Comparison of p53 and DNA content abnormalities in adenocarcinoma of the oesophagus and gastric cardia

Pathologic Features of Esophageal and Gastric Malignancies

Esophageal cancer is the eighth most common cancer globally, affecting approximately 570,000 people worldwide and currently ranking sixth among cancer-related mortality (Uhlenhopp et al. in, Clin J Gastroenterol 13:1010-1021, 2020). The prognosis is poor as many patients present with locally incurable or metastatic disease. In spite of advancements in treatment, the overall 5-year survival rates are in the realm of 10% whereas the 5-year post-esophagectomy survival rates are in the realm of 15-40% [2]. The incidence rates vary dramatically worldwide, which can be attributed to demographic and socioeconomic factors. Although the vast majority of esophageal neoplasms arise from the epithelial layer and include squamous cell carcinoma (SCC) and adenocarcinoma (AC), a subset of neuroendocrine and soft tissue tumors can also occur in the esophagus. Several tasks are presented to the surgical pathologist when dealing with esophageal carcinoma that include rendering a diagnosis, classifying the histological type, and assessing prognostic factors. This narrative review aims to evaluate current literature on various esophageal neoplasms and highlight pathological factors that impact clinical decision making and prognosis.

Status of CHEK2 and p53 in patients with early-onset and conventional gastric cancer

Gastric cancer (GC) is the fourth most common cause of cancer-associated death. Based on the age at diagnosis, GC is divided into early-onset GC (EOGC; ≤45 years) and conventional GC (CGC; >45 years). Mutations in the cell cycle checkpoint kinase 2 (CHEK2) and TP53 genes are associated with several types of cancer; however, their genetic defects in GC remain poorly understood. The aim of the present study was to determine the subcellular distribution of the CHEK2 protein and its redistribution following DNA damage, to improve the understanding of the DNA damage response. Genetic alterations and patterns of expression of CHEK2 and p53 proteins were investigated to identify potential biological markers and indicators of GC development. Additionally, the affected signaling pathways and their clinical importance in GC development and associated syndromes were investigated. A total of 196 GC samples (89 CGC and 107 EOGC samples) were used in the present study. DNA from 53 samples (18 CGC and 35 EOGC samples) was sequenced using targeted next-generation sequencing technology to identify and compare common and rare mutations associated with GC. Subsequently, the cytoplasmic and nuclear expression levels of CHEK2, phosphorylated (p)-CHEK2 at threonine 68 and p53 in GC tissues were determined via immunohistochemistry. Sequencing resulted in the identification of 63 single nucleotide polymorphisms (SNPs) in the CHEK2 gene amongst 5 different variants, and the intron variant c.319+379A>G was the most common SNP. In the TP53 gene, 57 different alterations were detected amongst 9 variant types, and the missense variant c.215C>G was the most common. Nuclear CHEK2 expression was high in both the EOGC and CGC subtypes. However, the prevalence of cytoplasmic CHEK2 expression (P<0.001) and nuclear p-CHEK2 expression (P=0.011) was significantly higher in CGC compared with in EOGC tissues. There was a statistically significant difference between high and low cytoplasmic CHEK2 expression in patients with p53-positive EOGC compared with in patients with p53-positive CGC (P=0.002). The present study was designed to determine the association between CHEK2 and p53 expression patterns in patients with EOGC and CGC, as well as genetic alterations in the CHEK2 and TP53 genes.

Econazole Induces p53-Dependent Apoptosis and Decreases Metastasis Ability in Gastric Cancer Cells

Econazole, a potent broad-spectrum antifungal agent and a Ca²⁺ channel antagonist, induces cytotoxicity in leukemia cells and is used for the treatment of skin infections. However, little is known about its cytotoxic effects on solid tumor cells. Here, we investigated the molecular mechanism underlying econazole-induced toxicity in vitro and evaluated its regulatory effect on the metastasis of gastric cancer cells. Using the gastric cancer cell lines AGS and SNU1 expressing wild-type p53 we demonstrated that econazole could significantly reduce cell viability and colony-forming (tumorigenesis) ability. Econazole induced G0/G1 phase arrest, promoted apoptosis, and effectively blocked proliferation- and survival-related signal transduction pathways in gastric cancer cells. In addition, econazole inhibited the secretion of matrix metalloproteinase- 2 (MMP-2) and MMP-9, which degrade the extracellular matrix and basement membrane. Econazole also effectively inhibited the metastasis of gastric cancer cells, as confirmed from cell invasion and wound healing assays. The protein level of p53 was significantly elevated after econazole treatment of AGS and SNU1 cells. However, apoptosis was blocked in econazole-treated cells exposed to a p53-specific small-interfering RNA to eliminate p53 expression. These results provide evidence that econazole could be repurposed to induce gastric cancer cell death and inhibit cancer invasion.

Lifestyle chemical carcinogens associated with mutations in cell cycle regulatory genes increases the susceptibility to gastric cancer risk

In the present study, we correlated the various lifestyle habits and their associated mutations in cell cycle (P21 and MDM2) and DNA damage repair (MLH1) genes to investigate their role in gastric cancer (GC). Multifactor dimensionality reduction (MDR) analysis revealed the two-factor model of oral snuff and smoked meat as the significant model for GC risk. The interaction analysis between identified mutations and the significant demographic factors predicted that oral snuff is significantly associated with P21 3'UTR mutations. A total of five mutations in P21 gene, including three novel mutations in intron 2 (36651738G > A, 36651804A > T, 36651825G > T), were identified. In MLH1 gene, two variants were identified viz. one in exon 8 (37053568A > G; 219I > V) and a novel 37088831C > G in intron 16. Flow cytometric analysis predicted DNA aneuploidy in 07 (17.5%) and diploidy in 33 (82.5%) tumor samples. The G2/M phase was significantly arrested in aneuploid gastric tumor samples whereas high S-phase fraction was observed in all the gastric tumor samples. This study demonstrated that environmental chemical carcinogens along with alteration in cell cycle regulatory (P21) and mismatch repair (MLH1) genes may be stimulating the susceptibility of GC by altering the DNA content level abnormally in tumors in the Mizo ethic population.

Centrosome amplification arises before neoplasia and increases upon p53 loss in tumorigenesis

Centrosome abnormalities are a typical hallmark of human cancers. However, the origin and dynamics of such abnormalities in human cancer are not known. In this study, we examined centrosomes in Barrett's esophagus tumorigenesis, a well-characterized multistep pathway of progression, from the premalignant condition to the metastatic disease. This human cancer model allows the study of sequential steps of progression within the same patient and has representative cell lines from all stages of disease. Remarkably, centrosome amplification was detected as early as the premalignant condition and was significantly expanded in dysplasia. It was then present throughout malignant transformation both in adenocarcinoma and metastasis. The early expansion of centrosome amplification correlated with and was dependent on loss of function of the tumor suppressor p53 both through loss of wild-type expression and hotspot mutations. Our work shows that centrosome amplification in human tumorigenesis can occur before transformation, being repressed by p53. These findings suggest centrosome amplification in humans can contribute to tumor initiation and progression.

Microsatellite instability in metaplasia-dysplasia-adenocarcinoma sequence of Barrett esophagus: a retrospective study

Aim

To analyze the loss of mismatch repair (MMR) system protein expression in metaplasia-dysplasia-adenocarcinoma sequence of Barrett esophagus (BE).

Methods

This study retrospectively analyzed the data from 70 patients with pathohistological diagnosis of BE or esophageal adenocarcinoma (EAC) treated at the Clinical Department of Pathology and Cytology, University Hospital Center Zagreb, from January 2009 to January 2011. Patients were divided into three groups: BE without dysplasia (22 patients), BE with dysplasia (37 patients), and EAC (11 patients). Immunohistochemical expression of MutL homologue 1 (MLH1), MutS homologue 2 (MSH2), postmeiotic segregation increased 2 (PMS2), and MutS homologue 6 (MSH6) of DNA MMR system was measured and compared with tumor protein p53 expression.

Results

A total of 81.8% and 81.8% patients with EAC, 32.4% and 35.1% patients with dysplasia, and 50% and 54.5% patients without dysplasia had loss of MLH1 and PMS2 expression, respectively. Patients with EAC and patients with dysplasia did not have loss of MSH2 and MSH6 expression, and 18.2% patients without dysplasia had loss of MSH2 and MSH6 expression. There was a strong positive correlation between MLH1 and PMS2 expression (Spearman ρ 0.97; P < 0.001) and between MSH2 and MSH6 expression (Spearman ρ 0.90, P < 0.001) in the entire sample and in all BE groups. No significant correlations of MLH1 and PMS2 with p53 expression were found, except in dysplasia group (φ 0.402, P = 0.030 for MSH1; φ 0.371, P = 0.042 for PMS2).

Conclusion

Although we demonstrated considerable loss of MLH1 and PMS2 expression in BE-associated carcinoma sequence, due to the retrospective study design and low number of patients we cannot conclude that MLH1 and PMS2 can be used as biomarkers for patient surveillance and therapy-making decisions.

Oxford Centre for Evidence-based Medicine level of evidence: 3

Comparative analysis of gene expression profiles of gastric cardia adenocarcinoma and gastric non-cardia adenocarcinoma

In the present study, gene expression profiles were analyzed to identify the molecular mechanisms underlying gastric cardia adenocarcinoma (GCA) and gastric non-cardia adenocarcinoma (GNCA). A gene expression dataset (accession number GSE29272) was downloaded from Gene Expression Omnibus, and consisted of 62 GCA samples and 62 normal controls, as well as 72 GNCA samples and 72 normal controls. The two groups of differentially-expressed genes (DEGs) were compared to obtain common and unique DEGs. A differential analysis was performed using the Linear Models for Microarray Data package in R. Functional enrichment analysis was conducted for the DEGs using the Database for Annotation, Visualization and Integrated Discovery. Protein-protein interaction (PPI) networks were constructed for the DEGs with information from the Search Tool for the Retrieval of Interacting Genes. Subnetworks were extracted from the whole network with Cytoscape. Compared with the control, 284 and 268 genes were differentially-expressed in GCA and GNCA, respectively, of which 194 DEGs were common between GCA and GNCA. Common DEGs [e.g., claudin (CLDN)7, CLDN4 and CLDN3] were associated with cell adhesion and digestion. GCA-unique DEGs [e.g., MAD1 mitotic arrest deficient like 1, cyclin (CCN)B1, CCNB2 and CCNE1] were associated with the cell cycle and the regulation of cell proliferation, while GNCA-unique DEGs (e.g., GATA binding protein 6 and hyaluronoglucosaminidase 1) were implicated in cell death. A PPI network with 141 nodes and 446 edges were obtained, from which two subnetworks were extracted. Genes [e.g., fibronectin 1, collagen type I α2 chain (COL1A2) and COL1A1] from the two subnetworks were implicated in extracellular matrix organization. These common DEGs could advance our understanding of the etiology of gastric cancer, while the unique DEGs in GCA and GNCA could better define the properties of specific cancers and provide potential biomarkers for diagnosis, prognosis or therapy.

Overview of major molecular alterations during progression from Barrett's esophagus to esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) develops in the sequential transformation of normal epithelium into metaplastic epithelium, called Barrett's esophagus (BE), then to dysplasia, and finally cancer. BE is a common condition in which normal stratified squamous epithelium of the esophagus is replaced with an intestine-like columnar epithelium, and it is the most prominent risk factor for EAC. This review aims to impartially systemize the knowledge from a large number of publications that describe the molecular and biochemical alterations occurring over this progression sequence. In order to provide an unbiased extraction of the knowledge from the literature, a text-mining methodology was used to select genes that are involved in the BE progression, with the top candidate genes found to be TP53, CDKN2A, CTNNB1, CDH1, GPX3, and NOX5. In addition, sample frequencies across analyzed patient cohorts at each stage of disease progression are summarized. All six genes are altered in the majority of EAC patients, and accumulation of alterations correlates well with the sequential progression of BE to cancer, indicating that the text-mining method is a valid approach for gene prioritization. This review discusses how, besides being cancer drivers, these genes are functionally interconnected and might collectively be considered a central hub of BE progression.

Role of p53 in the progression of gastric cancer

Intestinal metaplasia (IM) is a premalignant lesion associated with gastric cancer (GC) but is poorly described in terms of molecular changes. Here, we explored the role of TP53, a commonly mutated gene in GC, to determine if p53 protein expression and/or the presence of somatic mutations in TP53 can be used as a predictive marker for patients at risk of progressing to GC from IM. Immunohistochemistry and high resolution melting were used to determine p53 protein expression and TP53 mutation status respectively in normal gastric mucosa, IM without concurrent GC (IM-GC), IM with concurrent GC (IM+GC) and GC. This comparative study revealed an incremental increase in p53 expression levels with progression of disease from normal mucosa, via an IM intermediate to GC. TP53 mutations however, were not detected in IM but occurred frequently in GC. Further, we identified increased protein expression of Mdm2/x, both powerful regulators of p53, in 100% of the IM+GC cohort with these samples also exhibiting high levels of wild-type p53 protein. Our data suggests that TP53 mutations occur late in gastric carcinogenesis contributing to the final transition to cancer. We also demonstrated involvement of Mdmx in GC.

Comparison of global gene expression of gastric cardia and noncardia cancers from a high-risk population in china

Objective

To profile RNA expression in gastric cancer by anatomic subsites as an initial step in identifying molecular subtypes and providing targets for early detection and therapy.

Methods

We performed transcriptome analysis using the Affymetrix GeneChip U133A in gastric cardia adenocarcinomas (n = 62) and gastric noncardia adenocarcinomas (n = 72) and their matched normal tissues from patients in Shanxi Province, and validated selected dysregulated genes with additional RNA studies. Expression of dysregulated genes was also related to survival of cases.

Results

Principal Component Analysis showed that samples clustered by tumor vs. normal, anatomic location, and histopathologic features. Paired t-tests of tumor/normal tissues identified 511 genes whose expression was dysregulated (P<4.7E-07 and at least two-fold difference in magnitude) in cardia or noncardia gastric cancers, including nearly one-half (n = 239, 47%) dysregulated in both cardia and noncardia, one-fourth dysregulated in cardia only (n = 128, 25%), and about one-fourth in noncardia only (n = 144, 28%). Additional RNA studies confirmed profiling results. Expression was associated with case survival for 20 genes in cardia and 36 genes in noncardia gastric cancers.

Conclusions

The dysregulated genes identified here represent a comprehensive starting point for future efforts to understand etiologic heterogeneity, develop diagnostic biomarkers for early detection, and test molecularly-targeted therapies for gastric cancer.

Gastric cardia adenocarcinoma pathway analysis

Gastric cardia adenocarcinoma (GCA)is one of the few malignancies with unexplained reasons that have increased sharply in developed countries. The purpose of this review was to determine the pathways in GCA to identify new biomarker. So by comparing gene expression in GCA group with normal control identified important pathways. Gene expression data were extracted from the beforehand investigations then differentially expressed genes utilized in DAVID program to explorer and find related pathways. Our findings contain 367 gene names. Out of these 367 proteins, 199 were found to be exclusively expressed in GCA; whereas 168 proteins were detected down-regulated or silenced. The GCA associated diseases based on the differently expressed genes made up of diseases pathway related colorectal cancer, small cell lung cancer, breast cancer and H. pylori infection stomach cancer. KEGG pathways related to GCA contained cell cycle, p53 signaling pathway, DNA replication, toll-like receptor signaling pathway and some other diseases. The GO-discovered categories also demonstrated most biological process and molecular function related to cancer. Up until now, there is no report to introduce influential biomarkers in GCA so, the deregulated genes identified in GCA patterns might be helpful for diagnosis, prognosis and therapies for gastric cancer but validation of these biomarkers is necessary.

Alterations of the TP53 gene in gastric and esophageal carcinogenesis

TP53 genes is one of more important tumor suppressor gene, which acts as a potent transcription factor with fundamental role in the maintenance of genetic stability. The development of esophageal and gastric cancers is a multistep process resulting in successive accumulation of genetic alterations that culminates in the malignant transformation. Thus, this study highlights the participation of the main genetic alterations of the TP53 gene in esophageal and gastric carcinogenesis. Among these changes, high frequency of TP53 mutations, loss of heterozygosity (LOH), overexpression of the p53 protein, and consequently loss of p53 function, which would be early events in esophageal and gastric cancers, as well as an important biomarker of the prognosis and treatment response. Furthermore, Single Nucleotide Polymorphisms (SNPs) of TP53 have been implicated in the development and prognosis of several cancers, mainly TP53 codon 72 polymorphism whose role has been extensively studied in relation to susceptibility for esophageal and gastric cancer development.

Clinicopathological features and prognostic factors of proximal gastric carcinoma in a population with high Helicobacter pylori prevalence: a single-center, large-volume study in Korea

BACKGROUND

The incidence of gastric cancers has fallen in recent decades. However, a substantial reduction in Helicobacter pylori prevalence and a substantial increase in the incidence of proximal gastric cancer (PGC) have been observed in the West and Japan, but not in other East Asian countries. The purpose of this large-volume study was to analyze prevalence, clinicopathological features, and prognosis of PGC compared with other types of gastric cancer in Korea, where there is high incidence of H. pylori infection.

METHODS

Between 2000 and 2005, a total of 3,193 patients were enrolled. We analyzed clinicopathological features and survival outcomes.

RESULTS

Chronological analysis showed increasing incidence of PGC over the study period. PGC patients were younger and had higher incidence of Bormann types III and IV than did distal gastric cancer (DGC) patients. Also, PGC was associated with a significantly higher proportion of poorly differentiated type, T3 and T4 stage, and positive lymph nodes compared with DGC. Peritoneal and other distant metastases were more common in PGC group than in DGC group. The 5-year survival rate was significantly lower in PGC than in DGC group, regardless of curative resection. Also, the N0 and N1 category significantly influenced the 5-year survival rate. Tumor-node-metastasis (TNM) stage, hepatic metastasis, and curative resection were significant prognostic factors in PGC patients.

CONCLUSIONS

PGC has increased in incidence with the respective decline in H. pylori prevalence in Korea. Survival was worse for patients with PGC than for those with DGC, regardless of curative respectability. PGC is often diagnosed at more advanced stage than other gastric cancers, and therefore early detection is critical for successful treatment.

Cigarette smoking, body mass index, gastro-esophageal reflux disease, and non-steroidal anti-inflammatory drug use and risk of subtypes of esophageal and gastric cancers by P53 overexpression

A number of risk factors for esophageal and gastric cancers have emerged, yet little is known whether risk factors map to molecular tumor markers such as overexpression of the tumor suppressor TP53. Using a US multicenter, population-based case-control study (170 cases of esophageal adenocarcinomas, 147 gastric cardia adenocarcinomas, 220 non-cardia gastric adenocarcinomas, and 112 esophageal squamous cell carcinomas), we examined whether the risk associated with cigarette smoking, body mass index (BMI), gastroesophageal reflux disease (GERD), and non-steroidal anti-inflammatory drug (NSAID) use varied by P53 overexpression. We defined P53 overexpression through immunohistochemistry of paraffin-embedded tumor tissues, using cutpoints based on percent of cells positive. Polytomous logistic regression was used to assess differences between each case group (defined by tumor subtype and P53 expression) and the control group by risk factors. The proportion of cases overexpressing P53 by tumor subtype was 72% for esophageal adenocarcinoma, 69% for gastric cardia adenocarcinoma, 52% for non-cardia gastric adenocarcinoma, and 67% for esophageal squamous cell carcinoma. For most tumor subtypes, we found little difference in risk factors by tumor P53 overexpression. For non-cardia gastric cancer however, an association with cigarette smoking was suggested for tumors that do not overexpress P53, whereas larger BMI was related to adenocarcinomas that overexpress P53 versus no overexpression. Overall, this study did not find a clear relationship between P53 protein overexpression and the known risk factors for subtypes of esophageal and gastric cancers. Further research on these tumors is needed to identify molecular markers associated with variations in the risk factor profiles.

Human Gastric Adenocarcinoma Allelotype on Chromosomes 17 and 18

Allelic losses of multiple chromosome loci in gastric adenocarcinoma suggest that inactivation of tumour suppressor genes in these regions may be important for tumourigenesis. To define deletion intervals and find candidate tumour suppressor genes involved in gastric adenocarcinoma pathogenesis, a genome-wide search for loss of heterozygosity (LOH) was conducted in 45 patients with primary gastric adenocarcinoma. Investigations using 29 microsatellite markers spanning chromosomes 17 and 18 showed allelic deletion in 29 (64%) specimens at one or more loci. Five LOH overlap regions, three newly identified as deletion regions, were defined: RI, D17S831–D17S921 at 17p12-13.3; RII, D17S1868–D17S787 at 17q21.3-22; RIII, D17S785–D17S928 at 17q25.3; RIV, D18S61–D18S1161 at 18q22; and RV, D18S462–D18S70 at 18q22-q23. Eleven (24%) patients with chromosome 17 allelic loss also showed LOH on 18q, with at least one region of overlapping. LOH mapping showed allelic losses were widespread on both chromosomes and suggests the possibility that multiple tumour suppressor genes, including one or more that are unknown, might be inactivated in the aetiology of gastric adenocarcinoma.

Open questions in oesophageal adenocarcinogenesis

Transition from GORD to Barrett's oesophagus, and possibility of a reversal mechanism

Pathologic Risk Factors of Adenocarcinoma of the Gastric Cardia and Gastroesophageal Junction

Available evidence supports the existence of two major pathways of neoplastic development in the gastroesophageal region: the Barrett pathway, related to gastroesophageal reflux disease, and the gastric pathway, related to Helicobacter pylori infection. The existence of an independent junctional pathway is questionable, and gastroesophageal junction adenocarcinomas share features of esophageal and gastric adenocarcinomas. It has been impossible to accommodate all data that are provided by different levels and tools of observation in tumors that develop in the gastroesophageal region in a single, coherent classification. That is why the stratification of pathologic risk in such tumors, and their respective precursors, incorporates features from topography, histology, immunohistochemistry, and molecular pathology.

TP53 and progression from Barrett's metaplasia to oesophageal adenocarcinoma in a UK population cohort

BACKGROUND AND AIMS

Oesophageal adenocarcinoma frequently develops on a background of metaplastic Barrett's epithelium. The development of malignancy is accompanied by genetic alterations, which may be promising biomarkers of disease progression.

METHODS

A case control study was conducted nested within a large unselected population based cohort of Barrett's patients. Incident oesophageal malignancies and high grade dysplasias were identified. For each case up to five controls were matched on age, sex, and year of diagnosis. Biopsies from the time of diagnosis of Barrett's epithelium were stained immunohistochemically for TP53, cyclin D1, cyclooxygenase 2 (COX-2), and beta-catenin proteins.

RESULTS

Twenty nine incident oesophageal malignancies and six cases of high grade dysplasia were identified. The odds of diffuse or intense TP53 staining were substantially elevated in biopsies from patients who developed oesophageal adenocarcinoma compared with controls (odds ratio (OR) 11.7 (95% confidence interval (CI) 1.93, 71.4)). This difference was also present when all cases were considered (OR 8.42 (95% CI 2.37, 30.0). Despite the association with TP53 staining, only 32.4% of cases had an initial biopsy showing diffuse/intense TP53 staining. There were no significant associations between cyclin D1, COX-2, or beta-catenin staining and case control status. The OR for positive staining for both TP53 and COX-2 was markedly increased in cases compared with controls (OR 27.3 (95% CI 2.89, 257.0)) although only 15% of cases had positive staining for both markers.

CONCLUSIONS

Immunohistochemical detection of TP53 expression is a biomarker of malignant progression in Barrett's oesophagus but sensitivity is too low to act as a criterion to inform endoscopic surveillance strategies. Additional biomarkers are required which when combined with TP53 will identify, with adequate sensitivity and specificity, Barrett's patients who are at risk of developing cancer.

Genetic mechanisms of TP53 loss of heterozygosity in Barrett's esophagus: implications for biomarker validation

BACKGROUND AND AIMS

17p (TP53) loss of heterozygosity (LOH) has been reported to be predictive of progression from Barrett's esophagus to esophageal adenocarcinoma, but the mechanism by which TP53 LOH develops is unknown. It could be (a) DNA deletion, (b) LOH without copy number change, or (c) tetraploidy followed by genetic loss. If an alternative biomarker assay, such as fluorescence in situ hybridization (FISH), provided equivalent results, then translation to the clinic might be accelerated, because LOH genotyping is presently limited to research centers.

METHODS

We evaluated mechanisms of TP53 LOH to determine if FISH and TP53 LOH provided equivalent results on the same flow-sorted samples (n = 43) representing established stages of clonal progression (diploid, diploid with TP53 LOH, aneuploid) in 19 esophagectomy specimens.

RESULTS

LOH developed by all three mechanisms: 32% had DNA deletions, 32% had no copy number change, and 37% had FISH patterns consistent with a tetraploid intermediate followed by genetic loss. Thus, FISH and LOH are not equivalent (P < 0.000001).

CONCLUSIONS

LOH develops by multiple chromosome mechanisms in Barrett's esophagus, all of which can be detected by genotyping. FISH cannot detect LOH without copy number change, and dual-probe FISH is required to detect the complex genetic changes associated with a tetraploid intermediate. Alternative biomarker assay development should be guided by appreciation and evaluation of the biological mechanisms generating the biomarker abnormality to detect potential sources of discordance. FISH will require validation in adequately powered longitudinal studies before implementation as a clinical diagnostic for esophageal adenocarcinoma risk prediction.

Epidemiology and molecular biology of Barrett esophagus

Over the past three decades, there has been a marked change in the epidemiology of esophageal malignancy, with an increasing incidence of esophageal adenocarcinoma. The reasons for this are largely unknown and remain controversial, but several lifestyle risk factors have been proposed, including gastroesophageal reflux disease (GERD). It is hypothesized that chronic GERD results in acute mucosal injury, promotes cellular proliferation, and induces specialized columnar metaplasia (Barrett esophagus). Progression of Barrett esophagus to invasive adenocarcinoma is reflected histologically by the metaplasia-dysplasia-carcinoma sequence. Dysplasia is widely regarded as the precursor of invasive cancer, and high-grade dysplasia in Barrett epithelium is frequently associated with esophageal adenocarcinoma. Although several molecular alterations have been described in Barrett esophagus, it is anticipated that relatively few will prove to be clinically useful. To date, biomarkers which currently appear to predict the progression of Barrett esophagus to invasive malignancy include aneuploidy, loss of heterozygosity of 17p (implicating the p53 tumor suppressor gene), and cyclin D1 protein overexpression, and with further validation, will most likely be incorporated into routine clinical practice. It is anticipated that models incorporating objective scores of sociodemographic and lifestyle risk factors (ie, age, gender, body mass index), severity of reflux symptoms, endoscopic and histologic findings, and an assessment of a panel of biomarkers will be developed to further define subsets of patients with Barrett esophagus at increased risk for malignant progression, thereby permitting the development of more rational endoscopic surveillance and screening programs.

Multistage carcinogenesis in Barrett's esophagus

The multistage carcinogenesis of esophageal adenocarcinoma is a process of clonal evolution within Barrett's esophagus neoplasms. The initiating event for Barrett's esophagus is unknown, but is associated with chronic gastric reflux which probably also promotes progression. Inactivation of both alleles of CDKN2A appear to be early events causing clonal expansion. Clones with TP53 inactivated expand if they have already inactivated CDKN2A. After TP53 has been inactivated, tetraploid and aneuploid clones tend to develop. The final events that lead to invasion and metastasis are unknown. Evolutionary biology provides important tools to understand clonal evolution in progression and cancer prevention.

Identification of a 7.1–mega base pairs minimal deletion at 14q31.1-32.11 in adenocarcinomas of the gastroesophageal junction

In a recent evaluation by comparative genomic hybridization, we demonstrated chromosome 14q31-32.1 to be frequently deleted in adenocarcinomas of the gastroesophageal junction. This suggests the presence of a tumor suppressor gene in the deleted region. In the present study, we have performed a detailed loss of heterozygosity analysis in 34 gastroesophageal junction adenocarcinomas and 1 tumor-corresponding dysplastic Barrett's epithelium sample with 37 polymorphic microsatellite markers. Thirty-five markers are in the 14q24.3-32.33 region with a mean distance of 800 kilo base pairs. Of 34 tumor samples, 14 (41%) showed loss of 14q markers. We identified a minimal region of allelic loss of 7105440 base pairs between markers D14S1000 and D14S256 at cytogenetic location 14q31.1-32.11. Within this region, markers D14S1035, D14S55, D14S1037, D14S1022, D14S1052, D14S974, D14S73, D14S1033, D14S67, D14S68, and D14S1058 showed loss in all informative tumors with 14q loss. The region between markers D14S1000 and D14S256 contains 7 known genes. The identification of this minimal deletion and the data base information on the genes present in this region facilitate the search for the candidate tumor suppressor gene(s).

Lack of prognostic impact of p53 gene mutation and p53 phosphorylation at serine 15 in multimodally treated adenocarcinomas of the gastroesophageal junction

PURPOSE

As inactivation of p53 may be correlated with poor response of tumors to chemo- and/or radiotherapy the presence of p53 mutations in exons 5-8 was determined in adenocarcinomas of the gastroesophageal junction (GEJ). As p53 protein phosphorylation at serine 15 indicates stabilization and protection against mdm-2 the presence of this phosphorylation state was subsequently evaluated.

METHODS

Mutations in exons 5-8 were analyzed by denaturing high pressure liquid chromatography (DHPLC) and subsequent sequence analysis in pretherapeutic biopsies of 38 adenocarcinomas of the GEJ that had undergone multimodal treatment in the course of a prospective multicentric phase III trial. The presence of p53 protein phosphorylation at serine 15 was evaluated by immunohistochemistry.

RESULTS

Mutations in the DNA binding region were found in 23 samples and were only weakly associated with worse 2-year survival (P=0.083). Phosphorylation at serine 15 of p53 was detected in 14 samples, being neither associated with p53 mutation nor with patient's survival.

CONCLUSION

This allows the conclusion that the determination of these two parameters does not help to select patients who do profit from multimodal treatment for adenocarcinomas of the GEJ.

Biomarkers in the molecular pathogenesis of esophageal (Barrett) adenocarcinoma

Since the early 1970s, a dramatic change has occurred in the epidemiology of esophageal malignancy in both North America and Europe: the incidence of adenocarcinomas of the lower esophagus and esophagogastric junction is increasing. Several lifestyle factors are implicated in this change, including gastroesophageal reflux disease (GERD). Primary esophageal adenocarcinomas are thought to arise from Barrett esophagus, an acquired condition in which the normal esophageal squamous epithelium is replaced by a specialized metaplastic columnar-cell-lined epithelium.Today, gerd is recognized as an important risk factor in Barrett esophagus. Progression of Barrett esophagus to invasive adenocarcinoma is reflected histologically by the metaplasia-dysplasia-carcinoma sequence. Although several molecular alterations associated with progression of Barrett esophagus to invasive adenocarcinoma have been identified, relatively few will ultimately have clinical application. Currently, the histologic finding of high-grade dysplasia remains the most reliable predictor of progression to invasive esophageal adenocarcinoma. However other promising molecular biomarkers include aneuploidy; 17p loss of heterozygosity, which implicates the TP53 tumour suppressor gene; cyclin D1 protein overexpression; and p16 alterations. It is anticipated that models incorporating combinations of objective scores of sociodemographic and lifestyle risk factors (that is, age, sex, body mass index), severity of gerd, endoscopic and histologic findings, and a panel of biomarkers will be developed to better identify patients with Barrett esophagus at increased risk for malignant progression, leading to more rational endoscopic surveillance and screening programs.

TP53 gene mutations are rare in nondysplastic Barrett's esophagus

In search of potential prognostic markers, we analyzed a large series of tissues of Barrett's esophagus and samples of adenocarcinomas arising in the terrain of Barrett's esophagus for TP53 gene mutations by direct sequencing of exons 5 to 9 of the TP53 gene. While 9 of 21 adenocarcinomas tested (42.9%) contained a TP53 mutation, none of 24 samples from Barrett's esophagus were mutated. This observation suggests that TP53 gene mutation may be a relatively late event in the progression from nondysplastic Barrett's esophagus to adenocarcinoma of esophagus. Therefore, TP53 gene mutations alone are not likely to represent a widely useful prognostic marker of the risk of progression to malignancy, at least not in Barrett's esophagus without dysplasia.

STRAD in Peutz-Jeghers syndrome and sporadic cancers

BACKGROUND/AIMS

LKB1 is a tumour suppressor gene that is associated with Peutz-Jeghers syndrome (PJS), a rare autosomal dominant cancer predisposition syndrome. However, germline mutations in the LKB1 gene are found in only about 60% of patients with PJS, suggesting the existence of a second PJS gene. The STRAD gene, encoding an LKB1 interacting protein that activates LKB1, which subsequently leads to polarisation of cells, is an interesting candidate for a second PJS gene and a potential tumour suppressor gene in sporadic carcinomas.

METHODS

The involvement of STRAD in 42 PJS associated tumours (sporadic lung, colon, gastric, and ovarian adenocarcinomas) was studied using loss of heterozygosity (LOH) analysis of eight microsatellite markers on chromosome 17, including TP53, BRCA1, and STRAD markers.

RESULTS

Loss of the marker near the STRAD locus was seen in 13 of 29 informative cases, including all gastric adenocarcinomas. Specific LOH of the STRAD marker was found in four of 29 informative cases. For these patients all exons and exon-intron boundaries of the STRAD gene were sequenced, but no somatic mutations were identified. Furthermore, no germline STRAD mutations were found in 10 patients with PJS and family members without LKB1 germline mutation.

CONCLUSIONS

Despite the frequent occurrence of LOH in the STRAD region, these results indicate that inactivation of the STRAD gene is not essential in the sporadic adenocarcinomas studied, although it is possible that STRAD may be inactivated in different ways. In addition, no evidence was found for the hypothesis that STRAD is a second PJS susceptibility gene.

Measurement of 8-oxo-7,8-dihydro-2'-deoxyguanosine in peripheral blood mononuclear cells: optimisation and application to samples from a case-control study on cancers of the oesophagus and cardia

8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is a widely used biomarker to evaluate the level of oxidative stress. This study describes in its first part the optimisation of our analytical procedure (HPLC/electrochemical detection). Particular care was exercised to avoid artefactual oxidation and in the precision of measurement, which was evaluated with blood bags from hemochromatosis patients. The best results were obtained with a DNA extraction step using the "chaotropic method" recommended by the European Standards Committee on Oxidative DNA Damage (ESCODD). Other approaches such as anion exchange columns gave ten times as much 8-oxodG as this method. Moreover, a complete DNA hydrolysis using five different enzymes allowed improved precision. The optimised protocol was applied to peripheral blood mononuclear cells (PBMC) sampled during a case-control study on cancers of the oesophagus and cardia. With 7.2 +/- 2.6 8-oxodG/10(6) 2'-deoxyguanosines (2'-dG) (mean +/- SD), patients (n = 17) showed higher levels of 8-oxodG than controls (4.9 +/- 1.9 8-oxodG/10(6) 2'-dG, n = 43, Student's t-test: p < 0.001). This difference remained significant after technical (storage, sampling period, 2'-dG levels) and individual (age, sex, smoking, alcohol) confounding factors were taken into account (p < 0.0001, Generalised Linear regression Model). To our knowledge, this is the first report to demonstrate an increase of 8-oxodG in PBMCs of patients suffering from a cancer of the upper digestive tract. This elevated level of DNA damage in patients can raise interesting issues: is oxidative stress the cause or the result of the pathology? Could this biomarker be used to evaluate chemoprevention trials concerning digestive tract cancers?

Are carcinomas of the cardia oesophageal or gastric adenocarcinomas?

There is a clear relationship between Barrett's oesophagus and oesophageal adenocarcinoma, and between Helicobacter pylori and gastric cancer, but the histogenesis of cardiac adenocarcinomas is unknown. Some clues as to possible disease associations may be provided by the pattern of gastritis. In our study, we analysed gastritis associated with oesophageal, cardiac and gastric adenocarcinomas according to the Sydney classification. Chronic gastritis was more common in gastric (88%) than in cardiac (56%) and oesophageal adenocarcinomas (38%). H. pylori was significantly more prevalent in gastric (73%) than in cardiac (34%) or oesophageal (21%) adenocarcinomas. Our results show that factors other than H. pylori must be involved in the histogenesis of cardiac adenocarcinomas. As the pattern of gastritis and the clinical features of cardiac adenocarcinomas are more comparable to oesophageal carcinomas than gastric carcinomas, we speculate that most of these tumours share similar aetiological factors with oesophageal carcinomas.

Three different subsite classification systems for carcinomas in the proximity of the GEJ, but is it all one disease?

BACKGROUND AND AIM

Currently there are three different subsite classification systems for carcinomas in the region of the gastroesophaeal junction (GEJ), namely ICD-O, Munich and Liverpool. The aim of the present study was to compare clinicoepidemiological, pathological and molecular features of adenocarcinomas in the proximity of the GEJ, classified according to their position with respect to the GEJ initially, and then classified according to ICD-O, Munich and Liverpool classifications.

METHODS

Forty-seven adenocarcinomas in the proximity of the GEJ were subdivided into groups 1 (exclusively within esophagus), 2 (mainly within esophagus but extending distally across GEJ), 3 (equally present in esophagus and stomach) or 4 (mainly in stomach but extending proximally across GEJ), and analysis of their clinicoepidemiological, pathological and molecular features was performed. Molecular characterization included loss of heterozygosity (LOH) and microsatellite instability analyses.

RESULTS

Group 3 carcinomas were younger than other carcinomas in the proximity of the GEJ, but otherwise these carcinomas were similar in their clinicoepidemiological, pathological and molecular features. There were no significant differences between esophageal (groups 1 and 2) and gastric (groups 3 and 4) carcinomas as classified by ICD-O. Munich types I (groups 1 and 2), II (group 3) and III (group 4) carcinomas of the GEJ were also similar. LOH at the site of the Rb tumor suppressor gene and at 17p11.1-p12 was more common in GEJ (groups 2, 3 and 4) than lower third (group 1) esophageal carcinomas classified according to the Liverpool system.

CONCLUSION

Overall, adenocarcinomas of the lower esophagus and adenocarcinomas involving the GEJ have similar clinicoepidemiological, pathological and molecular features no matter which subsite classification is used, adding further evidence that they represent the same disease.

Characterisation of p53 status at the gene, chromosomal and protein levels in oesophageal adenocarcinoma

p53 mutations and loss of heterozygosity have been commonly associated with oesophageal adenocarcinoma. In this investigation, the p53 status of a Welsh population of Barrett's-associated oesophageal adenocarcinomas were fully characterised at the gene sequence, chromosomal, mRNA and protein levels. In total, 31 tumours were examined for p53 gene sequence mutations using RFLP with sequencing, allelic loss of the gene was characterised by FISH, mRNA expression by p53 pathway signalling arrays and protein levels by p53 immunohistochemistry. In all, 9.6% of adenocarcinomas harboured p53 mutations, 24% displayed p53 allelic loss and 83% exhibited p53 protein accumulation. Point mutations and deletions of the gene did not coexist within the same samples. All samples containing p53 mutations also displayed positive immunostaining; however; in the majority of cases, p53 protein accumulation developed in the absence of mutations. The gene expression analysis demonstrated no differences in p53 and mdm-2 transcription levels between the p53 immunonegative and immunopositive samples, indicating other mechanisms underlie the proteins' overexpression. In conclusion, p53 mutations and deletions do not appear to be frequent events in oesophageal adenocarcinomas; however, abnormal accumulation of the protein is present in a vast majority of cases. P53 gene mutations are not the primary cause of protein overexpression--an alternative mechanism is responsible for the positive p53 immunohistochemistry detected.

TP53 mutations in malignant and premalignant Barrett's esophagus

In order to improve the efficacy of endoscopic surveillance of Barrett's esophagus, markers of neoplastic progression in addition to dysplasia are required. The aim of the present study was to assess TP53 mutational analysis as a method of identifying patients with Barrett's esophagus who are at greatest risk of adenocarcinoma, for whom endoscopic surveillance is most appropriate. TP53 mutational analysis was initially performed on premalignant and malignant tissue from 30 patients undergoing esophagectomy for adenocarcinoma, and on premalignant biopsies from 48 patients participating in a Barrett's surveillance program. Surveillance patients were followed up endoscopically and histologically for a median of 5 years following TP53 assessment. Mutational analysis was performed by single-strand conformation polymorphism analysis and direct DNA sequencing. TP53 mutations were detected in 10 of 30 esophageal adenocarcinomas, and were more common in well-differentiated carcinomas. An identical TP53 mutation was detected in carcinoma and adjacent dysplasia. Two patients with premalignant Barrett's esophagus had TP53 mutations and one of these patients developed adenocarcinoma on follow up whilst the other has not yet progressed beyond metaplasia. No patient without TP53 mutation developed high-grade dysplasia or adenocarcinoma. TP53 mutations are detected in 33% of esophageal adenocarcinomas and in 4% of premalignant Barrett's esophagus in patients undergoing endoscopic surveillance. TP53 mutation can be detected before the development of high-grade dysplasia or carcinoma, and may be useful in stratifying the risk of adenocarcinoma in patients with Barrett's esophagus.

Primary adenocarcinomas of lower esophagus, esophagogastric junction and gastric cardia: in special reference to China

Gastric cardia adenocarcinoma (GCA) is an under-studied subject. The pathogenesis, molecular changes in the early stage of carcinogenesis and related risk factors have not been well characterized. There is evidence, however, that GCA differs from cancer of the rest of the stomach in terms of natural history and histopathogenesis. Adenocarcinomas of the lower esophagus, esophagogastric junction (EGJ) and gastric cardia have been given much attention because of their increasing incidences in the past decades, which is in striking contrast with the steady decrease in distal stomach adenocarcinoma. In China, epidemiologically, GCA shares very similar geographic distribution with esophageal squamous cell carcinoma (SCC), especially in Linzhou (formerly Linxian County), Henan Province, North China, the highest incidence area of esophageal SCC in the world. Historically, both GCA and SCC in these areas were referred to as esophageal cancer (EC) by the public because of the common syndrome of dysphagia. In Western countries, Barrett's esophagus is very common and has been considered as an important precancerous lesion of adenocarcinoma at EGJ. Because of the low incidence of Barrett's esophagus in China, it is unlikely to be an important factor in early stage of EGJ adenocarcinoma development. However, Z line up-growth into lower esophagus may be one of the characteristic changes in these areas in early stage of GCA development. Whether intestinal metaplasia (IM) is a premalignant lesion for GCA is still not clear. Higher frequency of IM observed at adjacent GCA tissues in Henan suggests the possibility of IM as a precancerous lesion for GCA in these areas. Molecular information on GCA, especially in early stage, is very limited. The accumulated data about the changes of tumor suppressor gene, such as p53 mutation, and ontogeny, such as C-erbB2, especially the similar alterations in GCA and SCC in the same patient, indicated that there might be some similar risk factors, such as nitrosamine, involved in both GCA and SCC in Henan population. The present observations also suggest that GCA should be considered as a distinct entity.

Early p53 mutations in nondysplastic Barrett's tissue detected by the restriction site mutation (RSM) methodology

Barrett's oesophagus is a premalignant condition whose incidence is rising dramatically. Molecular markers are urgently needed to identify Barrett's patients at the highest risk of cancer progression. To this end, we have used a rapid molecular technique, restriction site mutation (RSM), to detect low-frequency mutations in the p53 tumour suppressor gene in premalignant Barrett's tissues of cancer-free patients. In total, 38 endoscopically diagnosed Barrett's patients with a range of histological stages of Barrett's progression, plus four control patients without Barrett's oesophagus, were analysed for early p53 mutations. Tissue samples taken from these patients (93 samples in total) were analysed for the presence of low-frequency p53 mutations at hotspot codons: 175, 213, 248, 249, 282. In total, 13 of the 38 Barrett's patients were shown to possess a p53 mutation in at least one sample (no mutations in the four control patients). Although no statistically significant associations were found, p53 mutations reflected histological progression in Barrett's patients with p53 mutations found in 30% of metaplasia patients (P=0.4) and low-grade dysplasia patients (P=0.33) and 45% of high-grade dysplasia patients (P=0.15). Detected p53 mutations were mainly GC to AT transitions at CpG sites.

Losses of heterozygosity on chromosomes 9p and 17p are frequent events in Barrett's metaplasia not associated with dysplasia or adenocarcinoma

OBJECTIVE

Losses of heterozygosity (LOH) on chromosomes 9p and 17p frequently accompany malignant transformation of Barrett's esophagus (BE). They have been reported in adenocarcinoma, dysplasia, and adjacent metaplasia of patients with long-segment BE (LSBE). This study aimed to evaluate and compare the frequency of LOH on 9p and 17p in patients with long- and short-segment BE (SSBE) without dysplasia or adenocarcinoma.

METHODS

Matched metaplasia and blood DNA were evaluated for LOH on chromosomes 9p and 17p in patients with a previous diagnosis of BE and no dysplasia or cancer.

RESULTS

We included 18 patients (12 long-segment BE and six short-segment BE). The overall prevalence of LOH was 61% (10 of 18), with no significant difference between LSBE (58%) and SSBE (50%). The frequencies of LOH on 9p and 17p were similar (35% and 39%, respectively), with 18% of the patients showing losses at both chromosomes.

CONCLUSIONS

LOH on 9p and 17p are highly frequent events in BE, even in the absence of dysplasia and adenocarcinoma. The presence of these abnormalities in non-neoplastic epithelium suggests they might be useful markers for risk stratification within endoscopic surveillance programs.

TP53 and gastric carcinoma: a review

In this article, we survey the major p53 (TP53) alterations identified in gastric carcinomas and their precursors. These include p53 expression, mutations, and loss of heterozygosity (LOH). Not only are the various abnormalities summarized, but in addition there is a survey of the literature with respect to the impact of these changes on patient prognosis and treatment response. The majority of published studies involve the immunohistochemical detection of the protein. These use different antibodies, different detection techniques, and different methods of interpretation. Therefore not surprisingly, the results of many of the studies are contradictory with one another. Overall, however, it appears that p53 alterations occur early in the development of gastric carcinoma, being present even in the nonneoplastic mucosa and they increase in frequency as one progresses along the pathway of gastric carcinoma development. p53 immunoreactivity is seen in 17%-90.7% of invasive gastric carcinomas. p53 alterations occur much more commonly in proximal lesions than in distal ones, suggesting that the molecular events leading to the development of gastric carcinoma may be very different in proximal vs. distal tumors. p53 mutations occur in 0%-77% of gastric carcinomas. The mutations are distributed widely across the gene from exons 4-11 with hot spots of mutation at codons 175, 248, 273, 282, 245, and 213. G:C>A:T transitions at CpG sites are the commonest type of mutation. At least 60% of carcinomas with mutations also exhibit p53 LOH.

Cytokeratin expression in adenocarcinomas of the esophagogastric junction: a comparative study of adenocarcinomas of the distal esophagus and of the proximal stomach

Adenocarcinomas of the esophagogastric junction form a heterogeneous group of tumors. We aimed to evaluate the value of the expression pattern of cytokeratins 7, 19, and 20 for their diagnosis and classification. A total of 85 cases of adenocarcinoma of the distal esophagus and 67 cases of adenocarcinoma of the proximal stomach, defined on strict topographical criteria, were investigated. About 90% of the adenocarcinomas of distal esophagus were positive for cytokeratins 7 and 19, in contrast to <45% of the adenocarcinomas of proximal stomach (p <0.01); 17.6% of the adenocarcinomas of the distal esophagus and 55.2% of the adenocarcinomas of the proximal stomach expressed cytokeratin 20 (p <0.01); and 74.1% of the adenocarcinomas of the distal esophagus and 23.8% of the adenocarcinomas of the proximal stomach had a CK7+/CK20- immunophenotype (p <0.01). In intestinal-type tumors a CK7+/CK20- immunophenotype had a sensitivity of 76.5%, a specificity of 84.5%, and a predictive positive value of 87.3% for the diagnosis of adenocarcinoma of the distal esophagus. Cytokeratin patterns are different in adenocarcinomas of the distal esophagus and in adenocarcinomas of the proximal stomach. A CK7+/CK20- pattern is highly suggestive of an esophageal origin and may be helpful for the correct classification of esophagogastric adenocarcinomas.

Genetic pathways involved in the progression of Barrett's metaplasia to adenocarcinoma

BACKGROUND

The prediction of which patients with Barrett's metaplasia will develop cancer is difficult. Better genetic characterization of the condition may aid clinicians in devising more effective management and follow-up strategies.

METHODS

A review was undertaken of the accumulated genetic data relating to the progression of squamous epithelium to adenocarcinoma. The normal functions of a number of cancer-related genes are described and an explanation is given of how alterations in these genes interfere with normal cell processes and lead to cancer.

RESULTS AND CONCLUSION

The main genetic alterations accompanying the progression through dysplasia to adenocarcinoma were collated from 135 papers. The principal genetic changes implicated are the loss of p16 gene expression (by deletion or hypermethylation), the loss of p53 expression (by mutation and deletion), the increase in cyclin D1 expression, the induction of aneuploidy and the losses of the Rb, DCC and APC chromosomal loci.

Inactivation of the INK4a/ARF locus and p53 in sporadic extrahepatic bile duct cancers and bile tract cancer cell lines

The tumor-suppressor genes p14(ARF), p16(INK4a) and Tp53 are commonly inactivated in many tumors. We investigated their role in the pathogenesis of 9 bile tract cancer cell lines and 21 primary sporadic extrahepatic bile duct carcinomas. p53 and p16 protein expression was examined by Western blot analysis and immunohistochemistry. Mutation screening of p53 was done by SSCP and direct sequencing. Inactivating mechanisms of p14 and p16 were addressed by screening for mutations, homozygous deletions, chromosomal loss of 9p21 (loss of heterozygosity [LOH] analysis) and promoter hypermethylation of the p14/p16 genes. p53 overexpression could be detected in 7 of 9 cell lines and 7 of 21 primary tumors, but mutations were found in 3 cell lines only. p16 expression was absent in all cell lines, due to homozygous deletion of the gene in 8 of 9 cell lines and hypermethylation of the p16 promoter in one cell line (CC-LP-1). p14 exon 1beta was homozygously deleted in 6 of 9 cell lines, while retained in CC-LP-1 and 2 additional lines. No p14 promoter hypermethylation could be detected. p16 expression was lost in 11 of 21 primary tumors. p16 promoter hypermethylation was present in 9 of 21 primary tumors, all with lost p16 expression. Allelic loss at 9p21 was detected in 13 of 21 primary tumors, 10 of 11 with lost p16 expression and 8 of 9 with methylated p16 promoter. No p14 promoter hypermethylation or p14/p16 mutations could be detected. Neither Tp53 nor p16 alterations showed obvious association with histopathologic or clinical characteristics. In conclusion, inactivation of the p16 gene is a frequent event in primary sporadic extrahepatic bile duct cancers, 9p21 LOH and promoter hypermethylation being the principal inactivating mechanisms. Therefore, p16, but not p14, seems to be the primary target of inactivation at the INK4a locus in bile duct cancers. Other mechanisms than Tp53 mutations seems to be predominantly responsible for stabilization of nuclear p53 protein in bile duct cancers.

Role of molecular biology in the follow-up of patients who have Barrett's esophagus

At present, the follow-up of patients who have Barrett's esophagus (BE) should occur within the setting of an endoscopic biopsy surveillance program and with the frequency of surveillance as proposed by the American College of Gastroenterology. In the future, patients who have BE will be further stratified according to their risk for progression to invasive carcinoma. This stratification will permit the development of more rational surveillance programs. Models that incorporate epidemiologic risk factors, reflux symptoms, and endoscopic and histologic findings will likely include panels of biomarkers for further stratification of patients as low, intermediate, or high risk. Therefore, the challenge over the next decade will be to define the role of molecular markers in endoscopic surveillance strategies and to identify additional clinically relevant molecular markers for prognosis as intermediate markers for chemoprevention and as molecular targets for novel gene therapies.

Predictors of progression in Barrett's esophagus III: baseline flow cytometric variables

OBJECTIVES

Barrett's esophagus develops in 5-10% of patients with gastroesophageal reflux disease and predisposes to esophageal adenocarcinoma. We have previously shown that a systematic baseline endoscopic biopsy protocol using flow cytometry with histology identifies subsets of patients with Barrett's esophagus at low and high risk for progression to cancer. In this report, we further examined cytometric variables to better define the characteristics that best enable DNA cytometry to help predict cancer outcome.

METHODS

Patients were prospectively evaluated using a systematic endoscopic biopsy protocol, with baseline histological and flow cytometric measurements as predictors and with cancer as the outcome.

RESULTS

A receiver operating curve analysis demonstrated that a 4N fraction cut point of 6% was optimal to discriminate cancer risk (relative risk [RR] = 11.7, 95% CI = 6.2-22). The 4N fractions of 6-15% were just as predictive of cancer as were fractions of >15%. We found that only aneuploid DNA contents of >2.7N were predictive of cancer (RR = 9.5, CI = 4.9-18), whereas those patients whose sole abnormality was an aneuploid population with DNA content of < or =2.7 had a low risk for progression. The presence of both 4N fraction of >6% and aneuploid DNA content of >2.7N was highly predictive of cancer (RR = 23, CI = 10-50). S phase was a predictor of cancer risk (RR = 2.3, CI = 1.2-4.4) but was not significant when high-grade dysplasia was accounted for.

CONCLUSIONS

Flow cytometry is a useful adjunct to histology in assessing cancer risk in patients with Barrett's esophagus. Careful examination of cytometric variables revealed a better definition of those parameters that are most closely associated with increased cancer risk.

Expression of the p53 homologue p63alpha and DeltaNp63alpha in the neoplastic sequence of Barrett's oesophagus: correlation with morphology and p53 protein

BACKGROUND

While loss of p53 function is a key oncogenic step in human tumorigenesis, mutations of p53 are generally viewed as late events in the metaplasia-dysplasia-adenocarcinoma sequence of Barrett's oesophagus. Recent reports of a series of genes (p63, p73, and others) exhibiting close homology to p53 raise the possibility that abnormalities of these p53 family members may exert their influence earlier in the sequence.

AIM

Following recent characterisation of expression of p63 and a major isoform DeltaNp63 by generation of an antiserum that recognises p63 isoforms, but not p53, our aim was a comparative study of expression of p63 protein and p53 protein in a morphologically well defined biopsy series representative of all stages of the metaplasia-dysplasia-carcinoma sequence in Barrett's oesophagus.

METHODS

A series of 60 biopsy cases representing normal oesophagus through to invasive adenocarcinoma were stained, using immunohistochemistry, with antibodies to p63 and p53. All biopsies derived from patients with endoscopic and histopathological substantiation of a diagnosis of traditional/classical Barrett's oesophagus.

RESULTS

There was exact concordance in p53 and p63 expression in more advanced forms of neoplasia, high grade dysplasia, and invasive adenocarcinoma, while p63, but not p53, was detected in the proliferative compartment of some non-neoplastic oesophageal tissue, in both squamous mucosa and in the non-neoplastic metaplastic glandular epithelium.

CONCLUSIONS

In neoplastic Barrett's oesophagus there is upregulation of both p63 and p53 while p63 isoforms may well have an important role in epithelial biology in both non-metaplastic and metaplastic mucosa of the oesophagus. While abnormalities of p53 function represent an indisputable and critical element of neoplastic transformation, other closely linked genes and their proteins have a role in both the physiology and pathophysiology of the oesophageal mucosa.

Apoptosis and cell-cycle regulatory proteins in colorectal carcinoma: relationship to tumour stage and patient survival

The quantitative assessment of apoptotic index (AI) and mitotic index (MI) and the immunoreactivity of p53, bcl-2, p21, and mdm2 were examined in tumour and adjacent normal tissue samples from 30 patients with colonic and 22 with rectal adenocarcinoma. Individual features and combined profiles were correlated with clinicopathological parameters and patient survival data to assess their prognostic value. Increased AI was significantly associated with increased bcl-2 expression (p<0.008) and the immunoprofiles that included bcl-2, but not with MI, p53, p21 or mdm2. AI was significantly associated with increased Dukes' stage from A, B to C (p<0.02) but not D, while MI showed a significant association with all Dukes' stages (p<0.05). No significant association was found between either AI or MI and prognosis. p53, p21, mdm2, and bcl-2 positivity were detected in 65.4%, 53.8%, 65.4%, and 34.6% of cases, respectively. mdm2 was significantly associated with p53 (p<0.03) and p21 (p<0.04) expression and p53 immunoreactivity was more prevalent in rectal tumours (p<0.008). In univariate survival analysis, bcl-2 overexpression was associated with more favourable patient survival (p<0.03). Positive combined patterns p53+/p21+/bcl-2+ and p21+/mdm2+/bcl-2+ (p<0.005); p53+/bcl-2+, p21+/bcl-2+, and mdm2+/bcl-2+ (p<0.01); and p53+/p21+ (p<0.02) were also associated with favourable clinical outcome. In multivariate Cox survival analysis, bcl-2 (p<0.016) and Dukes' stage (p<0.0001) were the only significant independent prognostic indicators. In conclusion, bcl-2 immunoreactivity was associated with apoptosis and could be used in combination with Dukes' stage as a means of predicting prognosis in colorectal cancer.

Molecular cytogenetic evaluation of gastric cardia adenocarcinoma and precursor lesions

Analyses of cancer incidence data in the United States and Western Europe revealed steadily rising rates over the past decades of adenocarcinomas of the esophagus and gastric cardia. Genetic information on gastric cardia adenocarcinoma and its preneoplasias is sparse. We have used comparative genomic hybridization to obtain a genome-wide overview of 20 archival gastric cardia adenocarcinomas and 10 adjacent preneoplastic lesions (4 metaplasias, 1 low-grade dysplasia, 5 high-grade dysplasias). Multiple genetic alterations were discriminated in all adenocarcinomas. Frequent loss (> or =25% of all tumors) was detected, in decreasing order of frequency, on 5q, 18q, 4q, 3p, 9p, 2q, 11q, 14q, 21q, 4p, 9q, 16q, 1p, and 8p. Frequent gain (> or =25% of all tumors) was disclosed, in decreasing order of frequency, on 20q, 7p, 8q, 1q, 7q, 20p, 17q, 13q, Xp, 6q, 8p, 19q, 5p, 6p, and Xq. Loss of the Y chromosome was found in 60% of male cases. High level amplification was frequently (>10% of all tumors) detected on 7q21, 8p22, 12p11.2, 17q12-q21, and 19q13.1-q13.2. The precursor lesions showed multiple aberrations in all high-grade dysplasias, whereas few genetic changes were discerned in LGD and metaplasias. High level amplifications were also found in high-grade dysplasias, ie, on 7q21, 8p22, and 17q12-q21. Moreover, the percentage of aberrations was not significantly different for invasive carcinomas or high-grade dysplasias. Approximately 70% of the precursor aberrations were also present in the adjacent carcinoma. Minimal overlapping regions in the preneoplasias included loss on 18q12-q21 and gains on 8q23 and 17q12-q21, suggesting involvement of genes residing in these regions. In conclusion, we have (i) created a map of genetic alterations in gastric cardia adenocarcinomas and (ii) provided evidence for the presence of a metaplasia-dysplasia-carcinoma sequence in this poorly understood type of cancer.

P53 mutation does not affect prognosis in ovarian epithelial malignancies

Mutations of the p53 tumour suppressor gene have been found in most human cancers, including ovarian epithelial malignancies. This study investigated whether the presence or absence of p53 mutation was associated with outcome following platinum-based chemotherapy in patients with ovarian cancer. DNA samples from tumour tissue and blood were obtained from 73 patients with primary tumours, 50 of whom received platinum-based adjuvant chemotherapy. Single-strand conformation polymorphism analysis and direct DNA sequencing of exons 5-8 detected mutations in 44% (32 of 73) of tumours. These were more common in late-stage (III or IV) than in early-stage disease (I or II) (p=0.03). There was no association with histological type, volume of residual disease following surgery, or initial CA125 levels. No significant association was found between p53 status and overall survival or disease-free survival following chemotherapy. Likewise, there was no correlation between p53 mutation and response to chemotherapy as defined by normalization of CA125 levels. Tumours with p53 missense mutations recurred within a significantly shorter time than those with normal p53 (p=0.04). In addition, there was a tendency for tumours with missense mutations to have a shorter disease-free survival than those with non-missense mutations, although this did not reach statistical significance (p=0.07).

Molecular biology of Barrett's adenocarcinoma

OBJECTIVE

To review the current knowledge on the genetic alterations involved in the development and progression of Barrett's esophagus-associated neoplastic lesions.

SUMMARY BACKGROUND DATA

Barrett's esophagus (BE) is a premalignant condition in which the normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. BE predisposes patients to the development of esophageal adenocarcinoma. Endoscopic surveillance can detect esophageal adenocarcinomas when they are early and curable, but most of the adenocarcinomas are detected at an advanced stage. Despite advances in multimodal therapy, the prognosis for invasive esophageal adenocarcinoma is poor. A better understanding of the molecular evolution of the Barrett's metaplasia to dysplasia to adenocarcinoma sequence may allow improved diagnosis, therapy, and prognosis.

METHODS

The authors reviewed data from the published literature to address what is known about the molecular changes thought to be important in the pathogenesis of BE-associated neoplastic lesions.

RESULTS

The progression of Barrett's metaplasia to adenocarcinoma is associated with several changes in gene structure, gene expression, and protein structure. Some of the molecular alterations already showed promise as markers for early cancer detection or prognostication. Among these, alterations in the p53 and p16 genes and cell cycle abnormalities or aneuploidy appear to be the most important and well-characterized molecular changes. However, the exact sequence of events is not known, and probably multiple molecular pathways interact and are involved in the progression of BE to adenocarcinoma.

CONCLUSIONS

Further research into the molecular biology of BE-associated adenocarcinoma will enhance our understanding of the genetic events critical for the initiation and progression of Barrett's adenocarcinoma, leading to more effective surveillance and treatment.

Molecular and clinical differences between adenocarcinomas of the esophagus and of the gastric cardia

Adenocarcinoma of the esophagus (ADCE) with Barrett's mucosa and adenocarcinoma of the cardia (ADCC) are often reported as a single pathological entity. In this study we have used strict anatomical-pathological criteria to distinguish between these two lesions and we have investigated their differences in TP53 mutations, MDM2 gene amplification, and cytokeratin expression. DNA was extracted from the tumor areas of formalin-fixed, paraffin-embedded sections in 26 ADCC and 28 ADCE patients. TP53 mutations were detected by temporal temperature gradient electrophoresis and identified by sequencing. MDM2 amplification was assessed by differential polymerase chain reaction. The expression of cytokeratins 4, 7, and 13 was examined by immunohistochemistry. In ADCC, the male to female ratio was 1.8:1, compared to 27:1 in ADCE. Five ADCC patients had a history of other neoplasms, compared to only one ADCE patient. The two types of tumor differed in the prevalence of TP53 mutations (31% in ADCC and 50% in ADCE) and of MDM2 gene amplification (19% in ADCC and 4% in ADCE), and in the pattern of expression of cytokeratin 7 (positive in 100% of ADCE and in 41% of ADCC) and cytokeratin 13 (positive in 81% of ADCE and in 36.5% of ADCC). ADCE and ADCC differ in their clinical characteristics, in the prevalence of TP53 mutations and MDM2 amplifications, and in the patterns of cytokeratin expression. These results support the notion that ADCC and ADCE are distinct pathological entities.