PARP-1 and its associated nucleases in DNA damage response

BackgroundGlioblastomas treated with temozolomide frequently develop resistance to pharmacological treatments. Therefore, there is a need to find alternative drug targets to reduce treatment resistance based on tumor dependencies. A possibility is to target simultaneously two proteins from different DNA-damage repair pathways to facilitate tumor cell death. Therefore, we tested whether targeting the human chromatin kinase VRK1 by RNA interference can identify this protein as a novel molecular target to reduce the dependence on temozolomide in combination with olaparib, based on synthetic lethality.Materials and MethodsDepletion of VRK1, an enzyme that regulates chromatin dynamic reorganization and facilitates resistance to DNA damage, was performed in glioblastoma cells treated with temozolomide, an alkylating agent used for GBM treatment; and olaparib, an inhibitor of PARP-1, used as sensitizer. Two genetically different human glioblastoma cell lines, LN-18 and LN-229, were used for these experiments. The effect on the DNA-damage response was followed by determination of sequential steps in this process: H4K16ac, γH2AX, H4K20me2, and 53BP1.ResultsThe combination of temozolomide and olaparib increased DNA damage detected by labeling free DNA ends, and chromatin relaxation detected by H4K16ac. The combination of both drugs, at lower doses, resulted in an increase in the DNA damage response detected by the formation of γH2AX and 53BP1 foci. VRK1 depletion did not prevent the generation of DNA damage in TUNEL assays, but significantly impaired the DNA damage response induced by temozolomide and olaparib, and mediated by γH2AX, H4K20me2, and 53BP1. The combination of these drugs in VRK1 depleted cells resulted in an increase of glioblastoma cell death detected by annexin V and the processing of PARP-1 and caspase-3.ConclusionDepletion of the chromatin kinase VRK1 promotes tumor cell death at lower doses of a combination of temozolomide and olaparib treatments, and can be a novel alternative target for therapies based on synthetic lethality.

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Abstract LB-086: PARP-1 controls the DNA damage response by regulating E2F1 transcriptional activity

10.1158/1538-7445.am2017-lb-086 ◽

2017 ◽

Author(s):

Matthew J. Schiewer ◽

Amy C. Mandigo ◽

Nicolas Gordon ◽

Fangjin Huang ◽

Sanchaika Gaur ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Transcriptional Activity ◽

Damage Response ◽

Parp 1

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PARP-1 modifies the effectiveness of p53-mediated DNA damage response

Oncogene ◽

10.1038/sj.onc.1205169 ◽

2002 ◽

Vol 21 (7) ◽

pp. 1108-1116 ◽

Cited By ~ 80

Author(s):

M Teresa Valenzuela ◽

Rosario Guerrero ◽

M Isabel Núñez ◽

J Mariano Ruiz de Almodóvar ◽

Malabika Sarker ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Damage Response ◽

Parp 1

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Targeting DNA Damage Response in Prostate and Breast Cancer

International Journal of Molecular Sciences ◽

10.3390/ijms21218273 ◽

2020 ◽

Vol 21 (21) ◽

pp. 8273

Author(s):

Antje M. Wengner ◽

Arne Scholz ◽

Bernard Haendler

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Dna Damage Response ◽

Large Scale ◽

Hormone Receptors ◽

Steroid Hormone ◽

Steroid Hormone Receptors ◽

Genome Integrity ◽

Damage Response ◽

Parp 1

Steroid hormone signaling induces vast gene expression programs which necessitate the local formation of transcription factories at regulatory regions and large-scale alterations of the genome architecture to allow communication among distantly related cis-acting regions. This involves major stress at the genomic DNA level. Transcriptionally active regions are generally instable and prone to breakage due to the torsional stress and local depletion of nucleosomes that make DNA more accessible to damaging agents. A dedicated DNA damage response (DDR) is therefore essential to maintain genome integrity at these exposed regions. The DDR is a complex network involving DNA damage sensor proteins, such as the poly(ADP-ribose) polymerase 1 (PARP-1), the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the ataxia–telangiectasia-mutated (ATM) kinase and the ATM and Rad3-related (ATR) kinase, as central regulators. The tight interplay between the DDR and steroid hormone receptors has been unraveled recently. Several DNA repair factors interact with the androgen and estrogen receptors and support their transcriptional functions. Conversely, both receptors directly control the expression of agents involved in the DDR. Impaired DDR is also exploited by tumors to acquire advantageous mutations. Cancer cells often harbor germline or somatic alterations in DDR genes, and their association with disease outcome and treatment response led to intensive efforts towards identifying selective inhibitors targeting the major players in this process. The PARP-1 inhibitors are now approved for ovarian, breast, and prostate cancer with specific genomic alterations. Additional DDR-targeting agents are being evaluated in clinical studies either as single agents or in combination with treatments eliciting DNA damage (e.g., radiation therapy, including targeted radiotherapy, and chemotherapy) or addressing targets involved in maintenance of genome integrity. Recent preclinical and clinical findings made in addressing DNA repair dysfunction in hormone-dependent and -independent prostate and breast tumors are presented. Importantly, the combination of anti-hormonal therapy with DDR inhibition or with radiation has the potential to enhance efficacy but still needs further investigation.

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