Loss of BIM augments resistance of ATM-deficient thymocytes to DNA damage-induced apoptosis but does not accelerate lymphoma development.
Ontology highlight
ABSTRACT:
SUBMITTER: Delbridge AR
PROVIDER: S-EPMC5635225 | biostudies-literature | 2017 Nov
REPOSITORIES: biostudies-literature
Publications
Loss of BIM augments resistance of ATM-deficient thymocytes to DNA damage-induced apoptosis but does not accelerate lymphoma development.
Delbridge Alex Rd AR Grabow Stephanie S Strasser Andreas A
Cell death and differentiation 20170908 11
Similar Datasets
Project description:Caspase-2, the most evolutionarily conserved member of the caspase family, has been shown to be involved in apoptosis induced by various stimuli. Our recent work indicates that caspase-2 has putative functions in tumor suppression and protection against cellular stress. As such, the loss of caspase-2 enhances lymphomagenesis in Eµ-Myc transgenic mice, and caspase-2 KO (Casp2(-/-)) mice show characteristics of premature aging. However, the extent and specificity of caspase-2 function in tumor suppression is currently unclear. To further investigate this, ataxia telangiectasia mutated KO (Atm(-/-)) mice, which develop spontaneous thymic lymphomas, were used to generate Atm(-/-)Casp2(-/-) mice. Initial characterization revealed that caspase-2 deficiency enhanced growth retardation and caused synthetic perinatal lethality in Atm(-/-) mice. A comparison of tumor susceptibility demonstrated that Atm(-/-)Casp2(-/-) mice developed tumors with a dramatically increased incidence compared with Atm(-/-) mice. Atm(-/-)Casp2(-/-) tumor cells displayed an increased proliferative capacity and extensive aneuploidy that coincided with elevated oxidative damage. Furthermore, splenic and thymic T cells derived from premalignant Atm(-/-)Casp2(-/-) mice also showed increased levels of aneuploidy. These observations suggest that the tumor suppressor activity of caspase-2 is linked to its function in the maintenance of genomic stability and suppression of oxidative damage. Given that ATM and caspase-2 are important components of the DNA damage and antioxidant defense systems, which are essential for the maintenance of genomic stability, these proteins may synergistically function in tumor suppression by regulating these processes.
| S-EPMC3856814 | biostudies-other
Project description:Both oxidative stress and endoplasmic reticulum (ER) stress have been implicated in carcinogenesis. It is well documented that cells deficient in the ataxia-telangiectasia mutated (ATM) gene undergo oxidative stress, which is critically involved in thymic lymphomagenesis in Atm-/- mice. Here we demonstrate that undifferentiated Atm-/- thymocytes show signs of ER stress and of the unfolded protein response (UPR). Using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis, we identified 22 differentially expressed proteins, including the ER stress marker glucose-regulated protein 78 (GRP78), in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells relative to Atm+/+ thymocytes. The phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2alpha), a UPR marker, was also increased in Atm-/- thymocytes. Cells of the ATL-1 line, which were derived from an Atm-/- mouse thymic lymphoma, were more sensitive to the ER stress inducer tunicamycin than were Atm+/+ thymic leukemia ASL-1 cells. Notably, treatment with hydrogen peroxide duplicated the effects of ATM deficiency in cultured thymocytes, and treatment with the novel cell-permeable thiol antioxidant N-acetylcysteine amide (AD4) reduced elevated p-eIF2alpha levels in thymocytes of Atm-/- mice. Thus, we propose that ER stress and the UPR are secondary to oxidative stress in Atm-/- thymocytes.
| S-EPMC2244691 | biostudies-literature
Project description:genomic profiling of murine thymocytes of Atm deficient mice with and without T-cell lymphoma Keywords: genetic modification
2008-07-15 | GSE10844 | GEO
Project description:During the CD4(-)CD8(-) (DN) stage of T-cell development, RAG-dependent DNA breaks and V(D)J recombination occur at three T-cell receptor (TCR) loci: TCRβ, TCRγ and TCRδ. During this stage, abnormal trans-rearrangements also take place between TCR loci, occurring at increased frequency in absence of the DNA damage response mediator ataxia telangiectasia mutated (ATM). Here, we use this model of physiologic trans-rearrangement to study factors that predispose to rearrangement and the role of ATM in preventing chromosomal translocations. The frequency of DN thymocytes with DNA damage foci at multiple TCR loci simultaneously is increased 2- to 3-fold in the absence of ATM. However, trans-rearrangement is increased 10 000- to 100 000-fold, indicating that ATM function extends beyond timely resolution of DNA breaks. RAG-mediated synaptic complex formation occurs between recombination signal sequences with unequal 12 and 23 base spacer sequences (12/23 rule). TCR trans-rearrangements violate this rule, as we observed similar frequencies of 12/23 and aberrant 12/12 or 23/23 recombination products. This suggests that trans-rearrangements are not the result of trans-synaptic complex formation, but they are instead because of unstable cis synaptic complexes that form simultaneously at distinct TCR loci. Thus, ATM suppresses trans-rearrangement primarily through stabilization of DNA breaks at TCR loci.
| S-EPMC3632137 | biostudies-literature
Project description:The Ataxia Telangiectasia-mutated (ATM) kinase senses DNA double-strand breaks (DSB) and facilitates their repair. In humans, ATM deficiency predisposes to B- and T-cell lymphomas, but in mice it leads only to thymic lymphomas. We tested the hypothesis that increased DSB frequency at a cellular oncogene could promote B-cell lymphoma by generating ATM-deficient mice with a V(D)J recombination target (DJβ cassette) within c-myc intron 1 ("DA" mice). We also generated ATM-deficient mice carrying an Eμ-Bcl-2 transgene (AB mice) to test whether enhanced cellular survival could promote B-cell lymphomas. About 30% of DA or AB mice and nearly 100% of mice harboring the combined genotypes (DAB mice) developed mature B-cell lymphomas. In all genotypes, B-cell tumors harbored oncogenic c-myc amplification generated by breakage-fusion-bridge (BFB) from dicentric chromosomes formed through fusion of IgH V(D)J recombination-associated DSBs on chromosome 12 to sequences downstream of c-myc on chromosome 15. AB tumors demonstrate that B lineage cells harboring spontaneous DSBs leading to IgH/c-myc dicentrics are blocked from progressing to B-cell lymphomas by cellular apoptotic responses. DA and DAB tumor translocations were strictly linked to the cassette, but occurred downstream, frequently in a 6-kb region adjacent to c-myc that harbors multiple cryptic V(D)J recombination targets, suggesting that bona fide V(D)J target sequences may activate linked cryptic targets. Our findings indicate that ATM deficiency allows IgH V(D)J recombination DSBs in developing B cells to generate dicentric translocations that, via BFB cycles, lead to c-myc-activating oncogenic translocations and amplifications in mature B cells.
| S-EPMC4156541 | biostudies-literature
Project description:Mantle cell lymphoma (MCL) is a highly aggressive B-cell lymphoma resistant to conventional chemotherapy. Although defined by the characteristic t(11;14) translocation, MCL has not been recapitulated in transgenic mouse models of cyclin D1 overexpression alone. Indeed, several genetic aberrations have been identified in MCL that may contribute to its pathogenesis and chemoresistance. Of particular interest is the frequent biallelic deletion of the proapoptotic BCL-2 family protein BIM. BIM exerts its pro-death function via its α-helical BH3 death domain that has the dual capacity to inhibit antiapoptotic proteins such as BCL-2 and MCL-1 and directly trigger proapoptotic proteins such as the mitochondrial executioner protein BAX. To evaluate a functional role for Bim deletion in the pathogenesis of MCL, we generated cyclin D1-transgenic mice harboring Bim-deficient B cells. In response to immunization, Eμ(CycD1)CD19(CRE)Bim(fl/fl) mice manifested selective expansion of their splenic mantle zone compartment. Three distinct immune stimulation regimens induced lymphomas with histopathologic and molecular features of human MCL in a subset of mice. Thus, deletion of Bim in B cells, in the context of cyclin D1 overexpression, disrupts a critical control point in lymphoid maturation and predisposes to the development of MCL. This genetic proof of concept for MCL pathogenesis suggests an opportunity to reactivate the death pathway by pharmacologic mimicry of proapoptotic BIM.
| S-EPMC3916879 | biostudies-other
Project description:Production of a functional peripheral T cell compartment typically involves massive expansion of the bone marrow progenitors that seed the thymus. There are two main phases of expansion during T cell development, following T lineage commitment of double-negative (DN) 2 cells and after successful rearrangement and selection for functional TCRβ chains in DN3 thymocytes, which promotes the transition of DN4 cells to the DP stage. The signals driving the expansion of DN2 thymocytes are well studied. However, factors regulating the proliferation and survival of DN4 cells remain poorly understood. Here, we uncover an unexpected link between the transcription factor Zfp335 and control of cGAS/STING-dependent cell death in post-β-selection DN4 thymocytes. Zfp335 controls survival by sustaining expression of Ankle2, which suppresses cGAS/STING-dependent cell death. Together, this study identifies Zfp335 as a key transcription factor regulating the survival of proliferating post-β-selection thymocytes and demonstrates a key role for the cGAS/STING pathway in driving apoptosis of developing T cells.
| S-EPMC9537144 | biostudies-literature
Project description:To find genes deregulated in the pathogenisis of T-cells in Atm deficient mice, we performed expression profiling of Atm deficient thymic lymphomas, wildtype thymi and Atm deficient thymi without macroscopic enlargement, representing an intermediate stage in the process of tumorigenisis. Keywords: genetic modification, disease state analysis
2008-07-15 | GSE10807 | GEO
Project description:Low-dose radiation risks remain unclear owing to a lack of sufficient studies. We previously reported that low-dose, long-term fractionated radiation (FR) with 0.01 or 0.05 Gy/fraction for 31 d inflicts oxidative stress in human fibroblasts due to excess levels of mitochondrial reactive oxygen species (ROS). To identify the small effects of low-dose radiation, we investigated how mitochondria respond to low-dose radiation in radiosensitive human ataxia telangiectasia mutated (ATM)- and Nijmegen breakage syndrome (NBS)1-deficient cell lines compared with corresponding cell lines expressing ATM and NBS1. Consistent with previous results in normal fibroblasts, low-dose, long-term FR increased mitochondrial mass and caused accumulation of mitochondrial ROS in ATM- and NBS1-complemented cell lines. Excess mitochondrial ROS resulted in mitochondrial damage that was in turn recognized by Parkin, leading to mitochondrial autophagy (mitophagy). In contrast, ATM- and NBS1-deficient cells showed defective induction of mitophagy after low-dose, long-term FR, leading to accumulation of abnormal mitochondria; this was determined by mitochondrial fragmentation and decreased mitochondrial membrane potential. Consequently, apoptosis was induced in ATM- and NBS1-deficient cells after low-dose, long-term FR. Antioxidant N-acetyl-L-cysteine was effective as a radioprotective agent against mitochondrial damage induced by low-dose, long-term FR among all cell lines, including radiosensitive cell lines. In conclusion, we demonstrated that mitochondria are target organelles of low-dose radiation. Mitochondrial response influences radiation sensitivity in human cells. Our findings provide new insights into cancer risk estimation associated with low-dose radiation exposure.
| S-EPMC4889229 | biostudies-literature
Project description:BackgroundPersonalised medicine strategies may improve outcomes in pancreatic ductal adenocarcinoma (PDAC), but validation of predictive biomarkers is required. Having developed a clinical trial to assess the ATR inhibitor, AZD6738, in combination with gemcitabine (ATRi/gem), we investigated ATM loss as a predictive biomarker of response to ATRi/gem in PDAC.MethodsThrough kinase inhibition, siRNA depletion and CRISPR knockout of ATM, we assessed how ATM targeting affected the sensitivity of PDAC cells to ATRi/gem. Using flow cytometry, immunofluorescence and immunoblotting, we investigated how ATRi/gem synergise in ATM-proficient and ATM-deficient cells, before assessing the impact of ATM loss on ATRi/gem sensitivity in vivo.ResultsComplete loss of ATM function (through pharmacological inhibition or CRISPR knockout), but not siRNA depletion, sensitised to ATRi/gem. In ATM-deficient cells, ATRi/gem-induced replication catastrophe was augmented, while phospho-Chk2-T68 and phospho-KAP1-S824 persisted via DNA-PK activity. ATRi/gem caused growth delay in ATM-WT xenografts in NSG mice and induced regression in ATM-KO xenografts.ConclusionsATM loss augments replication catastrophe-mediated cell death induced by ATRi/gem and may predict clinical responsiveness to this combination. ATM status should be carefully assessed in tumours from patients with PDAC, since distinction between ATM-low and ATM-null could be critical in maximising the success of clinical trials using ATM expression as a predictive biomarker.
| S-EPMC7591912 | biostudies-literature