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TLR9 engagement on CD4 T lymphocytes represses gamma-radiation-induced apoptosis through activation of checkpoint kinase response elements.

ABSTRACT: T cell-based therapies have much promise in cancer treatment. This approach may be enhanced if used in combination with radiotherapy provided that tumor-specific T cells can be protected against the effects of radiotherapy. Previously, we demonstrated that administration of TLR9 ligand into mice decreased activation- and serum deprivation-induced cell death in T cells. We hypothesized that TLR9 engagement on T lymphocytes decreased apoptosis after cellular stress. We show that TLR9 engagement on murine CD4 T cells reduces gamma-radiation-induced apoptosis as judged by decreased annexin-V/PI staining, caspase-3 activation, and PARP cleavage. TLR9-stimulated cells show heightened accumulation at the G2 cell-cycle phase and increased DNA repair rates. Irradiated, TLR9-engaged cells showed higher levels of phosphorylated Chk1 and Chk2. While the levels of activated ATM in response to IR did not differ between TLR9-stimulated and unstimulated cells, inhibition of ATM/ATR and Chk1/Chk2 kinases abolished the radioprotective effects in TLR9-stimulated cells. In vivo, TLR9-stimulated cells displayed higher radio resistance than TLR9-stimulated MyD88(-/-) T cells and responded to antigenic stimulation after total body irradiation. These findings show, for the first time, that TLR9 engagement on CD4 T cells reduces IR-induced apoptosis by influencing cell-cycle checkpoint activity, potentially allowing for combinatorial immunotherapy and radiotherapy.

SUBMITTER: Zheng L

PROVIDER: S-EPMC2254540 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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TLR9 engagement on CD4 T lymphocytes represses gamma-radiation-induced apoptosis through activation of checkpoint kinase response elements.

Zheng Liqin L Asprodites Nicole N Keene Angela H AH Rodriguez Paulo P Brown Kevin D KD Davila Eduardo E

Blood 20071217 5

T cell-based therapies have much promise in cancer treatment. This approach may be enhanced if used in combination with radiotherapy provided that tumor-specific T cells can be protected against the effects of radiotherapy. Previously, we demonstrated that administration of TLR9 ligand into mice decreased activation- and serum deprivation-induced cell death in T cells. We hypothesized that TLR9 engagement on T lymphocytes decreased apoptosis after cellular stress. We show that TLR9 engagement on ...[more]

PMID: 18086870

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Project description:Ataxia telangiectasia (AT) is an autosomal recessive disorder characterized by neuronal degeneration, telangiectasias, acute cancer predisposition, and hypersensitivity to ionizing radiation (IR). The gene defective in AT, ATM (for AT-mutated), encodes a protein, pATM that has been found to have IR-inducible kinase activity. Cells from individuals with AT exhibit severely attenuated cell cycle checkpoints in response to gamma radiation exposure. pATM has been hypothesized to act as part of a complex that senses DNA damage, in particular, DNA double strand breaks. We are studying the pATM-dependent gene expression responses to a dose of 1.5 Gy radiation in lymphoblastoid cell lines from multiple individuals with either wild type or mutated ATM. The gene expression analyses were performed on Agilent Human 1A Oligo chips containing approximately 16,000 60mer probes. We identified a set of genes whose gene expression changes are ATM-dependent following exposure to 1.5 Gy IR. This set of genes was tested by real time quantitative PCR analysis. The study consists of one dose group - 1.5 Gray gamma radiation. Samples were collected 6 hr following irradiation (treated) or mock irradiation (controls) for each culture. Each culture has a treated sample and a control sample. There are cultures from 6 wild-type ATM individuals and cultures from 6 individuals that are ATM-deficient, for a total of 12 cultures. Hybridizations compared RNA extracted from each individual culture's treated sample against its corresponding control sample, and were performed as dye-flip duplicates (1 replicate in each direction). Hybridizations were performed on the Human 1A Oligo Chips using low input, direct labeling at Paradigm Genetics Laboratory. Microarray scanning was performed with the Agilent G2565AA Scanner. Paradigm Standard Operating Procedures were followed for quality analysis, sample labeling, microarray hybridization and washing, scanning, image analysis and initial data analysis.

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Dataset Information

TLR9 engagement on CD4 T lymphocytes represses gamma-radiation-induced apoptosis through activation of checkpoint kinase response elements.

Publications

TLR9 engagement on CD4 T lymphocytes represses gamma-radiation-induced apoptosis through activation of checkpoint kinase response elements.

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