scholarly journals NAD+ bioavailability mediates PARG inhibition-induced replication arrest, intra S-phase checkpoint and apoptosis in glioma stem cells

NAR Cancer ◽  
2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Jianfeng Li ◽  
Kate M. Saville ◽  
Md Ibrahim ◽  
Xuemei Zeng ◽  
Steve McClellan ◽  
...  
Keyword(s):  
Stem Cells ◽  
Excision Repair ◽  
Single Agent ◽  
S Phase ◽  
Glioma Stem Cells ◽  
Replication Arrest ◽  
Replication Fork Progression ◽  
Elevated Expression ◽  
Base Excision ◽  
S Phase Checkpoint

Abstract Elevated expression of the DNA damage response proteins PARP1 and poly(ADP-ribose) glycohydrolase (PARG) in glioma stem cells (GSCs) suggests that glioma may be a unique target for PARG inhibitors (PARGi). While PARGi-induced cell death is achieved when combined with ionizing radiation, as a single agent PARG inhibitors appear to be mostly cytostatic. Supplementation with the NAD+ precursor dihydronicotinamide riboside (NRH) rapidly increased NAD+ levels in GSCs and glioma cells, inducing PARP1 activation and mild suppression of replication fork progression. Administration of NRH+PARGi triggers hyperaccumulation of poly(ADP-ribose) (PAR), intra S-phase arrest and apoptosis in GSCs but minimal PAR induction or cytotoxicity in normal astrocytes. PAR accumulation is regulated by select PARP1- and PAR-interacting proteins. The involvement of XRCC1 highlights the base excision repair pathway in responding to replication stress while enhanced interaction of PARP1 with PCNA, RPA and ORC2 upon PAR accumulation implicates replication associated PARP1 activation and assembly with pre-replication complex proteins upon initiation of replication arrest, the intra S-phase checkpoint and the onset of apoptosis.

Decrease in Abundance of Apurinic/Apyrimidinic Endonuclease Causes Failure of Base Excision Repair in Culture-Adapted Human Embryonic Stem Cells

Stem Cells ◽  
2013 ◽  
Vol 31 (4) ◽  
pp. 693-702 ◽  
Author(s):  
Miriama Krutá ◽  
Lukáš Bálek ◽  
Renata Hejnová ◽  
Zuzana Dobšáková ◽  
Livia Eiselleová ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Base Excision Repair ◽  
Human Embryonic Stem Cells ◽  
Excision Repair ◽  
Embryonic Stem ◽  
Base Excision

scholarly journals Basal CHK1 activity safeguards its stability to maintain intrinsic S-phase checkpoint functions

2019 ◽  
Vol 218 (9) ◽  
pp. 2865-2875 ◽  
Author(s):  
Jone Michelena ◽  
Marco Gatti ◽  
Federico Teloni ◽  
Ralph Imhof ◽  
Matthias Altmeyer
Keyword(s):  
Cell Proliferation ◽  
Steady State ◽  
Cell Survival ◽  
Replication Fork ◽  
S Phase ◽  
Genome Integrity ◽  
Replication Machinery ◽  
Replication Fork Progression ◽  
Steady State Activity ◽  
S Phase Checkpoint

The DNA replication machinery frequently encounters impediments that slow replication fork progression and threaten timely and error-free replication. The CHK1 protein kinase is essential to deal with replication stress (RS) and ensure genome integrity and cell survival, yet how basal levels and activity of CHK1 are maintained under physiological, unstressed conditions is not well understood. Here, we reveal that CHK1 stability is controlled by its steady-state activity during unchallenged cell proliferation. This autoactivatory mechanism, which depends on ATR and its coactivator ETAA1 and is tightly associated with CHK1 autophosphorylation at S296, counters CHK1 ubiquitylation and proteasomal degradation, thereby preventing attenuation of S-phase checkpoint functions and a compromised capacity to respond to RS. Based on these findings, we propose that steady-state CHK1 activity safeguards its stability to maintain intrinsic checkpoint functions and ensure genome integrity and cell survival.

EGFR amplification predicted selective sensitivity to PARP inhibitors with high PARP-DNA trapping potential in human GBM.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. 2047-2047
Author(s):  
W. K. Alfred Yung ◽  
Shaofang Wu ◽  
Feng Gao ◽  
Siyuan Zheng ◽  
Jie Ding ◽  
...  
Keyword(s):  
Stem Cells ◽  
Dna Damage ◽  
Parp Inhibitor ◽  
Single Agent ◽  
Parp Inhibitors ◽  
Glioma Stem Cells ◽  
Egfr Amplification ◽  
Damage Repair ◽  
Selective Sensitivity ◽  
Dna Trapping

2047 Background: Poly-ADP-ribose polymerase (PARP) is an enzyme critical for regulating a variety of DNA damage repair mechanisms such as BER/SSBR, and PARP inhibitors have been shown to have single agent activity in breast and ovarian cancer patients with BRCA ½ mutations. However, PARP inhibitor such as veliparib has limited single agent activity in GBM and identifying markers predicting sensitivity is critical to select individuals or certain groups of patients for PARP inhibitor therapy. Methods: Potency and selectivity of PARP inhibitors were analyzed in a panel of glioma stem cells (GSCs) with varying genetic background. In vivo anti-tumor activity was evaluated in xenograft models. Results: In this study, we report that PARP inhibitor, talazoparib, showed strong single-agent cytotoxicity and remarkable selective activity in glioma stem cells (GSCs). This single agent activity was strongly correlated with EGFR amplification. GSCs with EGFR amplification (which occurs in about 45% of GBMs) showed higher oxidative base damage, DNA breaks, and genomic instability than non-amplified GSCs. To sustain the elevated basal oxidative stress, EGFR-amplified GSCs had increased basal expression of DNA repair proteins. As a result of blocked DNA damage repair by talazoparib treatment, DNA damage accumulated and lead to increased PARP-DNA complexes, which was then trapped by talazoparib and resulted in high toxicity. The PARP-DNA trapping function of PARPi is essential as olaparib and veliparib, two PARP inhibitors with weak DNA-PARP trapping potential did not show sensitivity in GSCs. In contrast, Pamiparib, another PARP inhibitor with similar PARP-DNA trapping ability to that of talazoparib, showed selective sensitivity in EGFR-amplified GSC. Conclusions: Our data showed that EGFR amplified GSCs with higher basal DNA damage exhibited therapeutic vulnerability to PARP inhibitors with high PARP-DNA trapping ability, and that EGFR amplification is a potential selection or predictive biomarker for PARP inhibitor therapy in GBM.

scholarly journals Chronomodulation of cyclin-dependent kinases 4/6 inhibitor may reduce hematological toxicities? A review of literature

2018 ◽  
Vol 3 (3) ◽  
pp. 78
Author(s):  
Mukul Arvind Gharote
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Circadian Rhythm ◽  
Excision Repair ◽  
Human Mesenchymal Stem Cells ◽  
Peak Level ◽  
Early Morning ◽  
S Phase ◽  
Hematological Toxicity ◽  
Key Factor

<p class="s3">Nucleotide excision repair, DNA damage checkpoints, and apoptosis are under the influence of the circadian rhythm1. Circadian rhythm is defined as oscillations in the behavior and biochemical changes in an individual that repeats itself after the span of 24 h approximately. Cyclin-dependent kinase (CDK) inhibition causes cell cycle arrest and subsequent circadian stage-dependent gating of cells at G2-M interface of the cell cycle. Few anecdotes have suggested that chronomodulation reduces hematological toxicity in cell cycle-specific chemotherapy, especially S1-specific chemotherapy. In a study conducted by Boucher et al., 2016, circadian rhythm plays a role in the regulation of human mesenchymal stem cells (hMSCs) differentiation and division and likely represents key factor in maintaining hMSCs properties. If we apply the knowledge of circadian clock, then we know the fact that bone marrow stem cells (BMSCs) are under the control of circadian rhythm and G1-S phase of cell division cycle occurs at the early morning period of solar day. If CDK4/6 plasma peak level coincides with G1-S phase of BMSCs, then theoretically cytopenia may occur, which again is the sign of CDK4/6 action but is also the reason of its toxicity. Chronomodulation studies of CDK4/6 inhibitor may reduce hematological toxicity of CDK4/6 inhibitor.</p>

scholarly journals Activation of mammalian Chk1 during DNA replication arrest

2001 ◽  
Vol 154 (5) ◽  
pp. 913-924 ◽  
Author(s):  
Carmen Feijoo ◽  
Clare Hall-Jackson ◽  
Rong Wu ◽  
David Jenkins ◽  
Jane Leitch ◽  
...  
Keyword(s):  
Dna Replication ◽  
Mammalian Cells ◽  
S Phase ◽  
Global Pattern ◽  
Origin Firing ◽  
Replication Arrest ◽  
Molecule Inhibitor ◽  
Replication Block ◽  
Phase Progression ◽  
S Phase Checkpoint

Checkpoints maintain order and fidelity in the cell cycle by blocking late-occurring events when earlier events are improperly executed. Here we describe evidence for the participation of Chk1 in an intra-S phase checkpoint in mammalian cells. We show that both Chk1 and Chk2 are phosphorylated and activated in a caffeine-sensitive signaling pathway during S phase, but only in response to replication blocks, not during normal S phase progression. Replication block–induced activation of Chk1 and Chk2 occurs normally in ataxia telangiectasia (AT) cells, which are deficient in the S phase response to ionizing radiation (IR). Resumption of synthesis after removal of replication blocks correlates with the inactivation of Chk1 but not Chk2. Using a selective small molecule inhibitor, cells lacking Chk1 function show a progressive change in the global pattern of replication origin firing in the absence of any DNA replication. Thus, Chk1 is apparently necessary for an intra-S phase checkpoint, ensuring that activation of late replication origins is blocked and arrested replication fork integrity is maintained when DNA synthesis is inhibited.

Role of metformin on base excision repair pathway in p53 wild-type H2009 and HepG2 cancer cells

2017 ◽  
Vol 37 (9) ◽  
pp. 909-919 ◽  
Author(s):  
Irem Dogan Turacli ◽  
Tuba Candar ◽  
Berrin Emine Yuksel ◽  
Selda Demirtas
Keyword(s):  
Oxidative Stress ◽  
Cancer Cells ◽  
Base Excision Repair ◽  
Molecular Mechanisms ◽  
Excision Repair ◽  
Single Agent ◽  
Tumor Formation ◽  
Dna Base Excision Repair ◽  
Cellular Signal ◽  
Base Excision

The antidiabetic agent metformin was shown to further possess chemopreventive and chemotherapeutic effects against cancer. Despite the advances, the underlying molecular mechanisms involved in decreasing tumor formation are still unclear. The understanding of the participation of oxidative stress in the action mechanism of metformin and its related effects on p53 and on DNA base excision repair (BER) system can help us to get closer to solve metformin puzzle in cancer. We investigated the effects of metformin in HepG2 and H2009 cells, verifying cytotoxicity, oxidative stress, antioxidant status, and DNA BER system. Our results showed metformin induced oxidative stress and reduced antioxidant capacity. Also, metformin treatment with hydrogen peroxide (H2O2) enhanced these effects. Although DNA BER enzyme activities were not changed accordantly together by metformin as a single agent or in combination with H2O2, activated p53 was decreased with increased oxidative stress in H2009 cells. Our study on the relationship between metformin/reactive oxygen species and DNA BER system in cancer cells would be helpful to understand the anticancer effects of metformin through cellular signal transduction pathways. These findings can be a model of the changes on oxidative stress that reflects p53’s regulatory role on DNA repair systems in cancer for the future studies.

scholarly journals MODL-03. ADAPTING PALBOCICLIB FOR MEDULLOBLASTOMA THERAPY BY IMPROVING DRUG DELIVERY AND ADDRESSING RESISTANCE

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii412-iii412
Author(s):  
Taylor Dismuke ◽  
Timothy Gershon
Keyword(s):  
Cell Cycle ◽  
Drug Delivery ◽  
Stem Cells ◽  
Single Agent ◽  
Extended Period ◽  
S Phase ◽  
Systemic Toxicity ◽  
Stem Cell Marker ◽  
Pathway Activity ◽  
Shh Pathway

Abstract CDK4/6 inhibition may be a promising therapy for medulloblastoma. All medulloblastoma subgroups show D-cyclin/CDK4/RB pathway activity, suggesting broad potential for efficacy. To address drug delivery and systemic toxicity limitations, we developed a nanoparticle formulation of CDK 4/6 inhibitor, palbociclib, in poly (2-oxazoline) micelles (POx-palbo). POx-palbo showed reduced systemic toxicity in transgenic mice engineered to develop medulloblastoma, allowing for higher dosing. Pharmacodynamic studies showed POx-palbo suppressed RB phosphorylation acutely and after 24hrs, the effect diminished. This inhibition produced a longer lasting suppression of SHH pathway activity, demonstrated by Gli-luc reporter tumor mice. Importantly, POx-palbo therapy, administered daily, reduced tumor growth and improved the survival of mice with medulloblastoma. While POx-palbo was clearly effective as a single agent, all mice treated with POx-palbo eventually developed progressive disease, as resistant populations of tumors cells emerged. To understand the mechanisms of resistance, we compared tumors early and late in the course of therapy. We found that after 5 days of treatment, palbociclib altered cell cycle progression to produce an extended period of S-phase and that the fractions of cell expressing the stem cell marker Olig2 were markedly increased. Based on these data, we propose that tumors respond to the initial suppressive effect of palbociclib by increasing the pool of Olig2+ stem cells, that these cells show discernably different cell cycle kinetics and are resistant to CDK4/6 inhibition. Combining POx-palbo with additional therapies that target Olig2+ stem cells, by disrupting their prolonged S-phase, or by disrupting Olig2 function, may lead to newly effective medulloblastoma treatment.

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