Integrins, cadherins, and catenins: molecular cross-talk in cancer cells

In the past decade, there have been major advances in the understanding of some of the mechanisms underlying tumour differentiation, invasion, and metastasis, in which cell-cell and cell-matrix adhesion molecules play a critical role. Cadherin/catenin complex and the integrins are the prime mediators of cell adhesion in normal and transformed cells, cadherin/catenin being largely responsible for intercellular adhesion and integrins for cell-extracellular matrix interactions. Intercellular and cell-matrix adhesion mediated by cadherin/catenin and integrins is likely to play a role in the control of both structural morphology and functional differentiation; hence, any loss of this control mechanism may well facilitate the neoplastic process. Indeed, in cancer cells, there is a co-ordinated down-regulation of both integrins and cadherins which correlates with tumour dedifferentiation. However, the expression and cellular localization of catenins do not always correlate with cadherin expression, since the catenins are rather promiscuous molecules which interact not only with E-cadherin, but also with growth regulatory and signalling molecules such as epidermal growth factor receptor and the adenomatous polyposis coli gene product.

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.

Intestinal trefoil factor controls the expression of the adenomatous polyposis coli-catenin and the E-cadherin-catenin complexes in human colon carcinoma cells

Intestinal trefoil factor 3 (TFF3) is a member of the trefoil family of peptides, small molecules constitutively expressed in epithelial tissues, including the gastrointestinal tract. TFF3 has been shown to promote migration of intestinal epithelial cells in vitro and to enhance mucosal healing and epithelial restitution in vivo. In this study, we evaluated the effect of recombinant TFF3 (rTFF3) stimulation on the expression and cellular localization of the epithelial (E)-cadherin-catenin complex, a prime mediator of Ca2+ dependent cell-cell adhesion, and the adenomatous polyposis coli (APC)-catenin complex in HT29, HCT116, and SW480 colorectal carcinoma cell lines. Stimulation by rTFF3 (10(-9) M and 10(-8) M) for 20-24 hr led to cell detachment and to a reduction in intercellular adhesion in HT29 and HCT116 cells. In both cell lines, E-cadherin expression was down-regulated. The expression of APC, alpha-catenin and beta-catenin also was decreased in HT29 cells, with a translocation of APC into the nucleus. No change in either cell adhesion or in the expression of E-cadherin, the catenins, and APC was detected in SW480 cells. In addition, TFF3 induced DNA fragmentation and morphological changes characteristic of apoptosis in HT29. Tyrphostin, a competitive inhibitor of protein tyrosine kinases, inhibited the effects of TFF3. Our results indicate that by perturbing the complexes between E-cadherin, beta-catenin, and associated proteins, TFF3 may modulate epithelial cell adhesion, migration, and survival.

Expression of fibroblast growth factor 2 mRNA in early and advanced gastric cancer

We examined the expression of FGF-2 mRNA in 16 early and 14 advanced gastric cancer by in situ hybridisation to elucidate its role in cancer progression. Anti-sense RNA probes were synthesized by transcribing the subcloned vector with T7 RNA polymerase in the presence of digoxigenin-labeled UTP. FGF-2 mRNA was located mainly in the cytoplasm around the nuclei of endothelial cells, fibroblasts and carcinoma cells. The expression was more frequently in the diffuse type carcinomas (4/7, 57%) than in the intestinal type tumours (5/23, 22%). The survival rates of advanced gastric cancers with FGF-2 mRNA expression were significantly lower than those without FGF-2 mRNA expression (p < 0.01). No significant correlation was seen with other clinicopathological factors. These results suggest that FGF-2 may play an important role for the growth of diffuse type gastric cancers, particularly at their advanced stage.

p53 mutation is a poor prognostic indicator for survival in patients with hepatocellular carcinoma undergoing surgical tumour ablation

Forty-two patients with hepatocellular carcinoma (HCC) were resected and their tumours were analysed for p53 mutations by GC-clamped denaturing gradient gel electrophoresis (DGGE), single-strand conformation polymorphism (SSCP) and gene sequencing. All the exons have been analysed in this study. Eight of 12 HCCs with cirrhosis due to viral hepatitis and the two patients with sarcomatoid changes displayed p53 mutations. In contrast, no mutation was observed in the fibrolamellar variant (n = 9), non-cirrhotics (n = 13) and alcoholic cirrhosis (n = 6). The mutations observed were in exons 5-8. Two mutations were observed in codons 136 and 213 as well as a T insertion between residues 156 and 157 (exon 5) and these are reported for the first time in HCC. Likewise, the silent mutation polymorphism in codon 213 was noticed in 3 of the 42 patients. Survival analysis of these patients after surgery showed the mean and median survival in patients with wild-type p53 to be 60 and 43 months respectively. In the group with p53 mutations, the mean and median survival was 15 and 12 months. The difference was statistically significant (P= 0.003).

Phosphorylation of beta-catenin and epidermal growth factor receptor by intestinal trefoil factor

Intestinal trefoil factor (TFF3) is a member of the trefoil family of peptides, which are constitutively expressed in the gastrointestinal tract. TFF3 has been shown to promote migration of intestinal epithelial cells in vitro and to enhance epithelial restitution in vivo. In the present study, we show that the stimulatory effect of TFF3 on the migration of HT29 colonic carcinoma cells requires the perturbation of E-cadherin function, a calcium-dependent cell-cell adhesion molecule in epithelia. A rapid (< 1 minute) and specific tyrosine phosphorylation of beta-catenin and epidermal growth factor receptor was detected in cells treated with recombinant rat TFF3. No phosphorylation of E-cadherin or alpha-catenin was detected. Tyrosine phosphorylation of beta-catenin was associated with reduced membranous E-cadherin expression, perturbation of intercellular adhesion, and promotion of cell motility. These results suggest that TFF3 enhances cell migration through modulation of E-cadherin/catenin complex function. Tyrosine phosphorylation of beta-catenin and epidermal growth factor receptor seems to be involved in this process.

Wild-type p53 induces apoptosis in Hep3B through up-regulation of bax expression

We demonstrated that introduction and expression of wild-type p53 gene in the human hepatocellular carcinoma cell line, Hep3B, resulted in up-regulation of both p21WAF1/CIP1 and bax gene expression and apoptosis. This cell line contains integrated hepatitis B virus sequences and lacks the expression of both p53 and retinoblastoma tumor suppressor genes because of deletions. Our results suggest that whereas an increased level of bax expression mediates apoptosis, an increased level of p21WAF1/CIP1 expression does not induce arrest of cell growth, presumably because of the deletion of the retinoblastoma gene. This study also confirms reported observations that p53 is a tumor suppressor gene, which induces apoptosis in malignant cells that lack normal p53 activity because of mutation, deletion, or inactivation of the gene by the presence of oncogenic viral proteins.

Beta-catenin mutations in cell lines established from human colorectal cancers

beta-catenin has functions as both an adhesion and a signaling molecule. Disruption of these functions through mutations of the beta-catenin gene (CTNNB1) may be important in the development of colorectal tumors. We examined the entire coding sequence of beta-catenin by reverse transcriptase-PCR (RT-PCR) and direct sequencing of 23 human colorectal cancer cell lines from 21 patients. In two cell lines, there was apparent instability of the beta-catenin mRNA. Five different mutations (26%) were found in the remaining 21cell lines (from 19 patients). A three-base deletion (codon 45) was identified in the cell line HCT 116, whereas cell lines SW 48, HCA 46, CACO 2, and Colo 201 each contained single-base missense mutations (codons 33, 183, 245, and 287, respectively). All 23 cell lines had full-length beta-catenin protein that was detectable by Western blotting and that coprecipitated with E-cadherin. In three of the cell lines with CTNNB1 mutations, complexes of beta-catenin with alpha-catenin and APC were detectable. In SW48 and HCA 46, however, we did not detect complexes of beta-catenin protein with alpha-catenin and APC, respectively. These results show that selection of CTNNB1 mutations occurs in up to 26% of colorectal cancers from which cell lines are derived. In these cases, mutation selection is probably for altered beta-catenin function, which may significantly alter intracellular signaling and intercellular adhesion and may serve as a complement to APC mutations in the early stages of tumorigenesis.

Aberrant E-cadherin and alpha-catenin expression in prostate cancer: correlation with patient survival

E-cadherin maintains the normal differentiated phenotype in epithelial cells; this function is partly mediated by alpha-catenin, which links E-cadherin to the cell cytoskeleton. Dysfunction of E-cadherin in vitro and in vivo is associated with an invasive phenotype. However, the role of alpha-catenin is largely undetermined. We analyzed the expression of E-cadherin and alpha-catenin in prostate cancer to assess the relationship of abnormal expression to stage, grade and survival. E-cadherin expression was evaluated in 99 prostate cancers. In 79 of those specimens, alpha-catenin was also assessed. In benign prostatic epithelium, both E-cadherin and alpha-catenin were expressed uniformly at the cell membrane. Abnormal E-cadherin expression was found in 56% of cancer specimens, whereas alpha-catenin expression was abnormal in 42%. Abnormal expression of each molecule was significantly correlated with Gleason score (P < 0.0001) and the ratio of resection chippings infiltrated by tumor (P < 0.0001). E-cadherin expression was also associated with the extent of disease on the initial bone scan (P = 0.017). Univariate analysis showed significantly lower survival rate for patients with abnormal E-cadherin (P = 0.0003) or alpha-catenin expression (P = 0.031). Multivariate regression analysis showed that the prognostic value of E-cadherin was independent of tumor grade but not of metastasis. These results suggest that perturbation of cell-cell adhesion is involved in the progression of prostate cancer and that analysis of E-cadherin expression may be clinically useful.

Inhibition of growth and enhancement of differentiation of colorectal carcinoma cell lines by MAb MR6 and IL-4

We have previously shown that expression of gp200-MR6, a molecule that is functionally associated with the interleukin-4 receptor (IL-4R), is lost from breast carcinoma cells as malignancy increases. Here we have analysed a series of colorectal carcinoma cell lines and show a similar decrease with increasing malignancy. Moreover, analysis of the HRA-19 cell line, which can exhibit a poorly or a well-differentiated phenotype according to culture conditions, shows that gp200-MR6 is weakly expressed on the former but strongly expressed on the latter. Functional analysis using either IL-4 or monoclonal antibody (MAb) MR6 and the well-differentiated cell line SW1222 revealed that MAb MR6 acts as an agonist for IL-4, with both reagents causing a dose-dependent inhibition of cell division, but greatly enhancing the glandular differentiation of SW1222 in three-dimensional collagen gels. These observations suggest that the gp200-MR6 molecule may act as the product of a tumour suppressor gene and that its loss may be a primary event in tumourigenesis.

Expression of E-cadherin-associated molecules (alpha-, beta-, and gamma-catenins and p120) in colorectal polyps

E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenin and p120 protein play a crucial role in the maintenance of normal tissue architecture. Perturbation in any of these molecules results in loss of intercellular adhesion and cell transformation. In this study, we have used immunohistochemistry to localize E-cadherin, alpha-, beta-, and gamma-catenin, and p120 in paraffin-embedded tissues from 60 patients with colonic polyps. Specimens consisted of 20 samples each from hyperplastic, inflammatory, and sporadic adenomatous polyps. Ten histologically normal colonic samples were also studied. Normal colonic epithelial cells showed strong E-cadherin/ catenin/p120 immunostaining at the cell-cell junction. In 65% (13/20) of adenomatous polyps, beta-catenin showed abnormal nuclear localization with increased expression and loss of membranous staining compared with the adjacent normal mucosa. In two cases (10%), gamma-catenin was seen in the nuclei. Heterogeneous p120 immunoreactivity was observed in four cases (20%), of which two also showed beta-catenin nuclear localization. Preserved membranous alpha-catenin staining was seen in all cases. E-cadherin was down-regulated in 6 of 20 (30%) adenomas with loss of cell surface staining in 3 cases. All hyperplastic and 40% (8/20) of inflammatory polyps showed weak E-cadherin expression on the surface epithelium. Similar changes in p120 expression were seen in all hyperplastic and 20% (4/20) of inflammatory polyps. There were no concomitant changes in alpha-, beta-, or gamma-catenin expression. These results indicate that changes in catenin expression and cellular localization occur early in dysplastic colonic lesions.

Possibilities and limitations of endoscopic resection for early gastric cancer

BACKGROUND AND STUDY AIMS

To date, the accepted criteria for endoscopic resection of early gastric cancer have been: a) elevated-type mucosal cancer less than 2 cm in size, and b) depressed-type mucosal cancer without ulceration less than 1 cm in size. In this study, we attempted to expand these indications.

PATIENTS AND METHODS

Sixty patients with early gastric cancer who did not meet the above criteria underwent endoscopic treatment, and were divided into four groups: those with elevated tumours larger than 2 cm with submucosal invasion (group 1 a); those without submucosal invasion (group 1 b); those with depressed tumours larger than 1 cm (group 2); and those with ulcerated tumours (group 3). The patients were treated with endoscopic resection using a two-channel scope, followed by additional laser irradiation or heater-probe coagulation (combination therapy) if residual cells were found. Follow-up was by endoscopy and biopsy for more than two years.

RESULTS

Endoscopic treatment was effective in 87% of the patients (52 of 60), half of whom required combination therapy. In submucosal cancers, endoscopic treatment was effective in 76% of patients (13 of 17). However, tumours with deep invasion into the submucosa could not be cured. Mucosal cancers larger than 20 mm could be completely resected in 44% of patients (eight of 18) using endoscopic resection, but all five patients with tumours larger than 30 mm had incomplete resections.

CONCLUSIONS

These results indicate that complete resection using endoscopic resection alone is possible in early gastric cancers measuring up to 30 mm in diameter. Tumours larger than 30 mm, and those with deep submucosal invasion, cannot be curatively treated by the current endoscopic modalities.

Inhibition of growth and enhancement of differentiation of colorectal carcinoma cell lines by MAb MR6 and IL-4

We have previously shown that expression of gp200-MR6, a molecule that is functionally associated with the interleukin-4 receptor (IL-4R), is lost from breast carcinoma cells as malignancy increases. Here we have analysed a series of colorectal carcinoma cell lines and show a similar decrease with increasing malignancy. Moreover, analysis of the HRA-19 cell line, which can exhibit a poorly or a well-differentiated phenotype according to culture conditions, shows that gp200-MR6 is weakly expressed on the former but strongly expressed on the latter. Functional analysis using either IL-4 or monoclonal antibody (MAb) MR6 and the well-differentiated cell line SW1222 revealed that MAb MR6 acts as an agonist for IL-4, with both reagents causing a dose-dependent inhibition of cell division, but greatly enhancing the glandular differentiation of SW1222 in three-dimensional collagen gels. These observations suggest that the gp200-MR6 molecule may act as the product of a tumour suppressor gene and that its loss may be a primary event in tumourigenesis.

Loss of E-cadherin expression associated with lymph node metastases in small breast carcinomas

The National Breast Screening Programme affords the opportunity to study breast carcinomas at an early stage in their development. E-cadherin is a calcium-dependent, intercellular adhesion molecule whose loss of expression may facilitate the processes of invasion and metastasis of some human tumours. From a group of screen-detected ductal carcinomas less than or equal to 10 mm in diameter, 16 with lymph node metastasis were identified and matched for grade, size and patient age with node negative tumours. The level of expression of E-cadherin (detected by immunocytochemistry) was compared in the matched pairs using a simple semi-quantitative intensity distribution scoring system. The results showed a significant (P = 0.05 Wilcoxon paired rank test) reduction of E-cadherin expression in tumours with lymph node metastases compared to those without. In the context of the small size of these tumours it is proposed that these results support the hypothesis that reduction in E-cadherin expression is an early event in the development of metastases.

Cytoplasmic antineutrophil cytoplasmic antibody-positive vasculitis associated with ulcerative colitis

The case of a man with poorly controlled ulcerative colitis, who developed a cytoplasmic antineutrophil cytoplasmic antibody-positive systemic vasculitis, causing small bowel infarction is reported. Antineutrophil cytoplasmic antibodies occur in 50-70% of patients with ulcerative colitis, but are usually of the perinuclear or atypical pattern; the cytoplasmic pattern seen in this case is indicative of systemic vasculitis. A variety of vasculitic diseases have been reported as occurring rarely with ulcerative colitis, but this report is the first description of a cytoplasmic antineutrophil cytoplasmic antibody-positive vasculitis with this association.

Abnormal immunoreactivity of the E-cadherin-catenin complex in gastric carcinoma: relationship with patient survival

BACKGROUND & AIMS

The E-cadherin-catenin complex plays a critical role in the maintenance of normal tissue architecture. Mutation of any of its components is believed to result in loss of cell-cell adhesion and contribute to neoplasia. The aim of this study was to examine the expression of E-cadherin and alpha-, beta-, and gamma-catenin in gastric carcinoma and dysplasia and determine any relationship with tumor characteristics and survival.

METHODS

Immunoperoxidase staining of E-cadherin and alpha-, beta-, and gamma-catenin was performed using 89 gastric carcinomas, lymph node metastases, and gastric biopsy specimens from 14 patients with dysplasia and 10 healthy controls.

RESULTS

Membranous staining was observed in control biopsy specimens for all components of the complex. Up to 57% of gastric dysplasia and 90% of tumors stained abnormally for one or more components of the cadherin-catenin complex. Abnormal E-cadherin and gamma-catenin staining occurred more frequently in diffuse than intestinal tumors (P < 0.0005 and < 0.05, respectively). No association with tumor grade or stage was found. A survival advantage was noted in intestinal and diffuse tumors retaining membranous expression of beta-catenin, independent of tumor type, grade, or stage (P < 0.005).

CONCLUSIONS

Abnormal expression of the E-cadherin-catenin complex occurs frequently in gastric carcinoma. The close correlation with poor survival suggests that abnormal beta-catenin may be a useful prognostic marker.

E-cadherin (E-cad) expression in duct carcinoma in situ (DCIS) of the breast

E-cadherin (E-cad) is an epithelial cell-cell adhesion molecule whose loss or reduced expression is associated with a more invasive tumour phenotype. Ninety-six cases of screen detected pure ductal carcinoma in situ (DCIS) were analysed immunocytochemically for expression of E-cad using the HECD-1 mouse monoclonal antibody. The in situ component in each case was classified on the basis of cytonuclear grade, extent of necrosis, Van Nuys classification and a newly devised Cardiff classification. The amount of E-cad expression was assessed semi-quantitatively using an intensity distribution method. There is significantly more expression of E-cad in well-differentiated DCIS when compared with poorly differentiated DCIS and this finding is highly significant (P < 0.001) irrespective of the classification system used. These findings suggest that progressive loss of E-cad expression may occur at an early stage of breast cancer development.

Fibroblast growth factor 1 and fibroblast growth factor 2 immunoreactivity in gastrointestinal tumours

Acidic and basic fibroblast growth factors (FGF-1 and FGF-2) are mitogenic polypeptides that may play a role in autocrine and paracrine growth control of malignant tumours. We have examined the expression of FGF-1 and FGF-2 in a series of 41 colorectal tumours (24 adenomas, 17 adenocarcinomas) and 50 gastric adenocarcinomas (23 intestinal, 27 diffuse), using immunohistochemistry. Whereas the FGF-1 distribution was cytoplasmic, FGF-2 was restricted to the nuclei of the epithelial cells. FGF-1 immunoreactivity was detected in all samples (100 per cent), whereas FGF-2 immunoreactivity was seen in 17 adenomas (71 per cent), 13 colorectal carcinomas (76 per cent), and 29 gastric carcinomas (58 per cent). Compared with the normal mucosa, FGF-1 was overexpressed in 42 per cent of colorectal adenomas, 76 per cent of colorectal cancers, and 54 per cent of gastric cancers. Conversely, FGF-2 expression was reduced in 16 (66 per cent), 8 (47 per cent), and 40 (80 per cent) adenomas and colorectal and gastric samples, respectively. We found a significant correlation only between reduced FGF-2 and gastric tumour grade. These data indicate that FGF-1 overexpression occurs in a large proportion of human colorectal and gastric cancers. This may play a role in the progression of these tumours. The topographic variation in FGF-2 expression between normal (nuclear) and tumour (cytoplasmic) cells implies a corresponding functional change that may in turn facilitate tumour growth.

E-cadherin transfection down-regulates the epidermal growth factor receptor and reverses the invasive phenotype of human papilloma virus-transfected keratinocytes

The human papillomavirus type 16 (HPV-16), the type most often associated with cervical cancer, immortalizes primary keratinocytes and inhibits serum/calcium-stimulated differentiation in culture. In this study, we have used a model of keratinocyte immortalization based upon HPV-16 to analyze perturbation of function and expression of E-cadherin, a Ca(2+)-dependent cell-cell adhesion molecule expressed by normal keratinocytes, and its associated proteins. An immortalized keratinocyte cell line generated by cotransfection with HPV-16 E6 and E7 showed decreased membrane E-cadherin expression and redistribution of alpha-, beta-, and gamma-catenin from the undercoat membrane to the cytoplasm. No changes in the level of expression were seen. Selection of the immortalized keratinocyte cell line for resistance to differentiation generated a more transformed cell line with an invasive phenotype, down-regulated E-cadherin and alpha-catenin, and up-regulated the epidermal growth factor receptor (EGFr). Transfection of an E-cadherin expression construct into the differentiation-resistant cell line restored membrane-bound E-cadherin and catenin expression, down-regulated the EGFr, and reversed the invasive phenotype. These results indicate that overexpression of the EGFr correlates with perturbation of the E-cadherin/catenin complex seen in the HPV-16 E6- and E7-transfected keratinocytes and may underlie a functional interaction between growth-regulatory factors and adhesion molecules (E-cadherin/catenin).

Downregulation of E-cadherin in the reparative epithelium of the human gastrointestinal tract

E-cadherin, an epithelial adhesion molecule, is critical for the maintenance of cell polarity and differentiation. We studied the distribution of E-cadherin in normal gut and in enteric ulceration to test the hypothesis that the motility of regenerative epithelium over ulcers is associated with a decrease in E-cadherin expression. Sections of normal stomach, small intestine, and colon were examined for E-cadherin distribution using the antibody HECD-1 and compared with the pattern seen in peptic ulceration and Crohn's disease. A subset was examined by in situ hybridization using 35S radiolabeled E-cadherin riboprobes. A wounding system employing the HT-29 cell line was used as an in vitro model of early healing. In the normal gut uniform strong basolateral staining was seen. Areas of ulceration showed a patchy reduction in membrane localized E-cadherin in regenerating epithelium, even though E-cadherin mRNA was demonstrable in this population. In wounded confluent HT29 layers, migrating cells also showed reduced E-cadherin immunostaining. These data support the notion that the motility of restitutive epithelial cells may relate to altered patterns of E-cadherin and that this may play an important role in the reconstitution of epithelial integrity after mucosal injury.

MUC1 expressed in PanC1 cells decreases adhesion to type 1 collagen but increases contraction in collagen lattices

A subline of human pancreatic cells (PanC1) that expresses low levels of cytokeratins 8 and 18 but not MUC1 mucin was transfected with both 3.5-kb and 3.9-kb full-length MUC1 cDNA. The MUC1-positive clone expressing the larger mucin was shown to express increased levels of cytokeratins 8 and 18 compared with the parental line or vector controls. Growth of these MUC1-transfected cells in type I collagen gels produced marked gel contraction that could be significantly reduced by the synthetic peptide SRGDTG or by growth in serum and fibronectin-depleted media. Cellular binding to type I collagen was found to be reduced by two- to four-fold in cells expressing the MUC1 mucin, for which the greatest inhibition was observed in cells expressing the larger form. No difference in cellular binding to fibronectin was observed. From these data we conclude that the human MUC1 mucin modifies the differentiated state of human pancreatic cells by altering cytokeratin expression and reducing adhesion to type I collagen but paradoxically enhancing the cellular contractile phenotype, effects that appear to be mediated by integrin expression and/or function.

Transforming growth factor-beta in GI neoplasia, wound healing and immune response

The last decade has been marked by tremendous advances in the biochemical and functional characterization of TGF-betas and their receptors in normal and transformed cells. TGF-betas have been shown to modulate proliferation, differentiation and motility of different cell types in a number of in vitro model systems and in some cases with some intriguing results. It is obvious that there is no simple pattern that explains the TGF-betas biological activity in vitro and their effects on cell behaviour need to be assessed in the context of an appropriate physiological cellular environment. Cell-cell and cell-matrix interactions, the differentiating status of the cell together with the functional activity of other soluble growth factors can influence how TGF-betas modulate cell behaviour. However, the overwhelming interest in this field shown by clinicians and basic scientists is rapidly increasing our understanding of how growth factors such as TGF-betas regulate the homeostasis of the GI mucosa and their role in gastrointestinal carcinogenesis.