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

The molecular basis of sensitivity to therapeutic radiation and chemotherapy is a complex product of cellular and tissue responses. Certain genetic factors can be highlighted as being of special importance in the response of breast cancers to treatment. The breast cancer susceptibility genes, BRCA1 and BRCA2, determine the phenotype of the tumor, with BRCA1- or BRCA2-deficient tumors showing marked sensitivity to ionizing radiation and drugs that produce double-strand breaks. However, the extent to which loss of BRCA1 or BRCA2 function occurs in sporadic cancer has not yet been determined. The ATM protein plays a significant role in determining the response to therapy, but how frequently the function of ATM is disrupted in breast cancer is debated. Although the p53 protein is a major determinant of the response to ionizing radiation and cytotoxic drugs, there is no consistency in how p53 affects the survival of cells, because an impairment of DNA repair is offset by reduced apoptosis. Growth factors that sustain the proliferation of breast cancer cells may impact the response to therapy by inhibiting apoptosis. Loss of cell-cycle checkpoint responses may result in increased sensitivity, particularly if the checkpoint controls the G2 transition. Overexpression of cyclin D, which shortens the duration of the G1 transition, is associated with mild radiation resistance, perhaps by inhibiting apoptosis. Overall, there is much more to be understood in the complex response of breast cancers to therapy, and many other proteins play important roles in the response to treatment. The focus of our investigation is on those genetic alterations in tumors that affect the response to therapy, which will ultimately allow strategies to achieve therapeutic gain.
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PMID:The molecular basis of radiosensitivity and chemosensitivity in the treatment of breast cancer. 1238 88

Fanconi anemia (FA) is an autosomal recessive disorder characterized by cellular hypersensitivity to DNA cross-linking agents and cancer predisposition. Recent evidence for the interactions of ataxia-telangiectasia mutated protein ATM and breast cancer susceptibility proteins BRCA1 and BRCA2 (identified as FANCD1) with other known FA proteins suggests that FA proteins have a significant role in DNA repair/recombination and cell cycle control. The International Fanconi Anemia Registry (IFAR), a prospectively collected database of FA patients, allows us the unique opportunity to analyze the natural history of this rare, clinically heterogeneous disorder in a large number of patients. Of the 754 subjects in this study, 601 (80%) experienced the onset of bone marrow failure (BMF), and 173 (23%) had a total of 199 neoplasms. Of these neoplasms, 120 (60%) were hematologic and 79 (40%) were nonhematologic. The risk of developing BMF and hematologic and nonhematologic neoplasms increased with advancing age with a 90%, 33%, and 28% cumulative incidence, respectively, by 40 years of age. Univariate analysis revealed a significantly earlier onset of BMF and poorer survival for complementation group C compared with groups A and G; however, there was no significant difference in the time to hematologic or nonhematologic neoplasm development between these groups. Multivariate analysis of overall survival time shows that FANCC mutations (P =.007) and hematopoietic stem cell transplantation (P = <.0001) define a poor-risk subgroup. The results of this study of patients registered in the IFAR over a 20-year period provide information that will enable better prediction of outcome and aid clinicians with decisions regarding major therapeutic modalities.
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PMID:A 20-year perspective on the International Fanconi Anemia Registry (IFAR). 1258 46

We review the genes and proteins related to the homologous recombinational repair (HRR) pathway that are implicated in cancer through either genetic disorders that predispose to cancer through chromosome instability or the occurrence of somatic mutations that contribute to carcinogenesis. Ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), and an ataxia-like disorder (ATLD), are chromosome instability disorders that are defective in the ataxia telangiectasia mutated (ATM), NBS, and Mre11 genes, respectively. These genes are critical in maintaining cellular resistance to ionizing radiation (IR), which kills largely by the production of double-strand breaks (DSBs). Bloom syndrome involves a defect in the BLM helicase, which seems to play a role in restarting DNA replication forks that are blocked at lesions, thereby promoting chromosome stability. The Werner syndrome gene (WRN) helicase, another member of the RecQ family like BLM, has very recently been found to help mediate homologous recombination. Fanconi anemia (FA) is a genetically complex chromosomal instability disorder involving seven or more genes, one of which is BRCA2. FA may be at least partially caused by the aberrant production of reactive oxidative species. The breast cancer-associated BRCA1 and BRCA2 proteins are strongly implicated in HRR; BRCA2 associates with Rad51 and appears to regulate its activity. We discuss in detail the phenotypes of the various mutant cell lines and the signaling pathways mediated by the ATM kinase. ATM's phosphorylation targets can be grouped into oxidative stress-mediated transcriptional changes, cell cycle checkpoints, and recombinational repair. We present the DNA damage response pathways by using the DSB as the prototype lesion, whose incorrect repair can initiate and augment karyotypic abnormalities.
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PMID:Recombinational DNA repair and human disease. 1242 31

Phosphorylation of BRCA1 tumor suppressor protein is regulated during the cell cycle and in response to DNA damage. Several Ser/Thr kinases have been implicated in BRCA1 phosphorylation, including ATM/ATR, cdk2, and hChk2 kinases. In this study, phospho-Ser-specific antibodies recognizing Ser-988, -1423, -1497, and -1524 residues of BRCA1 were employed to study BRCA1 phosphorylation during the S and G2/M phases under conditions of DNA damage. We observed that IR (ionizing radiation) treatment induced phosphorylation of Ser-988/Ser-1524 during the S phase and of Ser-988/Ser-1423 during the G2/M phase. UV treatment induced phosphorylation of Ser-988 during the S phase and of Ser-1423 during the G2/M phase. Phosphorylation of serines 1423 and -1524 was not induced in HCC1937 breast cancer cells, which contain mutant BRCA1 protein. Confocal microscopy revealed that unphosphorylated BRCA1 localizes on chromosomes from metaphase through telophase, whereas Ser-988-phosphorylated BRCA1 resides in the inner chromosomal structure, centrosome, and the cleavage furrow during prophase through telophase. We also found that Ser-988-phosphorylated BRCA1 relocalizes to the perinuclear region when cells are subjected to IR or UV radiation in the S phase. These results reinforce a model wherein phosphorylation of specific residues of BRCA1 after DNA damage affects its localization and function.
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PMID:Cell cycle differences in DNA damage-induced BRCA1 phosphorylation affect its subcellular localization. 1242 29

Fanconi anaemia (FA) is a rare autosomal recessive disease characterized by increased spontaneous and DNA crosslinker-induced chromosome instability, progressive pancytopenia and cancer susceptibility. An increasing number of genes are involved in FA, including the breast cancer susceptibility gene BRCA2. Five of the FA proteins (FANCA, FANCC, FANCE, FANCF and FANCG) assemble in a complex that is required for FANCD2 activation in response to DNA crosslinks. Active FANCD2 then interacts with BRCA1 and forms discrete nuclear foci. FANCD2 is independently phosphorylated by ATM (the protein whose gene is mutated in ataxia telangiectasia) in response to ionizing radiation. In addition, the FA proteins are interconnected with other nuclear and cytoplasmic factors all related to cellular responses to carcinogenic stress and to caretaker and gatekeeper functions. In this review, the most recently published data on the molecular biology of the FA pathway and its molecular crosstalk with ATM, BRCA1 and BRCA2, proteins involved in xenobiotic and reactive oxygen species metabolism, apoptosis, cell cycle control and telomere stability, are summarized. The currently available data indicate that FA is a central node in a complex nuclear and cytoplasmic network of tumour suppressor and genome stability pathways fully committed to prevent cancer.
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PMID:The Fanconi anaemia genome stability and tumour suppressor network. 1243 50

Numerous reports have revealed that the tumor suppressor BRCA1 may play an important role in DNA damage repair. BRCA1 is expressed and phosphorylated during cell cycle progression and after DNA damage. BRCA1 is hypophosphorylated in G0-G1 and probably during mitosis as well. Kinases known to phosphorylate BRCA1 include cyclin-dependent kinase 2, as well as ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related kinase (ATR), which function in G2 checkpoint control. However, protein phosphatases responsible for dephosphorylation of BRCA1 had yet to be identified. hCds1, which acts downstream of ATM, also phosphorylates a BRCA1 fragment containing amino acids 759-1064 [BRCA1 fragment 4 (BF4)]. We have used a GST-BF4 protein phosphorylated by hCds1 [glutathione S-transferase (GST)-BF4-P] as a substrate to identify potential phosphatases responsible for BRCA1 dephosphorylation. Data presented here show that both recombinant protein phosphatase 1 alpha (PP1alpha) catalytic subunit and endogenous PP1alpha dephosphorylate GST-BF4-P. Inhibitor 2 abolishes this activity. Overexpression of PP1alpha partially inhibits hyperphosphorylation of BRCA1 after ionizing radiation, indicating that PP1alpha dephosphorylates BRCA1 in vivo. BRCA1 and PP1alpha reciprocally coimmunoprecipitate, and a glutathione S-transferase pull-down assay shows that PP1alpha catalytic subunit associates directly with the BF4 region of BRCA1. In addition, BRCA1 inhibits PP1alpha activity. Therefore, BRCA1 is both a substrate and a regulator of PP1alpha. The interaction between BRCA1 and PP1alpha thus may play a role in DNA damage repair and cell cycle progression.
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PMID:Regulation of BRCA1 phosphorylation by interaction with protein phosphatase 1alpha. 1243 14

To facilitate association-based linkage studies we have studied the linkage disequilibrium (LD) and haplotype architecture around five genes of interest for cancer risk: ATM, BRCA1, BRCA2, RAD51, and TP53. Single nucleotide polymorphisms (SNPs) were identified and used to construct haplotypes that span 93-200 kb per locus with an average SNP density of 12 kb. These markers were genotyped in four ethnically defined populations that contained 48 each of African Americans, Asian Americans, Hispanic Americans, and European Americans. Haplotypes were inferred using an expectation maximization (EM) algorithm, and the data were analyzed using D', R(2), Fisher's exact P-values, and the four-gamete test for recombination. LD levels varied widely between loci from continuously high LD across 200 kb to a virtual absence of LD across a similar length of genome. LD structure also varied at each gene and between populations studied. This variation indicates that the success of linkage-based studies will require a precise description of LD at each locus and in each population to be studied. One striking consistency between genes was that at each locus a modest number of haplotypes present in each population accounted for a high fraction of the total number of chromosomes. We conclude that each locus has its own genomic profile with regard to LD, and despite this there is the widespread trend of relatively low haplotype diversity. As a result, a low marker density should be adequate to identify haplotypes that represent the common variation at a locus, thereby decreasing costs and increasing efficacy of association studies.
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PMID:Haplotype and linkage disequilibrium architecture for human cancer-associated genes. 1246 88

The present report deals with the functional relationships among protein complexes which, when mutated, are responsible for four human syndromes displaying cancer proneness, and whose cells are deficient in DNA double-strand break (DSB) repair. In some of them, the cells are also unable to activate the proper checkpoint, while in the others an unduly override of the checkpoint-induced arrest occurs. As a consequence, all these patients display genome instability. In ataxia-telangiectasia, the mutated protein (ATM) is a kinase, which acts as a transducer of DNA damage signalling. The defective protein in the ataxia-telangiectasia-like disorder is a DNase (the Mre11 nuclease) that in vivo produces single-strand tails at both sides of DSBs. Mre11 is always present with the Rad50 ATPase in a protein machine: the nuclease complex. In mammals, this complex also contains nibrin, the protein mutated in the Nijmegen syndrome. Nibrin confers new abilities to the nuclease complex, and can also bind to BRCA1 (one of the two proteins mutated in familial breast cancer). BRCA1 has a central motif that binds with high affinity to cruciform DNA, a structure present in places where the DNA loops are anchored to the chromosomal axis or scaffold. The BRCA1 x cruciform DNA complex should be released to allow the nuclease complex to work in DNA recombinational repair of DSBs. BRCA1 also acts as a scaffold for the assembly of ATPases such as Rad51, responsible for the somatic homologous recombination. Loss of the BRCA1 gene prevents cell survival after exposure to cross-linkers. The BRCA1-RING domain is an E3-ubiquitin ligase. It can mono-ubiquitinate the FANCD2 protein, mutated in one of the Fanconi anemia complementation groups, to regulate it. Finally, during DNA replication, the nuclease complex and its activating ATM kinase are integrated in the BRCA1-associated surveillance complex (BASC) that contains, among others, enzymes required for mismatch excision repair. In short, the proteins missing in these syndromes have in common their BRCA1-mediated assembly into multimeric machines responsible for the surveillance of DNA replication, DSB recombinational repair, and the removal of DNA cross-links.
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PMID:Human syndromes with genomic instability and multiprotein machines that repair DNA double-strand breaks. 1250 2

With the increasing of the incidence rate of breast carcinoma year after year, the susceptibility genes of breast carcinoma was paid more and more attention. The study on susceptibility genes play an important role in early diagnosis and prevention for the individuals with family history of breast carcinoma, elucidation of pathologic mechanism of sporadic breast carcinoma, early diagnosis and adjudging prognosis, research on drug sensitivity, differential diagnosis of benign and malignant disease, etc. There were many studies on the high-penetrance susceptibility genes (BRCA1, BRCA2). However, some low-penetrance susceptibility gene, for example, the members of hormone metabolism related enzymes genes CYP family (CYP17, CYP19, CYP1A1, etc.), the carcinogen metabolism related gene (GSTM1, NAT1, NAT2), and DNA damage repair gene (ATM) were not clearly understood. The aim of this study was to review the present research situation of common susceptibility genes of breast carcinoma found already.
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PMID:[Research on breast cancer susceptibility genes]. 1250 56

Fanconi anaemia (FA) is a rare genetic cancer-susceptibility syndrome that is characterized by congenital abnormalities, bone-marrow failure and cellular sensitivity to DNA crosslinking agents. Seven FA-associated genes have recently been cloned, and their products were found to interact with well-known DNA-damage-response proteins, including BRCA1, ATM and NBS1. The FA proteins could therefore be involved in the cell-cycle checkpoint and DNA-repair pathways. Recent studies implicate the FA proteins in the process of repairing chromosome defects that occur during homologous recombination, and disruption of the FA genes results in chromosome instability--a common feature of many human cancers.
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PMID:The Fanconi anaemia/BRCA pathway. 1250 64


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