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B R Seizinger

Publications and source records attributed to B R Seizinger.

At least 37 records · Page 2Linked to original sources
PubMed1993

Lack of allelic deletion and point mutation as mechanisms of p53 activation in human malignant melanoma.

To investigate the role of the p53 tumor-suppressor gene in the development of human melanoma, loss of heterozygosity (LOH) of p53 was studied in 46 cases of melanoma by a polymerase-chain-reaction/restriction-fragment-length polymorphism (PCR/RFLP) analysis, and p53 mutations were assessed in 51 cases of melanoma by a polymerase-chain-reaction/single-strand-conformation polymorphism (PCR/SSCP) analysis. Frozen tumors and paraffin samples were used in the study. We were not able to detect any allelic loss in 12BstUI informative cases or any single mutation in exons 5 to 8 of the p53 gene. Our results, together with other findings at the DNA level, suggest that the p53 gene appears not to be commonly involved in the development of melanoma, at least by its most frequent mechanisms of deletion of one allele and/or mutation in the other.

Base Sequence↗
PubMed1993

Clinical and genetic studies of renal cell carcinomas in a family with a constitutional chromosome 3;8 translocation. Genetics of familial renal carcinoma.

OBJECTIVE: To describe the clinical course and genetic studies of renal carcinoma in members of a family with the constitutional chromosome translocation, t(3;8) (p14;q24). DESIGN: A follow-up study that updates our 1979 report of renal carcinoma in 10 of these relatives. SETTING: A cancer center and university hospital. PATIENTS: Members of the family, including five carriers of the 3;8 translocation who were in remission of renal cancer. MEASUREMENTS: Clinical follow-up of the family and genetic analyses of the renal cancer specimens of three patients. RESULTS: Renal carcinoma recurred in all five patients in the family at 1 to 16 years of follow-up. Three patients have died of renal cancer, and two are in a second remission. The renal cancers from three family members consistently reveal loss of the entire derivative chromosome 8, which bears the chromosome 3p segment spanning band p14 to the telomere. In contrast, no genetic change was detected in the derivative chromosome 3 or in normal chromosomes 3 and 8. CONCLUSIONS: This family illustrates the importance of clinical follow-up of patients with a hereditary cancer that can develop at multiple foci and recur over time. The inherited 3;8 translocation and loss of the translocated distal chromosome 3p in tumor specimens of family members may help localize the gene or genes involved in the pathogenesis of both familial and sporadic renal carcinoma.

Adult↗
PubMed1993

Deletions on the long arm of chromosome 17 in pilocytic astrocytoma.

Pilocytic astrocytomas are the most common astrocytic tumors of childhood and differ clinically and histopathologically from those astrocytomas that affect adults. Studies of adult astrocytic tumors have revealed allelic losses on chromosomes 10, 17p, 19q and alterations in the epidermal growth factor receptor (EGFR) gene. We have previously examined pilocytic astrocytomas for allelic losses on chromosomes 10 and 19q and for amplification of the EGFR gene, but did not detect genomic alterations at these loci. In the present study we assayed 20 pilocytic astrocytomas for loss of allelic heterozygosity of chromosome 17p, including one locus in the p53 tumor suppressor gene. In addition, because pilocytic astrocytomas frequently affect patients with neurofibromatosis type 1 (NF1) and the NF1 gene has been mapped to 17q11.2, we also examined multiple loci on the long arm of chromosome 17. Allelic loss was observed on chromosome 17 in four cases (three sporadic, one NF1); all lost portions of the long arm in chromosome 17, and one tumor lost the short arm as well. One tumor showed an interstitial deletion on the long arm that included the region of the NF1 gene. These data suggest the presence of a tumor suppressor gene on 17q that is associated with pilocytic astrocytomas. A potential candidate for this gene is the NF1 tumor suppressor gene.

Adolescent↗
PubMed1993

Comparative study of p53 gene and protein alterations in human astrocytic tumors.

The p53 gene is a tumor suppressor gene involved in many common malignancies, including astrocytomas. Genetic analysis of the p53 gene and immunohistochemistry of the p53 protein have each been used to screen astrocytomas. To compare these methods, we performed immunohistochemistry with the monoclonal antibody PAb 1801 and single-strand conformational polymorphism (SSCP) with sequence analysis on 34 astrocytic tumors (WHO grades II, III and IV). Seven cases had detectable p53 protein and gene mutations, while twelve cases had neither detectable protein nor gene mutations. Four tumors had frameshift mutations in the p53 gene that were not revealed by immunohistochemistry. One tumor had a genetic polymorphism and no detectable p53 protein. Ten tumors had p53 protein accumulation but no mutations by SSCP; these cases may represent p53 mutations outside of the conserved exons or elevated levels of wild-type p53 protein. Thus, some p53 mutations are missed with PAb 1801 immunohistochemistry alone. p53 immunohistochemistry, however, may reveal p53 accumulation independent of mutations in the conserved portions of the gene. Finally, we suggest that glioblastomas with p53 mutations in the conserved region of the gene may be a subset that are more common in women and in younger patients.

Adolescent↗
PubMed1993

Subsets of glioblastoma multiforme defined by molecular genetic analysis.

Glioblastoma multiforme is a clinically and histologically heterogeneous lesion; however, to date, it has not been possible to subdivide glioblastomas on a clinical, histopathological or biological basis. Previous studies have demonstrated that loss of portions of chromosomes 10 and 17 and amplification of the epidermal growth factor receptor (EGFR) gene are the most frequent genetic alterations in glioblastoma. We therefore examined 74 glioblastomas from 67 patients for loss of heterozygosity on chromosomes 10 and 17, and for amplification of the epidermal growth factor receptor gene, to determine whether glioblastomas can be subtyped on a genetic basis. Using Southern blot analysis we were able to detect different patterns of genomic alterations. Eighteen of 67 informative patients were characterized by a loss of heterozygosity on the short arm of chromosome 17 in the tumor tissue. Forty-five of 64 informative patients showed a loss of heterozygosity on chromosome 10. Amplification of the epidermal growth factor receptor gene was noted in 25 of 67 patients and was restricted to those glioblastomas that had lost portions of chromosome 10. Epidermal growth factor receptor gene amplification occurred significantly more often in patients without chromosome 17p loss than in patients with chromosome 17p loss (p = 0.01). In addition, those glioblastomas with a loss of chromosome 17p occurred in patients significantly younger than those with glioblastomas characterized by EGFR gene amplification (p = 0.001). These data emphasize the genetic heterogeneity of glioblastoma and suggest the division of glioblastoma into genetic subsets.

Adolescent↗
PubMed1992

Cytogenetic and molecular studies of a familial renal cell carcinoma.

In a previously studied family with inherited renal cell carcinoma (RCC), RCC was shown to segregate with a constitutional balanced t(3;8)(p14.2;q24.1). In addition, we recently showed that in a RCC tumor from this family the constitutional translocation became unbalanced, suggesting a genetic mechanism that may be associated with the primary genetic events of tumorigenesis. We now report that the RCC tumor cells from this case showed additional cytogenetic alterations, possibly related to tumor progression, which include an additional tumor-specific translocation involving band 14 of chromosome 13. Because this band contains the retinoblastoma (RB) gene, we examined the tumor for aberrations in the RB gene using DNA sequence polymorphism analysis and pulsed-field gel electrophoresis (PFGE), but did not detect alterations in the RB gene.

Adult↗
PubMed1992

Anti-oncogenes and the development of tumors in the human nervous system.

Two distinct mechanisms of tumorigenesis have been identified in humans. One mechanism is associated with the activation of growth-promoting factors such as proto-oncogenes, growth factors, and growth factor receptors. However, there is overwhelming evidence for the existence of an alternative tumor mechanism that is related to the loss or inactivation of genes that normally suppress cell growth. These genes have been called "anti-oncogenes" or "tumor-suppressor" genes. They appear to be involved fundamentally in the development of many human cancers. This article reviews the potential importance of tumor-suppressor genes in tumor development and growth control in the human nervous system.

Gene Expression Regulation↗
PubMed1992

Repression of the basal c-fos promoter by wild-type p53.

Mutations in the p53 gene are the most common genetic alterations observed in many inherited and sporadic forms of human cancer. Recent studies indicate that wild-type p53 may be involved in the regulation of gene expression. In the present report we examined the effect of p53 on the human c-fos promoter. Using a transient co-transfection assay we show that wild-type human p53, but not a transforming mutant of p53, negatively regulates the activity of the c-fos promoter in a dose-dependent manner. Promoter deletion analysis maps a sequence conferring p53 repression to the basal promoter region between nucleotides -53 and +42 relative to the cap site. In contrast, p53 strongly stimulates transcription when a sequence previously reported to bind p53 (TGCCT repeat) was inserted in front of the HSV-TK promoter driving CAT. These findings raise the question as to whether p53 may mediate its inhibitory effect on c-fos gene expression by interfering, directly or indirectly, with components of the basal transcriptional machinery.

Base Sequence↗
PubMed1992

Evidence for a tumor suppressor gene on chromosome 19q associated with human astrocytomas, oligodendrogliomas, and mixed gliomas.

Previous studies have shown frequent allelic losses of chromosomes 9p, 10, 17p, and 22q in glial tumors. Other researchers have briefly reported that glial tumors may also show allelic losses of chromosome 19, suggesting a putative tumor suppressor gene locus on this chromosome (D. T. Ransom et al., Proc. Am. Assoc. Cancer Res., 32:302, 1991). To evaluate whether loss of chromosome 19 alleles is common in glial tumors of different types and grades, we performed Southern blot restriction fragment length polymorphism analysis for multiple chromosome 19 loci in 122 gliomas from 116 patients. Twenty-nine tumors had loss of constitutional heterozygosity of 19q, and four tumors had partial deletions of 19q. Allelic losses on 19q were restricted to grade III anaplastic astrocytomas (4/9) and grade IV glioblastomas (11/46), grade II oligodendrogliomas (2/5) and grade III anaplastic oligodendrogliomas (2/2), and grade II (5/8) and grade III (5/7) mixed oligoastrocytomas. These data demonstrate genetic similarities between astrocytomas, oligodendrogliomas, and mixed glial tumors and indicate the presence of a glial tumor suppressor gene on chromosome 19q.

Astrocytoma↗
PubMed1992

p53 mutations are associated with 17p allelic loss in grade II and grade III astrocytoma.

Loss of genetic material on the short arm of chromosome 17 is observed in approximately 40% of human astrocytomas (WHO grades II and III) and in approximately 30% of cases of glioblastoma multiforme (WHO grade IV). Previous studies of glioblastoma multiforme have shown that the p53 gene, located on the short arm of chromosome 17, is frequently mutated in these glioblastomas. To explore whether lower-grade astrocytomas are also associated with corresponding mutations of the p53 gene, we have investigated a series of 22 human astrocytomas of WHO grades II and III both for loss of heterozygosity on chromosome 17p and for p53 mutations. Mutations in the conserved regions of the p53 gene were identified by single strand conformation polymorphism analysis of exons 5, 6, 7, and 8 and were verified by direct DNA sequencing of the polymerase chain reaction products. p53 mutations were observed in 3 of 8 grade II astrocytomas and 4 of 14 grade II astrocytomas. In all 22 tumors, allelic loss of the short arm of chromosome 17 was investigated by restriction fragment length polymorphism analysis. One-half of the grade II astrocytomas (4 of 8) and grade III astrocytomas (7 of 14) exhibited allelic loss on chromosome 17p. Mutations in the p53 gene were exclusively observed in tumors with allelic loss on 17p. Our results show that p53 mutations are not restricted to glioblastoma multiforme and may be important in the tumorigenesis of lower-grade astrocytomas and that p53 mutations in lower-grade astrocytomas are associated with loss of chromosome 17p. These findings are consistent with a recessive mechanism of action of p53 in WHO grade II and III astrocytoma tumorigenesis.

Alleles↗
PubMed1992

Desmoplastic cerebral astrocytomas of infancy: a histopathologic, immunohistochemical, ultrastructural, and molecular genetic study.

The desmoplastic cerebral astrocytoma of infancy (DCAI) is a rare tumor that presents as a large hemispheric mass in infants. Despite an ominous histologic picture that may resemble a sarcoma, the tumor is astrocytic and has a good prognosis. We present two cases of DCAI, with histopathologic, immunohistochemical, ultrastructural, and molecular genetic data, and draw the following conclusions: (1) the diagnosis of DCAI requires a high index of suspicion and immunohistochemical or ultrastructural proof of astrocytic differentiation; (2) the data argue against nosologically equating these tumors with the desmoplastic infantile ganglioglioma, pleomorphic xanthoastrocytoma, or gliofibroma; (3) the components of the extensive tumor basal lamina may be elaborated by the tumor cells themselves and may contribute in an autocrine fashion to the slow growth of these lesions; and (4) if the lack of allelic loss on chromosomes 17p (including the p53 tumor suppressor gene locus) and 10 seen in our cases is found in other cases of DCAI, this may further distinguish the DCAI from other astrocytomas.

Alleles↗
PubMed1992

A (CA)n dinucleotide repeat assay for evaluating loss of allelic heterozygosity in small and archival human brain tumor specimens.

Southern blotting is a widely used method of determining loss of chromosomal alleles in tumors, but cannot be used to analyze small biopsies and most fixed, embedded tissues. These problems preclude analysis of many surgical neuropathology specimens. We have employed a polymerase chain reaction assay for loss of heterozygosity (LOH) based on the (CA)n dinucleotide repeat polymorphisms found in abundance throughout the human genome. We compared this method to conventional Southern blotting in detecting LOH on chromosome 10 in gliomas. From tissue sections of 14 paraffin-embedded, formalin-fixed gliomas, we amplified the (CA)n repeat D10S89 locus and compared (CA)n repeat patterns between tumor DNA and constitutional DNA. Loss of one chromosome 10 (CA)n repeat allele was seen in informative glioblastomas that showed allelic loss by Southern blotting, but not in gliomas that had maintained both alleles. The (CA)n repeat method can be applied to small and fixed, embedded specimens, is rapid and simple to perform, and uses highly polymorphic probes. We suggest that (CA)n repeats are a less exclusive and more rapid means of studying LOH in brain tumors than Southern blotting, and will provide further mapping data for the identification of tumor suppressor genes integral to glial tumorigenesis.

Adenine↗