Antibody for detecting p53 protein by immunohistochemistry in normal tissues

Expression of Hematopoietic Stem and Endothelial Cell Markers in Canine Hemangiosarcoma

Several chemicals and pharmaceuticals increase the incidence of hemangiosarcomas (HSAs) in mice, but the relevance to humans is uncertain. Recently, canine HSAs were identified as a powerful tool for investigating the pathogenesis of human HSAs. To characterize the cellular phenotype of canine HSAs, we evaluated immunoreactivity and/or messenger RNA (mRNA) expression of markers for hematopoietic stem cells (HSCs), endothelial cells (ECs), a tumor suppressor protein, and a myeloid marker in canine HSAs. Neoplastic canine cells expressed EC markers and a myeloid marker, but expressed HSC markers less consistently. The canine tumor expression results were then compared to previously published immunoreactivity results for these markers in human and mouse HSAs. There are 2 noteworthy differences across species: (1) most human HSAs had HSC marker expression, indicating that they were comprised of tumor cells that were less differentiated than those in canine and mouse tumors; and (2) human and canine HSAs expressed a late-stage EC maturation marker, whereas mouse HSAs were negative, suggesting that human and canine tumors may retain greater differentiation potential than mouse tumors. These results indicate that HSA development is variable across species and that caution is necessary when discussing translation of carcinogenic risk from animal models to humans.

Evaluation of epithelial dysplasia adjacent to lip squamous cell carcinoma indicates that the degree of dysplasia is not associated with the occurrence of invasive carcinoma in this site

BACKGROUND

We analyzed the different grades of dysplasia in the epithelium adjacent to lip squamous cell carcinoma (LSCC), as a parallel to actinic cheilitis (AC) that suffered malignant transformation.

METHODS

Forty samples of epithelium adjacent to LSCC were histologically graded according to the World Health Organization (WHO) and the binary systems. The expression of mutated p53 was evaluated through immunohistochemistry.

RESULTS

According to WHO system, 37.5% of the cases were graded as mild, 45% as moderate and 17.5% as severe dysplasia (P = 0.09). Considering the binary system, 90% of the cases were classified as low-risk and 10% as high-risk lesions. Mutated p53 was present in 73.3% of mild, 88.8% of moderate and 71.4% of severe dysplasia cases. Considering the binary system, 80.5% of the low-risk and 75% of high-risk lesions were immunopositive; 62.5% expressed the protein in both tumor cells and adjacent epithelium; 17.5% in adjacent epithelium only, and 7.5% in LSCC islands only (P = 0.03).

CONCLUSIONS

We observed heterogeneous grades of epithelial dysplasia in the epithelium adjacent to LSCC, which indicates that the analysis of AC morphological features is insufficient to predict patient's prognosis and to determine a treatment decision. Positive expression of mutant p53 in mild dysplasia reinforces this idea.

The C-terminal region of the hepatitis B virus X protein is required for its stimulation of HBV replication in primary mouse hepatocytes

Hepatitis B virus (HBV) infection is an important risk factor for hepatocellular carcinoma (HCC). The hepatitis B virus X protein (HBx), a multifunctional regulatory protein encoded by HBV, is known to be involved in stimulation of viral replication by modulating cell cycle status. HBx is required for maximal virus replication in plasmid-based replication assays in immortalized human liver HepG2 cells and in primary rat hepatocytes. Moreover, the C-terminal region of HBx is important for HBV replication in HepG2 cells. However, in normal hepatocytes, the region of HBx that is responsible for its effect on cell cycle regulation and HBV replication is unclear. We have demonstrated that HBx is similarly required for maximal HBV replication in primary mouse hepatocytes and that the C-terminus of HBx is essential for its ability to stimulate HBV replication by inducing quiescent hepatocytes to exit G0 phase of the cell cycle but stall in G1 phase. Our studies establish that primary mouse hepatocytes support HBx-dependent HBV replication, and provide further evidence for the effect of the C-terminal region of HBx on HBV infection and replication.

Increased p53 immunoreactivity in proliferative inflammatory atrophy of prostate is related to focal acute inflammation

Proliferative inflammatory atrophy (PIA) of prostate has been proposed as a precursor lesion of prostate cancer. The aim of the current study was to evaluate the expression of p53 protein in PIA lesions and to investigate the relationship between p53 staining and Ki-67, glutathione S-transferase-pi (GSTP1) and cyclooxygenase-2 (COX-2) immunohistochemical expression. The results revealed that p53 nuclear immunostaining appeared in PIA lesions in 2.1+/-3.4% (mean+/-SD) of the basal and 0.9+/-2.3% of the luminal epithelial cells. Both these values were significantly higher than those in normal-appearing acini (p<0.0001). Increased p53 expression in luminal cells was related to focal infiltration of polymorphonuclear leucocytes. A positive correlation between p53 expression and Ki-67 was found in COX-2-positive PIA lesions (r=0.610, p<0.0001). Half of the p53-positive epithelial cells expressed diffuse GSTP1 immunostaining in the same lesions. The present study demonstrates an increased p53 expression in PIA lesions, and inflammation, especially acute inflammation, may play a role in the induction of p53 over-expression, particularly as cells in PIA lesions are known to have a reduced defence against DNA damage.

Morphological and immunohistochemical characterization of isolated tumor cells by p53 status in gastrointestinal tumors

BACKGROUND AND AIMS

Isolated tumor cells (ITCs) in cancer patients are retrieved mostly using immunohistochemistry with antibodies directed against antiepithelial antigens (for example Ber-EP4), which are supposed not to be present in metastatic-free tissue. To date, there has been ongoing controversy whether those cells have biologic significance and are linked with tumor progression and impaired patient's prognosis. Therefore, the aim of this study was to further characterize Ber-EP4-positive cells in various tissues, with special emphasis on their tumorigenic origin.

MATERIALS AND METHODS

The frequency and prognostic impact of ITCs in lymph nodes displayed by means of monoclonal antibody Ber-EP4 were evaluated in retrospective (n = 292) and prospective (n = 100) collectives of various gastrointestinal carcinomas free of metastatic disease in conventional histopathology (pN0). Furthermore, the frequency of ITCs in the peritoneal cavity and bone marrow was analyzed in case of absence of overt distant metastasis (pM0) in the prospective collective. Ber-EP4-immunoreactive cells were further characterized for tumorigenic origin using morphological criteria and immunohistochemical double staining for Ber-EP4 and p53.

RESULTS

Ber-EP4-positive cells could be revealed in lymph nodes in 44.3% of pN0-gastrointestinal carcinomas, in the peritoneal cavity in 19%, and in the bone marrow in 10%. In lymph nodes, BerEP4-immunoreactive cells exhibited a metastatic-atypical morphology in 59%; however, it was always typical for true tumor cells in the peritoneal cavity or bone marrow. The cumulative 5-year survival rate was adversely affected by Ber-EP4-immunoreactive cells in uni- and multivariate analysis, irrespective of the underlying cell morphology (68% for Ber-EP4 negative, 41% for Ber-EP4 positive with atypical and typical morphology each). In the case of a p53-positive primary tumor, 70% of the corresponding ITCs also overexpressed p53, while the remainder was deemed p53 negative (p = 0.002).

CONCLUSION

ITCs detected by the antiepithelial antibody Ber-EP4 are present in a substantial proportion of apparently tumor-free lymph nodes. These cells impair patients' prognoses, irrespective of the underlying cell morphology. As approximately one third of Ber-EP4-positive cells in p53-positive primary tumors do not overexpress p53; their true tumorigenic origin needs to be further investigated.

Evaluation of p53, bcl-2, and interleukin-15 levels in gingival crevicular fluid of cyclosporin A-treated patients

BACKGROUND

Apoptosis plays an important role in the maintenance of tissue homeostasis. Considering that apoptosis mediators may play a role in the pathogenesis of drug-induced gingival overgrowth, this study was conducted to evaluate p53, bcl-2, and interleukin-15 (IL-15) levels in gingival crevicular fluid (GCF) of cyclosporin A (CsA)-treated patients.

METHODS

Twenty renal transplant patients exhibiting CsA-induced gingival overgrowth and 15 systemically healthy gingivitis patients were included in the study; 15 systemically and periodontally healthy volunteer subjects served as the healthy control group. GCF samples were obtained from one interdental site with gingival overgrowth (GO+) and one site without (GO-) from each CsA-treated patient; hyperplasia index, probing depth, papilla bleeding index, and plaque presence were recorded. One site from each gingivitis patient and healthy control was selected, GCF samples were obtained, and the same clinical parameters were recorded. GCF p53, bcl-2, and IL-15 levels were analyzed by enzyme-linked immunosorbent assay. The results were tested statistically.

RESULTS

p53 and bcl-2 levels were below the minimum detectable level in all GCF samples analyzed. CsA GO+ and CsA GO- sites, as well as gingivitis sites, exhibited significantly higher GCF levels of IL-15 compared to healthy controls (P<0.05). The difference between CsA GO+ sites and gingivitis sites was not statistically significant, although the total amount of IL-15 in CsA GO+ sites was lower than gingivitis sites (P>0.05). The total amount of IL-15 in CsA GO- sites was significantly lower than gingivitis sites (P<0.05). No significant correlation was found between the clinical parameters and GCF IL-15 levels (P>0.05).

CONCLUSIONS

The pathogenesis of CsA-induced gingival overgrowth is multifactorial. The findings of the present study indicate that IL-15 may play a role in the pathogenesis of CsA-induced gingival overgrowth due to its interactions with CsA and its role in apoptosis and inflammation.

p53 expression in normal paraffin-embedded tissue using different antibodies and antigen retrieval buffer systems

AIMS

The study was undertaken to demonstrate wild-type p53 in normal paraffin-embedded tissues using two widely used antibodies, DO7 and 1801 and two different antigen retrieval buffer systems.

METHODS AND RESULTS

Formalin-fixed paraffin-embedded normal tissue samples were obtained from the archives of the John Radcliffe Hospital, Oxford. Antigen retrieval was performed by microwaving using two different buffer systems: (i) the commercially available Dako target retrieval solution (Cat. no. 1699) (pH 9.8-9.9), (ii) freshly prepared buffer consisting of 0.1 m EDTA with 0.1% Tween pH 6.0, and (iii) freshly prepared buffer consisting of 0.1 m EDTA with 0.1% Tween pH 8.0. Staining was performed with DO7 and 1801 antibodies using the Dako Envision kit (peroxidase/DAB). DO7 antibody elicited strong nuclear staining in the mucosal cells of the small and large intestine, lymphoid cells, decidua, neurones such as Purkinje cells of the cerebellum, glandular epithelial cells and stromal cells of the prostate, cardiac myocytes and bronchial epithelial cells. Cytoplasmic staining was noted in Purkinje cells, glandular epithelium of prostate, exocrine pancreas and renal tubular epithelium. The 1801 antibody did not produce staining in any of these tissues.

CONCLUSIONS

Our study demonstrates the presence of p53 in normal paraffin-embedded tissue with nuclear and/or cytoplasmic localization in some instances. In our view, DO7 appears to be better suited for such detection.

Quantitative assessment of apoptotic and proliferative gingival keratinocytes in oral and sulcular epithelium in patients with gingivitis and periodontitis

BACKGROUND

Periodontal disease is caused by a chronic infection inducing an inflammatory reaction that leads to a breakdown of tooth-supporting tissue. The maintenance of an equilibrium between the host defence and microorganisms in the sulcus is essential to preserve health. All multicellular organisms have mechanisms for killing their own cells, and use physiological cell death for defence, development, homeostasis and ageing. Apoptosis and proliferation are very important phenomena in regulating this and a disturbance is often associated with disease e.g. cancer, AIDS, Alzheimer's disease, rheumatoid arthritis.

OBJECTIVE

The aim of this study was to determine whether the number of apoptotic and proliferative gingival keratinocytes differed between patients with gingivitis and those with periodontitis.

MATERIAL AND METHODS

The distribution of neutrophil elastase, PCNA/cyclin, DNA fragmentation (apoptosis) and p53 was determined with immunocytochemical techniques. We used paraffin-embedded sections from gingival biopsies and did quantitative analyses.

RESULTS AND CONCLUSION

These showed that 5-12% of the keratinocytes in the basal layers of the epithelium proliferated in the two groups. Fewer apoptotic cells were seen in the oral epithelium than in the sulcus in all subjects in both groups. Only in the most apical part of the sulcus, close to the junctional epithelium, did the number of apoptotic keratinocytes exceed the proliferative ones in patients with periodontitis.

p53 in nonneoplastic central nervous system lesions: an immunohistochemical and genetic sequencing study

OBJECTIVE

Immunostaining for p53 commonly is considered a marker of neoplasia. Previous studies of nonneoplastic processes have yielded conflicting results.

METHODS

To test the assumption that p53 immunoreactivity indicates neoplasia, we examined 60 formalin-fixed, paraffin-embedded biopsies of nonneoplastic central nervous system lesions, including gliosis (n = 12), infarction (n = 9), demyelinating disease (n = 23), progressive multifocal leukoencephalopathy (n = 11), and herpes simplex virus encephalitis (n = 5). Diffuse astrocytomas (n = 50) of World Health Organization Grades 2 to 4 also were studied, as were six control autopsy brains. The avidin-biotin-peroxidase complex method was used with commercially available monoclonal antisera to both p53 (clone DO7; Dako, Carpinteria, CA) and mdm2 (Dako), a protein known to stabilize p53. Two samples of each nonneoplastic lesion also were subjected to deoxyribonucleic acid isolation, amplification, and sequencing of exons 5 to 8 of TP53.

RESULTS

Although it was low level in most instances, p53 immunoreactivity was noted in all but normal control samples. In reactive lesions, staining was largely observed in astrocytes and histiocytes. Scant oligodendroglia also were labeled in demyelinating disease. The progressive multifocal leukoencephalopathy samples revealed exceptionally strong staining in astrocytes and infected oligodendrocytes. Staining also was noted in occasional endothelial cells and neurons, and in rare lymphocytes. Immunoreactivity for mdm2, studied only in nonneoplastic lesions, was moderate to strong in all cases and limited to reactive astrocytes and histiocytes. No TP53 mutations were noted in the nonneoplastic lesions studied. To some extent, all astrocytomas exhibited p53 immunopositivity, particularly high-grade lesions.

CONCLUSION

p53 immunoreactivity is not limited to astrocytomas, but it can be observed in lesions that often are mistaken for glioma. No TP53 mutations accompany p53 expression in nonneoplastic lesions, and mdm2 may be responsible for persistence of p53 expression in these processes.

c-erbB-2 and episialin challenge host immune response by HLA class I expression in human non-small-cell lung cancer

The role of major histocompatibility complex expression in cancer prognosis and pathogenesis is contradictory. The aim of the current study was to compare the expression of HLA class I molecules and of oncoproteins that may be sources of peptides presented by HLA class I antigens in non-small-cell lung cancer. For this purpose, the expression of HLA class I antigen and TAP-1 molecule (a transporter in the antigen-processing 1 transport protein) were studied with epidermal growth factor, receptor; c-erbB-2; episialin; wild-type and mutant p53; bcl-2 oncoprotein expression; and angiogenic factor expression (vascular endothelial growth factor and thymidine phosphorylase). The degree of lymphocytic stromal infiltration and of platelet-endothelial cell adhesion molecule-expressing lymphocytes was also studied. A strong association of c-erbB-2 and MUC1 (episialin) expression with HLA class I expression was observed (p = 0.005 and 0.009, respectively). Intense CD31-positive lymphocytic infiltration was also more frequent in HLA class I-positive cases (p = 0.05). Although there was no association of HLA class I expression with survival, loss of the HLA class I expression in MUC1 or c-erbB-2 overexpressing cases conferred a poorer clinical outcome (p = 0.04). Both c-erbB-2 and MUC1 are well-known targets of T-cell-mediated cytotoxicity and cell-cell or cell-matrix adhesion-regulating proteins. The authors provide evidence that the sequence of cell adhesion-disrupting oncoprotein expression, HLA class I induction, and enhanced epitope presentation followed by lymphocytic response is an important pathogenetic three-step sequence of events that define, in part, the clinical outcome in non-small-cell lung cancer.

Nuclear localization of human AP endonuclease 1 (HAP1/Ref-1) associates with prognosis in early operable non-small cell lung cancer (NSCLC)

The present study examined the immunohistochemical expression of human AP endonuclease 1 (HAP1/Ref-1), the major endonuclease in the repair of apurinic/apyrimidinic (AP) sites in cellular DNA, in normal lung and lung carcinomas. Cellular expression of HAP1 was determined using a standard avidin-biotin-peroxidase complex (ABC) technique and an anti-HAP1 rabbit polyclonal antibody on paraffin-embedded tissue sections from normal lung and in 103 primary non-small cell lung carcinomas (NSCLCs). In normal lung, the staining for HAP1 was found to be both nuclear and cytoplasmic in the pneumocytes of the alveoli. Superficial ciliated cells of the bronchial epithelium presented cytoplasmic staining, while staining for the basal cells was mostly nuclear. Bronchial glandular cells demonstrated mixed nuclear and cytoplasmic staining. Lung carcinomas showed all patterns of expression for HAP1. Loss of HAP1 expression was associated with low proliferation index (p=0.01) and with squamous histology (p=0.04). In squamous carcinomas, a significant correlation was observed between positive nuclear HAP1 and negative p53 expression (p=0.03). A survival benefit was seen in patients presenting nuclear HAP1 expression and those presenting the nuclear HAP1+/p53- phenotype (p=0.01 and 0.007, respectively). It is concluded that nuclear HAP1 localization may be relevant to its role as a DNA repair protein and/or to the recently proposed role as an activator of wild-type p53, and thus to the better outcome seen in this group of patients.

P53 and proliferating cell nuclear antigen (PCNA) expression in non-tumoral liver diseases

The tumor suppressor gene p53 is known to be involved in the negative regulation of cell growth. Proliferating cell nuclear antigen (PCNA), which is a nuclear protein and a component of the DNA replication process, is also involved in growth regulation. Both have been studied as progression markers in various tumors including hepatocellular carcinoma. In the present study, the aberrant p53 protein and PCNA expressions in non-tumoral liver diseases were investigated. Using monoclonal antibodies anti-p53 (D07-DAKO) and anti-PCNA (PC10-DAKO), 149 samples were stained, including 10 normal and 10 tumoral control liver tissues. p53 Overexpression was detected in 52 specimens (35%) whereas PCNA positivity was found in 96 (64%). There were 21 different pathological entities but most of the positive samples could be grouped into four types of diseases; namely, non-specific reactive hepatitis, steatohepatitis, chronic hepatitis and cirrhosis. Statistical analyses performed on these groups revealed that p53 positivity was found to be significantly higher in steatohepatitis (P < 0.05), while PCNA positivity did not show any statistical significance. The number of samples showing both p53 and PCNA positivity was 42 but their coexistence was not found to be significant. Certain cytological alterations like nuclear pleomorphism, steatosis and cholestasis, in addition to necroinflammatory activity, were evaluated for their possible impact on p53 and/or PCNA positivity. Necroinflammatory activity in steatohepatitis and steatosis in chronic hepatitis was found to be significant for p53 positivity (P < 0.05). In contrast, nuclear pleomorphism in non-specific reactive hepatitis was found to be significant for PCNA positivity (P < 0.05).

In situ detection of apoptosis at sites of chronic bacterially induced inflammation in human gingiva

Apoptosis is a key phenomenon in the regulation of the life span of terminally differentiated leukocytes. Human gingiva represents an established model to study immune responses to bacterial infection. In this investigation, we used the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) technique to evaluate presence and topographic location of apoptosis-associated DNA damage in human gingival biopsies along with the expression of the p53 and Bcl-2 apoptosis-regulating proteins. Qualitative data analysis showed high densities of cells expressing DNA damage and p53 both within the epithelial attachment to the tooth and in the perivascular infiltrate (infiltrated connective tissue [ICT]) immediately underlying the site of chronic bacterial aggression. Topographic consistency between DNA damage- and p53-positive cells was consistently observed. Quantitative analysis of the ICT showed mean densities of DNA damage- and p53-positive cells of 345 +/- 278 and 403 +/- 182 cells/mm2, respectively. Numerical consistency was confirmed by multivariate regression analysis: densities of DNA damage-positive cells were significantly predicted by densities of p53-positive cells (P = 0. 001, r2 = 0.84). In the ICT, cells displaying biotinylated DNA nicks were 3.8% +/- 2.7% of total cellularity, while p53- and Bcl-2-positive cells represented 4.4% +/- 1.7% and 15.4% +/- 6.7% of total cells, respectively. It is suggested that p53 expression associated with DNA damage is a prevalent phenomenon in chronically inflamed human gingiva, and that apoptosis may be a relevant process for the maintenance of local immune homeostasis at sites of chronic bacterial challenge in vivo.

p53, PCNA and Ki-67 expression in oral squamous cell carcinomas: the vagaries of fixation and microwave enhancement of immunocytochemistry

Proliferation markers are widely used as indicators of tumour progression and aggression. Fixation and antigen retrieval methods may enhance the immunocytochemical sensitivity of these markers but may also lead to loss of specificity. As these methods are often used quantitatively, standardisation of internal and external methodology is paramount. This study aimed to compare the effects of alcohol and formalin fixation and of microwaving on the immunocytochemical demonstration of p53, PCNA and Ki-67 in oral squamous cell carcinoma using duplicate tissue blocks from 24 cases. Both qualitative and quantitative differences in antigen expression were revealed. Whilst alcohol fixation alone at least maintained and usually increased the strength of positive staining, microwaving alcohol-fixed sections often gave rise to non-specific staining. p53 staining following microwave enhancement of alcohol-fixed tissue showed a significant incidence of conversion of negative results to positive and of positive staining in unexpected tissue components. Alcohol fixation increased the sensitivity of PCNA detection with a far less dramatic loss of specificity. The results emphasise the need for careful standardisation of immunocytochemical methods, particularly when used quantitatively and for inter-laboratory comparisons.

Endometrial carcinoma: immunohistochemically detected proliferation index is a prognosticator of long-term outcome

AIM

To test which immunohistochemically detected tumour parameters are predictive of outcome in endometrial carcinoma.

METHODS

A retrospective study of 300 patients diagnosed with endometrial carcinoma between 1980 and 1985, ensuring a follow up of at least 10 years. Paraffin wax embedded tissues from 236 patients with endometrial carcinoma were evaluated in terms of histological tumour type and grade, stage of disease, and certain immunohistochemical biological parameters. These parameters included the expression of oestrogen and progesterone receptors, the expression of p53 protein, the expression of the c-erbB-2 oncoprotein, and the expression of protease cathepsin D, together with the rate of cell proliferation.

RESULTS

Using univariate analysis, the following parameters correlated significantly with adjusted survival: histological type (p = 0.025), grade (p = 0.00003), FIGO stage (p < 0.00001), proliferation rate (p = 0.00002), oestrogen receptor expression (p = 0.007), progesterone receptor expression (p = 0.0092), and p53 expression (p = 0.00028). These parameters also correlated significantly with both disease free and overall survival. There was a weak correlation of cathepsin D expression with survival, but no correlation of c-erb B-2 expression with survival. Using multivariate analysis, only FIGO stage (p = 0.0021), histological grade (p = 0.005), and proliferation rate (p = 0.0007) remained statistically significant prognosticators of adjusted survival as well as of disease free and overall survival.

CONCLUSIONS

In addition to conventional histological parameters, the immunohistochemical determination of proliferative activity could contribute to the identification of a high risk subgroup of endometrial carcinomas. The other parameters tested were not of significant additional predictive value.

Detection of p53 in inflammatory tissue and lymphocytes using immunohistology and flow cytometry: a critical comment

AIMS

To analyse the expression of p53 in lymphatic cells found in inflammatory tissues and the peripheral blood by immunological methods.

METHODS

Immunohistological analysis of synovial tissues from patients with rheumatoid arthritis and flow cytometric analysis of peripheral blood lymphocytes were performed with anti-p53 antibodies from different sources.

RESULTS

The anti-p53 antibodies PAb240, PAb421, and PAb1801 from one supplier bound to the cytoplasm of lymphocytes, fibroblasts, and endothelial cells in rheumatoid synovial tissue, while the same anti-p53 antibodies from other sources and the p53 specific antibodies PAb1620 and DO1 were negative. Using flow cytometry, the antibodies that labelled cells in inflammatory tissues were shown to bind also to peripheral lymphocytes, while the antibodies that were negative in immunohistology did not react with peripheral blood lymphocytes. p53 expression could be confirmed by western blot in rheumatoid synovial tissue, but not in peripheral blood lymphocytes using PAb421 and PAb240 antibodies from our own laboratory, which had been negative in immunohistology.

CONCLUSIONS

Demonstration of p53 by western blot is more sensitive and reliable than immunohistology and flow cytometry. Western blot is the gold standard for the demonstration of p53 expression and should be used, whenever possible, to confirm p53 expression in normal tissue shown by immunohistology or flow cytometry. All other reports on p53 expression, especially those obtained using antibodies with an unusual staining pattern must be interpreted with caution.

Bcl-2 and p53 expression in node-negative breast carcinoma: a study with long-term follow-up

Bcl-2 and p53 gene products (Bcl-2, p53) are important regulators of apoptosis and cell proliferation, and their immunohistochemical expression may help to identify high-risk breast cancer patients. The authors evaluated p53 and Bcl-2 immunoreactivity in 178 node-negative breast cancers (NNBC) with long-term follow-up (median, 60 months). Bcl-2 was seen in 111 (62%) cases, and was significantly associated with small tumor size, nonductal morphology, low tumor grade, estrogen-receptor (ER) positivity, and p53 negativity. p53 overexpression (ie, > 15% reactive nuclei) was observed in 31 (17%) cases, and was associated with lower age, large tumor size, ductal morphology, high tumor grade, negative ER status, and lack of Bcl-2 immunoreactivity. In univariate analysis, the variables associated with short relapse-free survival (RFS) were large tumor size (P = .002), high histological grade (P = .01), high mitotic count (P = .03), and high Nottingham prognostic index (NPI) (P = .0002). In multivariate analysis (final model), only the NPI was of independent prognostic value concerning RFS.

Role of p53 immunohistochemistry in differentiating reactive gliosis from malignant astrocytic lesions

P53 immunohistochemistry has been used to distinguish between malignant tumors and morphologically similar benign processes. In the central nervous system, a major diagnostic dilemma is caused by overlapping features of benign reactive astrocytic lesions and low-grade astrocytomas, especially with small biopsies. P53 immunoreactivity in astrocytes could be useful in differentiating benign reactive lesions from malignant astrocytomas. An immunohistochemical study on 110 brain lesions from 108 patients using a monoclonal antibody (DO-7) against p53 protein was conducted. Using the modified Ringertz and World Health Organization system, the specimens included 22 astrocytomas, 12 anaplastic astrocytomas, 42 glioblastoma multiforme tumors, three nonglial tumors, and 56 reactive astrocytic lesions to 25 neoplasms, nine infectious processes, six cerebrovascular disorders,one metabolic disorder, two vascular malformations, eleven degenerative/demyelinating lesions, and two unknown primary lesions. Immunoreactive astrocytic tumors included 12 (54%) astrocytomas, nine (75%) anaplastic astrocytomas, and 38 glioblastoma multiforme tumors (90%). Among the reactive astrocytic lesions, only five (9%) cases of progressive multifocal leukoencephalopathy were immunoreactive. These data demonstrate that p53 immunoreactivity in astrogliosis is unusual but is to be expected in astrocytomas and can help to differentiate reactive from neoplastic astrocytic lesions.

Immunohistochemical detection of p53 in Wilms' tumors correlates with unfavorable outcome

The role of p53 in the pathogenesis and progression of Wilms' tumors is only partly understood. Although p53 mutations were initially reported only in anaplastic Wilms' tumors, we had reported that, of two of twenty-one cases that had a p53 mutation, one tumor showed no evidence of anaplasia. To determine the significance of p53 expression in all clinical stages of Wilms' tumor, twenty-eight cases were analyzed for p53 immunoreactivity. Paraffin sections were immunolabeled with two different monoclonal antibodies, recognizing both mutant and wild-type p53. Fifteen of sixteen tumors in the recurrent/metastatic group and three of twelve tumors in the nonmetastatic/nonrecurrent group showed p53 immunopositivity. Only one of three positive tumors in the latter group showed moderate to strong positivity, whereas twelve of sixteen metastatic/recurrent tumors revealed a similar degree of p53 positivity. The positivity was stronger in the metastasis/recurrences as compared with the corresponding primary tumor. Western blot analysis revealed p53 expression in all of the Wilms' tumors tested, suggesting its involvement in the development of Wilms' tumors. Single-strand conformation polymorphism analysis performed on twenty-three of these tumors revealed p53 mutations in four of fourteen recurrent/metastatic tumors and none in the nonmetastatic/nonrecurrent group. Our results show that, whereas 60% of cases were immunopositive for p53 protein, mutations were detected in only 16% of tumors, indicating that wild-type p53 protein is retained in the other tumors. We conclude that p53 immunopositivity strongly correlates with recurrence/metastasis in Wilms' tumors. Furthermore, the accumulation of p53 in these tumors is not only due to mutations but may also involve stabilization of normal p53 with other proteins.

p53 expression in odontogenic keratocyst epithelium

The expression of p53 protein was studied in odontogenic keratocysts (OKC, 11 solitary, 5 recurrent and 6 NBCCS cysts), radicular (RC, n = 5) and dentigerous (DC, n = 5) cysts, using a panel of antibodies to p53 (clone BP53-12, clone 1801 and polyclonal CM1) and a sensitive biotin-streptavidin method on paraffin embedded sections. Of the three antibodies tested, clone BP53-12 gave the most intense and consistent nuclear staining pattern. Clone 1801 and polyclonal CM1 stained only 38% and 71% OKC linings, respectively, but not RC and DC linings. However, BP53-12+ cells were detected in the epithelial linings of all cyst types. Quantification of BP53-12+ cells was performed by manual counting and by relating cell number to unit length of basement membrane as determined by TV image analysis. BP53-12+ cell counts in solitary OKC linings (25.5 +/- 11.0 cells/mmBM) were significantly greater than those in DC (9.3 +/- 4.9 cells/mmBM, P < 0.01) and RC (6.7 +/- 2.6 cells/mmBM, P < 0.01) linings. The epithelial distribution of positive cells in OKC was predominantly suprabasal, which also varied from that of DC and RC linings (P < 0.005). There were no detectable differences in BP53-12 reactivity between the different subtypes of OKC (i.e., solitary, recurrent and NBCCS-associated OKC; P > 0.1). When data for the NBCCS-related OKC group were excluded, there was a significant correlation (r = 0.55, P < 0.01) between p53 and Ki67 labelling. To detect the presence of p53 gene mutations, genomic DNA, extracted from paraffin sections of OKC (4 solitary, 2 recurrent and 4 NBCCS cysts), RC (n = 3) and normal oral mucosa (n = 1), was subjected to a combination of polymerase chain reaction and single-stranded conformation polymorphism (PCR-SSCP) analysis for exons 5-10 of the p53 gene. Exon 4 was not analysed because of compromised DNA quality. No abnormality in banding patterns was found and all samples gave results similar to DNA from known, sequenced, normal p53 gene controls. Absence of p53 mutations within exons 5-9 was confirmed by the direct sequencing of 2 fresh frozen OKC samples (1 solitary and 1 NBCCS cyst). These results suggest that overexpression of p53 protein in OKC epithelium, detected by immunocytochemistry, is not reflected by alteration of the p53 gene and presumably reflects overproduction and/or stabilisation of normal p53 protein.

Detection of p53 in Hodgkin's disease using the monoclonal antibody PAb248

The recent demonstration that the murine anti-p53 monoclonal antibody PAb248 can identify human p53 in a variety of normal tissues proves that immunohistochemical detection does not necessarily indicate the presence of mutations. PAb248 can detect p53 protein in a cytoplasmic-perinuclear localization, not previously described. The present study presents the expression of this antibody in a series of 34 cases of Hodgkin's disease, comparing it with the antibodies CM1, PAb1801, and PAb240. In all cases, PAb248 showed uniform cytoplasmic-perinuclear staining in small and medium-sized lymphocytes, while it was constantly negative in Hodgkin, Reed-Sternberg (R-S/H) cells, and variants. This pattern of staining was the opposite to that observed with the antibodies CM1, PAb1801, and PAb240, where the staining was nuclear and restricted to the R-S/H cells, with the small lymphocytes being negative. p53 can be found in different conformations and localizations, with the cytoplasmic-perinuclear localization mainly, although not exclusively, being found in normal and reactive tissues and the nuclear localization being mainly expressed by neoplastic cells. These results give further support to the theory that the R-S/H cells are the neoplastic population in Hodgkin's disease, while the surrounding lymphocytes are reactive.

Expression and prognostic significance of Bcl-2 in ovarian tumours

The expression of bcl-2 was studied in normal ovaries and in ovarian tumours by immunohistochemical analysis. Normal epithelium was strongly stained in all nine examined ovaries. In comparison, all tumour groups showed a substantially decreased tumour cell expression of the same order of magnitude. Thus, benign tumour cells were weakly stained in two and unstained in two samples, while the remaining eight showed strong expression. Of ten borderline samples, one was unstained and five had weakly and four strongly bcl-2 positive tumour cells. Finally, 24 of 50 malignant tumours showed strong staining, while weak or no expression in tumour cells was found in 16 and 10 samples respectively. The reduced staining deviated significantly from normal ovary for both borderline (P = 0.02) and malignant groups (P = 0.01). Tumour cell staining with the bcl-2 antibody was significantly reduced when tumour mass had to be left behind compared with those with no visible remaining tumour (P = 0.03 and 0.003 for weakly and strongly stained tumours respectively). The expression of bcl-2 in malignant tumour cells was inversely correlated with the expression of p53. Bcl-2 expression was correlated with survival with significantly reduced survival in weakly (P = 0.02) and unstained (P < 0.001) groups compared with those patients having strongly stained malignant tumour cells. This correlation between the presence of bcl-2 and survival was maintained in the subgroups of patients with advanced disease or with residual tumour bulk and was also the case in patients having p53-positive tumours. Our results indicate an inhibitory role of bcl-2 in development and progression of ovarian tumours.

The clinical significance of p53 aberrations in human tumours

p53 aberrations are the most common genetic alteration found in human tumours and this review summarizes the current understanding of the clinical significance of p53 abnormalities. Immunohistochemical and molecular techniques can demonstrate alterations at the protein and gene level, respectively, but with a significant discordance between the findings of either technique. The tumours evaluated in this review include cancers of the breast, lung, gastrointestinal tract, genitourinary tract, and others. In most cases, only data on p53 protein are available and in each of these tumour types discrepant conclusions on the clinical value of p53 abnormalities as prognostic indicators have been reached. The role of p53 in the context of anticancer adjuvant therapy has also been analysed. Experimental data suggest that p53 affects the apoptotic response to anticancer agents, but this has not yet been proven in a clinical series where this demonstration and its effect on therapy could represent one of the most important endpoints in p53 clinical research. The use of standardized techniques to evaluate p53 gene mutation and protein accumulation within controlled clinical series of patients entering prospective trials is essential to answer the many remaining questions on the clinical significance of p53 aberrations.

p53 gene mutations, p53 protein accumulation and compartmentalization in colorectal adenocarcinoma

p53 accumulation may occur in the nucleus and/or cytoplasm of neoplastic cells. Cytoplasmic accumulation has been reported to be an unfavorable, but not established, prognostic indicator in colorectal cancer. Different types of p53 intracellular compartmentalization could depend either on p53 gene mutations or on the interaction with p53 protein ligands. The purposes of our study were (1) to assess whether the different patterns of p53 accumulation are selectively associated with p53 mutations and (2) to evaluate the clinical significance of p53 mutations in colorectal carcinomas. We evaluated p53 gene mutations in colorectal carcinomas. We evaluated p53 gene mutations in exons 5 through 8, by polymerase chain reaction and single-strand conformation polymorphism analysis; p53 accumulation and intracellular compartmentalization were detected immunocytochemically with the antibodies PAb1801 and CM1. p53 mutations were found in 74 of 126 carcinomas (59%). Nuclear p53PAb1801 accumulation was associated with p53 gene mutations (P < 0.001) whereas cytoplasmic p53 CM1 accumulation was more likely to occur with the wild-type p53 gene (P = 0.048). Overall, 112 carcinomas (89%) displayed p53 gene mutations and/or p53 accumulations of any type. p53 mutations were not correlated with important clinicopathological parameters and were not related to patient survival. Our data suggest that mechanisms other than mutations may also play a role in inhibiting p53 tumor-suppressing functions in colorectal carcinomas. Cytoplasmic p53CM1 accumulation frequently does not depend on p53 mutations.

Heterogeneity in cell proliferation and expression of p53 and bcl-2 during the indolent phase of germinal centre cell lymphoma: an explanation for clinical variability

Germinal centre cell lymphomas (GCCL) show a wide range of clinical outcomes from persistent indolent disease to large cell transformation. To investigate possible mechanisms of this heterogeneity, a combined morphometric and immunohistological study of p53, bcl-2 and cell proliferation was carried out. There was wide variation in p53 expression between biopsies and between individual follicles in the same tumour. A similar pattern of variation was seen using the cell-cycle marker MIB1, but this did not correlate with p53 expression. Even in cases in which a t(14;18) was demonstrated by PCR, variation occurred in the number of cells expressing bcl-2. On the basis of these results, we suggest that the probability of the clonal expansion of GCCL tumour cells carrying additional genetic abnormalities depends on a complex interaction of cell proliferation with p53 and bcl-2 expression, and that this may account for variation seen in the clinical behaviour seen in this group of tumours.