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)

A 12-year-old male patient with ataxia telangiectasia developed an acute lymphoblastic leukemia of T-cell phenotype. The lymphoblasts showed uniform surface expression of CD3, CD7, CD8, and T-cell receptor (TCR) alpha/beta chains, positive immunofluorescent staining of terminal deoxynucleotidyl transferase, complex cytogenetic aberrations including t(14;14) (q11;q32) and unique rearrangements of TCR beta and gamma chain genes, indicating the clonal expansion of leukemic cells. CD25 expression could be readily induced on the leukemic cells by mitogenic stimulation, followed by CD71 expression, but interleukin-2 production and subsequent proliferation in response to mitogens were subnormal.
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PMID:Functional and molecular characteristics of acute lymphoblastic leukemia cells with a mature T-cell phenotype from a patient with ataxia telangiectasia. 199 61

In the genetic disorder ataxia telangiectasia (AT), humoral (B) and cellular (T) immunological abnormalities are frequently observed. As a consequence, AT patients are predisposed to life-threatening sinopulmonary infections. The pathogenic mechanisms remain unknown, but a role for ATM in signal transduction from membrane receptors has been proposed. We have explored the effects of a defective ATMgene on isolated human T-lineage cells from 13 AT patients with proven T cell dysfunction by transforming their CD4(+) and CD8(+) T lymphocytes with Herpesvirus saimiri, and analyzing their signaling behavior as compared to normal controls. Several functional parameters were assayed in response to both membrane (anti-CD3 and IL-2) and transmembrane (phorbol myristate acetate plus the calcium ionophore ionomycin) stimuli: (i) calcium mobilization, (ii) induction of activation molecules (CD25, CD40 ligand, CD69 and CD71), (iii) cytokine synthesis (IL-2 and tumor necrosis factor-alpha) and (iv) proliferation. All these early and late activation events were found to be normal in the transformed ATM-/-T cells, indicating that ATM is not necessary for their induction. As expected, ATM-/- transformed T cells showed an increased radiosensitivity by both radioresistant DNA synthesis and cell survival assays. In contrast to an earlier report testing transformed B lymphocytes, our results indicate that transformed mature peripheral T lymphocytes from AT patients do not have intrinsic immune function defects. Rather, the described T-lineage signaling impairments observed in patients may be secondary in vivo to extrinsic ATM-dependent suppressive factors and/or to a developmental defect. These transformed T cells may help to understand the distinct biological role of ATM in different cell types and to develop rational therapies for the immunological dysfunction of AT patients.
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PMID:Membrane and transmembrane signaling in Herpesvirus saimiri-transformed human CD4(+) and CD8(+) T lymphocytes is ATM-independent. 1083 20

Chronic lymphocytic leukemia (CLL) is a common adult leukemia characterized by the accumulation of mature neoplastic B-lymphocytes. Typically, CLL follows an indolent course, with most patients surviving for many years. However, 10-20% of CLL patients carry 11q23 chromosomal deletions and often exhibit a more severe disease course, with earlier onset of symptoms, shortened lymphocyte doubling time, poor response to therapy, and shortened survival. The molecular basis for 11q23 deletions resulting in a poor prognosis is currently poorly understood. The tumor suppressor gene, ataxia-telangiectasia mutated (ATM, 11q22.3-23.1), is considered a likely candidate gene whose loss could result in the poor prognosis associated with 11q23 deletion and is mutated in a significant percentage of CLL cases. Recently, recombinant ATM expression in ATM-deficient cells was found to decrease transferrin receptor (TfR) expression, suggesting that deletion of the chromosomal region carrying ATM results in increased TfR expression. TfR imports iron into cells, an event necessary for DNA synthesis and cell growth. Additionally, rapidly growing malignant cells, including lymphomas and CLL, often express high TfR levels. Based on this, we propose that one molecular mechanism by which 11q23 deletions confer a poor prognosis in CLL is via increased TfR expression secondary to ATM loss, resulting in the increased cellular iron import, and hence increased capacity for malignant growth. Our hypothesis may also partially explain why gallium, an atomically iron-like toxic metal that binds to transferrin and the TfR is incorporated into cells and was previously demonstrated to have anti-tumor activity in patients with lymphomas refractory to other chemotherapeutic treatments.
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PMID:Increased transferrin receptor expression following 11q23 deletion as a mechanism of malignant progression in chronic lymphocytic leukemia. 1632 28

Ataxia-telangiectasia (A-T) is characterized by ataxia, genomic instability, and increased cancer incidence. Previously, iron chelator concentrations which suppressed normal cell colony formation increased A-T cell colony formation. Similarly, iron chelators preferentially increased A-T cell colony formation following peroxide exposure compared to normal cells. Last, A-T cells exhibited increased short-term sensitivity to labile iron exposure compared to normal cells, an event corrected by recombinant ATM (rATM) expression. Since chromosomal damage is important in A-T pathology and iron chelators exert beneficial effects on A-T cells, we hypothesized that iron chelators would reduce A-T cell chromosomal breaks. We treated A-T, normal, and A-T cells expressing rATM with labile iron, iron chelators, antioxidants, and t-butyl hydroperoxide, and examined chromosomal breaks and ATM activation. Additionally, the effect of ATM-deficiency on transferrin receptor (TfR) expression and TfR activity blockage in A-T and syngeneic A-T cells expressing rATM was examined. We report that (1) iron chelators and iron-free media reduce spontaneous and t-butyl hydroperoxide-induced chromosomal breaks in A-T, but not normal, or A-T cells expressing rATM; (2) labile iron exposure induces A-T cell chromosomal breaks, an event lessened with rATM expression; (3) desferal, labile iron, and copper activate ATM; (4) A-T cell TfR expression is lowered with rATM expression and (5) blocking TfR activity with anti-TfR antibodies increases A-T cell colony formation, while lowering chromosomal breaks. ATM therefore functions in iron responses and the maintenance of genomic stability following labile iron exposure.
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PMID:Iron chelators reduce chromosomal breaks in ataxia-telangiectasia cells. 1695 48

Esophageal squamous cell carcinoma (ESCC) is one of the most common and aggressive cancers worldwide, especially in China, with poor prognosis due to the lack of effective therapeutic strategies. Here, the anticancer effect and pharmacological mechanism of a newly synthesized Fe(II) phenanthroline complex was studied in ESCC. Our data showed that transferrin receptor 1 (TFR1) was specifically overexpressed in ESCC tissues compared to its expression in normal esophageal tissues, a finding further supported by public datasets. The newly synthesized Fe(II) complex was selectively transported into ESCC cells overexpressing TFR1 through TFR1-mediated endocytosis and exhibited anticancer activity in a dose-dependent manner. The mechanistic study elucidated that the Fe(II) complex caused cell cycle arrest at the G0/G1 phase by blocking the CDK4/6-cyclin D1 complex and induced mitochondria-mediated apoptosis. Furthermore, exposure to the Fe(II) complex led to excessive reactive oxygen species (ROS) accumulation by thioredoxin reductase (TrxR) inhibition and DNA double-strand breaks (DSBs), which in turn sequentially activated ATM, CHK1/2 and p53. Moreover, combination treatment with cisplatin and the Fe(II) complex exhibited a synergistic effect in ESCC cells. Taken together, our results initially suggest the potential application of the Fe(II) complex in ESCC chemotherapy, especially for patients with TFR1 overexpression.
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PMID:A novel iron(II) phenanthroline complex exhibits anticancer activity against TFR1-overexpressing esophageal squamous cell carcinoma cells through ROS accumulation and DNA damage. 3107 3