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Biomedical subjects

B Vogelstein

Publications and source records attributed to B Vogelstein.

At least 163 records · Page 9Linked to original sources
PubMed1994

Clinical and pathological characteristics of sporadic colorectal carcinomas with DNA replication errors in microsatellite sequences.

DNA replication errors (RERs) in repeated nucleotide sequences due to defective mismatch repair genes have been reported in a subset of sporadic colorectal carcinomas and in the majority of tumors from patients with hereditary nonpolyposis colorectal cancer syndrome (HNPCC). We detected RER in 18 cases (13%) in a prospective series of 137 sporadic stage II and III (Dukes' B and C) colorectal carcinomas. The clinical and pathological features of the RER-positive cases differed from those without RER. The patients with RER-positive cancers tended to be somewhat younger (60 +/- 5 years, range 22-83, versus 66 +/- 1, range 27-90, P = 0.2 with unequal variances) and had a marked preponderance of tumors proximal to the splenic flexure (17/18, 94%, versus 41/119, 34%, P < 0.0001). Only two RER-positive patients (11%) had a family history of colorectal cancer. In comparison to the 41 RER-negative proximal colonic cancers, RER-positive cancers had more frequent exophytic growth (P = 0.04), large size (P = 0.03), poor differentiation (P = 0.0004), extracellular mucin production (P = 0.003) and Crohn's-like lymphoid reaction (P = 0.003), and a trend toward less frequent p53 gene product overexpression by immunohistochemistry (3/17, 18%, versus 18/41, 44%, P = 0.06). We conclude that a subset of sporadic colorectal carcinomas has unique biological features that may indicate inherited germline mutation, de novo germline mutation, or somatic mutations of the mismatch repair genes involved in HNPCC.

Adult↗
PubMed1993

Molecular diagnosis of familial adenomatous polyposis.

BACKGROUND: Familial adenomatous polyposis is an inherited disease characterized by multiple colorectal tumors. The diagnosis has classically been based on the detection of multiple colorectal adenomas. The recent identification of germline mutations of the APC gene in patients with familial adenomatous polyposis makes presymptomatic molecular diagnosis possible, but the widespread distribution of the many mutations within this very large gene have heretofore made the search for such mutations impractical. We describe a novel approach that allows molecular genetic diagnosis in the majority of patients with the disease. METHODS: We screened 62 unrelated patients from the Johns Hopkins Familial Adenomatous Polyposis Registry for germline APC mutations. Primary screening was accomplished by analysis of protein synthesized in vitro from surrogate APC genes. In addition, the relative amount of transcript from each APC allele was determined with an allele-specific--expression assay. RESULTS: The protein assay revealed truncated protein in 51 of the 62 patients (82 percent). In 3 of the 11 remaining patients, the allele-specific--expression assay revealed significantly reduced expression of one allele of the APC gene. The use of these two assays in combination successfully identified germline APC mutations in 87 percent of the 62 patients. CONCLUSIONS: The protein and allele-specific--expression assays provide a practical and sensitive method for molecular diagnosis of familial adenomatous polyposis. This approach will facilitate care, allowing routine testing of subjects at risk and genetic confirmation of spontaneous mutations.

Adenomatous Polyposis Coli↗
PubMed1993

Hypermutability and mismatch repair deficiency in RER+ tumor cells.

A subset of sporadic colorectal tumors and most tumors developing in hereditary nonpolyposis colorectal cancer patients display frequent alterations in microsatellite sequences. Such tumors have been thought to manifest replication errors (RER+), but the basis for the alterations has remained conjectural. We demonstrate that the mutation rate of (CA)n repeats in RER+ tumor cells is at least 100-fold that in RER- tumor cells and show by in vitro assay that increased mutability of RER+ cells is associated with a profound defect in strand-specific mismatch repair. This deficiency was observed with microsatellite heteroduplexes as well as with heteroduplexes containing single base-base mismatches and affected an early step in the repair pathway. Thus, a true mutator phenotype exists in a subset of tumor cells, the responsible defect is likely to cause transitions and transversions in addition to microsatellite alterations, and a biochemical basis for this phenotype has been identified.

Base Sequence↗
PubMed1993

Association of the APC tumor suppressor protein with catenins.

Mutations of APC appear to initiate sporadic and inherited forms of human colorectal cancer. Although these mutations have been well characterized, little is known about the function of the APC gene product. Two cellular proteins that associate with APC were identified by nucleotide sequence analysis and peptide mapping as the E-cadherin-associated proteins alpha- and beta-catenin. A 27-residue fragment of APC containing a 15-amino acid repeat was sufficient for the interaction with the catenins. These results suggest an important link between tumor initiation and cell adhesion.

Adenomatous Polyposis Coli Protein↗
PubMed1993

WAF1, a potential mediator of p53 tumor suppression.

The ability of p53 to activate transcription from specific sequences suggests that genes induced by p53 may mediate its biological role as a tumor suppressor. Using a subtractive hybridization approach, we identified a gene, named WAF1, whose induction was associated with wild-type but not mutant p53 gene expression in a human brain tumor cell line. The WAF1 gene was localized to chromosome 6p21.2, and its sequence, structure, and activation by p53 was conserved in rodents. Introduction of WAF1 cDNA suppressed the growth of human brain, lung, and colon tumor cells in culture. Using a yeast enhancer trap, a p53-binding site was identified 2.4 kb upstream of WAF1 coding sequences. The WAF1 promoter, including this p53-binding site, conferred p53-dependent inducibility upon a heterologous reporter gene. These studies define a gene whose expression is directly induced by p53 and that could be an important mediator of p53-dependent tumor growth suppression.

Amino Acid Sequence↗
PubMed1993

In vivo cloning of PCR products in E. coli.

This report describes an efficient method to clone PCR products exploiting endogenous Escherichia coli enzymatic activities. PCR products are engineered to contain terminal sequences identical to sequences at the two ends of a linearized vector. PCR products and vector DNA are then simply co-transfected into E. coli strain JC8679, obviating the requirement for enzymatic treatment of the PCR product or in vitro ligation. The high rate of homologous recombination in this strain results in efficient incorporation of the insert into the vector, a process we refer to as in vivo cloning (IVC).

Base Sequence↗
PubMed1993

Association between wild type and mutant APC gene products.

Germline mutations of the APC gene are responsible for familial adenomatous polyposis, an autosomal dominant inherited predisposition to colorectal tumors. Mutation of the APC gene is also an early, if not initiating, event for sporadic colorectal tumorigenesis. In both cases, almost all of the currently identified mutations of APC result in the truncation of the protein. In this study, we demonstrate that truncated APC proteins can associate with the wild type APC in vivo. Using in vitro expression and immunoprecipitation, we show that the first 171 residues of APC are sufficient for APC oligomerization and that the first 45 amino acids of APC is necessary for this interaction. These results indicate that most mutant APC proteins should be able to bind to wild type APC protein and perhaps inactivate it in a dominant negative manner.

Adenomatous Polyposis Coli↗
PubMed1993

p53 Mutation and MDM2 amplification in human soft tissue sarcomas.

The p53 and MDM2 genes were analyzed in 24 human soft tissue sarcomas (11 malignant fibrous histiocytomas and 13 liposarcomas). Alterations of p53, consisting of point mutations, deletions, or overexpression, were detected in one-third (8 of 24) of the sarcomas. MDM2 gene amplification was detected in another 8 tumors, but no tumor contained an alteration of both genes. Monoclonal antibodies reactive with the human MDM2 gene product were developed, and immunohistochemical analysis revealed nuclear localization and overexpression of MDM2 in those tumors with amplified MDM2 genes. These data support the hypothesis that p53 and MDM2 genetic alterations are alternative mechanisms for inactivating the same regulatory pathway for suppressing cell growth.

Animals↗
PubMed1993

Amplification of cyclin genes in colorectal carcinomas.

The genetic status of cyclin genes was examined in a panel of 47 colorectal carcinoma cell lines. Cyclin D2 was found to be amplified in one tumor and cyclin E in another. In each of the two cases, the amplified cyclin gene was overexpressed at the protein or mRNA level. Cyclin D1, previously shown to be amplified in breast and other tumors, was not amplified in these cancers. These data suggest that a variety of cyclin genes can play a role in human tumorigenesis and that cyclins D2 and E are particularly important in a subset of colorectal neoplasms.

Carcinoma↗
PubMed1993

Oncoprotein MDM2 conceals the activation domain of tumour suppressor p53.

The tumour-suppressor gene p53 is inactivated in most human malignancies either by missense mutations or by binding to oncogenic proteins. In human soft tissue sarcomas, inactivation apparently results from MDM2 gene amplification. MDM2 is an oncogene product that may function by binding to p53 and inhibiting its ability to activate transcription. Here we show that, when expressed in Saccharomyces cerevisiae, human MDM2 inhibits human p53's ability to stimulate transcription by binding to a region that nearly coincides with the p53 acidic activation domain. The isolated p53 activation domain fused to another DNA-binding protein is also inactivated by MDM2, confirming that MDM2 can inhibit p53 function by concealing the activation domain of p53 from the cellular transcription machinery.

DNA↗
PubMed1993

The APC gene product in normal and tumor cells.

The APC gene has been found to be mutated during the development of sporadic colorectal tumors as well as in the germ line of familial adenomatous polyposis patients. To facilitate the characterization of both normal and mutant APC protein, a series of monoclonal and polyclonal antibodies specific for the APC protein was produced. When lymphoblastoid cell lines derived from seven familial adenomatous polyposis patients with known mutations were analyzed by Western blot, an approximately 300-kDa protein corresponding to the predicted size of full-length APC was detected in all 7 cell lines. In addition, truncated APC proteins corresponding to the product of the known mutated alleles could be detected in 4 of the 7 lines. Similar analysis of 23 colon carcinoma and 9 adenoma cell lines revealed truncated proteins in 24 (75%) of the cell lines. Moreover, 26 (81%) of the colon tumor lines were totally devoid of the normal, full-length protein. In contrast, Western blot analysis of 40 cell lines derived from sporadic tumors of other organs detected only full-length APC. Immunohistochemical analysis of APC in normal colonic mucosa revealed cytoplasmic staining with more intense staining in the basolateral margins of the epithelial cell. This staining was markedly increased in the upper portions of the crypts, suggesting an increased level of expression with maturation. These studies provide some initial clues to the function of the cytoplasmic protein APC and demonstrate the feasibility of identifying APC mutations by direct analysis of the APC protein.

Adenoma↗
PubMed1993

Mapping of multiple intestinal neoplasia (Min) to proximal chromosome 18 of the mouse.

The Min (multiple intestinal neoplasia) mutation of the mouse has been mapped by analyzing the inheritance of restriction fragment length polymorphisms and simple sequence length polymorphisms in progeny from two intraspecific crosses segregating for the Min mutation. Min, a mutant allele of Apc, the mouse homolog of the human APC (adenomatous polyposis coli) gene, maps to proximal chromosome 18. The synteny between Apc and Mcc, the mouse homolog of the human MCC (mutated in colorectal cancer) gene, is conserved between mouse and human, although the gene order in the Apc to Mcc interval is different from that in the APC to MCC interval.

Adenoma↗
PubMed1993

The multistep nature of cancer.

Cancer is a distinct type of genetic disease in which not one, but several, mutations are required. Each mutation drives a wave of cellular multiplication associated with gradual increases in tumor size, disorganization and malignancy. Three to six such mutations appear to be required to complete this process.

Adult↗
PubMed1993

Cell adhesion molecules as tumour suppressors.

Cell adhesion molecules, a diverse group of proteins expressed on the cell surface, have been implicated in numerous important cellular functions ranging from controlling morphogenesis to suppressing tumourigenesis. In this article, we discuss evidence supporting the idea that at least some proteins involved in cell adhesion may suppress tumourigenesis through influences on cell growth, differentiation and/or invasion. These studies suggest that some cell adhesion molecules may be encoded by tumour suppressor genes.

Journal Article↗
PubMed1992

The colorectal cancer gene hunt: current findings.

Identification of four genes, each with its own clinical significance, promises probes for early diagnosis of colorectal cancer in the near future. It also suggests possibilities for new forms of chemotherapy to offset the effects of mutated or lost genes. Given the "moving target" of metastasis, this is likely to be a more fruitful approach than gene replacement--and a more immediate one.

Adenomatous Polyposis Coli↗
PubMed1992

A mammalian cell cycle checkpoint pathway utilizing p53 and GADD45 is defective in ataxia-telangiectasia.

Cell cycle checkpoints can enhance cell survival and limit mutagenic events following DNA damage. Primary murine fibroblasts became deficient in a G1 checkpoint activated by ionizing radiation (IR) when both wild-type p53 alleles were disrupted. In addition, cells from patients with the radiosensitive, cancer-prone disease ataxia-telangiectasia (AT) lacked the IR-induced increase in p53 protein levels seen in normal cells. Finally, IR induction of the human GADD45 gene, an induction that is also defective in AT cells, was dependent on wild-type p53 function. Wild-type but not mutant p53 bound strongly to a conserved element in the GADD45 gene, and a p53-containing nuclear factor, which bound this element, was detected in extracts from irradiated cells. Thus, we identified three participants (AT gene(s), p53, and GADD45) in a signal transduction pathway that controls cell cycle arrest following DNA damage; abnormalities in this pathway probably contribute to tumor development.

Amino Acid Sequence↗