Immunocytochemical demonstration of p21ras in normal and transitional cell carcinoma urothelium

Activation and/or overexpression of the protein product of the ras gene family (p21^ras) has been implicated in the development of various cancers, including bladder carcinoma. We have used the anti-p21^ras monoclonal antibody, RAP-5, to assess the level and pattern of expression in formalin-fixed, paraffin-embedded tissue sections of both normal and malignant urothelium. All 14 random normal bladder biopsies and 67 of 68 transitional cell carcinomas of the urinary bladder were positively stained with the RAP-5 antibody. In normal urothelium, p21^ras staining tended to be localized to the superficial cell layer. With increasing histological grade and/or depth of invasion of the tumour, a greater proportion of tissue sections demonstrated a staining pattern which was more uniform with respect to the different epithelial cell types. Serially diluting the primary antibody did not reveal any significant differences in the staining patterns observed. Despite the change in staining pattern with increasing grade, these results suggest that p21^ras expression by itself is not a useful indicator of the malignant phenotype.     

p21WAF1/Cip1 is associated with cyclin D1CCND1 expression and tubular differentiation but is independent of p53 overexpression in human breast carcinoma

p21^WAF1/Cip1 is an inhibitor of cdk/cyclin complexes, and thus regulates the cell cycle. p21 is also related to cell differentiation and is regulated by wild-type p53, although p53-independent regulatory pathways have been proposed. In order to analyse p21 expression as well as its relationship with p53 in human breast cancer, an immunohistochemical analysis was undertaken of 77 breast carcinomas, 16 of them with an in situ component; 30 adjacent normal tissue samples; and five non-neoplastic specimens. Forty-four infiltrating carcinomas (57 per cent) were p21-positive. Expression of p21 was also observed in pre-invasive lesions, whereas normal ducts were negative or focally and weakly positive. p21 expression was associated with high histological grade (II+III) (P-0·017) and poor tubule formation (P-0·002), and was significantly less frequent in lobular carcinomas (P-0·0001). p21 positivity also correlated with increased proliferation, but this seemed to be dependent on the histological grade. Twenty carcinomas (26 per cent) showed p53 overexpression, but this was not associated with p21 negativity, suggesting the existence of p53-independent mechanisms for p21 regulation in vivo. Cyclin D1^CCND1 expression was analysed in the same series and an association between p21 and cyclin D1 expression was found, since 23 of 26 cyclin D1-positive carcinomas were p21-positive (P<0·001 …). In conclusion, p21 is frequently overexpressed in breast carcinomas and this occurs in the early stages of neoplastic progression. This overexpression seems to be independent of p53 status and might be involved in cyclin D1 modulation. © 1998 John Wiley & Sons, Ltd.     

Studies of c-jun oncogene expression in human breast using a new monoclonal antibody,NCL-DK4

A new monoclonal antibody to human c-jun oncoprotein, designated NCL-DK4, has been produced. NCL-DK4 has been proved to be highly effective for use on formalin-fixed, paraffin-embedded tissues, enabling the study of c-jun expression at a cellular level in both normal and neoplastic human tissues. The expression of c-jun oncogene has been examined in normal, benign, and malignant breast tissues, and c-jun-specific immunoreactivity in carcinomas has been related to histological type, tumour grade, c-erbB-2, oestrogen receptor, progesterone receptor, and epidermal growth factor receptor expression. Normal and benign breast tissues showed c-jun-specific immunostaining, which was weaker and in fewer cells compared with the c-jun immunoreactivity observed in breast carcinomas. No relationship was found between the degree of immunostaining and the extent of proliferative changes in benign breast tissues. Ninety per cent of all breast carcinomas studied showed c-jun-specific nuclear staining. There were no statistically significant differences in the intensity of c-jun immunoreactivity among grade I, II, and III infiltrating ductal carcinomas. There was no significant relationship between c-jun oncoprotein expression and c-erbB-2, oestrogen, progesterone, and epidermal growth factor receptor immunoreactivity.     

Transferrin receptor expression in non-malignant and malignant human breast tissue

The expression of transferrin receptor by normal, pregnant and benign hyperplastic breast lesions and by breast carcinomas has been investigated immunohistochemically using two monoclonal antibodies directed against the receptor. Unlike a previous immunohistological study in which staining was confined to malignant breast, transferrin receptor has been detected in pregnant breast and in benign lesions as well as in all carcinomas examined. The latter showed variable reactivity but with staining of most cells in 70 per cent of cases. Although the expression of transferrin receptor in non-malignant conditions may be related to cell proliferation, as has been suggested from studies of activated cells, the extent of reactivity of carcinomas has shown no correlation with tumour characteristics such as differentiation and local tumour spread. It is therefore suggested that the immunologically active transferrin receptor of breast carcinomas may have significance other than that relating to proliferation. The finding that with some carcinomas differences in staining occurred between the two antibodies is a further illustration of the complexities of the nature of transferrin receptor.     

Immunohistochemical staining of ras oncogene product in neoplastic and non-neoplastic mesothelial tissues: Immunoreactivity for N-ras and lack of immunohistochemical staining for Ha-ras and K-ras

Immunohistochemical staining of 36 malignant mesothcliomas and 45 cases of non-neoplastsic mesothelium including 20 specimens with signs of hyperplasia were investigated using murine monoclonal antibodies directed against p21 ras protein, Ha-ras protein, K-ras protein, and N-ras protein. All cases of non-neoplastic mesothelium and the majority of the malignant mesotheliomas (78 per cent) showed cytoplasmic and often submembranous immunoreactivity in more than 50 per cent of the cells with both the pan-ras and N-ras antibody. No immunoreactivity was observed for Ha- and K-ras. There was no statistically significant difference with respect to immunoreactivity between neoplastic and non-neoplastic mesothelium or between the various mesothelioma subtypes.     

Alteration of stromal protein and integrin expression in breast—a marker of premalignant change?

Interactions between epithelia and the extracellular matrix are important in the modulation of cellular growth, differentiation, and motility. To investigate the possible roles of these interactions in the neoplastic process, this study examines the expression of the integrin subunits a2, a6, beta 1, and beta 4 and the stromal protein tenascin in 53 breast carcinomas, non-involved breast tissue from 21 of these cases, and 32 normal/benign cases. Frozen tissue and an indirect immunoperoxidase technique were used throughout. Linear staining in relation to the basement membrane was seen for all integrins in the normal/benign cases. The carcinomas showed complete loss of reactivity in 65 per cent of cases for a2, 80 per cent for a6 and beta 4, and 90 per cent for beta 1. Those showing reactivity displayed a diffuse cytoplasmic type of staining. The non-involved breast tissue showed linear basement membrane type staining with a2 and beta 1, but for a6 and beta 4 66 per cent of cases displayed reactivity identical to that of the corresponding tumour. For tenascin, band-like staining around ducts was seen in normal/benign cases, with a diffuse coarse reactivity in all carcinomas. Most non-involved cases stained as for normal breast. The altered a6 beta 4 integrin staining in non-involved tissue in cancerous breast may be an early event in the neoplastic process, and as such, may be of use as a marker of pre-malignant change.     

Epithelial (E-) and placentae (P-) cadherin cell adhesion molecule expression in breast carcinoma

Two members of the cadherin family of intercellular adhesion molecules are found in normal breast tissue: E- (epithelial) cadherin is present in both luminal and myoepithelial cells, whereas P- (placental) cadherin is confined to myoepithelium. There is experimental evidence that loss of E-cadherin is associated with increased invasiveness of malignant cells in vitro, which stimulated us to examine the presence and distribution of E- and P-cadherin in breast carcinomas by means of immunohistochemical staining. E-Cadherin was present in all in situ and invasive ductal carcinomas examined, although it had a patchy distribution and the staining was of variable intensity. However, in 83 per cent of invasive lobular carcinomas and all lobular carcinomas in situ there was complete loss of E-cauherin expression. In the remaining 17 per cent of invasive lobular tumours, E-cadherin appeared to have an abnormal distribution within the cytoplasm with variable expression on the cell membrane. P-Cadherin, by contrast, was absent from all benign breast luminal epithelium and 25 carcinomas of ductal and lobular type. It was found in only one carcinoma of lobular type. We suggest that loss of cell-cell adhesion mediated by E-cadherin plays a part in the characteristic morphology of lobular carcinomas.     

p53 Protein,PCNA staining,and DNA content in follicular neoplasms of the thyroid gland

Forty-nine follicular adenomas and 11 follicular carcinomas of the thyroid were investigated by immuno-histochemistry for the expression of p53 protein and proliferating cell nuclear antigen (PCNA). The DNA ploidy and the S-phase fraction (SPF) of the neoplasms were analysed by flow cytometry. Twelve adenomas (24 per cent) and six carcinomas (55 per cent) were DNA non-diploid (P=0·07). The carcinomas had a higher proliferation rate than the adenomas when assessed either by SPF size (median 9·9 per cent vs. 2·9 per cent, P=0·0003) or by PCNA staining intensity (P<0·0001). Some scattered nuclei in two (4 per cent) adenomas and in three (27 per cent) carcinomas stained positively for p53 (P=0·04). The two adenomas with positive staining for p53 were subserially sectioned, but no signs of invasion were found; both patients are alive and well 6 and 7 years after surgery. One of the two adenomas showing positive p53 nuclear staining was DNA aneuploid, and both were positive in PCNA staining, but their SPFs were low (2·1 and 3·3 per cent). We conclude that p53 protein expression is not confined to follicular carcinomas; scattered p53-positive cells may also be present in histologically and clinically benign follicular adenomas. Because both follicular adenomas and carcinomas may be DNA aneuploid and their SPF and PCNA staining distributions overlap, the distinction between follicular adenoma and carcinoma should still be based on histological criteria.     

Ras levels and metalloproteinase activity in normal versus neoplastic rat mammary tissues

We have previously reported that activatedras oncogenes can simultaneously switch on the metastatic phenotype and increased capability to degrade type IV collagen [36]. Here the relationship between c-H-ras, metalloproteinase expression and metastatic behavior was studied inN-nitrosomethylurea (NMU)-induced rat mammary carcinomas, which are known to possess activated c-H-ras. When comparing normal rat breast tissue to mammary carcinomas there was no direct relationship betweenras DNA levels and neoplastic changes. Furthermore, there were no consistent differences between metastatic and non-metastatic carcinomas, or between primary tumors and metastases. The NMU-induced rat mammary carcinomas expressed two major gelatinolytic metal-loproteinases (gelatinases) of 65 and 92kD, but only the 65kD gelatinase was detected in normal breast tissue and a rat fibroma. Type IV collagenolytic activity per 5 g of protein was two to three times higher in the mammary carcinomas than in the normal breasts, whereas the primary tumors did not differ from the corresponding metastases. This study shows thatras amplification is not necessary for development of the malignant or metastatic phenotype in the NMU-induced rat mammary carcinoma model. We have also found that induction of p21ras protein synthesis in a v-H-ras transfected NIH/3T3 (433) cell line, containing a glucocorticoid promoter, does not lead to an increase in metastatic capacity.     

Different proliferative patterns characterize different preinvasive breast lesions

The study of cell-cycle associated proteins Ki-67/MIB-1, bcl-2 and p53 could clarify some features regarding the early phases of neoplastic progression in the breast. An extensive immunohistochemical study was carried out of the expression of these markers in all kinds of preinvasive breast lesions and their collateral normal parenchyma, a type of analysis not previously reported. The specimens were 35 florid ductal hyperplasias (FDHs), 8 atypical ductal hyperplasias (ADHs), 12 well-differentiated intraductal carcinomas (WDICs), 20 intermediately differentiated intraductal carcinomas (IDICs), 14 poorly differentiated intraductal carcinomas (PDICs), 12 atypical lobular hyperplasias (ALHs), 12 type-A lobular carcinomas in situ (LCIS), 150 normal small-size ducts and 365 lobules. All FDHs, ADHs, WDICs, and lobular lesions showed low proliferation (Ki-67/MIB-1), bcl-2 positivity, and p53 negativity; all PDICs expressed high proliferation, while 85 per cent and 7 per cent were p53 and bcl-2 positive respectively; IDICs showed high proliferation (50 per cent), bcl-2 expression (70 per cent), and p53 positivity (30 per cent), but no correlation between the expression of these markers was observed. Independent of the type of collateral lesion and age of the patient, 90 per cent and 10 per cent of small ducts/lobules showed low and high proliferation and diffuse and low bcl-2 expression respectively; no p53 positivity was observed. The modulation of cell proliferation and apoptosis control in ductal lesions could be the expression of a progression from hyperplasia/WDIC to PDIC, in which IDICs represent the link, owing to their immunoprofile. An alternative purely speculative hypothesis is that the different immunoprofile of the preinvasive lesions reflects their different origin in normal breast parenchyma. Low proliferative or bcl-2 positive lobules could be the site of origin of the lesions maintaining this phenotype, namely FDHs, ADHs, WDICs and lobular lesions, while highly proliferative or bcl-2 negative lobules could be the site in which PDICs develop. Consequently, preinvasive breast lesions could express a different regulation of apoptosis control and proliferative activity from the very beginning, rather than a modulation during neoplastic progression. Copyright © 1999 John Wiley & Sons, Ltd.     

p21WAF1/Cip1 expression is associated with cell differentiation but not with p53 mutations in squamous cell carcinomas of the larynx

p21^WAF1/Cip1 is a recently identified gene involved in cell cycle regulation through cyclin-CDK-complex inhibition. The expression of this gene in several cell lines seems to be induced by wild-type, but not mutant, p53. p21^WAF1/Cip1 expression has been studied at both mRNA and protein levels in a series of 49 normal mucosae and squamous cell carcinomas of the larynx. A significant association was found between mRNA and protein expression in tumours (P<0·0001). p21^WAF1/Cip1 expression was strongly associated with squamous cell differentiation of carcinomas, because six of seven (86 per cent) undifferentiated carcinomas (grade 4) showed very low levels of p21^WAF1/Cip1 expression, whereas 41 out of 42 (98 per cent) carcinomas with squamous cell differentiation (grades 1–3) had normal or high levels of p21^WAF1/Cip1 expression (P<0·0001). In addition, p21^WAF1/Cip1 expression was topologically related to the squamous differentiation of tumour cells with a distribution similar to that seen in normal squamous epithelium. No correlation was found between p21^WAF1/Cip1 expression and the global S-phase of the carcinomas. p53 mutations (exons 5–9) were found in ten carcinomas with p21^WAF1/Cip1 expression, but no p53 mutations were detected in three p21^WAF1/Cip1-negative tumours. In conclusion, p21^WAF1/Cip1 expression is frequently upregulated in squamous cell carcinomas of the larynx and is associated with tumour cell differentiation. p21^WAF1/Cip1 expression in these tumours is independent of p53 gene mutations. © 1997 John Wiley & Sons, Ltd.     

The localization of the insulin-like growth factor receptor 1 (IGFR-1) in benign and malignant breast tissue

Insulin-like growth factors (IGFs) play an important role in normal cellular growth and development and have been implicated in the regulation of tumour growth. Two receptors are recognized, IGFR-1 and IGFR-2, of which one, IGFR-1, is a transmembrane heterodimer structurally similar to the insulin receptor. Studies using ligand-binding assays have suggested that the proportion of human breast carcinomas expressing IGFR-1 varies between 39 and 93 per cent and all suggest a lower level of IGFR-1 expression in benign mammary epithelia. As there is this variation between studies and since no study appears to have examined the immunohistochemical localization of IGFR-1 within breast tissue, a series of 79 infiltrating ductal carcinomas, 11 infiltrating lobular carcinomas, three cases of pure ductal carcinoma in situ (DCIS), seven fibroadenomas, and eight normal breast specimens have been studied utilizing the monoclonal antibody αIR3. IGFR-1 localized to the epithelial component of 90 per cent of the carcinomas, with only cytoplasmic (21 per cent), only membrane (5 per cent), or a mixture of both cytoplasmic and membrane (64 per cent) staining patterns. In some tumours, distinct basolateral distribution of the receptor was observed. Invasive lobular carcinoma showed significantly less labelling than ductal (P=0·0009). There was a significant correlation between the level of IGFR-1 immunostaining with both oestrogen receptor (P<0·001) and progesterone receptor (P=0·0018) positivity within the malignant group. All normal mammary epithelium showed strong labelling, which was often at an intensity matching that of the most strongly labelled carcinoma and occasionally visualized as basolateral staining of the luminal cells. Weak to moderate staining of endothelial cells was also observed. It is concluded that IGFR-1 immunoreactivity is found in the majority of breast carcinomas, where it correlates most closely with oestrogen receptor status. The high intensity labelling of normal cells seen in this study contrasts with the low levels inferred from ligand-binding-based techniques and emphasizes the importance of the morphological approach in the investigation of novel molecules. © 1997 John Wiley & Sons, Ltd.     

p21WAF1 expression and endocrine response in breast cancer

An immunocytochemical assay for the p53-regulated protein product of the WAF1/Cip1 gene, p21^WAF1 (p21), was developed and applied to archival primary breast tumour material from 91 patients whose subsequent recurrent disease was treated with assessable courses of endocrine therapy. Nuclear localization of p21 protein was observed in 76 (82·4 per cent) cases. Status cut-offs were established and 29 (31·9 per cent) were deemed negative, 39 (42·9 per cent) weakly positive, and 23 (25·3 per cent) strongly positive. p21 status was inversely correlated with p53 protein (p = 0·047) but did not relate to oestrogen receptor (ER) status, response to endocrine therapy, or time to further disease progression (TTP). Highly p21-positive patients had a significantly improved overall survival time (p = 0·020). Co-assessment of p21 and p53 subgroups revealed p21 + /p53 − patients to have good survival characteristics, whilst p21 − /p53+ patients did poorly (p = 0·008). The p21 − /p53− patients overall did intermediately well, but Ki67-defined cellular proliferation analysis of these revealed two subclasses: those with high proliferation and poor survival times resembling the p21 − /p53+ phenotype, and those with less proliferative tumours with good survival, similar to the p21 + /p53− group. The significance of these results is discussed in the light of recent research concerning the role of p21 and p53 in breast cancer aetiology. Copyright © 1999 John Wiley & Sons, Ltd.     

Expression of p27/kip1 is down-regulated in human prostate carcinoma progression

p27^Kip1 is a cyclin-dependent kinase inhibitor whose down-regulation has been observed in several tumour models, including breast, colorectal, and gastric carcinomas. The purpose of this study was to assess p27^Kip1 protein expression in normal and benign prostatic epithelia as well as the possible existence of abnormalities in prostate carcinoma progression. p27^Kip1 expression was immunohistochemically analysed in 51 normal tissue samples, 11 nodular hyperplasias (NH), 22 high-grade prostatic intraepithelial neoplasias (PIN), 56 localized prostate adenocarcinomas, and 19 metastases. Immunoblotting was performed in ten cases. Normal prostate epithelium and NH showed diffuse and intense p27^Kip1 nuclear expression in most cases. A significant p27^Kip1 down-regulation was observed in many carcinomas when compared with benign epithelium. Forty-seven cases (84 per cent) were low p27^Kip1 expressors (<50 per cent positive cells) and nine cases (16 per cent) were high p27^Kip1 expressors. p27^Kip1 down-regulation was also consistently seen in PIN. Fourteen out of 19 metastases (74 per cent) were low p27^Kip1 expressors. Six metastatic samples had their corresponding primary tumour analysed and three cases showed decreased expression in the metastasis. It is concluded that p27^Kip1 is constitutively expressed in normal and benign prostatic tissue. This expression is clearly down-regulated in neoplastic progression from the preinvasive lesions through invasive carcinoma and metastases and this therefore occurs in early stages of neoplastic transformation. Copyright © 1999 John Wiley & Sons, Ltd.     

Immunohistochemical study of D5 antigen (an oestrogen receptor related protein) in normal breast, benign breast disease, and mammary carcinoma in situ.

Patterns of staining with a monoclonal antibody which recognises D5 antigen (a 29,000 kD oestrogen receptor-related protein) were studied in seven normal and 76 benign breast biopsy specimens as well as in 12 cases of pure in situ mammary carcinoma. Staining in benign breast lesions was weak and heterogeneous when compared with that seen in most infiltrating carcinomas. In situ carcinomas showed an intermediate pattern of staining. The finding of only small foci of weak positivity for D5 antigen in normal and benign breast disease indicated that there are similarities between the expression of D5 antigen and the presence of oestrogen receptor protein in these tissues. A further similarity was seen with in situ carcinomas, which have been shown to have lower oestrogen receptor content than infiltrating carcinomas and a more heterogeneous staining pattern with D5 than is seen in infiltrating tumours. The importance of these findings remains to be evaluated because the precise nature of D5 antigen and its association with the oestrogen receptor molecule is not fully understood.     

Expression of gap junction proteins connexin 26 and connexin 43 in normal human breast and in breast tumours

Gap junctional intercellular communication (GJIC) has been proposed as a cellular mechanism for tumour suppression and there is experimental evidence in support of this. If aberrant GJIC contributes to the formation of human breast tumours, one might expect that the connexins (gap junction proteins) expressed by epithelial cells in normal human breast would be down-regulated in tumour epithelial cells, or that tumour cells might show aberrant expression of other connexin family members. This study examines the immunocytochemical expression of connexins 26 (Cx26) and 43 (Cx43) in normal human breast, 11 benign breast lesions, two special-type carcinomas, and 27 invasive carcinomas of no special histological type (NST). Cx26 generally was not expressed at detectable levels in normal human breast, but punctate Cx43 immunostaining of the myoepithelial cells was found. Cx43 staining of the myoepithelium was also a feature of the benign lesions and ductal carcinoma in situ (DCIS). In general, the epithelial cells of benign lesions failed to stain for either connexin. Similarly, a lobular carcinoma did not express Cx26 or Cx43, but there was punctate Cx43 in the epithelial cells of a mucoid carcinoma. Cx26 was up-regulated in the carcinoma cells of 15 of the 27 invasive NST carcinomas, although the staining was usually cytoplasmic and heterogeneous. Cx43 was expressed by stromal cells, possibly myofibroblasts, in all NST carcinomas. Furthermore, there was heterogeneous Cx43 expression in the carcinoma cells of 14 of the 27 NST carcinomas and the staining was often intercellular and punctate, characteristic of functional connexins. Up-regulation of Cx26 and/or Cx43 in the carcinoma cells of over two-thirds of invasive lesions of NST is not necessarily inconsistent with a tumour suppressor role for GJIC. However, the role of gap junctions in the formation and progression of solid human tumours is likely to be more complex than indicated from experimental systems. © 1998 John Wiley & Sons, Ltd.     

Immunohistochemical analysis of p53 protein overexpression in normal,premalignant, and malignant tissues of the cervix uteri

Two hundred and thirty-eight cervical lesions ranging from normal to malignant were examined for overexpression of p53 protein. Whereas p53 protein was identified in 62 per cent of invasive squamous cell carcinomas, 11 per cent of invasive adenocarcinomas, and 7 per cent of squamous cell carcinomas in situ, no staining was found in adenocarcinoma in situ, dysplastic tissue, condyloma, and normal tissue. In 9 per cent of the positive cases of invasive squamous cell carcinomas. 5-50 per cent of the tumour ceiis were immunoreactive for p53 protein, whereas the other positive specimens were characterized by only rare p53-positive cells. We conclude that in invasive cervical carcinomas widespread overexpression of p53 protein is unusual, but occasional positive nuclei can be found frequently. Furthermore, our results indicate that altered expression of p53 protein may be involved in the progression of cervical carcinomas.     

Immunocytochemical demonstration and significance of p21 ras family oncogene product in benign and malignant breast disease

It has been suggested that the immunocytochemical demonstration of the p21 ras oncogene product is a useful marker of malignancy in breast disease. We have studied the reactivity of a series of specimens of benign and malignant breast disease with the anti ras p21 monoclonal antibody Y13-259, and shown widespread positive staining in both benign and malignant (including metastatic) disease as well as in adjacent 'normal' epithelium. In addition some staining of stromal cells as well as nerve fibres was observed. Our results suggest that the presence of ras p21 protein as demonstrated by this antibody is not a useful marker of malignancy or of proliferating epithelium but is rather a normal feature of certain cell types.     

Distribution of p21ras in postimplantation rat embryos

Expression of ras cellular oncogenes during the early postimplantation period in the rat was investigated using immunohistochemistry to p21^ras was used in an indirect avidin-biotin-peroxidase (ABC) technique. Positive staining indicating the presence of p21^ras was found in embryos from 6.5 to 12 days embryonic age. In early egg cylinders (6.5 days), positive staining for p21^ras was observed on the ectoplacental cone, primitive ectoderm and trophectoderm, while primitive endoderm and parietal endoderm appeared paler. In later egg cylinder stages (7.5 days), strong positive staining was observed in the primitive embryonic ectoderm and ectoplacental cone, but parietal and visceral endoderm still appeared to be devoid of positive staining. As development proceeded during primitive streak stages, the visceral and parietal endoderm became positively stained. By 10 days, all tissues appeared to be positive for p21^ras, with strong staining appearing in the heart and neural elements. Therefore, p21^ras does not appear to be ubiquitous in the rat conceptus prior to gastrulation, but shows differential distribution, appearing later in endodermal derivatives. Possibly p21^ras is involved in determination of the ectodermal and endodermal lineages.© Willey-Liss, Inc.     

Type 1 protein tyrosine kinases in benign and malignant breast lesions

Aims : To determine their significance, we examined the expression pattern of the four epidermal growth factor receptor (EGFR) family members as well as the phosphotyrosine kinase activity in breast tumour tissues.  

Methods and results

Fifty-three malignant breast tumours, four breast cancer cell lines, and 10 benign breast tumours were investigated. Fifty-three per cent (28/53) of the malignant tumours expressed EGFR protein, and the majority of these positive tumours were strongly positive. Eighty per cent (8/10) of the benign tumours also expressed EGFR protein, but all in a lower or moderate level. An association between EGFR expression and increasing malignancy grade was found in the group of infiltrating ductal carcinomas. Of the malignant tumours, 35.8% (19/53) expressed c-erbB-2 protein and 17% (9/53) c-erbB-3 protein, while no expression of c-erbB-2 and c-erbB-3 proteins was found in the benign tumours. Contrary to previous reports, we observed c-erbB-4 receptor protein to be less expressed in the malignant breast tumours. The 'normal' breast epithelial cells adjacent to the malignant tumours and the benign tumours demonstrated intensified membrane staining for c-erbB-4, while a number of the malignant tumours demonstrated a weak cytoplasmic staining or were negative. However, several malignant tumours with strong membrane staining for the c-erbB-4 protein were also found. No simple association between the expression of the four receptors and phosphotyrosine kinase activity was found.  

Conclusion

Our study has revealed a complex expression pattern of the EGFR family members in breast tumour cells. While the data about EGFR, c-erbB-2, c-erbB-3 and phosphotyrosine are largely in line with what has been reported, we found the c-erbB-4 protein expression to be decreased in the malignant tumours.