PARPi in PCa results in decreased availability of DNA repair factors.

2016 ◽  
Vol 34 (2_suppl) ◽  
pp. 301-301
Author(s):  
Matthew Joseph Schiewer ◽  
Karen E. Knudsen
Keyword(s):  
Dna Repair ◽  
Enzymatic Activity ◽  
Disease Progression ◽  
Target Genes ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Clinical Trial Data ◽  
Parp Inhibition ◽  
Transcriptional Regulatory ◽  
Parp 1

301 Background: The first described roles for PARP-1 were in the repair of DNA damage and genomic maintenance, however, recent studies have identified PARP-1 as harboring critical context-dependent transcriptional regulatory functions in cancer, including regulating NFkB and HIF function. Our group recently discovered that PARP-1 enzymatic activity is a critical effector of AR function PCa, and assists in regulating AR-driven, PCa-associated phenotypes, including castrate-resistant AR function, tumor growth, and transition to CRPC. Additionally, recent clinical trial data of PARP inhibition as a single agent in advanced cancers has been promising. Given the preclinical and clinical data, pursuing a deeper understanding of the molecular underpinnings of PARP inhibitor action in PCa may yield markers of response and/or rationale for precision medicine. Methods: Hormone therapy-sensitive and CRPC models were transcriptionally profiled in response to PARP inhibition. Pathways were nominated for validation. Bioinformatics approaches were used to compare the PARP-1-sensitive transcritome with publicly available data sets. ChIP-qPCR was performed to examine the effect of PARPi on target genes of the nominated pathways. Patient specimen TMAs were utilized for PAR IHC. PARP inhibition reduced AR and E2F1 target gene expression, as well as significantly decreased expression of DNA repair genes. Both PARP enzymatic activity and the PARP-1-dependent transcriptional program are increased as a function of disease progression. Results: These data indicate that:(1) The PARPi-sensitive transcriptome holds major transcriptional regulatory events beyond AR signaling. (2) E2F1-regulated genes are sensitive to PARP-1 function. (3) The PARPi-sensitive E2F-regulated transcriptome is enriched for DNA repair factors. (4) PARP enzymatic and transcriptional functions are increased during disease progression. Conclusions: Taken together, this study demonstrates that the transcriptional roles of PARP-1 may contribute to the clinical response to PARP-1 inhibitors as single agents. This work was supported by a PCF YI award (to MJS).

scholarly journals Veliparib Is an Effective Radiosensitizing Agent in a Preclinical Model of Medulloblastoma

2021 ◽  
Vol 8 ◽  
Author(s):  
Jessica Buck ◽  
Patrick J. C. Dyer ◽  
Hilary Hii ◽  
Brooke Carline ◽  
Mani Kuchibhotla ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Combination Therapy ◽  
Cellular Response ◽  
Molecular Subtype ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibition ◽  
Preclinical Model ◽  
Radiation Induced

Medulloblastoma is the most common malignant childhood brain tumor, and 5-year overall survival rates are as low as 40% depending on molecular subtype, with new therapies critically important. As radiotherapy and chemotherapy act through the induction of DNA damage, the sensitization of cancer cells through the inhibition of DNA damage repair pathways is a potential therapeutic strategy. The poly-(ADP-ribose) polymerase (PARP) inhibitor veliparib was assessed for its ability to augment the cellular response to radiation-induced DNA damage in human medulloblastoma cells. DNA repair following irradiation was assessed using the alkaline comet assay, with veliparib inhibiting the rate of DNA repair. Veliparib treatment also increased the number of γH2AX foci in cells treated with radiation, and analysis of downstream pathways indicated persistent activation of the DNA damage response pathway. Clonogenicity assays demonstrated that veliparib effectively inhibited the colony-forming capacity of medulloblastoma cells, both as a single agent and in combination with irradiation. These data were then validated in vivo using an orthotopic implant model of medulloblastoma. Mice harboring intracranial D425 medulloblastoma xenografts were treated with vehicle, veliparib, 18 Gy multifractionated craniospinal irradiation (CSI), or veliparib combined with 18 Gy CSI. Animals treated with combination therapy exhibited reduced tumor growth rates concomitant with increased intra-tumoral apoptosis observed by immunohistochemistry. Kaplan–Meier analyses revealed a statistically significant increase in survival with combination therapy compared to CSI alone. In summary, PARP inhibition enhanced radiation-induced cytotoxicity of medulloblastoma cells; thus, veliparib or other brain-penetrant PARP inhibitors are potential radiosensitizing agents for the treatment of medulloblastoma.

Effect of inhibition of poly-(ADP ribose) polymerase on gemcitabine and radiation-induced cytotoxicity of pancreatic cancer cells.

2011 ◽  
Vol 29 (4_suppl) ◽  
pp. 203-203
Author(s):  
R. Tuli ◽  
A. Surmak ◽  
A. Blackford ◽  
A. Leubner ◽  
E. M. Jaffee ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cell Death ◽  
Dna Repair ◽  
Cancer Cells ◽  
Parp Inhibitor ◽  
Parp Inhibition ◽  
Pancreatic Cancer Cells ◽  
Synergistic Mechanism ◽  
Radiation Induced ◽  
Parp 1

203 Background: Poly-(ADP ribose) polymerases (PARPs) are DNA-binding proteins involved in DNA repair. PARP inhibition has resulted in excellent antitumor activity when used with other cytotoxic therapies. ABT-888 is a promising PARP inhibitor with excellent potency against the PARP-1/2 enzymes and good oral bioavailability. We attempt to determine whether PARP-1/2 inhibition alone, or in combination with gemcitabine, will enhance the effects of irradiation (RT) of pancreatic cancer cells. Methods: The pancreatic carcinoma cell lines, MiaPaCa-2 and Panc02, were treated with ABT-888, gemcitabine, RT, or combinations thereof. RT was delivered with a 137-Cs Gammacell in a single fraction. Cells were pre-treated once with ABT-888 and/or gemcitabine 30 minutes prior to RT. Viability was assessed through reduction of resazurin into fluorescent resorufin. Levels of apoptosis were determined by measuring caspase-3/7 activity using a luminescent assay. PARP activity was determined using a chemiluminescent PAR elisa. Results: The half maximal inhibitory concentration (IC50) of RT was 5 Gy; IC10 for ABT-888 and gemcitabine were 10 uM and 5 nM, respectively. Treatment with ABT-888 (10 uM), gemcitabine (5 nM), or combinations of the two with RT led to increasingly higher rates of cell death 8 days after treatment (p<0.001). RT dose enhancement factors were 1.5, 1.82 and 2.36 for 1, 10 and 100 uM ABT-888, respectively. Minimal cytotoxicity was noted when cells were treated with ABT-888 alone up to 100 uM. Caspase activity was not significantly increased when treated with ABT-888 (10 uM) alone (1.28 fold, p=0.077), but became significant when RT (2 Gy) was added (2.03 fold, p=0.006). This difference was further enhanced by the addition of gemcitabine (2.95 fold, p=0.004). Conclusions: ABT-888 is a potent radiosensitizer of pancreatic cancer cells with minimal cytotoxicity when used alone. Cell death is further potentiated by cotreatment with gemcitabine. Radiation-induced apoptosis was significantly enhanced by ABT-888 and gemcitabine, suggesting a synergistic mechanism of interference with DNA repair. These data are currently being validated in an orthotopic pancreatic cancer mouse model. No significant financial relationships to disclose.

scholarly journals Moving From Poly (ADP-Ribose) Polymerase Inhibition to Targeting DNA Repair and DNA Damage Response in Cancer Therapy

2019 ◽  
Vol 37 (25) ◽  
pp. 2257-2269 ◽  
Author(s):  
Charlie Gourley ◽  
Judith Balmaña ◽  
Jonathan A. Ledermann ◽  
Violeta Serra ◽  
Rebecca Dent ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Damage Response ◽  
Ataxia Telangiectasia ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Effector Proteins ◽  
Parp Inhibition ◽  
Ataxia Telangiectasia Mutated ◽  
Damage Response

The DNA damage response (DDR) pathway coordinates the identification, signaling, and repair of DNA damage caused by endogenous or exogenous factors and regulates cell-cycle progression with DNA repair to minimize DNA damage being permanently passed through cell division. Severe DNA damage that cannot be repaired may trigger apoptosis; as such, the DDR pathway is of crucial importance as a cancer target. Poly (ADP-ribose) polymerase (PARP) is the best-known element of the DDR, and several PARP inhibitors have been licensed. However, there are approximately 450 proteins involved in DDR, and a number of these other targets are being investigated in the laboratory and clinic. We review the most recent evidence for the clinical effect of PARP inhibition in breast and ovarian cancer and explore expansion into the first-line setting and into other tumor types. We critique the evidence for patient selection techniques and summarize what is known about mechanisms of PARP inhibitor resistance. We then discuss what is known about the preclinical rationale for targeting other members of the DDR pathway and the associated tumor cell genetics that may confer sensitivity to these agents. Examples include DNA damage sensors (MLH1), damage signaling molecules (ataxia-telangiectasia mutated; ataxia-telangiectasia mutated–related and Rad3-related; CHK1/2; DNA-dependent protein kinase, catalytic subunit; WEE1; CDC7), or effector proteins for repair (POLQ [also referred to as POLθ], RAD51, poly [ADP-ribose] glycohydrolase). Early-phase clinical trials targeting some of these molecules, either as a single agent or in combination, are discussed. Finally, we outline the challenges that must be addressed to maximize the therapeutic opportunity that targeting DDR provides.

scholarly journals Regulation of Poly(ADP-ribose) Polymerase-1-dependent Gene Expression through Promoter-directed Recruitment of a Nuclear NAD+ Synthase

2012 ◽  
Vol 287 (15) ◽  
pp. 12405-12416 ◽  
Author(s):  
Tong Zhang ◽  
Jhoanna G. Berrocal ◽  
Jie Yao ◽  
Michelle E. DuMond ◽  
Raga Krishnakumar ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Target Gene ◽  
Target Genes ◽  
Enzymatic Activities ◽  
Gene Promoters ◽  
Protein Coding ◽  
Photon Excitation ◽  
Gene Sets ◽  
Cellular Compartments ◽  
Parp 1

NMNAT-1 and PARP-1, two key enzymes in the NAD+ metabolic pathway, localize to the nucleus where integration of their enzymatic activities has the potential to control a variety of nuclear processes. Using a variety of biochemical, molecular, cell-based, and genomic assays, we show that NMNAT-1 and PARP-1 physically and functionally interact at target gene promoters in MCF-7 cells. Specifically, we show that PARP-1 recruits NMNAT-1 to promoters where it produces NAD+ to support PARP-1 catalytic activity, but also enhances the enzymatic activity of PARP-1 independently of NAD+ production. Furthermore, using two-photon excitation microscopy, we show that NMNAT-1 catalyzes the production of NAD+ in a nuclear pool that may be distinct from other cellular compartments. In expression microarray experiments, depletion of NMNAT-1 or PARP-1 alters the expression of about 200 protein-coding genes each, with about 10% overlap between the two gene sets. NMNAT-1 enzymatic activity is required for PARP-1-dependent poly(ADP-ribosyl)ation at the promoters of commonly regulated target genes, as well as the expression of those target genes. Collectively, our studies link the enzymatic activities of NMNAT-1 and PARP-1 to the regulation of a set of common target genes through functional interactions at target gene promoters.

scholarly journals Discovery of 2-(1-(3-(4-Chloroxyphenyl)-3-oxo- propyl)pyrrolidine-3-yl)-1H-benzo[d]imidazole-4-carboxamide: A Potent Poly(ADP-ribose) Polymerase (PARP) Inhibitor for Treatment of Cancer

Molecules ◽  
2019 ◽  
Vol 24 (10) ◽  
pp. 1901 ◽  
Author(s):  
Rui Min ◽  
Weibin Wu ◽  
Mingzhong Wang ◽  
Lin Tang ◽  
Dawei Chen ◽  
...  
Keyword(s):  
Cellular Proliferation ◽  
Parp Inhibitor ◽  
Parp Inhibition ◽  
Anticancer Activities ◽  
Reference Drug ◽  
Structure Activity ◽  
Ic50 Values ◽  
Proliferation Assays ◽  
Parp 1

A series of benzimidazole carboxamide derivatives have been synthesized and characterized by 1H-NMR, 13C-NMR and HRMS. PARP inhibition assays and cellular proliferation assays have also been carried out. Compounds 5cj and 5cp exhibited potential anticancer activities with IC50 values of about 4 nM against both PARP-1 and PARP-2, similar to the reference drug veliparib. The two compounds also displayed slightly better in vitro cytotoxicities against MDA-MB-436 and CAPAN-1 cell lines than veliparib and olaparib, with values of 17.4 µM and 11.4 µM, 19.8 µM and 15.5 µM, respectively. The structure-activity relationship based on molecular docking was discussed as well.

scholarly journals Inhibition of PARP Sensitizes Chondrosarcoma Cell Lines to Chemo- and Radiotherapy Irrespective of the IDH1 or IDH2 Mutation Status

Cancers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1918 ◽  
Author(s):  
Sanne Venneker ◽  
Alwine B. Kruisselbrink ◽  
Inge H. Briaire-de Bruijn ◽  
Yvonne de Jong ◽  
Andre J. van Wijnen ◽  
...  
Keyword(s):  
Dna Repair ◽  
Cell Lines ◽  
Dna Methyltransferase ◽  
Synthetic Lethality ◽  
Parp Inhibitor ◽  
Parp Inhibition ◽  
Idh Mutation ◽  
Mutation Status ◽  
Chondrosarcoma Cell ◽  
Idh Mutations

Chondrosarcomas are chemo- and radiotherapy resistant and frequently harbor mutations in isocitrate dehydrogenase (IDH1 or IDH2), causing increased levels of D-2-hydroxyglutarate (D-2-HG). DNA repair defects and synthetic lethality with poly(ADP-ribose) polymerase (PARP) inhibition occur in IDH mutant glioma and leukemia models. Here we evaluated DNA repair and PARP inhibition, alone or combined with chemo- or radiotherapy, in chondrosarcoma cell lines with or without endogenous IDH mutations. Chondrosarcoma cell lines treated with the PARP inhibitor talazoparib were examined for dose–response relationships, as well as underlying cell death mechanisms and DNA repair functionality. Talazoparib was combined with chemo- or radiotherapy to evaluate potential synergy. Cell lines treated long term with an inhibitor normalizing D-2-HG levels were investigated for synthetic lethality with talazoparib. We report that talazoparib sensitivity was variable and irrespective of IDH mutation status. All cell lines expressed Ataxia Telangiectasia Mutated (ATM), but a subset was impaired in poly(ADP-ribosyl)ation (PARylation) capacity, homologous recombination, and O-6-methylguanine-DNA methyltransferase (MGMT) expression. Talazoparib synergized with temozolomide or radiation, independent of IDH1 mutant inhibition. This study suggests that talazoparib combined with temozolomide or radiation are promising therapeutic strategies for chondrosarcoma, irrespective of IDH mutation status. A subset of chondrosarcomas may be deficient in nonclassical DNA repair pathways, suggesting that PARP inhibitor sensitivity is multifactorial in chondrosarcoma.

scholarly journals Gynecologic Cancers: Emerging Novel Strategies for Targeting DNA Repair Deficiency

2016 ◽  
pp. e259-e268 ◽  
Author(s):  
Rebecca S. Kristeleit ◽  
Rowan E. Miller ◽  
Elise C. Kohn
Keyword(s):  
Ovarian Cancer ◽  
Dna Repair ◽  
Brca Mutation ◽  
Parp Inhibitor ◽  
Inhibitor Therapy ◽  
Molecular Therapy ◽  
Parp Inhibition ◽  
Gynecologic Cancers ◽  
Brca Mutations ◽  
Individual Gene

The presence of a BRCA mutation, somatic or germline, is now established as a standard of care for selecting patients with ovarian cancer for treatment with a PARP inhibitor. During the clinical development of the PARP inhibitor class of agents, a subset of women without BRCA mutations were shown to respond to these drugs (termed “ BRCAness”). It was hypothesized that other genetic abnormalities causing a homologous recombinant deficiency (HRD) were sensitizing the BRCA wild-type cancers to PARP inhibition. The molecular basis for these other causes of HRD are being defined. They include individual gene defects (e.g., RAD51 mutation, CHEK2 mutation), homozygous somatic loss, and whole genome properties such as genomic scarring. Testing this knowledge is possible when selecting patients to receive molecular therapy targeting DNA repair, not only for patients with ovarian cancer but also endometrial and cervical cancers. The validity of HRD assays and multiple gene sequencing panels to select a broader population of patients for treatment with PARP inhibitor therapy is under evaluation. Other non-HRD targets for exploiting DNA repair defects in gynecologic cancers include mismatch repair (MMR), checkpoint signaling, and nonhomologous end-joining (NHEJ) DNA repair. This article describes recent evidence supporting strategies in addition to BRCA mutation for selecting patients for treatment with PARP inhibitor therapy. Additionally, the challenges and opportunities of exploiting DNA repair pathways other than homologous recombination for molecular therapy in gynecologic cancers is discussed.

scholarly journals G-Quadruplex loops regulate PARP-1 enzymatic activation

2020 ◽  
Author(s):  
Andrea D Edwards ◽  
John C Marecki ◽  
Alicia K Byrd ◽  
Jun Gao ◽  
Kevin D Raney
Keyword(s):  
Dna Repair ◽  
Enzymatic Activity ◽  
Regulation Of Transcription ◽  
Dna Structures ◽  
Repair Enzymes ◽  
G Quadruplex ◽  
Associated Proteins ◽  
Enzymatic Activation ◽  
Forming Characteristics ◽  
Parp 1

Abstract G-Quadruplexes are non-B form DNA structures present at regulatory regions in the genome, such as promoters of proto-oncogenes and telomeres. The prominence in such sites suggests G-quadruplexes serve an important regulatory role in the cell. Indeed, oxidized G-quadruplexes found at regulatory sites are regarded as epigenetic elements and are associated with an interlinking of DNA repair and transcription. PARP-1 binds damaged DNA and non-B form DNA, where it covalently modifies repair enzymes or chromatin-associated proteins respectively with poly(ADP-ribose) (PAR). PAR serves as a signal in regulation of transcription, chromatin remodeling, and DNA repair. PARP-1 is known to bind G-quadruplexes with stimulation of enzymatic activity. We show that PARP-1 binds several G-quadruplex structures with nanomolar affinities, but only a subset promote PARP-1 activity. The G-quadruplex forming sequence found in the proto-oncogene c-KIT promoter stimulates enzymatic activity of PARP-1. The loop-forming characteristics of the c-KIT G-quadruplex sequence regulate PARP-1 catalytic activity, whereas eliminating these loop features reduces PARP-1 activity. Oxidized G-quadruplexes that have been suggested to form unique, looped structures stimulate PARP-1 activity. Our results support a functional interaction between PARP-1 and G-quadruplexes. PARP-1 enzymatic activation by G-quadruplexes is dependent on the loop features and the presence of oxidative damage.

scholarly journals PARP Inhibitors in Ovarian Cancer: The Route to “Ithaca”

Diagnostics ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 55 ◽  
Author(s):  
Boussios ◽  
Karathanasi ◽  
Cooke ◽  
Neille ◽  
Sadauskaite ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Brca Mutation ◽  
Parp Inhibitor ◽  
Parp Inhibitors ◽  
Parp Inhibition ◽  
Current Evidence ◽  
Repair Pathway ◽  
Significant Efficacy

Poly (ADP-ribose) polymerase (PARP) inhibitors are a novel class of therapeutic agents that target tumors with deficiencies in the homologous recombination DNA repair pathway. Genomic instability characterizes high-grade serous ovarian cancer (HGSOC), with one half of all tumors displaying defects in the important DNA repair pathway of homologous recombination. Early studies have shown significant efficacy for PARP inhibitors in patients with germline breast related cancer antigens 1 and 2 (BRCA1/2) mutations. It has also become evident that BRCA wild-type patients with other defects in the homologous recombination repair pathway benefit from this treatment. Companion homologous recombination deficiency (HRD) scores are being developed to guide the selection of patients that are most likely to benefit from PARP inhibition. The choice of which PARP inhibitor is mainly based upon the number of prior therapies and the presence of a BRCA mutation or HRD. The identification of patients most likely to benefit from PARP inhibitor therapy in view of HRD and other biomarker assessments is still challenging. The aim of this review is to describe the current evidence for PARP inhibitors in ovarian cancer, their mechanism of action, and the outstanding issues, including the rate of long-term toxicities and the evolution of resistance.

Randomized phase II study of 2nd-line FOLFIRI versus modified FOLFIRI with PARP inhibitor ABT-888 (veliparib) (NSC-737664) in metastatic pancreatic cancer (mPC): SWOG S1513.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. TPS4147-TPS4147
Author(s):  
E. Gabriela Chiorean ◽  
Shannon McDonough ◽  
Philip Agop Philip ◽  
Elizabeth M. Swisher ◽  
Michael J. Pishvaian ◽  
...  
Keyword(s):  
Dna Repair ◽  
Phase Ii ◽  
Phase Ii Study ◽  
Parp Inhibitor ◽  
New Drugs ◽  
Parp Inhibition ◽  
Dna Breaks ◽  
Antitumor Effects ◽  
Repair Capacity ◽  
Randomized Phase Ii

TPS4147 Background: PC is characterized by multiple DNA repair defects, including in BRCA1/ 2, and other homologous recombination (HR) genes such as FANC, ATM, ATR (Waddell N, Nature 2015). Folinic acid/5-fluorouracil/ irinotecan (FOLFIRI) is a 2nd line therapy option in mPC, but overall survival (OS) averages only 6 mos (Yoo C, Br J Cancer 2009). It is known that PARP facilitates repair from topoisomerase 1-associated DNA damage, and that preclinically PARP inhibitors (PARPi) increase DNA breaks from camptothecins, resulting in synergistic antitumor effects (Smith LM, Clin Cancer Res 2005, Davidson D, Invest New Drugs 2013). PARPi are active in mPC harboring BRCA1/2 mutations. Given the preclinical synergism between ABT-888 with irinotecan, and the safety and preliminary efficacy noted in a phase I trial (Berlin J, J Clin Oncol 2014; abstr 2574), we designed a randomized phase II study of mFOLFIRI /ABT-888 vs FOLFIRI alone for 2nd line mPC patients (pts). Blood and tumor samples are collected at baseline to retrospectively analyze biomarkers related to DNA repair capacity, including the HRD assay and BROCA-HR, a targeted multi-gene sequencing to detect alterations within the Fanconi Anemia-BRCA (HR), non-homologous end joining (NHEJ), and DNA mismatch repair pathways, and correlate with efficacy. Methods: Phase II study in 143 pts randomized (1:1) to mFOLFIRI/ABT-888 or FOLFIRI. For optimal PARP inhibition, ABT-888 is dosed Days (D) 1-7 and mFOLFIRI (no 5-FU bolus) D3-5 in 14D-cycles. In the control arm, FOLFIRI is dosed D1-3 in 14D-cycles. Primary endpoint: compare OS between treatment arms; secondary endpoints: safety, progression-free survival, response rates; translational: correlate germline/somatic BRCA1/2 mutations, and other DNA repair biomarkers with efficacy in each arm. Standard eligibility criteria apply. Assuming that the addition of ABT-888 will increase OS from 6 to 9 mos, 128 eligible pts (143 pts total) are required, based on a one-sided type 1 error of 10%, and 80% power. Kaplan-Meier methodology will be used to estimate median OS for each treatment arm. This study is open to accrual (NCT02890355). Clinical trial information: NCT02890355.

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