Modulations of the epithelial phenotype during embryogenesis and cancer progression

SERPINC1, a new prognostic predictor of colon cancer, promote colon cancer progression through EMT

BACKGROUND

Liver metastasis of CRC is still the main cause of poor prognosis in patients with CRC. Previous studies have suggested that serpin family C member 1(SERPINC1) is involved in the development of a variety of tumours, but its effect on colorectal cancer progression has been poorly elucidated.

METHODS

Based on the GEO database, this study identifies the core gene SERPINC1 associated with liver metastasis in CRC. We used transcriptomic data and immunohistochemical staining to explore the expression of SERPINC1 in normal, cancer, and liver metastases tissue from CRC patients. Clinical data obtained from our hospital were used to explore the impact of SERPINC1 on the prognosis of colon cancer patients. Mechanistically, the biological functions exerted by SERPINC1 in CRC were predicted by bioinformatics, and the results were validated by the results of the experiments in vitro. Cell lines with knockdown of SERPINC1 were performed a series assay such as trans well, CCK-8 and colony formation assay to explore the relationship between SERPINC1 and proliferation and metastasis of CRC cells. Finally, the effect of SERPINC1 on the sensitivity of colon cancer patients to immune checkpoint therapy was evaluated.

RESULTS

In CRC liver metastatic tissues, we found significantly high expression of SERPINC1. Briefly, 212 CRC cohorts showed that SERPINC1 was significantly associated with TNM stage and plasma CA19-9 and CEA in CRC patients. Univariate and multivariate Cox demonstrated that SERPINC1 was significantly associated with 5-year survival after radical surgery for colorectal cancer (p < 0.001). Bioinformatics predicted that SERPINC1 affects metastasis of colon cancer through epithelial-mesenchymal transition (EMT). Colony formation assay and CCK-8 assay showed that SERPINC1 promotes malignant proliferation of CRC cells, trans well assay showed that SERPINC1 promotes distant migratory behaviour of CRC cells and protein blotting assay showed that SERPINC1 may promote migration by promoting the TGF-β1-mediated EMT of CRC cells. In addition, several immunotherapy cohorts also reflected that the expression of SERPINC1 reduced the sensitivity of CRC patients to immune checkpoint therapy.

CONCLUSION

Our study identified SERPINC1 as a novel liver metastasis-associated gene in CRC. Targeting SERPINC1 may be a novel therapeutic strategy for patients with liver metastases from CRC.

How studies in developmental epithelial-mesenchymal transition and mesenchymal-epithelial transition inspired new research paradigms in biomedicine

Epithelial-mesenchymal transition (EMT) and its reverse mechanism, mesenchymal-epithelial transition (MET), are evolutionarily conserved mechanisms initially identified in studies of early metazoan development. EMT may even have been established in choanoflagellates, the closest unicellular relative of Metazoa. These crucial morphological transitions operate during body plan formation and subsequently in organogenesis. These findings have prompted an increasing number of investigators in biomedicine to assess the importance of such mechanisms that drive epithelial cell plasticity in multiple diseases associated with congenital disabilities and fibrosis, and, most importantly, in the progression of carcinoma. EMT and MET also play crucial roles in regenerative medicine, notably by contributing epigenetic changes in somatic cells to initiate reprogramming into stem cells and their subsequent differentiation into distinct lineages.

Long non-coding RNA Lnc-LALC facilitates colorectal cancer liver metastasis via epigenetically silencing LZTS1

Colorectal cancer (CRC) is one of the most common cancers around the world and endangers human health seriously. Liver metastasis is an important factor affecting the long-term prognosis of CRC and the specific mechanism of CRLM (colorectal cancer with liver metastasis) is not fully understood. LZTS1 has been found dysregulated in many cancers, especially in CRC. Theories suggested that hypermethylation of the promoter regions of LZTS1 was responsible for LZTS1 abnormal expression in multiple malignant tumors. Although the role of LZTS1 in CRC cell proliferation has been reported, its role in CRLM remains unclear. Numerous studies reported Long non-coding RNA (lncRNA) could regulate the gene expression level by regulating gene methylation status in many tumors. However, whether there were lncRNAs could change the methylation status of LZTS1 or not in CRLM was unknown. In this study, we aimed to investigate whether there are lncRNAs can regulate the expression of LZTS1 through affecting DNA methylation in CRLM. We found that upregulated Lnc-LALC in CRC was negatively correlated with LZTS1 expression, and Lnc-LALC could regulate LZTS1 expression in both mRNA and protein level in our study. Functionally, Lnc-LALC enhanced the CRC cells metastasis ability in vitro and vivo through inhibiting the expression of LZTS1. Furthermore, the precise mechanisms exploration showed that lnc-LALC could recruit DNA methyltransferases (DNMTs) to the LZTS1 promoter by combining with Enhancer of zeste homolog 2(EZH2) and then altered the expression of LZTS1 via DNMTs-mediated DNA methylation. Collectively, our data demonstrated the important role of Lnc-LALC/ LZTS1 axis in CRLM development.

An Epithelial-Mesenchymal Transition (EMT) Preoperative Nomogram for Prediction of Lymph Node Metastasis in Bladder Cancer (BLCA)

Lymph node (LN) metastasis is a lethal independent risk factor for patients with bladder cancer (BLCA). Accurate evaluation of LN metastasis is of vital importance for disease staging, treatment selection, and prognosis prediction. Several histopathologic parameters are available to predict LN metastasis postoperatively. To date, medical imaging techniques have made a great contribution to preoperatively diagnosis of LN metastasis, but it also exhibits substantial false positives. Therefore, a reliable and robust method to preoperatively predict LN metastasis is urgently needed. Here, we selected 19 candidate genes related to epithelial-mesenchymal transition (EMT) across the LN metastasis samples, which was previously reported to be responsible for the subtype transition and correlation with malignancy and prognosis of BLCA, to establish an EMT-LN signature through LASSO logistic regression analysis. The EMT-LN signature could significantly predict LN metastasis with high accuracy in the TCGA-BLCA cohort, as well as several independent cohorts. As integrating with C3orf70 mutation, we developed an individualized prediction nomogram based on the EMT-LN signature. The nomogram exhibited good discrimination on LN metastasis status, with AUC of 71.7% and 75.9% in training and testing datasets of the TCGA-BLCA cohort. Moreover, the EMT-LN nomogram displayed good calibration with p > 0.05 in the Hosmer-Lemeshow goodness of fit test. Decision curve analysis (DCA) revealed that the EMT-LN nomogram was of high potential for clinical utility. In summary, we established an EMT-LN nomogram integrating an EMT-LN signature and C3orf70 mutation status, which acted as an easy-to-use tool to facilitate preoperative prediction of LN metastasis in BLCA individuals.

The association between KLF4 as a tumor suppressor and the prognosis of hepatocellular carcinoma after curative resection

Krüppel-like factor 4 (KLF4), a zinc-finger transcription factor in klfs family, is known for its crucial role in regulating cell growth, proliferation, and differentiation. This research aimed to explore the prognostic significance of KLF4 in hepatocellular carcinoma’s (HCC) patients after curative resection and the role of KLF4 in HCC progression. There were 185 HCC patients who had hepatectomy from July 2010 to July 2011 included in this study. KLF4 expression was detected by microarray immunohistochemical technique, western blot, and qRT-PCR. Then, the correlation between the prognosis of patients and KLF4 expression was evaluated based on patients’ follow-up data. The research found KLF4 expression was significantly downregulated in HCC tissues compared to para-tumorous tissues. More importantly, the overall survival rate (OS) and recurrence-free survival rate (RFS) of HCC patients with low KLF4 expression were both significantly decreased compared to those with a high level of KLF4. Further function and mechanism analysis showed that KLF4 could inhibit the proliferation, migration, invasion and epithelial-mesenchymal transition of HCC cells. The study revealed that KLF4 was not only a tumor suppressor in HCC but also can be regarded as a valuable prognostic factor and potential biological target for diagnosis and treatment in HCC patients.

HER4 promotes the progression of colorectal cancer by promoting epithelial‑mesenchymal transition

Colorectal cancer (CRC) remains one of the most common cancer types worldwide. A few previous studies have examined whether HER4 may promote the progression of CRC. The present study examined the associations among the expression levels of members of the HER family, and investigated the potential mechanism underlying the function of HER4 in CRC cells. Immunohistochemistry analysis was conducted to detect the expression levels of HER family members in patients with CRC. HER4 expression was knocked down using short hairpin RNA in HCT116 cells, and confirmed by quantitative PCR and western blotting. The proliferation and adhesion of CRC cells were analyzed by CCK-8 assays and adhesive assays, respectively. Flow cytometry was used to measure cell apoptosis. Western blotting and immunofluorescence staining in CRC cells were performed to identify proteins related to epithelial-mesenchymal transition. The proportion of patients with CRC presenting positive expression of the HER family members epidermal growth factor receptor (EGFR), HER2, HER3 and HER4 were 72.1, 45.2, 43.8 and 34.2%, respectively. No relationship was found between HER4 and EGFR, HER2 or HER3 expression. Higher expression of HER4 was positively associated with lymph node metastasis (P=0.039). In the present study, HER4 expression was found to be associated with an unfavorable clinical outcome in patients with CRC (P_logrank=0.020). Cell proliferation was inhibited, and apoptosis was increased following HER4 knockdown. Furthermore, HER4 knockdown increased the expression of E-cadherin and decreased the expressions of N-cadherin and vimentin (P<0.05). HER4 expression was found to be unrelated to other HER family members. In the present study, positive expression of HER4 promoted the progression of CRC through epithelial-mesenchymal transition.

Upregulated RACK1 attenuates gastric cancer cell growth and epithelial-mesenchymal transition via suppressing Wnt/β-catenin signaling

Purpose: As there have been few studies on the effects of the receptor for activated C kinase 1 (RACK1) on gastric cancer (GC), we aimed to explore such effects and the mechanism that may be involved.

Patients and methods: Normal gastric epithelial cells and six GC cell lines were used to detect the mRNA expression of RACK1. Overexpressing RACK1 was transfected in HGC27 and MGC803 cells. The effects of overexpressing RACK1 on cell viability, migration, and invasion were determined by cell counting kit-8, wound scratch, and Transwell assay, respectively. The expressions of epithelial–mesenchymal transition (EMT) and Wnt/β-catenin signaling related genes were detected using quantitative real-time PCR or Western blot. Wnt pathway agonist LiCl was added into RACK1 overexpressing GC cells, and then cell viability, migration, and invasion were also detected.

Results: RACK1 was downregulated in GC cell lines. Under the circumstance that overexpressing RACK1 was successfully transfected in the two lowest RACK1-expressing GC cells, significant inhibition of cell viability, migration, and invasion, promotion to the mRNA and protein expression of E-cadherin, as well as a decrease in the N-cadherin and Snail expressions could be observed. Overexpressing RACK1 also enhanced the protein level of phosphorylation-β-catenin/β-catenin and attenuated c-Jun protein expression. Additionally, LiCl could partially reverse the inhibitory effects of cell viability, migration and invasion by overexpressing RACK.

Conclusion: We found RACK1 possibly inhibited epithelial–mesenchymal transition of GC cells through limitation of the Wnt/β-catenin pathway, thereby suppressing cell migration and invasion; RACK1 could also suppress cell growth.

Reduced USP33 expression in gastric cancer decreases inhibitory effects of Slit2-Robo1 signalling on cell migration and EMT

OBJECTIVES

Gastric cancer (GC) is one of the most common cancers in the world, causing a large number of deaths every year. The Slit-Robo signalling pathway, initially discovered for its critical role in neuronal guidance, has recently been shown to modulate tumour invasion and metastasis in several human cancers. However, the role of Slit-Robo signalling and the molecular mechanisms underlying its role in the pathogenesis of gastric cancer remains to be elucidated.

MATERIALS AND METHODS

Slit2, Robo1 and USP33 expressions were analysed in datasets obtained from the Oncomine database and measured in human gastric cancer specimens. The function of Slit2-Robo1-USP33 signalling on gastric cancer cells migration and epithelial-mesenchymal transition (EMT) was studied both in vitro and in vivo. The mechanism of the interaction between Robo1 and USP33 was explored by co-IP and ubiquitination protein analysis.

RESULTS

The mRNA and protein levels of Slit2 and Robo1 are lower in GC tissues relative to those in adjacent healthy tissues. Importantly, Slit2 inhibits GC cell migration and suppresses EMT process in a Robo-dependent manner. The inhibitory function of Slit2-Robo1 is mediated by ubiquitin-specific protease 33 (USP33) via deubiquitinating and stabilizing Robo1. USP33 expression is decreased in GC tissues, and reduced USP33 level is correlated with poor patient survival.

CONCLUSIONS

Our study reveals the inhibitory function of Slit-Robo signalling in GC and uncovers a role of USP33 in suppressing cancer cell migration and EMT by enhancing Slit2-Robo1 signalling. USP33 represents a feasible choice as a prognostic biomarker for GC.

Capillary morphogenesis gene 2 maintains gastric cancer stem-like cell phenotype by activating a Wnt/β-catenin pathway

A growing body of evidence shows that the development and progression of gastric cancer (GC) is mainly associated to the presence of gastric cancer stem-like cells (GCSLCs). However, it is unclear how GCSLC population is maintained. This study aimed to explore the role of capillary morphogenesis gene 2 (CMG2) in GCSLC maintenance and the relevance to GC progression. We found that CMG2 was highly expressed in GC tissues and the expression levels were associated with the invasion depth and lymph node metastasis of GC, and inversely correlated with the survival of GC patients. Sorted CMG2^High GC cells preferentially clustered in CD44^High stem-like cell population, which expressed high levels of stemness-related genes with increased capabilities of self-renewal and tumorigenicity. Depletion of CMG2 gene resulted in reduction of GCSLC population with attenuated stemness and decrease of invasive and metastatic capabilities with subdued epithelial–mesenchymal transition phenotype in GC cells. Mechanistically, CMG2 interacted with LRP6 in GCSLCs to activate a Wnt/β-catenin pathway. Thus, our results demonstrate that CMG2 promotes GC progression by maintaining GCSLCs and can serve as a new prognostic indicator and a target for human GC therapy.

Discoidin domain receptor 1: New star in cancer-targeted therapy and its complex role in breast carcinoma

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by various types of collagens that performs a critical role in cell attachment, migration, survival and proliferation. The functions of DDR1 in various types of tumor have been studied extensively. However, in breast carcinoma, the roles of collagen-evoked DDR1 remain ill defined. Although a number of studies have reported that DDR1 promotes apoptosis and inhibits migration in breast carcinoma, it has also been reported to be associated with tumor cell survival, chemoresistance to genotoxic drugs and the facilitation of invasion. The present review summarizes current progress and the complex effects of DDR1 in the field of breast carcinoma, and presents DDR1 as a promising therapeutic target.

Overexpression of stromal interaction molecule 1 may promote epithelial‑mesenchymal transition and indicate poor prognosis in gastric cancer

The aim of the present study was to investigate the prognostic significance of stromal interaction molecule 1 (STIM1) expression in gastric cancer (GC) and examine the association between STIM1 and epithelial-mesenchymal transition (EMT). Immunohistochemical staining was performed to detect STIM1, E-cadherin, β-catenin and matrix metalloproteinase-9 (MMP-9) in 170 GC and 35 adjacent healthy gastric tissue samples. Positive staining of STIM1, E-cadherin, β-catenin and MMP-9 in GC tissues was significantly greater compared with adjacent healthy tissues (P<0.05). Clinicopathological analysis revealed that STIM1 expression was significantly associated with LNM (P<0.001) and tumor-node-metastasis stage (P=0.01). The overall survival rate was significantly reduced in STIM1-positive compared with STIM1-negative patients (P=0.043). Cox regression analysis indicated that STIM1 expression and LNM were independent prognostic factors for GC. Chi-square tests suggested that STIM1 expression in GC tissues was significantly associated with E-cadherin (P<0.001) and β-catenin (P<0.001), whereas no association was observed between STIM1 and MMP-9 expression (P>0.05). In conclusion, the results of the present study suggested that STIM1 may be a valuable prognostic marker in GC patients, and that STIM1 may increase GC motility and invasiveness by promoting epithelial-mesenchymal transition.

PI3K/AKT/mTOR and sonic hedgehog pathways cooperate together to inhibit human pancreatic cancer stem cell characteristics and tumor growth

Cancer stem cells (CSCs) play major roles in cancer initiation, progression, and metastasis. It is evident from growing reports that PI3K/Akt/mTOR and Sonic Hedgehog (Shh) signaling pathways are aberrantly reactivated in pancreatic CSCs. Here, we examined the efficacy of combining NVP-LDE-225 (PI3K/mTOR inhibitor) and NVP-BEZ-235 (Smoothened inhibitor) on pancreatic CSCs characteristics, microRNA regulatory network, and tumor growth. NVP-LDE-225 co-operated with NVP-BEZ-235 in inhibiting pancreatic CSC's characteristics and tumor growth in mice by acting at the level of Gli. Combination of NVP-LDE-225 and NVP-BEZ-235 inhibited self-renewal capacity of CSCs by suppressing the expression of pluripotency maintaining factors Nanog, Oct-4, Sox-2 and c-Myc, and transcription of Gli. NVP-LDE-225 co-operated with NVP-BEZ-235 to inhibit Lin28/Let7a/Kras axis in pancreatic CSCs. Furthermore, a superior interaction of these drugs was observed on spheroid formation by pancreatic CSCs isolated from Pan^kras/p53 mice. The combination of these drugs also showed superior effects on the expression of proteins involved in cell proliferation, survival and apoptosis. In addition, NVP-LDE-225 co-operated with NVP-BEZ-235 in inhibiting EMT through modulation of cadherin, vimentin and transcription factors Snail, Slug and Zeb1. In conclusion, these data suggest that the combined inhibition of PI3K/Akt/mTOR and Shh pathways may be beneficial for the treatment of pancreatic cancer.

FOXQ1 promotes gastric cancer metastasis through upregulation of Snail

Gastric cancer (GC) is one of the most common cancers, and the second most common cause of cancer deaths worldwide. Forkhead box Q1 (FOXQ1) is a member of the forkhead transcription factor family and its upregulation is closely correlated with tumor progression and prognosis of multiple cancer types, including GC. FOXQ1 has been shown to regulate EMT and function in human cancers. However, the role of FOXQ1 in regulating EMT in GC and the exactly mechanism has not been clarified. The purpose of this study was to investigate the effects of FOXQ1 on EMT in human GC. FOXQ1 protein was detected by immunohistochemistry in human GC specimens and their clinical significance evaluated. We examined the cell biology and molecular biology changes after overexpression and knockdown of FOXQ1 in gastric cancer cells in vitro. To further understand the underlying mechanisms of EMT promoted by FOXQ1, we examined the changes of target genes of FOXQ1 after overexpression and knockdown of FOXQ1 in gastric cancer cells. In the present study, we demonstrate that FOXQ1 is overexpressed in GC tissues and its expression level is closely correlated with histologic differentiation, pTNM stage, and lymphatic metastasis of GC. Kaplan-Meier survival analysis showed that a high expression level of FOXQ1 resulted in a significantly poor prognosis of GC patients. FOXQ1 modulated GC cell invasion in vitro, and induced E-cadherin repression. FOXQ1 also upregulated the expression of vimentin in vitro. The Snail signaling pathway was likely involved in the induction of EMT by FOXQ1 in GC. Our results demonstrate that FOXQ1 is a prognostic marker for patients with GC, FOXQ1 over-expression is involved in acquisition of the mesenchymal phenotype of gastric cancer cells, and that subsequent Snail expression is essential for induction of EMT. The results suggest that FOXQ1 is a potential therapeutic target for the development of therapies for GC.

WIP is necessary for matrix invasion by breast cancer cells

Actin filament assembly and reorganisation during cell migration and invasion into extracellular matrices is a well-documented phenomenon. Among actin-binding proteins regulating its polymerisation, the members of the WASP (Wiskott Aldrich Syndrome Protein) family are generally thought to play the most significant role in supporting cell invasiveness. In situ, cytosolic N-WASP (neural WASP) is associated with a partner protein termed WIP (WASP Interacting Protein) that is bound to the N-terminal domain of N-WASP. Despite much effort, rather little is known about the role of WIP in regulating N-WASP and consequent actin-filament assembly. Even less is known about the function of WIP within the specialised cell adhesion and attachment structures known as podosomes and invadopodia. In particular, whilst the interaction of WIP with known participants in the development and maturation of invadopodia such as N-WASP, the Arp2/3 complex and cortactin has been described, little is known concerning the direct contribution of WIP to invadopodia and its potential role as a regulator of cancer cell invasion. In this report, we use 2D and 3D culture systems to describe the role played by WIP in modulating the morphology and invasiveness of metastatic breast cancer cells in vitro, as well as its effect on the process of mesenchymal-epithelial transition (MET) seen in these cells. We demonstrate that WIP is necessary for invadopodium formation and matrix degradation by basal breast cancer cells, but not sufficient to induce invasiveness in luminal cells.

Epithelial-mesenchymal transition and drug resistance: role, molecular mechanisms, and therapeutic strategies

Chemotherapy is an important therapeutic option for most cancer patients; however, one major obstacle is the occurrence of drug resistance which usually leads to failure of the chemotherapy. Emerging evidence suggests that there are intricate links between epithelial-mesenchymal transition (EMT)-type cells and drug resistance in tumors. The process of drug resistance can be regulated by a diverse array of cytokines and growth factors, higher apoptotic threshold, aerobic glycolysis, regions of hypoxia, and elevated activity of drug efflux transporters. Moreover, recent reports have indicated that the emergence of drug resistance may occur as a result of EMT. In this regard, most drug-resistant cancers contain a subpopulation of cells with stem-like and mesenchymal features that are resistant to chemotherapy. In this review, we will explain potential mechanisms for the association between EMT induction and the emergence of drug resistance, and discuss new approaches and drugs for the clinical management of drug-resistant cancer induced by EMT.

Regulation of EMT by KLF4 in gastrointestinal cancer

Gastrointestinal (GI) cancer is characterized by its aggressiveness, but the underlying mechanism is not fully understood. Studies reveal that epithelial to mesenchymal transition (EMT), which is regulated by a series of transcription factors and signaling pathways, is strongly associated with GI cancer cell proliferation, invasion and metastasis. Importantly, EMT is a product of crosstalk between signaling pathways. Krüppel-like factor 4 (KLF4), a zinc finger-type transcription factor, is decreased or lost in most GI cancers. By transcriptionally regulating its downstream target genes, KLF4 plays important roles of GI cancer tumorigenesis, proliferation and differentiation. In this review, we focus on the mechanism of KLF4 in GI cancer EMT, and demonstrate that through crosstalk with TGF-β, Notch, and Wnt signaling pathways, KLF4 negatively regulates EMT of GI cancers. Finally, we indicate the challenging new frontiers for KLF4 which contributes to better understanding of the mechanism of GI cancer aggressiveness.

Role of the epithelial-mesenchymal transition in bladder cancer: from prognosis to therapeutic target

Bladder cancer (BC) is the second most common malignancy of urological organs. However, patients with non-muscle-invasive BC are at high risk of recurrence and progression into muscle-invasive BC, and the prognosis of patients with muscle-invasive BC is limited by the high rate of metastasis. The epithelial-mesenchymal transition (EMT) is characterized by loss of cell-to-cell adhesion and cell polarity and is closely associated with the invasion and metastasis of several cancers. Given the multifocality and high rates of relapse, progression, and metastasis of BC, the EMT is likely to participate in BC as well. Numerous factors associate with the EMT, and the key regulators of the EMT are E-cadherin, N-cadherin, Twist, Snail, Slug, Zeb-1, Zeb-2, vimentin, and microRNAs. This review focuses on the current concepts regarding the EMT in cancer and the evidence for involvement of the EMT in BC. Several potential EMT targets that may be useful in the treatment of BC are also described.

Breast cancer stem cells and epithelial mesenchymal plasticity - Implications for chemoresistance

Tumour heterogeneity is a key characteristic of cancer and has significant implications relating to tumour response to chemotherapy as well as patient prognosis and potential relapse. It is being increasingly accepted that tumours are clonal in origin, suggestive of a tumour arising from a deregulated or mutated cell. Cancer stem cells (CSC) possess these capabilities, and with appropriate intracellular triggers and/or signalling from extracellular environments, can purportedly differentiate to initiate tumour formation. Additionally through epithelial mesenchymal plasticity (EMP), where cells gain and maintain characteristics of both epithelial and mesenchymal cell types, epithelial-derived tumour cells have been shown to de-differentiate to acquire cancer stem attributes, which also impart chemotherapy resistance. This new paradigm places EMP centrally in the process of tumour progression and metastasis, as well as modulating drug response to current forms of chemotherapy. Furthermore, EMP and CSCs have been identified in cancers arising from different tissue types making it a possible generic therapeutic target in cancer biology. Using breast cancer (BrCa) as an example, we summarise here the current understanding of CSCs, the role of EMP in cancer biology - especially in CSCs and different molecular subtypes, and the implications this has for current and future cancer treatment strategies.

FOXC2 expression links epithelial-mesenchymal transition and stem cell properties in breast cancer

Resistance to chemotherapy and metastases are the major causes of breast cancer-related mortality. Moreover, cancer stem cells (CSC) play critical roles in cancer progression and treatment resistance. Previously, it was found that CSC-like cells can be generated by aberrant activation of epithelial-mesenchymal transition (EMT), thereby making anti-EMT strategies a novel therapeutic option for treatment of aggressive breast cancers. Here, we report that the transcription factor FOXC2 induced in response to multiple EMT signaling pathways as well as elevated in stem cell-enriched factions is a critical determinant of mesenchymal and stem cell properties, in cells induced to undergo EMT- and CSC-enriched breast cancer cell lines. More specifically, attenuation of FOXC2 expression using lentiviral short hairpin RNA led to inhibition of the mesenchymal phenotype and associated invasive and stem cell properties, which included reduced mammosphere-forming ability and tumor initiation. Whereas, overexpression of FOXC2 was sufficient to induce CSC properties and spontaneous metastasis in transformed human mammary epithelial cells. Furthermore, a FOXC2-induced gene expression signature was enriched in the claudin-low/basal B breast tumor subtype that contains EMT and CSC features. Having identified PDGFR-β to be regulated by FOXC2, we show that the U.S. Food and Drug Administration-approved PDGFR inhibitor, sunitinib, targets FOXC2-expressing tumor cells leading to reduced CSC and metastatic properties. Thus, FOXC2 or its associated gene expression program may provide an effective target for anti-EMT-based therapies for the treatment of claudin-low/basal B breast tumors or other EMT-/CSC-enriched tumors.

Epithelial-mesenchymal transition as a fundamental mechanism underlying the cancer phenotype

Epithelial-mesenchymal transition (EMT) is a complex process involved in embryonic development, wound healing and carcinogenesis. During this process, epithelial cells lose their defining characteristics and acquire mesenchymal properties: loss of cell-cell adhesion; increased motility and invasiveness; resistance to apoptosis and changes in cellular morphology. EMT has been implicated as a driver of metastasis and tumour invasion, as this process allows cells to detach from their niche and migrate through blood and lymphatic vessels to invade different organs. This transition involves a diverse range of transcription factors, including Twist, Snail and ZEB1, and downstream transcriptional targets, including E-cadherin, β-catenin, fibronectin and vimentin. Recent evidence indicates that cancer stem cells are required for metastatic tumours to become established at a distant site, and that cancer cells undergoing EMT may develop stem-cell characteristics as well as increased invasive potential. The role of EMT in cancer biology is newly emerging in the human field, and to date very little has been done in veterinary medicine. EMT may therefore be an important molecular determinant of tumour metastasis, and further understanding of this process may lead to novel drug targets to be exploited in both veterinary and human medicine.

The genome-wide expression profile of gastric epithelial cells infected by naturally occurring cagA isogenic strains of Helicobacter pylori

Helicobacter pylori (H. pylori) is associated with the development of gastric adenocarcinoma and lymphoma. However, the mechanisms through which H. pylori induces gastric mucosal lesions are not well defined. This study was conducted to evaluate the effect of the oncoprotein CagA on gastric cancer cells using whole-genome expression arrays. Human gastric epithelial (AGS) cells were incubated with CagA-positive H. pylori strains (147C (phosphorylated CagA) or 147A (dephosphorylated CagA)), and total protein and RNA were collected. The effects of phosphorylated and unphosphorylated CagA on AGS cells were then evaluated using Western blotting and microarray analysis. The expression levels of the genome profiles of AGS cells infected with 147A were compared with those of AGS cells infected with 147C. The expression profiles of the differentially expressed genes were grouped, and their expression patterns were validated via quantitative real-time PCR. Up- and down-regulated genes mainly included epithelial mesenchymal transition (EMT)-related genes. The results of the microarray analysis revealed that phosphorylated and unphosphorylated CagA may affect EMT in part through gene expression. This suggests that the intracellularly translocated CagA may be involved in EMT, resulting in differential expression of genes independent on the phosphorylation status of CagA.

NEDD9 is a positive regulator of epithelial-mesenchymal transition and promotes invasion in aggressive breast cancer

Epithelial to mesenchymal transition (EMT) plays an important role in many biological processes. The latest studies revealed that aggressive breast cancer, especially the triple-negative breast cancer (TNBC) subtype was frequently associated with apparent EMT, but the mechanisms are still unclear. NEDD9/HEF1/Cas-L is a member of the Cas protein family and was identified as a metastasis marker in multiple cancer types. In this study, we wished to discern the role of NEDD9 in breast cancer progression and to investigate the molecular mechanism by which NEDD9 regulates EMT and promotes invasion in triple-negative breast cancer. We showed that expression of NEDD9 was frequently upregulated in TNBC cell lines, and in aggressive breast tumors, especially in TNBC subtype. Knockdown of endogenous NEDD9 reduced the migration, invasion and proliferation of TNBC cells. Moreover, ectopic overexpression of NEDD9 in mammary epithelial cells led to a string of events including the trigger of EMT, activation of ERK signaling, increase of several EMT-inducing transcription factors and promotion of their interactions with the E-cadherin promoter. Data presented in this report contribute to the understanding of the mechanisms by which NEDD9 promotes EMT, and provide useful clues to the evaluation of the potential of NEDD9 as a responsive molecular target for TNBC chemotherapy.

Epithelial mesenchymal transition traits in human breast cancer cell lines parallel the CD44(hi/)CD24 (lo/-) stem cell phenotype in human breast cancer

We review here the recently emerging relationship between epithelial-mesenchymal transition (EMT) and breast cancer stem cells (BCSC), and provide analyses of published data on human breast cancer cell lines, supporting their utility as a model for the EMT/BCSC state. Genome-wide transcriptional profiling of these cell lines has confirmed the existence of a subgroup with mesenchymal tendencies and enhanced invasive properties ('Basal B'/Mesenchymal), distinct from subgroups with either predominantly luminal ('Luminal') or mixed basal/luminal ('Basal A') features (Neve et al. Cancer Cell, 2006). A literature-derived EMT gene signature has shown specific enrichment within the Basal B subgroup of cell lines, consistent with their over-expression of various EMT transcriptional drivers. Basal B cell lines are found to resemble BCSC, being CD44(high)CD24(low). Moreover, gene products that distinguish Basal B from Basal A and Luminal cell lines (Basal B Discriminators) showed close concordance with those that define BCSC isolated from clinical material, as reported by Shipitsin et al. (Cancer Cell, 2007). CD24 mRNA levels varied across Basal B cell lines, correlating with other Basal B Discriminators. Many gene products correlating with CD24 status in Basal B cell lines were also differentially expressed in isolated BCSC. These findings confirm and extend the importance of the cellular product of the EMT with Basal B cell lines, and illustrate the value of analysing these cell lines for new leads that may improve breast cancer outcomes. Gene products specific to Basal B cell lines may serve as tools for the detection, quantification, and analysis of BCSC/EMT attributes.

Reduced cell death, invasive and angiogenic features conferred by BRCA1-deficiency in mammary epithelial cells transformed with H-Ras

To investigate the role of tumor suppressors BRCA1 and p53 proteins in human breast tumorigenesis, we transformed immortalized human mammary epithelial cells, MCF10A, with or without BRCA1/p53 gene-specific knockdowns. Stable knockdown of BRCA1 alone in MCF10A cells led to centrosome amplification, impaired p53 protein stability, increased sensitivity towards DNA-damaging agents, defective chromosomal condensation at mitosis and elevated protein levels of cyclin D1 and c-myc. While over-expression of mutant H-Ras transformed MCF10A cells, depletion of BRCA1 dramatically enhanced the in vivo tumorigenesis that was associated with higher levels of VEGF, enhanced vascularization and less apoptosis in the BRCA1-deficient Ras-transformed tumors. The Ras-transformed BRCA1-deficient tumors exhibited features of the epithelial-to-mesenchymal transition, appeared to secrete matrix metalloproteases as visualized by in vivo bio-imaging of tumors using fluorescent probe MMP680, and were locally metastatic to lymph nodes. Our results suggest that loss of BRCA1 function may contribute to the aggressiveness of Ras-MAPK driven human breast cancer with associated increase in levels of cyclin D1 and c-myc, enhanced MAPK activity, angiogenic potential & invasiveness. This mammary xenograft tumor model may be useful as a tool to understand human breast tumor angiogenesis and metastasis, as well as to test candidate therapeutics.

Molecular events associated with epithelial to mesenchymal transition of nasopharyngeal carcinoma cells in the absence of Epstein-Barr virus genome

Epithelial-mesenchymal transition (EMT) is an important process in tumor metastasis. The EMT-related events associated with metastasis of NPC in the absence of EBV have not been elucidated. We established an EBV-negative NPC cell line from a bone marrow biopsy of an NPC patient. Using a Matrigel system we isolated an invasive and non-invasive sublines, designated NPC-BM29 and NPC-BM00. NPC-BM29 acquired an invasive-like phenotype characterized by EMT, marked by down-regulation of E-cadherin and β-catenin with concomitant increased expression of Ets1. NPC-BM29 cells expressed ≥ 10-fold higher of MMP-9 than NPC-BM00 cells. NPC-BM29 cells grew better in 2% serum than NPC-BM00 cells, with a population doubling-time of 26.8 h and 30.7 h, respectively. A marked reduction in colony-formation ability of NPC-BM00 cells compared to NPC-BM29 was observed. Wound-healing assay revealed that NPC-BM29 cells displayed higher motility than NPC-BM00 and the motility was further enhanced by cell treatment with TPA, a PKC activator. Cell surface markers and tumor-associated molecules, AE3, MAK6 and sialyl-Tn, were up-regulated in NPC-BM29 cells, whereas the expression of HLA-DR and CD54 was significantly increased in NPC-BM00 cells. NPC-BM29 consistently released higher levels of IL-8 and IL-10 than NPC-BM00, with low levels of IL-1α expression in both cell lines. Higher level of VEGF production was detected in NPC-BM00 than NPC-BM29 cells. These data show that EBV is not required for exhibiting multiple metastatic phenotypes associated with EMT. More studies that target right molecules/signalings associated with the EMT may offer new therapeutic intervention options for NPC invasion and metastasis.

The epithelial-to-mesenchymal transition and cancer stem cells: a coalition against cancer therapies

During cancer progression, some cells within the primary tumor may reactivate a latent embryonic program known as epithelial-to-mesenchymal transition (EMT). Through EMT, transformed epithelial cells can acquire the mesenchymal traits that seem to facilitate metastasis. Indeed, there is accumulating evidence that EMT and mesenchymal-related gene expression are associated with aggressive breast cancer subtypes and poor clinical outcome in breast cancer patients. More recently, the EMT program was shown to endow normal and transformed mammary epithelial cells with stem cell properties, including the ability to self-renew and efficiently initiate tumors. This link between EMT and stem cells may have numerous implications in the progression of breast tumors. The EMT process may facilitate the generation of cancer cells with the mesenchymal traits needed for dissemination as well as the self-renewal properties needed for initiation of secondary tumors. Breast cancer stem cells are resistant to many conventional cancer therapies, which can promote tumor relapse. Therefore, the generation of cancer stem cells by EMT may promote the development of refractory and resistant breast tumors. The purpose of this review is to summarize the findings related to EMT and stem cells in cancer progression and therapy resistance.

Prognostic significance of epithelial-mesenchymal and mesenchymal-epithelial transition protein expression in non-small cell lung cancer

PURPOSE

In carcinomas, invasive tumor growth is accompanied by desmoplastic stroma reaction and facilitated by epithelial-mesenchymal transition (EMT) of cancer cells. We investigated the prognostic significance of the EMT indicator proteins periostin and vimentin in comparison with versican, a putative indicator of the opposite mechanism mesenchymal-epithelial transition (MET), and to the desmoplasia proteins collagen and elastin in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Tumor of 533 patients with surgically resected NSCLC was used for analysis of stromal and epithelial protein expression by immunohistochemistry (EMT-MET proteins) and Elastica van Gieson histochemical staining (collagen and elastin). A semiquantitative sum scoring system was done on three tissue microarrays.

RESULTS

Of the 533 patients, 48% had squamous cell carcinoma, 47% adenocarcinoma, and 5% adenosquamous carcinoma. High expression of periostin in either stroma or tumor epithelia, independently scored by two pathologists, correlated with male gender, higher stage, higher pT category, and larger tumor size, and in only stroma with tumor relapse. High expression of versican in either stroma or epithelia as well as of stromal collagen had fewer but concordant associations with advanced tumor and periostin, respectively. High expression of elastin was oppositely associated with less advanced disease. Associations of high vimentin were inconsistent (all P values < 0.05). High stromal periostin was found to be a prognostic factor for decreased progression-free survival on univariate analysis (P = 0.007).

CONCLUSIONS

Because up-regulation is frequently observed in the stromal and epithelial tumor compartment, EMT-MET indicator proteins may be integrated in progression models of NSCLC.

TGF-beta and BMP7 interactions in tumour progression and bone metastasis

The skeleton is the second most frequent site of metastasis. However, only a restricted number of solid cancers, especially those of the breast and prostate, are responsible for the majority of the bone metastases. Metastatic bone disease is a major cause of morbidity, characterised by severe pain and high incidence of skeletal and haematopoietic complications (fractures, spinal cord compression and bone marrow aplasia) requiring hospitalisation. Despite the frequency of skeletal metastases, the molecular mechanisms for their propensity to colonise bone are poorly understood and treatment options are often unsatisfactory. TGF-beta and the signalling pathway it controls appears to play major roles in the pathogenesis of many carcinomas, both in their early stages, when TGF-beta acts to arrest growth of many cell types, and later in cancer progression when it contributes, paradoxically, to the phenotype of tumour invasiveness. Here we discuss some novel insights of the TGF-beta superfamily-including BMPs and their antagonists-in the formation of bone metastasis. Increasing evidence suggests that the TGF-beta superfamily is involved in bone homing, tumour dormancy, and development of micrometastases into overt bone metastases. The established role of TGF-beta/BMPs and their antagonists in epithelial plasticity during embryonic development closely resembles neoplastic processes at the primary site as well as in (bone) metastasis. For instance, the tumour-stroma interactions occurring in the tissue of cancer origin, including epithelium-to-mesenchyme transition (EMT), bear similarities with the role of bone matrix-derived TGF-beta in skeletal metastasis formation.

Identification and prognostic significance of an epithelial-mesenchymal transition expression profile in human bladder tumors

PURPOSE

Epithelial to mesenchymal transition (EMT) is reportedly an important transition in cancer progression in which the underlying cellular changes have been identified mainly using in vitro models. In this study, we examined the expression pattern of EMT markers in vivo and determined the occurrence and clinical significance of these events in a series of bladder carcinomas.

EXPERIMENTAL DESIGN

Eight hundred and twenty-five tumor samples from 572 bladder cancer patients were assembled in 10 tissue microarrays. Paraffin sections from each tissue microarray were subjected to antigen retrieval and processed by immunohistochemistry for the expression of E-cadherin, plakoglobin, beta-catenin, N-cadherin, and vimentin.

RESULTS

Pathologic expression of E-cadherin, beta-catenin, plakoglobin, and vimentin were associated with the clinicopathologic variables of grade and stage with only the cytoplasmic localization of plakoglobin found associated with lymph node status. Associations between the aforementioned markers were found significant as determined by the Spearman correlation coefficient with N-cadherin showing no associations in this analysis. In univariate survival analysis involving patients who underwent cystectomy, the reduction or loss of plakoglobin significantly influenced overall survival (P = 0.02) in which the median time to death was 2 years compared with 4 years when a normal level of plakoglobin was recorded. When the analysis was done for cancer-specific survival, low levels of both plakoglobin (P = 0.02) and beta-catenin (P = 0.02) significantly influenced survival.

CONCLUSION

The putative markers of EMT defined within a panel of bladder carcinoma cell lines were recorded in vivo, frequently associated with tumors of high grade and stage. Although multivariate analysis showed no significant influence of the EMT biomarkers on survival, alterations associated with plakoglobin were identified as significant prognostic features in these tumors.

Mesenchyme Forkhead 1 (FOXC2) plays a key role in metastasis and is associated with aggressive basal-like breast cancers

The metastatic spread of epithelial cancer cells from the primary tumor to distant organs mimics the cell migrations that occur during embryogenesis. Using gene expression profiling, we have found that the FOXC2 transcription factor, which is involved in specifying mesenchymal cell fate during embryogenesis, is associated with the metastatic capabilities of cancer cells. FOXC2 expression is required for the ability of murine mammary carcinoma cells to metastasize to the lung, and overexpression of FOXC2 enhances the metastatic ability of mouse mammary carcinoma cells. We show that FOXC2 expression is induced in cells undergoing epithelial-mesenchymal transitions (EMTs) triggered by a number of signals, including TGF-beta1 and several EMT-inducing transcription factors, such as Snail, Twist, and Goosecoid. FOXC2 specifically promotes mesenchymal differentiation during an EMT and may serve as a key mediator to orchestrate the mesenchymal component of the EMT program. Expression of FOXC2 is significantly correlated with the highly aggressive basal-like subtype of human breast cancers. These observations indicate that FOXC2 plays a central role in promoting invasion and metastasis and that it may prove to be a highly specific molecular marker for human basal-like breast cancers.

Snail and slug play distinct roles during breast carcinoma progression

PURPOSE

Carcinoma progression is linked to a partially dedifferentiated epithelial cell phenotype. As previously suggested, this regulation could involve transcription factors, Snail and Slug, known to promote epithelial-mesenchymal transitions during development. Here, we investigate the role of Snail and Slug in human breast cancer progression.

EXPERIMENTAL DESIGN

We analyzed Snail, Slug, and E-cadherin RNA expression levels and protein localization in large numbers of transformed cell lines and breast carcinomas, examined the correlation with tumor histologic features, and described, at the cellular level, Snail and Slug localization in carcinomas using combined in situ hybridization and immunolocalization.

RESULTS

In contrast with transformed cell lines, Slug was found to colocalize with E-cadherin at the cellular level in normal mammary epithelial cells and all tested carcinomas. Snail also colocalized at the cellular level with E-cadherin in tumors expressing high levels of Snail RNA. In addition, Snail was significantly expressed in tumor stroma, varying with tumors. Slug and Snail genes were significantly overexpressed in tumors associated with lymph node metastasis. Finally, the presence of semidifferentiated tubules within ductal carcinomas was linked to Slug expression levels similar to or above normal breast samples.

CONCLUSIONS

These results suggest that Snail or Slug expression in carcinoma cells does not generally preclude significant E-cadherin expression. They emphasize a link between Snail, Slug, and lymph node metastasis in a large sampling of mammary carcinomas, and suggest a role for Slug in the maintenance of semidifferentiated structures. Snail and Slug proteins seem to support distinct tumor invasion modes and could provide new therapeutic targets.

ESX induces transformation and functional epithelial to mesenchymal transition in MCF-12A mammary epithelial cells

ESX is an epithelial-restricted member of a large family of transcription factors known as the Ets family. ESX expression has been shown to be correlated with Her2/neu proto-oncogene amplification in highly aggressive breast cancers and induced by Her2/neu in breast cell lines, but its role in tumorigenesis is unknown. Previously, we have shown that ESX enhances breast cell survival in colony-formation assays. In order to determine whether ESX can act as a transforming gene, we stably transfected MCF-12A human mammary epithelial cells with the ESX expression vector, pCGN2-HA-ESX. The MCF-12A cell line is immortalized, but nontransformed, and importantly, these cells fail to express endogenous ESX protein. We used pCGN2-HA-Ets-2 and pSVRas expression vectors as positive controls for transformation. Like HA-Ets-2 and V12-Ras, stable expression of ESX induced EGF-independent proliferation, serum-independent MAPK phosphorylation and growth in soft agar. Additionally, stable ESX expression conferred increased cell adhesion, motility and invasion in two-dimensional and transwell filter assays, and an epithelial to mesenchymal morphological transition. In three-dimensional cultures, parental and vector control (pCGN2) cells formed highly organized duct-like structures with evidence of cell polarity, ECM adhesion-dependent proliferation and cell survival, and lack of cellular invasion into surrounding matrix. Remarkably, the ESX stable cells formed solid, disorganized structures, with lack of cell polarity, loss of adhesion junctions and cytokeratin staining and loss of dependence on ECM adhesion for cell proliferation and survival. In addition, ESX cells invaded the surrounding matrix, indicative of a transformed and metastatic phenotype. Taken together, these data show that ESX expression alone confers a transformed and in vitro metastatic phenotype to otherwise normal MCF-12A cells.

Molecular aspects of epithelial cell plasticity: implications for local tumor invasion and metastasis

Carcinomas arising from epithelial cells represent the most prevalent malignancies in humans, and metastasis is the major cause for the death of carcinoma patients. The breakdown of epithelial cell homeostasis leading to aggressive cancer progression has been correlated with the loss of epithelial characteristics and the acquisition of a migratory phenotype. This phenomenon, referred to as epithelial to mesenchymal transition (EMT), is considered as a crucial event in late stage tumorigenesis. Here we summarize the multitude of EMT models derived from different tissues, and review the diversity of molecular mechanisms contributing to the plasticity of epithelial cells. In particular, the synergism between activation of Ras, provided by the aberrant stimulation of receptor tyrosine kinases, and transforming growth factor (TGF)-beta signaling plays a pivotal role in inducing EMT of various epithelial cell types. Cytokines such as TGF-beta and extracellular matrix molecules are thought to fundamentally contribute to the microenvironmental interaction between stromal and malignant cells, and provide the basis for a broad repertoire of epithelial differentiation. Investigations of EMT tumor models, which represent in vitro correlates to local invasion and metastasis in vivo, facilitate the identification of diagnostic markers for a more accurate and faithful clinical and pathological assessment of epithelial tumors. In addition, the analysis of molecular mechanisms involved in EMT might yield novel therapeutic targets for the specific treatment of aggressive carcinomas.

Epidermal growth factor-induced epithelio-mesenchymal transition in human breast carcinoma cells

PMC42-LA cells display an epithelial phenotype: the cells congregate into pavement epithelial sheets in which E-cadherin and beta-catenin are localized at cell-cell borders. They abundantly express cytokeratins, although 5% to 10% of the cells also express the mesenchymal marker vimentin. Stimulation of PMC42-LA cells with epidermal growth factor (EGF) leads to epithelio-mesenchymal transition-like changes including up-regulation of vimentin and down-regulation of E-cadherin. Vimentin expression is seen in virtually all cells, and this increase is abrogated by treatment of cells with an EGF receptor antagonist. The expression of the mesenchyme-associated extracellular matrix molecules fibronectin and chondroitin sulfate proteoglycan also increase in the presence of EGF. PMC42-LA cells adhere rapidly to collagen I, collagen IV, and laminin-1 substrates and markedly more slowly to fibronectin and vitronectin. EGF increases the speed of cell adhesion to most of these extracellular matrix molecules without altering the order of adhesive preference. EGF also caused a time-dependent increase in the motility of PMC42-LA cells, commensurate with the degree of vimentin staining. The increase in motility was at least partly chemokinetic, because it was evident both with and without chemoattractive stimuli. Although E-cadherin staining at cell-cell junctions disappeared in response to EGF, beta-catenin persisted at the cell periphery. Further analysis revealed that N-cadherin was present at the cell-cell junctions of untreated cells and that expression was increased after EGF treatment. N- and E-cadherin are not usually coexpressed in human carcinoma cell lines but can be coexpressed in embryonic tissues, and this may signify an epithelial cell population prone to epithelio-mesenchymal-like responses.

Cell migration and proliferation are not discriminatory factors in the in vitro sociologic behavior of bronchial epithelial cell lines

A model of cellular cohesion has been developed, which permits the in vitro study of the spatial and temporal distribution of two human bronchial cell lines. The spatial distribution of cells in culture was characterized from videomicroscopic recordings and analyzed using an algorithmic program of cellular sociology based on the use of three geometrical models: Voronoï's partition, Delaunay's graph, the and minimum spanning tree (MST). The results obtained suggested that the manner of cellular cohesiveness could be used to differentiate between the organizational behaviors of the cell lines: non-invasive 16HBE14o- cells rapidly formed clusters with a cohesive organization, whereas invasive BZR cells remained isolated and were characterized by a non-cohesive organization. Videomicroscopic and image analysis techniques also demonstrated that cell migration and proliferation are not discriminatory factors for explaining differences in the spatial organizations of the two cell lines. We concluded that the random nature of cell movement combined with the cell adhesion capacity are determinant factors in cell cluster formation.

Leaving the neighborhood: molecular mechanisms involved during epithelial-mesenchymal transition

Several molecular mechanisms contribute directly and mechanically to the loss of epithelial phenotype. During epithelial-mesenchymal transition (EMT), adherens junctions and desmosomes are at least partially dissociated. At the same time, a massive cytoskeleton reorganization takes place, involving the rho family and the remodeling of the actin microfilament mesh. Numerous pathways have been described in vitro that control phenotype transition in specific cell models. In vivo developmental studies suggest that transcriptional control, activated by a specific pathway involving Ras, Src and potentially the Wnt pathway, is an essential step. Recent functional and localization experiments indicate that the slug/snail family of transcription factors functions overall as an epithelial phenotype repressor and could represent a key EMT contributor.

LCC15-MB: a vimentin-positive human breast cancer cell line from a femoral bone metastasis

The LCC15-MB cell line was established from a femoral bone metastasis that arose in a 29-year-old woman initially diagnosed with an infiltrating ductal mammary adenocarcinoma. The tumor had a relatively high (8%) S-phase fraction and 1/23 positive lymph nodes (LN). Both the primary tumor and LN metastasis were positive for estrogen receptor (ER) and progesterone receptor (PgR), but lacked erbB2 expression. Approximately one year later, the patient presented with a 0.8 cm comedo-type intraductal mammary adenocarcinoma in the left breast that was negative for ER and PgR, but positive for erbB2. Thirty-five months after the initial diagnosis she was treated for acute skeletal metastasis, and stabilized with a hip replacement. At this time, tumor cells were removed from surplus involved bone, inoculated into cell culture, and developed into the LCC 15-MB cell line. The bone metastasis was a poorly differentiated adenocarcinoma lacking ER, PgR, and erbB2, characteristics shared by the LCC15-MB cells, although ER can be re-expressed by treatment of the LCC15-MB cells for 5 days with 75 microM 5-aza-2'-deoxycytidine. The LCC15-MB cell line is tumorigenic when implanted subcutaneously in NCr nu/nu mice and produces long-bone metastases after intracardiac injection. Although the bone metastasis from which the LCC15-MB cell line was derived lacked vimentin (VIM) expression, the original primary tumor and lymph node metastasis were strongly VIM positive, as are LCC15-MB cells in vitro and in nude mice. The karyotype and isozyme profiles of LCC15-MB cells are consistent with its origin from a human female, with most chromosome counts in the hypertriploid range. Thirty-two marker chromosomes are present. These cells provide an in vitro/in vivo model in which to study the inter-relationships between ER, VIM, and bone metastasis in human breast cancer.

Fra-1 induces morphological transformation and increases in vitro invasiveness and motility of epithelioid adenocarcinoma cells

Two cell lines originating from a common ancestral tumor, CSML0 and CSML100, were used as a model to study AP-1 transcription factors at different steps of tumor progression. CSML0 cells have an epithelial morphology; they express epithelial but not mesenchymal markers and are invasive neither in vitro nor in vivo. CSML100 possesses all characteristics of a highly progressive carcinoma. These cells do not form tight contacts, are highly invasive in vitro, and are metastatic in vivo. AP-1 activity was considerably higher in CSML100 cells than in CSML0 cells. There was a common predominant Jun component, namely, JunD, detected in both cell lines. We found that the enhanced level of AP-1 in CSML100 cells was due to high expression of Fra-1 and Fra-2 proteins, which were undetectable in CSML0 nuclear extracts. Analysis of the transcription of different AP-1 members in various cell lines derived from tumors of epithelial origin revealed a correlation of fra-1 expression with mesenchymal characteristics of carcinoma cells. Moreover, we show here for the first time that the expression of exogenous Fra-1 in epithelioid cells results in morphological changes that resemble fibroblastoid conversion. Cells acquire an elongated shape and become more motile and invasive in vitro. Morphological alterations were accompanied by transcriptional activation of certain genes whose expression is often induced at late stages of tumor progression. These data suggest a critical role of the Fra-1 protein in the development of epithelial tumors.

Morphogenetic effects of neuregulin (neu differentiation factor) in cultured epithelial cells

Neuregulin, or neu differentiation factor, induces cell proliferation or differentiation through interaction with members of the ErbB family of receptor tyrosine kinases. We report that neuregulin can also induce profound morphogenic responses in cultured epithelial cells of different origins. These effects include scattering of small epithelial islands and rearrangement of larger cell islands into ordered ring-shaped arrays with internal lumens. The ring-forming cells are interconnected by cadherin- and beta-catenin-containing adherens junctions. In confluent cultures, neuregulin treatment induces formation of circular lumenlike gaps in the monolayer. Both cell scattering and ring formation are accompanied by a marked increase in cell motility that is independent of hepatocyte growth factor/scatter factor and its receptor (c-Met). Affinity-labeling experiments implied that a combination of ErbB-2 with ErbB-3 mediates the morphogenic signal of neuregulin in gastric cells. Indeed, a similar morphogenic effect could be reconstituted in nonresponsive cells by coexpression of ErbB-2 and -3. We conclude that a heterodimer between the kinase-defective neuregulin receptor, ErbB-3, and the coreceptor, ErbB-2, mediates the morphogenetic action of neuregulin.

Autotaxin, tumor motility-stimulating exophosphodiesterase

While nucleotides have a well-established role in intracellular metabolism, ATP and other nucleotides also have important extracellular roles in receptor-mediated signal transduction (34, 35). Extracellular or cell surface proteins capable of binding ATP and hydrolyzing phosphoester bonds of nucleotides are known to exist but their function has remained obscure. Our recent data point to a structure-function correlation between PDE activity and motility stimulation by ATX, indicating a biologically important functional role for the ecto/exophosdiesterases in the stimulation of cellular motility. Data from studies with PC-1 and gp130RB13-6 have suggested that cell surface PDE's may also play roles in cellular differentiation. Extracellular PDE activities, in combination with other nucleotidases, may result in ecto-nucleotidase cascades (36-38). These data suggest that ecto-/exo-enzymes may catalyze extracellular biochemical reactions that are important in the regulation of cell behavior.

The zinc-finger protein slug causes desmosome dissociation, an initial and necessary step for growth factor-induced epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is an essential morphogenetic process during embryonic development. It can be induced in vitro by hepatocyte growth factor/scatter factor (HGF/SF), or by FGF-1 in our NBT-II cell model for EMT. We tested for a central role in EMT of a zinc-finger protein called Slug. Slug mRNA and protein levels were increased transiently in FGF-1-treated NBT-II cells. Transient or stable transfection of Slug cDNA in NBT-II cells resulted in a striking disappearance of the desmosomal markers desmoplakin and desmoglein from cell-cell contact areas, mimicking the initial steps of FGF-1 or HGF/SF- induced EMT. Stable transfectant cells expressed Slug protein and were less epithelial, with increased cell spreading and cell-cell separation in subconfluent cultures. Interestingly, NBT-II cells transfected with antisense Slug cDNA were able to resist EMT induction by FGF-1 or even HGF/SF. This antisense effect was suppressed by retransfection with Slug sense cDNA. Our results indicate that Slug induces the first phase of growth factor-induced EMT, including desmosome dissociation, cell spreading, and initiation of cell separation. Moreover, the antisense inhibition experiments suggest that Slug is also necessary for EMT.