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Biomedical subjects

B Vogelstein

Publications and source records attributed to B Vogelstein.

At least 145 records · Page 8Linked to original sources
PubMed1994

Transcriptional regulation of basic fibroblast growth factor gene by p53 in human glioblastoma and hepatocellular carcinoma cells.

Mutations of the p53 gene are found in various human cancers. The frequency of its mutation is reported to increase during tumor progression in most tumors. In human gliomas, mutations of the p53 gene are found in about one-third of the malignant forms and in few of the benign ones, indicating their possible involvement in tumor progression. On the other hand, we have recently shown that basic fibroblast growth factor (basic FGF) plays a crucial role in tumor progression as an autocrine growth factor in tissues of human gliomas. Therefore, we hypothesized that p53 might regulate the promoter activity of the basic FGF gene, which has several GC boxes and no typical TATA box. In this study, cotransfection assays using human glioblastoma and hepatocellular carcinoma cells and establishment of stable cell lines expressing mutant-type p53 were performed. The basic FGF gene promoter was demonstrated to be regulated by p53 at the transcriptional level and its basal core promoter was found to be responsive to p53. Expression of endogenous basic FGF was also demonstrated to be activated by mutant type p53. Wild-type p53 repressed gene expression of the basic FGF and its mutant activated it in vitro, implying one of the possible pathways in tumor progression.

Carcinoma, Hepatocellular↗
PubMed1994

Allelic loss of chromosome 18q and prognosis in colorectal cancer.

BACKGROUND: Colorectal cancer occurs in approximately 150,000 people each year in the United States. Prognostic assessment influences the treatment of patients with colorectal cancer, including decisions about adjuvant therapy. We evaluated chromosome 18q allelic loss, a genetic event associated with tumor progression, as a prognostic marker for this disease. METHODS: We developed procedures to examine the status of chromosome 18q with microsatellite markers and DNA from formalin-fixed, paraffin-embedded tumors. Allelic loss of chromosome 18q was assessed in 145 consecutively resected stage II or III colorectal carcinomas. RESULTS: Among patients with stage II disease, the five-year survival rate was 93 percent in those whose tumor had no evidence of allelic loss of chromosome 18q and 54 percent in those with allelic loss; among patients with stage III disease, survival was 52 and 38 percent, respectively. The overall estimated hazard ratio for death in patients whose tumor had chromosome 18q allelic loss was 2.83 (P = 0.008) according to univariate analysis. Furthermore, chromosome 18q allelic loss remained a strong predictive factor (hazard ratio for death, 2.46; 95 percent confidence interval, 1.06 to 5.71; P = 0.036) after adjustment for all other evaluated factors, including tumor differentiation, vein invasion, and TNM stage. CONCLUSIONS: The status of chromosome 18q has strong prognostic value in patients with stage II colorectal cancer. The prognosis in patients with stage II cancer and chromosome 18q allelic loss is similar to that in patients with stage III cancer, who are thought to benefit from adjuvant therapy. In contrast, patients with stage II disease who do not have chromosome 18q allelic loss in their tumor have a survival rate similar to that of patients with stage I disease and may not require additional therapy.

Aged↗
PubMed1994

Wild-type but not mutant APC associates with the microtubule cytoskeleton.

The adenomatous polyposis coli protein (APC) is mutated in familial adenomatous polyposis patients as well as in sporadic colorectal tumors. In an attempt to further understand the function of APC, the subcellular localization of APC was examined. Wild-type and mutant forms of APC were expressed in mammalian cells and protein detected by immunofluorescence using monoclonal and polyclonal antibodies. Staining of wildtype APC protein revealed a filamentous network which extended throughout the cytoplasm and colocalized with microtubules. In striking contrast, mutant APC protein gave a diffuse cytoplasmic staining pattern. Treatment with a microtubule depolymerizing agent, nocodazole, caused APC as well as tubulin to become diffusely cytoplasmic. In addition, immunoperoxidase staining of transfected APC protein followed by transmission electron microscopy revealed staining of microtubules. These results suggest that wild-type but not mutant APC protein may be associated with the microtubule cytoskeleton.

3T3 Cells↗
PubMed1994

Paradoxical inhibition of solid tumor cell growth by bcl2.

The BCL2 gene product has been demonstrated to prevent apoptosis and provide a selective growth advantage to many cell types. We report an unexpected effect of bcl2 expression on the in vitro growth of several solid tumor cell lines. Expression of bcl2 in these cell lines resulted in growth inhibition similar to that seen with p53. In contrast, a COOH-terminal deletion mutant of bcl2 was unable to suppress growth. Thus, the bcl2 protein may exert distinct biological effects in different cell types.

Base Sequence↗
PubMed1994

The DCC gene product in cellular differentiation and colorectal tumorigenesis.

The analysis of human colorectal tumors has revealed frequent loss of heterozygosity (LOH) of the long arm of chromosome 18. A novel gene, DCC (deleted in colorectal cancer), located within the region of LOH on chromosome 18q was identified and has been implicated as a tumor suppressor gene. We have now shown that DCC encodes a membrane-bound protein of the immunoglobulin-CAM family, as demonstrated by cell-surface labeling, immunohistochemical analysis, and sequencing of cDNA clones. The DCC protein was found in axons of the central and peripheral nervous system and in differentiated cell types of the intestine. Colorectal tumors that lost their capacity to differentiate into mucus producing cells uniformly lacked DCC expression and loss of a chromosome 18q allele was often accompanied by loss of DCC expression in colon tumors. These results provide evidence that DCC encodes a cell surface-localized protein and emphasize the inverse relationship between differentiation and tumorigenesis.

Adenocarcinoma, Mucinous↗
PubMed1994

Interactions between p53 and MDM2 in a mammalian cell cycle checkpoint pathway.

Normal p53 function is required for optimal arrest of cells in the G1 phase of the cell cycle following certain types of DNA damage. Loss of this cell cycle checkpoint may contribute to tumor development by increasing the number of genetic abnormalities in daughter cells following DNA damage. The MDM2 protein is an endogenous gene product that binds to the p53 protein and is able to block p53-mediated transactivation of cotransfected reporter constructs; thus, interactions between MDM2 and p53 in this checkpoint pathway following ionizing irradiation were examined. Though increases in p53 protein by DNA damage were not abrogated by MDM2 overexpression, increased levels of MDM2, resulting either from endogenous gene amplification or from transfection of an exogenous expression vector, were associated with a reduction in the ability of cells to arrest in G1 following irradiation. In addition, expression of endogenous MDM2 was enhanced by ionizing irradiation at the level of transcription in a p53-dependent fashion. These observations demonstrate that MDM2 overexpression can inhibit p53 function in a known physiologic pathway and are consistent with the hypothesis that MDM2 may function in a "feedback loop" mechanism with p53, possibly acting to limit the length or severity of the p53-mediated arrest following DNA damage.

Animals↗
PubMed1994

Sequence-specific transcriptional activation is essential for growth suppression by p53.

Although several biochemical features of p53 have been described, their relationship to tumor suppression remains uncertain. We have compared the ability of p53-derived proteins to act as sequence-specific transcriptional (SST) activators with their ability to suppress tumor cell growth, using an improved growth-suppression assay. Both naturally occurring and in vitro derived mutations that abrogated the SST activity of p53 lost the ability to suppress tumor cell growth. Additionally, the N- and C-terminal ends of p53 were shown to be functionally replaceable with foreign transactivation and dimerization domains, respectively, with concordant preservation of both SST and tumor-suppressive properties. Only the central region of p53, conferring specific DNA binding, was required to suppress growth by such hybrid proteins. The SST activity of p53 thus appeared to be essential for the protein to function as a tumor suppressor.

Base Sequence↗
PubMed1994

An evaluation of six antibodies for immunohistochemistry of mutant p53 gene product in archival colorectal neoplasms.

Immunohistochemical detection of intranuclear p53 gene product may indicate mutation of the p53 suppressor gene on chromosome 17p. We used six commercially available antibodies for p53 immunohistochemistry on 19 archival colorectal neoplasms and compared the results with the mutation status of the p53 gene and 17p allelic deletion status. By Friedman's ranking analysis, use of mouse monoclonal antibody DO7 with Target Unmasking Fluid (TUF) for antigen retrieval was the most sensitive and specific procedure (P < 0.0001). Six of 7 cases with high expression (p53 Labeling Index > 30 per cent using a CAS 200 image analyser) had p53 mutation. Of seven tumours without expression (LI < 1 per cent), six had no mutation and one had a truncating mutation which prohibited nuclear localization of gene product. The low expression group (1 per cent < LI < 30 per cent, n = 5) consisted of three tumours without and two tumours with mutation. The sensitivity of high expression with the DO7-TUF method for p53 gene mutation was 67 per cent with specificity of 90 per cent, predictive value of a positive of 86 per cent, predictive value of a negative of 75 per cent, and efficiency of 79 per cent. This study suggests that immunohistochemistry is valuable for assessing p53 gene mutations in colorectal neoplasms, but further study is needed to elucidate the precise link between immunohistochemistry and molecular genetic alterations.

Antibodies↗
PubMed1994

The DCC gene: structural analysis and mutations in colorectal carcinomas.

DCC is a candidate tumor-suppressor gene encoding a protein with sequence similarity to cell adhesion molecules such as N-CAM. A set of overlapping YAC clones that contains the entire DCC coding region was isolated. Studies of this YAC contig showed that the DCC gene spans approximately 1.4 Mb. For elucidation of exon-intron structure, lambda phage clones containing all known coding sequences were isolated from a genomic library. These clones were used to demonstrate the existence of 29 DCC exons, and the sequences of the exon-intron boundaries were determined for each. Twenty-three polymorphic markers from chromosome 18 were then studied in a panel of primary colorectal tumors that had lost some, but not all, of chromosome 18. In most of these tumors, the region that was lost included DCC. Finally, Southern blot and PCR-based approaches were used to search for subtle mutations in several DCC exons. One tumor that had a point mutation in exon 28 was found, resulting in a proline to histidine substitution. A second tumor with a point mutation in intron 13 was also found. The regional map and genomic structure of DCC should provide the means to more extensively study DCC gene alterations and protein function in normal and neoplastic cells.

Amino Acid Sequence↗
PubMed1994

Lack of association of human polyomaviruses with human brain tumors.

Brain tumors, primarily glioblastoma multiforme, were examined for the presence of BKV DNA. DNAs extracted from 33 fresh-frozen tumors and from an additional 47 paraffin-embedded tumor tissues were tested for BKV sequences using two different primer pairs. One primer pair amplified highly conserved sequences in the early region coding for BKV and JCV T antigens. The other primer pair amplified the regulatory region of BKV-IR, a variant previously associated with human brain tumors. None of the tumors were positive for BKV or JCV DNA.

Base Sequence↗
PubMed1994

NIH3T3 cells expressing the deleted in colorectal cancer tumor suppressor gene product stimulate neurite outgrowth in rat PC12 pheochromocytoma cells.

The Deleted in Colorectal Cancer (DCC) gene is a candidate tumor suppressor gene that is predicted to encode a transmembrane polypeptide with strong similarity to the neural cell adhesion molecule (N-CAM) family. Previous studies have suggested that several different N-CAMs, when expressed in non-neuronal cell types can stimulate neurite outgrowth from PC12 rat pheochromocytoma cells. Based on the predicted structural similarity of DCC to N-CAMs, we sought to determine whether NIH3T3 cells expressing DCC could stimulate neurite outgrowth in PC12 cells. We found that NIH3T3 cell lines expressing DCC could stimulate PC12 cells to extend neurites. Supernatants from DCC-transfected NIH3T3 cells did not induce neurite outgrowth above background levels, suggesting that cell-cell interaction was required. NIH3T3 cells expressing a truncated form of DCC, lacking the majority of the cytoplasmic domain sequences, also failed to induce neurite outgrowth above the levels seen with control NIH3T3 cells, suggesting that the cytoplasmic domain of DCC was necessary for its neurite-promoting function. In contrast to NGF-mediated neurite outgrowth, the DCC-mediated response was inhibited by treatment with pertussis toxin or the combination of N- and L-type calcium channel blockers, and was unaffected by the transcriptional inhibitor cordycepin. The data suggest that the DCC protein can function in a fashion analogous to other N-CAMs to alter PC12 cell phenotype through intracellular pathways distinct from those involved in NGF signaling.

3T3 Cells↗
PubMed1994

p53 tagged sites from human genomic DNA.

The product of the tumor suppressor gene p53 binds to DNA and activates transcription from promoters containing its consensus binding site. This activity has been hypothesized to be responsible for its biological effects. However, the total number and nature of human genomic sites with which p53 can functionally interact is unknown. In this paper, we have used a Saccharomyces cerevisiae-based screen to identify human genomic sequences that activate transcription from an adjacent reporter gene in a p53-dependent manner (p53-tagged sites, PTS). Fifty-seven different PTS were identified, and the total number of such sites in the human genome was predicted to be between 200 and 300. Almost all contained two adjacent copies of the previously defined consensus 5'-PuPuPuC(A/T)(T/A)GPyPyPy-3'. Spacing between the copies was found to be critical for sequence-specific transcriptional activation in vivo. These results further refine the nature of the genomic sequences likely to be most important for p53-mediated tumor suppression.

Base Sequence↗