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Cindy R Timme, Barbara H Rath, John W O'Neill, Kevin Camphausen, Philip J Tofilon
Radiotherapy is a primary treatment modality for glioblastomas (GBMs). Because DNA-PKcs is a critical factor in the repair of radiation-induced double strand breaks (DSBs), this study evaluated the potential of VX-984, a new DNA-PKcs inhibitor, to enhance the radiosensitivity of GBM cells. Treatment of the established GBM cell line U251 and the GBM stem-like cell (GSC) line NSC11 with VX-984 under in vitro conditions resulted in a concentration-dependent inhibition of radiation-induced DNA-PKcs phosphorylation...
March 16, 2018: Molecular Cancer Therapeutics
Katsunori Sugimoto
Phosphatidylinositol 3-kinase-related kinases (PIKKs), are structurally related to phosphatidylinositol 3-kinase (lipid kinase), but possess protein kinase activities. PIKKs include ATM, ATR, DNA-PK, mTOR and SMG1, key regulators of cell proliferation and genome maintenance. TRRAP, which is devoid of protein kinase activity, is the sixth member of the PIKK family. PIKK family members are gigantic proteins in the range of 300-500 kDa. It has become apparent in the last decade that the stability or maturation of the PIKK family members depends on a molecular chaperone called the Tel2-Tti1-Tti2 (TTT) complex...
February 22, 2018: Current Genetics
Laura J Eccles, Andrew C Bell, Simon N Powell
When Fanconi Anemia (FA) proteins were depleted in human U2OS cells with integrated DNA repair reporters, we observed decreases in homologous recombination (HR), decreases in mutagenic non-homologous end joining (m-NHEJ) and increases in canonical NHEJ, which was independently confirmed by measuring V(D)J recombination. Furthermore, depletion of FA proteins resulted in reduced HR protein foci and increased NHEJ protein recruitment to replication-associated DSBs, consistent with our observation that the use of canonical NHEJ increases after depletion of FA proteins in cycling cells...
February 10, 2018: DNA Repair
Jay H Chung
DNA-dependent protein kinase (DNA-PK) is a very large holoenzyme comprised of the p470 kDa DNA-PK catalytic subunit (DNA-PKcs ) and the Ku heterodimer consisting of the p86 (Ku 80) and p70 (Ku 70) subunits. It is best known for its non-homologous end joining (NHEJ) activity, which repairs double-strand DNA (dsDNA) breaks (DSBs). As expected, the absence of DNA-PK activity results in sensitivity to ionizing radiation, which generates DSBs and defect in lymphocyte development, which requires NHEJ of the V(D)J region in the immunoglobulin and T cell receptor loci...
February 17, 2018: FEBS Journal
Minoru Hatayama, Jun Aruga
Proper functions of Zic proteins are essential for animals in health and disease. Here, we summarize our current understanding of the molecular properties and functions of the Zic family across animal species and paralog subtypes. Zics are basic proteins with some posttranslational modifications and can move to the cell nucleus via importin- and CRM1-based nucleocytoplasmic shuttling mechanisms. Degradation is mediated by the ubiquitin proteasome system. Many Zic proteins are capable of binding to two types of target DNA sequences (CTGCTG-core-type and GC-stretch-type)...
2018: Advances in Experimental Medicine and Biology
Yanling Wang, Haineng Xu, Tianrun Liu, Menggui Huang, Param-Puneet Butter, Chunsheng Li, Lin Zhang, Gary D Kao, Yanqing Gong, Amit Maity, Constantinos Koumenis, Yi Fan
Cancer stem cells (CSCs) - known to be resistant to genotoxic radiation and chemotherapy - are fundamental to therapy failure and cancer relapse. Here, we reveal that glioma CSCs are hypersensitive to radiation, but a temporal DNA repair mechanism converts the intrinsic sensitivity to genomic instability and treatment resistance. Transcriptome analysis identifies DNA-dependent protein kinase (DNA-PK) as a predominant DNA repair enzyme in CSCs. Notably, DNA-PK activity is suppressed after irradiation when ROS induce the dissociation of DNA-PKcs with Ku70/80, resulting in delayed DNA repair and radiosensitivity; subsequently, after ROS clearance, the accumulated DNA damage and robust activation of DNA-PK induce genomic instability, facilitated by Rad50-mediated cell-cycle arrest, leading to enhanced malignancy, CSC overgrowth, and radioresistance...
February 8, 2018: JCI Insight
Britta Vormoor, Yvonne T Schlosser, Helen Blair, Abhishek Sharma, Sarah Wilkinson, David R Newell, Nicola Curtin
Background: DNA-PK and PARP inhibitors sensitize cancer cells to chemo- and radiotherapy. ETS transcription factors (EWS-FLI1) have been described as biomarkers for PARP-inhibitor sensitivity. Sensitivity to single agent PARP inhibitors has so far been limited to homologous recombination repair (HRR) deficient tumors, exploiting synthetic lethality. Results: In clonogenic assays, single agent rucaparib LD50 values for continuously exposed cells were similar to those observed in HRR-defective cells (CAPAN-1 cell line, BRCA2 defective); however, both ES cell lines (TC-71, CADO-ES1) had functional HRR...
December 26, 2017: Oncotarget
Jun Dong, Yufeng Ren, Tian Zhang, Zhenyu Wang, Clifton C Ling, Gloria C Li, Fuqiu He, Chengtao Wang, Bixiu Wen
The DNA-dependent protein kinase (DNA-PK) complex plays a pivotal role in non-homologous end-joining (NHEJ) repair. We investigated the mechanism of NU7441, a highly selective DNA-PK inhibitor, in NHEJ-competent mouse embryonic fibroblast (MEF) cells and NHEJ-deficient cells and explored the feasibility of its application in radiosensitizing nasopharyngeal carcinoma (NPC) cells. We generated wild-type and DNA-PKcs-/- MEF cells. Clonogenic survival assays, flow cytometry, and immunoblotting were performed to study the effect of NU7441 on survival, cell cycle, and DNA repair...
March 2018: Oncology Reports
Carmen Klein, Ivana Dokic, Andrea Mairani, Stewart Mein, Stephan Brons, Peter Häring, Thomas Haberer, Oliver Jäkel, Astrid Zimmermann, Frank Zenke, Andree Blaukat, Jürgen Debus, Amir Abdollahi
BACKGROUND: Hypoxia-induced radioresistance constitutes a major obstacle for a curative treatment of cancer. The aim of this study was to investigate effects of photon and carbon ion irradiation in combination with inhibitors of DNA-Damage Response (DDR) on tumor cell radiosensitivity under hypoxic conditions. METHODS: Human non-small cell lung cancer (NSCLC) models, A549 and H1437, were irradiated with dose series of photon and carbon ions under hypoxia (1% O2) vs...
December 29, 2017: Radiation Oncology
Yang Yu, Liqi Qian, Nan Du, Yuxiao Liu, Xiao Zhao, Xin Zhang
Ganoderma lucidum polysaccharide (GLP) is a well-known traditional Chinese medicine, known for its anti-cancer and immunomodulatory properties. The present study aims to investigate whether GLP has a therapeutic effect on hepatocellular carcinoma (HCC) cells exposed to radiation. Immunofluorescence was used to detect the nuclei, the protein expression was measured by western blot analysis and flow cytometry was used to detect the rate of cell apoptosis. GLP treatment was demonstrated to enhance radiation-induced growth inhibition and apoptotic death of HCC cells...
December 2017: Experimental and Therapeutic Medicine
Jozsef Gal, Jing Chen, Yuriko Katsumata, David W Fardo, Wang-Xia Wang, Sergey Artiushin, Douglas Price, Sonya Anderson, Ela Patel, Haining Zhu, Peter T Nelson
Misfolded protein in the amygdala is a neuropathologic feature of Alzheimer disease and many other neurodegenerative disorders. We examined extracts from human amygdala (snap-frozen at autopsy) to investigate whether novel and as yet uncharacterized misfolded proteins would be detectable. Polypeptides from the detergent-insoluble, urea-soluble protein fractions of amygdala were interrogated using liquid chromatography-electrospray ionization-tandem mass spectrometry. Among the detergent-insoluble proteins identified in amygdala of demented subjects but not controls were Tau, TDP-43, Aβ, α-synuclein, and ApoE...
January 1, 2018: Journal of Neuropathology and Experimental Neurology
Polly Gravells, James Neale, Emma Grant, Amit Nathubhai, Kate M Smith, Dominic I James, Helen E Bryant
Upon DNA binding the poly(ADP-ribose) polymerase family of enzymes (PARPs) add multiple ADP-ribose subunits to themselves and other acceptor proteins. Inhibitors of PARPs have become an exciting and real prospect for monotherapy and as sensitizers to ionising radiation (IR). The action of PARPs are reversed by poly(ADP-ribose) glycohydrolase (PARG). Until recently studies of PARG have been limited by the lack of an inhibitor. Here, a first in class, specific, and cell permeable PARG inhibitor, PDD00017273, is shown to radiosensitize...
January 2018: DNA Repair
Xin Long, Robert B Gerbing, Todd A Alonzo, Michele S Redell
Despite aggressive chemotherapy including mitoxantrone and etoposide, relapse occurs for almost half of children with acute myeloid leukemia (AML). Since both drugs inhibit topoisomerase II and cause DNA double strand breaks, resistance could be achieved by enhanced DNA damage repair (DDR), via homologous recombination (HR) and/or non-homologous end joining (NHEJ). An important source of extrinsic chemoresistance is the bone marrow stroma. We aimed to reveal intrinsic and stroma-induced signaling pathways that contribute to chemoresistance...
October 27, 2017: Oncotarget
M H Yashavarddhan, Sandeep K Shukla, Pankaj Chaudhary, Nitya N Srivastava, Jayadev Joshi, Mrutyunjay Suar, Manju L Gupta
Drug discovery field has tremendously progressed during last few decades, however, an effective radiation countermeasure agent for the safe administration to the victims of radiation exposure is still unavailable. This multi-model study is aimed at elucidating the mechanistic aspects of a novel podophyllotoxin and rutin combination (henceforth referred as G-003M) in the hematopoietic radioprotection and its involvement in the DNA damage and repair signaling pathways. Using in silico study, we identified the binding sites and structural components of G-003M and validated in vitro ...
2017: Frontiers in Pharmacology
Jie Zhang, Grace Shim, Sonia M de Toledo, Edouard I Azzam
The absorption of ionizing radiation by living cells can directly disrupt atomic structures, producing chemical and biological changes. It can also act indirectly through radiolysis of water, thereby generating reactive chemical species that may damage nucleic acids, proteins, and lipids. Together, the direct and indirect effects of radiation initiate a series of biochemical and molecular signaling events that may repair the damage or culminate in permanent physiological changes or cell death. In efforts to gain insight into the mechanisms underlying these effects, we observed a prominent upregulation of the Translationally Controlled Tumor Protein (TCTP) in low dose/low dose rate (137)Cs γ-irradiated cells that was associated with adaptive responses that reduced chromosomal damage to a level lower than what occurs spontaneously...
2017: Results and Problems in Cell Differentiation
Pok Man Hau, Sai Wah Tsao
The Epstein-Barr virus (EBV) is a ubiquitous virus that infects most of the human population. EBV infection is associated with multiple human cancers, including Burkitt's lymphoma, Hodgkin's lymphoma, a subset of gastric carcinomas, and almost all undifferentiated non-keratinizing nasopharyngeal carcinoma. Intensive research has shown that EBV triggers a DNA damage response (DDR) during primary infection and lytic reactivation. The EBV-encoded viral proteins have been implicated in deregulating the DDR signaling pathways...
November 16, 2017: Viruses
Kalnisha Naidoo, Patty T Wai, Sarah L Maguire, Frances Daley, Syed Haider, Divya Kriplani, James Campbell, Hasan Mirza, Anita Grigoriadis, Andrew Tutt, Paul M Moseley, Tarek M A Abdel-Fatah, Stephen Yt Chan, Srinivasan Madhusudan, Emad A Rakha, Ian O Ellis, Christopher J Lord, Yinyin Yuan, Andrew R Green, Rachael Natrajan
Disruption of Cyclin Dependent Kinase 12 (CDK12) is known to lead to defects in DNA repair and sensitivity to platinum salts and poly(ADP-ribose) polymerase 1/2 inhibitors. However, CDK12 has also been proposed as an oncogene in breast cancer. We therefore aimed to assess the frequency and distribution of CDK12 protein expression by immunohistochemistry (IHC) in independent cohorts of breast cancer and correlate this with outcome and genomic status. We found that 21% of primary unselected breast cancers were CDK12 high, and 10...
November 13, 2017: Molecular Cancer Therapeutics
Hongzhi Zhang, Huijuan Jiang, Lei Chen, Juncai Liu, Xigang Hu, Huixiang Zhang
Notch signaling pathway has been demonstrated to mediate radioresistance of several tumors. Our study aims to explore the function of Notch1/HES1 pathway in the radioresistance of colorectal cancer (CRC). The results demonstrated that expressions of Notch1 and Hes1 were up-regulated with the increasing irradiation dose. DAPT (N-[(3,5-difluorophenacetyl)acety1]-L-alanyl-2-phenyl]glycine-1,1-dimethylethyl ester) or si-Notch1 reduced expressions of Notch1 and Hes1, exacerbated irradiation-induced cell proliferation inhibition, and improved radiosensitivity of CRC cells...
January 5, 2018: European Journal of Pharmacology
David G Kirsch, Max Diehn, Aparna H Kesarwala, Amit Maity, Meredith A Morgan, Julie K Schwarz, Robert Bristow, Sandra Demaria, Iris Eke, Robert J Griffin, Daphne Haas-Kogan, Geoff S Higgins, Alec C Kimmelman, Randall J Kimple, Isabelle M Lombaert, Li Ma, Brian Marples, Frank Pajonk, Catherine C Park, Dörthe Schaue, Eric J Bernhard
Innovation and progress in radiation oncology depend on discovery and insights realized through research in radiation biology. Radiobiology research has led to fundamental scientific insights, from the discovery of stem/progenitor cells to the definition of signal transduction pathways activated by ionizing radiation that are now recognized as integral to the DNA damage response (DDR). Radiobiological discoveries are guiding clinical trials that test radiation therapy combined with inhibitors of the DDR kinases DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM), ataxia telangiectasia related (ATR), and immune or cell cycle checkpoint inhibitors...
November 3, 2017: Journal of the National Cancer Institute
Mary Glorieux, Rüveyda Dok, Sandra Nuyts
Head and neck squamous cell carcinoma is the sixth most common cancer worldwide and despite advances in treatment over the last years, there is still a relapse rate of 50%. New therapeutic agents are awaited to increase the survival of patients. DNA repair targeted agents in combination with standard DNA damaging therapies are a recent evolution in cancer treatment. These agents focus on the DNA damage repair pathways in cancer cells, which are often involved in therapeutic resistance. Interesting targets to overcome these cancer defense mechanisms are: PARP, DNA-PK, PI3K, ATM, ATR, CHK1/2, and WEE1 inhibitors...
October 6, 2017: Oncotarget
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