Adenocarcinoma arising in Barrett's oesophagus: evidence for the participation of p53 dysfunction in the dysplasia/carcinoma sequence

Adenocarcinoma arising in Barrett's oesophagus is often preceded by mucosal dysplasia, but little is currently known about the aetiology or natural history of this dysplasia/carcinoma sequence. To investigate the participation of the tumour suppressor gene p53 in this sequence, an immunohistochemical analysis of p53 protein overexpression, which is known to closely correlate with point mutation of the p53 gene, was conducted in 30 patients with Barrett's adenocarcinoma. Adjacent Barrett's mucosa was dysplastic in 21 (70%) patients. Sixteen (53%) tumours overexpressed p53, 10 of which had adjacent dysplastic Barrett's mucosa. In all 10 patients, this dysplastic mucosa also overexpressed p53, predominantly in areas of high grade compared with low grade dysplasia. In contrast, none of the dysplastic mucosa adjacent to 11 tumours lacking p53 overexpression showed detectable values of p53. These results suggest that p53 dysfunction may participate in the progression from dysplasia to carcinoma in some patients with Barrett's oesophagus.     

High-grade dysplasia in Barrett's oesophagus

BACKGROUND: The management of high-grade dysplasia (HGD) in Barrett's oesophagus is a controversial and challenging problem. METHODS: An up-to-date review of the literature has been made using Index Medicus, the Medline database, and cross-referencing of major articles on this subject. RESULTS: Diagnosis should be confirmed by a second expert pathologist. Repeat multiple jumbo biopsies and brushings need to be taken to reduce sample error and exclude associated invasive cancer. In young fit patients the advantages of surgery outweight the disadvantage of missing an early adenocarcinoma. Continued endoscopic surveillance may be more appropriate in elderly patients. New technology has increased the number of options. Early results of laser and multipolar electrocoagulation ablation of Barrett's epithelium are encouraging. Photodynamic therapy appears to be ideally suited to HGD and early cancers. CONCLUSION: A selective approach to the management of HGD on an individual patient basis should be adopted.     

Review: Barrett's oesophagus in Taiwan

Barrett's oesophagus is the eponym applied to the columnar epithelium-lined lower oesophagus which is acquired as a complication of chronic gastro-oesophageal reflux (GER). Various complications seen in the Barrett's oesophagus, such as peptic ulcer, stricture, adenocarcinoma are named as Barrett's ulcer, Barrett's stricture-and Barrett's carcinoma, respectively. It is now generally accepted that Barrett's oesophagus is an acquired condition resulting from chronic repetitive GER. The frequency of Barrett's oesophagus seems to be higher in Caucasian than in Oriental or Negro populations. There is a tendency towards increasing prevalence rates all over the world, including Taiwan, due to the Westernization of diet, rapid growth in the elderly population, obesity etc. Almost 6% of the patients who manifest heartburn in GI clinics in Taiwan now suffer from GER, which is almost similar to the 7% reported by Nabel, (USA) in 1976. During the last 30 years, the incidence of esophageal adenocarcinoma has increased rapidly. Patients with Barrett's oesophagus have an increased risk of developing oesophageal adenocarcinoma and should be kept under surveillance. Regular follow-up, at least twice a year or preferably, every 2-3 months, for those patients with SCE using endoscopic surveillance and biopsy for those with severe dysphasia (oesophageal columnar intraepithelial neoplasia) in the surrounding area to detect Barrett's oesophagus cancer, is very important.     

Potential application of p53 as an intermediate biomarker in Barrett's esophagus

Diagnosis of the neoplastic progression in Barrett's esophagus using the histologic classification of dysplasia is frequently difficult. The tumor suppressor protein p53, when mutated, confers a promoter effect on cell growth. The purpose of this study was to evaluate the applicability of p53 as an intermediate biomarker of malignancy in Barrett's esophagus. Archival analysis of 100 biopsy specimens of Barrett's esophagus and 10 esophageal adenocarcinomas were compared with 35 chronic esophagitis biopsy specimens. Immunocytochemistry using an anti-p53 monoclonal antibody was performed and elevated immunoreactivity quantitated microscopically. Data were analyzed using a logistic regression model. Significant p53 immunoreactivity occurred as follows: chronic esophagitis (0%), Barrett's esophagus without dysplasia (10%), with low-grade dysplasia (60%), with high-grade dysplasia (100%), and adenocarcinoma (70%). All cases of Barrett's esophagus were significantly immunoreactive when compared with the chronic esophagitis cases (p = 0.001). There was an increase in p53 immunoreactivity as the histologic classification progressed toward adenocarcinoma (p = 0.001). Progression to high-grade dysplasia may be predicted based on p53 immunoreactivity. These findings suggest a role for p53 as an intermediate biomarker in Barrett's esophagus.     

bcl-2, p53 immunophenotypes and apoptosis in squamous cell carcinoma of the oesophagus

To establish baseline information on neopterin concentrations in livestock, companion and laboratory animals and identify the factors that may influence these concentrations, blood samples were taken from normal dairy cattle, horses, llamas, dogs, cats and rats of varying ages and sexes. In addition, neopterin concentrations in normal, adult equines were compared with those found in racing Thoroughbreds. There were no differences due to sex, sexual maturity, pregnancy, castration, or age. For all ages and sexes combined, mean neopterin concentrations were significantly lower in llamas (2.27+/-0.33 nmol litre(-1)) and rats (2.13+/-0.21 nmol litre(-1)) when compared with the other species tested. Racing Thoroughbreds demonstrated higher neopterin values than adult equines not in training (3.54+/-0.64 vs 3.13+/-1.02 nmol litre(-1)).     

Baculovirus p33 binds human p53 and enhances p53-mediated apoptosis

In vertebrates, p53 participates in numerous biological processes including cell cycle regulation, apoptosis, differentiation, and oncogenic transformation. When insect SF-21 cells were infected with a recombinant of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) overexpressing human p53, p53 formed a stable complex with the product of the AcMNPV orf92, a novel protein p33. The interaction between p53 and p33 was further confirmed by immunoprecipitation studies. When individually expressed in SF-21 cells, human p53 localized mainly in the nucleus whereas baculovirus p33 displayed diffuse cytoplasmic staining and punctuate nuclear staining. However, coexpression of p33 with p53 resulted in exclusive nuclear localization of p33. In both SF-21 and TN-368 cells, p53 expression induced typical features of apoptosis including nuclear condensation and fragmentation, oligonucleosomal ladder formation, cell surface blebbing, and apoptotic body formation. Coexpression of p53 with a baculovirus inhibitor of apoptosis, p35, OpIAP, or CpIAP, blocked apoptosis, whereas coexpression with p33 enhanced p53-mediated apoptosis approximately twofold. Expression of p53 in SF-21 cells stably expressing OpIAP inhibited cell growth in the presence or absence of p33. Thus, human p53 can influence both insect cell growth and death and baculovirus p33 can modulate the death-inducing effects of p53.     

K-ras point mutations are rare events in premalignant forms of Barrett's oesophagus

OBJECTIVE: In Barrett's adenocarcinomas, in contrast to squamous oesophageal carcinomas, K-ras point mutations are thought to be a frequent event. The frequency of K-ras point mutations in premalignant forms of Barrett's oesophagus (metaplasia, dysplasia) leading to adenocarcinoma with increased risk is currently not known. To establish the frequency of K-ras mutations in premalignant forms of Barrett's oesophagus, we investigated oesophageal biopsy specimens with Barrett's metaplastic and dysplastic epithelium for point mutations in the K-ras gene/codons 12, 13. DESIGN: A total of 412 biopsies from patients with Barrett's oesophagus were histologically classified into biopsies with metaplasia (n = 252), dysplasia (n = 105) and adenocarcinoma (n = 11), as well as biopsies distant from disease (normal, n = 37 and hyperplastic squamous epithelium, n = 7). METHODS: DNA from biopsy specimens was amplified by polymerase chain reaction (PCR) with a modified primer for generating a restriction site in the case of wild type in codon 12. Wild-type or point mutations in the K-ras gene/codons 12, 13 were detected by restriction fragment length analysis of the PCR products. RESULTS: Point mutations in K-ras/codon 12 were found in 9 biopsies (n = 1 in metaplasia, n = 4 in dysplasias, n = 4 in adenocarcinomas). All the other biopsies showed the wild type of K-ras/codon 12. No K-ras/codon 13 mutation (GGCgly-->GACasp) was observed. CONCLUSION: Mutations in K-ras/codon 12 were rarely found in premalignant forms of Barrett's oesophagus. Whereas the screening for K-ras point mutations in metaplastic sites of Barrett's epithelium seems not to be of practical value, the screening for mutations in dysplastic lesions might be helpful to estimate the individual risk for progression of Barrett's epithelium to adenocarcinoma. A further evaluation in larger numbers of patients is needed.     

p53 and apoptosis

Loss of function of the p53 tumour suppressor gene is a frequent and important event in the genesis or progression of many human malignancies. Loss of p53 dependent apoptosis is believed to be critical to carcinogenesis in many of these cases, suggesting the possibility to therapeutically restore this pathway and directly eliminate malignant cells or increase or restore their sensitivity to chemotherapeutic agents. The regulation of p53-dependent responses is complex and variable between cell types, and whether a cell undergoes apoptosis after activation of p53 is highly sensitive to signal context, including environmental and cell intrinsic influences. This article focuses upon p53-dependent apoptosis, considering current understanding of the biochemical steps involved, the factors determining selection of apoptosis over other p53-dependent responses, the significance of p53-dependent apoptosis for the genesis, progression and drug resistance of human cancers, and finally the prospects for clinical manipulation of this pathway in cancer therapy.     

p53 and colorectal cancer

Mutations of the p53 gene have been found in 380 of the 768 tumors (49.5%) included in the eight largest published series of colorectal cancer. Most point mutations of p53 change the conformation of the gene, and by stabilizing it make it detectable by immunohistochemistry. However, studies using both tests for p53 mutations and immunohistochemical methods found that the results of these two approaches were concordant in only 68% of cases. Conflicting data have been reported regarding the prognostic significance of positive p53 staining. Presence of a mutation is generally believed to indicate a poor prognosis.     

Cancer progression and p53

In a complex organism, somatic cells are under intermittent selection pressure for the emergence of mutants that can survive environmental insults and that can grow autonomously despite adverse conditions. Repeated rounds of mutation, selection, and proliferation may lead to cancer. The organism prevents malignant transformation by assuring accurate DNA repair before cell division, by forcing the death of cells with excessive DNA damage, and by placing limits on the replicative lifespans of most somatic cells. The p53 gene is a "guardian of the genome"--it regulates multiple components of the DNA damage control response and promotes cellular senescence. Disabling mutations and deletions of p53 occur in 50% of human tumours. p53-deficient cancers are often unstable, aggressive, and resistant to therapy.     

Flow cytometric DNA analysis and p53 protein expression show a good correlation with histologic findings in patients with Barrett's esophagus

BACKGROUND: There is a considerable degree of subjectivity and, therefore, substantial interobserver and intraobserver disagreement in the diagnosis and grading of dysplastic lesions in Barrett's esophagus (BE). The aim of this study was to evaluate the usefulness of DNA flow cytometry and immunohistochemical staining for p53 protein as objective methods to complement the conventional histologic diagnosis of dysplasia in patients with this disease. The most common problems and the possible advantages of using these procedures are analyzed briefly in this article. METHODS: Formalin fixed, paraffin embedded tissue from 55 patients diagnosed with BE were processed for flow cytometric measurements (ploidy and proliferation index) and p53 immunostaining. RESULTS: Both the cytometric data and the positivity of staining for p53 revealed a statistically significant increase throughout the following sequence: no dysplasia --> indefinite for dysplasia --> low grade dysplasia --> high grade dysplasia --> adenocarcinoma. There was also a highly significant correlation between the results of the cytometric study and the positivity of staining for p53. CONCLUSIONS: In the future, the use of this procedure could play an important role in the evaluation of patients with BE. Considering that staining for p53 is technically simple, economical, and quick, and the materials required are available to most pathology laboratories, this method appears to be a firm candidate for application as a biomarker in BE. The authors have shown that it is possible to obtain adequate results for cytometric analysis with small formalin fixed, paraffin embedded biopsies if a strict protocol for the acceptance of tissue samples and/or histograms is observed.