[Show abstract][Hide abstract] ABSTRACT: Seventy-nine esophageal carcinoma patients were studied for genetic abnormalities in the p53 and Rb tumor suppressor genes. Single-strand conformation polymorphism analysis and DNA sequencing were used to detect p53 point mutations, Northern blotting was used to examine abnormal expression of p53 and Rb, and polymerase chain reaction and Southern blotting were used to analyze allelic loss. Twenty-five cases were analyzed by DNA sequencing to detect mutations in p53. Fourteen samples contained mutations within exons 5 through 9 of p53; seven had missense mutations giving rise to single amino acid substitutions. The remaining seven (50%) contained nonsense mutations leading to premature termination, five due to single base pair substitutions, and two that were the result of frameshift mutations. In other human tumors, p53 mutations are predominantly missense mutations, but our data as well as those from other groups show that nonsense mutations are common in human esophageal cancer. All but one of the constitutionally heterozygous samples containing mutations also manifested loss of the normal p53 allele; the one exception without allelic loss contained a silent mutation, which should not have had any affect on the p53 protein product. In addition, Northern blotting analysis revealed abnormalities (altered transcript size or mRNA levels) in 5 of 7 cases involving p53 and in 2 of 7 cases analyzed for Rb. Thirty-four cases were informative for allelic loss studies of both p53 and Rb; of these, 25 (74%) lost heterozygosity of p53, Rb, or both. When point mutations and mRNA expression abnormalities were also considered, 33 of 45 (73%) tumors informative for allelic loss assays of both genes as well as for mRNA or point mutation studies showed one or more abnormalities in p53 or Rb. Our results strongly suggest that a unique profile of molecular alterations involving p53 and Rb characterizes human esophageal cancer and that these specific genetic lesions are important in the development and/or progression of most human esophageal carcinomas.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
Preview · Article · May 1992 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Abnormalities in the retinoblastoma tumor suppressor gene (Rb) have been observed in a large number of human cancers. Loss of heterozygosity is a common mode of allelic inactivation of Rb and other tumor suppressor genes. We investigated DNA from 61 primary human esophageal tumors for loss of heterozygosity at the Rb locus using a polymerase chain reaction-based restriction fragment length polymorphism assay. Of informative cases, we found loss of heterozygosity in 14 of 26 (54%) squamous cell carcinomas and 5 of 14 (36%) adenocarcinomas. These data support the hypothesis that Rb inactivation is involved in the pathogenesis and/or progression of esophageal cancer.