Identification of laminin binding proteins in cell membranes of a human colon adenocarcinoma cell line

PED/PEA-15 interacts with the 67 kD laminin receptor and regulates cell adhesion, migration, proliferation and apoptosis

Phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes-15 kD (PED/PEA-15) is an anti-apoptotic protein whose expression is increased in several human cancers. In addition to apoptosis, PED/PEA-15 is involved in the regulation of other major cellular functions, including cell adhesion, migration, proliferation and glucose metabolism. To further understand the functions of this protein, we performed a yeast two-hybrid screening using PED/PEA-15 as a bait and identified the 67 kD high-affinity laminin receptor (67LR) as an interacting partner. 67 kD laminin receptor is a non-integrin cell-surface receptor for the extracellular matrix (ECM), derived from the dimerization of a 37 kD cytosolic precursor (37LRP). The 67LR is highly expressed in human cancers and widely recognized as a molecular marker of metastatic aggressiveness. The molecular interaction of PED/PEA-15 with 67LR was confirmed by pull-down experiments with recombinant His-tagged 37LRP on lysates of PED/PEA-15 transfected HEK-293 cells. Further, overexpressed or endogenous PED/PEA-15 was co-immunoprecipitated with 67LR in PED/PEA-15-transfected HEK-293 cells and in U-373 glioblastoma cells, respectively. PED/PEA-15 overexpression significantly increased 67LR-mediated HEK-293 cell adhesion and migration to laminin that, in turn, determined PED/PEA-15 phosphorylation both in Ser-104 and Ser-116, thus enabling cell proliferation and resistance to apoptosis. PED/PEA-15 ability to induce cell responses to ECM-derived signals through interaction with 67LR may be of crucial importance for tumour cell survival in a poor microenvironment, thus favouring the metastatic spread and colonization.

Changes of glycoprotein and collagen immunolocalization in the uterine artery wall of postmenopausal women with and without pelvic organ prolapse

Pelvic organ prolapse (POP) is accompanied by an altered composition of the extracellular matrix (ECM). However, it is unclear whether the changed ECM is the cause or the consequence of POP, as stretching of the tissue may have an effect on the composition of the ECM. To address this question, we analyzed the connective tissues of the uterine artery wall of postmenopausal women with and without POP. The uterine artery wall is stretched in patients with POP, but this stretching is unlikely to cause the POP. Twenty-one women (13 with POP and 8 without POP) hospitalized for hysterectomy were included in this study. Tissue samples from the uterine artery were analyzed for collagen (types I, III, IV, V and VI) and other ECM proteins (fibronectin, laminin, tenascin, vitronectin and elastin) using immunofluorescence microscopy. Results revealed that uterine artery samples of women with prolapse showed a significantly weaker immunoreactivity to type VI collagen, vitronectin and elastin and a stronger immunostaining for type III collagen and tenascin as compared to control samples. Our results suggest that the ECM may be altered in response to mechanical stretch. Changes in the ECM composition as observed in POP may not necessarily be the reason for the development of pelvic floor relaxation in postmenopausal women.

Periurethral connective tissue status of postmenopausal women with genital prolapse with and without stress incontinence

OBJECTIVE

Connective tissue consists mainly of collagen and structural glycoproteins and is considered an important factor of the supportive structures of the genitourinary region. Few data have been published as yet with respect to the role of connective tissue in pelvic floor relaxation and genuine stress incontinence (GSI). We compared periurethral connective tissue structures between continent and incontinent postmenopausal women with genital prolapse.

METHODS

Twenty-nine women underwent pelvic floor reconstructive surgery (anterior colporrhaphy: n = 29, sacrospinous fixation: n = 12), with biopsies obtained from the periurethral region. Fifteen patients and 14 women were incontinent and continent, respectively. Tissue samples were investigated for localization and distribution of collagen (types I, III, IV, V, VI) and glycoproteins (fibronectin, laminin, vitronectin) using immunofluorescent microscopic techniques.

RESULTS

Collagen types I, III, IV, V, and VI were found in all tissue samples. Compared with the continent women, the tissue samples of the incontinent women showed a significantly weaker immunohistochemical staining of type I, III, and VI collagen. No difference in staining patterns of collagen type IV and V, fibronectin, and laminin was observed between the two groups. Intact vitronectin was found in the periurethral tissues of all the continent women, whereas this glycoprotein was either absent or fragmented in the incontinent women.

CONCLUSIONS

Our results indicate an altered metabolism of connective tissue in the periurethral region with a significant decrease of collagen and vitronectin expression in postmenopausal women with pelvic floor relaxation with and without GSI.

Overexpression of the 67-kD laminin receptor correlates with tumour progression in human colorectal carcinoma

The high affinity 67-kD laminin receptor (67LR) is a cell surface protein whose expression is increased in a number of human carcinoma models. To date, 67LR expression in colorectal carcinomas has been examined in a small number of cases. 67LR expression has been immunohistochemically analysed in a large series of human colorectal neoplasms, using the MLuC5 monoclonal antibody. The study included 59 samples of non-neoplastic mucosa, 45 polyps (11 hyperplastic, 34 adenomas), 196 carcinomas, and lymph node metastases of 87 carcinomas. Epithelial cells of normal mucosa and hyperplastic polyps were negative or showed weak positivity in the paranuclear and apical areas of the cytoplasm. In adenomas and carcinomas, the staining was stronger, with a membranous or cytoplasmic pattern. The expression of 67LR correlated significantly with the progression from normal mucosa (22 per cent) to adenoma (44 per cent), carcinoma (61 per cent), and lymph node metastasis (75 per cent) (P < 0.0001). Expression of the laminin receptor showed a tendency to be more frequently positive in advanced stage (III+IV; 67 (III+IV; 67 per cent) when compared with early stage (I+II) carcinomas (54 per cent). The difference, however, was not statistically significant (P = 0.058). In addition, 14 out of 28 (50 per cent) primary carcinomas without 67LR expression became positive in lymph node metastases, while most (86 per cent) of the MLuC5-positive primary carcinomas were also immunoreactive in metastases. In conclusion, these results indicate that 67LR is up-regulated in the progression of human colorectal carcinomas and may play a role in the local and metastatic progression of these tumours.

Variability of neoplastic parameters in colon tumours, and its significance in diagnostic practice

We have reviewed the value of individual variability in the reaction of tissues to treatment with carcinogens, and the manifestation of this variability in different morphological (histological, morphometric, and ultrastructural), histochemical and immunohistochemical parameters generated in tumorous tissues. Moreover, we also reviewed data in the literature on individual variability in the manifestation of some biochemical and immunochemical markers which are accumulated in the serum of tumour-bearing patients and which are characteristic for the different phases of tumourigenesis. The high variability of different tumorous parameters suggests that none can be utilized alone as a conclusive marker of neoplasia and that only their combined use can give objective information. We also reviewed the impact of this variability in the evaluation of various pathological methods to detect different stages of neoplastic transformation in the colon. It has been concluded that none of the present approaches can be absolutely conclusive and without false results, and that objective information regarding early cancerous changes may be obtained only by use of combined analyses utilizing several laboratory methods. The diagnostic procedures should be based on the complex utilization of all appropriate methods using the quantitative interpretation of the obtained data. Multivariate analysis of many parameters should be very effective for the prediction of therapeutic results.

Adhesive properties and integrin expression profiles of two colonic cancer populations differing by their spreading on laminin

The mostly undifferentiated parental HT29 (HT29p) human colonic adenocarcinoma cell line and a differentiated subpopulation selected by the anti-cancer drug 5-fluorouracil (HT29-Fu) (Lesuffleur et al. (1991) Int. J. Cancer 49, 721–730) display strikingly different behavior when grown on laminin coatings: the former grows as aggregates while the latter grows as monolayers. In an attempt to explain this difference, we performed a comparative study of cell adhesion properties and of expression, involvement and localization of the alpha 6, beta 1 and beta 4 subunits constituting the integrin family among the two cell populations. HT29p and HT29-Fu cells exhibited a similar adhesion pattern to laminin and laminin fragments E8 and P1. In both cell lines, cell adhesion could be blocked at about 90% with anti-alpha 6 subunit antibodies and around 30–50% with anti-beta 1 antibodies; no inhibition of the cell adhesion was obvious when using anti-beta 4 antibodies. Immunoprecipitations of iodinated membrane-solubilized proteins and immunoblotting experiments showed that all alpha 6 chains expressed in both HT29p and HT29-Fu cell populations exist as alpha 6 beta 4 integrins; beta 1 subunits are associated with alpha 2 and alpha 3 chains. When HT29p or HT29-Fu cells were injected subcutaneously in nude mice, a similar expression pattern of alpha 6, beta 4 and beta 1 integrin subunits was noticeable in the resulting tumors: alpha 6 and beta 4 subunits were localized at the basal surface of the tumor cells facing the stromal elements, and to a lesser extent at the cell-cell contacts within the tumor-cell clumps; beta 1 subunits were mainly found within the cytoplasm of the tumor cells. Despite these overall similarities among the two cell lines, the following changes could account for their different behavior on laminin: less proteolytic processing of the beta 4 integrin subunit occurred in HT29-Fu cells yielding peptidic fragments of 175 kDa, which are absent from the parental cells; the immunostaining pattern of the various subunits demonstrated a segregation of alpha 6, beta 4 and beta 1 integrin subunits on the basal side of the HT29-Fu cells when cultured on laminin to the detriment of their lateral location, a phenomenon that was not obvious in the parental cells. Altogether, these results suggest that the distinct behavior of the undifferentiated versus differentiated HT29 cell populations on laminin is not related to altered adhesion properties of the cells but rather to a deficient stabilization of the adhesion leading to cell spreading.(ABSTRACT TRUNCATED AT 400 WORDS)

Basement membrane proteins in synovial membrane: distribution in rheumatoid arthritis and synthesis by fibroblast-like cells

Rheumatoid arthritis is a complex disease of unknown origin. In consequence of some immunological reactions, proliferative invading synovial tissue leads to destruction of normal joint architecture. The aim of this study was to investigate qualitative changes in extracellular matrix distribution of proliferating rheumatoid synovium and their cellular origin. Synovial tissues from 57 clinically indicated arthrotomies were investigated with immunofluorescence, using specific antibodies against extracellular matrix proteins in tissue slides and cultured cells, which were also studied for collagen biosynthesis. Results indicated that synovial fibroblast-like cells synthesize and secrete basement membrane proteins laminin and collagen type IV as e.g. endothelial cells or organogenic fibroblasts. Laminin and collagen type IV were specifically demonstrated pericellularly in the hyperplastic lining layer of active rheumatoid synovitis. These findings are discussed with respect to the possible implication of altered cell-matrix interactions in rheumatoid synovial proliferation.

Ito cell heterogeneity: desmin-negative Ito cells in normal rat liver

The presence of desmin is used to identify Ito cells in rat liver and to evaluate the purity of separated and cultured Ito cells. Heterogeneity of the normal Ito cell population has been suggested; this could include variations in the content of cytoskeletal components. For these reasons we decided to reevaluate the use of desmin staining as a phenotypical marker of Ito cells in normal rat liver. Our approach was to combine desmin staining with identification of vitamin A (autofluorescence), lipid droplets (Sudan III), vimentin, laminin and tenascin, using cryostat sections: Immunofluorescence, double-immunofluorescence or immunoperoxidase techniques were used. All the techniques described corroborate the existence of desmin-negative Ito cells, mainly located in pericentral areas. In fact, lobular desmin-positive cells showed uneven distribution because they were more frequent in periportal than in pericentral areas. On the contrary, Ito cells identified on the basis of morphological criteria or positivity for laminin were evenly distributed. Double immunofluorescence confirmed this observation, showing nearly complete codistribution of laminin and desmin in periportal areas. Outside this area, positivity for desmin was observed only in about 50% of laminin-positive cells. Our observations suggest that desmin cannot be viewed as a phenotypical marker but rather is a differentiation marker of Ito cells, possibly indicating a specific functional state.

Age-dependent changes of the immunohistochemical distribution of various collagen types and structural glycoproteins in the human uterine tube

This immunohistochemical investigation deals with the age-dependent localization and distribution of types I, III, IV, V, and VI collagen and the structural glycoproteins undulin, fibronectin, laminin, tenascin, and vitronectin in the connective tissue of the human uterine tube. The stroma of this oviductal region consisted of all collagen types. Collagen types I and VI were distributed throughout the connective tissue of the mucosa reaching the basal membrane. The findings suggest that the amount of these collagen types and type III collagen increases in relation to age, since the coarser fibres of the mucosal stroma in the uterine tubes of older women were strongly labelled by immunohistochemistry. The pattern of undulin reactivity was similar to that of types I and VI collagen. The exact quantitative proportions of age-related oviductal changes for types I, III, and VI as well as of undulin are still unknown. Type V collagen was associated with a fine fibre meshwork in the mucosal stroma. The fibres reached the subepithelial zone which appeared membrane-like. The location of type V collagen-associated fibres and aldehyde fuchsin-positive fibres characterized in our previous studies appears to be identical. Moreover, the structural glycoproteins undulin, fibronectin, laminin, tenascin, and vitronectin were detected in the mucosal stroma. The staining of fibronectin was less pronounced than that of undulin. Laminin was located in the zone of the basal membrane, whereas tenascin was mainly found in the mucosal vessels. Contrary to these findings, tenascin showed a unique distribution in the region near the basis of the mucosal folds in the isthmic part. Vitronectin could be observed in the same region of the isthmic part of uterine tubes obtained from younger women. However, the zonal localization of vitronectin reactivity was absent in the isthmic part of older women.

Collagen metabolism during wound healing in rats. The aminoterminal propeptide of type III procollagen in serum and wound fluid in relation to formation of granulation tissue

The aminoterminal propeptide of type III procollagen (PIIINP) in serum has been shown to correlate with fibrillogenesis, and thus to be a potential direct marker of type III collagen deposition. The aim of the study was to investigate the correlation between changes in serum PIIINP and formation of granulation tissue during pharmacological suppression. Granulation tissue was induced in rats by the implantation of viscose cellulose sponges. Pharmacological suppression was achieved by cyclophosphamide treatment. To distinguish between the isolated effect of cyclophosphamide and the influence of the weight loss caused by treatment, weight loss caused by starvation was investigated. In untreated rats, serum PIIINP and wound fluid PIIINP were related to formation of granulation tissue (serum: r = 0.58, p < 0.05; wound fluid: r = 0.56, p < 0.05). In rats treated with cyclophosphamide, collagen deposition and formation of granulation tissue were markedly reduced, as compared within the untreated rats (6% vs 33%, p = 0.01). Wound fluid PIIINP reflected the sparse collagen deposition (r = 0.48, p < 0.05), whereas serum PIIINP decreased (-35%, p < 0.01) and was not correlated with the formation of granulation tissue. In starved rats, with a weight loss of 8%, formation of granulation tissue, vascular density, and collagen deposition were not reduced. Wound fluid PIIINP reflected the formation of granulation tissue (r = 0.52, p < 0.05), whereas serum PIIINP remained unchanged despite normal formation of granulation tissue. Starvation of rats without implants caused a decrease in serum PIIINP (-33%(-)-48%, p < 0.01). We conclude that during cyclophosphamide treatment and after a moderate weight loss, serum PIIINP is not a valid marker of fibrillogenesis. However, in normal rats with free access to food, changes in serum PIIINP mirror fibrillogenesis. Furthermore, our study provides experimental evidence consistent with the hypothesis that wound fluid PIIINP directly mirrors the local formation of granulation tissue, independent of weight loss and cyclophosphamide treatment.

Altered glycosylation of integrin adhesion molecules in colorectal cancer cells and decreased adhesion to the extracellular matrix

The integrin mediated interactions between tumour cells and the surrounding extracellular matrix are thought to play crucial parts in the complex process of invasion and metastasis. It has been previously shown that the expression of integrins is differently diminished in a chain-specific manner in human colorectal cancer. To further characterise the integrins still expressed in colorectal carcinomas, immunoblots with monoclonal antibodies against the beta 1 integrin subunit have been performed. In isolated cell membranes of colorectal cancers a second smaller beta 1 chain (105 kD non-reduced) was found as well as the mature beta 1 chain (116 kD non-reduced) present in normal mucosa of the colon. This smaller beta 1 chain comigrates with the diminished glycosylated precursor form of the beta 1 chain. The role of N-glycosylation for the function and expression of integrins in vitro was therefore investigated, with deoxymannojirimycin (DMJ) and deoxynojirimycin (DNJ) as specific inhibitors of N-glycan processing. Pretreatment of human colon adenocarcinoma derived HT-29 cells with DMJ resulted in an expression of the 105 kD beta 1 precursor chain and of smaller forms of the alpha 1, alpha 3, alpha 6, and alpha v integrin subunits in a time and dose dependent manner. HT-29 cells treated with DMJ adhered poorly to laminin (8% of untreated controls), collagen type IV (40%), and fibronectin (35%). Pretreatment of the cells with DNJ did not alter the molecular weight of the integrin chains expressed and reduced HT-29 adhesion to laminin and fibronectin only to 68% and 49% respectively. Adhesion to collagen type IV was increased to 124% by DNJ. These results show that N-glycan processing is essential for the function and expression of integrins in human colorectal cancer cells. An altered glycosylation of these adhesion receptors may contribute to a more invasive or metastatic phenotype in colorectal cancer.

Detection of laminin receptor mRNA in human cancer cell lines and colorectal tissues by in situ hybridization

The 67-kd high-affinity laminin receptor (67 LR) is a gene product whose expression appears to be associated with the invasive and metastatic phenotype of a variety of human cancer cells. Northern blot hybridization has been routinely used to quantify the level of 67 LR mRNA from total cellular RNA extracts of homogenized tissue specimens or in vitro grown cell populations. This technique is useful to assess the average expression of the 67 LR mRNA of a particular sample but does not provide information about expression in specific cell types nor about heterogeneity of expression from cell to cell. In this study, we analyzed the expression of 67 LR mRNA in four human cancer cell lines with varying degrees of expression of 67 LR protein (renal cancer A-704, breast carcinoma MCF-7/4 and MCF-7/7, and pancreatic cancer Panc-1) using in situ hybridization performed with 67 LR riboprobes. Total cellular RNA was simultaneously extracted from the cell lines and hybridized on Northern blots with a 67 LR cDNA probe to assess the validity of the mRNA detection by in situ hybridization. Sixty-seven LR mRNA expression was higher in Panc-1 and MCF-7/4 cells than in MCF-7/7 and renal carcinoma A-704. There was a direct correlation (R2 = 0.88) between the in situ hybridization analysis and the mRNA levels detected by Northern blot analysis. The in situ hybridization method showed a heterogeneous expression of the 67 LR mRNA in the four cell lines with different subpopulations of cells showing a range from negative to high levels of the message. Sixteen freshly frozen human colorectal tissues (seven adenocarcinomas, five matched normal mucosae, and four adenomas) were also analyzed by in situ hybridization. The 67 LR mRNA was localized in normal and neoplastic epithelial cells. Adenocarcinoma cells showed a 1.6- to 5-fold higher expression (P < 0.02 according to the Wilcoxon-Mann-Whitney test) than did epithelial colonic cells from normal mucosae or adenomas. The signal tended to be stronger in poorly differentiated carcinomas and carcinomas with metastases than in moderately differentiated and nonmetastatic tumors. We conclude that the high expression of 67 LR mRNA in colorectal tumors is due to an increased production by tumor cells. Furthermore, in situ hybridization is an effective method to detect the expression of LR mRNA in cultured cell lines as well as in frozen tissue sections.

Increased collagen type III synthesis by fibroblasts isolated from strictures of patients with Crohn's disease

Increased type III collagen deposition in all layers of the intestinal tract, including the lamina propria, is a common feature of strictures in Crohn's disease. In the present study, it was found that in comparison with fibroblasts from normal or nonstrictured but inflamed intestinal lamina propria, the fibroblasts isolated from strictures of patients with Crohn's disease produce significantly more collagen, especially collagen type III. Transforming growth factor beta 1 (TGF-beta 1) significantly increased collagen type III synthesis in intestinal lamina propria fibroblasts isolated from all patients. The effect of TGF-beta 1 on type III collagen synthesis in fibroblasts from strictures in Crohn's disease was significantly higher than that in fibroblasts from inflamed specimens of the same patients. In contrast, platelet-derived growth factor decreased collagen type III synthesis in lamina propria fibroblasts derived from strictures compared with fibroblasts from nonstrictured but inflamed tissue. These findings indicate that fibroblasts in the lamina propria of patients with Crohn's disease have a different reactivity towards cytokines. On the basis of increased type III collagen deposition in intestinal strictures of Crohn's disease by using cell adhesion and cell proliferation assays, it was shown that collagen type III stimulated adhesion and proliferation of lamina propria fibroblasts. The current data provide evidence that the different reactivity of mesenchymal cells to cytokines in terms of synthesizing type III collagen fibrils, which is a major component of collagen fibrils, may play an important role in the pathogenesis of fibrosis and stricture formation in chronic inflammatory bowel diseases.

Laminin binding in membranes of a rat pancreatic acinar cell line are targets for glucocorticoids

The adhesive properties of tumor cells to basement membranes are known to play a crucial role in the complex process of tumor invasion and metastasis. Therefore, the interaction between the rat pancreatic acinar cell line AR42J and various extracellular matrix components along the route of differentiation induced by glucocorticoids was investigated. AR42J cells displayed a significantly higher affinity to laminin than to type IV collagen and fibronectin. Flow cytometric analysis showed expression of the 67-kilodalton laminin receptor and the integrin VLA-6 as potential laminin binding proteins in AR42J cells. Cell adhesion inhibition studies revealed that binding of undifferentiated AR42J cells to laminin was mediated predominantly by the 67-kilodalton laminin receptor. Dexamethasone pretreatment, which results in a more differentiated phenotype of AR42J cells, reduced the adhesion to laminin. In contrast to undifferentiated cells, interaction of differentiated AR42J cells to laminin was mediated by VLA-6. Dexamethasone-induced differentiation of pancreatic AR42J cells was paralleled by a decreased expression of 67-kilodalton laminin receptors, most likely because of a downregulation of the steady-state concentration of 67-kilodalton laminin receptor messenger RNA induced by dexamethasone. The hormonal modulation of cell matrix interactions opens interesting perspectives to the potential regulation of infiltrative growth and metastasis in pancreatic cancer.

Altered deposition of basement-membrane molecules in co-cultures of colonic cancer cells and fibroblasts

Two human colon carcinoma cell lines, HT29 and Caco-2 were co-cultured with fetal rat or human skin fibroblasts. Their morphological features, ultra-structural characteristics at the heterologous cell interface, and the deposition of basement-membrane molecules [laminin, type-IV collagen, heparan sulfate proteoglycan (HSPG)] at the epithelial-stromal junction were analyzed. The 2 cell lines behaved differently. HT29 cells did not spread on the fibroblasts and grew as clusters, while Caco-2 cells formed a monolayer over the fibroblastic feeder layer. Only the latter carcinoma cells exhibited cytoplasmic processes towards the fibroblasts and, after 5 days in co-cultures, a structured basement membrane (BM). The immunocytochemical analysis of the BM constituents revealed the absence of the molecules studied at the sites of heterologous contacts in the case of HT29 cells. In contrast, in the co-cultures comprising Caco-2 cells, laminin and type-IV collagen were progressively deposited in a polar fashion at the epithelial-fibroblastic interface which, however, remained devoid of HSPG molecules. Together with earlier data indicating a dual origin of the BM molecules located at the epithelial-fibroblastic interface in normal intestine, the present study shows that the cancer cells as well as the fibroblastic ones under the influence of carcinoma cells display an altered capacity to synthesize and/or secrete BM molecules. The extent of such abnormalities correlates with the differentiation of the cells. Finally, these modifications occur concomitantly with alterations in cell interactions which vary among cell lines.

Identification of different laminin binding proteins in basolateral cell membranes of human colorectal carcinomas and normal colonic mucosa

The adhesive properties of tumour cells to laminin, the major glycoprotein of basement membranes, play a crucial part in the complex process of tumour invasion and metastasis. We therefore investigated the expression of laminin binding proteins in isolated basolateral cell membranes of human colorectal carcinomas and the adjacent normal colonic mucosa. Cell membrane binding assays and immunoblotting experiments showed appreciable quantitative and qualitative differences in the expression of these proteins in neoplastic and normal tissue. Epithelial basolateral cell membranes of colorectal carcinomas bound five to eight times more radioactive labelled laminin than basolateral cell membranes of the adjacent normal colonic epithelium. The expression of laminin binding proteins with Mr 66,000-69,000 daltons corresponding to the so called 'Mr 67,000 dalton laminin receptor' was three to four times higher in colorectal carcinomas than in normal colonic epithelium. In addition, laminin binding proteins with higher molecular weights, which may be related to the family of integrins, were also increased in colorectal carcinomas. In particular, laminin binding proteins with Mr 180,000 daltons were exclusively expressed on neoplastic epithelial cells of human colorectal carcinomas. Our data suggest that certain classes of laminin binding proteins may be selectively expressed on colonic tumour cells, leading to an increased capacity for migration, invasion, and metastasis.