On the expression of the p53 protein in human cancer

Nucleotide variants and protein expression of TP53 in a Sri Lankan cohort of patients with head and neck cancer

Head and neck cancer (HNC) is the leading cancer in Sri Lankan males and second most common cancer among Sri Lankan females. This is the first study, to the best of our knowledge, that has focused on investigating the association between TP53 somatic DNA variants, with p53 protein expression and risk factors in a cohort of Sri Lankan patients with HNC. A total of 44 patients with cancer and 20 healthy controls were studied. In total, 36 genomic DNA sequence variants were found, including several novel variants (two deletions in exons 4 and 6, two in the 3′ untranslated region and several intronic variants). A total of 14 tumour samples carried pathogenic TP53 mutations. A random selection of 24 samples was analysed immunohistochemically for p53 protein expression. All the samples with point missense variants were strongly immuno-positive, whereas, samples with nonsense and frameshift TP53 variants were immuno-negative for p53 immunohistochemical staining. Although, the human papilloma virus is a known risk factor for HNC, results from the present study identified an absence or lower level of infection in the Sri Lankan cohort.

Evaluating the association between p53 codon 72 Arg>pro polymorphism and risk of ovary cancer: a meta-analysis

Aim

Allelic polymorphism in codon 72 of the p53 tumor suppressor gene causes imbalance of p53 protein expression. Earlier studies have shown association between allelic polymorphism in codon 72 of the p53 gene with risk of ovary cancer (OC); however the results are inconclusive and conflicting. Therefore, we performed this meta-analysis to investigate the relation between p53 codon 72 Arg>Pro polymorphism and overall OC susceptibility.

Methods

We searched all eligible published studies based on the association between codon 72 of the p53 Arg>Pro polymorphism and risk of OC. Data were pooled together from individual studies and meta-analysis was performed. Pooled odds ratios (ORs) and 95% CI were calculated for allele contrast, homozygous, heterozygous, dominant and recessive genetic models.

Results

A total of twelve studies comprising of 993 OC cases and 1264 healthy controls were included in this meta-analysis. Overall, no significant association was detected for Pro allele carrier (Pro vs. Arg: p = 0.916; OR = 0.980, 95% CI = 0.677 to 1.419), homozygous (Pro/Pro vs. Arg/Arg: p = 0.419; OR = 0.731, 95% CI = 0.341 to 1.564), heterozygous (Arg/Pro vs. Arg/Arg: p = 0.248; OR = 1.237, 95% CI = 0.862 to 1.773), dominant (Pro/Pro+Arg/Pro vsArg/Arg: p = 0.699; OR = 1.089, 95% CI = 0.706 to 1.681), and recessive (Pro/Pro vs Arg/Arg+Arg/Pro: p = 0.329; OR = 0.754, 95% CI = 0.428 to 1.329) genetic models, respectively. Also, in the stratified analysis by ethnicity, no significant association of this polymorphism with risk of OC was found in the Caucasian population.

Conclusions

This meta-analysis suggested that codon 72 of the p53 Arg>Pro polymorphism may not significantly contribute in ovary cancer susceptibility. However, future large studies with gene-gene and gene-environment interactions are needed to validate these findings.

The consequence of oncomorphic TP53 mutations in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy, with an alarmingly poor prognosis attributed to late detection and chemoresistance. Initially, most tumors respond to chemotherapy but eventually relapse due to the development of drug resistance. Currently, there are no biological markers that can be used to predict patient response to chemotherapy. However, it is clear that mutations in the tumor suppressor gene TP53, which occur in 96% of serous ovarian tumors, alter the core molecular pathways involved in drug response. One subtype of TP53 mutations, widely termed gain-of-function (GOF) mutations, surprisingly converts this protein from a tumor suppressor to an oncogene. We term the resulting change an oncomorphism. In this review, we discuss particular TP53 mutations, including known oncomorphic properties of the resulting mutant p53 proteins. For example, several different oncomorphic mutations have been reported, but each mutation acts in a distinct manner and has a different effect on tumor progression and chemoresistance. An understanding of the pathological pathways altered by each mutation is necessary in order to design appropriate drug interventions for patients suffering from this deadly disease.

Role of p53 and p73 genes polymorphisms in susceptibility to esophageal cancer: a case control study in a northern Indian population

Genetic variants in p53 and in its homologue p73 may modulate Esophageal Cancer (EC) risk because they are supposed to influence cell cycle progression, apoptosis and DNA repair. Therefore, we aimed to evaluate the association of p53 intron3 16 bp duplication and p73 G4C14-to-A4T14 polymorphisms with susceptibility to EC in a northern Indian population in 255 EC patients and 255 age and sex matched healthy controls. We found that p53 intron3 16 bp duplication polymorphism was not associated with EC and its clinical characteristics. However, p73 G4C14-to-A4T14 polymorphism was associated with significant higher risk of EC (OR = 1.74, 95% CI = 1.16-2.60, P = 0.007) in an allele dose-dependent manner (P(trend) = 0.0047). Stratification of subjects on the basis of clinical characteristics showed that p73 AT genotype carriers were at significant increased risk of developing esophageal squamous cell carcinoma (OR = 1.78, 95% CI = 1.18-2.67, P = 0.006) at middle third tumor location (OR = 1.87, 95% CI = 1.18-2.97, P = 0.007) with lymph node metastasis (OR = 1.77, 95% CI = 1.04-3.02, P = 0.035). No interaction with environmental risk factors was observed with any of the studied polymorphisms. In summary, p73 G4C14-to-A4T14 polymorphism but not the p53 intron3 16 bp duplication polymorphism is associated with EC and its clinical characteristics in northern Indian population.

Two TP53 germline mutations in a classical Li-Fraumeni syndrome family

Li-Fraumeni syndrome (LFS) is an autosomal dominantly inherited cancer predisposition syndrome characterized by a combination of tumors including sarcoma, breast cancer, brain tumors, adrenocortical carcinoma and leukemia. Germline mutations in the tumor suppressor gene TP53 are associated with LFS. We present a family with LFS in which initially a novel germline TP53 intron 5 splice site mutation was found. A second germline TP53 mutation, the exon 7 Asn235Ser (704A-->G) mutation, was detected in this family through pre-symptomatic DNA testing. This latter mutation has been reported repeatedly in the literature as a pathogenic mutation involved in LFS. We provide evidence for pathogenicity of the novel intron 5 splice site mutation, whereas this evidence is lacking for the exon 7 Asn235Ser (704A-->G) mutation. Our findings emphasize the importance of performing additional tests in case of germline sequence variants with uncertain functional effects.

P53 and breast cancer

p53 mutation is the most common genetic abnormality found so far in human cancer, and in breast cancer p53 mutation/alteration is seen in up to 50% of primary carcinomas. Together with the increasing knowledge of the characteristics and understanding of the role of p53 over the last two decades, attention in recent years has been focused on how this knowledge can be used in clinical settings for patient care and management in terms of analyzing p53 as a potential marker for studying the relationship between p53 expression and tumour development, progression and outcome; and designing alternative treatment strategies specifically aimed at restoring normal p53 function.

Molecular epidemiology of plasma oncoproteins in vinyl chloride monomer workers in Taiwan

AIMS

To determine the presence of Asp13-p21-ki-ras oncoprotein and p53 oncoprotein in the plasma of vinyl chloride monomer (VCM)-workers in Taiwan.

METHODS

We used enhanced chemiluminescence (ECL) western blotting to detect Asp13-p21-ki-ras and ELISA to detect mutant p53 protein (p53-Ag) and anti-p53 antibodies (p53-Ab) in the plasma of VCM-exposed workers.

RESULTS

Twenty-five out of 251 (10%) VCM-workers were positive for Asp13-p21-ki-ras in plasma, but 0 out of 36 controls were positive. There were 15 out of 95 (15.8%) plasma-positives among the more highly exposed (> 480 ppm-month) workers and 10 out of 156 (6.4%) plasma-positives among the lesser exposed (< or = 480 ppm-month). Compared to the unexposed controls, age and drinking adjusted odds ratios (95% CI) were 1.2 (0.1, 9.8) in the lower exposed workers, and 4.8 (0.8, 28) in the higher exposed workers, and there was a significant linear trend between exposure and plasma positivity (P=0.001). Thirty-three out of 251 (13.2%) VCM-workers were positive for the p53 over-expression (10% with positive p53-Ag and 2.8% with positive p53-Ab). There was a significant association between cumulative VCM exposure concentration and positive p53 expression (P=0.032) among VCM-workers after adjusting for age, hepatitis, drinking and smoking status.

CONCLUSIONS

Asp13-p21-ki-ras oncoprotein and p53 over-expression (p53-Ag or p53-Ab) can be found in the plasma of VCM-workers in Taiwan, and a significant dose-response relationship exists between plasma oncoproteins expression and VCM exposure.

Oral non-Hodgkin lymphomas: studies of EBV and p53 expression

OBJECTIVES

The aims of the study were to assess sociodemographic and clinicopathologic characteristics of patients with oral non-Hodgkin lymphomas (NHLs) and the expression of Epstein-Barr virus (EBV) and p53.

MATERIALS AND METHODS

The clinical and pathologic features of 11 patients with oral NHLs were studied. The expression of EBV mRNA and p53 protein were studied by means of in situ hybridization and immunohistochemical methods in 11 formalin-fixed, paraffin-embedded specimens from these patients.

RESULTS

The patients' age ranged from 13 to 70 years with the mean of 42 years. Human immuno-deficiency virus (HIV) status was documented in five of the 11 patients and three were known to be HIV-positive. The most common locations were gingiva and alveolar mucosa. Pain and tenderness were major symptoms of the patients. The most common histologic subtype was diffuse large-cell, intermediate-grade NHL. Eight of 11 cases (72.7%) showed positive expression of p53 protein. Four of 10 cases (40%) expressed EBV-encoded RNA (EBER) transcripts. All known HIV-positive cases were EBV-positive.

CONCLUSIONS

The findings suggest that appropriately expressed p53 protein may play a role in tumorigenesis of oral NHLs. In addition, EBV may be involved with the pathogenesis of oral NHLs particularly in patients with HIV infection.

Critical residues of epitopes recognized by several anti-p53 monoclonal antibodies correspond to key residues of p53 involved in interactions with the mdm2 protein

The aim of this work was to study the reactivity of antibodies directed against the N-terminus of p53 protein. First, we analysed the cross-reactivity of anti-p53 antibodies from human, mouse and rabbit sera with peptides derived from human, mouse and Xenopus p53. Next, we characterized more precisely a series of monoclonal antibodies directed against the N-terminal part of p53 and produced by immunizing mice with either full length human or Xenopus p53. For each of these mAbs we localized the epitope recognized on human p53 by the Spot method of multiple peptide synthesis, defined critical residues on p53 involved in the interaction by alanine scanning replacement experiments and determined kinetic parameters using real-time interaction analysis. These antibodies could be divided into two groups according to their epitopic and kinetic characteristics and their cross-reactivity with murine p53. Our results indicate that critical residues involved in the interaction of some of these mAbs with p53 correspond to key residues on p53 involved in its interaction with the mdm2 protein. These antibodies could, therefore, represent powerful tools for the study of p53 regulation.

Plasma p53 protein and anti-p53 antibody expression in vinyl chloride monomer workers in Taiwan

Vinyl chloride (VC) workers are known to be at risk for development of angiosarcoma of the liver (ASL), a rare tumor. Previously, a study of p53 gene mutations in tumors of VC-exposed workers found that 50% of liver angiosarcomas contained such mutations. Mutant p53 oncoprotein and anti-p53 antibodies can also be found in the sera of ASL patients and VC-exposed workers without cancer. Workers in Taiwan have also been exposed to VC, and some have contracted liver tumors. In this study, we used enzyme-linked immunosorbent assays to detect mutant p53 protein and anti-p53 antibodies in the plasma of VC-exposed workers in Taiwan. Thirty-three of 251 (13.2%) VC-workers tested positive for the p53 overexpression (10% with positive mutant p53 protein and 3.6% with positive anti-p53) in their plasma, but only 2 of 36 controls (5.6%) tested positive (2.8% with positive mutant p53 protein and 2.8% with positive anti-p53). There was a significant association between cumulative VC exposure concentration and positive p53 expression (P = 0.032) among VC workers after we adjusted for age, hepatitis, drinking, and smoking status. In summary, P53 overexpression (mutant p53 protein or anti-p53 antibody) can be found in the plasma of VC workers in Taiwan, and a significant dose-response relationship exists between plasma p53 overexpression and VC cumulative exposure concentration.

Role of p53 tumor suppressor gene in pancreatic endocrine tumors of Chinese patients

OBJECTIVE

The molecular genetic of pancreatic endocrine tumor (PET) has rarely been studied in depth because of its rarity. The aim of this study is to determine if there is any implication of p53 overexpression on the pathogenesis and clinicopathological parameters of PET.

METHODS

This study examines the immunohistochemical expression of the p53 gene product in 52 PETs (32 insulinomas, three gastrinomas, two glucagonomas, one carcinoid, and 14 nonfunctional tumors) from Chinese patients (27 men, 25 women) collected over a 23-yr period. Of these, 21% were malignant.

RESULTS

Irrespective of their demographic data, clinical behavior, hormonal status, or pathological features, none of the 52 PETs showed p53 overexpression.

CONCLUSIONS

This observation, together with an analysis of the literature, suggests that p53 gene aberrations may not be important in the pathogenesis of PET.

Overexpression of p53 protein in cutaneous T cell lymphoma: relationship to large cell transformation and disease progression

The molecular mechanisms by which advanced cases of cutaneous T cell lymphoma (CTCL) (mycosis fungoides/Sezary syndrome) undergo large cell transformation (LCT) and develop the morphologic appearance of a large cell lymphoma, are undefined. We used immunohistochemical analysis and polymerase chain reaction/single strand conformational polymorphism to examine whether p53 mutations are associated with disease progression and LCT in CTCL. p53 protein immunohistochemistry was performed on 37 paraffin embedded biopsies from 27 patients with CTCL; LCT was present in 15 biopsies. Overexpression of p53 protein was found in 11 of 37 CTCL biopsies including 10 of 15 biopsies (67%) with LCT in which p53 staining was predominantly seen in large transformed cells. In contrast, p53 immunostaining was found in only one of 22 CTCL biopsies without LCT (p < 0.0004). Serial biopsies revealed acquisition of p53 expression following LCT in two patients in whom initial diagnostic biopsies without LCT were p53 negative by immunostaining. All p53 protein positive biopsies were from advanced lesions (cutaneous tumors or extracutaneous sites); none of 12 patch/plaque stage CTCL biopsies demonstrated p53 staining. Polymerase chain reaction/single strand conformational polymorphism and sequencing analysis of p53 exons 4-8 was performed in 11 cases where frozen tissue was available. No mutations were detected in six cases positive for p53 protein expression. These results suggest overexpression of p53 protein in LCT and disease progression of CTCL by a mechanism other than p53 gene mutation, in most cases.

p53 protein expression in nephroblastomas: a predictor of poor prognosis

Alteration of the tumour-suppressor gene p53 is the commonest genetic change encountered in human malignant tumours. A study was undertaken to ascertain the prognostic value of p53 immunoexpression in nephroblastomas. A series of 93 consecutive cases was analysed. Archival formalin-fixed, paraffin wax-embedded tissue sections were stained with monoclonal anti-p53 antibody (DO-7, Dako) using a peroxidase-labelled streptavidin biotin kit. Five of seven tumours (71.4%) with unfavourable histology, but only 3 of 86 favourable histology tumours, showed 'high' p53 immunoexpression (P < 0.001). p53 expression in unfavourable histology tumours was present in both anaplastic and non-anaplastic components. Moreover, there was uniform staining of blastema, epithelium and stroma in unfavourable histology tumours. No statistical difference in p53 expression was found between patients who had received and those who had not received preoperative chemotherapy (P = 0.678). Similarly, no statistical difference was found in the groups of patients who were disease free, who had residual/recurrent disease or who had died (P = 0.238). The mean survival period for patients with tumours that had 'low' and 'high' expressions was 24.8 months and 12.6 months respectively (P = 0.0003). In conclusion, p53 immunoexpression in nephroblastomas was found to be an important determinant of poor prognosis as it identifies those patients with a shorter survival period and also those with unfavourable histology tumours. It may also be of practical value to the practising pathologist by identifying those tumours that require careful assessment for the presence of anaplasia.

Is p53 a protein that predicts the response to chemotherapy in node negative breast cancer?

The role of p53 in modulating apoptosis has suggested that it may affect efficacy of anti cancer agents. For this reason, we have evaluated p53 alterations in 282 consecutive patients with infiltrating node-negative breast cancer who underwent primary surgery and were randomized either to CMF (Cyclophosphamide 400 mg/m2, Fluorouracil 400 mg/m2, and Methotrexate 40 mg/m2) or control arm (no adjuvant therapy) from 1980 to 1989. p53 alterations were analyzed by immunohistochemistry using DO7 MoAb, revealed by immunoperoxidase technique, and quantitated in term of percentage of positive cells. We observed a positive staining in 24% of the tumors. Among them, 10% had a positive staining in more than 75% of the cells. There was a highly significant association between the proportion of positive cells and histologic grade of the infiltrating ductal carcinomas (p<0.004). However, there was no association with age, tumor size, hormone receptor content, or vascular embolism. There was a trend but no significant relationship between positive staining and overall survival either in each arm of the trial or in the overall population. Interestingly, we observed a higher relative risk of local relapse after conservative therapy in the boosted area in the group of mutated p53 (RR=4.41; p<0.0005). We conclude that, in this node-negative breast tumor population, alteration of p53 cannot predict the response to the chemotherapy. However, it may represent a useful marker of risk of local relapse and of radio resistance.

Expression of p21 and mutant p53 gene products in residual prostatic tumor cells after radical radiotherapy

BACKGROUND

In a previous study, sextant core biopsies revealed residual tumor in the prostate in 37/55 investigated patients, with an average of 6.8 years after external beam radiation therapy (RRT). More than half of the biopsies exhibited Ki-67 and PCNA proliferation activity.

METHODS

The present study aims at further characterizing residual tumor cells post-RRT by investigating whether the tumor cells exhibit immunohistochemical expression of p21 and mutant p53 gene products, which reflect the state of cell cycle regulatory mechanisms.

RESULTS

Positive p53 staining was observed in 11% and p21 positivity in 47% of biopsies. The proportion of positively stained cells was low for both antigens. The staining patterns point to the existence of wild-type p53-dependent, as well as alternative pathways for p21 protein induction.

CONCLUSIONS

A low proportion of tumor cells exhibited p53 protein accumulation post-RRT. G1 arrest, as assessed by p21 immunoexpression, was demonstrated in a low percentage of tumor cells in < 50% of post-RRT biopsies, indicating that the vast majority of residual tumor cells following RRT escape the G1/S checkpoint control and propagate into S-phase, presumably with a maintained malignant potential.

Oral exfoliative cytology: review of methods of assessment

The use of oral exfoliative cytology in clinical practice declined due to the subjective nature of its interpretation and because there may be only a small number of abnormal cells identifiable in a smear. The more recent application of quantitative techniques, together with advances in immunocytochemistry, have refined the potential role of cytology, stimulating a reappraisal of its value in the diagnosis of oral cancer. This review considers the influence of the quantitative analysis of cytomorphology, DNA analysis and other tumour markers applied to oral exfoliative cytological samples. These studies indicate that oral cytology may provide an important adjunct in the assessment of the patient with a potentially cancerous oral lesion.

p53 over-expression in laryngeal carcinoma is not predictive of response to radiotherapy

It has been suggested that alteration involving the p53 gene may influence tumour response to radiotherapy. If this were so, then p53 overexpression (which is usually associated with p53 mutation and readily detectable in routine diagnostic pathology) may help determine the most appropriate form of cancer therapy. p53 expression was assessed in 90 formalin-fixed paraffin-embedded laryngeal carcinomas that were subsequently treated with radiotherapy. The polyclonal antibody DO1 (1 in 50 dilution) was used, together with an avidin-biotin immunoperoxidase technique, but in the absence of any additional antigen retrieval techniques. p53 expression was assessed and correlated with various clinicopathological parameters. Using Chi square analysis, no significant difference between p53 positive and p53 negative lesions was found for response to radiotherapy, as measured by survival and recurrence rates. Furthermore, no correlation with p53 expression was found for tumour size, nodal metastasis, sex, age, alcohol intake, tobacco habit and histological grade. This absence of correlation may in part be explained by discrepancies between immunohistochemical detection of p53 and p53 mutation, although the lack of predictive response to radiotherapy mimics that recently found for irradiated head and neck cancer cell lines.

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.

Correlation between p53 immunostaining patterns and gene sequence mutations in breast carcinoma

We performed p53 immunostaining in 82 invasive breast carcinomas by using two commercially available antibodies, one of which (DO7) was employed in formalin-fixed paraffin-embedded sections. The other antibody (PAb1801) was evaluated in corresponding acetone-fixed cryostat sections. A greater percent of cases were immunostained with DO7 compared to PAb1801 (52% vs 33%); however, the staining was more often heterogeneous (6-50% cells positive) or focal (< or = 5% cells positive) with DO7 (9% vs 31%). To investigate the genetic relevance of p53 immunostaining, single-strand conformational polymorphism (SSCP) analysis and DNA sequencing were performed on exons 2-11 by using archival tissue samples of 18 cases that were selected on the basis of certain immunostaining patterns. Two (33%) of six tumors with negative staining for DO7 had gene sequence mutations; however, one of these mutations was a base-pair deletion that caused a reading-frame shift and the other was a base-pair insertion that resulted in a stop codon. Both of these tumors exhibited immunostaining with PAb1801, although it was weak and cytoplasmic in one case. Conversely, three (30%) of 10 tumors showing immunoreactivity in 6-100% of cells with both reagents lacked a gene sequence mutation. Of the remaining seven tumors that were positive by SSCP, six contained a point mutation resulting in a base-pair substitution. Despite repeat analyses, one of the cases positive by SSCP failed to demonstrate a mutation in the sequenced exons. Four (80%) of five cases with heterogeneous DO7 immunoreactivity (that is, 6-50% of nuclei positive) were positive for gene sequence mutation. Neither of two cases showing focal DO7 nuclear staining in < 5% of tumor cells contained a mutation in the sequenced exons, and neither of these cases was strongly positive with PAb1801. Staining for either antibody was significantly associated with adverse outcome, as determined by disease recurrence at 52 months median follow-up (DO7, p = 0.01; and PAb1801 p = 0.002, chi-squared test). We conclude that a variety of factors may account for discrepancies when immunohistology is used to evaluate p53 status. These include fixation artifacts, differing epitope specificities of monoclonal reagents, presence of immunohistologically "silent" mutations and, possibly, aberrant overexpression of wild-type protein.

The clinical significance of p53 accumulation in gastric carcinoma

BACKGROUND

Alterations in the expression of p53 tumor suppressor protein is a frequent event in human cancer but the practical implications of this phenomenon are yet to be fully exploited. The objective of this study was to determine the value of p53 accumulation as a marker of tumor progression and prognosis of gastric carcinoma patients and to evaluate whether this parameter can be properly assessed prior to surgery.

METHODS

The expression of p53 was studied immunohistochemically in 200 gastric carcinomas using paraffin embedded surgical specimens and endoscopic biopsies. The correlation between p53 expression in tumor tissue, selected clinicopathologic variables, and the course of the patients' disease were analyzed.

RESULTS

Results showed that 42.5% of the gastric carcinomas expressed elevated levels of p53 protein. P53 accumulation positivity correlated with increasing tumor stage and size (P < 0.001 and P = 0.025, respectively). P53 positive tumors had a higher propensity for lymph node and distant metastases (P < 0.001). P53 accumulation was also more frequently detected in carcinoma from proximal rather than distal stomach (P = 0.027). In patients receiving potentially curative resection for advanced cancer, p53 accumulation was an independent parameter and the strongest for poor prognosis (RR = 3.7, P < 0.001). There was complete concordance between immunohistochemical detection of p53 in endoscopic and surgical material.

CONCLUSIONS

A preoperative assessment of p53 expression in gastric carcinoma can be helpful to identify patients at high risk of metastatic spread to regional lymph nodes and independently to identify those with especially poor prognosis. When combined with routine procedures, this simple and inexpensive test might allow appropriate planning of better treatment strategies.

Prognostic significance of TP53 accumulation in human primary breast cancer: comparison between a rapid quantitative immunoassay and SSCP analysis

TP53 accumulation in human primary breast carcinomas was studied by a quantitative luminometric immunoassay (LIA), and TP53 gene alterations, exons 5-8, were examined by single-strand conformation polymorphism (SSCP) analysis. In 48 of 142 breast tumor samples, a TP53 gene alteration was identified. In tumor samples without a TP53 gene alteration, the median cytosolic TP53 protein level, as determined by LIA, was 0.4 ng/mg protein (range 0-70.8 ng/mg protein), whereas the median TP53 protein level for tumor samples with a TP53 gene alteration was 10 times higher, i.e., 4.1 ng/mg protein (range 0.1-176.0 ng/mg protein). Despite a significant correlation between the outcome of LIA and SSCP, a disagreement was found in 22% of cases analyzed. Significant correlations were found between TP53 protein accumulation and low estrogen receptor content, and with a shorter relapse-free as well as overall survival, with a median duration of follow-up of 100 months. Due to its rapid and easy performance on routinely prepared cytosols, the LIA for TP53 protein may be useful in evaluating the prognostic impact of TP53 protein accumulation in human primary breast cancer.

Allosteric regulation of the thermostability and DNA binding activity of human p53 by specific interacting proteins. CRC Cell Transformation Group

Conformational stability is a prerequisite for the physiological activity of the tumor suppressor protein p53. p53 protein can be allosterically activated for DNA binding by phosphorylation or through noncovalent interaction with proteins such as DnaK, the Escherichia coli homologue of the heat shock protein Hsp70. We present in vitro evidence for a rapid temperature-dependent change in the conformation and tetrameric nature of wild-type p53 upon incubation at 37 degrees C, which correlates with a permanent loss in DNA binding activity. We show that p53 is allosterically regulated for stabilization of the wild-type conformation and DNA binding activity at 37 degrees C by binding of two classes of ligands to regulatory sites on the N and C terminus of the molecule through which an intrinsic instability of p53 is neutralized. Deletion of the domain conferring instability at the C terminus is sufficient to confer enhanced stability to the total protein. DnaK binding to the C terminus can profoundly protect p53 at 37 degrees C from a temperature-dependent loss of the DNA binding activity but does not renature or activate denatured p53. In contrast, another activator of the DNA binding activity of latent p53, the monoclonal antibody PAb421, which also interacts with the C terminus of the protein, is not able to protect p53 from thermal denaturation. Two monoclonal antibodies to the N terminus of p53, PAb1801 and DO-1, do not activate the latent DNA binding function of p53 but can protect the p53 wild-type conformation at 37 degrees C. Thus, activation of the DNA binding function of p53 is not synonymous with protection from thermal denaturation, and therefore, both of these pathways may be used in cells to control the physiological activity of p53. The protection of p53 conformation from heat denaturation by interacting proteins suggests a novel mechanism by which p53 function could be regulated in vivo.

The use of antigen retrieval for immunohistochemical detection of p53 over-expression in malignant and benign oral mucosa: a cautionary note

The tumour suppressor gene p53 is frequently mutated in neoplasia. Since mutant p53 protein is often over-expressed, mutation can be indirectly detected by immunocytochemical techniques. As microwave antigen retrieval is becoming a widespread method for increasing the antigenicity of paraffin sections, we investigated the application of this technique to p53 immunohistochemical staining of oral mucosa specimens. Paraffin sections of 22 squamous cell carcinomas (SCC) and 36 benign lesions were immunohistochemically stained with and without antigen retrieval. Without antigen retrieval p53 over-expression was observed in 6/22 SCC and 1/36 benign lesions. Following antigen retrieval positive staining was observed in 15/22 SCC and 35/36 benign lesions. Staining in benign lesions was confined to basal and parabasal cells and could reflect normal functioning of wild-type p53. We conclude that antigen retrieval increases the sensitivity of p53 immunoreactivity, but such staining is not specific for malignancy and should be interpreted with caution.

Aberrant p53 expression does not correlate with the prognosis in anaplastic astrocytoma

Mutations of the p53 tumor-suppressor gene, as determined by the immunohistochemistry of archival formalin-fixed specimens, have been correlated with the prognosis for patients with many different types of malignancy. Similar correlations have been shown in series including patients with all grades of astrocytoma. We hypothesized that this might be a clinically useful prognostic indicator for patients with a defined grade of astrocytoma, anaplastic astrocytoma. This series comprised 54 consecutive patients with biopsy-proven anaplastic astrocytoma treated at one institution. When the CM-1 antiserum was used for testing, 33 (61%) of the 54 biopsies exhibited positive nuclear staining for p53, indicating an abnormal accumulation of the protein. This staining was graded according to the number of positive cells per high-power field. Positive immunohistochemical staining for p53 in the tumor cell nuclei did not correlate with the patient's outcome. Significant correlates of improved patient survival were the presentation with epilepsy in the absence of a neurological deficit (P = 0.005) and the surgeon's performance of a macroscopically complete surgical resection of the tumor (P = 0.01).

Immunohistochemical and molecular analysis of p53, MDM2, proliferating cell nuclear antigen and Ki67 in benign and malignant peripheral nerve sheath tumours

A series of 26 malignant peripheral nerve sheath tumours (MPNST) and 24 benign peripheral nerve sheath tumours (BPNST) were analysed immunocytochemically for p53 expression and the cell proliferation markers proliferating cell nuclear antigen (PCNA) and Ki67 (with MIB1). In 23/26 MPNST, 5%-65% of the tumour cell nuclei were immunoreactive for Ki67 with MIB1 while none of the 24 BPNST had nuclear staining exceeding 5%. Greater than 50% nuclear PCNA staining was detected in 25/26 MPNST compared with 8/24 BPNST; 17/26 MPNST showed 5-100% nuclear staining for p53 (13/26 > 20%), whereas none of the BPNST had nuclear staining exceeding 1%. The Ki67, PCNA and p53 immunostaining results correlated significantly with benign versus malignant (P < 0.001, P < 0.001 and P < 0.005, respectively) as well as mitotic rate (P < 0.001, P < 0.05 and P < 0.05). Ki67 immunostaining results correlated significantly with PCNA and p53, as did p53 and Ki67 and PCNA (P < 0.001 in both). Stepwise (logistic regression forward) multivariate analysis of the variable, benign versus malignant, revealed the strongest correlations with PCNA (P = 0.007) and Ki67 (P = 0.021). Direct confirmation of the presence of p53 protein was obtained by western blot analysis of 3 MPNST and 5 BPNST. Two MPNST, showing 90% and 30% immunoreactivity, were positive for p53, while one MPNST with 5% immunoreactivity and all 5 BPNST were negative. Southern blot analysis performed on the two MPNST with high p53 protein levels revealed no amplification of the MDM2 gene, suggesting that high p53 levels in MPNST are likely to be due to mutation. The results also indicate that PCNA and Ki67 are potentially useful in distinguishing BPNST from MPNST, particularly in problematic cases of cellular schwannoma versus MPNST. The detection of p53 in a large percentage of cells of a plexiform neurofibroma giving rise to MPNST and Ki67 in 5% and 25% of cells of two similar cases suggests that malignant transformation may be detected in some cases by p53 and proliferation markers prior to overt histological evidence of malignancy.

Sequential p53 mutation analysis of pre-invasive and invasive head and neck squamous carcinoma

Single-stranded conformational polymorphism (SSCP) and direct sequencing were performed on uninvolved mucosa, severe dysplasia and invasive carcinoma samples from 20 patients with head and neck squamous carcinoma. Seven (35%) of the non-invasive lesions and 15 (75%) of the invasive carcinomas manifested p53 mutations. Although the majority of mutations were mis-sense, resulting in single amino acid substitution, a silent mutation encoding for the same amino acid and 2 non-sense mutations encoding a stop codon were also observed. Mutations in invasive carcinoma were mostly in exon 8 and involved codons 296, 288 and 298; non-invasive lesions showed more mutations at exons 5 to 7. Five lesions showed simultaneous mutations in 2 different exons; in 3 both non-invasive and invasive carcinomas showed primary mutation at exons 5 to 7, and invasive carcinoma showed a secondary mutation at exon 8. Different codon mutations in the same exon between dysplastic and the corresponding carcinoma samples were found in 2 cases. p53 alterations were not observed in any of the normal mucosa samples. No apparent association between p53 mutations and conventional clinicopathologic parameters, including DNA content, was found in this cohort. Our study indicates that (i) p53 alteration is an early event in the genesis of a subset of head and neck squamous carcinomas, (ii) normal mucosa within the resected specimens lacked p53 mutation, (iii) sequential mutations of different exons of the p53 gene suggests accumulation of genetic alterations during the neoplastic transformation of these lesions and (iv) the difference in codon mutation of the same exon between dysplastic and corresponding carcinoma suggests an independent clonal development.

A simple p53 functional assay for screening cell lines, blood, and tumors

Mutations in the p53 gene are implicated in the pathogenesis of half of all human tumors. We have developed a simple functional assay for p53 mutation in which human p53 expressed in Saccharomyces cerevisiae activates transcription of the ADE2 gene. Consequently, yeast colonies containing wild-type p53 are white and colonies containing mutant p53 are red. Since this assay tests the critical biological function of p53, it can distinguish inactivating mutations from functionally silent mutations. By combining this approach with gap repair techniques in which unpurified p53 reverse transcription-PCR products are cloned by homologous recombination in vivo it is possible to screen large numbers of samples and multiple clones per sample for biologically important mutations. This means that mutations can be detected in tumor specimens contaminated with large amounts of normal tissue. In addition, the assay detects temperature-sensitive mutants, which give pink colonies. We show here that this form of p53 functional assay can be used rapidly to detect germline mutations in blood samples, somatic mutations in tumors, and mutations in cell lines.