Reduction to homozygosity involving p53 in esophageal cancers demonstrated by the polymerase chain reaction

Genetic Insights in Barrett's Esophagus and Esophageal Adenocarcinoma

Beginning in the 1980s, an alarming rise in the incidence of esophageal adenocarcinoma (EA) led to screening of patients with reflux to detect Barrett's esophagus (BE) and surveillance of BE to detect early EA. This strategy, based on linear progression disease models, resulted in selective detection of BE that does not progress to EA over a lifetime (overdiagnosis) and missed BE that rapidly progresses to EA (underdiagnosis). Here we review the historical thought processes that resulted in this undesired outcome and the transformation in our understanding of genetic and evolutionary principles governing neoplastic progression that has come from application of modern genomic technologies to cancers and their precursors. This new synthesis provides improved strategies for prevention and early detection of EA by addressing the environmental and mutational processes that can determine "windows of opportunity" in time to detect rapidly progressing BE and distinguish it from slowly or nonprogressing BE.

Widespread hypomethylation occurs early and synergizes with gene amplification during esophageal carcinogenesis

Although a combination of genomic and epigenetic alterations are implicated in the multistep transformation of normal squamous esophageal epithelium to Barrett esophagus, dysplasia, and adenocarcinoma, the combinatorial effect of these changes is unknown. By integrating genome-wide DNA methylation, copy number, and transcriptomic datasets obtained from endoscopic biopsies of neoplastic progression within the same individual, we are uniquely able to define the molecular events associated progression of Barrett esophagus. We find that the previously reported global hypomethylation phenomenon in cancer has its origins at the earliest stages of epithelial carcinogenesis. Promoter hypomethylation synergizes with gene amplification and leads to significant upregulation of a chr4q21 chemokine cluster and other transcripts during Barrett neoplasia. In contrast, gene-specific hypermethylation is observed at a restricted number of loci and, in combination with hemi-allelic deletions, leads to downregulatation of selected transcripts during multistep progression. We also observe that epigenetic regulation during epithelial carcinogenesis is not restricted to traditionally defined “CpG islands,” but may also occur through a mechanism of differential methylation outside of these regions. Finally, validation of novel upregulated targets (CXCL1 and 3, GATA6, and DMBT1) in a larger independent panel of samples confirms the utility of integrative analysis in cancer biomarker discovery.

The incidence of esophageal adenocarcinoma (EA) is increasing at an alarming pace in the United States. Distinct pathological stages of Barrett's metaplasia and low- and high-grade dysplasia can be seen preceding malignant transformation. These precursor lesions provide a unique in vivo model for deepening our understanding the early steps in human neoplasia. By integrating genome-wide DNA methylation, copy number, and transcriptomic datasets obtained from endoscopic biopsies of neoplastic progression within the same individual, we are uniquely able to define the molecular events associated progression of Barrett esophagus. We show that the predominant change during this process is loss of DNA methylation. We show that this global hypomethylation occurs very early during the process and is seen even in preinvasive lesions. This loss of DNA methylation drives carcinogenesis by cooperating with gene amplifications in upregulating proteins during this process. Finally we uncovered proteins that upregulated by loss of methylation or gene amplification (CXCL1 and 3, GATA6, and DMBT1) and show their relevance by validating their levels in larger independent panel of samples, thus confirming the utility of integrative analysis in cancer biomarker discovery.

Intraperitoneal dedifferentiated liposarcoma: A case report

Dedifferentiated liposarcoma is a variant of liposarcoma with a more aggressive course. Mutations of the p53 gene have been found in different types of soft tissue sarcoma. It is generally accepted that p53 mutations in human malignant tumors are often related to a poor prognosis. In our case, analysis of p53 gene mutation in tumor samples was performed. p53 gene mutation was observed in dedifferentiated tumor tissue samples but not in well-differentiated tumor tissue samples. It has been reported that p53 gene mutation occurs most commonly in the retroperitoneum and rarely in other anatomic locations. Herein we report a case of dedifferentiated liposarcoma located at intraperitoneum.

Relationship between biomarker expression and allelic alteration in esophageal carcinoma

BACKGROUND AND AIM

Expression of biomarkers and probable allelic alterations were studied in esophagus tissue samples from patients with esophageal carcinoma.

METHODS

A total of 116 esophagus tissue samples were obtained from 25 patients with esophagus cancer. Histological studies revealed 23 samples were adenocarcinoma and 14 samples were epidermoid carcinoma while 79 samples were non-tumor. Expression of biomarkers was determined by enzyme immunoassay, and allelic alterations on chromosome 17p were performed by polymerase chain reaction (PCR) using primers D17S513 and D17S514.

RESULTS

The adenocarcinoma group exhibited an increase of matrix metalloproteinase (MMP)-1 (P < 0.0001) and sialyl Le (a) (P < 0.001) mean levels when compared with the non-tumor group. Adenocarcinoma samples from patients with more than three positive lymph nodes had lower levels of tissue-inhibitor metalloproteinase (TIMP)-1 than those with negative nodes (P < 0.0005). Positive allelic alteration was associated with high levels of MMP-1 expression (P = 0.003). Epidermoid carcinoma samples showed higher expression of MMP-1 (P < 0.0001) and TIMP-1 (P < 0.02) than non-tumor samples. Both epidermal growth factor receptor and sialyl Le (a) levels were overexpressed in tumors of patients with more than three positive lymph nodes (P < 0.005). Carcinoembryonic antigen levels were higher in tumors associated with allelic wild type group (P = 0.0001) and patients with negative lymph nodes (P < 0.05). Furthermore, variability in expression of biomarkers was observed according to sample location, and allelic alterations were also found both in tumor and in some non-tumor samples.

CONCLUSION

The data suggest that overexpression of tissue biomarkers associated with allelic alterations may have potential prognostic implications with different behavior in esophagus cancer.

NSAIDs modulate CDKN2A, TP53, and DNA content risk for progression to esophageal adenocarcinoma

BACKGROUND

Somatic genetic CDKN2A, TP53, and DNA content abnormalities are common in many human cancers and their precursors, including esophageal adenocarcinoma (EA) and Barrett's esophagus (BE), conditions for which aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed as possible chemopreventive agents; however, little is known about the ability of a biomarker panel to predict progression to cancer nor how NSAID use may modulate progression. We aimed to evaluate somatic genetic abnormalities with NSAIDs as predictors of EA in a prospective cohort study of patients with BE.

METHODS AND FINDINGS

Esophageal biopsies from 243 patients with BE were evaluated at baseline for TP53 and CDKN2A (p16) alterations, tetraploidy, and aneuploidy using sequencing; loss of heterozygosity (LOH); methylation-specific PCR; and flow cytometry. At 10 y, all abnormalities, except CDKN2A mutation and methylation, contributed to EA risk significantly by univariate analysis, ranging from 17p LOH (relative risk [RR] = 10.6; 95% confidence interval [CI] 5.2-21.3, p < 0.001) to 9p LOH (RR = 2.6; 95% CI 1.1-6.0, p = 0.03). A panel of abnormalities including 17p LOH, DNA content tetraploidy and aneuploidy, and 9p LOH was the best predictor of EA (RR = 38.7; 95% CI 10.8-138.5, p < 0.001). Patients with no baseline abnormality had a 12% 10-y cumulative EA incidence, whereas patients with 17p LOH, DNA content abnormalities, and 9p LOH had at least a 79.1% 10-y EA incidence. In patients with zero, one, two, or three baseline panel abnormalities, there was a significant trend toward EA risk reduction among NSAID users compared to nonusers (p = 0.01). The strongest protective effect was seen in participants with multiple genetic abnormalities, with NSAID nonusers having an observed 10-y EA risk of 79%, compared to 30% for NSAID users (p < 0.001).

CONCLUSIONS

A combination of 17p LOH, 9p LOH, and DNA content abnormalities provided better EA risk prediction than any single TP53, CDKN2A, or DNA content lesion alone. NSAIDs are associated with reduced EA risk, especially in patients with multiple high-risk molecular abnormalities.

Beyond Field Effect: Analysis of Shrunken Centroids in Normal Esophageal Epithelia Detects Concomitant Esophageal Adenocarcinoma

BACKGROUND AND AIMS: Because of the extremely low neoplastic progression rate in Barrett's esophagus, it is difficult to diagnose patients with concomitant adenocarcinoma early in their disease course. If biomarkers existed in normal squamous esophageal epithelium to identify patients with concomitant esophageal adenocarcinoma, potential applications would be far-reaching. The aim of the current study was to identify global gene expression patterns in normal esophageal epithelium capable of revealing simultaneous esophageal adenocarcinoma, even located remotely in the esophagus. METHODS: Tissues comprised normal esophageal epithelia from 9 patients with esophageal adenocarcinoma, 8 patients lacking esophageal adenocarcinoma or Barrett's, and 6 patients with Barrett's esophagus alone. cDNA microarrays were performed, and pattern recognition in each of these subgroups was achieved using shrunken nearest centroid predictors. RESULTS: Our method accurately discriminated normal esophageal epithelia of 8/8 patients without esophageal adenocarcinoma or Barrett's esophagus and of 6/6 patients with Barrett's esophagus alone from normal esophageal epithelia of 9/9 patients with Barrett's esophagus and concomitant esophageal adenocarcinoma. Moreover, we identified genes differentially expressed between the above subgroups. Thus, based on their corresponding normal esophageal epithelia alone, our method accurately diagnosed patients who had concomitant esophageal adenocarcinoma. CONCLUSIONS: These global gene expression patterns, along with individual genes culled from them, represent potential biomarkers for the early diagnosis of esophageal adenocarcinoma from normal esophageal epithelia. Genes discovered in normal esophagus that are differentially expressed in patients with vs. without esophageal adenocarcinoma merit further pursuit in molecular genetic, functional, and therapeutic interventional studies.

Molecular targets for treatment of Barrett's esophagus

SUMMARY. Esophageal cancer is one of the most deadly forms of gastrointestinal cancer with a mortality rate exceeding 90%. The major risk factors for esophageal adenocarcinoma are gastroesophageal reflux disease (GERD) and its sequela, Barrett's esophagus. GERD commonly leads to esophagitis. In a minority of patients however, ongoing GERD leads to replacement of esophageal squamous mucosa with metaplastic, intestinal-type Barrett's mucosa. In the setting of continued peptic injury, Barrett's mucosa can give rise to esophageal adenocarcinoma. Despite the widespread use of potent acid suppressive therapies for patients with GERD, the incidence of esophageal adenocarcinoma, among white men in the USA, the UK and Europe has continued to rise. Cancers in Barrett's esophagus arise through a sequence of genetic events that endow the cells with six essential physiologic hallmarks of cancer as described by Hanahan and Weinberg in 2000. These cancer hallmarks include the ability to proliferate without exogenous stimulation, to resist growth-inhibitory signals, to avoid triggering the programmed death mechanism (apoptosis), to resist cell senescence, to develop new vascular supplies (angiogenesis), and to invade and metastasize. While the acquisition of these essential attributes is not specific to the neoplastic progression of Barrett's esophagus, this review will focus on the genetic alterations that occur in Barrett's cells that contribute to the acquisition of each of the hallmarks. Moreover, potential diagnostic and therapeutic strategies for Barrett's patients aimed at each of these cancer hallmarks will be reviewed.

Polymorphisms and mutations found in the regions flanking exons 5 to 8 of the TP53 gene in a population at high risk for esophageal cancer in South Africa

A previous study in esophageal cancer (EC) patients from South Africa showed that 17% of tumors contained somatic mutations, including small deletions, insertions, and point mutations, resulting in frameshifts or amino acid changes in exons 5-8 of the TP53 gene. In the present study, polymerase chain reaction single-strand conformation polymorphism and DNA sequence analysis were used to search for sequence variation in the regions flanking exons 5-8 in a series of 74 primary human esophageal squamous cell carcinomas (ESCC). DNA from blood from 37 of the same EC patients and 118 blood samples from the same ethnic group, originating from the Transkei region of South Africa, a high-risk area for EC, served as controls. Mutations were rarely found in the regions flanking exons 5-8, but polymorphisms were frequent. Two mutations (G-->A, codon 331; G-->T, donor splice site) were found in the exon 9 region, while four polymorphisms occurred in intron 3 (16 bp duplication) and exon 4 (C-->A, codon 34; G-->C, codon 36; G-->C, codon 72) regions. Loss of heterozygosity occurred for the 16 bp polymorphism in the EC patients, but not in the controls. Certain genotypes were common in the EC group while others were common in the control group. Graphic representation illustrates the various mutations/polymorphisms found in the TP53 gene in samples from EC patients from South Africa. The results indicate that various small deletions and insertions occur at direct repeat sequences and can be explained by slipped mispairing. The point mutations include the polymorphism in codon 72 (Arg-->Pro), which has recently been associated with an increased risk of developing human papilloma virus-associated cancers.

Barrett's esophagus: clinical characteristics

Barrett's metaplasia develops in 6-14% of individuals with gastroesophageal reflux. Barrett's adenocarcinomas are increasing in epidemic proportions for as yet unknown reasons, approximately 0.5-1% of patients with Barrett's will develop adenocarcinoma. Heartburn duration and frequency (but not severity), male gender, and Caucasian race are major risk factors for developing cancer. Obesity and smoking are weak risk factors. Survival is determined by depth of tumor invasion (stage). Once invasion of the muscularis propia occurs, the vast majority of patients will have developed widespread metastasis, even when clinical staging studies are negative. No currently available therapy results in prolonged survival once metastases develop. Thus, the more widespread use of effective surveillance strategies is the only currently available means for reducing the morbidity and mortality associated with Barrett's adenocarcinoma.

Molecular and biologic basis of upper gastrointestinal malignancy--esophageal carcinoma

Esophageal cancer is one of the most deadly forms of gastrointestinal cancer. Even though the incidence of esophageal adenocarcinoma has been rising in Western populations over the past two decades, esophageal squamous cell carcinoma remains the predominant type of esophageal malignancy in the remainder of the world. With the recent advances in molecular biology, high-output genome wide screening has provided comprehensive profiles of molecular alterations in human esophageal carcinomas. The elucidation of the basic mechanisms of esophageal carcinogenesis brings with it the promise of developing treatment and preventive strategies that are based on the molecular biology of these tumors. The genetic alterations discussed in this article are not unique to the formation of esophageal carcinomas and represent only a fraction of the molecular changes found in these tumors. The goal of this article is to provide the clinician with a useful conceptual basis for evaluating studies on the molecular mechanisms underlying the development of esophageal carcinomas.

Review article: a conceptual approach to understanding the molecular mechanisms of cancer development in Barrett's oesophagus

Oesophageal adenocarcinoma is one of the most deadly human malignancies. Gastro-oesophageal reflux disease (GERD) has been established as a strong risk factor for oesophageal adenocarcinoma, and more than 40% of adult Americans experience regular GERD symptoms. GERD can be complicated by oesophagitis, and by replacement of oesophageal squamous mucosa with metaplastic, intestinal-type epithelium (Barrett's oesophagus) that is predisposed to malignancy. Cancers in Barrett's oesophagus arise through a sequence of genetic alterations which endow unlimited proliferative capacity upon the cells by affecting components of the cell cycle clock apparatus-the pivotal molecular machinery in the cell nucleus that controls whether a cell will proliferate, differentiate, become quiescent or die. This report describes how the genetic abnormalities that have been recognized in Barrett's oesophagus might promote carcinogenesis through effects on the cell cycle clock machinery. The goal of this review is to provide the clinician with a useful conceptual basis for evaluating studies on the molecular mechanisms underlying the progression from metaplasia to carcinoma in Barrett's oesophagus.

Molecular alterations of Barrett's esophagus on microdissected endoscopic biopsies

Alterations in proto-oncogenes and tumor suppressor genes play a role in the sequence from Barrett's metaplasia to esophageal adenocarcinoma. The present study aims to ascertain whether molecular abnormalities take place in Barrett's metaplasia and low-grade dysplasia and to correlate them with the histological features of the esophageal mucosa. Forty-one formalin-fixed, paraffin-embedded endoscopic esophageal biopsies were classified according to the type of metaplastic changes (noncolumnar fundic and cardial metaplasia; columnar metaplasia, with and without intestinal features). After microdissection samples were examined for loss of heterozygosity (LOH) using polymorphic markers on 5q (D5S82), corresponding to APC (adenomatous polyposis coli) gene, 13q (CA repeat in intron 2 position 14815 to 14998 of the retinoblastoma gene), 17p (D17S513) corresponding to p53 locus, and for p53 mutations. Molecular alterations including LOH, allelic imbalance, and microsatellite instability could be detected in all types of metaplastic changes and sporadically in the squamous epithelium adjacent to the metaplastic tissue. Molecular alterations involving microsatellites D5S82 and the CA repeat inside the retinoblastoma gene were more frequent in nonintestinal metaplasia whereas those involving the p53 locus took place in columnar intestinal metaplasia and in low-grade dysplasia. Clonal changes were demonstrated in different metaplastic areas in three patients. Genetic alterations comprising LOH and microsatellite instability characterize Barrett's mucosa and appear related to the type of metaplastic change. Some of them precede the development of intestinal metaplasia, suggesting that genetic alterations take place earlier than previously thought.

Analysis for loss of heterozygosity (LOH) of p53 allele in tumors derived from p53+/- and CD-1 mice following repeated subcutaneous injections of solutions containing antioxidants

Genomic DNA was isolated from subcutaneous masses observed in CD-1 and p53+/- heterozygous mice during the course of carcinogenicity studies in the vehicle control groups. These masses resulted after daily subcutaneous injection of an antioxidant vehicle with a pH adjusted to 3-4. The vehicle was 1.0% ascorbic acid plus 0.05% sodium metabisulfite in 0.75% saline in a dosing volume of 10 ml/kg/day. These masses were first palpable after 13 and 37 weeks of dosing among p53+/- and CD-1 mice, respectively. By week 26, the incidence of these masses was 89% and 80% in male and female p53+/- mice, respectively (n = 15 mice/sex) and was 0% in both male and female CD-1 mice (n = 60 mice/sex). These masses originated from panniculus carnosus muscle. Histopathological examination of the p53+/- mouse masses indicated the tumors to be sarcomas of spindle-cell origin. The histopathological examination of the masses in the CD-1 mice revealed fibrosarcomas. Five mice/sex/strain were randomly selected from a pool of mice that developed these masses in the course of the two studies. Frozen tissues from these masses were used to examine the DNA for loss of the functional p53 allele in the p53+/- mice (i.e., loss of heterozygosity, or LOH) or for loss of one of the alleles in the wild type (p53+/+) CD-1 mice by the polymerase chain reaction (PCR) technique. Loss of the functional allele was observed only in the tumor from one p53+/- male mouse. These results support a nongenotoxic mechanism for these injection site masses.

Selective genetic analysis of p53 immunostain positive cells

The isolation of p53 immunostain positive cells from histological sections for molecular genetic studies is a difficult task, especially if there are few positive cells. To eliminate contaminating DNA from p53 negative cells, which can obscure the results of molecular assays, a variation on the technique of immunohistoselective sequencing was developed. This is a highly selective approach, whereby immunostained sections of formalin fixed, paraffin wax embedded tissue are exposed to ultraviolet irradiation to damage the DNA in p53 negative cells. The DNA in positive cells remains unaffected because the dark immunostain protects their nuclei from ultraviolet light. Polymerase chain reaction single strand conformation polymorphism of samples enriched with p53 immunostain positive cells has shown that this method can produce pure samples of mutated DNA. The isolation of DNA from minority immunostain positive cells allows a wide range of molecular analyses to be carried out on these samples, which would otherwise be hampered by the problem of contaminating background cells.

Barrett's esophagus. Reducing the risk of progression to adenocarcinoma

Barrett's metaplasia develops in 6% to 14% of individuals with gastroesophageal reflux. Barrett's adenocarcinomas are increasing in epidemic proportions for, as yet unknown, reasons; approximately 0.5% to 1% of patients with Barrett's metaplasia develop adenocarcinoma. Heartburn duration and frequency (but not severity), male gender, and white race are major risk factors for developing cancer. Obesity and smoking are weak risk factors. Survival is determined by depth of tumor invasion (stage). Once invasion of the muscularis propria occurs, most patients have developed widespread metastasis, even when clinical staging studies are negative. No currently available therapy results in prolonged survival once metastases develop. Thus, the more widespread use of effective surveillance strategies is the only currently available means for reducing the morbidity and mortality associated with Barrett's adenocarcinoma.

Metallothionein expression correlates with metastatic and proliferative potential in squamous cell carcinoma of the oesophagus

The goal of this study is to clarify whether the expression of metallothionein (MT) could affect the prognosis and the metastatic potential of squamous cell carcinoma (SCC) of the oesophagus. In paraffin-embedded specimens resected from 57 patients, MT mRNA and protein expressions were detected by in situ hybridization and immunohistochemistry respectively. The expression of MT was evaluated in respect of clinicopathologic variables and patients' survival. MT mRNA expression was significantly associated with the proportion of lymph node metastasis (71% in MT mRNA-positive tumours vs 42% in MT mRNA-negative tumours; P = 0.0343) and that of distant metastasis (29% in MT mRNA-positive tumours vs 5% in MT mRNA-negative tumours; P = 0.0452). In respect of MT protein expression, the frequency of distant metastasis was more common in MT-positive tumours than in MT-negative tumours (30% in MT-positive tumours vs 8% in MT-negative tumours; P = 0.0446). The survival rate of the patients with MT protein-negative tumours was significantly better than that of the patients with MT protein-positive tumours (P = 0.0340). There was a positive correlation between the expression of MT protein and that of proliferating cell nuclear antigen (P = 0.0018). Therefore, we conclude that MT expression, both at the mRNA and protein levels, may be a potential marker predicting metastatic and proliferative activities of oesophageal SCC.

p53 and cyclin A protein expression in squamous carcinoma of the oesophagus

The aim of this study was to explore the relationship between p53 and cyclin A immunostaining in squamous carcinomas of the oesophagus. It has been shown that both these proteins are overexpressed in poorly differentiated endometrial carcinomas. Fifty oesophagectomy specimens were analysed for p53 and cyclin A immunoexpression. This was correlated with patient age and gender and tumor stage and grade. Forty-two percent of cases were p53 positive, while 94% of the squamous cancers expressed cyclin A protein. Neither protein showed any statistically significant correlation with clinicopathological parameters. This study has demonstrated that only 42% of oesophageal squamous carcinomas from South Africa express p53 protein, while the vast majority (94%) express cyclin A protein. Neither of these proteins showed any relationship to each other or any clinical feature or the tumor grade or stage.

The antiapoptotic decoy receptor TRID/TRAIL-R3 is a p53-regulated DNA damage-inducible gene that is overexpressed in primary tumors of the gastrointestinal tract

Both DR4 and DR5 have recently been identified as membrane death receptors that are activated by their ligand TRAIL to engage the intracellular apoptotic machinery. TRID (also named as TRAIL-R3) is an antagonist decoy receptor and lacks the cytoplasmic death domain. TRID protects from TRAIL-induced apoptosis by competing with DR4 and DR5 for binding to TRAIL. TRID has been shown to be overexpressed in normal human tissues but not in malignantly transformed cell lines. DR5 is a p53-regulated gene and we have recently reported that DR5 expression is induced in response to genotoxic stress in both a p53-dependent and independent manner (Sheikh et al., 1998). In the current study, we demonstrate that TRID gene expression is also induced by the genotoxic agents ionizing radiation and methyl methanesulfonate (MMS) in predominantly p53 wild-type cells, whereas UV-irradiation does not induce TRID gene expression. Consistent with these results, exogenous wild-type p53 also upregulates the expression of endogenous TRID in p53-null cells. Thus, TRID appears to be a p53 target gene that is regulated by genotoxic stress in a p53-dependent manner. Using primary gastrointestinal tract (GIT) tumors and their matching normal tissue, we also demonstrate for the first time that TRID expression is enhanced in primary tumors of the GIT. It is, therefore, possible that TRID overexpressing GIT tumors may gain a selective growth advantage by escaping from TRAIL-induced apoptosis.

Gene mutation of transforming growth factor beta1 type II receptor in hepatocellular carcinoma

Alteration of transforming growth factor beta1 (TGF-beta1) type II receptor (RII) appears to cause unresponsiveness to TGF-beta1 in tumorigenic cells. Defect in the mononucleotide repeat sequence, i.e., poly A region of TGF-beta1RII gene has been reported to be related to replication error-positive cancer cells. We examined if there is any TGF-beta1RII mutation in a coding microsatellite in hepatocellular carcinoma (HCC). Genomic DNAs were extracted from formalin-fixed, paraffin-embedded liver tissues obtained at surgery or autopsy in 3 normal individuals and 96 patients with hepatitis C virus-induced chronic liver disease; 3 with chronic hepatitis, 20 with liver cirrhosis and 73 with HCC. The DNA was PCR-amplified at 2 segments of TGF-beta1RII: poly A region which includes the (A)10 microsatellite sequence, and poly GT region. PCR products were directly sequenced. DNA from normal and patients with chronic liver disease contained the 10 wild-type adenines but 3 cases with liver cirrhosis in whom there were only 9 adenines within poly A tract. This microdeletion of one A resulted in a frameshift and truncated a predicted length of amino acids. In HCC lesions, the same deletion was noted in 4 cases (25%) of well-differentiated type, 10 (40%) of moderately differentiated type, 18 (53%) of poorly differentiated type. None of the lesions had mutations within the GT region. Our findings indicate that one adenine deletion of poly A microsatellite tract within TGF-beta1RII is frequently detected in patients with HCC, and the mutation may cause the abrogation of the function of TGF-beta1RII gene.

Loss of heterozygosity of p53 gene of oral cancer detected by exfoliative cytology

The p53 tumor suppressor gene is a 16-20-kb section of cellular DNA located on the short arm of human chromosome 17 at position 17 P 13.1. Allelic deletions and/or point mutations in p53 gene are now known to be associated with the development of carcinogenesis. A hallmark of p53 is that both alleles are generally altered during transformation, which usually represents a loss of heterozygosity (LOH). In this study 30 normal dental students and 22 oral cancer patients were collected from the affiliated hospital of Chung Shan Medical and Dental College, Taichung, Taiwan. Extractions of DNA from the buccal mucosa or cancer surface were sampled by cytology brush. The two polymorphic restriction sites exon 4 and intron 6 within the p53 gene were amplified with polymerase chain reactions followed by restriction fragment length polymorphism assay. In heterozygous individuals, 66% of oral cancers demonstrated loss of p53 gene heterozygosity at the exon 4 site, and 50% showed LOH at the intron 6 site. These results indicate that inactivation of p53 gene is associated with development and/or progression of oral cancer. The essential advantages of oral exfoliative cytology are the non-invasiveness, painlessness, rapidity, ease and cost-effectiveness of cell sampling and DNA extraction. Furthermore, this experimental assay might be useful for preliminary screening of carcinogenesis in human beings.

Expression of Bcl-2 protein is decreased in colorectal adenocarcinomas with microsatellite instability

Bcl-2 is known to inhibit apoptosis and is thought to play a role in colorectal tumour development. Studies of the promoter region of bcl-2 have indicated the presence of a p53 responsive element which downregulates bcl-2 expression. Since p53 is commonly mutated in colorectal cancers, but rarely in those tumours showing microsatellite instability (MSI), the aim of this study was to examine the relationship of bcl-2 protein expression to MSI, as well as to other clinicopathological and molecular variables, in colorectal adenocarcinomas. Expression of bcl-2 was analysed by immunohistochemistry in 71 colorectal cancers which had been previously assigned to three classes depending upon their levels of MSI. MSI-high tumours demonstrated instability in three or more of six microsatellite markers tested, MSI-low tumours in one or two of six, and MSI-null in none of six. Bcl-2 expression in tumours was quantified independently by two pathologists and assigned to one of five categories, with respect to the number of cells which showed positive staining: 0, up to 5%; 1, 6-25%; 2, 26-50%; 3, 51-75%; and 4, > or =76%. Bcl-2 negative tumours were defined as those with a score of 0. Bcl-2 protein expression was tested for association with clinicopathological stage, differentiation level, tumour site, age, sex, survival, evidence of p53 inactivation and MSI level. A significant association was found between bcl-2 expression and patient survival (P = 0.012, Gehan Wilcoxon test). Further, a significant reciprocal relationship was found between bcl-2 expression and the presence of MSI (P = 0.012, Wilcoxon rank sum test). We conclude that bcl-2 expressing colorectal cancers are more likely to be MSI-null, and to be associated with improved patient survival.

p53 alterations in oesophageal cancer: association with clinicopathological features, risk factors, and survival

AIM

To characterise the spectrum of p53 alterations (gene mutations and protein accumulation) in a consecutive series of surgically resected oesophageal cancers, and to evaluate associations with clinicopathological findings (age, sex, tumour histology, grade, and stage), potential risk factors (alcohol, tobacco, hot beverage consumption, history of gastrooesophageal reflux disease and antacid use), and survival.

METHODS

The case series comprised 61 sequentially accrued patients with primary oesophageal carcinomas. Genomic DNA was extracted from banked (frozen) tumours and matched normal mucosal tissue; p53 mutations (exons 4-10) were studied by means of polymerase chain reaction (PCR)/single strand conformation polymorphism (SSCP) analysis and DNA sequencing. Immunohistochemistry (DO7, CM1) was used to assess cell nuclear p53 protein accumulation. Risk factor data, overall and disease free survival were measured prospectively, and analysis was carried out at the univariate level using Kaplan-Meier survival curves with log rank tests, and in multivariate analysis using Cox's proportional hazards models (parsimonious and fully adjusted).

RESULTS

p53 mutations were found in 59% (36 of 61) and p53 protein accumulation was detected in 39% (24 of 61) of oesophageal cancers. Eighty eight per cent (23 of 26) of poorly differentiated tumours had p53 alterations compared with 57% (20 of 35) of moderate/well differentiated tumours (odds ratio (OR) = 5.575; p = 0.013). p53 mutations increased significantly with increasing consumption of hot beverages (measured by the average temperature of beverage, number consumed daily, and an index made by multiplying the two variables together) using both univariate (OR = 18.6; p = 0.0025) and multivariate (OR = 24.5; p = 0.0025) analysis. p53 alterations were associated with reduced disease free and overall survival (p = 0.051, log rank), with a univariate (unadjusted) hazard ratio (HR) of 2.241 (95% confidence limits (CL) = 0.973, 5.159; p = 0.058) for overall survival. By multivariate analysis adjusted for other relevant variables, the HR for tumours with p53 alterations was estimated at 2.913 (95% CL = 1.069, 7.936; p = 0.036) for overall survival.

CONCLUSIONS

This study reports novel p53 mutations (exon 10), and an association between increasing consumption of hot beverages as a risk factor for p53 mediated oesophageal cancer. p53 is a potentially useful prognostic marker in this disease.

Relationship of p53 molecular abnormalities with flow cytometry and growth factor receptor content in lung cancer

This study attempts of clarify the oncological significance of the p53 molecular abnormalities and p53 expression in lung cancer (LC) and their relationship with flow cytometry (FC) parameters and epidermal growth factor receptor (EGFR). The study includes 65 samples taken from both LC and normal lung (NL). The p53 molecular abnormalities of exons 4-8 were studied by single strand conformation polymorphisms (SSCP) and the loss of heterozygosity (LOH) of exon 4 by the Metzler method. P53 protein was detected by Western blot. EGFR was determined by a radioligand assay using [125I]EGF. The FC parameters S phase fraction (SPF), DNA index (D.I.), G1G0 and growth rate (G2M + SPF) were evaluated from cellular monosuspensions. The LC with SSCP p53 molecular abnormalities have a significantly higher EGFR content (P < 0.001), SPF (P < 0.007), D.I. (P < 0.017) and a lower proportion of G1G0 cells (P < 0.04) than LC with no molecular abnormalities. No relationship between p53 molecular abnormalities and tumor TN or evolutive events was found. Neither the relationship between the molecular results and p53 expression detected by Western blot nor that of the p53 expression detected by Western with FC parameters or EGFR could be shown. In NL the growth fraction cells decrease significantly (P < 0.05) with the intensity of p53 expression. The lack of biological functionality of p53 with molecular abnormalities seemed to relate to fast growing LC whereas p53 expression detected by Western seemed more related to the wild type of p53.

p53 mutation as the second event in juvenile chronic myelogenous leukemia in a patient with neurofibromatosis type 1

BACKGROUND

Young patients with neurofibromatosis type 1 (NF1) are at increased risk of developing various malignancies, most of which are myeloid disorders. The observed loss of NF1 allele in the myeloid malignancies of NF1 patients suggests a role of NF1 as a tumor suppressor gene. Loss of 17p was found to be quite frequent in neural crest tumors from patients with NF1, raising the possibility of p53 tumor suppressor gene involvement in other NF1-related tumors.

METHODS

The authors studied mutations in the NF1 and p53 genes, using loss of heterozygosity, single strand conformation polymorphism, heteroduplex and sequencing analyses.

RESULTS

An NF1 germline mutation was identified in exon 31 of a child who developed juvenile chronic myelogenous leukemia (JCML). The mutation was segregated within the proband's family. A 14bp deletion at exon 6 of the p53 gene was observed when JCML was diagnosed, and the wild-type p53 allele was lost during progression of the disease. No loss of the normal NF1 allele could be detected.

CONCLUSIONS

A germline mutation in the NF1 gene and sequential inactivation of p53 alleles in the malignant clone of JCML raise the possibility of a correlation between NF1 and p53 genes in the tumorigenesis of JCML.

Gene amplification of int-2 and erbB in human esophageal cancer: relationship to clinicopathological variables

Gene amplification is a relatively frequent event in human malignant tumors and is believed to play an important role in tumor progression. The int-2 and erbB genes are amplified more frequently than any other genes in human esophageal cancer. In order to investigate the correlation between these two proto-oncogenes and the clinical behavior of esophageal cancer, we examined DNA amplification of int-2 and erbB and analyzed their relationship to clinicopathological variables. Genomic DNA was extracted from 21 esophageal squamous carcinomas and normal esophageal mucosa, as well as from 4 metastatic tumors. We used Southern blot analysis for detection of gene amplification. Amplification of int-2 was observed in 13 of 21 cases (62%) and in all the metastatic tumors (4/4; 100%). We found a significant correlation between amplification of int-2 and the length of the primary lesion. Amplification of erbB was detected in 3 of 18 patients (17%). All patients who showed amplification of erbB also demonstrated amplification of int-2. These results suggest that amplification of int-2 or neighboring genes on 11q may participate in tumor progression and metastasis in patients with esophageal squamous cancer.

The molecular basis for carcinogenesis in metaplastic columnar-lined esophagus

A wide variety of biologic events and mechanisms appear to have roles in the development and progression of Barrett's esophagus-associated neoplastic lesions. Figure 5 is a schematic depiction of these events. This is known as an infernogram (named after Dante's Inferno) (S. Kern, unpublished presentations, 1996). Events at the bottom rings of the inferno are high-frequency mutations; nearer to the top of the inferno are the less common events. The next several years promise many further discoveries of not only high-frequency and low-frequency events, but also their application. Some of the molecular alterations already studied show promise as markers for early cancer detection or prognostication. Eventually, applications of these discoveries should yield new and more effective means of preventing and treating the deadly complications of this troublesome premalignant condition.

Biomarkers for malignancy in the columnar-lined esophagus

The biological mechanisms underlying the progression from normal esophageal squamous mucosa to Barrett's epithelium associated with dysplasia and finally to esophageal adenocarcinoma is becoming increasingly well understood. Histologic determination of Barrett's-associated dysplasia remains of paramount importance; however, genetic and biochemical biomarkers of Barrett's metaplasia and dysplasia will facilitate clinical diagnosis, endoscopic surveillance, and monitoring of new therapeutic interventions as they evolve. This article covers conventional and novel biomarkers in Barrett's esophagus.

Diagnosis of bladder cancer by analysis of the allelic loss of the p53 gene in urine samples using blunt-end single-strand conformation polymorphism

The novel approach of blunt-end single-strand conformation polymorphism (SSCP) has been applied in the analysis of urine samples from bladder-cancer patients for detecting loss of heterozygosity (LOH) of 3 polymorphic markers in the p53 gene. Of the 28 urine samples examined by SSCP analysis of blunt-ended DNA fragments using a fluorescence-based automated sequencer, 16 were informative in more than 1 of the 3 polymorphic markers at the p53 locus and 8 (50.0%) showed allelic loss of the p53 gene. In analysis of resected tumor tissues, LOH of the p53 gene was detected in 8 of 8 informative samples (100%) with T1 and higher stages and/or Grade 2 and Grade 3 tumors, while it was detected in 6 (75.0%) urine samples obtained from these 8 patients. This new diagnostic modality enables sensitive detection of tumor cells in urine samples and would be applicable for diagnostic bladder cancer with invasive character.

Analysis of p21Waf1/Cip1 expression in normal, premalignant, and malignant cells during the development of human lung adenocarcinoma

Our studies suggested that adenocarcinoma of the peripheral lung mostly develops by several steps from atypical adenomatous hyperplasia through early adenocarcinoma to overt adenocarcinoma, and that some p53 abnormalities play an important role in this progression. In the present study, we examined by immunohistochemistry the expression of p53-inducible cyclin-dependent kinase inhibitor p21Waf1/Cip1 (p21) in the cells at various developmental stages of lung adenocarcinoma (32 lesions of adenomatous hyperplasia, 14 of early adenocarcinoma, 23 of well differentiated adenocarcinoma, and 17 of moderately or poorly differentiated adenocarcinoma) in comparison with 19 reactive proliferative lesions and analyzed the relationship between p53 and p21 expression. Bronchioalveolar cells in the normal lung expressed very little or no p21 and no p53 expression. In not only reactive but also neoplastic lesions regardless of their developmental stage, the cells expressed p21 at various frequencies. The average labeling indices ranged from 5.4 to 13.8%, and there was no significant difference between any of these categories. The expression of p21, however, tended to be relatively low in moderately and poorly differentiated adenocarcinomas (5.5%) compared to well differentiated adenocarcinomas (12.2%), and high-level p21 expressors (10% < or = positive cells) were more frequent in the latter group (1 of 17 (6%) versus 3 of 23 (35%), P < 0.05), suggesting that p21 expression is affected by the degree of differentiation of the neoplastic cells. Although the correlation was positive between the expression of p21 and p53 in reactive lesions (r = 0.88; P < 0.001), none was found in neoplastic lesions at any step or grade (-0.12 < or = r < or = 0.26). These results indicated that p21 expression depends upon p53 expression in reactive lung cells, whereas p21 expression is at least in part independent of that of p53 from the earliest to the most fully developed step of lung adenocarcinoma tumorigenesis. We concluded that disruption of the p53-dependent cell cycle regulation is a very early event in the tumorigenesis of lung adenocarcinoma.

Microbeam MOMeNT: non-contact laser microdissection of membrane-mounted native tissue

The analysis of tissue-specific genetic alterations depends on the selective procurement of homogeneous cell populations. Microbeam microdissection of membrane-mounted native tissue (MOMeNT) permits the rapid, selective, and low-contamination procurement of tumor or other cells from histological sections by non-thermic non-contact laser microdissection. Tissue sections are mounted on a specifically designed ultrathin transparent supporter membrane. Tissue together with the membrane are then dissected with an ultraviolet (337-nm) pulsed laser microbeam coupled into a robot-stage microscope. The ultraviolet laser causes dissection by cold photolysis due to the high photon density of the microbeam rather than by local heating. The track of the laser microbeam can be preselected freely on a video screen, and the size and form of the dissectates can thus be adapted to the histological features of the section with a delineation accuracy in the micron range. Polymerase chain reaction amplification of DNA from the dissectates is not impaired, and tumor-specific loss of heterozygosity of the APC gene as well as homozygous deletion of the MTS1 gene are demonstrated in bladder carcinomas. Taken together, microbeam MOMeNT is a novel technique that utilizes membrane-based microdissection by an ultraviolet laser microbeam, thus providing a flexible, easy-to-use high-performance tool for the molecular pathologist.

Human papillomavirus type 16 DNA in esophageal carcinomas from Alaska Natives

The possible etiological role of human papillomavirus (HPV) in esophageal carcinogenesis was evaluated in Alaska Natives in whom the incidence of esophageal cancer is 1.3 and 3.8 times higher than in US Caucasian men and women, respectively. Fixed paraffin-embedded esophageal tissues from 32 cases of squamous-cell carcinoma (SCC) and 3 cases of adenocarcinoma (AC) diagnosed between 1957 and 1988 were analyzed by polymerase chain reaction (PCR) and in situ hybridization for HPV DNA sequences. Detection of the human beta-globin gene by PCR was used as a control for sufficiency of DNA and its potential for amplification in the tissue samples. Twenty-five of the tumor tissues were considered adequate for PCR analyses; HPV DNA was detected in 10 of 22 SCCs and was not found in 3 ACs. Seven of the 10 HPV-positive tissues contained sequences from the E6 gene of HPV type 16. Koilocytosis, an epithelial change consistent with HPV infection, was found in 80% of the esophageal squamous-cell tumors with HPV DNA and in 75% of those without HPV DNA. The detection of amplifiable cellular DNA was related to recentness of diagnosis; however, the detection of HPV DNA within amplifiable specimens was not related to recentness of diagnosis. A 413-bp sequence from the L1 open reading frame of HPV 16 from esophageal tissue of 2 patients was identical to sequences previously identified in cervical cells from other Alaska Natives. Our results provide molecular evidence of HPV infection, especially type 16, in archival esophageal cancer tissues from 45% of those patients whose specimens contain adequate DNA for PCR analysis.

No evidence of mutation in the human PTC gene, responsible for nevoid basal cell carcinoma syndrome, in human primary squamous cell carcinomas of the esophagus and lung

The high frequency of loss of heterozygosity that has been observed on the distal region of the long arm of chromosome 9 in squamous cell carcinomas of esophagus, lung, uterus, and head and neck indicates the presence of a tumor suppressor gene(s) in this region. To investigate the possible role of the PTC gene on chromosome 9q22.3, that was identified as the cause of nevoid basal cell carcinoma syndrome, during carcinogenesis in esophagus and lung, we examined 20 esophageal squamous cell carcinomas and 10 squamous cell carcinomas of the lung for mutations in any coding exon of PTC. Using single-strand conformation polymorphism and direct sequencing, we detected no mutations other than two non-deleterious polymorphisms. Our results suggest that inactivation of some tumor suppressor gene(s) on 9q other than PTC contributes to the development of squamous cell carcinomas in these tissues.

Mutation analysis of the p53, APC, and p16 genes in the Barrett's oesophagus, dysplasia, and adenocarcinoma

AIMS

To study the loss of heterozygosity and the presence of mutations at the p53, p16/CDKN2, and APC genes in Barrett's oesophagus, low grade dysplastic oesophageal epithelium, and adenocarcinoma of the oesophagus; to relate the presence of alterations at these genes with the progression from Barrett's oesophagus to adenocarcinoma.

METHODS

DNA was extracted from paraffin blocks containing tissue from Barrett's oesophagus (12 samples), low grade dysplasia (15 cases), and adenocarcinoma (14 cases). Loss of heterozygosity (LOH) at the p53, p16, and APC genes was determined by comparing the autoradiographic patterns of several microsatellite markers between the normal tissue and the malignant tissue counterpart. SSCP was used to determine the presence of mutations at p53 (exons 5 to 8), p16 (exon 2), and APC. Homozygous deletion of the p16 gene was defined through polymerase chain reaction followed by Southern blot.

RESULTS

LOH at the p53, p16, and APC genes was not observed in Barrett's oesophagus without dysplasia, and increased to 90% (p53), 89% (p16), and 60% (APC) in the adenocarcinomas. The p53 gene was mutated in only two adenocarcinomas (codons 175 and 245). In one case a mutation at the APC gene (codon 1297) was found. No patient had mutation at the second exon of p16. However, this gene was homozygously deleted in three of the 12 adenocarcinomas.

CONCLUSIONS

The tumour suppressor genes p53, p16, and APC are often deleted in adenocarcinomas derived from Barrett's oesophagus. Mutations at these genes are also found in the adenocarcinomas, including the homozygous deletion of the p16 gene. However, the absence of genetic alterations in the Barrett's oesophagus and the low grade dysplastic epithelia suggest that mutations at these genes develop later in the progression from Barrett's oesophagus to adenocarcinoma.

p53 protein accumulation and p53 gene mutation in esophageal carcinoma. A molecular and immunohistochemical study with clinicopathologic correlations

BACKGROUND

p53 gene mutation and p53 protein accumulation are common in human cancer. However, their clinical significance is controversial and p53 accumulation may not correlate with gene mutation. The current study investigates the occurrence of p53 alterations in esophageal carcinoma, the correlation between the analyses at the gene and protein level, and their prognostic significance.

METHODS

A series of 74 esophageal carcinomas (46 squamous cell carcinomas, 21 Barrett's adenocarcinomas, and 7 undifferentiated carcinomas) was studied by single strand conformation polymorphism (SSCP) analysis and immunohistochemistry (IHC) to detect p53 mutation and accumulation, respectively.

RESULTS

p53 mutations in exons 5-8 were detected in 53% of the carcinomas whereas p53 accumulation was observed in 57% of cases. Comparing SSCP and IHC, there were 27 discordant cases (38%). Overall, only 20 tumors (27%) did not display p53 mutation and/or p53 accumulation. No associations were found between p53 aberrations and clinicopathologic parameters, including patients age and gender tumor type, stage, and grade. p53 protein accumulation and p53 gene mutation were not related to patient survival by univariate or multivariate analysis in esophageal carcinomas.

CONCLUSIONS

p53 aberrations are very common in esophageal carcinomas. However, p53 gene mutation and p53 protein accumulation have a significant discordance, suggesting that p53 function may be inactivated by mechanisms other than mutation. p53 aberrations do not independently predict prognosis in esophageal tumors.

Correlation of allelic loss of the P53 gene and tumor grade, stage, and malignant progression in bladder cancer

BACKGROUND

We examined loss of heterozygosity (LOH) of the P53 gene in bladder cancer, and investigated the role of the P53 gene on malignant progression of papillary tumors. In addition, the clonality of recurrent bladder cancer was examined.

METHODS

LOH of the P53 gene was analyzed in 67 bladder cancers from 47 patients. DNA was extracted from formalin-fixed, paraffin-embedded tissues, amplified by the polymerase chain reaction (PCR) at 3 polymorphic loci in the P53 gene, and analyzed with nonradioisotopic single-strand conformation polymorphism (Non-RI SSCP) analysis.

RESULTS

Out of 40 informative samples, LOH was detected in 13 samples, containing 4 of 7 in grade 3 (57%), 9 of 23 in grade 2 (39%), and none of 10 in grade 1 (10%). Statistical significance was observed between the LOH in grades 1 and 2, and in grades 1 and 3. An analysis of 5 cases showing malignant progression revealed that 3 (60%) showed an LOH in the primary tumor, and 2 showed LOH in recurrent tumors, in contrast to LOH found in 3 cases of 19 (16%) not showing malignant progression. Four cases with metachronous recurrence exhibited LOH; 2 at recurrent tumors, 1 only at the initial tumor, and 1 at both tumors.

CONCLUSIONS

The alterations of the P53 gene were considered to correlate with tumor grade, and contribute to the malignant progression of bladder cancer. LOH in the P53 gene may serve as a clinical indicator for prognosis in superficial bladder cancer.

The role of the Ikaros gene in lymphocyte development and homeostasis

The Ikaros gene, which encodes a family of hemopoietic-specific zinc finger proteins, is described as a central regulator of lymphocyte differentiation. During fetal development, it is required at the earliest stage of T cell and B cell specification. In the adult, however, lymphoid lineages rely on Ikaros at distinct phases of their development. Its activity is essential for the generation of B cell but not of T cell precursors, although the differentiation of the latter is not normal. A significant increase in CD4 thymocytes and their immediate precursors is detected, and because these cells lack markers that correlate with positive selection, a deregulation in their maturation process is suggested. Furthermore, Ikaros-null thymocytes hyperproliferate in response to T cell receptor (TCR) signaling; within days after their appearance in the thymus, clonally expanding populations are detected. Deregulated TCR-mediated responses and the fast kinetics of tumor development in these mutant thymocytes implicate Ikaros as a central tumor suppressor gene for the T cell lineage. In addition, lack of natural killer cells and selective defects in gamma delta T cells and dendritic antigen-presenting cells point to Ikaros as an essential factor for the establishment of early branchpoints of the T cell pathway. The dominant interference activity of Ikaros isoforms unable to bind DNA and their effects in lymphocyte development suggest that Ikaros works in concert with other factors. The role of Aiolos, a lymphoid-restricted and structurally related gene, in lymphoid differentiation is discussed. A model is proposed that defines Ikaros as the backbone of a complex regulatory protein network that controls cell fate decisions and regulates homeostasis in the hemo-lymphoid system. Changes in this regulatory network may reflect differentiation and proliferation adjustments made in hemo-lymphoid progenitors and precursors as they give rise to the cells of our immune system.

Numerical chromosome alterations in colorectal carcinomas detected by fluorescence in situ hybridization. Relationship to 17p and 18q allelic losses

This study concerns DNA ploidy, numerical changes of chromosomes 7, 8, 10, 17 and 18, and allelic losses at chromosomes 17p13.3 (flanking the p53 gene) and 18q21 (location of the DCC gene) in 31 freshly resected colorectal tumours. Cytological smears were used to determine DNA ploidy by image analysis, and chromosome numbers by fluorescence in situ hybridization (FISH) using chromosome-specific pericentromeric alpha-satellite DNA probes. Allelic losses were assessed by Southern blotting and by the polymerase chain reaction loss of heterozygosity method. Approximately 50% of the tumours were aneuploid. There was heterogeneity with respect to chromosome numbers, but gains and losses of chromosomes, or both, were detected in all carcinomas examined, including 10 that were nonaneuploid by image analysis. Trisomy 7 was found in 74% of the tumours, and monosomy of chromosome 18 in 32%. Allelic loss at chromosome 17p13.3 was evident in 13 of 26 informative cases, and only one case exhibited monosomy 17. In comparison monosomy 18 was found in 10 cases; 7 of them corresponded to approximately half of the cases with allelic loss within the DCC gene, and the other three were noninformative. These findings indicate that the loss of one chromosome 18 is an important mechanism producing allelic deletion of the DCC gene in colorectal carcinomas. Our data also suggest that monosomy 18 is a useful indicator for studying colorectal cancer progression on a cell by cell basis.

Genetic alterations in esophageal cancer and their relevance to etiology and pathogenesis: a review

Cancer of the esophagus exists in 2 main forms with different etiological and pathological characteristics-squamous cell carcinoma (SCC) and adenocarcinoma (ADC). This review focuses on the occurrence of genetic alterations in SSC and ADC of the esophagus and on their possible implications for the elucidation of the etiology and pathogenesis of these cancers. The most common alterations found in esophageal cancers include allelic losses at chromosomes 3p, 5q, 9p, 9q, 13q, 17p, 17q and 18q, as well as mutations of p53 (mostly missense), Rb (deletions), cyclin DI (amplifications) and c-myc (amplifications). The sequence of occurrence of these alterations with respect to histopathological tumor progression is discussed. Our findings underscore the different etiology and pathogenesis of SCC vs. ADC and suggest that the genetic alterations observed may represent molecular fingerprints of critical risk involved in the development of these 2 cancers.

The molecular biology of esophageal carcinoma

There have been many new developments in our understanding of esophageal carcinoma biology over the past several years. Information regarding both of the major forms of this disease, adenocarcinoma and squamous cell carcinoma, has accumulated in conjunction with data on precursor conditions such as Barrett's esophagus. Some of the most interesting and promising findings have included aneuploidy (abnormal DNA content), amplification and overexpression of proto-oncogenes, loss of heterozygosity at multiple chromosomal loci, and tumor suppressor gene inactivation. Of particular importance is mutation and deletion involving the tumor suppressor gene p53, but abnormalities in the retinoblastoma, deleted in colon cancer, and adenomatous polyposis coli genes have been described as well. Recently, two important cancer pathways implicated in the genesis of multiple tumor types have also been inculpated in esophageal carcinogenesis: the cyclin kinase inhibitor cascade and the DNA mismatch repair process. Alterations in the p16 and p15 cyclin kinase inhibitors, including point mutation and homozygous deletion, have been reported in primary esophageal tumors and/or tumor-derived cell lines. Microsatellite instability, the hallmark of DNA mismatch repair defects, has been detected in esophageal cancers, particularly those associated with Barrett's metaplasia (where it may represent an early event). Further developments in the field of molecular carcinogenesis of esophageal malignancies promise to yield improvements in the early detection, prognostic categorization, and perhaps eventual gene-based therapy of this deadly disease.

DNA polymerase beta gene mutations in human bladder cancer

We examined 24 human bladder cancer tissues for possible mutations in the entire coding region of the human DNA polymerase beta gene using polymerase chain reaction analysis, single-strand conformational polymorphism analysis of RNA, and sequence analysis. DNA polymerase beta gene mutations were observed in four of the 24 cases (16.7%) and included three missense point mutations and a single base insertion. The single base insertion was also observed in our previous study of human prostate cancer, suggesting that this region may be a hot spot for mutation of the DNA polymerase beta gene. No clinical or pathological association was found among the four cases that contained the mutation. Three of the four cases with DNA polymerase beta gene mutation had mutations of the p16 or RB genes or loss of heterozygosity of the p53 and APC gene loci. The results of the study presented here suggest that DNA polymerase beta gene mutations, in combination with mutations of tumor suppressor genes, may be involved in certain cases of human bladder cancer.

Frequency and prognostic evaluation of 3p21-22 allelic losses in non-small-cell lung cancer

Previous loss of heterozygosity (LOH) studies of chromosome 3p loci have displayed a 60% deletion frequency in non-small-cell lung cancers (NSCLC), as opposed to small-cell lung cancers, in which the 3p deletion is consistently found. However, the high stromal-cell admixture found in NSCLC and the use of the Southern-blot method lead to under-evaluation of this frequency. In this study, we used a very precise microdissection technique followed by PCR amplification of 6 3p21-22 polymorphic genomic sequences to analyze LOH in 86 NSCLC and in normal adjacent tissue. We found the sensitivity of the microdissection-PCR-based LOH technique higher than the sensitivity of the Southern-blot technique: 87% of the squamous-cell carcinomas and 84% of the large-cell undifferentiated carcinomas showed a clear LOH for a 3p21-22 locus. All doubly informative cases but 4 showed concordant deletion at all 3p21-22 loci. The analysis of 3p microsatellite sequences displayed only 2 cases of genomic instability, one of them also displaying features of tumoral heterogeneity as regards the instability genotype. Four carcinomas in situ adjacent to these NSCLC showed the same allelic profile as the invasive tumors. The only prognostic factors in this study were the disease stage and histology. The 3p21-22 deletion was not related to the stage of the disease and did not appear to be a significant prognostic factor of survival. 3p21 loss appears, so far, to be the most frequent and the earliest genetic alteration described in NSCLC, but does not seem to carry significant prognostic information in invasive tumors.

Microsatellite instability in Japanese esophageal carcinoma

Recent studies have shown that microsatellite instability (MSI) may play an important role in the development of various types of cancer. However, there have been only 2 reports describing MSI in esophageal carcinoma and the clinicopathologic significance of MSI in this malignancy has not yet been clarified. To better elucidate the role of genetic instability in the development of esophageal carcinoma, we investigated the presence of MSI in 32 cases of esophageal cancer using paired samples of fresh frozen tumor and normal tissue by a method based on the polymerase chain reaction. MSI was defined as occurring in tumors which showed altered banding patterns at one or more microsatellite loci. The incidence of MSI in esophageal carcinoma was 6 out of 32 patients. MSI was observed more frequently in cases with small-cell carcinoma (2 out of 2) than in cases with squamous-cell carcinoma (4 out of 29). No cases with adenocarcinoma or Barrett's metaplasia were included in our series. No significant correlations between MSI and other clinicopathologic parameters were observed. The present study suggests that (1) some Japanese esophageal carcinomas certainly correlate with DNA replication error, and (2) MSI may be more frequent in small-cell carcinoma of the esophagus than in squamous-cell carcinoma of the esophagus.