Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Loci on chromosome 9p are frequently deleted in several malignant tumors, suggesting the presence of putative tumor suppressor genes. The MTS1/p16 and MTS2/p15 genes on 9p are considered to be candidates. Binding of p15 and p16 cell cycle-regulatory proteins to the cyclin dependent protein kinase CDK4 inhibits CDK4/cyclin D dependent phosphorylation of retinoblastoma protein. We analysed the DNAs from 37 gliomas of several grades of malignancy for allelic loss of chromosome 9p and aberrations of the MTS1/p16 and MTS2/p15 genes. We detected losses of one allele and homozygous deletions at loci, including those of the MTS1/p16 and MTS2/p15 genes, in 10 and 3 tumors, respectively. However, we did not detect any tumor-specific mutation in the two genes. The CDK4 gene was amplified in two malignant gliomas without homozygous deletion of the MTS1/p16 and MTS2/p15 genes and one malignant glioma with an allelic loss of the genes. These data suggest that aberrations of the genes coding for components of the cell cycle-regulatory system occurred in at least 15 of 37 gliomas.
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PMID:Homozygous deletion of the MTS1/p16 and MTS2/p15 genes and amplification of the CDK4 gene in glioma. 747 35

In this study the expression of p16INK4, retinoblastoma protein (pRb), and cdk4 proteins have been examined in 18 malignant glioma cell lines and in 45 malignant glial tumors. Loss of p16INK4 expression associated with p16INK4 gene homozygous deletion was evident in 12 cell lines and in 10 primary tumors. Lack of p16INK4 expression was also evident in five tumors for which there was no evidence of p16INK4 gene homozygous deletion. Two of the cell lines and six of the primary tumors in which p16INK4 was present were determined to overexpress cdk4 in association with CDK4 gene amplification. Absence of pRb was determined in two of the cell lines and in ten of the tumors. In total, 16 of 18 cell lines and 25 of 45 tumors showed either a lack of p16INK4 or pRb or amplification-associated overexpression of cdk4. Two additional tumors showed an absence of pRb and p16INK4, and one tumor showed a lack of pRb combined with amplification-associated overexpression of cdk4. These results suggest a common growth-regulatory mechanism that is disrupted in gliomas by either suppressing the expression of p16INK4 or pRb or by increasing the expression of cdk4.
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PMID:Lack of p16INK4 or retinoblastoma protein (pRb), or amplification-associated overexpression of cdk4 is observed in distinct subsets of malignant glial tumors and cell lines. 758 16

Recently, it has been shown that a gene encoding the cyclin-dependent kinase 4 inhibitory protein, p16, is frequently targeted for homozygous deletions in several types of tumor cell lines, including those established from malignant gliomas. Here we have examined 32 glioma cell lines for amplification-associated overexpression of the CDK4 gene as an alternative mechanism for abrogating the growth-regulatory effects of p16. Two of the cell lines revealed high-level expression of CDK4 in association with gene amplification, and this alteration was observed among the 10 cases having intact p16 genes. Consequently, 24 of 32 glioma cell lines revealed one of two alternative genetic alterations, each of which indicates that increased cdk4 kinase activity is important to glial tumor development.
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PMID:CDK4 amplification is an alternative mechanism to p16 gene homozygous deletion in glioma cell lines. 795 4

p16 is involved in a cell cycle regulatory cascade that includes cyclin-dependent kinase 4 (cdk4), cyclin D1, and pRb (retinoblastoma). Alterations of each of these components have been described in primary human glioblastoma multiforme (GBM) or in GBM cell lines. Because perturbation of any component in this pathway may have similar oncogenic effects, we studied the relationship between abnormalities of CDKN2/p16 and RB, the two commonly involved tumor suppressor genes, in 55 astrocytic gliomas (42 GBMs, 8 anaplastic astrocytomas, and 5 astrocytomas). By using comparative multiplex PCR, homozygous deletions of the CDKN2/p16 gene were detected in 24 GBMs (57%) and in 2 anaplastic astrocytomas. Two additional GBMs and one anaplastic astrocytoma had allelic loss of chromosome 9p, as assessed by microsatellite polymorphisms flanking the CDKN2/p16 region. Single-strand conformation polymorphism and DNA sequencing analysis of all three coding exons of CDKN2/p16 revealed a frameshift mutation (four-bp deletion) in one of the three GBMs that had lost the remaining 9p allele. Allelic loss of chromosome 13q at the RB gene, RB gene mutations, or loss of pRb expression was noted in 14 GBMs (33%) and 2 anaplastic astrocytomas. Thirty-six of 42 GBMs (86%) had alterations of either CDKN2/p16 (n = 22), RB (n = 10), or both (n = 4); these two genetic changes, however, were relatively exclusive (P = 0.003). Furthermore, of the six GBMs without either CDKN2/p16 or RB gene abnormalities, one case had CDK4 gene amplification. These data indicate that the vast majority of GBMs probably have inactivation of the p16-cdk4/cyclin D1-pRb pathway. The findings also provide corroborative evidence that CDKN2/p16 and RB are the critical glioma tumor suppressor genes on chromosomes 9p and 13q, respectively.
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PMID:CDKN2/p16 or RB alterations occur in the majority of glioblastomas and are inversely correlated. 854 55

Gliomas represent the largest group of primary brain tumors in adults. The astrocytic variants are the most common and the adult forms are histologically stratified into three malignancy grades. Of these glioblastoma is the most common and the most malignant; it has also been best studied by molecular genetics and cytogenetics. Double-minute chromosomes, known to represent amplified genes, are found in 50% of glioblastomas. Amplified genes are not detected in the most benign of the astrocytomas. Many genes have been shown to be amplified in more than single cases of gliomas and these include EGFR, CDK4, SAS, MDM2, GLI, PDGFAR, MYC, N MYC, MYCL1, MET, GADD153, and KIT. The most commonly amplified genes in glioblastomas are EGFR (in approximately 40%), CDK4, and SAS (in approximately 15%). The remainder of the genes are amplified at lower frequency. The best mapped amplicon in gliomas involves the 12q13-14 region. The amplicon is of undetermined size, encompasses a number of genes, and may be rearranged. It occurs in 15% of glioblastomas and almost always includes the CDK4 and SAS genes, in about 10% of tumors the MDM2 gene, and at lower frequency GLI, GADD153, and A2MR. All but A2MR are overexpressed if amplified. The amplified EGFR gene is frequently rearranged, resulting in changes in the regions of the transcript that codes for the extracellular domain. The resultant receptor is constitutively activated. These findings provide examples of the impact the use of modern molecular biological techniques has had on our understanding of oncogenic mechanisms in gliomas.
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PMID:Gene amplification in human gliomas. 858 64

Abnormalities in the p16, p15 and CDK4 genes that regulate transition through the G1 phase of the cell cycle have been implicated in the malignant progression of astrocytomas. The results of the present study demonstrate that dysfunction of these genes also occurs during recurrence of glial tumors that were highly malignant at first presentation. Analysis of 10 matched pairs of high grade malignant astrocytomas and their subsequent recurrences identified three distinct groups. The primary and recurrent tumors in Group A did not show structural alterations in the p16, p15 or CDK4 genes, whereas homozygous codeletion of p16 and p15 was observed in both primary and recurrent tumors in Group B. The primary tumors in Group C had a normal profile of p16, p15 and CDK4 at presentation. Upon recurrence, however, the tumors sustained either deletion of p16 alone or codeletion of both p16 and p15 or amplification of CDK4. Analysis of the molecular differences between primary anaplastic astrocytomas/glioblastomas and their subsequent recurrences, which are clinically indistinguishable, may provide better therapeutic options for treatment.
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PMID:Abnormalities of p16, p15 and CDK4 genes in recurrent malignant astrocytomas. 876 Mar 9

Gliomas are tumors of the central nervous system that may be inherited in some patients. The gene(s) responsible for the clustering of gliomas in families have not yet been identified. Molecular studies of sporadic high-grade gliomas have revealed mutations or deletions of the genes encoding the protein kinase inhibitors p16(INK4A) and p15(INK4B) in a large proportion of tumors. Moreover, those tumors without deletions frequently display gene amplification and/or over-expression of mRNA encoding the protein kinase cdk4. We hypothesized that germ-line mutations in the p16(INK4A), p15(INK4B), or CDK4 genes might contribute to some cases of familial gliomas. To address this issue, we analyzed 36 kindreds with a predisposition to glial tumors. Genomic DNA from index members of these families was screened by PCR-single-strand conformational polymorphism analysis. We did not detect any functional mutations in the p16(INK4A), p15(INK4B), or CDK4 genes, although two individuals did have a previously described A140T polymorphism in p16(INK4A). Thus, despite the association between the sporadic forms of high-grade glioma and abnormalities of p16(INK4A), p15(INK4B), or CDK4, we found no evidence that germ-line mutations in the coding region of these three genes predispose to inherited glial tumors.
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PMID:Lack of germ-line mutations of CDK4, p16(INK4A), and p15(INK4B) in families with glioma. 981 74

Malignant glial tumors (anaplastic astrocytomas and glioblastomas multiforme) arise mostly either from the progression of low grade precursor lesions or rapidly in a de novo fashion and contain distinct genetic alterations. There is, however, a third subset of malignant gliomas in which genetic lesions remain to be identified. Following surgical resection, all gliomas appear to have an inherent tendency to recur. Comparative molecular analysis of ten primary malignant gliomas (three anaplastic astrocytomas and seven glioblastomas multiforme) with their recurrences identified two distinct subgroups of recurrent tumors. In one group, primary tumors harbored genetic aberrations frequently associated with linear progression or de novo formation pathways of glial tumorigenesis and maintained their genetic profiles upon recurrence. In the other subset with no detectable known genetic mutations at first presentation, the recurrent tumors sustained specific abnormalities associated with pathways of linear progression or de novo formation. These included loss of genes on chromosomes 17 and 10, mutations in the p53 gene, homozygous deletion of the DMBTA1 and p16 and/ or p15 genes and amplification and/or overexpression of CDK4 and alpha form of the PDGF receptor. Recurrent tumors from both groups also displayed an abnormal expression profile of the metalloproteinase, gel A, and its inhibitor, TIMP-2, consistent with their highly invasive behavior. Delineation of the molecular differences between malignant glioblastomas and their subsequent recurrences may have important implications for the development of rational clinical approaches for this neoplasm that remains refractory to existing therapeutic modalities.
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PMID:Comparative molecular genetic profiles of anaplastic astrocytomas/glioblastomas multiforme and their subsequent recurrences. 1002 21

Malignant gliomas frequently show genetic aberrations of genes coding for cell cycle regulatory proteins involved in the control of G1/S phase transition. These include mutation and/or deletion of the retinoblastoma (RB1) gene, homozygous deletion of the CDKN2A and CDKN2B genes, as well as amplification and overexpression of the CDK4 and CDK6 genes. The D-type cyclins (cyclin D1, D2, and D3) promote cell cycle progression from G1 to S phase by binding to and activating the cyclin dependent kinases Cdk4 and Cdk6. Here, we have investigated a series of 110 primary malignant gliomas and 8 glioma cell lines for amplification and expression of the D-type cyclin genes CCND1 (11q13), CCND2 (12p13), and CCND3 (6p21). We found the CCND1 gene amplified and overexpressed in one anaplastic astrocytoma of our tumor series. Two glioblastomas and one anaplastic astrocytoma showed CCND2 gene amplification, but lacked significant overexpression of CCND2 transcripts. Amplification and overexpression of the CCND3 gene was detected in the glioblastoma cell line CCF-STTG1, as well as in one primary glioblastoma and in the sarcomatous component of one gliosarcoma. Our data thus suggest that amplification and increased expression of CCND1 and CCND3 contribute to the loss of cell cycle control in a small fraction of human malignant gliomas.
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PMID:Amplification and expression of cyclin D genes (CCND1, CCND2 and CCND3) in human malignant gliomas. 1041 84

Chordoid glioma of the third ventricle was recently reported as a novel tumor entity of the central nervous system with characteristic clinical and histopathological features (Brat et al., J Neuropathol Exp Neurol 57: 283-290, 1998). Here, we report on a histopathological, immunohistochemical and molecular genetic analysis of five cases of this rare neoplasm. All tumors were immunohistochemically investigated for the expression of various differentiation antigens, the proliferation marker Ki-67, and a panel of selected proto-oncogene and tumor suppressor gene products. These studies revealed a strong expression of GFAP, vimentin, and CD34. In addition, most tumors contained small fractions of neoplastic cells immunoreactive for epithelial membrane antigen, S-100 protein, or cytokeratins. The percentage of Ki-67 positive cells was generally low (<5%). All tumors showed immunoreactivity for the epidermal growth factor receptor and schwannomin/merlin. There was no nuclear accumulation of the p53, p21 (Waf-1) and Mdm2 proteins. To examine genomic alterations associated with the development of chordoid gliomas, we screened 4 tumors by comparative genomic hybridization (CGH) analysis. No chromosomal imbalances were detected. More focussed molecular genetic analyses revealed neither aberrations of the TP53 and CDKN2A tumor suppressor genes nor amplification of the EGFR, CDK4, and MDM2 proto-oncogenes. Our data strongly support the hypothesis that chordoid glioma of the third ventricle constitutes a novel tumor entity characterized by distinct morphological and immunohistochemical features, as well as a lack of chromosomal and genetic alterations commonly found in other types of gliomas or in meningiomas.
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PMID:Chordoid glioma of the third ventricle: immunohistochemical and molecular genetic characterization of a novel tumor entity. 1051


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