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Al Jīzah, Egypt

Alagoz M.,University of Sheffield | Alagoz M.,University of Sussex | Wells O.S.,University of Sussex | El-Khamisy S.F.,University of Sheffield | And 2 more authors.
Nucleic Acids Research | Year: 2014

Base damage and topoisomerase I (Top1)-linked DNA breaks are abundant forms of endogenous DNA breakage, contributing to hereditary ataxia and underlying the cytotoxicity of a wide range of anti-cancer agents. Despite their frequency, the overlapping mechanisms that repair these forms of DNA breakage are largely unknown. Here, we report that depletion of Tyrosyl DNA phosphodiesterase 1 (TDP1) sensitizes human cells to alkylation damage and the additional depletion of apurinic/apyrimidinic endonuclease I (APE1) confers hypersensitivity above that observed for TDP1 or APE1 depletion alone. Quantification of DNA breaks and clonogenic survival assays confirm a role for TDP1 in response to base damage, independently of APE1. The hypersensitivity to alkylation damage is partly restored by depletion of Top1, illustrating that alkylating agents can trigger cytotoxic Top1-breaks. Although inhibition of PARP activity does not sensitize TDP1-deficient cells to Top1 poisons, it confers increased sensitivity to alkylation damage, highlighting partially overlapping roles for PARP and TDP1 in response to genotoxic challenge. Finally, we demonstrate that cancer cells in which TDP1 is inherently deficient are hypersensitive to alkylation damage and that TDP1 depletion sensitizes glioblastoma-resistant cancer cells to the alkylating agent temozolomide. © The Author(s) 2013.

Gomez-Herreros F.,University of Sussex | Schuurs-Hoeijmakers J.H.M.,Radboud University Nijmegen | Schuurs-Hoeijmakers J.H.M.,Donders Institute for Brain | McCormack M.,Royal College of Surgeons in Ireland | And 17 more authors.
Nature Genetics | Year: 2014

Topoisomerase II (TOP2) removes torsional stress from DNA and facilitates gene transcription by introducing transient DNA double-strand breaks (DSBs). Such DSBs are normally rejoined by TOP2 but on occasion can become abortive and remain unsealed. Here we identify homozygous mutations in the TDP2 gene encoding tyrosyl DNA phosphodiesterase-2, an enzyme that repairs 'abortive' TOP2-induced DSBs, in individuals with intellectual disability, seizures and ataxia. We show that cells from affected individuals are hypersensitive to TOP2-induced DSBs and that loss of TDP2 inhibits TOP2-dependent gene transcription in cultured human cells and in mouse post-mitotic neurons following abortive TOP2 activity. Notably, TDP2 is also required for normal levels of many gene transcripts in developing mouse brain, including numerous gene transcripts associated with neurological function and/or disease, and for normal interneuron density in mouse cerebellum. Collectively, these data implicate chromosome breakage by TOP2 as an endogenous threat to gene transcription and to normal neuronal development and maintenance. © 2014 Nature America, Inc. All rights reserved.

Talaat R.M.,Sadat City University | Alrefaey S.A.,Sadat City University | Bassyouni I.H.,Cairo University | Ashour M.E.,Sadat City University | And 2 more authors.
Lupus | Year: 2016

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Cytokine gene polymorphisms play an important role in SLE. Thus, this study aimed to investigate the associations between interleukin 6 (IL-6) and interleukin 10 (IL-10) promoter single-nucleotide polymorphisms (SNPs) and their susceptibility to SLE and the implications for plasma levels. We genotyped IL-6-174G/C (rs1800795) using mutagenically separated polymerase chain reaction (MS-PCR) and IL-10-1082G/A (rs1800896) and -819C/T (rs1800871) using sequence specific primer polymerase chain reaction (SSP-PCR) in 100 Egyptian patients and 119 controls. The plasma levels of IL-6 and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA). There was significant increase in the frequency of IL-6 (-174) GG genotype (P < 0.05) and G allele (P < 0.01) compared to controls. A significant increase in the distribution of IL-10 (-1082G/A) GG (P < 0.05) and AA (P < 0.05) genotypes and a significant reduction in the frequency of GA genotype (P < 0.05) was found in SLE patients. The mean serum concentration of IL-6 (P < 0.001) and IL-10 (P < 0.001) was significantly elevated in SLE patients compared to healthy controls. There was no significant association of the most common clinical findings and IL-6 and IL-10 gene polymorphisms in SLE patients. In conclusion, our preliminary study indicated that both GG genotype and G allele of IL-6 (-174G/C) could be considered as risk factors for SLE. In addition, the polymorphisms at IL-10 (-1082 G/G and AA) may play a role in SLE susceptibility in Egyptian patients. Larger prospective studies are needed to confirm our findings. © The Author(s) 2015.

Meisenberg C.,University of Sussex | Gilbert D.C.,Sussex Cancer Center | Chalmers A.,University of Glasgow | Gollins S.,University of Wales | And 4 more authors.
Molecular Cancer Therapeutics | Year: 2015

Colorectal cancer is the third most common cancer in the world. Despite surgery, up to 50% of patients relapse with incurable disease. First-line chemotherapy uses the topoisomerase 1 (TOP1) poison irinotecan, which triggers cell death by trapping TOP1 on DNA. The removal of TOP1 peptide from TOP1-DNA breaks is conducted by tyrosyl-DNA phosphodiesterase 1 (TDP1). Despite putative roles for TDP1 and TOP1 in colorectal cancer, their role in cellular and clinical responses to TOP1-targeting therapies remains unclear. Here, we show varying expression levels of TOP1 and TDP1 polypeptides in multiple colorectal cancer cell lines and in clinical colorectal cancer samples. TDP1 overexpression or TOP1 depletion is protective. Conversely, TDP1 depletion increases DNA-strand breakage and hypersensitivity to irinotecan in a TOP1-dependent manner, presenting a potential therapeutic opportunity in colorectal cancer. TDP1 protein levels correlate well with mRNA and with TDP1 catalytic activity. However, no correlation is observed between inherent TDP1 or TOP1 levels alone and irinotecan sensitivity, pointing at their limited utility as predictive biomarkers in colorectal cancer. These findings establish TDP1 as a potential therapeutic target for the treatment of colorectal cancer and question the validity of TOP1 or TDP1 on their own as predictive biomarkers for irinotecan response. ©2014 AACR.

Talaat R.M.,University of Sadat City | Ashour M.E.,University of Sadat City | Ashour M.E.,Helmy Institute | Bassyouni I.H.,Cairo University | Raouf A.A.,Menoufia University
Immunobiology | Year: 2014

Cytokines play critical roles in the pathogenesis of Behçet's disease (BD). They mediated many of the effectors and regulatory functions of immune and inflammatory responses. Many studies have linked Interleukin-6 (IL-6) and Interleukin-10 (IL-10) pathologically to BD. Thus, this study aimed to investigate the associations between IL-6 and IL-10 promoter single-nucleotide polymorphisms (SNPs) and the susceptibility to BD and their implication on plasma levels. We genotyped IL-6 -174 G/C (rs1800795) using Mutagenically Separated Polymerase Chain Reaction PCR (MS-PCR) and IL-10 -1082 G/A (rs1800896) and -819 C/T (rs1800871) using Sequence Specific Primer PCR (SSP-PCR) in 87 Egyptian patients and 97 controls. The plasma levels of IL-6 and IL-10 were measured using Enzyme-linked Immunosorbent Assay (ELISA). Significant increase in the frequency of -1082 GG genotype (P < 0.05, OR = 2.25, 95%CI = 1.03-4.91) and significant decrease in the frequency of -1082 GA genotype (P < 0.05, OR = 0.53, 95%CI = 0.29-0.96) was demonstrated in BD patients compare to controls. Patients with genital ulcer had significantly lower frequency of -1082 GG (P < 0.05, OR 0.2, 95% CI = 0.04-0.99) and G allele (P < 0.05, OR = 0.28, 95%CI = 0.08-0.93), while patients with ocular manifestations had significantly higher frequency of -1082 G allele (P < 0.01, OR = 2.28, 95%CI = 1.19-4.36). BD patients had significantly higher level of IL-6 (P < 0.001) and significantly lower level of IL-10 (P < 0.001) compared to controls. The changes in the level of cytokines were independent of any genotype of IL-6 or any genotype/haplotype of IL-10. Patients with active disease state had significantly higher level of IL-6 compared to patients in remission (P < 0.05). In conclusion, our preliminary study indicates that the polymorphism at IL-10 -1082 G/A may play a role in BD susceptibility. The significant increase in IL-6 level and the significant decrease in IL-10 level in BD patients were independent of any particular genotype in IL-6 or any particular genotype/haplotype in IL-10. © 2014 Elsevier GmbH.

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