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B J Reid

Publications and source records attributed to B J Reid.

At least 55 records · Page 3Linked to original sources
PubMed1995

A p53-dependent mouse spindle checkpoint.

Cell cycle checkpoints enhance genetic fidelity by causing arrest at specific stages of the cell cycle when previous events have not been completed. The tumor suppressor p53 has been implicated in a G1 checkpoint. To investigate whether p53 also participates in a mitotic checkpoint, cultured fibroblasts from p53-deficient mouse embryos were exposed to spindle inhibitors. The fibroblasts underwent multiple rounds of DNA synthesis without completing chromosome segregation, thus forming tetraploid and octaploid cells. Deficiency of p53 was also associated with the development of tetraploidy in vivo. These results suggest that murine p53 is a component of a spindle checkpoint that ensures the maintenance of diploidy.

Animals↗
PubMed1995

Comparative genomic analysis of tumors: detection of DNA losses and amplification.

We demonstrate the use of representational difference analysis for cloning probes that detect DNA loss and amplification in tumors. Using DNA isolated from human tumor cell lines to drive hybridization against matched normal DNA, we were able to identify six genomic regions that are homozygously deleted in cultured cancer cells. When this method was applied in the reverse way, using normal DNA to drive hybridization against tumor cell DNA, we readily isolated probes detecting amplification. Representational difference analysis was also performed on DNAs derived from tumor biopsies, and we thereby discovered a probe detecting very frequent homozygous loss in colon cancer cell lines and located on chromosome 3p.

Animals↗
PubMed1995

Inactivation of p53 and the development of tetraploidy in the elastase-SV40 T antigen transgenic mouse pancreas.

Human pancreatic cancer develops in association with an acquired genomic instability, but the events that lead to instability are difficult to investigate because they occur sporadically and unpredictably. The elastase-SV40 T antigen transgenic mouse model of pancreatic adenocarcinoma reproducibly proceeds through a diploid --> tetraploid --> multiple aneuploid sequence of genetic abnormalities. We investigated the relationship between inactivation of p53 and development of tetraploidy in this model. Because T antigen inactivates p53 by forming a stable complex with it, we used multiparameter flow cytometry to assess p53 expression in pancreatic samples of transgenic and control mice between 8 and 24 days of age. On day 18, a cell cycle-specific inactivation of p53 developed between diploid G, and S phase and was associated with the appearance of a cycling tetraploid cell population that had p53 protein overexpression in both G1- and S-phase cells. Cytogenetic analysis of pancreatic samples confirmed the development of a tetraploid cell population. Inactivation of p53 in diploid cells of the transgenic pancreas is followed by the development of a tetraploid cell population. We have shown previously that this tetraploid intermediate is predisposed to progression to aneuploidy because it has abnormal mitotic poles. Therefore, our results suggest that inactivation of p53 by T antigen leads to formation of a tetraploid cell intermediate that is predisposed to chromosome segregation abnormalities and the development of multiple aneuploid cell populations.

Animals↗
PubMed1994

The management of high grade dysplasia and early cancer in Barrett's esophagus. A multidisciplinary problem.

BACKGROUND: The incidence of Barrett's-associated esophageal adenocarcinoma is rising, but experience in the treatment of high-grade dysplasia (HGD) or early cancer is limited. Based on an endoscopic surveillance program, the authors developed a systematic multidisciplinary approach to this problem. METHODS: Surgical resection was considered if biopsies of the Barrett's segment, performed according to a published protocol, showed invasive cancer, intramucosal carcinoma, or repeated evidence of HGD. The type of resection was based on the length of the Barrett's segment and included an en bloc lymph node dissection for staging purposes. Careful intraoperative pathologic evaluation ensured that all of the Barrett's mucosa was resected. RESULTS: From 1984 to 1993, 27 consecutive patients (23 men, 4 women), with median age of 61 years (range, 45-75 years) underwent surgical exploration. Indications for operation were invasive cancer in 17 patients, intramucosal carcinoma in 5 patients, and HGD in 5 patients. Median length of the Barrett's segment was 9 cm (range, 1-17 cm). Only 15 patients (55%) had abnormalities visible with endoscopic examination that were potentially suspicious for malignancy. Twenty-six patients underwent resection with complete removal of the Barrett's mucosa, 20 by Ivor Lewis esophagogastrectomy, and 6 by transhiatal esophagectomy. Pathologic tumor stages were: TisN0M0 in 10 patients; T1N0M0 in 11 patients; T2N0M0 in 2 patients; T3N0M0 in 3 patients; and T1NXM1 in 1 patient. There were no postoperative deaths or anastomotic leaks. Major complications occurred in 4 patients. With a median follow-up of 3.7 years, 22 patients were alive, and only 2 patients had recurrences. CONCLUSIONS: This increasingly important group of patients with HGD or early carcinoma in the Barrett's esophagus has a high chance of cure but requires careful multidisciplinary treatment by the surgeon, gastroenterologist, and pathologist.

Adenocarcinoma↗
PubMed1994

Microsatellite instability occurs frequently and in both diploid and aneuploid cell populations of Barrett's-associated esophageal adenocarcinomas.

Alterations of microsatellites consisting of extra or missing copies of these sequences occur at relatively high frequencies in sporadic and hereditary colorectal adenocarcinomas, gastric and pancreatic cancers, and at lower frequencies in endometrial, bladder, ovarian, and other carcinomas. We determined the prevalence of microsatellite instability in esophageal adenocarcinoma, Barrett's esophagus, and squamous cell carcinoma of the esophagus. Assays were performed on 105 patients, including 28 subjects with Barrett's metaplasia, 36 with Barrett's-associated adenocarcinoma, and 42 with primary esophageal squamous cell carcinoma. Flow cytometric nuclear sorting based on DNA content was performed on 25 of the adenocarcinomas prior to DNA extraction. Specimens from 11 of the 106 patients (10%) showed instability at 1 or more chromosomal loci. Instability was seen in 2 of 28 patients (7%) with Barrett's metaplasia alone, in 8 of 36 (22%) with adenocarcinoma, and in 1 of 42 (2%) with squamous cell carcinoma. Among the 25 flow cytometrically sorted adenocarcinomas, instability occurred in 8 (32%); sorted diploid nuclei from these tumors showed instability in 4 of 8 cases (50%). These data indicate that microsatellite instability occurs frequently in Barrett's-associated esophageal adenocarcinoma. They also suggest that in esophageal adenocarcinomas, microsatellite instability can develop as an early event in metaplasia and in diploid tumor cells, before aneuploidy occurs.

Adenocarcinoma↗
PubMed1994

17p allelic losses in diploid cells of patients with Barrett's esophagus who develop aneuploidy.

Inactivation of the p53 gene, located on chromosome 17p, leads to genetic instability and aneuploidy in vitro. Aneuploid cell populations from Barrett's adenocarcinomas have a high prevalence of 17p allelic losses, and there is substantial evidence that the target of these losses is the p53 gene. If 17p allelic losses lead to aneuploidy in Barrett's esophagus, then they should be present in diploid cells from patients who develop aneuploidy. We detected 17p allelic losses in diploid cells from 10 of 11 patients (91%) with Barrett's esophagus who developed aneuploid cell populations. Our data strongly suggest that 17p allelic losses precede the development of aneuploidy during neoplastic progression in Barrett's esophagus in vivo and, therefore, support in vitro evidence for the role of p53 in genetic instability.

Adenocarcinoma↗
PubMed1994

p53 mutations in Barrett's adenocarcinoma and high-grade dysplasia.

BACKGROUND/AIMS: Allelic losses of chromosome 17p and overexpression of p53 protein have been reported in Barrett's adenocarcinomas. This study aimed to determine the stage in which p53 mutations arise in neoplastic progression in Barrett's esophagus and their relationship to the clonal evolution of cancer. METHODS: Fourteen patients with high-grade dysplasia, adenocarcinoma, or both arising in Barrett's esophagus were evaluated. Flow cytometric cell sorting was used to obtain purified populations of neoplastic cells for analysis of p53 mutations. DNA was extracted, and exons 5 through 9 of the p53 gene were amplified by polymerase chain reaction. Amplified DNA was sequenced and analyzed by automated sequencing. RESULTS: Nine of the 14 patients had p53 mutations. Six of the 9 patients had regions of high-grade dysplasia that could be evaluated; all 6 had p53 mutations in high-grade dysplasia. In 3 patients, the same p53 mutations were found in both high-grade dysplasia and adenocarcinoma. All 14 patients had aneuploidy. In 4 patients, diploid cell populations could also be evaluated for p53 mutations; 3 of the 4 patients had p53 mutations in diploid cell populations. In 2 patients, the same p53 mutation was found in multiple aneuploid cell populations within a cancer. CONCLUSIONS: p53 mutations occur frequently in Barrett's adenocarcinomas. They develop in diploid cell populations. The same p53 mutations are then found in aneuploid cell populations in high-grade dysplasia, in cancer, and in multiple aneuploid cell populations in cancer.

Adenocarcinoma↗
PubMed1993

Clonal ordering of 17p and 5q allelic losses in Barrett dysplasia and adenocarcinoma.

Both 17p and 5q allelic losses appear to be involved in the pathogenesis or progression of many human solid tumors. In colon carcinogenesis, there is strong evidence that the targets of the 17p and 5q allelic losses are TP53, the gene encoding p53, and APC, respectively. It is widely accepted that 5q allelic losses precede 17p allelic losses in the progression to colonic carcinoma. The data, however, supporting this proposed order are largely based on the prevalence of 17p and 5q allelic losses in adenomas and unrelated adenocarcinomas from different patients. We investigated the order in which 17p and 5q allelic losses developed during neoplastic progression in Barrett esophagus by evaluating multiple aneuploid cell populations from the same patient. Using DNA content flow cytometric cell sorting and polymerase chain reaction, 38 aneuploid cell populations from 14 patients with Barrett esophagus who had high grade dysplasia, cancer or both were evaluated for 17p and 5q allelic losses. 17p allelic losses preceded 5q allelic losses in 7 patients, both 17p and 5q allelic losses were present in all aneuploid populations of 4 patients, and only 17p (without 5q) allelic losses were present in the aneuploid populations of 3 patients. In no patient did we find that a 5q allelic loss preceded a 17p allelic loss. Our data suggest that 17p allelic losses typically occur before 5q allelic losses during neoplastic progression in Barrett esophagus.

Adenocarcinoma↗
PubMed1993

An endoscopic biopsy protocol can differentiate high-grade dysplasia from early adenocarcinoma in Barrett's esophagus.

BACKGROUND: Surveying vs. performing resection in patients with high-grade dysplasia in Barrett's esophagus is debated because of concern about the accuracy of endoscopic biopsy diagnosis. The aim of this study was to investigate the accuracy of an endoscopic biopsy protocol in patients with neoplastic abnormalities in Barrett's epithelium without obvious esophageal cancer. METHODS: Preoperative and postoperative diagnoses in 28 patients who underwent surgery for high-grade dysplasia or early adenocarcinoma in Barrett's esophagus and compared them with 22 other patients with high-grade dysplasia who were maintained under prospective endoscopic surveillance. All 50 patients lacked gross lesions to suggest esophageal cancer. The endoscopic protocol involved rigorous, systematic acquisition of multiple, large biopsy samples. RESULTS: Overall, 64% of patients had minimal but distinct endoscopic abnormalities that were targeted for biopsies. High-grade dysplasia alone (7 patients) was differentiated from early adenocarcinoma (19 patients). Two patients with preoperative diagnoses of intramucosal adenocarcinoma had high-grade dysplasia in their resection specimens. CONCLUSIONS: This endoscopic protocol accurately detects and differentiates high-grade dysplasia from early adenocarcinoma in Barrett's esophagus. Patients with high-grade dysplasia alone in Barrett's esophagus detected by such a protocol do not necessarily require surgical resection to rule out an undiagnosed adenocarcinoma; electing for surgery should be based on other clinical considerations.

Adenocarcinoma↗
PubMed1993

Barrett's esophagus: cell cycle abnormalities in advancing stages of neoplastic progression.

BACKGROUND: Abnormal proliferation in Barrett's esophagus may predispose to the development of esophageal adenocarcinoma, but previous studies have not determined the specific cell cycle abnormalities that were associated with neoplastic progression. METHODS: Ki67/DNA content multiparameter flow cytometry and DNA content flow cytometry were used to investigate G0, G1, and S phase fractions in advancing stages of neoplastic progression in Barrett's esophagus. RESULTS: In control biopsy specimens from gastric mucosa, G1, S phase, and total Ki67-positive proliferative fractions were low, suggesting that cells were predominantly in G0. Ki67-positive G1 fractions were increased in Barrett's metaplasia. More advanced stages of neoplastic progression were characterized by a subset of biopsy specimens that had aneuploid cell populations, increased S phase fractions, or both. CONCLUSIONS: The development of increased G1 fractions is an early event in Barrett's metaplasia. Increased S phase fractions occur in a subset of specimens typically at more advanced stages of neoplastic progression and often in association with the development of aneuploidy. Neoplastic progression in Barrett's esophagus is associated with at least three types of cell cycle abnormalities: (1) mobilization from G0 into G1; (2) loss of control of the G1/S phase transition; and (3) accumulation in G2.

Aneuploidy↗
PubMed1992

Loss of heterozygosity involves multiple tumor suppressor genes in human esophageal cancers.

Loss of heterozygosity occurring on various chromosomes has been described in the majority of human tumors. The targets of frequent or consistent subchromosomal deletions are believed to be tumor suppressor genes. We examined 72 esophageal tumors (46 squamous cell carcinomas and 26 adenocarcinomas) for loss of heterozygosity at the p53, Rb, APC, MCC, and DCC loci. Inclusion of these tumor suppressor genes in the allelic deletions was directly ascertained by performing polymerase chain reaction at polymorphic sites within the genes. Loss of heterozygosity occurred in 55% of informative cases at p53, in 48% of informative cases at Rb, in 66% at APC, in 63% at MCC, and in 24% at DCC. Ninety-three % of tumors informative at all loci (fully informative) lost heterozygosity of at least one locus. A high percentage of fully informative tumors (71%) also lost heterozygosity at more than one locus. There were no significant differences among histological types in the prevalence of loss of heterozygosity at any locus. There were correlations of losses involving MCC versus DCC, Rb, and p53. These data suggest that (a) allelic deletions including these tumor suppressor genes are important in the formation and/or progression of most esophageal cancers; (b) allelic deletions involving MCC may not occur independently of deletions involving other tumor suppressor genes; and (c) the accumulation of multiple allelic deletions involving specific tumor suppressor genes may be important in most esophageal tumorigenesis or tumor evolution.

Adenocarcinoma↗
PubMed1992

Persistent clonal areas and clonal expansion in Barrett's esophagus.

Three patients with Barrett's esophagus who had cytogenetic abnormalities detected in their metaplastic epithelium developed high-grade dysplasia or adenocarcinoma during prospective surveillance over a period of 1.5 to 6 years. In the 3 cases, cytogenetic abnormalities that were associated with the most advanced histological lesions were present in samples obtained 11, 25, and 48 months prior to the diagnosis of high-grade dysplasia or carcinoma. In a fourth patient, marker chromosomes found in a Barrett's adenocarcinoma were also present in an esophageal region spatially removed from the tumor. In all four patients, clonal cytogenetic abnormalities were present in samples obtained at widespread locations in the Barrett's segment. These observations suggest that in some patients with Barrett's esophagus clonal proliferations arise in regions of benign histology and spread to involve large areas of Barrett's mucosa. These clones persisted when the disease progressed to high-grade dysplasia or adenocarcinoma.

Adenocarcinoma↗
PubMed1992

Loss of heterozygosity involving the APC and MCC genetic loci occurs in the majority of human esophageal cancers.

The tumor suppressor gene APC was recently identified, and the cDNA was cloned from chromosome 5q21. Point mutations affecting APC are seen in the hereditary syndrome familial adenomatous polyposis, and point mutations in APC and a closely linked gene, MCC, as well as loss of heterozygosity involving chromosome 5q have been reported in sporadic colon cancer. To our knowledge, loss of heterozygosity involving APC or MCC or both has not yet been described in any other human cancer besides lung cancer. We used the polymerase chain reaction and DNA content flow cytometric nuclear sorting to examine 30 primary human esophageal cancers for loss of heterozygosity of APC or MCC or both. Loss of one allele was detected in 77% of 26 informative cases. These data suggest that loss of heterozygosity of regions on 5q including the APC and MCC genetic loci is involved in the development and/or progression of most human esophageal cancers. They imply that inactivation of APC, MCC, and/or a linked gene on chromosome 5q plays a role in the pathogenesis of some cancers of the upper gastrointestinal tract, as well as in colon cancer and familial adenomatous polyposis.

Adenocarcinoma↗
PubMed1992

Flow-cytometric and histological progression to malignancy in Barrett's esophagus: prospective endoscopic surveillance of a cohort.

To determine whether or not flow-cytometric evidence of aneuploidy and increased G2/tetraploid fractions predispose to neoplastic progression in Barrett's esophagus, 62 patients with Barrett's esophagus were evaluated prospectively for a mean interval of 34 months. Nine of 13 patients who showed aneuploid or increased G2/tetraploid populations in their initial flow-cytometric analysis developed high-grade dysplasia or adenocarcinoma during follow-up; none of the 49 patients without these abnormalities progressed to high-grade dysplasia or cancer (P less than 0.0001). Neoplastic progression was characterized by progressive flow-cytometric and histological abnormalities. Patients who progressed to high-grade dysplasia and carcinoma frequently developed multiple aneuploid populations of cells that were detectable flow-cytometrically. Similarly, patients appeared to progress through a phenotypic sequence that could be recognized histologically by the successive appearance of Barrett's metaplasia negative for dysplasia, abnormalities in the indefinite/low-grade dysplasia range, high-grade dysplasia, and eventually adenocarcinoma. These and prior results suggest that neoplastic progression in Barrett's esophagus occurs in a subset of patients who have an acquired genomic instability that generates abnormal clones of cells, some of which have aneuploid or increased G2/tetraploid DNA contents. With continued genomic instability, multiple aneuploid subclones may evolve, one of which may ultimately acquire the ability to invade and become an early carcinoma. The combination of histology and flow cytometry can be used to identify a subset of patients with Barrett's esophagus who merit more frequent endoscopic surveillance for the early detection of high-grade dysplasia or carcinoma.

Aneuploidy↗
PubMed1992

Evaluation of p53 protein expression in Barrett's esophagus by two-parameter flow cytometry.

Barrett's esophagus is a condition in which the normal stratified squamous epithelium is replaced by metaplastic columnar epithelium that predisposes to the development of esophageal adenocarcinoma. Neoplastic progression in Barrett's esophagus occurs by a multistep process associated with genomic instability and the development of aneuploid cell populations. p53 protein overexpression and allelic deletions on chromosome 17p have been shown to be present in some Barrett's adenocarcinomas, but the stage in neoplastic progression at which p53 protein overexpression develops has not been investigated. To determine the stages in neoplastic progression at which p53 protein overexpression could be detected, biopsy specimens from patients with Barrett's esophagus at all stages of histological progression from Barrett's metaplasia negative for dysplasia to esophageal adenocarcinoma were investigated using a multiparameter flow-cytometric assay. p53 protein overexpression was found in 1 of 21 patients (5%) with Barrett's metaplasia negative for dysplasia, 2 of 13 patients (15%) with Barrett's metaplasia with abnormalities in the indefinite/low-grade dysplasia range, 5 of 11 patients (45%) with high-grade dysplasia, and 8 of 15 patients (53%) with Barrett's adenocarcinoma (P less than 0.01). p53 protein overexpression was found in 9% of patients with Barrett's esophagus who had neither high-grade dysplasia nor adenocarcinoma. Whether or not patients whose biopsy specimens show p53 protein overexpression are at increased risk for progression to adenocarcinoma can be determined by prospective endoscopic surveillance.

Adenocarcinoma↗
PubMed1991

17p allelic deletions and p53 protein overexpression in Barrett's adenocarcinoma.

Barrett's esophagus is a condition in which the stratified squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium that predisposes to the development of esophageal adenocarcinoma. Allelic deletions of 17p and alterations of p53 including elevated p53 protein levels have been observed in many different tumors. To investigate the presence of 17p allelic deletions and p53 protein overexpression in Barrett's adenocarcinomas, we have combined the use of restriction fragment length polymorphism analysis, multiparameter flow cytometry, and DNA content cell sorting. The combined use of these methodologies permits the purification of aneuploid tumor cells for restriction fragment length polymorphism analysis of 17p allelic deletions and the evaluation of p53 protein expression by multiparameter flow cytometry in the same aneuploid tumor cell populations. We analyzed 15 aneuploid populations and one tetraploid populations from 13 Barrett's adenocarcinomas for 17p allelic deletions and p53 protein overexpression to determine whether both of these alterations are involved in carcinogenesis in Barrett's esophagus. Twelve of 13 tumors (92%) had 17p allelic deletions, and 8 of 13 tumors (62%) had p53 protein overexpression. Eight of the 12 tumors (67%) with 17p allelic deletions also had p53 protein overexpression. These data indicate that both 17p allelic deletions and p53 protein overexpression are frequently involved in carcinogenesis in Barrett's esophagus.

Adenocarcinoma↗