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W K Cavenee

Publications and source records attributed to W K Cavenee.

At least 91 records · Page 5Linked to original sources
PubMed1995

Replacement of the p16/CDKN2 gene suppresses human glioma cell growth.

The p16/CDKN2 gene has many features of a growth suppressor gene: it maps to 9p21, a frequent region of loss of heterozygozity in a variety of tumor types; it encodes an inhibitor of cyclin-dependent kinase 4; and its homozygous deletion is common in tumor-derived cell lines. However, the lower frequency of alteration of the gene in primary tumor tissue as compared to the cognate tumor cell lines has brought this interpretation into question. We have assessed the growth suppressive function of p16/CDKN2 by gene transfer. The introduction of full-length p16/CDKN2 cDNA caused marked growth suppression in p16/CDKN2-null human glioma cells, but was without significant effect in those cells with endogenous wild-type p16/CDKN2 alleles. These results provide functional evidence in support of the hypothesis that the p16/CDKN2 gene is a functional growth suppressor gene, at least in gliomas.

Base Sequence↗
PubMed1995

Single cell monitoring of growth arrest and morphological changes induced by transfer of wild-type p53 alleles to glioblastoma cells.

Mutation of the p53 tumor suppressor gene is one of the earliest identified genetic lesions during malignant progression of human astrocytomas. To assess the functional significance of these mutations, wild-type (WT) p53 genes were introduced into glioblastoma cell lines having mutant, WT, or null endogenous p53 alleles. Populations of cells with mutant or null endogenous p53 alleles and exogenous WT p53 were spontaneously selected in culture for cells expressing only mutant p53 or no p53, which then displayed a growth and tumorigenic phenotype identical to the parental cells. To determine the phenotypic consequences of WT p53 expression before the occurrence of mutations, we developed a single cell assay to monitor WT p53-dependent transcription activity. Transfer and expression of exogenous WT p53 genes to cells with endogenous mutant or deleted, but not WT, p53 alleles caused growth arrest and morphological changes, including increased cell size and acquisition of multiple nuclei. This supports the hypothesis that genetic lesions of the p53 gene play an important role in the genesis of astrocytomas. Furthermore, the high sensitivity of the episomal single cell reporter strategy developed here has potential clinical applications in the rapid screening of patients for germ-line mutations of the p53 gene or any other gene with known targets for transcriptional transactivation.

Alleles↗
PubMed1995

The p53 gene and its role in human brain tumors.

Mutation of the p53 gene is among the most common lesions in a variety of human tumors, including those of the central nervous system. In most instances, mutation of one p53 allele is followed by loss of the remaining wild-type allele, resulting in cells with a complete absence of functional wild-type p53 protein. However, in some situations, such as at initiation of spontaneously arising gliomas or as the germline configuration of patients with the Li-Fraumeni syndrome, cells clearly carry both wild-type and mutant p53 alleles. These observations lead to the hypothesis that p53 mutations can give rise to loss of tumor suppressor functions as well as to gain of oncogenic transformation capabilities. In this review, we define the types of mutations that occur in the p53 gene in various glial tumors, contrast that with the spectra described in other human tumor types, and discuss the biochemistry and physiology of the p53 protein and its ability to regulate and be regulated by other gene products. We use this information to propose roles for p53 in the initiation and progression of human gliomas.

Amino Acid Sequence↗
PubMed1995

p53 activates expression of HIC-1, a new candidate tumour suppressor gene on 17p13.3.

For several human tumour types, allelic loss data suggest that one or more tumour suppressor genes reside telomeric to the p53 gene at chromosome 17p13.1. In the present study we have used a new strategy, involving molecular analysis of a DNA site hypermethylated in tumour DNA, to identify a candidate gene in this region (17p13.3). Our approach has led to identification of HIC-1 (hypermethylated in cancer), a new zinc-finger transcription factor gene which is ubiquitously expressed in normal tissues, but underexpressed in different tumour cells where it is hypermethylated. Multiple characteristics of this gene, including the presence of a p53 binding site in the 5' flanking region, activation of the gene by expression of a wild-type p53 gene and suppression of G418 selectability of cultured brain, breast and colon cancer cells following insertion of the gene, make HIC-1 gene a strong candidate for a tumour suppressor gene in region 17p13.3.

Amino Acid Sequence↗
PubMed1995

Genetics and malignant progression of human brain tumours.

Progression of gliomas to more malignant phenotypes involves numerous molecular genetic alterations. The genes affected by these alterations, the steps in malignant progression for which they are responsible, their normal function in controlling diverse cellular functions such as differentiation, signal transduction, cell cycle progression and angiogenesis and how they may act in concert with other tumour suppressor genes or oncogenes are some of the questions finally coming into focus and being studied. As other genes are discovered, their association with tumour progression can be assessed, coupled with current histopathology and used to determine more accurately patient prognosis and strategies for intervention. With the generation of specific reagents, such as monoclonal antibodies directed to glioma derived antigens or emerging gene therapy techniques designed to deliver toxic, antisense or reconstituting genes specifically to tumour tissue, new approaches will be devised that may finally be used to treat these tumours effectively.

Animals↗
PubMed1994

p53 gene mutation and mdm2 gene amplification are uncommon in medulloblastoma.

Loss of heterozygosity is common for the short arm of chromosome 17 in medulloblastomas, and putative medulloblastoma suppressor loci have been localized to 17p13. The colocalization of the p53 tumor suppressor gene to 17p13 raises the possibility that its mutant alleles may play a role in the malignant transformation of "medulloblasts." Mutations and deletions of the p53 gene have been described in many tumor types and in the germline of some individuals with the Li-Fraumeni syndrome, but reports on the status of the p53 and mdm2 (a gene coding for a p53-associated protein reportedly amplified in human sarcomas) genes in medulloblastomas are few and an indication of their roles, if any, in the etiology of this important childhood tumor has yet to emerge. Here we have analyzed polymerase chain reaction-amplified products of exons 4-9 (95% of reported p53 mutations occur within this region) of the p53 gene in 9 medulloblastomas for potential mutations using the technique of single strand conformation polymorphism analysis and DNA sequencing. We found only one mutation, an A-T to T-A transversion involving the second base of codon 285 and resulting in the substitution of valine for glutamic acid, amplification of the mdm2 gene could be detected in zero of eight of these tumors. These findings suggest that genetic events associated with the inactivation of p53 gene occur in only a minor subset of medulloblastomas.

Base Sequence↗
PubMed1994

Loss of heterozygosity in sporadic human breast carcinoma: a common region between 11q22 and 11q23.3.

The development of sporadic human breast cancer is associated with the accumulation of genetic alterations on several chromosomes. In the case of chromosome 11, loss of heterozygosity (LOH) at loci on the short arm has been well documented and suggests the presence of a suppressor gene(s) at 11p15.5. However, the evidence for similar events on the long arm is less compelling. Here, we determined the prevalence of LOH for chromosome 11q in 44 malignant and 3 benign cases of unselected sporadic breast tumor samples. We found that alteration of chromosome 11q is common in the pathogenesis of breast cancer as 19 of 44 (43%) malignant tumor specimens exhibited LOH. Eleven (58%) of these genetic alterations were specific to the long arm of the chromosome. The smallest region of shared LOH places the target between 11q22 and 11q23.3, the same general region frequently altered in cancers of the ovary, colon, skin, and uterine cervix, perhaps indicating the location of a tumor suppressor gene or genes of importance in each of these different tumor types.

Breast Neoplasms↗
PubMed1994

A mutant epidermal growth factor receptor common in human glioma confers enhanced tumorigenicity.

The development and neoplastic progression of human astrocytic tumors appears to result through an accumulation of genetic alterations occurring in a relatively defined order. One such alteration is amplification of the epidermal growth factor receptor (EGFR) gene. This episomal amplification occurs in 40-50% of glioblastomas, which also normally express endogenous receptors. Moreover, a significant fraction of amplified genes are rearranged to specifically eliminate a DNA fragment containing exons 2-7 of the gene, resulting in an in-frame deletion of 801 bp of the coding sequence of the extracellular domain. Here we used retroviral transfer of such a mutant receptor (de 2-7 EGFR) into glioblastoma cells expressing normal endogenous receptors to test whether the mutant receptor was able to augment their growth and malignancy. Western blotting analysis showed that these cells expressed endogenous EGFR of 170 kDa as well as the exogenous de 2-7 EGFR of 140-155 kDa. Although holo-EGFRs were phosphorylated on tyrosine residues only after exposure of the cells to ligand, de 2-7 EGFRs were constitutively phosphorylated. In tissue culture neither addition of EGF nor expression of the mutant EGFR affected the rate of cell growth. However, when cells expressing mutant EGFR were implanted into nude mice subcutaneously or intracerebrally, tumorigenic capacity was greatly enhanced. These results suggest that a tumor-specific alteration of the EGFR plays a significant role in tumor progression perhaps by influencing interactions of tumor cells with their microenvironment in ways not easily assayed in vitro.

Animals↗
PubMed1994

Loss of heterozygosity for 10q22-10qter in malignant melanoma progression.

Karyotypic and molecular data indicate that genetic events involving the chromosome region 10q22-10qter may be related to tumorigenesis in malignant melanoma. To test this we analyzed 10 polymorphic microsatellite repeats in the region 10q22-qter, using a polymerase chain reaction-based assay for loss of heterozygosity and DNA isolated from normal and tumor tissue from 26 individuals with malignant melanoma. The samples included 19 paired normal and malignant tissues representing various stages of melanoma as well as 7 cases in which samples from at least 2 different points in time during tumor progression were available. Our findings indicate that loss of heterozygosity of 10q22-10qter is a frequent event, that the observed loss of heterozygosity does not result from whole chromosome loss, and that it is associated with tumor progression. Finally, the appearance of new alleles in two of the tumors may indicate the involvement of DNA replication errors in melanoma analogous to such events in other tumor types.

Alleles↗
PubMed1994

Analysis of the p53 gene and its expression in human glioblastoma cells.

Chromosome 17p has been shown to be an early and frequent target for loss of heterozygosity through mitotic recombination in astrocytomas. These losses are frequently accompanied by point mutations in the p53 gene of the remaining allele, resulting in loss of wild type p53 function. However, a fraction of astrocytomas retain constitutional heterozygosity and do not have p53 mutations; some of these lose wild type p53 activity through binding to the protein product of amplified mdm2 genes. To test whether loss of wild type p53 biological function is a necessary step in astrocytoma progression we analyzed p53 expression and biological function in 13 glioma cell lines. All the cell lines expressed a 2.8-kilobase p53 transcript and showed various amounts of p53 protein by immunoprecipitation, except for cell line LN-Z308 which had only a small truncated p53 mRNA and no protein expression. To test whether the p53 expressed in these cell lines was functionally wild type or mutant we transfected them with a plasmid construct harboring a chloramphenicol acetyltransferase (CAT) reporter gene under the control of transcriptional elements that are induced by wild type but not mutant p53. Four lines were shown to retain wild type p53 function. Sequencing of the p53 gene in two of these cell lines confirmed the wild type genotype. These results show that inactivation of the p53 gene is not an obligatory step in glioblastoma genesis. This suggests either that two pathways (p53 inactivation dependent or independent) may lead to a tumor group classified histologically as glioblastoma or that in some cases p53 mutations are bypassed due to the presence of mutations in downstream effector genes.

Animals↗
PubMed1994

A new highly polymorphic DNA restriction site marker in the 5' region of the human tyrosine hydroxylase gene (TH) detecting loss of heterozygosity in human embryonal rhabdomyosarcoma.

We have isolated a new marker (cos11-5TH) that detects an MspI restriction fragment length polymorphism in the 5' region of the human tyrosine hydroxylase gene (TH) on chromosome band 11p15.5. This region of human chromosome 11 contains several important loci for disease phenotypes including Beckwith-Wiedemann syndrome (BWS), Wilms' tumor, and embryonal rhabdomyosarcoma. Thus, identification of new polymorphic markers in this region are important for future gene mapping and linkage analyses. To better define the region of 11p15.5 deleted in embryonal rhabdomyosarcoma, this new marker was used to investigate allelic losses in embryonal rhabdomyosarcoma tumors.

Base Sequence↗
PubMed1994

Release of an inhibitor of angiogenesis upon induction of wild type p53 expression in glioblastoma cells.

The earliest genetic alteration in human astrocytoma progression is mutation of the p53 tumour suppressor gene, while one of the earliest phenotypic changes is the stimulation of neovascularization. Here, we tested the role of p53 in the angiogenic process by introducing a tetracycline-regulated wild type p53 gene into null glioblastoma cells. The parental cells expressed strong angiogenic activity while upon induction of wild type, but not mutant, p53 expression, the cells secreted a factor able to neutralize the angiogenicity of the factors produced by the parental cells as well as of basic fibroblast growth factor.

Angiogenesis Inhibitors↗
PubMed1993

Mutation and expression of the p53 gene in malignant melanoma cell lines.

Three monoclonal antibodies (MAbs) against p53 protein (PAb 24o, DO-I and PAb1801) were used to define the immunophenotype of 13 melanoma cell lines. Immunoreactions could be detected in 12 out of 13 cell lines by using the indirect immunofluorescence technique. In 7 of these the majority of cells displayed cytoplasmic staining whereas positive nuclei were detected in only a few cells. Two cell lines had predominantly nuclear reactivity, while the remaining 3 cell lines showed signals in both locations. Despite identical nuclear staining patterns, the 3 MAbs produced qualitatively distinct cytoplasmic immunoreactions. PAb240 and DO-1, which showed similar staining frequencies, appeared more sensitive in the detection of p53 protein than did PAb1801. Immunoprecipitations of lysates from each of the cell lines, with MAbs DO-1 and 1801 (which bind to both wild-type and mutant p53 species) detected 53-kDa proteins, whereas PAb240 (which recognizes the mutant conformation of the protein in this type of assay) detected 53-kDa proteins in only 4 cell lines. Nucleotide sequencing of exons 5 to 9 of TP53 in these latter cell lines showed that each has homozygous point mutations in the locus, whereas in the others no TP53 alterations were found. Three of the 4 mutations were C-to-T transversions, alterations possibly caused by damage from UV-light. Our findings indicate that immunostaining with p53 antibodies, although common in malignant melanoma, results from the presence of mutant p53 protein in about 30% of the cases tested. Neither immunostaining with PAb240 nor the patterns of intracellular distributions of the signals are sufficient to detect TP53 mutations.

Antibodies, Monoclonal↗