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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ataxia telangiectasia (AT) is a hereditary disease transmitted in a recessive mode and characterized by chromosomal instability and radiosensitivity. AT patients have a 100-fold higher risk of cancer than the general population. Although AT is a rare disease of which the frequency has been estimated to be 1/40,000, the frequency of the heterozygosity status, when assessed with the Hardy-Weinberg equation is high (about 1.4%). Parents of AT children, thus obligate AT carriers, show chromosomal instability and radiosensitivity, but at a lower level than AT patients. Assuming that these AT characteristics deal with the cancer predisposition, it can be hypothesized that AT heterozygote individuals have a higher cancer susceptibility than the general population. To test this hypothesis, M Swift's group compared cancer incidence rates from adult blood relatives of AT patients with controls. The risk of cancer in AT heterozygotes could be increased by 3.5 and, for carrier women, the breast cancer risk could be increased by 5.1. Actually, the diagnosis of the AT heterozygote status is not possible. However, the near cloning of the gene (or genes) for the disease will permit to identify the AT carriers in a population of patients suffering from cancer and to assess precisely the impact of AT heterozygosity in the genetic predisposition to cancer.
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PMID:[Ataxia telangiectasia: what impact in clinical oncology?]. 146 90

Ataxia-telangiectasia (A-T) is a syndrome that has an extremely high incidence of cancer. Patients with the disease are homozygous for a mutant gene, the A-T gene, located at 11q23. Of these individuals, 30-40% develop cancer. Of these cancers, 80% are lymphoid. Those heterozygous for the A-T gene also have an increased frequency of cancer, the most notable being the 6.8-fold increase of breast cancer in females carriers. The syndrome is characterized cytogenetically by increased nonrandom chromosome breaks and rearrangements in lymphocytes involving the sites of the immunoglobulin and T-cell receptor genes. Clones of cells having the same rearrangements are often present in the blood of the A-T patients and if the rearrangements involve certain sites, especially a locus within 14q32, the propensity to progress to a malignant transformation is great. Sequencing the A-T gene and ascertaining its function should contribute significantly to our understanding of the molecular mechanisms underlying cancer susceptibility.
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PMID:Cancer susceptibility in ataxia-telangiectasia. 154 42

Ataxia-telangiectasia (AT) is an autosomal recessive disorder resulting from a single defective gene in each family. Complementation studies suggest that the same syndrome is associated with defects of at least four AT genes (ATA, ATC, ATD and ATE). The syndrome is multifaceted and involves the cerebellum, skin, immunological system, chromosomes, cancer susceptibility, radiosensitivity, premature ageing and serum alphafetoprotein levels. In order to further develop understanding of how these seemingly unrelated physiological systems interact in this disease, we attempted to localize the gene by linkage analysis, using a single large Group A AT family to screen 171 genetic markers and 30 additional AT families to confirm any positive linkages. We found a linkage to AT (Group A) with genetic markers on chromosome 11q22-23. This region of the human genome is syntenic with a large region of the mouse genome on chromosome 9 and includes such "candidate" genes as THY1, NCAM, CD3G-D-3, ets-1, and APOA1-C3-A4. In addition, studies of human chromosomes identify fragile sites in this region as well as breakpoints associated with translocation 4: 11 and 9; 11 in acute non- lymphocytic leukemias. The pathogenetic implications of this localization to 11q22-23 are considered.
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PMID:Ataxia-telangiectasia (group A): localization of ATA gene to chromosome 11q22-23 and pathogenetic implications. 168 42

Ataxia-telangiectasia (AT) is a heterogeneous autosomal recessive disorder marked by cerebellar ataxia, oculocutaneous telangiectases, hypersensitivity to ionizing radiation, immunodeficiency, and cancer susceptibility. AT is also a spontaneous chromosomal breakage syndrome, notable for tissue-specific cytogenetic changes and telomeric fusions. Molecular characterization of rearrangements specific to T-lymphocytes suggests that a DNA repair/processing defect is potentially responsible for the diverse array of chromosomal abnormalities observed in a variety of AT cell types.
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PMID:The cytogenetics of ataxia telangiectasia. 175 58

Ataxia-telangiectasia is a syndrome with many facets, involving a progressive cerebellar ataxia, immunodeficiency, cancer susceptibility, radiosensitivity, defects in DNA repair/processing, chromosomal breakage and rearrangements, elevated serum alphafetoprotein, and premature aging. Ataxia-telangiectasia is an autosomal recessive disorder, rare in outbred populations; carriers of the ataxia-telangiectasia gene may be as common as 1 in 60 and have subclinical radiosensitivity and cancer susceptibility. One estimate suggests that 8.8% of patients with breast cancer could be carriers of ataxia-telangiectasia. These carriers may be responsible for underestimating normal tolerance doses for radiation therapy by 15% to 20%; thus by preselecting and excluding carriers of ataxia-telangiectasia from cohorts of patients with cancer, conventional radiation doses might be increased so as to improve greatly the efficacy of radiotherapy. The genes for the 3 most common ataxia-telangiectasia complementation groups, which include 97% of tested families, have recently been localized to the long arm of chromosome 11.
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PMID:Ataxia-telangiectasia: an interdisciplinary approach to pathogenesis. 200 80

Supplementation with 1 g of vitamin C (ascorbic acid) per day decreased the amount of chromosome damage induced in lymphocytes by an exposure to bleomycin during the last 5 h of cell culture. We did not see such changes in lymphocytes from control individuals samples at the same time but not taking vitamin C supplements. This bleomycin assay has been proposed as a test for cancer susceptibility. A similar assay for genetic instability may be useful in detecting heterozygotes for chromosome-breakage syndromes (for example, Fanconi anemia or ataxia telangiectasia). Even though our sample size is small and our results should be interpreted cautiously, statistically significant effects were found with vitamin C supplementation. It would, therefore, be prudent to consider dietary and perhaps other lifestyle factors when interpreting of results from this bleomycin assay and related assays for genetic instability.
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PMID:Vitamin C intake influences the bleomycin-induced chromosome damage assay: implications for detection of cancer susceptibility and chromosome breakage syndromes. 247 99

In the present study, both post-irradiation DNA synthesis and G2 phase accumulation were analyzed in lymphoblastoid cell lines (LCLs) and fibroblast cell strains derived from (Saudi) patients with non-Hodgkin's lymphoma (NHL), ataxia telangiectasia (AT), AT heterozygotes and normal subjects. A comparison of the percent DNA synthesis inhibition (assayed by 3H-thymidine uptake 30 min after irradiation), and a 24 h post-irradiation G2 phase accumulation determined by flow cytometry placed the AT heterozygotes and the NHL patients in an intermediate position between the normal subjects (with maximum DNA synthesis inhibition and minimum G2 phase accumulation) and the AT homozygotes (with minimum DNA synthesis inhibition and maximum G2 accumulation). The similarity between AT heterozygotes and the NHL patients with respect to the two parameters studied after irradiation was statistically significant. The data indicating a moderate abnormality in the control of cell cycle progression after irradiation in the LCLs and fibroblasts from NHL patients may explain the enhanced cellular and chromosomal radiosensitivity in these patients reported by us earlier. In addition to demonstrating a link between cell cycle abnormality and radiosensitivity as a possible basis for cancer susceptibility, particularly in the NHL patients, the present studies emphasized the usefulness of the assay for 24 h post-irradiation G2 phase accumulation developed by Lavin et al. (1992) in characterizing AT heterozygote-like cell cycle anomaly in cancer patients irrespective of whether they carried the AT gene or any other affecting the cell cycle.
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PMID:Post-irradiation DNA synthesis inhibition and G2 phase delay in radiosensitive body cells from non-Hodgkin's lymphoma patients: an indication of cell cycle defects. 752 92

We examined five males with laboratory-confirmed ataxia-telangiectasia (AT), aged 9-28 years, several times by MRI (9 examinations: 5 at 0.15 T, 3 at 0.5 T, 1 at 1.5 T). Intermediate, T1-, T2- and T2*-weighted spin-echo and gradient-echo sequences were performed. All patients showed vermian atrophy, enlarged fourth ventricle and cisterna magna; four showed cerebellar hemisphere atrophy; two enlarged infracerebellar subarachnoid spaces and four patients had sinusitis. No focal areas of abnormal signal were seen in the brain, diffuse high signal was found in the central cerebral white matter of the oldest patient. AT is an important human model of inherited cancer susceptibility and multisystem ageing; as in xeroderma pigmentosum and other "breakage syndromes", ionising radiation should be avoided. When imaging is necessary, MRI should be preferred to CT in patients known or suspected to have AT and those with undefined paediatric ataxias of nontraumatic origin. If atrophy of only the cerebellum, especially the vermis, is noted, laboratory research should be performed to confirm the diagnosis of AT.
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PMID:Cranial MRI in ataxia-telangiectasia. 770 96

We used a modified colony survival assay to measure the sensitivity to ionizing radiation of more than 50 lymphoblastoid cell lines from normal individuals and from patients with ataxia-telangiectasia, Nijmegen breakage syndrome variants, and X-linked agammaglobulinemia. All of these disorders are associated with an increased frequency of cancer. Lymphoblastoid cell lines from patients with ataxia-telangiectasia complementation groups A, C, D, and E; ATFresno; Nijmegen breakage syndrome variants V1 and V2; and X-linked agammaglobulinemia showed marked radiosensitivity, whereas ataxia-telangiectasia heterozygotes were similar to controls. Friedreich's ataxia is not associated with increased cancer risk; lymphoblastoid cell lines from two such patients showed normal radiosensitivity. Taken together, these results suggest that some forms of X-ray sensitivity and cancer susceptibility share a common mechanism, such as an enzyme that is necessary both for the repair of radiation damage to DNA and for gene rearrangements during V(D)J recombination.
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PMID:Radiosensitivity of ataxia-telangiectasia, X-linked agammaglobulinemia, and related syndromes using a modified colony survival assay. 816 76

Alterations of the TP53 tumor suppressor gene are present in various human malignancies and in the dominantly inherited Li-Fraumeni syndrome. Recently, a cell cycle checkpoint pathway involving p53 and GADD45 has been identified as defective in ataxia-telangiectasia. Using single strand conformation polymorphism analysis of PCR products, we looked for TP53 mutations in DNA of patients with AT. We did not find any mutation in 6 patients, suggesting that TP53 mutations are not directly involved in the cancer susceptibility observed in AT.
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PMID:Lack of mutations in the P53 gene exons 5 to 8 in ataxia-telangiectasia. 850 Jan 1


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