Biomedical subjects

A Waha

Publications and source records attributed to A Waha.

31 records · Page 2Linked to original sources

PubMed1997

Association of EGFR gene amplification and CDKN2 (p16/MTS1) gene deletion in glioblastoma multiforme.

Glioblastoma multiforme (GBM) can be divided into genetic subsets: approximately one-third of GBM, primarily in older adults, have EGFR amplification; another one-third, primarily in younger adults, have TP53 mutation. The majority of GBM also have homozygous deletions of the CDKN2 (p16/MTS1) gene, resulting in cell cycle deregulation and elevated proliferation indices. We evaluated the relationship between CDKN2 deletions and the GBM subsets as defined by EGFR amplification or TP53 mutation in 70 GBM. Twenty-eight cases (40%) had EGFR amplification, 21 (30%) had TP53 mutation, and 21 (30%) had neither change. CDKN2 deletions were present in 36 (51%) GBM. Of the 28 GBM with EGFR amplification, 20 (71%) had CDKN2 deletion (p = 0.0078). The remaining 16 cases with CDKN2 loss were divided between GBM with TP53 mutations (6 cases) and GBM with neither EGFR amplification nor TP53 mutation (10 cases). Thus, CDKN2 deletions occur twice as commonly in GBM with EGFR amplification (71%) than in GBM with TP53 mutation (29%). CDKN2 deletions occurred in GBM from patients somewhat older than those patients with GBM lacking CDKN2 deletion (mean age 53 vs. 48 years). Specifically among GBM with EGFR amplification, those with CDKN2 deletions also occurred in patients slightly older than those few GBM without CDKN2 deletions (mean age 55 vs. 51 years). The presence of CDKN2 deletions in most GBM with EGFR amplification and in generally older patients may provide one explanation for the potentially more aggressive nature of such tumors.

Carrier Proteins↗

PubMed1997

A novel splice site associated polymorphism in the tuberous sclerosis 2 (TSC2) gene may predispose to the development of sporadic gangliogliomas.

The tuberous sclerosis 2 (TSC2) gene is thought to function as a growth suppressor in sporadic and TSC-associated hamartomas and tumors. Clusters of dysplastic glial cells are a common feature of cortical tubers and subependymal nodules in tuberous sclerosis patients. In an effort to identify TSC2 gene alterations in sporadic gliomas, we detected a novel polymorphism adjacent to the 3'splice site of intron 4. We evaluated the distribution of this variant allele in a series of 244 patients with glial tumors, including 55 gangliogliomas, 31 pilocytic astrocytomas (WHO grade I), 50 astrocytomas (WHO grades II and III), and 108 glioblastomas (WHO grade IV). The allelic distribution in the general population was estimated by examining 381 healthy blood donors. This rare allele appeared in the control population and in the patients with astrocytic gliomas with a virtually identical frequency (8.14%, and 8.20%, respectively). The frequency of the rare allele in gangliogliomas, however, was significantly higher (15.5%; p = 0.024). The fact that both gangliogliomas and cortical tubers in tuberous sclerosis contain neuronal and astrocytic elements and may resemble each other histologically suggests that the TSC2 gene may be involved in the development of these tumors. The rare allele of the TSC2 gene emerges as a candidate for a predisposing factor for the formation of sporadic gangliogliomas.

Adult↗

PubMed1997

Molecular genetic analysis of giant cell glioblastomas.

Glioblastomas (GBMs) are a heterogeneous group of tumors. Recently, distinct molecular genetic alterations have been linked to subgroups of patients with GBM. Giant cell (gc)GBMs are a rare variant of GBM characterized by a marked preponderance of multinucleated giant cells. Several reports have associated this entity with a more favorable prognosis than the majority of GBMs. To evaluate whether gcGBM may also represent a genetically defined subgroup of GBM, we analyzed a series of 19 gcGBMs for mutations in the TP53 gene for amplification of the EGFR and CDK4 genes and for homozygous deletions in the CDKN2A (p16/MTS1) gene. Seventeen of nineteen gcGBMs carried TP53 mutations whereas EGFR and CDK4 gene amplification was seen in only one tumor each and homozygous deletion of CDKN2A was not observed at all. The strikingly high incidence of TP53 mutations and the relative absence of other genetic alterations groups gcGBM together with a previously recognized molecular genetic variant of GBM (type 1 GBM). It is tempting to speculate that the better prognosis of gcGBM patients may result from the low incidence of EGFR amplification and CDKN2A deletion, changes known for their growth-promoting potential.

Adult↗

PubMed1997

Quantitative analysis of neurofibromatosis type 2 gene transcripts in meningiomas supports the concept of distinct molecular variants.

Meningiomas frequently show mutational inactivation of the neurofibromatosis type 2 tumor suppressor gene (NF2 gene). In a previous study, mutations were preferentially observed in the fibroblastic and transitional subtypes (75%), whereas the meningothelial variant was significantly less affected (25%). To study a potential role of the NF2 gene on the transcriptional level, we have analyzed NF2 transcripts in 67 meningiomas of different subtypes. A competitive reverse transcriptase-PCR assay with an external NF2 gene standard was used for quantitative mRNA analysis. Fibroblastic and transitional meningiomas exhibited significantly lower levels of NF2 mRNA compared with meningothelial variants (p = 0.001, unpaired t test). These data support the concept of a distinct molecular pathway in the formation of meningothelial meningiomas independent from the NF2 gene or its gene product merlin/schwannomin. In addition, in these tumors, NF2 expression was reduced by a factor of 10 (p < 0.001, unpaired t test) in those meningiomas with NF2 gene mutations suggesting decreased stability or impaired transcription of mutated NF2 mRNA. In conclusion, our data provide further evidence for molecular differences between subtypes of meningiomas and support an NF2-independent pathogenesis of meningothelial meningiomas.

Genes, Neurofibromatosis 2↗

PubMed1996

Association of loss of heterozygosity on chromosome 17p with high platelet-derived growth factor alpha receptor expression in human malignant gliomas.

The aim of this study was to examine platelet-derived growth factor alpha receptor (PDGFR-alpha) expression in gliomas of various degrees of malignancy and to correlate the findings with genetic alterations present in the same tumor samples. We analyzed 83 tumors by in situ hybridization using a PDGFR-alpha cRNA probe. Increased PDGFR-alpha mRNA expression was observed in astrocytic tumors of all stages of malignancy, although the highest levels were found in glioblastoma multiforme. To evaluate the frequency of PDGFR-alpha gene amplification, differential PCR requiring less DNA than Southern analysis was used with fluorescence-labeled primers corresponding to the kinase insert region of the PDGFR-alpha. Only 7 of 43 glioblastomas and none of the other tumors tested showed amplification of the PDGFR-alpha gene, suggesting that a mechanism other than gene amplification is responsible for the overexpression of PDGFR-alpha in glial brain tumors. Comparison of the in situ hybridization data with genetic alterations in the same tumor material showed a significant correlation of loss of heterozygosity on chromosome 17p (Fisher's exact, P < 0.0002) with high expression levels of PDGFR-alpha. Because that was the case in both low- and high-grade astrocytomas, our data imply that PDGFR-alpha is actively involved in tumor cell proliferation in early and late stages of glioma development. The association of PDGFR-alpha expression with a distinct subset of glioblastomas characterized by loss of heterozygosity 17p further supports the differentiation of these tumors into molecular variants.

Base Sequence↗

PubMed1996

Amplification of the cyclin-dependent kinase 4 (CDK4) gene is associated with high cdk4 protein levels in glioblastoma multiforme.

Genetic alterations on the long arm of chromosome 12, including both gene amplification and allelic loss, are associated with malignant progression of human gliomas. The region of the chromosomal arm 12q that is amplified in malignant gliomas contains the CDK4 gene, a cell cycle regulatory gene which promotes cell division. To evaluate the frequency of CDK4 gene amplification, we analyzed a series of 355 brain tumors using a quantitative non-radioactive polymerase chain reaction assay. CDK4 gene amplification occurred in 9 of 81 glioblastomas (11%), but was rare in other neoplasms, including low-grade and anaplastic gliomas, meningiomas, medulloblastomas and metastatic carcinomas (only 6 of 274 cases). There was no correlation between CDK4 gene amplification and allelic loss of chromosome 12. To assess the significance of CDK4 gene amplification, we analyzed protein extracts from 37 glioblastomas by Western blotting with a commercially available polyclonal antibody to cdk4. All tumors with CDK4 gene amplification showed high cdk4 expression levels, whereas no increased cdk4 expression was seen in glioblastomas without CDK4 gene amplification. These data support the functional activity of CDK4 gene amplification in glioblastoma multiforme and point to an important role of CDK4 gene amplification in a subset of glioblastomas.

Brain Neoplasms↗

PubMed1996

Variable imprinting of H19 and IGF2 in fetal cerebellum and medulloblastoma.

Only the maternal or paternal allele of an imprinted gene is expressed in somatic cells. The gene for insulin-like growth factor II (IGF2) and the H19 gene (a putative tumor suppressor gene) are imprinted in humans with monoallelic paternal and maternal expression, respectively. Loss of imprinting (LOI) (i.e., biallelic expression) of IGF2 occurs in some tumors and may promote tumor growth. We examined imprinting of IGF2 and H19 in 6 fetal cerebella, 1 adult cerebellum, 15 medulloblastomas, and 7 medulloblastoma cell lines using polymerase chain reaction (PCR) and reverse transcription-PCR of exonic polymorphisms. Loss of imprinting of IGF2 occurred in 2 out of 3 informative fetal cerebella, 3 out of 7 informative medulloblastomas, and 1 out of 4 informative cell lines. Loss of imprinting of H19 occurred in 0 out of 4 informative fetal cerebella, 0 out of 1 informative adult cerebellum, 4 out of 8 informative medulloblastomas, and 1 out of 4 informative cell lines. The biallelic expression of H19 was only partial in two medulloblastomas, however, with one allele being significantly weaker than the other. Loss of imprinting of IGF2 occurs in medulloblastomas or medulloblastoma cell lines but can also occur in normal fetal cerebellum. Its occurrence in medulloblastomas may therefore reflect the tumors' embryonal nature rather than representing a primary pathogenetic mechanism. Our data also indicate that both genes can be imprinted and expressed independently of each another, both in normal cerebellum and medulloblastomas.

Adult↗

PubMed1996

A polymerase chain reaction-based assay for the rapid detection of gene amplification in human tumors.

A differential polymerase chain reaction (PCR) protocol was established for semiquantitative, nonradioactive detection of gene amplification using a DNA sequencer. Oncogene fragments and control DNA sequences were simultaneously PCR-amplified using fluorescent-labelled primers. Analysis of the PCR products allowed quantitative assessment of gene copy numbers in this coamplification assay. Using this approach, we examined a series of 132 brain tumors for amplification of the epidermal growth factor receptor (EGFR) gene. The same set of tumors was also analyzed by Southern blotting and hybridization with a radiolabelled EGFR probe. Both methods yielded virtually identical results. This technique has a great potential for nonradioactive screening of large tumor panels of oncogene amplification.

Aneuploidy↗

PubMed1996

Lack of prognostic relevance of alterations in the epidermal growth factor receptor-transforming growth factor-alpha pathway in human astrocytic gliomas.

Alterations in the epidermal growth factor receptor (EGFR) and its main ligand, transforming growth factor-alpha (TGF alpha), were investigated for a possible prognostic relevance in 125 astrocytic gliomas (44 World Health Organization (WHO) Grade II, 19 WHO Grade III, and 62 WHO Grade IV tumors). The TGF alpha and EGFR proteins were detected immunohistochemically using monoclonal antibodies. A positive immunoreaction to TGF alpha was detected in 33 (75%) of 44 WHO Grade II astrocytomas, 18 (95%) of 19 WHO Grade III astrocytoma, and 50 (81%) of 62 WHO Grade IV glioblastomas. No correlation between TGF alpha immunoreaction and duration of survival could be found. A positive EGFR immunoreaction was detected in seven (16%) of 44 WHO Grade II astrocytomas, five (26%) of 19 WHO Grade III astrocytomas, and 32 (52%) of 62 WHO Grade IV glioblastomas. Of these gliomas, 97 (26 WHO Grade II, 17 WHO Grade III, and 54 WHO Grade IV gliomas) were examined for EGFR gene amplification using a differential polymerase chain reaction assay. Amplification of the EGFR gene was detected in none of the WHO Grade II astrocytomas, one (6%) of 17 WHO Grade III astrocytomas, and 18 (33%) of 54 WHO Grade IV glioblastomas. Twenty-two of the tumors investigated showed a positive EGFR immunoreaction without detectable gene amplification (five WHO Grade II, four WHO Grade III, and 13 WHO Grade IV tumors). Gene amplification was invariably associated with a positive EGFR immunoreaction. For the entire study group, a strong correlation between EGFR alterations (gene amplification and positive immunoreaction) and survival could be found. However, this correlation only reflected the higher percentages of cases with EGFR alterations in malignant gliomas and was not an independent prognostic factor as determined by multifactorial analysis. These data demonstrate that EGFR alterations are frequent events in astrocytic gliomas and are largely restricted to glioblastomas. However, within one tumor grade they do not provide prognostic information.

Adult↗

PubMed1995

Allelic losses on chromosomes 14, 10, and 1 in atypical and malignant meningiomas: a genetic model of meningioma progression.

To investigate chromosomal events that underlie formation and progression of meningiomas, we have examined a set of 18 benign (WHO grade I), 15 atypical (grade II), and 13 anaplastic/malignant (grade III) meningiomas for loss of heterozygosity (LOH) on chromosomes 1p, 6p, 9q, 10q, and 14q. Frequent loss of loci on these chromosomes was seen in grade II and grade III tumors, specifically, 14q (II and III, 47 and 55%), 1p (40 and 70%), and 10q (27 and 40%). In contrast, LOH for these loci was infrequent in benign meningiomas, specifically, 14q (0%), 1p (11%), and 10q (12%). The smallest common regions of deletion that could be defined were 14q24-q32, 1p32-pter, and 10q24-qter. These observations indicate the likely presence of tumor suppressor genes in these regions that are involved in the development of WHO grade II and grade III meningiomas. Because LOH for loci on chromosomes 1p and 10q was found in tumors of all grades and because the frequency of LOH in all three regions increased with tumor grade, these results would support a model for the formation of aggressive meningiomas through tumor progression.

Adult↗

PubMed1994

Loss of maternal alleles on chromosome arm 11p in hepatoblastoma.

Hepatoblastoma is the most common primary malignant liver tumor in children, yet little is known about molecular genetic changes in these tumors. Previous studies report loss of heterozygosity on chromosome arm 11p in some hepatoblastomas. We used the polymerase chain reaction to amplify multiple microsatellites on chromosome arm 11p to assess loss of heterozygosity in 18 hepatoblastomas. Loss of heterozygosity on 11p was found in six of them. The common region of overlap was restricted to the telomeric portion of 11p (11p15.5) and therefore excluded the WT-1 tumor suppressor gene at 11p13. Parental origin of the lost allele could be determined in all six cases and was exclusively maternal. These results indicate that a tumor suppressor gene at 11p15.5 is involved in the pathogenesis of hepatoblastoma and also suggest that this chromosomal region is imprinted.

Child, Preschool↗

PubMed1994

Loci associated with malignant progression in astrocytomas: a candidate on chromosome 19q.

WHO grades II and III astrocytomas frequently exhibit loss of genetic material on chromosomes 9p, 11p, 17p, 19q, and 22q, indicating that these chromosomal regions harbor tumor suppressor genes involved in the pathogenesis of astrocytic neoplasms. The present study was conducted to examine whether these genetic regions are involved in the process of malignant progression from astrocytoma WHO grade II (A II) to anaplastic astrocytoma WHO grade III (A III). We have analyzed 44 astrocytomas, i.e., 18 A II and 26 A III for loss of heterozygosity (LOH) on chromosomes 1p, 1q, 9p, 9q, 10p, 10q, 11p, 13q, 17p, 19p, 19q, and 22q and for amplification of the epidermal growth factor receptor gene. A polymerase chain reaction-based assay with microsatellite repeat sequences was used for the detection of polymorphisms on silver-stained polyacrylamide gels. LOH on 9p was seen in 1 of 18 (6%) informative cases of A II and 4 of 24 (17%) informative cases of A III. LOH on 17p was observed in 9 of 17 (53%) informative cases of A II and 15 of 26 (58%) informative cases of A III. LOH on 19q was detected in 2 of 18 (11%) informative cases of A II and in 12 of 26 (46%) informative cases of A III. The association of LOH on 19q with anaplasia in astrocytoma was significant (P = 0.015). Amplification of the epidermal growth factor receptor gene was not detected in A II or A III. These data suggest that a putative tumor suppressor gene on the long arm of chromosome 19 is a candidate for a gene associated with tumor progression in astrocytic gliomas.

Adult↗

PubMedDate not supplied

The epidermal growth factor receptor in glioblastoma: genomic amplification, protein expression, and patient survival data in a therapeutic trial.

Human glioblastomas were evaluated for overexpression of the epidermal growth factor receptor (EGFR) in a therapeutic trial with the anti-EGFR antibody EMD 55900. A total of 55 cases were examined by immunohistochemistry using 4 different monoclonal antibodies on frozen or on paraffin sections: EGFR-1 (Amersham), E 62 (Merck), E 30 (Merck), and EMD 55900 (MAB 425, Merck). Definition for inclusion in clinical trials of EMD 55900 was an immunohistochemical overexpression of grade 4+ or 3+ in a scale of 4 grades of staining quality. The use of the 4 different antibodies gave essentially equal results. In 21 cases, the immunohistochemical results were supplemented by molecular genetic analysis of EGFR amplification on the corresponding locus of chromosome 7, using frozen tissue from the same blocks after screening for vital tumor areas. Since no other material was available, the differential polymerase chain reaction technique was applied. Interferon-gamma (IFN-gamma) served as a reference gene. In a preliminary experimental series with cases of known EGFR amplification, a densitometric EGFR/IFN-gamma ratio higher than 3 was determined as indicator for amplification of the EGFR gene. With this experimental approach we were able to identify an amplified EGFR gene in 13 specimens including 2 from recurrent glioblastomas in the same patients. All of these showed an increased immunoreactivity for EGFR protein. The degree of EGFR amplification (EGFR/IFN-gamma ratio as measured by DNA densitometry) showed a positive correlation with the grade of immunohistochemical protein expression, both in regard to the fraction of positive cells and to the overall staining intensity.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗