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Xuanxuan Wang, Yanjun Gu, Hai Liu, Liming Shi, Xiaonan Sun
Background: Radiotherapy and cisplatin-based chemotherapy are currently considered as standard treatments employed for advanced cervical cancer (CC). However, patients with local recurrence or distant metastasis continue to have poor outcomes. EGFR overexpression correlated with chemo/radioresistance, and disease failure has been well proved in the previous studies. Hence, the aim of this study was to explore the therapeutic efficacy and underlying mechanism of the sensitization to radiation or cisplatin of icotinib hydrochloride (IH), a high-selective EGFR tyrosine kinase inhibitor (TKI), in the Hela S3 human CC cell line...
2018: OncoTargets and Therapy
Yu Chen, Zhen Li, Zhu Xu, Huanyin Tang, Wenxuan Guo, Xiaoxiang Sun, Wenjun Zhang, Jian Zhang, Xiaoping Wan, Ying Jiang, Zhiyong Mao
The homologous recombination (HR) pathway is a promising target for cancer therapy as it is frequently upregulated in tumors. One such strategy is to target tumors with cancer-specific, hyperactive promoters of HR genes including RAD51 and RAD51C. However, the promoter size and the delivery method have limited its potential clinical applications. Here we identified the ~2.1 kb promoter of XRCC2, similar to ~6.5 kb RAD51 promoter, as also hyperactivated in cancer cells. We found that XRCC2 expression is upregulated in nearly all types of cancers, to a degree comparable to RAD51 while much higher than RAD51C...
March 16, 2018: Cell Death & Disease
Francesca Vena, Ruochen Jia, Arman Esfandiari, Juan J Garcia-Gomez, Manuel Rodriguez-Justo, Jianguo Ma, Sakeena Syed, Lindsey Crowley, Brian Elenbaas, Samantha Goodstal, John A Hartley, Daniel Hochhauser
Targeting the DNA damage response (DDR) in tumors with defective DNA repair is a clinically successful strategy. The RAS/RAF/MEK/ERK signalling pathway is frequently deregulated in human cancers. In this study, we explored the effects of MEK inhibition on the homologous recombination pathway and explored the potential for combination therapy of MEK inhibitors with DDR inhibitors and a hypoxia-activated prodrug. We studied effects of combining pimasertib, a selective allosteric inhibitor of MEK1/2, with olaparib, a small molecule inhibitor of poly (adenosine diphosphate [ADP]-ribose) polymerases (PARP), and with the hypoxia-activated prodrug evofosfamide in ovarian and pancreatic cancer cell lines...
February 20, 2018: Oncotarget
Pingping Fang, Jill A Madden, Lisa Neums, K Ryan Moulder, M Laird Forrest, Jeremy Chien
FOXM1 transcription factor network is activated in over 84% of cases in high-grade serous ovarian cancer (HGSOC), and FOXM1 upregulates the expression of genes involved in the homologous recombination (HR) DNA damage and repair (DDR) pathway. However, the role of FOXM1 in poly (ADP-ribose) polymerase (PARP) inhibitor response has not yet been studied. The present study demonstrates that PARP inhibitor (PARPi), olaparib, induces the expression and nuclear localization of FOXM1. Based on ChIP-qPCR, olaparib enhances the binding of FOXM1 to genes involved in HR repair...
March 15, 2018: Molecular Cancer Research: MCR
Jun Huang, Hong-Liang Luo, Hua Pan, Cheng Qiu, Teng-Fei Hao, Zheng-Ming Zhu
Colon cancer remains one of the most common digestive system malignancies in the World. This study investigated the possible interaction between RAD51 and minichromosome maintenance proteins (MCMs) in HCT116 cells, which can serve as a model system for forming colon cancer foci. The interaction between RAD51 and MCMs was detected by mass spectrometry. Silenced MCM vectors were transfected into HTC116 cells. The expressions of RAD51 and MCMs were detected using Western blotting. Foci forming and chromatin fraction of RAD51 in HCT116 cells were also analyzed...
January 2018: Biochemistry. Biokhimii︠a︡
Alex Bronstein, Shay Bramson, Keren Shemesh, Batia Liefshitz, Martin Kupiec
Proper DNA damage repair is one of the most vital and fundamental functions of every cell. Several different repair mechanisms exist to deal with various types of DNA damage, in various stages of the cell cycle and under different conditions. Homologous recombination is one of the most important repair mechanisms in all organisms. Srs2, a regulator of homologous recombination, is a DNA helicase involved in DNA repair, cell cycle progression and genome integrity. Srs2 can remove Rad51 from ssDNA, and is thought to inhibit unscheduled recombination...
March 12, 2018: G3: Genes—Genomes—Genetics
Luther Davis, Yinbo Zhang, Nancy Maizels
Nicks are the most common form of DNA damage, but they have only recently been shown to initiate damage that requires repair. Analysis of the pathways of nick repair in human cells has benefited from the development of enzymes that target nicks to specific sites in the genome and of reporters that enable rapid analysis of homology-directed repair and mutagenic end joining. Nicks undergo efficient repair by single-stranded oligonucleotide donors complementary to either the nicked or intact DNA strand, via pathways that are normally suppressed by RAD51...
2018: Methods in Enzymology
Ke Li, Huaying Yan, Wenhao Guo, Mei Tang, Xinyu Zhao, Aiping Tong, Yong Peng, Qintong Li, Zhu Yuan
PTEN deficiency often causes defects in DNA damage repair. Currently, effective therapies for breast cancer are lacking. ATM is an attractive target for cancer treatment. Previous studies suggested a synthetic lethality between PTEN and PARP. However, the synthetically lethal interaction between PTEN and ATM in breast cancer has not been reported. Moreover, the mechanism remains elusive. Here, using KU-60019, an ATM kinase inhibitor, we investigated ATM inhibition as a synthetically lethal strategy to target breast cancer cells with PTEN defects...
March 6, 2018: Experimental Cell Research
T Maués, K B El-Jaick, F B Costa, G E F Araujo, M V G Soares, A S Moreira, M L G Ferreira, A M R Ferreira
The canine BRCA2 is a tumor supressor gene which encodes the BRCA2 protein, involved in DNA repair through interaction with the RAD51 recombinase. This process is mediated by eigth BRC repeats that are encoded by BRCA2 exon 11. Two variants corresponding to human mutations in human BRC3 repeat have been reported in canine BRC3 repeat. In addition, other variants have also been described in canine BRCA2 exon 11. Considering the importance of polymorphisms in human BRCA2 to breast cancer development, this study aimed to investigate the frequency of variants in BRCA2 exon 11 in 48 blood and tissue DNA samples from bitches with canine mammary tumors (CMT), as well as, to analyze tumor stage and histopathological features...
March 6, 2018: Veterinary and Comparative Oncology
Qi Liu, Liliana Gheorghiu, Michael Drumm, Rebecca Clayman, Alec Eidelman, Matthew F Wszolek, Aria Olumi, Adam Feldman, Meng Wang, Lynnette Marcar, Deborah E Citrin, Chin-Lee Wu, Cyril H Benes, Jason A Efstathiou, Henning Willers
Biomarkers and mechanisms of poly (ADP-ribose) polymerase (PARP) inhibitor-mediated cytotoxicity in tumor cells lacking a BRCA-mutant or BRCA-like phenotype are poorly defined. We sought to explore the utility of PARP-1 inhibitor (PARPi) treatment with/without ionizing radiation in muscle-invasive bladder cancer (MIBC), which has poor therapeutic outcomes. We assessed the DNA damaging and cytotoxic effects of the PARPi olaparib in nine bladder cancer cell lines. Olaparib radiosensitized all cell lines with dose enhancement factors from 1...
March 7, 2018: Oncogene
Hongjian Gong, Yuxi Zhang, Kunpeng Jiang, Shengfan Ye, Shuming Chen, Qinghe Zhang, Jinrong Peng, Jun Chen
Tumour repressor p53 isoform Δ133p53 is a target gene of p53 and an antagonist of p53-mediated apoptotic activity. We recently demonstrated that Δ133p53 promotes DNA double-strand break (DSB) repair by upregulating transcription of the repair genes RAD51, LIG4 and RAD52 in a p53-independent manner. However, Δ133p53 lacks the transactivation domain of full-length p53, and the mechanism by which it exerts transcriptional activity independently of full-length p53 remains unclear. In this report, we describe the accumulation of high levels of both Δ133p53 and p73 (a p53 family member) at 24 h post γ-irradiation (hpi)...
March 6, 2018: Cell Death and Differentiation
Ineke Brouwer, Tommaso Moschetti, Andrea Candelli, Edwige B Garcin, Mauro Modesti, Luca Pellegrini, Gijs Jl Wuite, Erwin Jg Peterman
An essential mechanism for repairing DNA double-strand breaks is homologous recombination (HR). One of its core catalysts is human RAD51 (hRAD51), which assembles as a helical nucleoprotein filament on single-stranded DNA, promoting DNA-strand exchange. Here, we study the interaction of hRAD51 with single-stranded DNA using a single-molecule approach. We show that ATP-bound hRAD51 filaments can exist in two different states with different contour lengths and with a free-energy difference of ~4 kB T per hRAD51 monomer...
March 5, 2018: EMBO Journal
Eui-Hwan Choi, Seobin Yoon, Keun P Kim
Homologous recombination (HR), which ensures accurate DNA replication and strand-break repair, is necessary to preserve embryonic stem cell (ESC) self-renewal. However, little is known about how HR factors modulate ESC differentiation and replication stress-associated DNA breaks caused by unique cell-cycle progression. Here, we report that ESCs utilize Rad51-dependent HR to enhance viability and induce rapid proliferation through a replication-coupled pathway. In addition, ESC differentiation was shown to be enhanced by ectopic expression of a subset of recombinases...
February 8, 2018: Molecular Therapy: the Journal of the American Society of Gene Therapy
W Y Mansour, P Tennstedt, J Volquardsen, C Oing, M Kluth, C Hube-Magg, K Borgmann, R Simon, C Petersen, E Dikomey, K Rothkamm
Here we report that PTEN contributes to DNA double-strand break (DSB) repair via homologous recombination (HR), as evidenced by (i) inhibition of HR in a reporter plasmid assay, (ii) enhanced sensitivity to mitomycin-C or olaparib and (iii) reduced RAD51 loading at IR-induced DSBs upon PTEN knockdown. No association was observed between PTEN-status and RAD51 expression either in-vitro or in-vivo in a tissue microarray of 1500 PTEN-deficient prostate cancer (PC) samples. PTEN depletion and sustained activation of AKT sequestered CHK1 in the cytoplasm, thus impairing the G2/M-checkpoint after irradiation...
March 2, 2018: Scientific Reports
Cristina Maranto, Vindhya Udhane, David T Hoang, Lei Gu, Vitali Alexeev, Kareem M Malas, Karmel Cardenas, Jonathan R Brody, Ulrich Rodeck, Carmen Bergom, Kenneth A Iczkowski, Kenneth Jacobsohn, William A See, Sara M Schmitt, Marja T Nevalainen
PURPOSE: The standard treatment for organ-confined prostate cancer (PC) is surgery or radiation, and locally advanced PC is typically treated with radiotherapy alone or in combination with androgen deprivation therapy. Here, we investigated whether Stat5a/b participates in regulation of double strand DNA break repair in PC, and whether Stat5 inhibition may provide a novel strategy to sensitize PC to radiation therapy. EXPERIMENTAL DESIGN: Stat5a/b regulation of DNA repair in PC was evaluated by comet and clonogenic survival assays, followed by assays specific to Homologous Recombination (HR) DNA repair and Non-Homologous End-Joining (NHEJ) DNA repair...
February 26, 2018: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
Mário Špírek, Jarmila Mlcoušková, Ondrej Belán, Máté Gyimesi, Gábor M Harami, Eszter Molnár, Jiri Novacek, Mihály Kovács, Lumir Krejci
Formation of RAD51 filaments on single-stranded DNA is an essential event during homologous recombination, which is required for homology search, strand exchange and protection of replication forks. Formation of nucleoprotein filaments (NF) is required for development and genomic stability, and its failure is associated with developmental abnormalities and tumorigenesis. Here we describe the structure of the human RAD51 NFs and of its Walker box mutants using electron microscopy. Wild-type RAD51 filaments adopt an 'open' conformation when compared to a 'closed' structure formed by mutants, reflecting alterations in helical pitch...
February 22, 2018: Nucleic Acids Research
Yuan Wang, Weihang Chai
Coats plus syndrome is a complex genetic disorder that can be caused by mutations in genes encoding the CTC1-STN1-TEN1 (CST) complex, a conserved single-stranded DNA binding protein complex. Studies have demonstrated that mutations identified in Coats plus patients are defective in telomere maintenance, and concluded that Coats plus may be caused by telomere dysfunction. Recent studies have established that CST also plays an important role in countering replication stress and protecting the stability of genomic fragile sites...
February 22, 2018: Nucleic Acids Research
Ting-Hsiang Huang, Faith Fowler, Chin-Chuan Chen, Zih-Jie Shen, Barry Sleckman, Jessica K Tyler
The access-repair-restore model for the role of chromatin in DNA repair infers that chromatin is a mere obstacle to DNA repair. However, here we show that blocking chromatin assembly, via knockdown of the histone chaperones ASF1 or CAF-1 or a mutation that prevents ASF1A binding to histones, hinders Rad51 loading onto ssDNA during homologous recombination. This is a consequence of reduced recruitment of the Rad51 loader MMS22L-TONSL to ssDNA, resulting in persistent RPA foci, extensive DNA end resection, persistent activation of the ATR-Chk1 pathway, and cell cycle arrest...
March 1, 2018: Molecular Cell
Anja Göder, Claudia Emmerich, Teodora Nikolova, Nicole Kiweler, Maria Schreiber, Toni Kühl, Diana Imhof, Markus Christmann, Thorsten Heinzel, Günter Schneider, Oliver H Krämer
Checkpoint kinases sense replicative stress to prevent DNA damage. Here we show that the histone deacetylases HDAC1/HDAC2 sustain the phosphorylation of the checkpoint kinases ATM, CHK1 and CHK2, activity of the cell cycle gatekeeper kinases WEE1 and CDK1, and induction of the tumour suppressor p53 in response to stalled DNA replication. Consequently, HDAC inhibition upon replicative stress promotes mitotic catastrophe. Mechanistically, HDAC1 and HDAC2 suppress the expression of PPP2R3A/PR130, a regulatory subunit of the trimeric serine/threonine phosphatase 2 (PP2A)...
February 22, 2018: Nature Communications
George E Ronson, Ann Liza Piberger, Martin R Higgs, Anna L Olsen, Grant S Stewart, Peter J McHugh, Eva Petermann, Nicholas D Lakin
PARP1 regulates the repair of DNA single-strand breaks generated directly, or during base excision repair (BER). However, the role of PARP2 in these and other repair mechanisms is unknown. Here, we report a requirement for PARP2 in stabilising replication forks that encounter BER intermediates through Fbh1-dependent regulation of Rad51. Whereas PARP2 is dispensable for tolerance of cells to SSBs or homologous recombination dysfunction, it is redundant with PARP1 in BER. Therefore, combined disruption of PARP1 and PARP2 leads to defective BER, resulting in elevated levels of replication-associated DNA damage owing to an inability to stabilise Rad51 at damaged replication forks and prevent uncontrolled DNA resection...
February 21, 2018: Nature Communications
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