Smad2/3 and p38 MAPK had a role in regulation of TGF-β1-induced collagen expression. Furthermore, these data demonstrate that Smads and p38 MAPK differentially regulate EMT-related changes in pulmonary epithelial cells.

The skinny on Slug

The zinc finger transcription factor Slug (Snai2) serves a wide variety of functions in the epidermis, with roles in skin development, hair growth, wound healing, skin cancer, and sunburn. Slug is expressed in basal keratinocytes and hair follicles where it is important in maintaining epidermal homeostasis. Slug also helps coordinate the skin response to exogenous stimuli. Slug is rapidly induced by a variety of growth factors and injurious agents and Slug controls, directly or indirectly, a variety of keratinocyte responses, including changes in differentiation, adhesion, motility, and production of inflammatory mediators. Slug thus modulates the interactions of the keratinocyte with its environment and with surrounding cells. The function of Slug in the epidermis appears to be distinct from that of the closely related Snail transcription factor.

In vivo effects of adjunctive tetracycline treatment on refractory corneal ulcers in dogs

OBJECTIVE

To evaluate effect of adjunctive treatment with tetracycline analogues on time to complete corneal reepithelialization in dogs with nonhealing (ie, refractory) corneal ulcers.

DESIGN

Randomized controlled clinical trial.

ANIMALS

89 dogs with refractory corneal ulcers.

PROCEDURES

Corneal ulcers were treated via debridement and grid keratotomy. Dogs were assigned to receive 1 of 3 treatment regimens for up to 6 weeks: doxycycline (5 mg/kg [2.27 mg/lb], PO, q 12 h) with topically applied ophthalmic ointment containing neomycin, polymyxin B, and bacitracin (ie, triple antibiotic ointment; q 8 h); cephalexin (22 mg/kg [10 mg/lb], PO, q 12 h) with topically applied oxytetracycline ophthalmic ointment (q 8 h); or a control treatment of cephalexin (22 mg/kg, PO, q 12 h) with topically applied triple antibiotic ointment (q 8 h). Healing was monitored via measurements of the wound with calipers and evaluation of photographs obtained every 2 weeks. Treatment effectiveness was evaluated by wound healing and decreased signs of pain.

RESULTS

The Boxer breed was overrepresented in all groups. At the 2-week time point, wound healing was significantly more common in small-breed dogs, compared with large-breed dogs. Dogs treated with oxytetracycline ophthalmic ointment had a significantly shorter healing time than did dogs receiving the control treatment. Corneal ulcers in dogs that received doxycycline PO healed more rapidly than did ulcers in dogs in the control treatment group; however, this difference was not significant.

CONCLUSIONS AND CLINICAL RELEVANCE

Topical tetracycline ophthalmic ointment was a safe, inexpensive, and effective adjunctive treatment for refractory corneal ulcers in dogs.

TAK1 lysine 158 is required for TGF-β-induced TRAF6-mediated Smad-independent IKK/NF-κB and JNK/AP-1 activation

Lys63-linked TAK1 polyubiquitination plays an essential role in the regulation of TAK1 activation. TRAF6-mediated Lys63-linked polyubiquitylation of TAK1 has been shown to be required for TGF-β-induced TAK1 activation. However, it remains unclear which lysine residue on TAK1 is TRAF6-mediated TAK1 polyubiquitination acceptor site in TGF-β signaling pathway. Here we report that lysine 158 on TAK1 is required for TGF-β-induced TRAF6-mediated TAK1 polyubiquitination and TAK1-mediated IKK, JNK and p38 activation. Notably, in contrast to TAK1 wild-type and K34R mutant, TAK1 K158R mutant co-overexpression with TAB1 failed to induce Lys63-linked TAK1 polyubiquitination. TRAF6-induced K63-linked TAK1 polyubiquitination was blocked by TAK1 K158R mutation, but not by K34R mutation. Furthermore, TGF-β-induced TAK1 polyubiquitination was inhibited by TAK1 K158R mutation, but not by K34R mutation in HeLa cells. Reconstitution of TAK1-deficient mouse embryo fibroblast cells with TAK1 wild-type, K158R mutant, or K34R mutant reveals that TAK1 lysine 158 residue is required for TGF-β-induced IKK, p38 and JNK activation.

Novel ZEB1 expression in bladder tumorigenesis

What's known on the subject? and What does the study add? Epithelial-mesenchymal transition (EMT) is involved in tumor progression where the underlying cellular changes associated with EMT have been identified in in vitro models and confirmed in a limited number of in vivo studies. ZEB1, which targets E-cadherin repression, is a transcriptional regulator that has been implicated in EMT, and is associated with uterine and colorectal cancers. Regulation of ZEB1 expression has been shown to involve different microRNAs (miRNAs), identifying a potential role for miRNA in EMT. In the present study we have identified novel expression of ZEB1 in bladder tumours and shown a role for ZEB1 in enhanced migration and invasion potential in in vitro assays. Confirmation of ZEB1 expression in bladder tumours was shown in tissue microarrays (TMAs).

OBJECTIVE

To evaluate ZEB1 expression in bladder tumorigenesis and define a possible role for this transcription factor in urothelial carcinomas of the bladder (UCBs).

MATERIALS AND METHODS

Five hundred and fifty-eight samples were assembled in 10 tissue microarrays (TMAs; 263 non-muscle-invasive Ta/T1/Tis, 295 muscle-invasive T2-T4). All tumours were transitional cell carcinomas (TCCs) and processed for immunohistochemistry to assess nuclear ZEB1 expression. Expression levels of ZEB1 were modulated in bladder carcinoma cell lines CUBIII or UM-UC-3 after forced expression or shRNA knockdown, respectively. Protein expression levels were determined using western blot analysis and transfectants were assessed for migration and invasion potential in standard in vitro assays.

RESULTS

Nuclear ZEB1 expression was recorded in 22.8% of non-muscle-invasive UCBs and 21.7% of muscle-invasive UCBs, including 24.1% grade I/II and 21.1% grade III tumours, and absent in normal bladder mucosa. No significant correlation was observed for tumour stage and grade, nodal involvement, vascular invasion, metastasis and overall or cancer-specific survival. The introduction or knockdown of ZEB1 expression in bladder carcinoma cell lines showed enhanced or reduced migration and invasive potential, respectively. Changes in ZEB1 expression were accompanied by altered microRNA (miRNA) expression underlying events linked to epithelial-mesenchymal transition (EMT).

CONCLUSION

The results in the present study showed novel expression of ZEB1 in bladder cancer in the absence of a link to clinical variables of change, including metastasis and survival. However, in vitro assays showed enhanced or reduced migration and invasion after the introduction or reduction of ZEB1, respectively, in transfected bladder cell lines. Modulation in expression of ZEB1 was closely linked to changes in the miR-200 family along with alternative known prognostic indicators of bladder tumour progression.

[Research of TGF-beta1 inducing lung adencarcinoma PC9 cells to mesenchymal cells transition]

背景与目的

研究表明上皮-间质转化（epithelial-mesenchymal transition, EMT）不仅参与胚胎形成与发育，而且参与肿瘤侵袭转移。此外，人转化生长因子-β1（transforming growth factor-beta1, TGF-β1）已被证实为肿瘤EMT的主要诱导剂。本研究旨在探讨TGF-β1诱导人肺腺癌PC9细胞发生EMT及其对PI3K/AKT信号通道的影响。

方法

将体外培养的PC9细胞用不同浓度TGF-β1处理48 h，相差倒置显微镜下观察细胞形态学变化；Western blot和细胞免疫荧光验证EMT相关标记蛋白表达变化。同时，采用Western blot方法检测AKT和P-AKT的表达水平。

结果

TGF-β1可诱导PC9细胞向间质型细胞形态转化，并上调间质标记蛋白Fibronectin的表达及下调P-AKT的表达。

结论

TGF-β1可诱导PC9细胞发生EMT，并影响PI3K/AKT信号通道。

Involvement of cholangiocyte proliferation in biliary fibrosis

Cholangiocytes are the epithelial cells that line the biliary tree. In the adult liver, they are a mitotically dormant cell population, unless ductular reaction is triggered by injury. The ability of cholangiocytes to proliferate is important in many different human pathological liver conditions that target this cell type, which are termed cholangiopathies (i.e. primary biliary cirrhosis, primary sclerosing cholangitis and biliary atresia). In our article, we provide background information on the morphological and functional heterogeneity of cholangiocytes, summarize what is currently known about their proliferative processes, and briefly describe the diseases that target these cells. In addition, we address recent findings that suggest cholangiocyte involvement in epithelial-to-mesenchymal transformation and liver fibrosis, and propose directions for future studies.

Epithelial-mesenchymal transition: from molecular mechanisms, redox regulation to implications in human health and disease

Epithelial to mesenchymal transition (EMT) is a fundamental process, paradigmatic of the concept of cell plasticity, that leads epithelial cells to lose their polarization and specialized junctional structures, to undergo cytoskeleton reorganization, and to acquire morphological and functional features of mesenchymal-like cells. Although EMT has been originally described in embryonic development, where cell migration and tissue remodeling have a primary role in regulating morphogenesis in multicellular organisms, recent literature has provided evidence suggesting that the EMT process is a more general biological process that is also involved in several pathophysiological conditions, including cancer progression and organ fibrosis. This review offers first a comprehensive introduction to describe major relevant features of EMT, followed by sections dedicated on those signaling mechanisms that are known to regulate or affect the process, including the recently proposed role for oxidative stress and reactive oxygen species (ROS). Current literature data involving EMT in both physiological conditions (i.e., embryogenesis) and major human diseases are then critically analyzed, with a special final focus on the emerging role of hypoxia as a relevant independent condition able to trigger EMT.

Smad3 regulates Rho signaling via NET1 in the transforming growth factor-beta-induced epithelial-mesenchymal transition of human retinal pigment epithelial cells

We previously demonstrated that RhoA-dependent signaling regulates transforming growth factor-beta1 (TGF-beta1)-induced cytoskeletal reorganization in the human retinal pigment epithelial cell line ARPE-19. Smad pathways have also been shown to mediate TGF-beta1 activity. Here, we examined what regulates Rho GTPase activity and tested whether Smad signaling cross-talks with Rho pathways during TGF-beta1-induced actin rearrangement. Using small interfering RNAs, we found that NET1, the guanine nucleotide exchange factor of RhoA, is critical for TGF-beta1-induced cytoskeletal reorganization, N-cadherin expression, and RhoA activation. In ARPE-19 cells lacking NET1, TGF-beta1-induced stress fibers and N-cadherin expression were not observed. Interestingly, in dominant-negative Smad3-expressing or constitutively active Smad7 cells, TGF-beta1 failed to induce NET1 mRNA and protein expression. Consistent with these results, both dominant-negative Smad3 and constitutively active Smad7 blocked the cytoplasmic localization of NET1 and inhibited interactions between NET1 and RhoA. Finally, we found that NET1 is a direct gene target of TGF-beta1 via Smad3. Taken together, our results demonstrate that Smad3 regulates RhoA activation and cytoskeletal reorganization by controlling NET1 in TGF-beta1-induced ARPE-19 cells. These data define a new role for Smad3 as a modulator of RhoA activation in the regulation of TGF-beta1-induced epithelial-mesenchymal transitions.

Inhibition and role of let-7d in idiopathic pulmonary fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually lethal fibrotic lung disease characterized by profound changes in epithelial cell phenotype and fibroblast proliferation.

OBJECTIVES

To determine changes in expression and role of microRNAs in IPF.

METHODS

RNA from 10 control and 10 IPF tissues was hybridized on Agilent microRNA microarrays and results were confirmed by quantitative real-time polymerase chain reaction and in situ hybridization. SMAD3 binding to the let-7d promoter was confirmed by chromatin immunoprecipitation, electrophoretic mobility shift assay, luciferase assays, and reduced expression of let-7d in response to transforming growth factor-beta. HMGA2, a let-7d target, was localized by immunohistochemistry. In mice, let-7d was inhibited by intratracheal administration of a let-7d antagomir and its effects were determined by immunohistochemistry, immunofluorescence, quantitative real-time polymerase chain reaction, and morphometry.

MEASUREMENTS AND MAIN RESULTS

Eighteen microRNAs including let-7d were significantly decreased in IPF. Transforming growth factor-beta down-regulated let-7d expression, and SMAD3 binding to the let-7d promoter was demonstrated. Inhibition of let-7d caused increases in mesenchymal markers N-cadherin-2, vimentin, and alpha-smooth muscle actin (ACTA2) as well as HMGA2 in multiple epithelial cell lines. let-7d was significantly reduced in IPF lungs and the number of epithelial cells expressing let-7d correlated with pulmonary functions. HMGA2 was increased in alveolar epithelial cells of IPF lungs. let-7d inhibition in vivo caused alveolar septal thickening and increases in collagen, ACTA2, and S100A4 expression in SFTPC (pulmonary-associated surfactant protein C) expressing alveolar epithelial cells.

CONCLUSIONS

Our results indicate a role for microRNAs in IPF. The down-regulation of let-7d in IPF and the profibrotic effects of this down-regulation in vitro and in vivo suggest a key regulatory role for this microRNA in preventing lung fibrosis. Clinical trial registered with www.clinicaltrials.gov (NCT 00258544).

Epithelial-mesenchymal transition in human lungs with usual interstitial pneumonia: quantitative immunohistochemistry

Fibroblastic foci, a major histological feature of usual interstitial pneumonia (UIP), play a critical role in the development of UIP. The mechanisms involved in the formation of these foci, however, including cellular origin, remain unclear. Recent in vitro and animal studies suggested epithelial-mesenchymal transition (EMT) of alveolar epithelial cells during pulmonary fibrogenesis. The aim of the present study was to investigate the presence of EMT in patients with UIP on quantitative immunohistochemistry using pathological tissue sections. The study subjects were 13 patients with UIP pattern among 52 patients with interstitial pneumonia who underwent lung biopsy. Alveolar epithelial cells overlying fibroblastic foci expressed epithelial markers less frequently and mesenchymal markers more frequently compared with those in non-diseased control lung tissues (n= 10). Moreover, double immunostaining showed that some epithelial cells stained for both epithelial and mesenchymal markers. Furthermore, significantly higher numbers of epithelial marker-positive fibroblastic cells were found in fibroblastic foci in UIP as well as in other non-UIP fibrosing diseases than in control lung tissues. The results showed that some epithelial cells overlying fibroblastic foci lose the epithelial phenotype and gain the mesenchymal phenotype, and that some fibroblastic cells in fibroblastic foci originate from epithelial cells. But this EMT may not be specific for UIP.

Kruppel-like factor 4 inhibits epithelial-to-mesenchymal transition through regulation of E-cadherin gene expression

The Krüppel-like factor 4 (KLF4) is a transcriptional regulator of proliferation and differentiation in epithelial cells, both during development and tumorigenesis. Although KLF4 functions as a tumor suppressor in several tissues, including the colon, the role of KLF4 in breast cancer is less clear. Here, we show that KLF4 is necessary for maintenance of the epithelial phenotype in non-transformed MCF-10A mammary epithelial cells. KLF4 silencing led to alterations in epithelial cell morphology and migration, indicative of an epithelial-to-mesenchymal transition. Consistent with these changes, decreased levels of KLF4 also resulted in the loss of E-cadherin protein and mRNA. Promoter/reporter analyses revealed decreased E-cadherin promoter activity with KLF4 silencing, while chromatin immunoprecipitation identified endogenous KLF4 binding to the GC-rich/E-box region of this promoter. Furthermore, forced expression of KLF4 in the highly metastatic MDA-MB-231 breast tumor cell line was sufficient to restore E-cadherin expression and suppress migration and invasion. These findings identify E-cadherin as a novel transcriptional target of KLF4. The clear requirement for KLF4 to maintain E-cadherin expression and prevent epithelial-to-mesenchymal transition in mammary epithelial cells supports a metastasis suppressive role for KLF4 in breast cancer.

Continuously perfused, non-cross-contaminating microfluidic chamber array for studying cellular responses to orthogonal combinations of matrix and soluble signals

We present a microfluidic cell culture array with unique versatility and parallelization for experimental trials requiring perfusion cultures. Specifically, we realize a rectangular chamber array in a PDMS device with three attributes: (i) continuous perfusion; (ii) flow paths that forbid cross-chamber contamination; and (iii) chamber shielding from direct perfusion to minimize shear-induced cell behaviour. These attributes are made possible by a bridge-and-underpass architecture, where flow streams travel vertically to pass over (or under) channels and on-chip valves. The array is also designed for considerable versatility, providing subarray, row, column, or single chamber addressing. It allows for incubation with adsorbed molecules, perfusion of differing media, seeding or extraction of cells, and assay staining. We use the device to characterize different phenotypes of alveolar epithelial type II (ATII) cells, particularly the extent of epithelial-to-mesenchymal transition (EMT), a highly suspected pathway in tissue regeneration and fibrosis. Cells are cultured on combinations of matrix proteins (fibronectin or laminin by row) and soluble signals (with or without transforming growth factor-beta1 by column) with two repeats per chip. Fluorescent assays are performed in the array to assess viability, cytoskeletal organization, and cell-cell junction formation. Assay and morphological data are used to tease-out effects of cues driving each phenotype, confirming this as an effective and versatile combinatorial screening platform.

Upregulation of vimentin and aberrant expression of E-cadherin/beta-catenin complex in oral squamous cell carcinomas: correlation with the clinicopathological features and patient outcome

Oral squamous cell carcinoma is a challenging oncology problem. A reliable biomarker for metastasis or high-risk prognosis in oral cancer patients remains undefined. Using quantitative immunohistochemistry, we examined the expression of vimentin, E-cadherin, and beta-catenin in 83 oral squamous cell carcinoma patients, and the relationships between the expression of these markers and specific clinicopathological features were analysed. The high expression of vimentin was observed in 23 of 43 (53%) tumours from patients who eventually developed a recurrent tumour and was associated with recurrence and death (P<0.001 and <0.001, respectively). The decreased expression of E-cadherin was observed in 36 of 43 (84%) tumours from patients who eventually developed a recurrent tumour and was also associated with recurrence and death (P<0.001 and <0.001, respectively). Although no correlation between beta-catenin expression in whole-tumour sections and clinicopathological features was observed, decreased beta-catenin expression at the tumour invasive front was closely associated with recurrence and death (P=0.002 and 0.002, respectively). The expression of vimentin and that of E-cadherin were associated with survival and were independent prognostic factors in univariate and multivariate analyses. Our data show that the overexpression of vimentin was closely associated with recurrence and death in oral squamous cell carcinoma patients. The combination of the upregulation of vimentin and aberrant expression of E-cadherin/beta-catenin complexes at the tumour invasive front may provide a useful prognostic marker in oral squamous cell carcinoma.

Lef-1 isoforms regulate different target genes and reduce cellular adhesion

The lymphoid enhancer factor 1 (Lef-1) belongs to the nuclear transducers of canonical Wnt-signalling in embryogenesis and cancer. Lef-1 acts, in cooperation with beta-catenin, as a context-dependent transcriptional activator or repressor, thereby influencing multiple cellular functions such as proliferation, differentiation and migration. Here we report that an increased Lef-1 expression in human pancreatic cancer correlates with advanced tumour stages. In pancreatic tumours, two different transcripts of Lef-1 have been detected in various stages, as demonstrated by RT-PCR analysis. One transcript was identified as the full length Lef-1 (Lef-1 FL), whereas the second, shorter transcript lacked exon VI (Lef-1 Deltaexon VI) compared to the published sequence. Comparative analysis of these two Lef-1 variants revealed that they exhibit different cellular effects after transient expression in pancreatic carcinoma cells. Forced expression of Lef-1 Deltaexon VI inhibited E-cadherin expression in a beta-catenin-independent way. Increased amounts of Lef-1 Deltaexon VI resulted in reduced cellular aggregation and increased cell migration. Expression of Lef-1 FL, but not the newly identified Lef-1 Deltaexon VI, induced the expression of the cell cycle regulating proteins c-myc and cyclin D1 in cooperation with beta-catenin and it enhanced cell proliferation. Our findings indicate that expression of alternatively spliced Lef-1 isoforms is involved in the determination of proliferative or migratory characteristics of pancreatic carcinoma cells.

Novel links among Wnt and TGF-beta signaling and Runx2

Osteoblasts exhibit complex Wnt-induced effects that increase T cell factor (TCF)/lymphoid enhancing factor-dependent transcription in parallel with beta-catenin stabilization and nuclear factor binding to TCF response element DNA. Here we show that Wnt-dependent gene expression increases during the early phase of osteoblast differentiation in vitro, is enhanced by prostaglandin E(2) activation of transcription factor Runx2 (runt homology domain transcription factor 2), and is specifically suppressed in Runx2 antisense-depleted osteoblasts. Moreover, Wnt pathway induction increases expression of the Runx2-sensitive gene, TGF-beta type I receptor, without increasing nuclear Runx2 levels or Runx2 binding to DNA. Rather, despite an increase in beta-catenin levels, Wnt pathway induction enhances Runx2 transcriptional potential in a beta-catenin-independent way. Runx2 functionally associates with TCF-4 that lacks a beta-catenin-binding domain and is more fully activated in response to both prostaglandin E(2) and Wnt pathway induction. Wnt pathway induction increases TGF-beta type I receptor expression, yet regulates, both positively and negatively, TGF-beta signaling. Furthermore, TGF-beta signaling enhances TCF-4 and lymphoid enhancing factor-1 mRNA expression and increases TCF-4 transcriptional activity. Therefore, we propose that cross talk between the Wnt and TGF-beta pathways, which converge on Runx2, both promotes and attenuates individual aspects of osteoblast maturation.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

Tumor-host histopathologic variables, stromal myofibroblasts and risk score, are significantly associated with recurrent disease in tongue cancer

Margin status, a major prognostic parameter in oral cancer, was analyzed vis-à-vis the histopathologic parameters of risk scores and stromal myofibroblasts. Specimens of tongue carcinoma (n = 50) were submitted to a risk score assignment consisting of the worst pattern of invasion, lymphocytic infiltration, and perineural invasion. Frequency of stromal myofibroblasts (alpha-smooth muscle actin stain) was assessed. A triple immunostaining assay with E-cadherin, Ki-67 and alpha-smooth muscle actin was used to identify carcinoma cells undergoing epithelial-mesenchymal transition. Margins were considered 'clean' if the tumor was >or=5 mm away from them. Patients Collapse

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MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Cadherins/analysis
• Epithelium/pathology
• Female
• Fibroblasts/pathology
• Humans
• Male
• Mesoderm/pathology
• Middle Aged
• Neoplasm Recurrence, Local/pathology
• Risk
• Stromal Cells/pathology
• Tongue Neoplasms/etiology
• Tongue Neoplasms/pathology

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Grants Collapse

Affiliation(s)

Marilena Vered Institute of Pathology, The Chaim Sheba Medical Center, Tel Hashomer, Israel.
Alex Dobriyan
Dan Dayan
Ran Yahalom
Yoav P Talmi
Lev Bedrin
Iris Barshack
Shlomo Taicher

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alpha2-antiplasmin is associated with the progression of fibrosis

Systemic sclerosis results in tissue fibrosis due to the activation of fibroblasts and the ensuing overproduction of the extracellular matrix. We previously reported that the absence of alpha2-antiplasmin (alpha2AP) attenuated the process of dermal fibrosis; however, the detailed mechanism of how alpha2AP affects the progression of fibrosis remained unclear. The goal of the present study was to examine the role of alpha2AP in fibrotic change. We observed significantly higher levels of alpha2AP expression in the skin of bleomycin-injected systemic sclerosis model mice in comparison with the levels seen in control mice. We also demonstrated that alpha2AP induced myofibroblast differentiation, and the absence of alpha2AP attenuated the induction of myofibroblast differentiation. Moreover, we found that connective tissue growth factor induced the expression of alpha2AP through both the extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways in fibroblasts. Interestingly, alpha2AP also induced transforming growth factor-beta expression through the same pathways, and the inhibition of ERK1/2 and JNK slowed the progression of bleomycin-induced fibrosis. Our findings suggest that alpha2AP is associated with the progression of fibrosis, and regulation of alpha2AP expression by the ERK1/2 and JNK pathways may be an effective antifibrotic therapy for the treatment of systemic sclerosis.

TGF-beta1 induced epithelial to mesenchymal transition (EMT) in human bronchial epithelial cells is enhanced by IL-1beta but not abrogated by corticosteroids

Background

Chronic persistent asthma is characterized by ongoing airway inflammation and airway remodeling. The processes leading to airway remodeling are poorly understood, and there is increasing evidence that even aggressive anti-inflammatory therapy does not completely prevent this process. We sought to investigate whether TGFβ₁ stimulates bronchial epithelial cells to undergo transition to a mesenchymal phenotype, and whether this transition can be abrogated by corticosteroid treatment or enhanced by the pro-inflammatory cytokine IL-1β.

Methods

BEAS-2B and primary normal human bronchial epithelial cells were stimulated with TGFβ₁ and expression of epithelial and mesenchymal markers assessed by quantitative real-time PCR, immunoblotting, immunofluorescence microscopy and zymography. In some cases the epithelial cells were also incubated with corticosteroids or IL-1β. Results were analyzed using non-parametric statistical tests.

Results

Treatment of BEAS-2B or primary human bronchial epithelial cells with TGFβ₁ significantly reduced the expression level of the epithelial adherence junction protein E-cadherin. TGFβ₁ then markedly induced mesenchymal marker proteins such as collagen I, tenascin C, fibronectin and α-smooth muscle actin mRNA in a dose dependant manner. The process of mesenchymal transition was accompanied by a morphological change towards a more spindle shaped fibroblast cell type with a more motile and invasive phenotype. Corticosteroid pre-treatment did not significantly alter the TGFβ₁ induced transition but IL-1β enhanced the transition.

Conclusion

Our results indicate, that TGFβ₁ can induce mesenchymal transition in the bronchial epithelial cell line and primary cells. Since asthma has been strongly associated with increased expression of TGFβ₁ in the airway, epithelial to mesenchymal transition may contribute to the contractile and fibrotic remodeling process that accompanies chronic asthma.

Inflammation: a driving force speeds cancer metastasis

It has been increasingly recognized that tumor microenvironment plays an important role in carcinogenesis. Inflammatory component is present and contributes to tumor proliferation, angiogenesis, metastasis and resistance to hormonal and chemotherapy. This review highlights the role of inflammation in the tumor metastasis. We focus on the function of proinflammatory factors, particularly cytokines during tumor metastasis. Understanding of the mechanisms by which inflammation contributes to metastasis will lead to innovative approach for treating cancer. How tumor spread remains an enigma and has received great attention in recent years, as metastasis is the major cause of cancer mortality. The complex and highly selective metastatic cascade not only depends on the intrinsic properties of tumor cells but also the microenvironment that they derive from. An inflammatory milieu consisting of infiltrated immune cells and their secretory cytokines, chemokines and growth factors contribute significantly to the invasive and metastatic traits of cancer cells. Here, we review new insights into the molecular pathways that link inflammation in the tumor microenvironment to metastasis.

Expression and activity of phosphodiesterase isoforms during epithelial mesenchymal transition: the role of phosphodiesterase 4

Epithelial-mesenchymal transition (EMT) has emerged as a critical event in the pathogenesis of organ fibrosis and cancer and is typically induced by the multifunctional cytokine transforming growth factor (TGF)-beta1. The present study was undertaken to evaluate the potential role of phosphodiesterases (PDEs) in TGF-beta1-induced EMT in the human alveolar epithelial type II cell line A549. Stimulation of A549 with TGF-beta1 induced EMT by morphological alterations and by expression changes of the epithelial phenotype markers E-cadherin, cytokeratin-18, zona occludens-1, and the mesenchymal phenotype markers, collagen I, fibronectin, and alpha-smooth muscle actin. Interestingly, TGF-beta1 stimulation caused twofold increase in total cAMP-PDE activity, contributed mostly by PDE4. Furthermore, mRNA and protein expression demonstrated up-regulation of PDE4A and PDE4D isoforms in TGF-beta1-stimulated cells. Most importantly, treatment of TGF-beta1 stimulated epithelial cells with the PDE4-selective inhibitor rolipram or PDE4 small interfering RNA potently inhibited EMT changes in a Smad-independent manner by decreasing reactive oxygen species, p38, and extracellular signal-regulated kinase phosphorylation. In contrast, the ectopic overexpression of PDE4A and/or PDE4D resulted in a significant loss of epithelial marker E-cadherin but did not result in changes of mesenchymal markers. In addition, Rho kinase signaling activated by TGF-beta1 during EMT demonstrated to be a positive regulator of PDE4. Collectively, the findings presented herein suggest that TGF-beta1 mediated up-regulation of PDE4 promotes EMT in alveolar epithelial cells. Thus, targeting PDE4 isoforms may be a novel approach to attenuate EMT-associated lung diseases such as pulmonary fibrosis and lung cancer.

Fibroblast activation and myofibroblast generation in obstructive nephropathy

Obstructive nephropathy is a major cause of renal failure, particularly in newborn babies and children. After urinary tract obstruction, and under the influence of mechanical forces and cytokines produced by tubular cells and cells that have infiltrated the interstitium, resident fibroblasts undergo activation and myofibroblasts are generated from bone-marrow-derived cells, pericytes and endothelial cells. In addition, selected tubular epithelial cells can become fibroblast-like cells via epithelial-mesenchymal transition. This transition is characterized by downregulation of epithelial marker proteins such as E-cadherin, zonula occludens 1 and cytokeratin; loss of cell-to-cell adhesion; upregulation of mesenchymal markers including vimentin, alpha-smooth muscle actin and fibroblast-specific protein 1; basement membrane degradation; and migration to the interstitial compartment. All the events of epithelial-mesenchymal transition are strictly regulated by complex signaling pathways. Myofibroblasts and activated fibroblasts proliferate and produce large amounts of extracellular matrix, which accumulates in the tubular interstitium; together with tubular atrophy, this accumulation leads to interstitial fibrosis. This Review examines the molecular mechanisms of fibroblast activation and epithelial-mesenchymal transition, processes that seem to be promising targets for the prevention, or even reversal, of interstitial fibrosis and renal dysfunction associated with obstructive nephropathy.