Patterns of α- and β-catenin and E-cadherin expression in colorectal adenomas and carcinomas

Previous in vitro and in vivo model studies have shown that when E-cadherin expression in carcinoma cells is reduced, invasive behaviour ensues. The situation in human cancer in vivo, however, appears to be more complex, as immunohistochemically determined E-cadherin expression in various carcinomas, including colorectal cancer, does not always correlate with invasive growth. Loss of cell adhesion during invasion in spite of E-cadherin expression might be associated with a defective cadherin–catenin complex. The expression of α- and β-catenin in comparison with E-cadherin was therefore examined in colorectal adenomas and carcinomas and in lymph node and liver metastases. In normal colonic mucosa, α- and β-catenin immunoreactivity occurred along the lateral plasma membranes of the epithelial cells, in a pattern identical to E-cadherin staining. A similar pattern was found in colorectal adenomas and in most malignancies. In general, in neoplastic epithelia, the majority of the cancer cells displayed a normal (matching) pattern of E-cadherin and catenin expression. It is concluded that the patterns of expression of E-cadherin and α- and β-catenin are very similar in colorectal neoplasms. This observation indicates that invasion in colorectal cancer is not paralleled by consistent loss of expression of the components of the cadherin–catenin complex. © 1997 John Wiley & Sons, Ltd.     

Changes in the expression of syndecan-1 in the colorectal adenoma–carcinoma sequence

 Syndecan-1, a transmembrane heparan sulphate proteoglycan (HSPG), functions as a matrix receptor on the basal surface of epithelial cells. It also co-localizes with E-cadherin at the lateral cell surface where its function is uncertain. Tumour development in the large bowel is associated with loss of normal epithelial adhesion and altered patterns of expression of cell adhesion molecules, possibly including syndecan-1. To evaluate changes in syndecan-1 expression during the development of colorectal neoplasia, 59 adenomas and 20 carcinomas arising from adenomas were investigated by immunohistochemistry. The staining intensity and distribution of syndecan-1 and E-cadherin in sequential sections was examined, semi-quantified and compared. Staining of syndecan-1 and E-cadherin was uniform in normal colorectal epithelial cells, and located at the basolateral surface. No significant change was seen in either molecule in mildly or moderately dysplastic adenomas. A significant reduction in expression of both syndecan-1 and E-cadherin was seen in severely dysplastic epithelium as compared to moderate dysplasia (P=0.001 and P=0.004 respectively). Similarly, there was a significant reduction of both molecules in carcinomas compared with associated adenomas (syndecan-1 P=0.00003; E-cadherin P=0.002). In both cases the loss of syndecan-1 expression was more striking than that of E-cadherin. Previous in vitro studies have shown that epithelial cells made deficient in syndecan-1 cease to express E-cadherin, suggesting a causal association. Our results support these findings and indicate that disruption of cell-matrix adhesion is critical in colorectal carcinogenesis, probably preceding changes in the purely homotypic cell-cell adhesion mediated by E-cadherin. Received: 11 May 1998 / Accepted: 14 September 1998     

L-CAM expression in lymph node and liver metastases of colorectal carcinomas

L-CAM, also known as E-cadherin, is a cell adhesion molecule expressed on the plasma membranes of epithelial cells at the intercellular interface. From in vitro gene transfection experiments the idea has been conceived that loss of L-CAM expression might be related to the invasive capacity as well as metastatic potential of tumour cells. In several tumours a relation between the grade of differentiation and L-CAM expression has been noticed: loss of differentiation appears to be associated with loss of L-CAM immunoreactivity. Also, in lymph node metastases of poorly differentiated carcinomas loss of L-CAM expression was demonstrated. In this study we describe L-CAM expression in lymphogenous and haematogenous metastases of large bowel adenocarcinomas, using an indirect immunoperoxidase method with the monoclonal anti-L-CAM antibody 6F9. All the metastases studied—lymphogenous as well as haematogenous—demonstrated L-CAM immunoreactivity in a pattern comparable to that of primary tumours. Intratumour heterogeneity in expression was noted, with normal intercellular, apical (non-functional), and focally negative areas in the same tumour. The data indicate that primary tumours and their metastases do not differ strikingly in their pattern of L-CAM expression. This would be consistent with transient rather than constitutive down-regulation of L-CAM in invasive and metastatic cancer cells.     

Reciprocity between membranous and nuclear expression of β-catenin in colorectal tumours

 β-Catenin has a central role not only in linking the cadherin-mediated cell adhesion system but also in the intercellular signalling pathway. To investigate alterations of β-catenin in the development of colorectal carcinoma, the pattern of β-catenin expression was studied using immunohistochemistry in 74 sporadic colorectal adenomas, in histologically normal mucosa adjacent to 65 of these adenomas, and in 52 carcinomas arising in adenomas. All normal epithelia displayed cell boundary staining for β-catenin. Adenomas and carcinomas showed varying degrees of membranous staining. However, some tumours also showed nuclear staining of β-catenin protein. Decreased membranous and increased nuclear β-catenin staining were associated with increasing degrees of dysplasia in adenomas (P < 0.005, P < 0.05, respectively). Carcinomas manifested significantly reduced membranous, but enhanced nuclear β-catenin expression compared with their associated adenomas (P < 0.001, P < 0.005, respectively). An inverse correlation was found between decreased membranous and increased nuclear staining of β-catenin in both adenomas and carcinomas (P < 0.025, P < 0.05, respectively). The data confirm that reduced membranous and increased nuclear expression of β-catenin is associated with the progression of colorectal adenomas to carcinomas. Our results also suggest that decreased membranous expression of β-catenin may result from aberrant localisation of the protein in the cell nucleus. Received: 1 January 1997 / Accepted: 26 February 1997     

Human colorectal adenomas demonstrate a size-dependent increase in epithelial cyclooxygenase-2 expression

Non-steroidal anti-inflammatory drugs are chemopreventive for colorectal cancer. This effect is due in part to their ability to inhibit the inducible isoform of cyclooxygenase (COX-2). However, the cellular expression and role of COX-2 in the premalignant stages of colorectal tumourigenesis is unclear. COX-2 expression was assessed in 35 human colorectal adenomas and 38 sporadic invasive colorectal adenocarcinomas. Adenomas were classified as small (<5 mm in diameter), medium (5-10 mm), and large (>10 mm). All tissues were paraffin-embedded and formalin-fixed. COX-2 protein expression was determined using immunohistochemistry. COX-2 was detected in the epithelial cells in 35 of 38 carcinomas (92%) and in 8 of 8 (100%) lymph node metastases. All of the epithelial cells expressed COX-2 in 30 of 35 (86%) carcinomas and in 100% of the lymph node metastases. Twenty-three of 35 (66%) adenomas expressed COX-2 in the tumour epithelium. With an increase in the size of adenoma (<5 mm, 5-10 mm, >10 mm), there was an increase in (i) the proportion of adenomas with immunoreactive COX-2 in the epithelium (p = 0.036)-this was 38% in small adenomas and 82% in large adenomas; (ii) the extent of epithelial COX-2 staining within a given tumour (p = 0.003)-100% of epithelial cells were COX-2-positive in 15% of small adenomas and in 73% of large adenomas; and (iii) the intensity of epithelial COX-2 staining (p = 0.009)-strong COX-2 staining occurred in 8% of small adenomas and in 36% of large adenomas. COX-2 immunoreactivity was not detected in adjacent normal epithelium but was apparent in fibroblasts and inflammatory mononuclear cells of adjacent normal, adenoma, and carcinoma tissue. These results suggest that epithelial COX-2 activity is important for the growth and/or survival of adenomatous epithelial cells from an adenoma diameter of less than 5 mm and that there is a selective advantage for adenoma epithelial cells expressing higher levels of COX-2.     

Expression of E-cadherin in oesophageal carcinomas from the UK and China: disparities in prognostic significance.

AIMS: To study the expression and prognostic significance of the cell adhesion molecule E-cadherin in oesophageal tumours from the UK (low risk area) and China (high risk area). METHODS: E-cadherin expression was measured immunohistochemically in resected tumours from 17 patients in the UK with adenocarcinoma, 23 patients from the UK with squamous carcinoma, and 30 patients from China with squamous carcinomas who survived for five years postoperatively and compared with similar tumours from patients in the same regions who did not survive (140 tumours in all). RESULTS: Normal squamous epithelial cells and well differentiated areas of tumours showed membranous staining for E-cadherin expression. Cytoplasmic staining, heterogeneous staining, or an absence of staining was seen in dysplastic epithelium and in less well differentiated areas of tumours. Only one of 140 primary tumours had homogeneous membranous expression. In tumours from UK patients with adenocarcinoma (p = 1.00) and from Chinese patients with squamous carcinomas (p = 0.06) there was no correlation between E-cadherin absence and non-survival. In tumours from UK patients with squamous carcinomas there was a significant correlation between absence of E-cadherin and non-survival (p = 0.009). Tumours from UK patients with squamous carcinoma who survived were significantly less likely to be E-cadherin absent than those from Chinese patients with squamous carcinomas who survived (p = 0.007). Multivariate analysis (n = 37 UK, paired data) showed that absence of E-cadherin in the primary tumour was a weak independent prognostic factor for non-survival (30% significance level; p = 0.26; odds ratio = 3.56). In UK nodal metastases there was no correlation between E-cadherin expression and survival. CONCLUSIONS: Squamous carcinomas from UK patients differed from both adenocarcinomas from UK patients and carcinomas from Chinese patients with respect to E-cadherin expression and prognostic significance. In tumours from UK patients, E-cadherin absence in the primary carcinoma (a weak independent prognostic factor) but not metastases correlated with non-survival.     

Glut-1 expression in dysplastic and regenerative lesions of the colon

Monosaccaride transporter proteins are responsible for transmembrane transport of monosaccarides into cells. Glucose transporter protein 1 (Glut-1) is most prevalent in the cell membranes of erythrocytes and facilitates transport of glucose in tissues with barrier functions, i.e. blood brain barrier. Expression of Glut-1 in malignant tumors is increased due to increased metabolic need of the proliferating cell populations. In colorectal adenomas and carcinomas, membranous expression of Glut-1 has been associated with higher grade of tumors and decreased survival time. We studied the expression of Glut-1 in dysplastic proliferations of the colon which included sporadic adenomas and dysplasia associated lesions (DALM) in patients with ulcerative colitis and reactive/regenerative proliferations of the colon, including non-dysplastic chronic colitis, acute colitis and ischemia. Two patterns of Glut-1 expression were detected. Most adenomas and DALMs showed at least focal membranous expression of Glut-1. In addition a second staining pattern was recognized which consisted of prominent supranuclear dots. This pattern of staining was not only seen in adenomas and DALM but also in non-dysplastic areas immediately surrounding sporadic adenomas, in regenerative chronic colitis and in areas surrounding acute inflammation. Areas away from dysplasia did not show any positive staining for Glut-1. We conclude that two distinct patterns of Glut-1 expression may be found in colonic epithelial proliferation: membranous staining, associated with dysplasia, and, heretofore not described, supranuclear staining which may be related to Glut-1 expression secondary to expression of specific growth factors and not necessarily related to dysplasia.     

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.     

E-cadherin, CD44 and CD44v6 in squamous intraepithelial lesions and invasive carcinomas of the uterine cervix: an immunohistochemical study.

OBJECTIVE: To evaluate the immunoexpression pattern of E-cadherin, CD44std and the variant isoform v6 in normal squamous epithelium, low and high squamous intraepithelial lesions (SILs) and invasive squamous cell carcinomas (ISCCs) of the uterine cervix. The purpose was to determine whether any distinctive change in antigenic expression could contribute to the recognition of the earliest commitment to neoplasia and/or the onset of the invasive phenotype. METHODS: Immunohistochemistry using the avidin-biotin indirect immunoperoxidase method was used to study the protein expression of epithelial cadherin (E-cadherin), cluster differentiation 44 (CD44), and the isoform v6 (CD44v6) in 124 human cervical samples (5 normal, 39 low-grade, 54 high-grade and 26 ISCCS) in formalin-fixed, paraffin-embedded tissue blocks. RESULTS: Membranous expression of E-cadherin, CD44 and CD44v6 was preserved in normal squamous epithelium and in low-grade squamous intraepithelial lesions. A significant association was observed with the histological grade of the SILs and the immunoreactivity (membranous versus cytoplasmic) pattern of E-cadherin (p < 0.001), CD44std (p = 0.027) and CD44v6 (p < 0.001). A loss of membranous staining and a progressive increase in cytoplasmic staining was observed from low to high grade SILs to ISCCs. CONCLUSIONS: Our study demonstrates that during the development of cervical lesions substantial qualitative (subcellular localization-membrane to cytoplasmic) and quantitative alterations (changes in expression) occur in the protein expression of E-cadherin, CD44, and CD44v6 in cervical cancer. The most striking observation was the decrease in membranous immunoreactivity and the progressive increase in cytoplasmic staining of E-cadherin, CD44 and CD44v6, relating to loss of differentiation as a consequence of neoplastic transformation.     

An immunohistochemical examination of the expression of E-cadherin, α- and β/γ-catenins,and α2- and β1-integrins in invasive breast cancer

This study examines the expression of the cell–cell adhesion molecules E-cadherin and its associated proteins, the catenins and the matrix–cell adhesion molecules β1- and α2-integrins, in primary invasive breast carcinoma. Expression was assessed immunohistochemically on frozen sections by semi-quantitative scoring of the intensity and proportion of immunoreactivity in 55 cases. Associations with each other and with other histological and prognostic features and survival were sought. There was a significant association between loss of E-cadherin expression and loss of α- and β/γ-catenin immunostaining. In 20 per cent of cases, membranous immunoreactivity with E-cadherin antibody was absent. Absent cytoplasmic expression of α- and β/γ-catenins was seen in 24 and 22 per cent of breast cancers, respectively. The intensity of reactivity with E-cadherin showed a significant association with histological grade (p = 0·002) and tumour type (p < 0·001). Lobular carcinomas frequently showed loss of expression of E-cadherin, as reported elsewhere; loss of catenin expression was also found in these tumours. α-Catenin intensity also showed a relationship with grade (p = 0·008) and with oestrogen receptor (ER) status (p = 0·006). β/γ-Catenin expression was not associated with other known prognostic factors. Forty-nine per cent and 42 per cent of cases showed no membrane immunostaining with β1- and α2-integrin, respectively, and co-ordinated loss of β1- and α2-integrin expression was found. Both β1- and α2-integrin expression were associated with histological grade (p = 0·003 and p = 0·031, respectively) and β1 immunoreactivity with tumour type (p = 0·010). None of the variables examined showed a statistically significant association with tumour size or lymph node stage, or with overall survival, although a trend was seen (p = 0·087) towards poorer survival of patients with tumours with absent or weak expression of β1-integrin. The expression of these markers is of biological interest, but appears to be of little additional use in predicting clinical behaviour. Copyright © 1999 John Wiley & Sons, Ltd.     

Altered expression and function of E-cadherin in cervical intraepithelial neoplasia and invasive squamous cell carcinoma

HECD-1 monoclonal antibody has been used to localize E-cadherin, a calcium-dependent cell–cell adhesion molecule, in microwave-treated, paraffin-embedded sections from 53 cases of cervical intraepithelial neoplasia (CIN) (11 CIN I, 22 CIN II, and 20 CIN III), 16 invasive cervical squamous cell carcinomas, and seven metastases. In normal cervix, E-cadherin was expressed on the cell membrane of basal and parabasal cells. Cytoplasmic staining was present in occasional basal cells only. In CIN, the presence and localization of cytoplasmic E-cadherin were found to be significantly correlated with the grade of the CIN lesion. In squamous cell carcinomas, reduced membranous and increased cytoplasmic staining was seen with worsening differentiation. Loss of membranous E-cadherin expression was also detected in 4/7 metastatic deposits. E-cadherin expression (120 kD form on Western blotting) was seen in human cervical carcinoma cell lines (HT3, ME180, C41, Caski) that maintained the ability to aggregate in a homotypic adhesion assay and showed a typical epithelial morphology. E-cadherin-negative cell lines (Hela, SiHa, C33A) did not show adhesion. HOG-1 was the only E-cadherin-negative cell line which showed a significant degree of cell–cell aggregation. These data indicate that loss of membranous E-cadherin expression may represent one of the abnormalities underlying loss of cell polarity and differentiation which characterize CIN and invasive cervical cancer.     

Are heterogenous results of EGFR immunoreactivity in renal cell carcinoma related to non-standardised criteria for staining evaluation?

AIMS: To assess whether heterogeneity of epidermal growth factor receptor (EGFR) immunoreactivity in renal cell carcinoma (RCC) is related to non-standardised criteria for staining evaluation. METHODS: EGFR expression was investigated in 132 primary and 55 metastatic conventional RCCs using a tissue microarray technique. RESULTS: Overall, membranous and/or cytoplasmic EGFR immunostaining was present in 123 of 132 (93%) primary and 49 of 53 (92%) metastatic RCCs, with extensive immunoreactivity (> 50% of tumour cells) in 110 of 132 (83%) primary tumours and 39 of 53 (73%) metastases. Cytoplasmic staining was associated with high tumour stage and high tumour grade. In addition, strong membranous staining (score 3+) prevailed in high grade RCCs. Cytoplasmic immunostaining was associated with an unfavourable prognosis, whereas overall (cytoplasmic and membranous) immunoreactivity and intensity of membranous staining were not. CONCLUSIONS: Different methods of immunohistochemical evaluation led to different results, strengthening the need for standardisation, especially against a background of rapidly evolving EGFR targeted cancer treatment strategies.     

Human scribble accumulates in colorectal neoplasia in association with an altered distribution of beta-catenin

The loss of epithelial polarity and tissue architecture is a diagnostic feature of malignant tumors. In Drosophila, genetic studies identified 3 neoplastic tumor suppressor genes (nTSGs), and a loss of nTSGs has been shown to result in a disruption of apical-basal polarity and neoplastic growth in epithelial cells. Scribble is one type of the Drosophila nTSGs, which encodes a membrane-associated cytoplasmic protein containing the multi-PDZ domain. In contrast to Drosophila scribble, the oncogenic roles of its mammalian homologues have not yet been established. We herein immunohistochemically examined the distributions of hScrib protein in human colorectal neoplasia using affinity-purified antibody. In 50 cases of colorectal adenomas and adenocarcinomas, the accumulation of hScrib protein was commonly observed in comparison with the adjacent normal epithelia. Furthermore, the overexpression and distribution of hScrib was observed to extensively overlap with the cytoplasmic accumulation of beta-catenin. Like beta-catenin, the intense immunoreactivity of hScrib was often observed in small adenomas, thus, suggesting that hScrib could be involved in an early step of colon carcinogenesis. Five corresponding liver metastases showed a comparable immunoreactivity for anti-hScrib in comparison with their primary sites. In an immunofluorescence analysis on cultured cell lines, the loss of membranous staining of hScrib was observed according to the cytoplasmic translocation of beta-catenin. We herein demonstrate that the accumulation of hScrib protein might therefore be involved in colon carcinogenesis while also providing a possible link between hScrib and beta-catenin.     

High nuclear expression of protein arginine methyltransferase‐5 is a potentially useful marker to estimate submucosal invasion in endoscopically resected early colorectal carcinoma

Protein arginine methyltransferase‐5 (PRMT5), a major type II arginine methyltransferase, is an important epigenetic modifier with oncogene‐like properties because of its ability to repress the expression of tumor suppressor genes. We determined the correlations between PRMT5 expression or its cellular localization and malignant progression, with special reference to invasiveness, in colorectal adenomas and early colorectal carcinomas (CRCs). We performed immunohistochemical detection of PRMT5 in 108 endoscopically resected tissue samples (6 adenomas with low‐grade dysplasia, 34 adenomas with high‐grade dysplasia, 30 intramucosal carcinomas, and 38 submucosal invasive carcinomas). Early CRC (55 of 68, 80.9%) showed more frequent nuclear expression of PRMT5 than adenoma (15 of 40, 37.5%) (P < 0.001). Furthermore, high (strong staining in ≥ 50% of nuclei) nuclear expression of PRMT5 was more common in submucosal invasive carcinoma (21 of 38, 55.3%) than in intramucosal carcinoma (9 of 30, 30.0%) (P = 0.037). In conclusion, our data suggests that high nuclear expression of PRMT5 is a potentially useful marker for estimating submucosal invasion of early CRC in endoscopically resected specimens.     

The ductal phenotypic expression of the E-cadherin/catenin complex in tubulolobular carcinoma of the breast: an immunohistochemical and clinicopathologic study.

Tubulolobular carcinoma is a type of mammary carcinoma that displays an admixture of invasive tubules and lobular-like cells. Previous reports have shown it to share clinical similarities to lobular carcinoma, whereas more recent studies have shown it to be E-cadherin positive. The aim of the current study was to further explore the immunophenotype of tubulolobular carcinoma, and to document its natural behavior. Nineteen cases of tubulolobular carcinoma and 10 cases each of tubular and lobular carcinoma were retrieved for comparison analysis. Immunohistochemistry was performed with antibodies against estrogen receptor, progesterone receptor, HER2/neu, 34betaE12, E-cadherin, and the catenins. Twenty-five percent of patients with tubulolobular carcinoma presented with greater than stage I disease, compared to 0 and 60% of patients with tubular and lobular carcinoma, respectively. Two patients with tubulolobular carcinoma had tumor recurrence, one of whom also developed metastasis. The majority of all carcinomas were estrogen and progesterone receptor positive. E-cadherin displayed membranous staining in all tubular and tubulolobular carcinomas, and was negative in all lobular carcinomas. Half of each carcinoma subtype displayed granular cytoplasmic 34betaE12 immunoreactivity. alpha-Catenin exhibited partial or complete membranous staining in all tubulolobular and tubular carcinomas, and was negative in all lobular carcinomas. beta-Catenin displayed membranous staining in tubulolobular and tubular carcinomas, whereas all lobular carcinomas had coarse cytoplasmic immunoreactivity. p120 and gamma-catenin displayed membranous staining in 100% of tubulolobular and tubular carcinomas and cytoplasmic staining in 100% of lobular carcinomas. Tubulolobular carcinoma of the breast is thus a distinct type of mammary carcinoma that displays both tubular and lobular patterns histologically but displays the membranous E-cadherin/catenin complex characteristic of the ductal immunophenotype. Tubulolobular carcinoma appears to be more aggressive than tubular carcinoma, as 16% of patients had lymph node metastases, although all were alive at a mean follow-up of 40 months.     

Expression of mdm2 and p53 in epithelial neoplasms of the colorectum.

AIMS: To evaluate the respective roles of mdm2 (murine double minute 2) and p53 in the development of colorectal carcinoma. METHODS: Formalin fixed, paraffin wax embedded tissues from 72 sporadic adenomas and 55 carcinomas were investigated by means of immunohistochemistry for mdm2 and p53. RESULTS: mdm2 was expressed weakly in 17 of 72 (23.6%) adenomas and in 14 of 55 (25.4%) carcinomas. p53 was expressed in 19 of 72 (26.4%) adenomas and in 23 of 55 (41.8%) carcinomas. Four adenomas and five carcinomas showed positive staining for both proteins. Overexpression of p53 in adenomas was associated with moderate and severe dysplasia but not with tumour size. No associations were found between the expression of mdm2 and either the degree of dysplasia or tumour size. In carcinomas, neither the expression of p53 nor mdm2 correlated with Dukes's stage, metastasis, or differentiation. No associations were found between the expression of p53 and mdm2 in either adenomas or carcinomas. CONCLUSIONS: Although mdm2 has been reported to be an oncogene, it does not appear to play a major role in the development of colorectal carcinoma.     

p53 protein expression in colorectal adenomas: an immunohistochemical study using an antigen retrieval system

The immunohistochemical expression of the p53 gene product was examined in 91 colorectal adenomas from patients without (group 1,50 cases) or with (group 2,41 cases) concurrent sporadic colorectal carcinoma, and in 15 additional cases of randomly selected carcinomas from group 2 patients. Immunohistochemical reactions were performed with the DO-7 monoclonal and the CM1 polyclonal antibodies, following microwave irradiation of the tissues in an antigen retrieval solution, and the proportion of the immunoreactive cells was semiquantitatively assessed. p53 protein immunoreactivity was present in 46.1% (42, of 91, i.e., 20 out of 50 of group 1 and 22 out of 41 of group 2) and 33% (30 of 91, i.e. 14 out of 50 of group 1 and 16 out of 41 of group 2) of the adenomas using DO-7 and CM1 antibody, respectively. High p53 expression (i.e. immunolabelling of more than 30% of the tumour cell nuclei) was found in 13.2% of the adenomas (12 of 91, i.e. three out of 50 of group 1 and nine out of 41 of group 2; P= 0.025 using the X² test) using the DO-7 antibody, and in 6.6% of the cases (six of 91, i.e. two out of 50 of group 1 and four out of 41 of group 2) using the CM1 antibody. In carcinomas, 80% of the cases (i.e. 12 of 15) were found to express p53 protein with both antibodies. p53 immunoreactivity in colorectal adenomas increased with the degree of dysplasia: only five (17.8%) of the 28 adenomas with mild dysplasia were found to be DO-7 positive, while all of them remained CM1 negative. From the 50 adenomas exhibiting moderate dysplasia, 28 (56%) were DO-7 positive, and 22 (44%) were CM1 positive. Finally, from the 13 adenomas with severe dysplasia, nine (69.2%) and eight (61.5%) were found to be positive with the DO-7 and the CM1 antibody, respectively. Our results indicate that an increased number of group 2 adenomas express p53 protein, when compared with group 1 adenomas, and suggest that a strong correlation exists between p53 protein expression and the degree of dysplasia in colorectal neoplasms.     

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 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.     

β-Catenin expression and allelic loss at <Emphasis Type="Italic">APC</Emphasis> in sporadic colorectal carcinogenesis

beta-catenin is involved in E-cadherin-mediated cell adhesion, intracellular signal transduction, and also interacts with adenomatous polyposis coli (APC) protein. We previously found that 31% of colorectal adenomas and 84% of carcinomas showed reduced membranous staining of beta-catenin, while 46% of adenomas and 79% of carcinomas displayed beta-catenin nuclear expression. Importantly, a reciprocal relationship between reduced membranous and increased nuclear beta-catenin expression was demonstrated in the development from adenoma to carcinoma. To clarify whether this relates to an abnormality of the APC gene ( APC), we have now studied allele loss in microdissected tissues from 74 adenomas and 21 carcinomas (sporadic cases, previously immunostained for beta-catenin) by analysis of the microsatellites D5S346, D5S82 and D5S299. Fifty-five tumors (57.8%) showed allele loss at APC (no difference between adenomas and carcinomas). Thirty-one of these 55 (31/55, 56.4%) displayed both increased nuclear localization and reduced membranous staining of beta-catenin, and thirteen tumors (13/55, 23.6%) manifested either nuclear expression without changes in membranous expression or reduced membranous staining without nuclear expression (9 and 4 cases, respectively), while 11 (11/55, 20.0%) preserved normal membranous expression. Adenomas and carcinomas showing both nuclear and reduced membranous expression of beta-catenin, compared with those with normal membranous expression, tended to show allele loss ( P<0.01). In addition, 24 (24/95, 25.6%) tumors showed a change in the pattern of beta-catenin expression, but did not exhibit allele loss. These results suggest that although there may be a number of mechanisms responsible for changes in beta-catenin expression in colorectal tumors, dysfunction of APC may be the major cause of this phenomenon.