Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe molecular genetic findings in a patient who initially presented with an intermediate teratoma of the testis and who many years later presented with an oligodendro-astrocytoma. In addition he developed a malignant histiocytoma over the scapula, an adenocarcinoma of the stomach and a late stage adenoma of the sigmoid colon. Due to the development of several neoplasms the possibility of either ataxia telangiectasia or Li-Fraumeni syndrome was considered in differential diagnosis. A molecular genetic investigation revealed that both he and his brother carried a germline p53 tumor suppressor gene mutation at codon 248. From this result we conclude that this family belongs to the Li-Fraumeni syndrome. Once characterized as belonging to the Li-Fraumeni syndrome, the remaining members of the family were typed to determine if they too carried the same mutation. The two children of the index patient were shown not to carry the mutation and are therefore at no increased risk of developing any of the Li-Fraumeni spectrum of malignancies. A molecular genetic investigation into similar families could help to prevent the development of additional malignancies as seen in the index patient, as radiotherapy may interfere with the normal function of the p53 protein and this may in turn help to orchestrate DNA repair after radiation.
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PMID:[Hereditary p53 mutation in a patient with multiple tumors: significance for genetic counseling]. 839 84

A 7-year and 11 month-old girl with cerebellar astrocytoma linked to familial ataxia-telangiectasia (AT) is presented. She was born as the 7th girl of a woman with aortic arch syndrome. Two elder sisters of the patient have ataxia telangiectasia. She had immunodeficiency, and cerebellar ataxia, but had no oculocutaneous telangiectasia. The risk of cancer developing in AT patients is about 1,200 times greater than that in age-matched controls. With regard to central nervous system tumours, seven primary tumours have been reported, such as 3 cases of medulloblastoma and 4 cases of glioma. Members of AT families who were under the age of 45 had a risk of dying of a malignant neoplasm five times greater than in the general population. However, there were no reports of glioma in AT families. In this case, it is suggested that IgA deficiency linked to familial AT may have contributed to the development of astrocytoma.
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PMID:Astrocytoma linked to familial ataxia-telangiectasia. 874 98

In previous studies, we showed that angiotensin II (Ang II) and its congener peptides-angiotensin-(2-8) [Ang-(2-8)] and angiotensin-(1-7) [Ang-(1-7)]-activate 2 distinct signal transduction pathways in a mixed population of human cortical astrocytoma cells. This suggested that different populations of astrocytes could be heterogeneous with respect to their expression of Ang II receptors or the responses to which these receptors are coupled. To compare the responses which are activated by Ang II and its congener peptides in astrocytes from different brain regions, we measured phospholipase C (PLC) activity and prostaglandin release in isolated astrocytes from 4 different areas of neonatal rat brain. In medullary and cerebellar astrocytes, Ang II activated a phosphoinositide-specific PLC in a dose-dependent manner with EC50s of 1.74 and 1.86 nM, respectively. Ang-(2-8) also caused an increase in inositol phosphate release. PLC activity was coupled to an AT1 receptor in both medullary and cerebellar astrocytes, as demonstrated by the inhibition of Ang II-activation of inositol phosphate release by the AT1 antagonist losartan. The AT2 antagonist PD 123319 was ineffective. Ang II and Ang-(2-8) also released prostacyclin from medullary and cerebellar astrocytes, measured as the release of its stable metabolite 6-keto-PGF1 alpha. In contrast, Ang II did not activate PLC or release prostaglandins in astrocytes isolated from the cortex or hypothalamus. In addition, Ang-(1-7) did not stimulate the release of inositol phosphates or prostacyclin in astrocytes from any of the neonatal rat brain regions examined. However, bradykinin (1 microM) activated PLC or released prostacyclin in astrocytes isolated from all 4 brain regions. These results suggest that Ang II receptors on region-specific astrocytes activate distinct signal transduction mechanisms in response to different angiotensin peptides.
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PMID:Angiotensin II activates distinct signal transduction pathways in astrocytes isolated from neonatal rat brain. 909 77

DNA double-strand breaks are thought to precede the formation of most radiation-induced micronuclei. Phosphorylation of the histone H2AX is an early indicator of DNA double-strand breaks. Here we studied the phosphorylation status of the histone H2AX in micronuclei after exposure of cultured cells to ionizing radiation or treatment with colchicine. In human astrocytoma SF268 cells, after exposure to gamma radiation, the proportion of gamma-H2AX-positive to gamma-H2AX-negative micronuclei increases. The majority of the gamma-H2AX-positive micronuclei are centromere-negative. The number of gamma-H2AX-positive micronuclei continues to increase even 24 h postirradiation when most gamma-H2AX foci in the main nucleus have disappeared. In contrast, in normal human fibroblasts (BJ), the proportion of gamma-H2AX-positive to gamma-H2AX-negative micronuclei remains constant, and the majority of the centromere-negative cells are gamma-H2AX-negative. Treatment of both cell lines with colchicine results in mostly centromere-positive, gamma-H2AX-negative micronuclei. Immunostaining revealed co-localization of MDC1 and ATM with gamma-H2AX foci in both main nuclei and micronuclei; however, other repair proteins, such as Rad50, 53BP1 and Rad17, that co-localized with gamma-H2AX foci in the main nuclei were not found in the micronuclei. Combination of the micronucleus assay with gamma-H2AX immunostaining provides new insights into the mechanisms of the formation and fate of micronuclei.
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PMID:Phosphorylation of histone H2AX in radiation-induced micronuclei. 1790 33

Astrocytomas develop intense vascular proliferation, essential for tumour growth and invasiveness. Angiotensin II (ANGII) was initially described as a vasoconstrictor; recent studies have shown its participation in cellular proliferation, vascularisation, and apoptosis. We conducted a prospective study to evaluate the expression of ANGII receptors - AT1 and AT2 - and their relationship with prognosis. We studied 133 tumours from patients with diagnosis of astrocytoma who underwent surgery from 1997 to 2002. AT1 and AT2 were expressed in 52 and 44% of the tumours, respectively, when determined by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Ten per cent of low-grade astrocytomas were positive for AT1, whereas grade III and IV astrocytomas were positive in 67% (P<0.001). AT2 receptors were positive in 17% of low-grade astrocytomas and in 53% of high-grade astrocytomas (P=0.01). AT1-positive tumours showed higher cellular proliferation and vascular density. Patients with AT1-positive tumours had a lower survival rate than those with AT1-negative (P<0.001). No association to survival was found for AT2 in the multivariate analysis. Expression of AT1 and AT2 is associated with high grade of malignancy, increased cellular proliferation, and angiogenesis, and is thus related to poor prognosis. These findings suggest that ANGII receptors might be potential therapeutic targets for high-grade astrocytomas.
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PMID:Expression of AT1 and AT2 angiotensin receptors in astrocytomas is associated with poor prognosis. 1859 40

The purpose of the study was to examine the degree of hTERT, the catalytic subunit of telomerase, expression in paediatric high-grade astrocytoma and to explore the potential of telomerase inhibition as a therapy for these tumours. hTERT was expressed at high levels in 36 of 44 paediatric astrocytomas. Telomerase inhibition induced acute DNA damage and ATM-pathway-dependent G2/M cell cycle arrest in astrocytomas in vitro, both occurring prior to telomere shortening itself. Our data suggest that telomerase inhibition could be a useful adjuvant therapy for high-grade astrocytomas, potentially inducing tumour growth arrest following short-term treatment.
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PMID:Telomerase inhibition induces acute ATM-dependent growth arrest in human astrocytomas. 1894 45

Cyclin D2, P53, Rb and ATM as cell cycle genes regulate cell growth and proliferation. Considering their roles, we assumed that they have different level of mRNA expression in different grades of brain tumors. To determine this point, we investigated the mRNA expression in two types of brain tumors, including astrocytoma and meningioma. The mRNA of 52 brain tumor samples were extracted; cyclin D2, P53, Rb and ATM mRNA expression was quantified using the real-time quantitative reverse-transcription polymerase chain reaction. We compared mRNA expression of these genes between astrocytoma and meningioma tumors and also between different grades of them. Cyclin D2, P53, Rb and ATM had higher expression in astrocytoma than meningioma tumors. Higher grade (III and IV) of astrocytoma tumors had up-regulation for cyclin D2 and ATM genes, but higher grades of these tumors showed down-regulation of P53 and Rb genes. Analysis of relative expression between two grades of meningioma tumors showed a high down-regulation in grade II related to grade I. Also, cyclin D2, P53, Rb and ATM mRNA expression in each group of tumors (meningioma and astrocytoma) showed a highly positive correlation in lower grades. Considering this fact and also different templates of up- and down-regulation for these genes' interaction in different types of brain tumors, it seems that these genes do not have a unique model of interaction.
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PMID:Expression of cyclin D2, P53, Rb and ATM cell cycle genes in brain tumors. 2007 38

Malignant gliomas, the deadliest of brain neoplasms, show rampant genetic instability and resistance to genotoxic therapies, implicating potentially aberrant DNA damage response (DDR) in glioma pathogenesis and treatment failure. Here, we report on gross, aberrant constitutive activation of DNA damage signalling in low- and high-grade human gliomas, and analyze the sources of such endogenous genotoxic stress. Based on analyses of human glioblastoma multiforme (GBM) cell lines, normal astrocytes and clinical specimens from grade II astrocytomas (n=41) and grade IV GBM (n=60), we conclude that the DDR machinery is constitutively activated in gliomas, as documented by phosphorylated histone H2AX (gammaH2AX), activation of the ATM-Chk2-p53 pathway, 53BP1 foci and other markers. Oxidative DNA damage (8-oxoguanine) was high in some GBM cell lines and many GBM tumors, while it was low in normal brain and grade II astrocytomas, despite the degree of DDR activation was higher in grade II tumors. Markers indicative of ongoing DNA replication stress (Chk1 activation, Rad17 phosphorylation, replication protein A foci and single-stranded DNA) were present in GBM cells under high- or low-oxygen culture conditions and in clinical specimens of both low- and high-grade tumors. The observed global checkpoint signaling, in contrast to only focal areas of overabundant p53 (indicative of p53 mutation) in grade II astrocytomas, are consistent with DDR activation being an early event in gliomagenesis, initially limiting cell proliferation (low Ki-67 index) and selecting for mutations of p53 and likely other genes that allow escape (higher Ki-67 index) from the checkpoint and facilitate tumor progression. Overall, these results support the potential role of the DDR machinery as a barrier to gliomagenesis and indicate that replication stress, rather than oxidative stress, fuels the DNA damage signalling in early stages of astrocytoma development.
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PMID:Replication stress and oxidative damage contribute to aberrant constitutive activation of DNA damage signalling in human gliomas. 2058 68

Acrylamide (ACR) has been recognized as a neurological and reproductive toxin in humans and laboratory animals. This study aimed to determine the effects of ACR-induced DNA damage on cell cycle regulation in human astrocytoma cell lines. Treatment of U-1240 MG cells with 2 mM ACR for 48 h resulted in a significant inhibition of cell proliferation as evaluated by Ki-67 protein expression and MTT assay. The analysis of DNA damage with the comet assay showed that treatment of the cells with 0.5, 1, and 2 mM ACR for 48 h caused significant increases in DNA damage by 3.5-, 4-, and 14-fold, respectively. Meanwhile, analysis of cell-cycle arrest with flow cytometry revealed that the ACR treatments resulted in significant increases in the G(0)/G(1)-arrested cells in a time- and dose-dependent manner. Expression of DNA damage-associated/checkpoint-related signaling molecules, including phosphorylated-p53 (pp53), p53, p21, p27, Cdk2, and cyclin D(1), in three human astrocytoma cell lines (U-1240 MG, U-251 MG, and U-87 MG) was also analyzed by immunoblotting. Treatment of the three cell lines with 2 mM ACR for 48 h caused marked increases in pp53 and Cdk2, as well as decreases in cyclin D(1) and p27. Moreover, increases in p53 and p21 were detected in both U-1240 and U-87 MG cells, whereas no marked change in p53 and a decrease in p21 were observed in U-251 MG cells. To address the involvement of ataxia telangiectasia mutated/ATM-Rad3-related (ATM/ATR) kinase in the signaling of ACR-induced G(0)/G(1) arrest, caffeine was used to block the ATM/ATR pathway in U-1240 MG cells. Caffeine significantly attenuated the ACR-induced G(0)/G(1) arrest as well as the expression of DNA damage-associated/checkpoint-related signaling molecules in a dose-dependent manner. This in vitro study clearly demonstrates the critical role of ATM/ATR in the signaling of ACR-induced cell-cycle arrest in astrocytoma cells.
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PMID:Proliferation inhibition, DNA damage, and cell-cycle arrest of human astrocytoma cells after acrylamide exposure. 2073 98

Knowledge on the role of genetic polymorphisms in the etiology of pediatric brain tumors (PBTs) is limited. Therefore, we investigated the association between single nucleotide polymorphisms (SNPs), identified by candidate gene-association studies on adult brain tumors, and PBT risk.The study is based on the largest series of PBT cases to date. Saliva DNA from 245 cases and 489 controls, aged 7-19 years at diagnosis/reference date, was genotyped for 68 SNPs. Data were analyzed using unconditional logistic regression.The results showed EGFRrs730437 and EGFRrs11506105 may decrease susceptibility to PBTs, whereas ERCC1rs3212986 may increase risk of these tumors. Moreover, stratified analyses indicated CHAF1Ars243341, CHAF1Ars2992, and XRCC1rs25487 were associated with a decreased risk of astrocytoma subtype. Furthermore, an increased risk of non-astrocytoma subtype associated with EGFRrs9642393, EME1rs12450550, ATMrs170548, and GLTSCRrs1035938 as well as a decreased risk of this subtype associated with XRCC4rs7721416 and XRCC4rs2662242 were detected.This study indicates SNPs in EGFR, ERCC1, CHAF1A, XRCC1, EME1, ATM, GLTSCR1, and XRCC4 may be associated with the risk of PBTs. Therefore, cell cycle and DNA repair pathways variations associated with susceptibility to adult brain tumors also seem to be associated with PBT risk, suggesting pediatric and adult brain tumors might share similar etiological pathways.
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PMID:Common genetic variations in cell cycle and DNA repair pathways associated with pediatric brain tumor susceptibility. 2761 41


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