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W Birchmeier

Publications and source records attributed to W Birchmeier.

At least 73 records · Page 4Linked to original sources
PubMed1994

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.

Amino Acid Sequence↗
PubMed1994

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.

Adenocarcinoma↗
PubMed1994

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.

Adenomatous Polyposis Coli Protein↗
PubMed1994

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.

Adenomatous Polyposis Coli Protein↗
PubMed1994

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.

Animals↗
PubMed1993

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.

Cadherins↗
PubMed1993

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.

Adult↗
PubMed1993

Loss of epithelial differentiation and gain of invasiveness correlates with tyrosine phosphorylation of the E-cadherin/beta-catenin complex in cells transformed with a temperature-sensitive v-SRC gene.

Loss of histotypic organization of epithelial cells is a common feature in normal development as well as in the invasion of carcinomas. Here we show that the v-src oncogene is a potent effector of epithelial differentiation and invasiveness. MDCK epithelial cells transformed with a temperature-sensitive mutant of v-src exhibit a strictly epithelial phenotype at the nonpermissive temperature for pp60v-src activity (40.5 degrees C) but rapidly loose cell-to-cell contacts and acquire a fibroblast-like morphology after culture at the permissive temperature (35 degrees C). Furthermore, the invasiveness of the cells into collagen gels or into chick heart fragments was increased at the permissive temperature. The profound effects of v-src on intercellular adhesion were not linked to changes in the levels of expression of the epithelial cell adhesion molecule E-cadherin. Rather, we observed an increase in tyrosine phosphorylation of E-cadherin and, in particular, of the associated protein beta-catenin. These results suggest a mechanism by which v-src counteracts junctional assembly and thereby promotes invasiveness and dedifferentiation of epithelial cells through phosphorylation of the E-cadherin/catenin complex.

Animals↗
PubMed1993

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.

Amino Acid Sequence↗
PubMed1993

Properties and functions of scatter factor/hepatocyte growth factor and its receptor c-Met.

Scatter factor (SF), a cell motility factor with a multimodular structure, is identical to hepatocyte growth factor (HGF), a potent mitogen of various cell types. The receptor for SF/HGF has recently been identified as the c-Met proto-oncogene product, a transmembrane receptor tyrosine kinase. Depending on the target cells and culture conditions, SF/HGF has several distinct activities in vitro, i.e., it induces cell motility, proliferation, invasiveness, tubular morphogenesis, angiogenesis, or cytotoxicity. In vivo, SF/HGF might be involved in tissue regeneration, tumor progression, and embryological processes.

Amino Acid Sequence↗
PubMed1993

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.

Animals↗
PubMed1993

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.

Adult↗
PubMed1993

Molecular characteristics of HGF-SF and its role in cell motility and invasion.

Scatter factor (SF), a secretory protein of fibroblasts, dissociates and increases the motility of epithelial cells and may be involved in cell migration processes during embryogenesis and tumor progression. Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and other cells, and is thought to play a role in liver regeneration. We have presented structural and functional evidence that human SF and human HGF are identical proteins encoded by a single gene, since (i) no differences could be found by protein sequencing, by cDNA analysis, or by immunological comparison, and (ii) SF acts as a hepatocyte growth factor--i.e., stimulates DNA synthesis of primary hepatocytes and is a morphogen of kidney epithelial cells--whereas HGF exhibits SF activity--i.e., dissociates and induces invasiveness of various epithelial cells. Furthermore, there exists only one gene for human HGF-SF which is located on chromosome 7, bands q11.2-21 (Weidner et al., Proc. Natl. Acad. Sci. USA 88, 7001-7005, 1991). HGF-SF has been found to be the ligand of the c-met receptor tyrosine kinase (Naldini et al., EMBO J. 10, 2867-2878, 1991b). We have recently used transient expression of naturally occurring and in vitro mutagenized cDNAs of HGF-SF in order to delineate the protein domains necessary for biological activity and c-met receptor activation. (i) A single-chain HGF-SF resulting from the destruction of the protease cleavage site between heavy and light chain (Arg494 to Gln) was largely inactive, indicating that proteolytic cleavage is essential for acquisition of the biologically active conformation. (ii) A HGF-SF splice variant encoding a protein with a 5 amino acid deletion in the first kringle domain was as highly active as the wild type molecule. (iii) The separately expressed light chain (with serine protease homology) was inactive in all assays tested. (iv) The separate heavy chain as well as a naturally occurring splice variant consisting of the N-terminus and the first two kringle domains bound the met receptor, stimulated its tyrosine phosphorylation, and induced dissociation of epithelial cells but not mitogenesis. These data indicate that a functional domain in the N-terminal region and/or the first two kringle domains of HGF-SF is sufficient for binding to and activation of the met receptor (Hartmann et al., Proc. Natl. Acad. Sci. USA, in press).

Animals↗
PubMed1993

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.

Animals↗