E-cadherin gene mutations in human gastric carcinoma cell lines

Molecular pathological approach to cancer epigenomics and its clinical application

Careful microscopic observation of histopathological specimens, accumulation of large numbers of high-quality tissue specimens, and analysis of molecular pathology in relation to morphological features are considered to yield realistic data on the nature of multistage carcinogenesis. Since the morphological hallmark of cancer is disruption of the normal histological structure maintained through cell-cell adhesiveness and cellular polarity, attempts have been made to investigate abnormalities of the cadherin-catenin cell adhesion system in human cancer cells. It has been shown that the CDH1 tumor suppressor gene encoding E-cadherin is silenced by DNA methylation, suggesting that a "double hit" involving DNA methylation and loss of heterozygosity leads to carcinogenesis. Therefore, in the 1990s, we focused on epigenomic mechanisms, which until then had not received much attention. In chronic hepatitis and liver cirrhosis associated with hepatitis virus infection, DNA methylation abnormalities were found to occur frequently, being one of the earliest indications that such abnormalities are present even in precancerous tissue. Aberrant expression and splicing of DNA methyltransferases, such as DNMT1 and DNMT3B, was found to underlie the mechanism of DNA methylation alterations in various organs. The CpG island methylator phenotype in renal cell carcinoma was identified for the first time, and its therapeutic targets were identified by multilayer omics analysis. Furthermore, the DNA methylation profile of nonalcoholic steatohepatitis (NASH)-related hepatocellular carcinoma was clarified in groundbreaking studies. Since then, we have developed diagnostic markers for carcinogenesis risk in NASH patients and noninvasive diagnostic markers for upper urinary tract cancer, as well as developing a new high-performance liquid chromatography-based diagnostic system for DNA methylation diagnosis. Research on the cancer epigenome has revealed that DNA methylation alterations occur from the precancerous stage as a result of exposure to carcinogenic factors such as inflammation, smoking, and viral infections, and continuously contribute to multistage carcinogenesis through aberrant expression of cancer-related genes and genomic instability. DNA methylation alterations at the precancerous stages are inherited by or strengthened in cancers themselves and determine the clinicopathological aggressiveness of cancers as well as patient outcome. DNA methylation alterations have applications as biomarkers, and are expected to contribute to diagnosis, as well as preventive and preemptive medicine.

Activation of Laminin γ2 by Helicobacter pylori Promotes Invasion and Survival of Gastric Cancer Cells With E-Cadherin Defects

BACKGROUND

Helicobacter pylori infection induces cellular phenotypes relevant for cancer progression, namely cell motility and invasion. We hypothesized that the extracellular matrix (ECM) could be involved in these deleterious effects.

METHODS

Microarrays were used to uncover ECM interactors in cells infected with H. pylori. LAMC2, encoding laminin γ2, was selected as a candidate gene and its expression was assessed in vitro and in vivo. The role of LAMC2 was investigated by small interference RNA (siRNA) combined with a set of functional assays. Laminin γ2 and E-cadherin expression patterns were evaluated in gastric cancer cases.

RESULTS

Laminin γ2 was found significantly overexpressed in gastric cancer cells infected with H. pylori. This finding was validated in vitro by infection with clinical isolates and in vivo by using gastric biopsies of infected and noninfected individuals. We showed that laminin γ2 overexpression is dependent on the bacterial type IV secretion system and on the CagA. Functionally, laminin γ2 promotes cell invasion and resistance to apoptosis, through modulation of Src, JNK, and AKT activity. These effects were abrogated in cells with functional E-cadherin.

CONCLUSIONS

These data highlight laminin γ2 and its downstream effectors as potential therapeutic targets, and the value of H. pylori eradication to delay gastric cancer onset and progression.

Potential therapeutic targets discovery by transcriptome analysis of an in vitro human gastric signet ring carcinoma model

BACKGROUND

Loss of E-cadherin expression is frequently observed in signet ring carcinoma (SRCC). People with germline mutations in CDH1, which encodes E-cadherin, develop diffuse gastric cancer at a higher rate. Loss of E-cadherin expression is thus assumed to trigger oncogenic development.

METHODS

To investigate novel therapeutic targets for gastric SRCC, we engineered an E-cadherin-deficient SRCC model in vitro using a human gastric organoid (hGO) with CDH1 knockout (KO).

RESULTS

CDH1 KO hGO cells demonstrated distinctive morphological changes similar to SRCC and high cell motility. RNA-sequencing revealed up-regulation of matrix metalloproteinase (MMP) genes in CDH1 KO hGO cells compared to wild type. MMP inhibitors suppressed cell motility of CDH1 KO hGO cells and SRCC cell lines in vitro. Immunofluorescent analysis with 95 clinical gastric cancer tissues revealed that MMP-3 was specifically abundant in E-cadherin-aberrant SRCC. In addition, CXCR4 molecules translocated onto the cell membrane after CDH1 KO. Addition of CXCL12, a ligand of CXCR4, to the culture medium prolonged cell survival of CDH1 KO hGO cells and was abolished by the inhibitor, AMD3100. In clinical SRCC samples, CXCL12-secreting fibroblasts showed marked infiltration into the cancer area.

CONCLUSIONS

E-cadherin deficient SRCCs might gain cell motility through upregulation of MMPs. CXCL12-positive cancer-associated fibroblasts could serve to maintain cancer-cell survival as a niche. MMPs and the CXCL12/CXCR4 axis represent promising candidates as novel therapeutic targets for E-cadherin-deficient SRCC.

Constitutive Occurrence of E:N-cadherin Heterodimers in Adherens Junctions of Hepatocytes and Derived Tumors

Cell–cell junctions are pivotal for embryogenesis and tissue homeostasis but also play a major role in tumorigenesis, tumor invasion, and metastasis. E-cadherin (CDH1) and N-cadherin (CDH2) are two adherens junction’s transmembrane glycoproteins with tissue-specific expression patterns in epithelial and neural/mesenchymal cells. Aberrant expression has been implicated in the process of epithelial–mesenchymal transition (EMT) in malignant tumors. We could hitherto demonstrate cis-E:N-cadherin heterodimer in endoderm-derived cells. Using immunoprecipitation in cultured cells of the line PLC as well as in human hepatocellular carcinoma (HCC)-lysates, we isolated E-N-cadherin heterodimers in a complex with the plaque proteins α- and β-catenin, plakoglobin, and vinculin. In confocal laser scanning microscopy, E-cadherin co-localized with N-cadherin at the basolateral membrane of normal hepatocytes, hepatocellular adenoma (HCA), and in most cases of HCC. In addition, we analyzed E- and N-cadherin expression via immunohistochemistry in a large cohort of 868 HCCs from 570 patients, 25 HCA, and respective non-neoplastic liver tissue, and correlated our results with multiple prognostic markers. While E- or N-cadherin were similarly expressed in tumor sites with vascular invasion or HCC metastases, HCC with vascular encapsulated tumor clusters (VETC) displayed slightly reduced E-cadherin, and slightly increased N-cadherin expression. Analyzing The Cancer Genome Atlas patient cohort, we found that reduced mRNA levels of CDH1, but not CDH2 were significantly associated with unfavorable prognosis; however, in multivariate analysis, CDH1 did not correlate with prognosis. In summary, E- and N-cadherin are specific markers for hepatocytes and derived HCA and HCC. E:N-cadherin heterodimers are constitutively expressed in the hepatocytic lineage and only slightly altered in malignant progression, thereby not complying with the concept of EMT.

N-Cadherin Distinguishes Intrahepatic Cholangiocarcinoma from Liver Metastases of Ductal Adenocarcinoma of the Pancreas

Carcinomas of the pancreatobiliary system confer an especially unfavorable prognosis. The differential diagnosis of intrahepatic cholangiocarcinoma (iCCA) and its subtypes versus liver metastasis of ductal adenocarcinoma of the pancreas (PDAC) is clinically important to allow the best possible therapy. We could previously show that E-cadherin and N-cadherin, transmembrane glycoproteins of adherens junctions, are characteristic features of hepatocytes and cholangiocytes. We therefore analyzed E-cadherin and N-cadherin in the embryonally related epithelia of the bile duct and pancreas, as well as in 312 iCCAs, 513 carcinomas of the extrahepatic bile ducts, 228 gallbladder carcinomas, 131 PDACs, and precursor lesions, with immunohistochemistry combined with image analysis, fluorescence microscopy, and immunoblots. In the physiological liver, N-cadherin colocalizes with E-cadherin in small intrahepatic bile ducts, whereas larger bile ducts and pancreatic ducts are positive for E-cadherin but contain decreasing amounts of N-cadherin. N-cadherin was highly expressed in most iCCAs, whereas in PDACs, N-cadherin was negative or only faintly expressed. E- and N-cadherin expression in tumors of the pancreaticobiliary tract recapitulate their expression in their normal tissue counterparts. N-cadherin is a helpful marker for the differential diagnosis between iCCA and PDAC, with a specificity of 96% and a sensitivity of 67% for small duct iCCAs and 50% for large duct iCCAs.

Genetic and Epigenetic Alterations of CDH1 Regulatory Regions in Hereditary and Sporadic Gastric Cancer

E-cadherin is a key player in gastric cancer (GC) and germline alterations of CDH1, its encoding gene, are responsible for Hereditary Diffuse Gastric Cancer (HDGC) syndrome. This study aimed at elucidating the role of genetic variants and DNA methylation of CDH1 promoter and enhancers in the regulation of gene expression. For this purpose, we analyzed genetic variants of the CDH1 gene through Next-Generation Sequencing (NGS) in a series of GC cell lines (NCI-N87, KATO-III, SNU-1, SNU-5, GK2, AKG, KKP) and the corresponding CDH1 expression levels. By bisulfite genomic sequencing, we analyzed the methylation status of CDH1 regulatory regions in 8 GC cell lines, in a series of 13 sporadic GC tissues and in a group of 20 HDGC CDH1-negative patients and 6 healthy controls. The NGS analysis on CDH1 coding and regulatory regions detected genetic alterations in 3 out of 5 GC cell lines lacking functional E-cadherin. CDH1 regulatory regions showed different methylation patterns in patients and controls, GC cell lines and GC tissues, expressing different E-cadherin levels. Our results showed that alterations in terms of genetic variants and DNA methylation patterns of both promoter and enhancers are associated with CDH1 expression levels and have a role in its regulation.

KSR1- and ERK-dependent translational regulation of the epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) is considered a transcriptional process that induces a switch in cells from a polarized state to a migratory phenotype. Here, we show that KSR1 and ERK promote EMT-like phenotype through the preferential translation of Epithelial-Stromal Interaction 1 (EPSTI1), which is required to induce the switch from E- to N-cadherin and coordinate migratory and invasive behavior. EPSTI1 is overexpressed in human colorectal cancer (CRC) cells. Disruption of KSR1 or EPSTI1 significantly impairs cell migration and invasion in vitro, and reverses EMT-like phenotype, in part, by decreasing the expression of N-cadherin and the transcriptional repressors of E-cadherin expression, ZEB1 and Slug. In CRC cells lacking KSR1, ectopic EPSTI1 expression restored the E- to N-cadherin switch, migration, invasion, and anchorage-independent growth. KSR1-dependent induction of EMT-like phenotype via selective translation of mRNAs reveals its underappreciated role in remodeling the translational landscape of CRC cells to promote their migratory and invasive behavior.

Brain-invasive meningiomas: molecular mechanisms and potential therapeutic options

Meningiomas are the most commonly diagnosed benign intracranial adult tumors. Subsets of meningiomas that present with extensive invasion into surrounding brain areas have high recurrence rates, resulting in difficulties for complete resection, substantially increased mortality of patients, and are therapeutically challenging for neurosurgeons. Exciting new data have provided insights into the understanding of the molecular machinery of invasion. Moreover, clinical trials for several novel approaches have been launched. Here, we will highlight the mechanisms which govern brain invasion and new promising therapeutic approaches for brain-invasive meningiomas, including pharmacological approaches targeting three major aspects of tumor cell invasion: extracellular matrix degradation, cell adhesion, and growth factors, as well as other innovative treatments such as immunotherapy, hormone therapy, Tumor Treating Fields, and biodegradable copolymers (wafers), impregnated chemotherapy. Those ongoing studies can offer more diversified possibilities of potential treatments for brain-invasive meningiomas, and help to increase the survival benefits for patients.

TAZ Controls Helicobacter pylori-Induced Epithelial-Mesenchymal Transition and Cancer Stem Cell-Like Invasive and Tumorigenic Properties

Helicobacter pylori infection, the main risk factor for gastric cancer (GC), leads to an epithelial–mesenchymal transition (EMT) of gastric epithelium contributing to gastric cancer stem cell (CSC) emergence. The Hippo pathway effectors yes-associated protein (YAP) and transcriptional co-activator with PDZ binding motif (TAZ) control cancer initiation and progression in many cancers including GC. Here, we investigated the role of TAZ in the early steps of H. pylori-mediated gastric carcinogenesis. TAZ implication in EMT, invasion, and CSC-related tumorigenic properties were evaluated in three gastric epithelial cell lines infected by H. pylori. We showed that H. pylori infection increased TAZ nuclear expression and transcriptional enhancer TEA domain (TEAD) transcription factors transcriptional activity. Nuclear TAZ and zinc finger E-box-binding homeobox 1 (ZEB1) were co-overexpressed in cells harboring a mesenchymal phenotype in vitro, and in areas of regenerative hyperplasia in gastric mucosa of H. pylori-infected patients and experimentally infected mice, as well as at the invasive front of gastric carcinoma. TAZ silencing reduced ZEB1 expression and EMT phenotype, and strongly inhibited invasion and tumorsphere formation induced by H. pylori. In conclusion, TAZ activation in response to H. pylori infection contributes to H. pylori-induced EMT, invasion, and CSC-like tumorigenic properties. TAZ overexpression in H. pylori-induced pre-neoplastic lesions and in GC could therefore constitute a biomarker of early transformation in gastric carcinogenesis.

CHAC1 overexpression in human gastric parietal cells with Helicobacter pylori infection in the secretory canaliculi

BACKGROUND

Cation transport regulator 1 (CHAC1), a newly discovered enzyme that degrades glutathione, is induced in Helicobacter pylori (H. pylori)-infected gastric epithelial cells in culture. The CHAC1-induced decrease in glutathione leads to an accumulation of reactive oxygen species and somatic mutations in TP53. We evaluated the possible correlation between H. pylori infection and CHAC1 expression in human gastric mucosa.

MATERIALS AND METHODS

Both fresh-frozen and formalin-fixed paraffin-embedded tissue samples of gastric mucosa with or without H. pylori infection were obtained from 41 esophageal cancer patients that underwent esophago-gastrectomy. Fresh samples were used for real-time polymerase chain reaction for H. pylori DNA and CHAC1 mRNA, and formalin-fixed samples were used for immunohistochemistry with anti-CHAC1 and anti-H. pylori monoclonal antibodies. Double-enzyme or fluorescence immunohistochemistry and immuno-electron microscopy were used for further analysis.

RESULTS

Significant CHAC1 overexpression was detected in H. pylori-infected parietal cells that expressed the human proton pump/H,K-ATPase α subunit, whereas a constitutively low level of CHAC1 mRNA expression was observed in the other samples regardless of the H. pylori infection status, reflecting the weak CHAC1 expression detected by immunohistochemistry in the fundic-gland areas. Immuno-electron microscopy revealed intact H. pylori cells in the secretory canaliculi of infected parietal cells. Some parietal cells exhibited positive nuclear signals for Ki67 in the neck zone of the gastric fundic-gland mucosa with H. pylori infection.

CONCLUSION

Cation transport regulator 1 overexpression in H. pylori-infected parietal cells may cause the H. pylori-induced somatic mutations that contribute to the development of gastric cancer.

The significance of scirrhous gastric cancer cell lines: the molecular characterization using cell lines and mouse models

Scirrhous gastric cancer (SGC) exhibits aggressiveness of the rapid infiltrating tumor cells with abundant fibroblasts. Experimental studies using SGC cell lines have obtained useful information about this cancer. Our literature search divulged a total of 18 SGC cell lines; two cell lines were established from primary SGC and the other lines were established from a metastatic lesion of SGC. Fibroblast growth factor receptor 2 (FGFR2) and transforming growth factor-beta receptor (TβR) are linked to the rapid development of SGC. Cross-talk between the cancer cells and cancer-associated fibroblasts (CAFs) has been shown to contribute to the progression of SGC. Chemokine (C-X-C motif) receptor 1 (CXCR1) from SGC cells might be associated with the abundant CAFs in cancer microenvironments. The in vivo models established using SGC cell lines are expected to serve as a useful tool for the development of drugs such as FGFR2 inhibitors, TβR inhibitors, and CXCR1 inhibitors, which might be promising as SGC treatments. However, the number of available SGC cell lines is insufficient for the clarification of the entire biologic behavior of SGC. Since the mechanisms responsible for the characteristic aggressiveness of SGC are not fully elucidated, the establishment of new SGC cell lines could help clarify the biological behavior of SGC and contribute to its treatment.

O-mannosylation and N-glycosylation: two coordinated mechanisms regulating the tumour suppressor functions of E-cadherin in cancer

Dysregulation of tumor suppressor protein E-cadherin is an early molecular event in cancer. O-mannosylation profile of E-cadherin is a newly-described post-translational modification crucial for its adhesive functions in homeostasis. However, the role of O-mannosyl glycans in E-cadherin-mediated cell adhesion in cancer and their interplay with N-glycans remains largely unknown. We herein demonstrated that human gastric carcinomas exhibiting a non-functional E-cadherin display a reduced expression of O-mannosyl glycans concomitantly with increased modification with branched complex N-glycans. Accordingly, overexpression of MGAT5-mediated branched N-glycans both in gastric cancer cells and transgenic mice models led to a significant decrease of O-mannosyl glycans attached to E-cadherin that was associated with impairment of its tumour suppressive functions. Importantly, overexpression of protein O-mannosyltransferase 2 (POMT2) induced a reduced expression of branched N-glycans which led to a protective effect of E-cadherin biological functions. Overall, our results reveal a newly identified mechanism of (dys)regulation of E-cadherin that occur through the interplay between O-mannosylation and N-glycosylation pathway.

A deep boosting based approach for capturing the sequence binding preferences of RNA-binding proteins from high-throughput CLIP-seq data

Characterizing the binding behaviors of RNA-binding proteins (RBPs) is important for understanding their functional roles in gene expression regulation. However, current high-throughput experimental methods for identifying RBP targets, such as CLIP-seq and RNAcompete, usually suffer from the false negative issue. Here, we develop a deep boosting based machine learning approach, called DeBooster, to accurately model the binding sequence preferences and identify the corresponding binding targets of RBPs from CLIP-seq data. Comprehensive validation tests have shown that DeBooster can outperform other state-of-the-art approaches in RBP target prediction. In addition, we have demonstrated that DeBooster may provide new insights into understanding the regulatory functions of RBPs, including the binding effects of the RNA helicase MOV10 on mRNA degradation, the potentially different ADAR1 binding behaviors related to its editing activity, as well as the antagonizing effect of RBP binding on miRNA repression. Moreover, DeBooster may provide an effective index to investigate the effect of pathogenic mutations in RBP binding sites, especially those related to splicing events. We expect that DeBooster will be widely applied to analyze large-scale CLIP-seq experimental data and can provide a practically useful tool for novel biological discoveries in understanding the regulatory mechanisms of RBPs. The source code of DeBooster can be downloaded from http://github.com/dongfanghong/deepboost.

Decreased expression of granulocyte-macrophage colony-stimulating factor is associated with adverse clinical outcome in patients with gastric cancer undergoing gastrectomy

Previous studies have revealed the clinical significance of tumor-associated macrophages (TAMs) in gastric cancer, whereas the role of the cytokines that orchestrate TAM polarization in gastric cancer remains elusive. The present study aimed to evaluate the prognostic value of granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in patients with gastric cancer. Intratumoral GM-CSF expression was investigated by immunohistochemical staining in 408 retrospectively enrolled patients. Kaplan-Meier analysis and Cox regression models were used to evaluate the prognostic value of GM-CSF expression. Predictive nomograms were generated to predict the overall survival and disease-free survival rates of the patients. Decreased intratumoral GM-CSF expression was identified, and indicated a poorer clinical outcome for patients with gastric cancer, particularly in advanced stages. Intratumoral GM-CSF expression may provide an additional risk stratification for the prognosis of patients with gastric cancer based on the Tumor-Node-Metastasis (TNM) staging system. Cox multivariate analysis identified GM-CSF expression as an independent prognostic factor for overall survival and disease-free survival time. The generated nomograms performed well in predicting the 3-and 5-year clinical outcome of patients with gastric cancer. In conclusion, GM-CSF is a potential independent prognostic indicator for patients with gastric cancer, which may be integrated with TNM staging systems to improve the predictive accuracy for clinical outcome, particularly in advanced tumors.

p120-catenin prevents multinucleation through control of MKLP1-dependent RhoA activity during cytokinesis

Spatiotemporal activation of RhoA and actomyosin contraction underpins cellular adhesion and division. Loss of cell-cell adhesion and chromosomal instability are cardinal events that drive tumour progression. Here, we show that p120-catenin (p120) not only controls cell-cell adhesion, but also acts as a critical regulator of cytokinesis. We find that p120 regulates actomyosin contractility through concomitant binding to RhoA and the centralspindlin component MKLP1, independent of cadherin association. In anaphase, p120 is enriched at the cleavage furrow where it binds MKLP1 to spatially control RhoA GTPase cycling. Binding of p120 to MKLP1 during cytokinesis depends on the N-terminal coiled-coil domain of p120 isoform 1A. Importantly, clinical data show that loss of p120 expression is a common event in breast cancer that strongly correlates with multinucleation and adverse patient survival. In summary, our study identifies p120 loss as a driver event of chromosomal instability in cancer.

Decitabine inhibits tumor cell proliferation and up-regulates e-cadherin expression in Epstein-Barr virus-associated gastric cancer

The present study investigated the effect of a DNA demethylating agent, decitabine, against Epstein-Barr virus-associated gastric cancer (EBVaGC). Decitabine inhibited cell growth and induced G2/M arrest and apoptosis in EBVaGC cell lines. The expression of E-cadherin was up-regulated and cell motility was significantly inhibited in the cells treated with decitabine. The promoter regions of p73 and RUNX3 were demethylated, and their expression was up-regulated by decitabine. They enhanced the transcription of p21, which induced G2/M arrest and apoptosis through down-regulation of c-Myc. Decitabine also induced the expression of BZLF1 in SNU719. Induction of EBV lytic infection was an alternative way to cause apoptosis of the host cells. This study is the first report to reveal the effectiveness of a demethylating agent in inhibiting tumor cell proliferation and up-regulation of E-cadherin in EBVaGC. J. Med. Virol. 89:508-517, 2017. © 2016 Wiley Periodicals, Inc.

Relevance of MET activation and genetic alterations of KRAS and E-cadherin for cetuximab sensitivity of gastric cancer cell lines

PURPOSE

The therapeutic activity of the epidermal growth factor receptor (EGFR)-directed monoclonal antibody cetuximab in gastric cancer is currently being investigated. Reliable biomarkers for the identification of patients who are likely to benefit from the treatment are not available. The aim of the study was to examine the drug sensitivity of five gastric cancer cell lines towards cetuximab as a single agent and to establish predictive markers for chemosensitivity in this cell culture model. The effect of a combination of cetuximab with chemotherapy was compared between a sensitive and a nonsensitive cell line.

METHODS

EGFR expression, activation and localisation, the presence and subcellular localisation of the cell adhesion molecule E-cadherin as well as MET activation were examined by Western blot analysis, flow cytometry and immunofluorescence staining. Cells were treated with varying concentrations of cetuximab and cisplatin and 5-fluorouracil in tumour-relevant concentrations. The biological endpoint was cell viability, which was measured by XTT cell proliferation assay. Response to treatment was evaluated using statistical methods.

RESULTS

We assessed the activity of cetuximab in five gastric cancer cell lines (AGS, KATOIII, MKN1, MKN28 and MKN45). The viability of two cell lines, MKN1 and MKN28, was significantly reduced by cetuximab treatment. High EGFR expression and low levels of receptor activation were associated with cetuximab responsiveness. MET activation as well as mutations of KRAS and CDH1 (gene encoding E-cadherin) was associated with cetuximab resistance.

CONCLUSION

These data indicate that our examinations may be clinically relevant, and the candidate markers should therefore be tested in clinical studies.

Preventing E-cadherin aberrant N-glycosylation at Asn-554 improves its critical function in gastric cancer

E-cadherin is a central molecule in the process of gastric carcinogenesis and its posttranslational modifications by N-glycosylation have been described to induce a deleterious effect on cell adhesion associated with tumor cell invasion. However, the role that site-specific glycosylation of E-cadherin has in its defective function in gastric cancer cells needs to be determined. Using transgenic mice models and human clinical samples, we demonstrated that N-acetylglucosaminyltransferase V (GnT-V)-mediated glycosylation causes an abnormal pattern of E-cadherin expression in the gastric mucosa. In vitro models further indicated that, among the four potential N-glycosylation sites of E-cadherin, Asn-554 is the key site that is selectively modified with β1,6 GlcNAc-branched N-glycans catalyzed by GnT-V. This aberrant glycan modification on this specific asparagine site of E-cadherin was demonstrated to affect its critical functions in gastric cancer cells by affecting E-cadherin cellular localization, cis-dimer formation, molecular assembly and stability of the adherens junctions and cell-cell aggregation, which was further observed in human gastric carcinomas. Interestingly, manipulating this site-specific glycosylation, by preventing Asn-554 from receiving the deleterious branched structures, either by a mutation or by silencing GnT-V, resulted in a protective effect on E-cadherin, precluding its functional dysregulation and contributing to tumor suppression.

Helicobacter pylori-negative gastric cancer: characteristics and endoscopic findings

Helicobacter pylori (H. pylori) leads to chronic gastritis and eventually causes gastric cancer. The prevalence of H. pylori infection is gradually decreasing with improvement of living conditions and eradication therapy. However, some reports have described cases of H. pylori-negative gastric cancers (HpNGC), and the prevalence was 0.42-5.4% of all gastric cancers. Diagnostic criteria of HpNGC vary among the different reports; thus, they have not yet been definitively established. We recommend negative findings in two or more methods that include endoscopic or pathological findings or serum pepsinogen test, and negative urease breath test or serum immunoglobulin G test and no eradication history the minimum criteria for diagnosis of HpNGC. The etiology of gastric cancers, excluding H. pylori infection, is known to be associated with several factors including lifestyle, viral infection, autoimmune disorder and germline mutations, but the main causal factor of HpNGC is still unclear. Regarding the characteristics of HpNGC, the undifferentiated type (UD-type) is more frequent than the differentiated type (D-type). The UD-type is mainly signet ring-cell carcinoma that presents as a discolored lesion in the lower or middle part of the stomach in relatively young patients. The gross type is flat or depressed. The D-type is mainly gastric adenocarcinoma of the fundic gland type that presents as a submucosal tumor-like or flat or depressed lesion in the middle and upper part of the stomach in relatively older patients. Early detection of HpNGC enables minimally invasive treatment which preserves the patient's quality of life. Endoscopists should fully understand the characteristics and endoscopic findings of HpNGC.

Loss of Cdh1 and Trp53 in the uterus induces chronic inflammation with modification of tumor microenvironment

Type II endometrial carcinomas (ECs) are estrogen independent, poorly differentiated tumors that behave in an aggressive manner. As TP53 mutation and CDH1 inactivation occur in 80% of human endometrial type II carcinomas, we hypothesized that mouse uteri lacking both Trp53 and Cdh1 would exhibit a phenotype indicative of neoplastic transformation. Mice with conditional ablation of Cdh1 and Trp53 (Cdh1(d/d)Trp53(d/d)) clearly demonstrate architectural features characteristic of type II ECs, including focal areas of papillary differentiation, protruding cytoplasm into the lumen (hobnailing) and severe nuclear atypia at 6 months of age. Further, Cdh1(d/d)Trp53(d/d) tumors in 12-month-old mice were highly aggressive, and metastasized to nearby and distant organs within the peritoneal cavity, such as abdominal lymph nodes, mesentery and peri-intestinal adipose tissues, demonstrating that tumorigenesis in this model proceeds through the universally recognized morphological intermediates associated with type II endometrial neoplasia. We also observed abundant cell proliferation and complex angiogenesis in the uteri of Cdh1(d/d)Trp53(d/d) mice. Our microarray analysis found that most of the genes differentially regulated in the uteri of Cdh1(d/d)Trp53(d/d) mice were involved in inflammatory responses. CD163 and Arg1, markers for tumor-associated macrophages, were also detected and increased in the uteri of Cdh1(d/d)Trp53(d/d) mice, suggesting that an inflammatory tumor microenvironment with immune cell recruitment is augmenting tumor development in Cdh1(d/d)Trp53(d/d) uteri. Further, inflammatory mediators secreted from CDH1-negative, TP53 mutant endometrial cancer cells induced normal macrophages to express inflammatory-related genes through activation of nuclear factor-κB signaling. These results indicate that absence of CDH1 and TP53 in endometrial cells initiates chronic inflammation, promotes tumor microenvironment development following the recruitment of macrophages and promotes aggressive ECs.

Signaling mechanisms of the epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) is an essential mechanism in embryonic development and tissue repair. EMT also contributes to the progression of disease, including organ fibrosis and cancer. EMT, as well as a similar transition occurring in vascular endothelial cells called endothelial-mesenchymal transition (EndMT), results from the induction of transcription factors that alter gene expression to promote loss of cell-cell adhesion, leading to a shift in cytoskeletal dynamics and a change from epithelial morphology and physiology to the mesenchymal phenotype. Transcription program switching in EMT is induced by signaling pathways mediated by transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP), Wnt-β-catenin, Notch, Hedgehog, and receptor tyrosine kinases. These pathways are activated by various dynamic stimuli from the local microenvironment, including growth factors and cytokines, hypoxia, and contact with the surrounding extracellular matrix (ECM). We discuss how these pathways crosstalk and respond to signals from the microenvironment to regulate the expression and function of EMT-inducing transcription factors in development, physiology, and disease. Understanding these mechanisms will enable the therapeutic control of EMT to promote tissue regeneration, treat fibrosis, and prevent cancer metastasis.

Metastatic tumor evolution and organoid modeling implicate TGFBR2 as a cancer driver in diffuse gastric cancer

Background

Gastric cancer is the second-leading cause of global cancer deaths, with metastatic disease representing the primary cause of mortality. To identify candidate drivers involved in oncogenesis and tumor evolution, we conduct an extensive genome sequencing analysis of metastatic progression in a diffuse gastric cancer. This involves a comparison between a primary tumor from a hereditary diffuse gastric cancer syndrome proband and its recurrence as an ovarian metastasis.

Results

Both the primary tumor and ovarian metastasis have common biallelic loss-of-function of both the CDH1 and TP53 tumor suppressors, indicating a common genetic origin. While the primary tumor exhibits amplification of the Fibroblast growth factor receptor 2 (FGFR2) gene, the metastasis notably lacks FGFR2 amplification but rather possesses unique biallelic alterations of Transforming growth factor-beta receptor 2 (TGFBR2), indicating the divergent in vivo evolution of a TGFBR2-mutant metastatic clonal population in this patient. As TGFBR2 mutations have not previously been functionally validated in gastric cancer, we modeled the metastatic potential of TGFBR2 loss in a murine three-dimensional primary gastric organoid culture. The Tgfbr2 shRNA knockdown within Cdh1^-/-; Tp53^-/- organoids generates invasion in vitro and robust metastatic tumorigenicity in vivo, confirming Tgfbr2 metastasis suppressor activity.

Conclusions

We document the metastatic differentiation and genetic heterogeneity of diffuse gastric cancer and reveal the potential metastatic role of TGFBR2 loss-of-function. In support of this study, we apply a murine primary organoid culture method capable of recapitulating in vivo metastatic gastric cancer. Overall, we describe an integrated approach to identify and functionally validate putative cancer drivers involved in metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0428-9) contains supplementary material, which is available to authorized users.

Study of β-catenin, E-cadherin and vimentin in oral squamous cell carcinoma with and without lymph node metastases

Abstract

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/6506095201182002.

Epithelial-mesenchymal plasticity in carcinoma metastasis

Tumor metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. Metastasis occurs through a series of steps: local invasion, intravasation, transport, extravasation, and colonization. A developmental program termed epithelial-mesenchymal transition (EMT) has been shown to play a critical role in promoting metastasis in epithelium-derived carcinoma. Recent experimental and clinical studies have improved our knowledge of this dynamic program and implicated EMT and its reverse program, mesenchymal-epithelial transition (MET), in the metastatic process. Here, we review the functional requirement of EMT and/or MET during the individual steps of tumor metastasis and discuss the potential of targeting this program when treating metastatic diseases.

Dynamic Switch Between Two Adhesion Phenotypes in Colorectal Cancer Cells

The hematogenous metastatic cascade is mediated by the interaction of cancer cells and the endothelial cell lining of blood vessels. In this work, we examine the colon cancer cell line COLO 205, which grows simultaneously in both adherent and suspended states in culture and can serve as a good model for studying tumor heterogeneity. The two subpopulations of cells have different molecular characteristics despite being from the same parent cell line. We found that the ratio of adherent to suspended cells in culture is maintained at 7:3 (equilibrium ratio). The ratio was maintained even when we separate the two populations and culture them separately. After 8 h in culture the equilibrium was achieved only from either adherent or suspended population. The adherent cells were found to express less E-selectin binding glycans and demonstrated significantly weaker interaction with E-selectin under flow than the suspended cells. Manipulation of the epithelial–mesenchymal transition (EMT) markers β-catenin and E-cadherin expression, either by siRNA knockdown of β-catenin or incubation with E-cadherin antibody-coated microbeads, shifted the ratio of adherent to suspended cells to 9:1. Interestingly, human plasma supplemented media shifted the ratio of adherent to suspended cells in the opposite direction to 1:9, favoring the suspended state. The dynamic COLO 205 population switch presents unique differential phenotypes of their subpopulations and could serve as a good model for studying cell heterogeneity and the EMT process in vitro.

Loss of CDH1 and Pten accelerates cellular invasiveness and angiogenesis in the mouse uterus

E-cadherin (CDH1) is a cell adhesion molecule that coordinates key morphogenetic processes regulating cell growth, cell proliferation, and apoptosis. Loss of CDH1 is a trademark of the cellular event epithelial to mesenchymal transition, which increases the metastatic potential of malignant cells. PTEN is a tumor-suppressor gene commonly mutated in many human cancers, including endometrial cancer. In the mouse uterus, ablation of Pten induces epithelial hyperplasia, leading to endometrial carcinomas. However, loss of Pten alone does not affect longevity until around 5 mo. Similarly, conditional ablation of Cdh1 alone does not predispose mice to cancer. In this study, we characterized the impact of dual Cdh1 and Pten ablation (Cdh1(d/d) Pten(d/d)) in the mouse uterus. We observed that Cdh1(d/d) Pten(d/d) mice died at Postnatal Days 15-19 with massive blood loss. Their uteri were abnormally structured with curly horns, disorganized epithelial structure, and increased cell proliferation. Co-immunostaining of KRT8 and ACTA2 showed invasion of epithelial cells into the myometrium. Further, the uteri of Cdh1(d/d) Pten(d/d) mice had prevalent vascularization in both the endometrium and myometrium. We also observed reduced expression of estrogen and progesterone receptors, loss of cell adherens, and tight junction molecules (CTNNB1 and claudin), as well as activation of AKT in the uteri of Cdh1(d/d) Pten(d/d) mice. However, complex hyperplasia was not found in the uteri of Cdh1(d/d) Pten(d/d) mice. Collectively, these findings suggest that ablation of Pten with Cdh1 in the uterus accelerates cellular invasiveness and angiogenesis and causes early death.

Acute WNT signalling activation perturbs differentiation within the adult stomach and rapidly leads to tumour formation

A role for WNT signalling in gastric carcinogenesis has been suggested due to two major observations. First, patients with germline mutations in adenomatous polyposis coli (APC) are susceptible to stomach polyps and second, in gastric cancer, WNT activation confers a poor prognosis. However, the functional significance of deregulated WNT signalling in gastric homoeostasis and cancer is still unclear. In this study we have addressed this by investigating the immediate effects of WNT signalling activation within the stomach epithelium. We have specifically activated the WNT signalling pathway within the mouse adult gastric epithelium via deletion of either glycogen synthase kinase 3 (GSK3) or APC or via expression of a constitutively active β-catenin protein. WNT pathway deregulation dramatically affects stomach homoeostasis at very short latencies. In the corpus, there is rapid loss of parietal cells with fundic gland polyp (FGP) formation and adenomatous change, which are similar to those observed in familial adenomatous polyposis. In the antrum, adenomas occur from 4 days post-WNT activation. Taken together, these data show a pivotal role for WNT signalling in gastric homoeostasis, FGP formation and adenomagenesis. Loss of the parietal cell population and corresponding FGP formation, an early event in gastric carcinogenesis, as well as antral adenoma formation are immediate effects of nuclear β-catenin translocation and WNT target gene expression. Furthermore, our inducible murine model will permit a better understanding of the molecular changes required to drive tumourigenesis in the stomach.

Advances in gastric cancer prevention

Gastric cancer is a multifactorial neoplastic pathology numbering among its causes both environmental and genetic predisposing factors. It is mainly diffused in South America and South-East Asia, where it shows the highest morbility percentages and it is relatively scarcely diffused in Western countries and North America. Although molecular mechanisms leading to gastric cancer development are only partially known, three main causes are well characterized: Helicobacter pylori (H. pylori) infection, diet rich in salted and/or smoked food and red meat, and epithelial cadherin (E-cadherin) mutations. Unhealthy diet and H. pylori infection are able to induce in stomach cancer cells genotypic and phenotypic transformation, but their effects may be crossed by a diet rich in vegetables and fresh fruits. Various authors have recently focused their attention on the importance of a well balanced diet, suggesting a necessary dietary education starting from childhood. A constant surveillance will be necessary in people carrying E-cadherin mutations, since they are highly prone in developing gastric cancer, also within the inner stomach layers. Above all in the United States, several carriers decided to undergo a gastrectomy, preferring changing their lifestyle than living with the awareness of the development of a possible gastric cancer. This kind of choice is strictly personal, hence a decision cannot be suggested within the clinical management. Here we summarize the key points of gastric cancer prevention analyzing possible strategies referred to the different predisposing factors. We will discuss about the effects of diet, H. pylori infection and E-cadherin mutations and how each of them can be handled.

E-cadherin in canine mast cell tumors: decreased expression and altered subcellular localization in Grade 3 tumors

Mast cell tumors (MCTs) are the most frequent round cell tumors in dogs and comprise approximately 21% of all canine cutaneous tumors. MCTs are highly invasive and metastatic corresponding to the histological grade. E-cadherin is an adhesion molecule expressed in epithelial cells and although it is an epithelial cellular marker, studies have shown expression of E-cadherin in canine round cell tumors. To better characterize the expression pattern of E-cadherin in several different histological grades of MCTs in dogs, the expression and localization of the adhesion molecule was investigated using immunohistochemistry. For this purpose, 18 cutaneous MCTs were classified into three histological grades, 1, 2 or 3. Clinical history and follow-up data were available for all of the dogs. Cytoplasmic and nuclear expressions of E-cadherin in all three types of tumors were verified by immunostaining using two different antibodies. There was decreased E-cadherin expression in the more aggressive MCTs (Grade 3), suggesting an association between E-cadherin and tumor aggressiveness. Additionally, the loss of E-cadherin expression in either the cytoplasm or nucleus in more aggressive and undifferentiated tumor types confirmed the importance of cellular adhesion in tumor behavior.

Transcription initiation arising from E-cadherin/CDH1 intron2: a novel protein isoform that increases gastric cancer cell invasion and angiogenesis

Disruption of E-cadherin (CDH1 gene) expression, subcellular localization or function arises during initiation and progression of almost 90% of all epithelial carcinomas. Nevertheless, the mechanisms through which this occurs are largely unknown. Previous studies showed the importance of CDH1 intron 2 sequences for proper gene and protein expression, supporting these as E-cadherin cis-modulators. Through RACE and RT-PCR, we searched for transcription events arising from CDH1 intron 2 and discovered several new transcripts. One, named CDH1a, with high expression in spleen and absent from normal stomach, was demonstrated to be translated into a novel isoform, differing from canonical E-cadherin in its N-terminal, as determined by mass spectrometry. Quantitative and functional assays showed that when overexpressed in an E-cadherin negative context, CDH1a replaced canonical protein interactions and functions. However, when co-expressed with canonical E-cadherin, CDH1a increased cell invasion and angiogenesis. Further, interferon-induced gene IFITM1 and IFI27 levels were increased upon CDH1a overexpression. Effects on invasion and IFITM1 and IFI27 expression were reverted upon CDH1a-specific knockdown. Importantly, CDH1a was de novo expressed in gastric cancer cell lines. This study presents a new mechanism by which E-cadherin functions are impaired by cis-regulatory mechanisms possibly with the involvement of inflammatory machinery. If confirmed in other cancer models, our data enclose potential for designing targeted therapies to rescue E-cadherin function.

Snail is an independent prognostic predictor for progression and patient survival of gastric cancer

The present study investigated the clinical significance of Snail, a zinc-finger transcription factor, in the development and progression of gastric cancer. To elucidate the relationship between Snail expression and dedifferentiation status with cancer stem cell phenotype in gastric cancer cells, we used western blot analysis, RT-PCR, quantitative real-time PCR and flow cytometry. Immunohistochemistry staining and evaluation of Snail expression in 10 human normal gastric samples versus 103 clinicopathologically characterized gastric cancer tissues followed by statistical analyses were applied to evaluate the prognostic value of Snail expression for progression and patient survival of gastric carcinomas. The results showed that functional Snail expression interlinks dedifferentiation status with cancer stem cell phenotype in gastric cancer cells. In addition, expression levels of Snail in gastric cancer tissues were significantly associated with tumor cell differentiation, local tumor growth, lymph node status, distant metastasis and tumor stage. The overall survival rate of gastric cancer patients with high Snail expression was significantly lower than for those patients with low Snail expression. Multivariate Cox regression analyses showed that Snail expression is an independent prognostic predictor for patient survival of gastric carcinomas. Thus, our data suggest that Snail expression could be a reliable independent prognostic factor to predict gastric carcinoma progression, which might open a new avenue for potential clinical intervention with functional Snail expression in gastric cancer patients.

Epithelial mesenchymal transition and cancer stem cells in esophageal adenocarcinoma originating from Barrett's esophagus

Carcinomas comprise cohesive epithelial cells linked to one another by E-cadherin-based cell-cell junctions. Epithelial mesenchymal transition (EMT) enables carcinoma cells to migrate from the original tissue and invade into stromal components. The E-cadherin promoter is frequently repressed by specific transcriptional repressors including Snail, Slug and Twist. CD133 is known to be a marker of tumor-initiating cells in human cancers. This is the first study to characterize the transcriptional factors for E-cadherin and the representative cancer stem cell marker in specimens of early esophageal adenocarcinoma (EAC) originating from Barrett's esophagus. Ten surgically treated patients were analyzed in the present study. Immunohistochemistry was performed to determine the expression of Snail, Slug, Twist and CD133, and the results were scored. Unlike previous studies of advanced stage esophageal cancers showing the overexpression of each specific transcriptional protein, the invading edges of the tumor were found to abundantly express Snail, Slug, Twist and CD133 in our cohort. Therefore, results of this study suggest that early stage cancers predominantly comprise cells with metastatic potential and this evidence adds legitimacy to the complete removal of early EAC.

Novel tumor suppressive function of Smad4 in serum starvation-induced cell death through PAK1-PUMA pathway

DPC4 (deleted in pancreatic cancer 4)/Smad4 is an essential factor in transforming growth factor (TGF)-β signaling and is also known as a frequently mutated tumor suppressor gene in human pancreatic and colon cancer. However, considering the fact that TGF-β can contribute to cancer progression through transcriptional target genes, such as Snail, MMPs, and epithelial–mesenchymal transition (EMT)-related genes, loss of Smad4 in human cancer would be required for obtaining the TGF-β signaling-independent advantage, which should be essential for cancer cell survival. Here, we provide the evidences about novel role of Smad4, serum-deprivation-induced apoptosis. Elimination of serum can obviously increase the Smad4 expression and induces the cell death by p53-independent PUMA induction. Instead, Smad4-deficient cells show the resistance to serum starvation. Induced Smad4 suppresses the PAK1, which promotes the PUMA destabilization. We also found that Siah-1 and pVHL are involved in PAK1 destabilization and PUMA stabilization. In fact, Smad4-expressed cancer tissues not only show the elevated expression of PAK1, but also support our hypothesis that Smad4 induces PUMA-mediated cell death through PAK1 suppression. Our results strongly suggest that loss of Smad4 renders the resistance to serum-deprivation-induced cell death, which is the TGF-β-independent tumor suppressive role of Smad4.

DNA methyltransferase 1 as a predictive biomarker and potential therapeutic target for chemotherapy in gastric cancer

PURPOSE

DNA methylation contributes to carcinogenesis by mediating transcriptional regulation and chromatin remodelling, which may influence the effect of DNA-damaging drugs. We examined the prognostic and predictive impact of DNA methyltransferase (DNMT) 1 and 3b expression in gastric carcinomas (GC) treated by neoadjuvant chemotherapy. In vitro, DNMT1 expression and chemosensitivity were investigated for a functional relationship and the DNMT inhibitor decitabine (DAC) was tested as an alternative treatment option.

PATIENTS AND METHODS

DNMT1/3b expression was analysed immunohistochemically in 127 pretherapeutic biopsies of neoadjuvant (platinum/5-fluorouracil)-treated GC patients and correlated with response and overall survival (OS). Short hairpin RNA technology was used to knockdown DNMT1 in the GC cell line, AGS. The chemosensitivity of GC cell lines to DAC alone and to DAC in combination with cisplatin was analysed by XTT or colony formation assays.

RESULTS

High DNMT1 and DNMT3b expression was found in 105/127 (83%) and 79/127 (62%) carcinomas, respectively. Patients with low DNMT1 expression demonstrated a significantly better histopathological/clinical response (P=0.03/P=0.008) and OS (P(log-rank)=0.001). In vitro, knockdown of DNMT1 caused an increased chemosensitivity towards cisplatin. Combined treatment with cisplatin and DAC showed a synergistic effect leading to increased cytotoxicity in the cisplatin-resistant cell line AGS.

CONCLUSION

Low DNMT1 expression defines a subgroup of GC patients with better outcomes following platinum/5FU-based neoadjuvant chemotherapy. In vitro data support a functional relationship between DNMT1 and cisplatin sensitivity. Besides its potential use as a predictive biomarker, DNMT1 may represent a promising target for alternative therapeutic strategies for a subset of GC patients.

Mammary-specific inactivation of E-cadherin and p53 impairs functional gland development and leads to pleomorphic invasive lobular carcinoma in mice

Breast cancer is the most common malignancy in women of the Western world. Even though a large percentage of breast cancer patients show pathological complete remission after standard treatment regimes, approximately 30-40% are non-responsive and ultimately develop metastatic disease. To generate a good preclinical model of invasive breast cancer, we have taken a tissue-specific approach to somatically inactivate p53 and E-cadherin, the cardinal cell-cell adhesion receptor that is strongly associated with tumor invasiveness. In breast cancer, E-cadherin is found mutated or otherwise functionally silenced in invasive lobular carcinoma (ILC), which accounts for 10-15% of all breast cancers. We show that mammary-specific stochastic inactivation of conditional E-cadherin and p53 results in impaired mammary gland function during pregnancy through the induction of anoikis resistance of mammary epithelium, resulting in loss of epithelial organization and a dysfunctional mammary gland. Moreover, combined inactivation of E-cadherin and p53 induced lactation-independent development of invasive and metastatic mammary carcinomas, which showed strong resemblance to human pleomorphic ILC. Dissemination patterns of mouse ILC mimic the human malignancy, showing metastasis to the gastrointestinal tract, peritoneum, lung, lymph nodes and bone. Our results confirm that loss of E-cadherin contributes to both mammary tumor initiation and metastasis, and establish a preclinical mouse model of human ILC that can be used for the development of novel intervention strategies to treat invasive breast cancer.

Structure and biochemistry of cadherins and catenins

Classical cadherins mediate specific adhesion at intercellular adherens junctions. Interactions between cadherin ectodomains from apposed cells mediate cell-cell contact, whereas the intracellular region functionally links cadherins to the underlying cytoskeleton. Structural, biophysical, and biochemical studies have provided important insights into the mechanism and specificity of cell-cell adhesion by classical cadherins and their interplay with the cytoskeleton. Adhesive binding arises through exchange of beta strands between the first extracellular cadherin domains (EC1) of partner cadherins from adjacent cells. This "strand-swap" binding mode is common to classical and desmosomal cadherins, but sequence alignments suggest that other cadherins will bind differently. The intracellular region of classical cadherins binds to p120 and beta-catenin, and beta-catenin binds to the F-actin binding protein alpha-catenin. Rather than stably bridging beta-catenin to actin, it appears that alpha-catenin actively regulates the actin cytoskeleton at cadherin-based cell-cell contacts.

Activation of 5-lipoxygenase is required for nicotine mediated epithelial-mesenchymal transition and tumor cell growth

Nicotine is shown to be one of the carcinogenic agents for gastric cancer. Perturbation of epithelial-mesenchymal transition (EMT) results in loss of intracellular adhesions leading to tumor progression. In this study, we examined the underlying mechanism of the long-term effects of nicotine on tumor progression in human gastric cancer cells. Nicotine activated 5-lipoxygenase (5-LOX) in three gastric cancer cell lines (MKN-45, MKN-28 and AGS). Cells treated with nicotine dose- and time-dependently induced cell proliferation, invasion and suppressed apoptosis. In addition, cell cycle progression analysis revealed that activation of 5-LOX modulated the G1/S phase transition regulatory proteins and caused cell proliferation. MK886 (5-LOX activating protein inhibitor) mediated the induction of apoptosis by elevation of caspase-3 and Bax/Bcl2 ratio. Abrogation of 5-LOX repressed featured molecular markers of EMT (inactivation of E-cadherin and activation of transcriptional repressor Snail). Blockade of 5-LOX signaling resulted in downregulation of cyclin D1, matrix metalloproteinase (MMP-7, -9), urokinase plasminogen activator (uPA) and its receptor (uPAR), and pro-apoptotic proteins. Furthermore, suppression of Snail and induction of E-cadherin is extracellular signal-regulated kinase (Erk)-dependent. Thus, we conclude that the promotion effect of nicotine on cancer cell progression and EMT is mediated by Erk/5-LOX signaling pathway.

Hereditary diffuse gastric cancer

Gastric cancer is one of the world's leading causes of cancer mortality. A small percentage of cases can be attributed to heritable mutations in highly penetrant cancer susceptibility genes. In this chapter we will focus on the genetic cause of hereditary diffuse gastric cancer (HDGC). Until 10 years ago, individuals from these families lived with the uncertainty of developing lethal gastric cancer. Today, HDGC families can be identified, tested for causative mutations in CDH1, and for those families where a pathogenic mutation can be identified, prophylactic total gastrectomy can be implemented in asymptomatic mutation carriers who elect to virtually eliminate their risk of developing this lethal disease.

E-cadherin, beta-catenin, and ZEB1 in malignant progression of cancer

The embryonic program 'epithelial-mesenchymal transition' (EMT) is activated during tumor invasion in disseminating cancer cells. Characteristic to these cells is a loss of E-cadherin expression, which can be mediated by EMT-inducing transcriptional repressors, e.g. ZEB1. Consequences of a loss of E-cadherin are an impairment of cell-cell adhesion, which allows detachment of cells, and nuclear localization of beta-catenin. In addition to an accumulation of cancer stem cells, nuclear beta-catenin induces a gene expression pattern favoring tumor invasion, and mounting evidence indicates multiple reciprocal interactions of E-cadherin and beta-catenin with EMT-inducing transcriptional repressors to stabilize an invasive mesenchymal phenotype of epithelial tumor cells.

Reversibility of epithelial-mesenchymal transition (EMT) induced in breast cancer cells by activation of urokinase receptor-dependent cell signaling

Hypoxia induces expression of the urokinase receptor (uPAR) and activates uPAR-dependent cell signaling in cancer cells. This process promotes epithelial-mesenchymal transition (EMT). uPAR overexpression in cancer cells also promotes EMT. In this study, we tested whether uPAR may be targeted to reverse cancer cell EMT. When MDA-MB 468 breast cancer cells were cultured in 1% O(2), uPAR expression increased, as anticipated. Cell-cell junctions were disrupted, vimentin expression increased, and E-cadherin was lost from cell surfaces, indicating EMT. Transferring these cells back to 21% O(2) decreased uPAR expression and reversed the signs of EMT. In uPAR-overexpressing MDA-MB 468 cells, EMT was reversed by silencing expression of endogenously produced urokinase-type plasminogen activator (uPA), which is necessary for uPAR-dependent cell signaling, or by targeting uPAR-activated cell signaling factors, including phosphatidylinositol 3-kinase, Src family kinases, and extracellular signal-regulated kinase. MDA-MB 231 breast cancer cells express high levels of uPA and uPAR and demonstrate mesenchymal cell morphology under normoxic culture conditions (21% O(2)). Silencing uPA expression in MDA-MB-231 cells decreased expression of vimentin and Snail, and induced changes in morphology characteristic of epithelial cells. These results demonstrate that uPAR-initiated cell signaling may be targeted to reverse EMT in cancer.

Suppression of androgen-independent prostate cancer cell aggressiveness by FTY720: validating Runx2 as a potential antimetastatic drug screening platform

PURPOSE

Previously, FTY720 was found to possess potent anticancer effects on various types of cancer. In the present study, we aimed to first verify the role of Runx2 in prostate cancer progression and metastasis, and, subsequently, assessed if FTY720 could modulate Runx2 expression, thus interfering downstream events regulated by this protein.

EXPERIMENTAL DESIGN

First, the association between Runx2 and prostate cancer progression was assessed using localized prostate cancer specimens and mechanistic investigation of Runx2-induced cancer aggressiveness was then carried out. Subsequently, the effect of FTY720 on Runx2 expression and transcriptional activity was investigated using PC-3 cells, which highly expressed Runx2 protein. Last, the involvement of Runx2 in FTY720-induced anticancer effects was evaluated by modulating Runx2 expression in various prostate cancer cell lines.

RESULTS

Runx2 nuclear expression was found to be up-regulated in prostate cancer and its expression could be used as a predictor of metastasis in prostate cancer. Further mechanistic studies indicated that Runx2 accelerated prostate cancer aggressiveness through promotion of cadherin switching, invasion toward collagen I, and Akt activation. Subsequently, we found that FTY720 treatment down-regulated Runx2 expression and its transcriptional activity, as well as inhibited its regulated downstream events. More importantly, silencing Runx2 in PC-3 enhanced FTY720-induced anticancer effects as well as cell viability inhibition, whereas overexpressing Runx2 in 22Rv1 that expressed very low endogenous Runx2 protein conferred resistance in the same events.

CONCLUSION

This study provided a novel mechanism for the anticancer effect of FTY720 on advanced prostate cancer, thus highlighting the therapeutic potential of this drug in treating this disease.

An essential role for p120-catenin in Src- and Rac1-mediated anchorage-independent cell growth

p120-catenin regulates epithelial cadherin stability and has been suggested to function as a tumor suppressor. In this study, we used anchorage-independent growth (AIG), a classical in vitro tumorigenicity assay, to examine the role of p120 in a different context, namely oncogene-mediated tumorigenesis. Surprisingly, p120 ablation by short hairpin RNA completely blocked AIG induced by both Rac1 and Src. This role for p120 was traced to its activity in suppression of the RhoA-ROCK pathway, which appears to be essential for AIG. Remarkably, the AIG block associated with p120 ablation was completely reversed by inhibition of the downstream RhoA effector ROCK. Harvey-Ras (H-Ras)-induced AIG was also dependent on suppression of the ROCK cascade but was p120 independent because its action on the pathway occurred downstream of p120. The data suggest that p120 modulates oncogenic signaling pathways important for AIG. Although H-Ras bypasses p120, a unifying theme for all three oncogenes is the requirement to suppress ROCK, which may act as a gatekeeper for the transition to anchorage independence.

Alterations of DNA methylation and clinicopathological diversity of human cancers

Alterations of DNA methylation can account for the histological heterogeneity, reflected in the stepwise progression and complex biological characteristics of human cancers, that genetic alterations alone cannot explain. Analysis of DNA methylation status in tissue samples can be an aid to understanding the molecular mechanisms of multistage carcinogenesis. Human cancer cells show a drastic change in DNA methylation status, that is, overall DNA hypomethylation and regional DNA hypermethylation, which results in chromosomal instability and silencing of tumor-suppressor genes. Overexpression of DNA methyltransferase (DNMT) 1 is not a secondary result of increased cell proliferative activity but may underline the CpG island methylator phenotype of cancers. Splicing alteration of DNMT3B may result in chromosomal instability through DNA hypomethylation of pericentromeric satellite regions. Alterations of DNA methylation are observed even in the precancerous stage frequently associated with chronic inflammation and/or persistent viral infection or with cigarette smoking. Precancerous conditions showing alterations of DNA methylation may generate more malignant cancers. Aberrant DNA methylation is significantly associated with aggressiveness of cancers and poorer outcome of cancer patients. Genome-wide analysis of DNA methylation status based on array-based technology may identify DNA methylation profiles that can be used as appropriate indicators for carcinogenetic risk estimation and prognostication.

Establishment of an ovarian metastasis model and possible involvement of E-cadherin down-regulation in the metastasis

Clinical observations of cases of ovarian metastasis suggest that there may be a unique mechanism underlying ovarian-specific metastasis. This study was undertaken to establish an in vivo model of metastasis to the ovary, and to investigate the mechanism of ovarian-specific metastasis. We examined the capacity for ovarian metastasis in eight different human carcinoma cell lines by implantation in female NOD/SCID mice transvenously and intraperitoneally. By transvenous inoculation, only RERF-LC-AI, a poorly differentiated carcinoma cell line, frequently demonstrated ovarian metastasis. By intraperitoneal inoculation, four of the eight cell lines (HGC27, MKN-45, KATO-III, and RERF-LC-AI) metastasized to the ovary. We compared E-cadherin expression among ovarian metastatic cell lines and others. All of these four ovarian metastatic cell lines and HSKTC, a Krukenberg tumor cell line, showed E-cadherin down-regulation and others did not. E-cadherin was then forcibly expressed in RERF-LC-AI, and inhibited ovarian metastasis completely. The capacity for metastasizing to the other organs was not affected by E-cadherin expression. We also performed histological investigation of clinical ovarian-metastatic tumor cases. About half of all ovarian-metastatic tumor cases showed loss or reduction of E-cadherin expression. These data suggest that E-cadherin down-regulation may be involved in ovarian-specific metastasis.

Epithelial-mesenchymal transition mediated tumourigenesis in the gastrointestinal tract

Epithelial-mesenchymal transition (EMT) is a highly conserved process that has been well characterised in embryogenesis. Studies have shown that the aberrant activation of EMT in adult epithelia can promote tumour metastasis by repressing cell adhesion molecules, including epithelial (E)-cadherin. Reduced intracellular adhesion may allow tumour cells to disseminate and spread throughout the body. A number of transcription proteins of the Snail superfamily have been implicated in EMT. These proteins have been shown to be over-expressed in advanced gastrointestinal (GI) tumours including oesophageal adenocarcinomas, colorectal carcinomas, gastric and pancreatic cancers, with a concomitant reduction in the expression of E-cadherin. Regulators of EMT may provide novel clinical targets to detect GI cancers early, so that cancers previously associated with a poor prognosis such as pancreatic cancer can be diagnosed before they become inoperable. Furthermore, pharmacological therapies designed to inhibit these proteins will aim to prevent local and distant tumour invasion.

Inter-cellular adhesion disruption and the RAS/RAF and beta-catenin signalling in lung cancer progression

Cadherin cell adhesion molecules play an essential role in creating tight intercellular association and their loss has been correlated with poor prognosis in human cancer. Mutational activation of protein kinases and loss of cell adhesion occur together in human lung adenocarcinoma but how these two pathways interconnect is only poorly understood. Mouse models of human lung adenocarcinoma with oncogene expression targeted to subtypes of lung epithelial cells led to formation of adenomas or adenocarcinomas that lacked metastatic potential. Conditional genetic abrogation of epithelial tumour cell adhesion in mice with benign lung tumours induced by oncogenic RAF kinase has been demonstrated to induce intratumourous vascularization (angiogenic switch), progression to invasive adenocarcinoma and micrometastasis. Importantly, breaking cell adhesion in benign oncogene-driven lung tumour cells activated beta-catenin signalling and induced the expression of several genes that are normally expressed in intestine rather than the lung. I will discuss potential routes to nuclear beta-catenin signalling in cancer and how nuclear beta-catenin may epigenetically alter the plasticity of tumour cells during malignant progression.

Combined analysis of Rac1, IQGAP1, Tiam1 and E-cadherin expression in gastric cancer

Rho GTPases are a family of major regulators of E-cadherin-mediated cell adhesion that are implicated in the carcinogenic process by deregulated expression of the family members itself or of upstream modulators or downstream effectors. Combined investigation of the Rho GTPase Rac1, the effector protein IQGAP1 and the activator Tiam1 in relation to expression or mutation of E-cadherin in gastric adenocarcinomas has not been reported. The aim of the study was to determine the expression and prognostic significance of Rac1, IQGAP1, Tiam1 and E-cadherin in gastric adenocarcinomas. Gastric carcinomas of 76 patients were investigated immunohistochemically in a tissue microarray study for expression of Rac1, IQGAP1, Tiam1 and E-cadherin. Correlations with clinical and follow-up data were examined. Moderate or strong reactivity for Rac1 was observed in 46% and for Tiam1 in 56% of tumors. Expression of IQGAP1 was present in 59% and of E-cadherin in 87% of tumors. While Rac1 and E-cadherin expression were not related to prognosis, a trend was observed between a lack of IQGAP1 expression (log-rank 0.088) as well as presence of Tiam1 (log-rank 0.097) and favorable prognosis in Kaplan-Meier survival analysis. Expression of Rac1 was positively linked to IQGAP1 expression (P=0.007, r=0.343) and tended to be inversely associated with expression of E-cadherin (P=0.055, r=-0.245). In conclusion, we observed deregulated expression of Rac1, IQGAP1, Tiam1 and E-cadherin in gastric cancer. We present evidence that either upregulation (for Rac1 and IQGAP1) or downregulation (for Tiam1 and E-cadherin) occurs. Rac1 and E-cadherin expression were not related to prognosis, while trends pointing to favorable prognosis of patients with Tiam1 expression and a lack of IQGAP1 expression were observed. These results indicate that the investigated regulators of E-cadherin-mediated cell adhesion play a role in gastric carcinogenesis.