Involvement of the NGFI-A gene in the differentiation of neuroblastoma cells

The transcription factor NGFI-A is an early response gene that has been implicated in the regulation of cell growth and differentiation and, more recently, in apoptosis. This gene is expressed in many tissues, and is very abundant in the brain. However, little is known about its functional role in the differentiation of this tissue. In the present work we investigated the role of NGFI-A in serum withdrawal-induced differentiation in N2A neuroblastoma cells. To do so, we studied the effect of NGFI-A antisense oligonucleotides and NGFI-A overexpression on this process. We show that neuroblastoma cells treated with an NGFI-A antisense oligonucleotide do not undergo normal morphological differentiation after serum withdrawal, whereas N2A cells overexpressing this gene extend long neurites, even in the presence of serum. We also show that NGFI-A overexpression is accompanied by an increase in the amount of phosphorylated microtubule-associated protein MAP1B, which has been associated with neurite outgrowth. Our results suggest that the NGFI-A gene plays an important role in neurite extension.

Up-regulated cytoplasmic expression, with reduced membranous distribution, of the src substrate p120(ctn) in gastric carcinoma

p120(ctn) is a substrate of the tyrosine kinase pp60 src. Tyrosine kinases such as src localize to the adherens junctions and phosphorylate junctional proteins in both normal and transformed cells.(1) p120(ctn) forms a complex with E-cadherin at the adherens junction and is phosphorylated by ligands such as epidermal growth factor receptor as well as pp60 src. Phosphorylation of p120(ctn) has been shown to correlate with cell transformation. The aim of this study was to investigate in vivo expression of p120(ctn) in gastric carcinoma and to examine any relationship to pathological characteristics and patient survival. Immunohistochemical staining for p120(ctn) was performed in 68 gastric carcinoma specimens (19 diffuse, 49 intestinal type), in 22 lymph node metastases, and in gastric mucosal biopsies from 16 patients with gastric dysplasia and ten healthy controls. Up-regulation of p120(ctn) cytoplasmic staining was seen in six (37 per cent) of the gastric dysplasia cases and in 45 (66 per cent) tumours (89 per cent of diffuse and 57 per cent of intestinal tumours). Loss of membranous distribution of staining for p120(ctn) was seen in 22 (32 per cent) tumours (52 per cent of diffuse and 24 per cent of intestinal tumours). The staining pattern in the primary tumour showed no correlation with tumour type, grade, or stage, or patient survival. Of 22 lymph node metastases examined, 13 (60 per cent) showed loss of membranous staining. In conclusion, staining for p120(ctn) in gastric carcinoma and dysplasia revealed marked up-regulation of cytoplasmic staining, sometimes associated with reduced membranous expression. Up-regulation of expression of p120(ctn) has not previously been described in human epithelial malignancy. The significance of these findings is uncertain, but they may reflect a change in tyrosine kinase signal transduction pathways, and a role for p120(ctn) in ligand-induced mitogenic signalling and cell transformation.

Expression patterns of the novel catenin p120cas in gastrointestinal cancers

p120cas is involved in signal transduction upon src or growth factor stimulation as well as in E-cadherin mediated cell adhesion and may play an important role in carcinogenesis. In this study, we evaluated immunohistochemically the expression and cellular localization of p120cas in 40 gastric, 43 colorectal and 20 pancreatic carcinomas, and examined the relationship between p120cas expression and pathological features. Altered p120cas expression was observed in 70%, 65% and 60% of gastric, colorectal and pancreatic cancers, respectively. The most common abnormality was of cytoplasmic expression associated with loss of membranous distribution found in 37% of gastric, in 25% of colorectal and in 25% of pancreatic cancers. Heterogeneous staining was noted in 15%, 19% and 20%, and complete loss of expression in 18%, 21% and 15% of gastric, colorectal and pancreatic cancers, respectively. There was no correlation between p120cas staining pattern and tumour grade or stage. Aberrant expression of p120cas which may reflect changes in signal transduction pathways occurs frequently in human malignancies.

beta-catenin expression in primary and metastatic colorectal carcinoma

beta-catenin plays a fundamental role in the regulation of the E-cadherin-catenin cell adhesion complex. It also functions in growth signalling events, independently of the cadherin-catenin complex, and these signalling pathways are disturbed in colorectal cancer. Mutations in either the APC or beta-catenin genes in colorectal cancer cells result in up-regulation of protein expression and subsequent cytoplasmic and nuclear distribution of beta-catenin. In this study, we examined beta-catenin expression in 47 primary colorectal tumors and the corresponding liver metastases. Immunohistochemical studies demonstrated loss of membranous beta-catenin expression in 26% of primary tumors and 60% of liver metastases and a concomitant increase in cytoplasmic and nuclear staining. Widespread nuclear expression of beta-catenin was found in 64% of primary tumors and 21% of liver metastases. No associations were found between any form of beta-catenin expression and either tumor stage or tumor grade. Cellular distribution of beta-catenin was also examined by detergent extraction and Western blot analysis in 16 primary tumors and 23 liver metastases. This analysis showed that most tumors demonstrated reduced beta-catenin in the cytoskeletal fraction and increased beta-catenin in the cytosolic fraction. Furthermore, 3 liver metastases were found to contain a truncated beta-catenin protein of approximately M(r) 80,000. Immunoprecipitation studies showed that the truncated beta-catenin proteins only bound weakly to E-cadherin and beta-catenin compared with non-truncated beta-catenin. These results demonstrate gross alterations in the cellular distribution of beta-catenin in primary colorectal cancers with metastatic potential, as well as in the metastatic tumors. These changes may be the consequence of APC or beta-catenin gene mutations, or possibly result from a post-translational modification of the E-cadherin-catenin complex.

A phase I/II study of hepatic artery infusion with wtp53-CMV-Ad in metastatic malignant liver tumours

Colorectal cancer (CRC) is the second commonest cause of cancer death in the UK, with greater than 40% of these patients destined to die of the disease despite current medical management. Death is commonly due to liver metastases with sequelae including progressive liver dysfunction. Most patients with liver metastases present with tumours that are unresectable and incurable with existing therapies. The median survival for CRC patients after diagnosis with liver metastases is approximately 6 months or less. The human p53 gene is a tumour suppressor gene involved in the control of cell proliferation. Loss of wild-type p53 function is associated with the uncontrolled growth of many types of human cancers. The reintroduction and expression of wild-type p53 into p53 altered tumour cells has been shown to suppress tumour growth or induce apoptosis in both in vitro and in vivo models. In our experience greater than 50% of CRC tumours have p53 alterations. This study seeks to evaluate the safety, biological efficacy and the effectiveness of wtp53-CMV-Ad treatment which is a recombinant adenoviral vector containing the wild-type human p53 gene. It will be administered by infusion via the hepatic artery, for the regional gene therapy of malignant liver tumours. Study patients will have incurable metastatic (CRC) malignant tumours of the liver with evidence of p53 alteration in their liver tumours. In vitro studies have demonstrated p53-specific antiproliferative effects of wtp53-CMV-Ad on human liver tumour cells and in vivo studies have demonstrated p53-specific antiproliferative effects on human liver tumour cells. The vector Ad-p53 is a recombinant, replication-defective adenovirus based on adenovirus serotype 5. It contains a sequence encoding wild-type p53 whose expression is under the control of the human cytomegalovirus immediate early promoter-enhancer. This construct will be growth in 293 cells which contain the adenoviral E1A and E1B coding sequences which have been removed from the vector to render it replication defective. The study design is an open-label, non-randomised, single-dose, dose escalation Phase I/II clinical trial anticipated to involve a maximum of 19 patients. wtp53-CMV-Ad will be administered by infusion in a reservoir connected to the hepatic artery, for regional gene therapy (surgically implanted pump) in 3 escalating doses to successive cohorts of 3 patients each until the maximum tolerated dose is determined. Subsequently, 10 patients will be treated with this dose. Regional wtp53-CMV-Ad therapy will be administered as a single bolus infusion via hepatic artery catheter. The route of administration of wtp53-CMV-Ad via hepatic artery infusion is designed to maximise gene therapy exposure to the malignant tumours while minimising exposure to normal tissues outside the liver. The clinical protocol is designed to monitor treatment toxicity. Another objective is to evaluate the biological efficacy, including efficiency and stability of gene transfer by analysis of tumour tissues following therapy. As an important part of this objective the pharmacokinetics of wtp53-CMV-Ad will be studied. Clinical evidence of anti-tumour efficacy will also be collected. In addition, the safety and efficacy of different doses levels of wtp53-CMV-Ad will be studied.

beta-catenin expression in primary and metastatic colorectal carcinoma

beta-catenin plays a fundamental role in the regulation of the E-cadherin-catenin cell adhesion complex. It also functions in growth signalling events, independently of the cadherin-catenin complex, and these signalling pathways are disturbed in colorectal cancer. Mutations in either the APC or beta-catenin genes in colorectal cancer cells result in up-regulation of protein expression and subsequent cytoplasmic and nuclear distribution of beta-catenin. In this study, we examined beta-catenin expression in 47 primary colorectal tumors and the corresponding liver metastases. Immunohistochemical studies demonstrated loss of membranous beta-catenin expression in 26% of primary tumors and 60% of liver metastases and a concomitant increase in cytoplasmic and nuclear staining. Widespread nuclear expression of beta-catenin was found in 64% of primary tumors and 21% of liver metastases. No associations were found between any form of beta-catenin expression and either tumor stage or tumor grade. Cellular distribution of beta-catenin was also examined by detergent extraction and Western blot analysis in 16 primary tumors and 23 liver metastases. This analysis showed that most tumors demonstrated reduced beta-catenin in the cytoskeletal fraction and increased beta-catenin in the cytosolic fraction. Furthermore, 3 liver metastases were found to contain a truncated beta-catenin protein of approximately M(r) 80,000. Immunoprecipitation studies showed that the truncated beta-catenin proteins only bound weakly to E-cadherin and beta-catenin compared with non-truncated beta-catenin. These results demonstrate gross alterations in the cellular distribution of beta-catenin in primary colorectal cancers with metastatic potential, as well as in the metastatic tumors. These changes may be the consequence of APC or beta-catenin gene mutations, or possibly result from a post-translational modification of the E-cadherin-catenin complex.

The E-cadherin/epidermal growth factor receptor interaction: a hypothesis of reciprocal and reversible control of intercellular adhesion and cell proliferation

The E-cadherin/catenin complex is a calcium-dependent cell-cell adhesion molecule, whose function is critical to the integrity of the adherens junction and which plays a role in the establishment and maintenance of normal epithelial morphology and differentiation. Loss of E-cadherin-mediated adhesion appears to be a fundamental aspect of the neoplastic phenotype which in some cases appears to be mediated by post-translational modifications (i.e. tyrosine phosphorylation) of its interacting proteins, the catenins which link E-cadherin to the actin cytoskeleton. There is increasing experimental evidence to suggest that epidermal growth factor receptor tyrosine phosphorylation may lead to the inactivation of the E-cadherin/catenin complex in cancer cells through its interaction with beta- or gamma-catenin in the cytoskeleton. Modulation of epidermal growth factor receptor activity by pharmacological agents has the potential to regulate a variety of cellular processes including adhesion, differentiation, and proliferation.

The E-cadherin/epidermal growth factor receptor interaction: a hypothesis of reciprocal and reversible control of intercellular adhesion and cell proliferation

The E-cadherin/catenin complex is a calcium-dependent cell-cell adhesion molecule, whose function is critical to the integrity of the adherens junction and which plays a role in the establishment and maintenance of normal epithelial morphology and differentiation. Loss of E-cadherin-mediated adhesion appears to be a fundamental aspect of the neoplastic phenotype which in some cases appears to be mediated by post-translational modifications (i.e. tyrosine phosphorylation) of its interacting proteins, the catenins which link E-cadherin to the actin cytoskeleton. There is increasing experimental evidence to suggest that epidermal growth factor receptor tyrosine phosphorylation may lead to the inactivation of the E-cadherin/catenin complex in cancer cells through its interaction with beta- or gamma-catenin in the cytoskeleton. Modulation of epidermal growth factor receptor activity by pharmacological agents has the potential to regulate a variety of cellular processes including adhesion, differentiation, and proliferation.

Cadherin-catenin expression in primary colorectal cancer: a survival analysis

Both cell adhesion and cell signalling events are mediated by components of the cadherin-catenin complex. Loss of expression of the components of this complex have been shown to correlate with invasive behaviour in many tumour types although their exact role in colorectal cancer remains unclear. Immunohistochemical analysis of the expression of components of the cadherin-catenin complex in colorectal cancers from 60 patients was undertaken. Loss of memberanous expression of E-cadherin, alpha-catenin and beta-catenin was demonstrated in 52%, 85% and 40% of tumours respectively. Focal nuclear expression of beta-catenin (< 75% of cells per section), usually associated with cytoplasmic expression, was clearly demonstrated in 19 (32%) tumours while widespread nuclear expression (> 75% of tumour cells per section) was seen in 11 (18%) tumours. Loss of membranous alpha-catenin expression significantly correlated with tumour de-differentiation (P = 0.009). There was a trend towards an association between advanced tumour stage and loss of membranous expression of alpha-catenin or beta-catenin, although these associations were not statistically significant. Univariate analysis revealed that advanced Dukes' stage, tumour de-differentiation, loss of membranous beta-catenin expression, cytoplasmic beta-catenin expression and widespread nuclear expression of beta-catenin all correlated with short survival following apparently curative resection of the primary tumour. However, only Dukes' stage (P = 0.002), tumour grade (P = 0.02) and widespread nuclear expression of beta-catenin (P = 0.002) were independent predictors of short survival. Disturbed growth signalling events in colorectal tumours are thought to result in nuclear accumulation of beta-catenin. Consequently, tumours with widespread nuclear expression of beta-catenin are likely to have severely abnormal growth characteristics, and which therefore might be predictive of short survival in these patients.

Characterization of the E-cadherin-catenin complexes in pancreatic carcinoma cell lines

E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenins play important roles in cell adhesion and signal transduction, as well as in maintenance of the structural and functional organization of polarized epithelial cells. In this study, the expression, distribution, and complex assembly of catenins with E-cadherin was analysed at the steady state in a panel of human pancreatic adenocarcinoma cell lines (BxPc3, HPAF, T3M4, and PaTuII cell lines). The expression and subcellular distribution were determined by western blotting and immunocytochemistry. Co-immunoprecipitation and cross-linking studies were performed to examine the complex assembly in both Triton X-100 (TX-100)-soluble and -insoluble fractions. In BxPc3 and T3M4 cells, E-cadherin exists in two complexes, one with alpha- and gamma-catenin, and the other with beta-catenin alone. In HPAF cells there are two complexes, one consisting of E-cadherin with alpha- and beta-catenin, and another of E-cadherin with gamma-catenin. In PaTuII cells, there is only a single complex of E-cadherin with alpha-catenin and gamma-catenin. Modification of E-cadherin-catenin complexes in HPAF and PaTuII cells was associated with loss of membranous E-cadherin immunolocalization. The common denominator is impaired beta-catenin association with either E-cadherin (PaTuII) or alpha-catenin (BxPc3 and T3M4). This may suggest the presence of distinct mechanisms that modulate the assembly of each complex, which could disturb the tumour suppressor function of E-cadherin and the catenins.

Vicia faba agglutinin, the lectin present in broad beans, stimulates differentiation of undifferentiated colon cancer cells

BACKGROUND

Dietary lectins can alter the proliferation of colonic cells. Differentiation is regulated by adhesion molecules which, being glycosylated, are targets for lectin binding.

AIMS

To examine the effects of dietary lectins on differentiation, adhesion, and proliferation of colorectal cancer cells.

METHODS

Differentiation was assessed in three dimensional gels, adhesion by aggregation assay, and proliferation by 3H thymidine incorporation. The role of the epithelial cell adhesion molecule (epCAM) was studied using a specific monoclonal antibody in blocking studies and Western blots. The human colon cancer cell lines LS174T, SW1222, and HT29 were studied.

RESULTS

The cell line LS174T differentiated in the presence of Vicia faba agglutinin (VFA) into gland like structures. This was inhibited by anti-epCAM monoclonal antibody. Expression of epCAM itself was unaffected. VFA as well as wheat germ agglutinin (WGA) and the edible mushroom lectin (Agaricus bisporus lectin, ABL) significantly aggregated LS174T cells but peanut agglutinin (PNA) and soybean agglutinin (SBA) did not. All lectins aggregated SW1222 and HT29 cells. Aggregation was blocked by the corresponding sugars. Aggregation of cells by VFA was also inhibited by anti-epCAM. VFA, ABL, and WGL inhibited proliferation of all the cell lines; PNA stimulated proliferation of HT29 and SW1222 cells. In competition studies all sugars blocked aggregation and proliferation of all cell lines, except that the addition of mannose alone inhibited proliferation.

CONCLUSION

VFA stimulated an undifferentiated colon cancer cell line to differentiate into gland like structures. The adhesion molecule epCAM is involved in this. Dietary or therapeutic VFA may slow progression of colon cancer.

Gastrointestinal responses to a panel of lectins in rats maintained on total parenteral nutrition

Total parenteral nutrition (TPN) causes atrophy of gastrointestinal epithelia, so we asked whether lectins that stimulate epithelial proliferation can reverse this effect of TPN. Two lectins stimulate pancreatic proliferation by releasing CCK, so we asked whether lectins that stimulate gastrointestinal proliferation also release hormones that might mediate their effects. Six rats per group received continuous infusion of TPN and a once daily bolus dose of purified lectin (25 mg. rat-1. day-1) or vehicle alone (control group) for 4 days via an intragastric cannula. Proliferation rates were estimated by metaphase arrest, and hormones were measured by RIAs. Phytohemagglutinin (PHA) increased proliferation by 90% in the gastric fundus (P < 0.05), doubled proliferation in the small intestine (P < 0.001), and had a small effect in the midcolon (P < 0.05). Peanut agglutinin (PNA) had a minor trophic effect in the proximal small intestine (P < 0.05) and increased proliferation by 166% in the proximal colon (P < 0.001) and by 40% in the midcolon (P < 0.001). PNA elevated circulating gastrin and CCK by 97 (P < 0.05) and 81% (P < 0.01), respectively, and PHA elevated plasma enteroglucagon by 69% and CCK by 60% (both P < 0.05). Only wheat germ agglutinin increased the release of glucagon-like peptide-1 by 100% (P < 0.05). PHA and PNA consistently reverse the fall in gastrointestinal and pancreatic growth associated with TPN in rats. Both lectins stimulated the release of specific hormones that may have been responsible for the trophic effects. It is suggested that lectins could be used to prevent gastrointestinal atrophy during TPN. Their hormone-releasing effects might be involved.

Abnormal expression and function of the E-cadherin-catenin complex in gastric carcinoma cell lines

Dysfunction of the cadherin-catenin complex, a key component of adherens junctions, is thought to confer invasive potential to cells. The aim of this study is to examine the expression and function of the E-cadherin/catenin complex in gastric carcinoma cell lines. Expression of E-cadherin, alpha, beta and gamma-catenin and p120ctn, and of the adenomatous polyposis coli protein (APC), together with function of the cadherin-catenin complex was examined in a panel of gastric carcinoma cell lines, using immunocytochemistry, Western blotting and a cell-cell aggregation assay. Protein interactions were examined by sequential immunoprecipitation and immunoblotting with antibodies to E-cadherin, alpha, beta and gamma-catenin, p120ctn and APC. Abnormalities of E-cadherin, alpha- and beta-catenin expression, were associated with disturbance of E-cadherin-catenin complex composition, loss of membranous localization and loss of calcium-dependent aggregation in six gastric carcinoma cell lines. APC protein expression and interaction with beta-catenin was preserved in five cell lines. We demonstrate frequent abnormalities of expression and function of E-cadherin and catenins, and associated disturbance of E-cadherin-mediated intercellular adhesion in gastric carcinoma cell lines. These findings support the tumour suppressor role of the E-cadherin and its contribution to the development and progression of the neoplastic phenotype in gastric carcinoma.

Clinical short-term results of radiofrequency ablation in primary and secondary liver tumors

BACKGROUND

Radiofrequency ablation (RFA) is emerging as a new therapeutic method for management of solid tumors. We report here our experience in the use of this technique for management of primary and secondary unresectable liver cancers.

METHODS

Thirty-five patients with liver cancers were considered not suitable for curative resection at presentation: 8 with primary hepatocellular carcinoma ([HCC] 6 HCC and 2 fibrolamellar); 27 with metastatic liver cancer (17 colorectal carcinoma and 10 others). They were treated either with radiofrequency heat ablation (Radionics Europe N.V., Wettdren, Belgium) alone percutaneously and/or intraoperatively or in conjunction with surgical resections. The quality of RFA was based on the subjective feeling of whether the tumor was completely destroyed or not. The effectiveness of RFA was assessed according to clinical findings, radiographic images, and tumor markers at follow-up.

RESULTS

In 8 primary liver cases, 4 patients with a high level of alpha fetoprotein (AFP) benefited from the RFA with a 83.3% to 99.7% reduction of AFP. One with fibrolamellar hepatocellular carcinoma died 2 months after an incomplete percutaneous RFA from recurrence. The rest all had stable disease at the time of follow-up (mean 10.4 months). In patients with colorectal liver metastases, there were 4 deaths: 1 patient died postoperatively on the 30th day from a severe chest infection having shown a considerable reduction of carcinoembryonic antigen level (CEA, 8 versus 36 microg/L); 3 died from local and systemic disease, 1 at 12 months and 2 at 1 month, having had an incomplete RFA. The others had stable disease at follow-up (mean 7.6 months). Five patients underwent liver resections successfully with the application of RFA for residual lesions in the remaining contralateral lobe. In 10 patients with other liver tumors, 7 patients had stable disease at follow-up (mean 13.4 months); 1 patient had evidence of local and systemic recurrence 10 months after surgical resections with the intraoperative RFA and 2 patients died of systemic recurrence of disease 3 and 6 months after RFA alone. Two patients had liver resections in conjunction with the intraoperative RFA. The mean follow-up in our series was 8.5 months.

CONCLUSION

Radiofrequency heat ablation is useful as a primary treatment for unresectable liver cancers. The procedure can be used to treat the small residual tumor load in the contralateral lobe following liver resection in those considered unresectable at the first presentation. This new therapeutic strategy seems to increase surgical resectability in patients judged unresectable.

Mutated epithelial cadherin is associated with increased tumorigenicity and loss of adhesion and of responsiveness to the motogenic trefoil factor 2 in colon carcinoma cells

Epithelial (E)-cadherin and its associated cytoplasmic proteins (alpha-, beta-, and gamma-catenins) are important mediators of epithelial cell-cell adhesion and intracellular signaling. Much evidence exists suggesting a tumor/invasion suppressor role for E-cadherin, and loss of expression, as well as mutations, has been described in a number of epithelial cancers. To investigate whether E-cadherin gene (CDH1) mutations occur in colorectal cancer, we screened 49 human colon carcinoma cell lines from 43 patients by single-strand conformation polymorphism (SSCP) analysis and direct sequencing. In addition to silent changes, polymorphisms, and intronic variants in a number of the cell lines, we detected frameshift single-base deletions in repeat regions of exon 3 (codons 120 and 126) causing premature truncations at codon 216 in four replication-error-positive (RER+) cell lines (LS174T, HCT116, GP2d, and GP5d) derived from 3 patients. In LS174T such a mutation inevitably contributes to its lack of E-cadherin protein expression and function. Transfection of full-length E-cadherin cDNA into LS174T cells enhanced intercellular adhesion, induced differentiation, retarded proliferation, inhibited tumorigenicity, and restored responsiveness to the migratory effects induced by the motogenic trefoil factor 2 (human spasmolytic polypeptide). These results indicate that, although inactivating E-cadherin mutations occur relatively infrequently in colorectal cancer cell lines overall (3/43 = 7%), they are more common in cells with an RER+ phenotype (3/10 = 30%) and may contribute to the dysfunction of the E-cadherin-catenin-mediated adhesion/signaling system commonly seen in these tumors. These results also indicate that normal E-cadherin-mediated cell adhesion can restore the ability of colonic tumor cells to respond to trefoil factor 2.

E-cadherin and catenins: molecules with versatile roles in normal and neoplastic epithelial cell biology

E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenin, play a crucial role in epithelial cell-cell adhesion and in the maintenance of tissue architecture. Perturbation in the expression or function of any of these molecules results in loss of intercellular adhesion, with possible consequent cell transformation and tumour progression. The catenins are connected to many structural and functional proteins, which in turn influence their functions. Among these molecules are type 1 growth factor receptors, which along with other molecules are believed to alter the function of catenins through tyrosine phosphorylation. A recent finding is the association between the catenins and the adenomatous polyposis coli gene product (APC). APC mutation is an early event in colorectal carcinogenesis. It may possibly do so through perturbation of the critical cadherin/catenin complex. Further studies of the cadherin/catenin complex and its connections may give insight into the early molecular interactions critical to the initiation and progression oftumours, which should aid in the development of novel therapeutic strategies for both prevention and treatment.

Role of adhesion molecules in bladder cancer: an important part of the jigsaw

There is a growing body of evidence suggesting that alterations in the adhesion properties of neoplastic cells may play a pivotal role in the development and progression of bladder cancer. Loss of intercellular adhesion and the desquamation of cells from the underlying lamina propria allows malignant cells to escape from their site of origin, degrade the extracellular matrix, acquire a more motile and invasive phenotype, and finally invade and metastasize. In addition to participating in tumor invasiveness and metastasis, adhesion molecules regulate or significantly contribute to a variety of functions, including signal transduction, cell growth, differentiation, site-specific gene expression, morphogenesis, immunologic function, cell motility, wound healing, and inflammation. To date, a diverse system of transmembrane glycoproteins have been identified that mediate the cell-cell and the cell-extracellular matrix adhesion. The main families of adhesion molecules are the cadherins, integrins, members of the immunoglobulin superfamily, and selectins. We review the recent data regarding the role of selected adhesion molecules in the pathogenesis of bladder cancer and their clinical exploitation as biomarkers of this malignant disease.

The E-cadherin/epidermal growth factor receptor interaction: a hypothesis of reciprocal and reversible control of intercellular adhesion and cell proliferation

The E-cadherin/catenin complex is a calcium-dependent cell-cell adhesion molecule, whose function is critical to the integrity of the adherens junction and which plays a role in the establishment and maintenance of normal epithelial morphology and differentiation. Loss of E-cadherin-mediated adhesion appears to be a fundamental aspect of the neoplastic phenotype which in some cases appears to be mediated by post-translational modifications (i.e. tyrosine phosphorylation) of its interacting proteins, the catenins which link E-cadherin to the actin cytoskeleton. There is increasing experimental evidence to suggest that epidermal growth factor receptor tyrosine phosphorylation may lead to the inactivation of the E-cadherin/catenin complex in cancer cells through its interaction with beta- or gamma-catenin in the cytoskeleton. Modulation of epidermal growth factor receptor activity by pharmacological agents has the potential to regulate a variety of cellular processes including adhesion, differentiation, and proliferation.

Expression of catenins and E-cadherin during epithelial restitution in inflammatory bowel disease

Catenins are cytoplasmic proteins associated with E-cadherin, the prime mediator of cell-cell adhesion. Perturbation in any of these molecules results in altered intercellular adhesion, cell differentiation, and increased migration. In this study, the expression and cellular localization of catenins and E-cadherin in inflammatory bowel disease were examined. The expression of E-cadherin; alpha-, beta-, and gamma-catenin; and p120 was evaluated immunohistochemically in 31 paraffin-embedded colonic specimens from 21 patients with ulcerative colitis and Crohn's disease. Loss of normal membranous E-cadherin and alpha-catenin staining was detected at the mucosal edges around epithelial ulcerations in all cases of active ulcerative colitis and in 50 per cent of cases with active Crohn's disease. Reduced expression of p120 protein was also found at the margins of ulcerated mucosa in all cases of active ulcerative colitis and in 75 per cent of those with active Crohn's disease. There was a statistically significant correlation between the expression of E-cadherin, alpha-catenin and p120 and disease activity. There were no changes in beta- and gamma-catenin expression in either ulcerative colitis on Crohn's disease. These findings indicate that altered expression of E-cadherin, alpha-catenin, and p120 occurs during mucosal ulceration in inflammatory bowel disease. These changes may be involved in promoting cell migration during epithelial restitution of the gastrointestinal mucosa.

E-cadherin/catenin complex in benign and malignant melanocytic lesions

E-cadherin is a calcium-dependent cell-cell adhesion molecule expressed by melanocytes and responsible for their adhesion to keratinocytes in vitro. In this study, the expression of E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenin was evaluated in melanocytic lesions by immunohistochemistry. E-cadherin expression was evaluated in 70 malignant melanomas and the catenins in 35 of these specimens. Twenty benign melanocytic naevi were also evaluated for E-cadherin and catenin expression. In normal epidermis, E-cadherin/catenin immunostaining was localized at the intercellular borders. In melanomas, a differential loss of E-cadherin expression was observed. Membranous E-cadherin staining was absent in dermal nests of melanomas in their radial growth phase and in Clark level II and III lesions, whereas it was present in a high proportion of melanomas in their vertical growth phase, in Clark level IV and V lesions and in metastasizing melanomas. In contrast, superficial compartments of naevi showed membranous E-cadherin immunoreactivity and junctional naevus cell nests displayed heterogeneous or diffuse cytoplasmic staining. Cytoplasmic alpha- and beta-catenin, but not gamma-catenin staining were detected in all benign and malignant lesions. These findings indicate that qualitative changes in the expression and cellular localization of E-cadherin and of alpha-, beta-, and gamma-catenin occur in melanocytic lesions and may reflect different stages in their progression.

Abnormal expression of p120 correlates with poor survival in patients with bladder cancer

p120 is a cytoplasmic molecule closely associated with the Ca(2+)-dependent cell-cell adhesion molecule E-cadherin, by forming complexes between the cytoplasmic domain of E-cadherin and the cytoskeleton. Although it has been shown that loss or downregulation of E-cadherin is associated with an invasive and poorly differentiated phenotype in several tumours, there is very little information available concerning p120 expression in malignant disease. We used an avidin-biotin immunoperoxidase technique to examine the immunoreactivity and cellular localisation of p120 and E-cadherin in 68 transitional cell carcinomas (TCC) and 14 normal bladder biopsies and correlated these results with pathological and clinical parameters. E-cadherin and p120 were expressed in a normal membranous pattern in all normal bladder epithelium specimens. Loss of normal surface E-cadherin and p120 expression was found in 52/68 (76%) and 57/68 (84%) tumours, respectively. There was a significant correlation between the loss of normal membranous expression of p120 and increased grade (P < 0.001) and T stage (P < 0.001). The abnormal expression of p120 was correlated with poor survival (P < 0.05). Our data indicate that the E-cadherin-p120 complex may be a useful prognostic marker in bladder cancer.

Altered gamma-catenin expression correlates with poor survival in patients with bladder cancer

PURPOSE

We studied the expression of alpha-, beta-, gamma- catenin and E-cadherin in transitional cell carcinoma (TCC) and normal bladder epithelium and correlated these results with pathological and clinical parameters.

MATERIALS AND METHODS

We used an avidin-biotin immunoperoxidase technique to examine the cellular localization of alpha-catenin, beta-catenin, gamma-catenin and E-cadherin in 68 TCC and 14 normal bladder biopsies.

RESULTS

E-cadherin, alpha-catenin, beta-catenin and gamma-catenin were expressed in a normal membranous pattern in all normal bladder epithelium specimens. Loss of normal surface E-cadherin, alpha-catenin, beta-catenin and gamma-catenin expression was found in 52/68 (76.4%) tumors, 57/68 (83.8%) tumors, 54/68 (79.4%) tumors and 54/68 (79.4%) tumors (p <0.001). There was a significant correlation between the loss of normal membranous expression of catenins and E-cadherin and increased grade (p <0.05). A highly significant correlation was observed between the loss of expression of E-cadherin, alpha-catenin and gamma-catenin, but not beta-catenin, with increased TNM stage (p <0.05). The abnormal expression of gamma-catenin as well as E-cadherin was correlated with poor survival (p <0.05).

CONCLUSIONS

E-cadherin-gamma-catenin complex may be a useful prognostic marker in bladder cancer. Work is in progress to establish whether normal membranous catenin expression can be enhanced by gene transfer or biological therapy to induce a less invasive and metastatic phenotype.

E-cadherin and catenins: molecules with versatile roles in normal and neoplastic epithelial cell biology

E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenin, play a crucial role in epithelial cell-cell adhesion and in the maintenance of tissue architecture. Perturbation in the expression or function of any of these molecules results in loss of intercellular adhesion, with possible consequent cell transformation and tumour progression. The catenins are connected to many structural and functional proteins, which in turn influence their functions. Among these molecules are type 1 growth factor receptors, which along with other molecules are believed to alter the function of catenins through tyrosine phosphorylation. A recent finding is the association between the catenins and the adenomatous polyposis coli gene product (APC). APC mutation is an early event in colorectal carcinogenesis. It may possibly do so through perturbation of the critical cadherin/catenin complex. Further studies of the cadherin/catenin complex and its connections may give insight into the early molecular interactions critical to the initiation and progression oftumours, which should aid in the development of novel therapeutic strategies for both prevention and treatment.