Genetic heterogeneity in sporadic colorectal adenomas

The majority of colorectal cancers develop from adenomatous polyps under the influence of factors that are still poorly understood. Tumourigenesis is generally considered a multistep process in which multiple genetic alterations occur, eventually reflected in abnormalities of the cellular DNA content. Macroscopical features such as tumour size and tumour architecture (tubular, tubulovillous, or villous) are correlated wit the chance of malignancy in the lesion. Grade of dysplasia can be considered an indicator for the level of progression of the adenoma towards invasive carcinoma. These characteristics were correlated with the presence or absence of K-ras mutations and the DNA ploidy in a prospective study performed on 46 large sporadic colorectal adenomas resected by endoscopy. DNA ploidy and K-ras mutations were analysed in two samples taken at distant sites in the adenomas. Aneuploidy was present in 12 adenomas (26 per cent) and K-ras mutations occurred in 26 (57 per cent). A highly significant correlation was found between aneuploidy and adenoma size, architecture, and grade of dysplasia. The presence of K-ras mutations was significantly correlated only with the size of the adenomas. The proportion of adenomas with aneuploidy and/or a K-ras mutation increased when two samples were analysed instead of one. This observation suggests that the prevalence of genetic mutations and of aneuploidy is probably underestimated, as generally only one sample is investigated. No correlation was observed between K-ras mutations and ploidy. This study demonstrates the presence of genetic heterogeneity in colorectal adenomas and supports the notion that K-ras mutation is an early event, while aneuploidy is a late event in the adenoma–carcinoma sequence. © 1997 John Wiley & Sons, Ltd.     

Immunohistochemical localization of c-erbB-2 protein and epidermal growth factor receptor in normal surface epithelium,surface inclusion cysts,and common epithelial tumours of the ovary

Summary The c-erbB-2 (HER-2/neu) protein is a membrane glycoprotein growth factor receptor showing molecular homology with the epidermal growth factor receptor (EGFR). We examined the immunohistochemical reactivity of monoclonal antibodies against both of these proteins in normal surface epithelium, surface inclusion cysts, and common epithelial tumours of the ovary. The ovarian tumours were classified as benign (16), borderline malignant (2), and malignant (19). Normal surface ovarian epithelium was weakly positve for both c-erbB-2 protein and EGFR. In surface inclusion cysts, however, the epithelial cells lining the lumen exhibited stronger staining for c-erbB-2 protein, but no staining for EGFR. All 16 benign ovarian tumours and the 2 borderline malignant ovarian tumours were positive for c-erbB-2 protein and negative for EGFR. Of the ovarian carcinomas, 13 of the 19 (68.4%) were positive for c-erbB-2 protein and negative for EGFR, while 4 showed positivity for both c-erbB-2 protein and EGFR. Two cases were negative for both proteins. Expression of both c-erbB-2 protein and EGFR was found in endometrioid carcinoma with squamous differentiation and in clinically advanced poorly differentiated serous carcinomas. Expression of c-erbB-2 protein appears to be increased and that of EGFR is reduced in the early stage of epithelial ovarian oncogenesis. The expression of EGFR with c-erbB-2 protein in ovarian carcinoma is related both to histological differentiation and/or advanced clinical stage.     

Amplification units and translocation at chromosome 17q and c-erbB-2 overexpression in the pathogenesis of breast cancer

 Hyperplasia without and with atypia is considered to be a precursor lesion for certain breast carcinomas. The cytogenetic events and the molecular pathology involved in the multistep process from normal to invasive carcinoma are unknown. To characterise the sequence of early genetic abnormalities of chromosome 17q and their biological consequences in the pathogenesis of breast cancer, we performed immunohistochemistry on 451 breast tissues including 180 normal breast specimens, 28 hyperplastic lesions without atypia and 44 with atypia, 100 cases of ductal carcinoma in situ (DCIS) and 99 cases of invasive ductal carcinoma. We correlated the overexpression of the c-ErbB-2 protein, the histological and the recently proposed differentiation classification of DCIS with the extent of DCIS. For fluorescence in situ hybridisation (FISH) analysis, different probes spanning the 17q region including the c-erbB-2 gene locus and those which are found adjacent, were used. Reverse painting and comparative genomic hybridisation (CGH) were performed on several breast cancer cell lines. c-ErbB-2 overexpression was observed in only 29% of DCIS and 23% of invasive carcinomas, but not in hyperplastic and normal tissue. c-ErbB-2 overexpression is correlated with poor differentiation in DCIS but not in invasive carcinoma. In DCIS, there was no correlation with the histological subtype classification. The average extent of DCIS is significantly increased from 13.81 mm in c-ErbB-2 negative cases to 29.37 mm in c-ErbB-2 positive cases. The increase was considered to be a possible consequence of the overexpression and is probably due to the previously described motility enhancing effect of the c-ErbB-2 protein. The histological and differentiation classification of DCIS did not correlate with the extent of disease. Using FISH, amplified genes at 17q12, always including the c-erbB-2 gene, were detected in all cases of DCIS and invasive carcinoma with c-ErbB-2 overexpression. The centromeric region and the NF1 locus, which is located between the centromere and c-erbB-2, were not amplified in any of the DCIS and invasive breast carcinomas, but co-amplification of the myeloperoxidase gene was detected in 3/5 DCIS and 1/5 invasive carcinomas with c-ErbB-2 overexpression. In contrast to c-erbB-2, immunohistochemical overexpression of their respective gene products was not observed. FISH, reverse painting and CGH show similar amplified genes with amplified c-erbB-2 in c-ErbB-2 overexpressing SK-BR-3 and BT474 human breast cancer cells. The amplified genes are part of two different amplicons. Extensive modifications of the 17q chromosomal region, caused by translocation, were also observed in these cell lines. It is concluded that the modifications of chromosome 17q, inducing overexpression of c-ErbB-2 protein, occur at the level of transition from hyperplasia to DCIS. They are preserved in invasive carcinoma with overexpression of c-ErbB-2 protein. This had led to the hypothesis that these modifications at 17q may lead to a larger extent of DCIS. Received: 23 July 1996 / Accepted: 9 December 1996     

Correlation between p53, c-erbB-2, and topoisomerase IIα expression,DNA ploidy,hormonal receptor status and proliferation in 356 node-negative breast carcinomas: prognostic implications

Various new prognostic indicators have been identified for mammary carcinomas, but the issue of their significance remains unsettled. The prognostic impact of p53, c-erbB-2, and topoisomerase IIα expression was investigated in relation to standard prognostic factors for carcinomas of the breast and to the tumour cell growth fraction. Paraffin-embedded specimens of 356 node-negative infiltrating ductal carcinomas were stained immunohistochemically using a polyclonal antiserum to c-erb B-2, and the monoclonal antibodies DO-1 (p53), Ki-S4 (topoisomerase IIα), and Ki-S5 (Ki-67). The patients were followed for a median duration of 99 months. Both p53 and c-erb B-2 were significantly associated with high tumour grade, large tumour size, DNA aneuploidy, lack of steroid hormone receptors, young age, and increased topoisomerase IIα and Ki-67 expression levels. The correlation of p53 and c-erb B-2 was not significant. Topoisomerase IIα and Ki-67 scores closely paralleled each other, indicating that both reflect the proliferative activity of tumour cells. A univariate analysis of overall (OS), specific (SS), and disease-free survival (DFS) revealed all the above-mentioned parameters to be statistically significant except patient age, which was relevant only to overall survival. Multivariate analysis with inclusion of all covariates selected tumour size and proliferation (topoisomerase IIα and Ki-67) indices as independent predictors of survival in all three models. No additional information was gained by p53 or c-erb B-2. It is concluded that the proliferative activity, as assessed by topoisomerase IIα or Ki-67 immunostaining, is the most useful indicator of breast cancer prognosis, except for tumour size. Copyright © 1999 John Wiley & Sons, Ltd.     

C-erbB-2 immunoexpression in parathyroid tumors and hyperplasias

C-erbB-2 is a proto-oncogene previously implicated in the pathogenesis and prognosis of several human tumors. The authors investigated c-erbB-2 immunoexpression in parathyroid tumors and hyperplasias, and correlated its presence with the diagnosis and severity of the parathyroid lesions. One hundred two parathyroid tissues (28 adenomas, 12 primary hyperplasias, 57 secondary hyperplasias, and 5 carcinomatous tissues) were studied. Membrane c-erbB-2 (either in the cell membrane or on the border of pseudocysts) was absent in normal glands, and detected in 50% of the adenomas, 25% of the primary hyperplasias, 100% of the carcinomas, and 12 and 53% of the secondarily diffuse and nodular hyperplasias, respectively. C-erbB-2 expression was significantly lower in diffuse hyperplasias than in other parathyroid lesions (P<0.05). Cytoplasmic c-erbB-2 expression (restricted to oxyphil cells) was found in 50% of the normal tissues and in variable frequency in parathyroid lesions. Mean gland mass and intact parathyroid hormone levels were not significantly different according to c-erbB-2 immunodetection. Mean serum ionized calcium was higher in c-erbB-2-positive adenomas than in negative ones (P=0.006). In conclusion, c-erbB-2 protein is frequently detected in hyperproliferative conditions of the parathyroid, such as neoplasms and hyperplasias.     

Molecular pathology of ovarian carcinomas

 There is evidence that ovarian cancer may be derived from the progressive transformation of benign and/or borderline tumours. Mutations involving different oncogenes and tumour suppressor genes accumulate during the process of malignant transformation, and the alterations of genes involved in the pathogenesis of familial ovarian cancer are probably early events in ovarian tumorigenesis. BRCA-1 and BRCA-2 act as classical tumour suppressor genes in hereditary tumours, but their role in sporadic tumours remains controversial; however, a high frequency of allele losses in BRCA-1 (17q) and BRCA-2 (13q) loci has been observed in both familial and sporadic tumours. The possible role of mismatch repair genes and microsatellite instability is also controversial, but a role for them has been proposed in borderline tumours. Mutations in K-ras are specific for mucinous tumours and may be related to mucinous differentiation. Finally, a role in tumour progression has been proposed for both c-erb B-2 and p53, but their practical value in prognosis remains questionable. Received: 29 May 1997 / Accepted: 2 April 1998     

“Low-risk” and “High-risk” HPV-infection and K-ras Gene Point Mutations in Human Cervical Cancer: A Study of 31 Cases

To analyze the coexistence of human papilloma virus (HPV) infection and K-ras gene activation in cervical neoplasia, we investigated 31 (seven pre-invasive and 24 invasive) cervical carcinomas for “low-risk” (types 6 and 11) and “high-risk” (types 16 and 18) HPVs and K-ras point mutations using PCR-based technology. “Low-risk” HPVs were not detected in the group investigated; however, 20 of 31 (64%) cases were HPV 16 positive, while HPV 18 was found in only three (9.7%) samples (HPV 6/11 v. HPV 16/18, p < 0.0001; HPV 16 v. HPV 18, p < 0.0001; Fisher's exact test). There was a K-ras codon 12 point mutation in two of 31 (6.4%) neoplasms, with none of the cases showing a K-ras codon 13 point mutation. Two moderately differentiated squamous carcinomas showed K-ras exon 2 gene alterations. Interestingly, none of the pre-invasive cervical carcinomas displayed K-ras gene point mutations. The mean patient age did not differ significantly in the number of HPV-positive and -negative cases. A coexistence of “high-risk” human papillomavirus DNA with K-ras gene alterations was observed in three of 31 (9.7%) neoplasms (one IIA and two IB moderately differentiated cervical carcinomas). Our results suggest that “high-risk” HPVs coexist with K-ras gene alterations in a subset of moderately differentiated carcinomas of the cervix uteri.     

The sequential accumulation of genetic alterations characteristic of the colorectal adenoma–carcinoma sequence does not occur between gastric adenoma and adenocarcinoma

We screened 30 gastric adenomas and 72 gastric adenocarcinomas for four genetic alterations (mutations of the K-ras, APC, and p53 genes and loss of heterozygosity at the DCC genetic locus) which are known to occur during colorectal tumourigenesis. We used polymerase chain reaction (PCR) single-strand conformation polymorphism analysis to detect mutations. Loss of heterozygosity (LOH) at the DCC locus was ascertained directly by performing PCR on the variable number of tandem repeats within the gene. Mutations of the K-ras gene were not detected in any gastric adenoma or carcinoma. APC mutations were detected in 20 per cent (6/30) of the adenomas but in only 1·4 per cent (1/72) of the carcinomas. In contrast, the p53 gene was frequently mutated in carcinomas (35 per cent; 25/72), but not in adenomas. LOH at the DCC locus was a frequent occurrence in carcinomas (58 per cent; 11/19 informative cases) but was infrequent in adenomas (14 per cent; 1/7). Alterations of the p53 and DCC genes occurred frequently both in differentiated and in undifferentiated gastric carcinomas. The considerable differences in the incidences of genetic alerations between gastric adenoma and carcinoma indicate that the sequential development of gastric carcinoma from adenoma is uncommon in gastric carcinogenesis.     

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.     

Salivary duct carcinoma—a highly aggressive salivary gland tumour with overexpression of c-erB-2

The clinicopathological and immunocytochemical features of nine cases of salivary duct carcinoma are described. This relatively rare tumour, which only recently has been widely recognized as a separate entity, is highly maligant and caused the death in eight of the patients. The tumour cells are arranged in cribriform and solid growth patterns, where the solid tumour nests frequently have comedo necrosis, and a fibrous, often sclerotic, stroma is present. The infiltrating desmoplasmic component and the diffuse invasive growth into adjacent adipose parotid tissue have similarities to ductal breast carcinoma. Immunocytochemical investigationof salivary duct carcinoma showed constant overexpression of c-erbB-2 as detected by membrane accentuation, and high proliferative activity as detected by nuclear positivity for MIB 1 (Ki-67). Changes in the expression of p53 and retinoblastoma gene product do not constitute a constant event event in salivary duct carcinoma. A few of the tumours showed scattered cells with distinct nuclear positivity for both progesterone and oestrogen receptors. We emphasize that this highly malignant salivary gland tumour has a characteristic morphology, may not be as rare as previously considered, and that prompt and aggressive therapy is needed.     

Expression and prognostic value of c-erbB-2 oncogene product in human phaeochromocytomas

Aims: Amplification of c-erbB-2 proto-oncogene has been reported in endocrine tumours, but the results were unclear and no predictive prognostic value has been established in the case of phaeochromocytoma. We investigated the immunohistochemical expression of c-erbB-2 oncogene in 34 cases of human phaeochromocytoma (27 sporadic, seven familial type MEN (multiple endocrine neoplasm)) in order to find out if it could be used to differentiate sporadic and familial forms and whether c-erbB-2 expression is related to tumour biological behaviour. Methods and results: All the cases showed diffuse, generally heterogeneous, intracytoplasmic granular c-erbB-2 staining. The percentage of tumour cells expressing c-erbB-2 was used as the comparative variable. The percentage of c-erbB-2 positive cells had a statistically significant (P < 0.001) relationship with tumour aggressiveness, as manifested by the presence of distant metastasis or association with other malignant neoplasms. We also found significantly higher levels (P = 0.007) of c-erbB-2 overexpression in MEN phaeochromocytoma than in sporadic cases. Conclusions: These results clarify the important role of c-erbB-2 proto-oncogene in the pathogenesis of human phaeochromocytoma and confirm the unfavourable prognostic significance of c-erbB-2 expression.     

Expression of p53 protein in benign epithelial hyperplasia,atypical ductal hyperplasia,non-invasive and invasive mammary carcinoma: an immunohistochemical study

To clarify whether p53 protein expression is involved in multistep carcinogenesis or the progression of mammary ductal carcinoma, we investigated p53 protein expression in 83 invasive ductal carcinomas (IDC), 10 IDC with a predominant intraductal component, 13 non-invasive ductal carcinoma (NIDC), 16 atypical ductal hyperplasia (ADH) and 39 benign epithelial hyperplasia (EH), using immunohistochemistry. Expression of p53 protein was detected in 24 (28.9%) cases of IDC, 5 (50%) cases of IDC with a predominant intraductal component and 1 (7.6%) case of NIDC. No expression was observed in either ADH or EH. In IDC, including cases with a predominant intraductal component, p53 protein expression was associated with a higher histological grade (P<0.0001) or mitotic index (P<0.0005). Although overexpression of c-erbB-2 protein has also shown a similar association with these prognostic indicators, expression of p53 protein correlated regardless of the status of c-erbB-2 overexpression. Completely coordinated expression of p53 protein was seen in both intraductal and invasive components. The intraductal component in IDC including cases with a predominant intraductal component which expresses p53 protein had significantly higher histological grade (P<0.0005) or more comedo-subtypes (P<0.0001). These results suggested that p53 protein expression occurs at a stage of NIDC with high histological grade or in comedo-subtypes. Its expression is maintained throughout invasion.     

p53 anderbB-2 protein overexpression are associated with early invasion and metastasis in bladder cancer

Overexpression of p53 anderbB-2 was studied by immunohistochemistry in formalin-fixed tissue samples of 179 patients with transitional cell carcinoma of the urinary bladder. p53 immunostaining was strongly correlated with tumour stage (P<0.0001). This was driven by a marked difference in p53 expression between pTa (37% positive) and pT1 (71%) tumours, while there was no difference between pT1 and pT2-4 tumours. Similarly, a strong overall association between p53 expression and grade (P<0.0001) was driven by a marked difference between grade 1 (28%) and grade 2 tumours (71%), and there was no significant difference between grade 2 and grade 3 tumours. Surprisingly, the frequency oferbB-2 overexpression was higher in pT1 tumours (74%) than in either pTa (49%;P=0.0265) or pT2-T4 (56%;P=0.0645) tumours. Both p53 anderbB-2 expression was also associated with metastasis. Metastases were found in 77% of patients with p53 positive primary tumours, but in only 50% of the patients with p53 negative primary tumours (P=0.022). Metastases were found in 66% of patients witherbB-2 positive primaries, but in only 37% of theerbB-2 negative primaries (P=0.020). Of 32 patients with positivity for both p53 anderbB-2, 84% developed metastases, as compared to 49% of patients with positivity for either one or neither positive (P=0.002). We conclude that both p53 anderbB-2 over-expression are associated with early invasion in bladder cancer. Furthermore, p53 anderbB-2 may be important predictors for metastasis.     

p53 mutations and expression in breast carcinoma in situ

The p53 tumor suppressor gene is altered in approximately half of human cancers. Although p53 mutations are common in invasive breast carcinoma, few have been identified in breast carcinoma in situ (intraductal breast carcinomas). Most studies of p53 in breast carcinoma in situ are immunohistochemical studies of p53 staining in paraffin-embedded tissue sections. Few studies have isolated the tumor cells and subjected them to DNA sequence analysis. The current study was undertaken to characterize p53 in a cohort of breast carcinoma in situ cases, both with and without invasive disease. Fifty-eight frozen breast biopsy samples were used for these investigations. Twenty-seven cases had only ductal carcinoma in situ (CIS) and 31 cases had evidence of both invasive and in situ carcinoma. DNA sequence alterations in exons 2 through 11 of p53 were screened by the single-strand conformational polymorphism technique. Exons with altered mobility were sequenced. Among breast CIS cases without invasive disease, 22% had p53 mutations and 7% had DNA sequence alterations of unknown significance. Analysis of breast CIS with concurrent invasive disease demonstrated p53 mutations in 19% of cases and one (3%) DNA alteration of unknown significance. Each carcinoma having a p53 mutation in the breast CIS component had the identical mutation in the invasive component of the same tumor indicating a clonal relationship between the two tumor components. p53 protein overexpression was identified in 22% of pure intraductal breast carcinomas and in 35% of breast CIS with invasive disease. Comparison of immunostaining and DNA sequence alterations showed a significant association between overexpression and mutations (P = 0. 0037) in cases of CIS without invasion, and similarly between overexpression and mutations in cases of CIS with invasion (P = 0. 007). p53 mutations and p53 overexpression were relatively common in intraductal breast carcinomas but were not observed in adjacent normal breast lobules or ducts in 9 cases available for DNA analysis. The frequency of p53 alterations when comparing breast CIS with and without an invasive component indicated that p53 mutations usually occur before invasion during the progression of breast cancer, as is observed for a number of other adult solid tumors.     

p53 but not erbB-2 expression is associated with rapid tumor proliferation in urinary bladder cancer

Tumor proliferation in bladder cancer is associated with tumor behavior. To assess the association between Ki-67 labeling index (LI), p53, and c-erbB-2 overexpression, formalin-fixed tissue samples of 160 patients with transitional cell carcinoma (TCC) of the urinary bladder were studied by immunohistochemistry. Ki-67 LI was strongly associated with tumor stage (P < .0001), tumor grade (P < .0001), and p53 status (P = .0014) but not with erbB-2 overexpression (P > .2). Ki-67 LI was higher in p53-positive tumors (19%) than in p53-negative tumors (14%) when all stages were compared. Ki-67 LI was independent of p53 expression in pTa tumors (p53-positive, 9%; p53-negative, 11%), showing that p53 overexpression alone is not sufficient to induce rapid tumor cell proliferation in pTa tumors. Ki-67 LI also was independent of p53 expression in pT2 to pT4 tumors (p53-positive, 20%; p53-negative, 23%), indicating that p53 expression is not necessary for rapid tumor cell proliferation in advanced stages. However, there was a striking difference in Ki-67 LI between p53-positive pT1 tumors (22.0% ± 8.8 standard deviation [SD]; n = 20) and p53-negative pT1 tumors (9.7 ± 8.3 SD; n = 22; P = .0001). These results suggest that increased proliferation in p53-positive pT1 tumors is caused by additional alterations that occur during tumor progression.     

Intratumor Cellular Heterogeneity and Alterations in ras Oncogene and p53 Tumor Suppressor Gene in Human Prostate Carcinoma

To assess the potential role of ras oncogene activation and P53 tumor suppressor gene mutations in the development of human prostate carcinoma, nine cases of histologically heterogeneous prostate tumors obtained from total prostatectomies were probed for these specific events. Each tumor was divided into 5 to 10 areas according to different growth or histological patterns. Targeted DNA sequences coding for ras and p53 were amplified by the polymerase chain reaction, analyzed by single-strand conformational polymorphisms, and confirmed by direct DNA sequencing. Point mutations of the ras gene were found in three of the nine tumors. Two contained K-ras codon 13 and H-ras codon 61 mutations, found in only one and three areas of each lesion, respectively. The third tumor contained two different point mutations in K-ras codons 13 and 61 in different foci of the sample. Loss of heterozygosity at the polymorphic codon 72 in the p53 gene was detected in two of four informative cases (50%) showing fragment cleavage by restriction fragment length polymorphism analysis. Mutations in p53, missense transversions, single base insertions, and two base deletions were also detected in three tumors. The present results reveal mutated ras and p53 occasionally occurring in small foci of the tumor and that genetic mutations in p53, as opposed to those in ras, are more closely associated with invasive growth of heterogeneous prostate carcinoma.     

Lowp53 protein expression in salivary gland tumours compared with lung carcinomas

Summary Fifty-one salivary gland tumours (23 pleomorphic adenomas, 5 Warthin's tumours, 12 mucoepidermoid carcinomas, 7 adenoid cystic carcinomas, 3 undifferentiated carcinomas and 1 acinic cell tumour) and 27 lung carcinomas (18 squamous cell carcinomas, 6 adenocarcinomas and 3 small cell carcinomas) were analysed immunohistochemically for the expression ofp53 nuclear phosphoprotein. Eight out of 51 (16%) salivary gland tumours werep53 positive. Three of these were benign and 5 malignant. All 3 benign salivary gland tumours were pleomorphic adenomas and expressed only occasional nuclear positivity with less than 1% of tumour cells positive. Of the 5p53-positive malignant tumours, 3 were mucoepidermoid carcinomas and 2 undifferentiated carcinomas. The malignant salivary gland tumours expressed more than 1% of positive nuclei in every case. Seventeen lung carcinomas werep53 positive (63%). Thirteen of these were squamous cell carcinomas, 3 were adenocarcinomas and 1 small cell lung carcinoma. The results show that mutations of thep53 gene may be infrequent in salivary gland tumours when compared with lung carcinomas. The relatively indolent course of some histological types of malignant salivary gland tumours could be associated with the preservation of the non-mutatedp53 gene in most of these tumours. The presence ofp53 positivity in some pleomorphic adenomas might, on one hand, suggest thatp53 gene alterations are also present in these tumours; on the other hand, the accumulation of thep53 protein in these tumours might also be due to some unknown mechanism, not necessarily related top53 gene mutation.     

Expression of E-cadherin and its relation to the p53 protein status in human breast carcinomas

 In breast carcinomas the TP53 gene is altered in 10–30% of cases. Alteration of the gene may lead to a general genomic instability, detected as deletions and/or amplifications at the gene level, and as altered expression at the mRNA and protein level. We have demonstrated a strong association between down-regulation of E-cadherin protein expression and alterations of the p53 protein, detected as TP53 gene mutation and/or protein accumulation in tumour samples from 210 patients with breast carcinomas (P <0.001). Investigation of allelic imbalance using microsatellite markers located near the E-cadherin locus was also performed. A higher frequency of loss of heterozygosity in the microsatellite marker closest to the E-cadherin locus was observed in samples with down-regulation of E-cadherin protein expression. A higher frequency of down-regulation of the E-cadherin protein expression was found in invasive lobular carcinomas than in invasive ductal carcinomas, although this difference was of borderline significant (P=0.084). Cases in the present series were also immunostained for c-erbB-2 protein overexpression. A significant association between p53 protein accumulation and cerbB-2 protein overexpression was seen (P=0.036). The results of the present study indicate that p53 protein may play a role in regulation of E-cadherin protein expression. Received: 29 May 1997)Accepted: 10 June 1997