Clinical significance of E-cadherin as a prognostic marker in thyroid carcinomas

The aim of this study was to evaluate the expression of E-cadherin as a potential marker for the prognosis of thyroid carcinomas. In normal thyroid (n = 8), the expression of E-cadherin messenger ribonucleic acid levels was uniformly high and seemed to be restricted to thyrocytes. Steady-state messenger ribonucleic acid levels and immunostaining were both completely lost in undifferentiated thyroid carcinomas (n = 7) and were variably reduced in differentiated thyroid carcinomas (n = 44). In a follow-up study during a mean of 4.5 +/- 1.4 yr, E-cadherin messenger ribonucleic acid and immunohistochemical expression were compared with the initial clinicopathological parameters and with locoregional recurrence and the development of nodal or distant metastases in differentiated thyroid carcinomas. Immunohistochemical expression of E-cadherin was greatly reduced with the progression to primary tumor stage 4 (pT4) tumors. In parallel, patients with pT4 tumors had a higher rate of locoregional tumor recurrence and distant metastasis than did the group of patients with pT1-3 tumors. In 5 of 29 patients with pT4 tumors, positive E-cadherin staining of more than 30% of the cells was detected. None of these patients showed signs of a regional recurrence or distant metastases during an observation period of 4.3 +/- 1.1 yr. In 13 patients with E-cadherin-positive tumors, none developed new distant metastases which was in contrast to 7 of the group of 31 patients with less than 30% E-cadherin-positive cells. Thus, E-cadherin expression seems to be associated with the dedifferentiation, progression, and metastatic spread of thyroid carcinomas and may be a useful marker for the prognosis of these tumors.

Mutation of juxtamembrane tyrosine residue 1001 suppresses loss-of-function mutations of the met receptor in epithelial cells

Signals transduced by the met tyrosine kinase, which is the receptor for scatter factor/hepatocyte growth factor, are of major importance for the regulation of epithelial cell motility, morphogenesis, and proliferation. We report here that different sets of tyrosine residues in the cytoplasmic domain of the met receptor affect signal transduction in epithelial cells in a positive or negative fashion: mutation of the C-terminal tyrosine residues 13-16 (Y1311, Y1347, Y1354, and Y1363) reduced or abolished ligand-induced cell motility and branching morphogenesis. In contrast, mutation of the juxtamembrane tyrosine residue 2 (Y1001) produced constitutively mobile, fibroblastoid cells. Furthermore, the gain-of-function mutation of tyrosine residue 2 suppressed the loss-of-function mutations of tyrosine residue 15 or 16. The opposite roles of the juxtamembrane and C-terminal tyrosine residues may explain the suggested dual function of the met receptor in both epithelial-mesenchymal interactions and tumor progression.

E-cadherin as a tumor (invasion) suppressor gene

Diffuse-type gastric carcinomas show diminished cell-cell adhesion. A recent paper reports that 50% of these carcinomas contain mutations in the E-cadherin gene, resulting in the destruction of the calcium-binding sites of E-cadherin, and providing strong in vivo evidence that alterations in E-cadherin play a major role in the development of this particular type of cancer and the short survival of the patients.

Characterization of the scatter factor/hepatocyte growth factor gene promoter. Positive and negative regulatory elements direct gene expression to mesenchymal cells

Scatter factor/hepatocyte growth factor (SF/HGF) and its receptor c-Met represent a paracrine signaling system involved in mesenchymal-epithelial interactions during development and during tumor progression. We have examined the promoters of the mouse and human SF/HGF genes by deletion mapping followed by CAT assays as well as by gel retardation and footprinting analysis. The promoter sequences are highly conserved (89.5% identity) up to position -453 from the major transcription start site but diverged considerably further upstream. Both promoters are active in mesenchymal but not epithelial cells thus reflecting the expression pattern of the SF/HGF gene in cells in vitro and in vivo. We have here identified two regulatory sequences in the SF/HGF promoter: a negative element at positions -239 to -258 and a positive element near the major transcription start site; specific deletions destroyed the activities of these elements. We were not able to localize elements on the SF/HGF promoter region that mediate the previously described effects of transforming growth factor beta, 12-O-tetradecanoylphorbol-13-acetate, and coculture of epithelial cells on SF/HGF gene expression. This study represents a first step toward understanding the intricately regulated and cell type-specific expression of the paracrine acting SF/HGF.

Epithelial-mesenchymal transitions in development and tumor progression

Epithelial-mesenchymal transitions play important roles in development and malignancy. Here we discuss molecular events in the control of such transitions: changes in cellular adhesion components, action of oncogenes and tyrosine kinase receptors, as well as activation of transcription factors. In development, epithelial-mesenchymal transitions take place in a temporally and spatially controlled manner, whereas in tumors these changes are highly uncontrolled. Loss of epithelial character is typically observed late in progression of human carcinomas, and correlates there with the acquisition of invasive and metastatic potential.

E-cadherin and APC compete for the interaction with beta-catenin and the cytoskeleton

beta-Catenin is involved in the formation of adherens junctions of mammalian epithelia. It interacts with the cell adhesion molecule E-cadherin and also with the tumor suppressor gene product APC, and the Drosophila homologue of beta-catenin, armadillo, mediates morphogenetic signals. We demonstrate here that E-cadherin and APC directly compete for binding to the internal, armadillo-like repeats of beta-catenin; the NH2-terminal domain of beta-catenin mediates the interaction of the alternative E-cadherin and APC complexes to the cytoskeleton by binding to alpha-catenin. Plakoglobin (gamma-catenin), which is structurally related to beta-catenin, mediates identical interactions. We thus show that the APC tumor suppressor gene product forms strikingly similar associations as found in cell junctions and suggest that beta-catenin and plakoglobin are central regulators of cell adhesion, cytoskeletal interaction, and tumor suppression.

Tumor-suppressor gene products in cell contacts: the cadherin-APC-armadillo connection

Various structural components of intercellular junctions have recently been found to represent (or be related to) products of tumor-suppressor genes. The tumor-suppressor gene product adenomatous polyposis coli (APC) binds to beta 2-catenin (homologous to the product of Drosophila armadillo), which is cytoplasmically associated with the cell adhesion molecule E-cadherin.

The motility signal of scatter factor/hepatocyte growth factor mediated through the receptor tyrosine kinase met requires intracellular action of Ras

Scatter factor/hepatocyte growth factor (SF/HGF) has various biological effects upon different cells, i.e. induces increased motility and proliferation as well as invasiveness and morphogenesis. The signals given to epithelial cells by SF/HGF are all mediated through the Met receptor tyrosine kinase (Weidner, K. M., Sachs, M., and Birchmeier, W. (1993) J. Cell Biol. 111, 145-154) suggesting that signal diversity is due to the interplay of different downstream pathways. It has also been shown that SF/HGF activates the protooncogene product Ras, i.e. stimulates guanine nucleotide exchange. In order to examine whether Ras is involved in mediating the dissociation and motility signal of SF/HGF to epithelial cells, we have expressed in Madin-Darby canine kidney cells the dominant-negative N17Ras under the control of a modified metallothionein promoter. Induced expression of N17Ras by the addition of Zn2+ clearly prevented dissociation of the cells by SF/HGF. These data indicate that the Ras pathway is indeed essential to mediate the motility signal of SF/HGF-Met to the cell-cell adhesion system and the cytoskeleton of epithelial cells.

Localization of the human beta-catenin gene (CTNNB1) to 3p21: a region implicated in tumor development

The human beta-catenin locus (CTNNB1) was mapped by in situ fluorescence analysis to band p21 on the short arm of chromosome 3, a region frequently affected by somatic alterations in a variety of tumors. PCR primers for the genomic amplification of beta-catenin sequences were selected on the basis of homology to exon 4 of the Drosophila armadillo gene. Analysis of a panel of somatic cell hybrids confirmed the localization of beta-catenin on human chromosome 3. Furthermore, exclusion mapping of three hybrids carrying defined fragments of the short arm of human chromosome 3 allowed us to determine the position of the CTNNB1 locus close to the marker D3S2 in 3p21.

Inverse relation of E-cadherin and autocrine motility factor receptor expression as a prognostic factor in patients with bladder carcinomas

Down-regulation of E-cadherin, an intercellular adhesion molecule, and up-regulation of autocrine motility factor receptor (gp78) expressions have been shown to play a role in tumor cell invasion and metastasis. Monoclonal antibodies against E-cadherin and gp78 were used to stain serial snap-frozen sections of 12 normal bladder and 83 bladder carcinoma specimens (27 noninvasive, 53 invasive, and 3 metastases). In normal urothelium, E-cadherin is expressed while gp78 is not. Positive expression of E-cadherin and negative expression of gp78 were found to be associated with a low risk of clinical progression in the superficial bladder carcinoma patient group. While reduction in E-cadherin concomitantly with an increase in gp78 expression was associated with poor prognosis, 71% of the patients (n = 30) underwent rapid cancer progression, and 32% of the patients died of cancer-related disease at a median of 2 years after initial diagnosis. Thus, it is suggested that reduction of E-cadherin expression associated with an increase in the level of gp78 in bladder cancers may define a high risk group of patients. The dual use of these two antigens may improve early diagnosis of high risk bladder cancer patients and influence treatment decisions.

Cadherin expression in carcinomas: role in the formation of cell junctions and the prevention of invasiveness

It has been realized that the loss of epithelial differentiation in carcinomas, which is accompanied by higher mobility and invasiveness of the tumor cells, is often a consequence of reduced intercellular adhesion. A variety of recent reports have indicated that the primary cause for the 'scattering' of the cells in invasive carcinomas is a disturbance of the integrity of intercellular junctions, often involving loss of a functional cell-cell adhesion molecule E-cadherin. It has also been suggested that during invasion, carcinoma cells convert to a sort of mesenchymal stage, as do normal epithelial cells during development. In the present review, permanent and transient molecular mechanisms are discussed which lead to the impairment of junction integrity of the epithelial cells and thus to the progression of carcinomas towards a more metastatic state. Furthermore, the now extensive literature on the down-regulation of E-cadherin expression in human and animal carcinomas is reviewed in detail.

E-cadherin gene mutations in human gastric carcinoma cell lines

Reduced expression of E-cadherin has been regarded as one of the main molecular events involved in dysfunction of the cell-cell adhesion system, triggering cancer invasion and metastasis. However, even with a sufficient amount of E-cadherin, cell-cell adhesion is sometimes lost in "diffusely invasive" human carcinomas. Ten human cancer cell lines, showing growth characterized morphologically by loose cell-cell adhesion, were analyzed for possible structural abnormalities of their expressed E-cadherin. Four of the cell lines showed strong mRNA and protein expression with no nucleotide sequence abnormalities, and mRNA was absent in four other cell lines. mRNA sequence was abnormal in the remaining two gastric carcinoma cell lines. In MKN45 (poorly differentiated adenocarcinoma), this involved a 12-bp in-frame deletion with strong expression of mRNA and protein. In KATO-III (signet ring cell carcinoma), there were four mRNA species with insertions of different sizes, among which the major transcripts (with a 7-bp insertion) caused a frameshift, and expression of both mRNA and protein was markedly reduced. In these two cell lines, DNA mutations were detected around exon-intron junctions, revealing that aberrant RNA splicing was the cause of the mRNA abnormalities. In addition, the wild-type allele of the E-cadherin locus was lost, suggesting that the E-cadherin gene had been inactivated by two hits (mutation and allele loss), similar to the mechanism for inactivation of tumor suppressor genes.

Molecular aspects of the loss of cell adhesion and gain of invasiveness in carcinomas

It has been realized that the loss of epithelial differentiation in carcinomas, which is accompanied by higher mobility and invasiveness of the tumor cells, is often a consequence of reduced intercellular adhesion. A variety of recent reports have indicated that the primary cause for the 'scattering' of the cells in invasive carcinomas is a disturbance of the integrity of intercellular junctions. It has also been suggested that during invasion, carcinoma cells convert to a sort of mesenchymal stage, as do normal epithelial cells during development. This paper discusses permanent and transient molecular mechanisms which lead to the impairment of junction integrity of epithelial cells and thus to the progression of carcinomas towards a more invasive state.

Differences of E-cadherin expression levels and patterns in primary and metastatic human lung cancer

Normal lung epithelium and 52 lung carcinomas obtained at surgical resection were examined by immunofluorescence for their expression levels and patterns of the calcium-dependent intercellular adhesion molecule E-cadherin. In dysplastic lung tissue and in well-differentiated squamous cell and adenocarcinomas, expression of E-cadherin was confined to the lateral cell border, similar to the expression level and pattern of normal lung tissue. The E-cadherin level was reduced and expression pattern was spotty or diffuse in moderately and poorly differentiated squamous cell and in small cell carcinomas of the lung. Most metastases resected also had a reduced level and an altered pattern of E-cadherin expression. In contrast, no such correlation was found in adenocarcinomas of the lung. This indicates that different cellular mechanisms are responsible in the progression of squamous cell carcinomas and adenocarcinomas of the lung.

Differential loss of E-cadherin expression in infiltrating ductal and lobular breast carcinomas

The epithelial-specific cell-cell adhesion molecule E-cadherin was analyzed immunohistochemically on tissue sections of 89 human primary infiltrating breast carcinomas, using monoclonal antibodies 6F9 (for cryostat sections) and 5H9 (for cryostat and paraffin sections). The tumors included 41 well and moderately differentiated infiltrating ductal carcinomas (IDCs) most of which (78%) showed strong linear staining at the cell borders at a level, as high as luminal cells of normal mammary glands. The 26 poorly differentiated, more highly malignant IDCs examined also were all positive for E-cadherin, although a higher proportion of them (54%) showed reduced staining, which was heterogeneous and dotted over the cell borders. In contrast, 19 of 22 infiltrating lobular carcinomas (ILCs), which were either of the dispersed (classical), solid, or the mixed type, did not express E-cadherin, whereas three cases showed weak staining. In situ lesions of ILCs and pure lobular carcinoma in situ (four cases) were all E-cadherin negative, whereas intraductal carcinomas (11 cases) exhibited mostly strong staining. The results were confirmed by Western blotting. The data indicate that loss of E-cadherin expression is an early event in the formation of the lobular type of breast carcinomas. The absence of E-cadherin signifies a partial loss of epithelial differentiation and may account for the extended spread of lobular carcinoma in situ and the peculiar diffuse invasion mode of ILC. The generation of dedifferentiated IDCs can only in part be correlated with reduced expression of the intercellular adhesion molecule E-cadherin. Other factors are obviously also involved during invasion of this carcinoma type.

Molecular mechanisms leading to loss of differentiation and gain of invasiveness in epithelial cells

It has been realized for some time that the loss of epithelial differentiation in carcinomas, which is accompanied by higher mobility and invasiveness of the tumor cells, is a consequence of reduced intercellular adhesion. A variety of recent reports have indicated that the primary cause for the 'scattering' of the cells in invasive carcinomas is a loss of the integrity of intercellular junctions. Thus, defects in expression or structure of several components of the epithelial adherens junctions (e.g. E-cadherin, alpha-catenin) can occur, and our increased knowledge about the molecules of the junctions allows an explanation of these defects in molecular terms in some of the cases. Furthermore, tyrosine phosphorylation of junctional components (e.g. beta-catenin) appears to play a role in the assembly and disassembly of cell-cell contacts. Some of the effectors of epithelial junction formation are tyrosine protein kinases, e.g. the scatter factor/hepatocyte growth factor receptor c-Met, the FGF receptors and the pp60src kinase. The importance of tyrosine phosphorylation in junctions during tumor development is becoming increasingly evident.

Deletion of the E-cadherin gene in hepatitis B virus-positive Chinese hepatocellular carcinomas

Frequent allele loss from chromosome 16q was recently described for human tumors of the breast, prostate gland and liver, indicating the possible presence of a tumor-suppressor gene on that chromosome arm. In this study, the chromosome 16 allele status of 38 hepatocellular carcinomas in Chinese patients was determined with restriction-fragment-length polymorphism analysis. Tumor-specific allele loss was detected in 14 (74%) of 19 patients informative for 16p markers and in 22 (85%) of 26 patients informative for 16q markers. Quantitative densitometric analysis revealed reduction to hemizygosity of the E-cadherin cell adhesion gene (localized to 16q22.1) in 18 (64%) of the 28 patients for whom quantitative data were available. Reduced expression of E-cadherin has been associated with invasion and metastasis in several human cell lines and primary tumors, and our results suggest that one mechanism of reduced E-cadherin expression is the loss of one copy of the E-cadherin gene.

Molecular mechanisms leading to cell junction (cadherin) deficiency in invasive carcinomas

It has been realized for some time that the loss of epithelial differentiation in carcinomas, which is accompanied by higher mobility and invasiveness of the tumor cells, is a consequence of reduced intercellular adhesion. A variety of recent reports have indicated that the primary cause for the 'scattering' of the cells in invasive carcinomas is a loss of the integrity of intercellular adherens junctions often involving loss of a functional cell-cell adhesion molecule E-cadherin. In the present review, permanent and transient molecular mechanisms are discussed which lead to the impairment of junctional integrity of cells and thus the progression of carcinomas toward a more metastatic state.

The Met receptor tyrosine kinase transduces motility, proliferation, and morphogenic signals of scatter factor/hepatocyte growth factor in epithelial cells

Depending on the target cells and culture conditions, scatter factor/hepatocyte growth factor (SF/HGF) mediates several distinct activities, i.e., cell motility, proliferation, invasiveness, tubular morphogenesis, angiogenesis, or cytotoxicity. A small isoform of SF/HGF encoded by a natural splice variant, which consists of the NH2-terminal hairpin structure and the first two kringle domains but not the protease homology region, induces cell motility but not mitogenesis. Two types of SF/HGF receptors have recently been discovered in epithelial cells, the high affinity c-Met receptor tyrosine kinase, and low affinity/high capacity binding sites, which are probably located on heparan sulfate proteoglycans. In the present study, we have addressed the question whether the various biological activities of SF/HGF are transduced into cells by a single type of receptor. We have here examined MDCK epithelial cells transfected with a hybrid cDNA encoding the ligand binding domain of the nerve growth factor (NGF) receptor and the membrane-spanning and tyrosine kinase domains of the Met receptor. We demonstrate that all biological effects of SF/HGF upon epithelial cells such as the induction of cell motility, proliferation, invasiveness, and tubular morphogenesis can now be triggered by the addition of NGF. Thus, it is likely that all known biological signals of SF/HGF are transduced through the receptor tyrosine kinase encoded by the c-Met protooncogene.

E-cadherin expression in primary and metastatic gastric cancer: down-regulation correlates with cellular dedifferentiation and glandular disintegration

Expression of the epithelial cell adhesion molecule E-cadherin in primary and metastatic gastric carcinoma was examined using immunohistochemical analyses. Compared to normal mucosa, 92% of the primary tumors (n = 60) showed reduced E-cadherin expression, suggesting that down-regulation of this cell adhesion molecule is a common early event in gastric tumorigenesis. No significant correlation was found between E-cadherin expression and tumor diameter, lymphatic vessel invasion, Borrmann classification, lymph node status, or manifest metastases. Although advanced tumors (tumor stage 3/4) showed a loss of E-cadherin-positive cells (< or = 50% cells/lesion, P = 0.0168), the most significant correlation was observed between low E-cadherin expression and cellular dedifferentiation (grading 3/4, P = 0.0001) and disintegration of tissue architecture (Lauren and WHO classifications, P = 0.0001). Low E-cadherin expression (< or = 50% cells/lesion) was associated with tumor recurrence (P = 0.0013) and mortality (P = 0.0246). E-cadherin expression in metastatic lesions (n = 58) also correlated with the degree of glandular differentiation (P = 0.0001). Significant correlation (rs = 0.686) was observed between E-cadherin expression in primary and metastatic lesions from individual patients (n = 39). However, while metastases derived from E-cadherin-negative tumors remained negative, those originating from E-cadherin-positive tumors frequently demonstrated increased levels of expression. Evaluation of multiple metastases in 11 patients revealed uniformly strong E-cadherin expression in liver metastases, suggesting a possible regulatory role of the microenvironment.