scholarly journals Incorporation of Low Concentrations of Gold Nanoparticles: Complex Effects on Radiation Response and Fate of Cancer Cells

Pharmaceutics ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 166
Author(s):  
Lucie Dobešová ◽  
Theresa Gier ◽  
Olga Kopečná ◽  
Eva Pagáčová ◽  
Tomáš Vičar ◽  
...  
Keyword(s):  
Dna Damage ◽  
Gold Nanoparticles ◽  
Radiation Dose ◽  
Cancer Cells ◽  
Tumor Cells ◽  
Phase Cell ◽  
Dsb Repair ◽  
Post Irradiation ◽  
Low Concentrations ◽  
G2 Cells

(1) Background: In oncology research, a long-standing discussion exists about pros and cons of metal nanoparticle-enhanced radiotherapy and real mechanisms behind the tumor cell response to irradiation (IR) in presence of gold nanoparticles (GNPs). A better understanding of this response is, however, necessary to develop more efficient and safety nanoparticle (NP) types designed to disturb specific processes in tumor cells. (2) Aims and Methods: We combined 3D confocal microscopy and super-resolution single molecule localization microscopy (SMLM) to analyze, at the multiscale, the early and late effects of 10 nm-GNPs on DNA double strand break (DSB) induction and repair in tumor cells exposed to different doses of photonic low-LET (linear energy transfer) radiation. The results were correlated to different aspects of short and long-term cell viability. SkBr3 breast cancer cells (selected for the highest incidence of this cancer type among all cancers in women, and because most breast tumors are treated with IR) were incubated with low concentrations of GNPs and irradiated with 60Co γ-rays or 6 MV X-rays. In numerous post-irradiation (PI) times, ranging from 0.5 to 24 h PI, the cells were spatially (3D) fixed and labeled with specific antibodies against γH2AX, 53BP1 and H3K9me3. The extent of DSB induction, multi-parametric micro- and nano-morphology of γH2AX and 53BP1 repair foci, DSB repair kinetics, persistence of unrepaired DSBs, nanoscale clustering of γH2AX and nanoscale (hetero)chromatin re-organization were measured by means of the mentioned microscopy techniques in dependence of radiation dose and GNP concentration. (3) Results: The number of γH2AX/53BP1 signals increased after IR and an additional increase was observed in GNP-treated (GNP(+)) cells compared to untreated controls. However, this phenomenon reflected slight expansion of the G2-phase cell subpopulation in irradiated GNP(+) specimens instead of enhanced DNA damage induction by GNPs. This statement is further supported by some micro- and nano-morphological parameters of γH2AX/53BP1 foci, which slightly differed for cells irradiated in absence or presence of GNPs. At the nanoscale, Ripley’s distance frequency analysis of SMLM signal coordinate matrices also revealed relaxation of heterochromatin (H3K9me3) clusters upon IR. These changes were more prominent in presence of GNPs. The slight expansion of radiosensitive G2 cells correlated with mostly insignificant but systematic decrease in post-irradiation survival of GNP(+) cells. Interestingly, low GNP concentrations accelerated DSB repair kinetics; however, the numbers of persistent γH2AX/53BP1 repair foci were slightly increased in GNP(+) cells. (4) Conclusions: Low concentrations of 10-nm GNPs enhanced the G2/M cell cycle arrest and the proportion of radiosensitive G2 cells, but not the extent of DNA damage induction. GNPs also accelerated DSB repair kinetics and slightly increased presence of unrepaired γH2AX/53BP1 foci at 24 h PI. GNP-mediated cell effects correlated with slight radiosensitization of GNP(+) specimens, significant only for the highest radiation dose tested (4 Gy).

scholarly journals Nuclear Transglutaminase 2 interacts with topoisomerase II⍺ to promote DNA damage repair in lung cancer cells

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Xiao Lei ◽  
Kun Cao ◽  
Yuanyuan Chen ◽  
Hui Shen ◽  
Zhe Liu ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Dna Damage ◽  
Cancer Therapy ◽  
Cancer Cells ◽  
Protein Localization ◽  
Transglutaminase 2 ◽  
Lung Cancer Cells ◽  
Mass Spectrometry Analysis ◽  
Cancer Resistance ◽  
Dsb Repair

Abstract Background To block repairs of DNA damages, especially the DNA double strand break (DSB) repair, can be used to induce cancer cell death. DSB repair depends on a sequential activation of DNA repair factors that may be potentially targeted for clinical cancer therapy. Up to now, many protein components of DSB repair complex remain unclear or poorly characterized. In this study, we discovered that Transglutaminase 2 (TG2) acted as a new component of DSB repair complex. Methods A bioinformatic analysis was performed to identify DNA damage relative genes from dataset from The Cancer Genome Atlas. Immunofluorescence and confocal microscopy were used to monitor the protein localization and recruitment kinetics. Furthermore, immunoprecipitation and mass spectrometry analysis were performed to determine protein interaction of both full-length and fragments or mutants in distinct domain. In situ lung cancer model was used to study the effects cancer therapy in vivo. Results After DSB induction, cytoplasmic TG2 was extensively mobilized and translocated into nucleus after phosphorylated at T162 site by DNA-PKcs. Nuclear TG2 quickly accumulated at DSB sites and directly interacting with Topoisomerase IIα (TOPOIIα) with its TGase domain to promote DSB repair. TG2 deficient cells lost capacity of DSB repair and become susceptible to ionizing radiation. Specific inhibition of TG2-TOPOIIα interaction by glucosamine also significantly inhibited DSB repair, which increased sensitivity in lung cancer cells and engrafted lung cancers. Conclusions These findings elucidate new mechanism of TG2 in DSB repair trough directly interacting with TOPOIIα, inhibition of which provided potential target for overcoming cancer resistance.

scholarly journals WIP1 Promotes Homologous Recombination and Modulates Sensitivity to PARP Inhibitors

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1258 ◽  
Author(s):  
Kamila Burdova ◽  
Radka Storchova ◽  
Matous Palek ◽  
Libor Macurek
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Cancer Cells ◽  
Genotoxic Stress ◽  
Parp Inhibitors ◽  
Cell Cycle Checkpoint ◽  
Dna Lesion ◽  
Cycle Checkpoint ◽  
G2 Cells

Genotoxic stress triggers a combined action of DNA repair and cell cycle checkpoint pathways. Protein phosphatase 2C delta (referred to as WIP1) is involved in timely inactivation of DNA damage response by suppressing function of p53 and other targets at chromatin. Here we show that WIP1 promotes DNA repair through homologous recombination. Loss or inhibition of WIP1 delayed disappearance of the ionizing radiation-induced 53BP1 foci in S/G2 cells and promoted cell death. We identify breast cancer associated protein 1 (BRCA1) as interactor and substrate of WIP1 and demonstrate that WIP1 activity is needed for correct dynamics of BRCA1 recruitment to chromatin flanking the DNA lesion. In addition, WIP1 dephosphorylates 53BP1 at Threonine 543 that was previously implicated in mediating interaction with RIF1. Finally, we report that inhibition of WIP1 allowed accumulation of DNA damage in S/G2 cells and increased sensitivity of cancer cells to a poly-(ADP-ribose) polymerase inhibitor olaparib. We propose that inhibition of WIP1 may increase sensitivity of BRCA1-proficient cancer cells to olaparib.

scholarly journals AZD1775 Increases Sensitivity to Olaparib and Gemcitabine in Cancer Cells with p53 Mutations

Cancers ◽  
2018 ◽  
Vol 10 (5) ◽  
pp. 149 ◽  
Author(s):  
Xiangbing Meng ◽  
Jianling Bi ◽  
Yujun Li ◽  
Shujie Yang ◽  
Yuping Zhang ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cancer Cells ◽  
Tumor Cells ◽  
Gynecologic Cancer ◽  
Cell Cycle Checkpoints ◽  
Ovarian Cancer Cells ◽  
Tumor Suppressor P53 ◽  
New Approach ◽  
Dna Damaging Agents ◽  
Recurrent Gynecologic Cancer

Tumor suppressor p53 is responsible for enforcing cell cycle checkpoints at G1/S and G2/M in response to DNA damage, thereby allowing both normal and tumor cells to repair DNA before entering S and M. However, tumor cells with absent or mutated p53 are able to activate alternative signaling pathways that maintain the G2/M checkpoint, which becomes uniquely critical for the survival of such tumor cells. We hypothesized that abrogation of the G2 checkpoint might preferentially sensitize p53-defective tumor cells to DNA-damaging agents and spare normal cells with intact p53 function. The tyrosine kinase WEE1 regulates cdc2 activity at the G2/M checkpoint and prevents entry into mitosis in response to DNA damage or stalled DNA replication. AZD1775 is a WEE1 inhibitor that overrides and opens the G2/M checkpoint by preventing WEE1-mediated phosphorylation of cdc2 at tyrosine 15. In this study, we assessed the effect of AZD1775 on endometrial and ovarian cancer cells in the presence of two DNA damaging agents, the PARP1 inhibitor, olaparib, and the chemotherapeutic agent, gemcitabine. We show that AZD1775 alone is effective as a therapeutic agent against some p53 mutated cell models. Moreover, the combination of AZD1775 with olaparib or gemcitabine is synergistic in cells with mutant p53 and constitutes a new approach that should be considered in the treatment of advanced and recurrent gynecologic cancer.

scholarly journals Gold Nanoparticles for Targeting Varlitinib to Human Pancreatic Cancer Cells

Pharmaceutics ◽  
2018 ◽  
Vol 10 (3) ◽  
pp. 91 ◽  
Author(s):  
Sílvia Coelho ◽  
Daniel Reis ◽  
Maria Pereira ◽  
Manuel Coelho
Keyword(s):  
Pancreatic Cancer ◽  
Gold Nanoparticles ◽  
Drug Release ◽  
Cancer Cells ◽  
Photoelectron Spectroscopy ◽  
Drug Efficacy ◽  
Human Pancreatic Cancer ◽  
Pancreatic Cancer Cells ◽  
Low Concentrations

Colloidal gold nanoparticles are targeting probes to improve varlitinib delivery into cancer cells. The nanoconjugates were designed by the bioconjugation of pegylated gold nanoparticles with varlitinib via carbodiimide-mediated cross-linking and characterized by infrared and X-ray photoelectron spectroscopy. The drug release response shows an initial delay and a complete drug release after 72 h is detected. In vitro experiments with MIA PaCa-2 cells corroborate that PEGAuNPsVarl conjugates increase the varlitinib toxic effect at very low concentrations (IC50 = 80 nM) if compared with varlitinib alone (IC50 = 259 nM). Our results acknowledge a decrease of drug side effects in normal cells and an enhancement of drug efficacy against to the pancreatic cancer cells reported.

scholarly journals GINS1 Induced Sorafenib Resistance by Promoting Cancer Stem Properties in Human Hepatocellular Cancer Cells

2021 ◽  
Vol 9 ◽  
Author(s):  
Sheng Li ◽  
Lina Wu ◽  
Hong Zhang ◽  
Xijuan Liu ◽  
Zilei Wang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cancer Cells ◽  
Tumor Cells ◽  
Cell Activity ◽  
Hepatocellular Cancer ◽  
Gene Expression Omnibus ◽  
High Rate ◽  
Phase Cell

Hepatocellular carcinoma (HCC) is characterized by a high rate of incidence and recurrence, and resistance to chemotherapy may aggravate the poor prognosis of HCC patients. Sorafenib resistance is a conundrum to the treatment of advanced/recurrent HCC. Therefore, studies on the molecular pathogenesis of HCC and the resistance to sorafenib are of great interest. Here, we report that GINS1 was highly expressed in HCC tumors, associated with tumor grades, and predicted poor patient survival using Gene Expression Omnibus (GEO) databases exploration. Cell cycle, cell proliferation assay and in vivo xenograft mouse model indicated that knocking down GINS1 induced in G1/S phase cell cycle arrest and decreased tumor cells proliferation in vitro and in vivo. Spheroid formation assay results showed that GINS1 promoted the stem cell activity of HCC tumor cells. Furthermore, GEO database (GSE17112) analysis showed that HRAS oncogenic gene set was enriched in GINS1 high-expressed cancer cells, and quantitative real-time PCR, and Western blot results proved that GINS1 enhanced HCC progression through regulating HRAS signaling pathway. Moreover, knocking down endogenous GINS1 with shGINS1 increased the sensitivity of HCC cells to sorafenib, and restoring HRAS or stem associated pathway partly recovered the sorafenib resistance. Overall, the collective findings highlight GINS1 functions in hepatocarcinogenesis and sorafenib resistance, and indicate its potential use of GINS1 in drug-resistant HCC.

scholarly journals Assessment of the Influence of 5-fluorouracil on the SMAD4 Gene Expression, Apoptosis induction and DNA Damage in the Human CACO-2 Cell Line

2021 ◽  
Author(s):  
Agnieszka Wosiak ◽  
Katarzyna Michalska ◽  
Jacek Pietrzak ◽  
Marek Mirowski ◽  
Ewa Balcerczak
Keyword(s):  
Gene Expression ◽  
Colorectal Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Downstream Signaling ◽  
Cycle Arrest ◽  
Low Concentrations ◽  
Late Stage Cancer ◽  
Colorectal Cancer Cells ◽  
Colorectal Cancer Patients

Abstract Colorectal cancer (CRC) is the third most common cancer in the world. There are two major distinct precursor lesion pathways: the traditional adenoma–carcinoma pathway leading to most cases CRC, and the serrated neoplasia pathway. SMAD4 gene is involved in adenoma–carcinoma pathway. The protein encoded by the SMAD4 gene is a key downstream signaling mediator in the TGFβ pathway. This pathway has tumor-suppressor functions, including cell-cycle arrest and apoptosis. Its activation in late-stage cancer can promote tumorigenesis, including metastasis and chemoresistance. This study aimed to evaluate the effect of 5-fluorouracil (5-FU) on viability of advanced colorectal cancer cells and establishing whether the test compound may have an effect on the expression level of the SMAD4 gene, DNA damage and apoptosis. Chemotherapy based on 5-FU is used as an adjuvant treatment in most colorectal cancer patients. The results obtained in the study showed that the use of 5-FU in low concentrations may not have a therapeutic effect, and may also influence drug resistance in cancer cells. Moreover, it has been shown that by using 5-FU at higher concentrations and prolonging the exposure time, SMAD4 gene expression is significantly increased which may have an impact on the effectiveness of the therapy.

scholarly journals DNA-Ligase IV and DNA-Protein Kinase Play a Critical Role in Deficient Caspases Activation in Apoptosis-resistant Cancer Cells by Using Doxorubicin

2008 ◽  
Vol 19 (8) ◽  
pp. 3283-3289 ◽  
Author(s):  
Claudia Friesen ◽  
Miriam Uhl ◽  
Ulrich Pannicke ◽  
Klaus Schwarz ◽  
Erich Miltner ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Kinase ◽  
Cancer Cells ◽  
Critical Role ◽  
Dna Ligase ◽  
Apoptosis Resistance ◽  
Dsb Repair ◽  
Doxorubicin Treatment ◽  
Dna Ligase Iv ◽  
Ligase Iv

Resistance toward cytotoxic drugs is one of the primary causes for therapeutic failure in cancer therapy. DNA repair mechanisms as well as deficient caspases activation play a critical role in apoptosis resistance of tumor cells toward anticancer drug treatment. Here, we discovered that deficient caspases activation in apoptosis-resistant cancer cells depends on DNA-ligase IV and DNA-protein kinase (DNA-PK), playing crucial roles in the nonhomologous end joining (NHEJ) pathway, which is the predominant pathway for DNA double-strand break repair (DNA-DSB-repair) in mammalian cells. DNA-PK(+/+) as well as DNA-ligase IV (+/+) cancer cells were apoptosis resistant and deficient in activation of caspase-3, caspase-9, and caspase-8 and in cleavage of poly(ADP-ribose) polymerase after doxorubicin treatment. Inhibition of NHEJ by knocking out DNA-PK or DNA-ligase IV restored caspases activation and apoptosis sensitivity after doxorubicin treatment. In addition, inhibition of caspases activation prevented doxorubicin-induced apoptosis but could not prevent doxorubicin-induced DNA damage, indicating that induction of DNA damage is independent of caspases activation. However, caspases activation depends on induction of DNA damage left unrepaired by NHEJ-DNA-DSB-repair. We conclude that DNA damage left unrepaired by DNA-ligase IV or DNA-PK might be the initiator for caspases activation by doxorubicin in cancer cells. Failure in caspases activation using doxorubicin depends on loss of DNA damage and is due to higher rates of NHEJ-DNA-DBS-repair.

scholarly journals 2467 PRMT5 is a master epigenetic regulator to promote repair of radiation-induced DNA damage

2018 ◽  
Vol 2 (S1) ◽  
pp. 24-24
Author(s):  
Jake L. Owens
Keyword(s):  
Prostate Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Cancer Patients ◽  
Cell Lines ◽  
Cancer Cell ◽  
Target Genes ◽  
Prostate Cancer Cells ◽  
G2 Arrest ◽  
Dsb Repair

OBJECTIVES/SPECIFIC AIMS: We recently reported that PRMT5 epigenetically activates androgen receptor (AR) in prostate cancer cells. Because targeting AR signaling through androgen deprivation therapy is clinically used as a radiosensitization approach to treat high-risk prostate cancer, our finding raised an exciting possibility that targeting PRMT5 may improve RT for prostate cancer patients. Contrary to our expectation, targeting PRMT5 sensitized both AR expressing and AR negative (AR−) prostate cancer cell lines to radiation. The goal of our study was therefore to determine the role of PRMT5 in repair of IR-induced DSBs and to translate these findings to improving radiation therapy for cancer patients in general (not just prostate cancer patients). METHODS/STUDY POPULATION: The majority of experiments were basic science experiments analyzing PRMT5’s role in the DNA damage response in normal and cancer cell lines. For example, to extend our findings and determine if PRMT5’s role in DSB repair is conserved across multiple cell types, we performed similar experiments in AR− prostate cancer cells, luminal breast cancer cells, glioblastoma cells, and human embryonic kidney cells. To determine the clinical significance of our finding, we also analyzed mRNA expression of PRMT5, AR, and both PRMT5 and AR target genes involved in DSB repair across 43 clinical cancer data sets. RESULTS/ANTICIPATED RESULTS: (1) Targeting PRMT5 sensitizes prostate cancer cells to IR in an AR-independent manner, (2) PRMT5 regulates the repair of IR-induced DSBs in an AR-independent manner, (3) RNA-seq analysis reveals that PRMT5 likely regulates genes involved in the DNA damage response, (4) PRMT5 activates expression of several genes in the DDR including those involved in DSB repair, (5) PRMT5 functions as an epigenetic activator of genes involved in DDR, (6) PRMT5 is required for NHEJ, HR, and G2-Arrest upon IR treatment, (7) Upregulation of PRMT5 correlates with formation and repair of IR-induced DSBs, (8) PRMT5’s role in repair of IR-induced DSBs is conserved in several normal and cancer cell types, and (9) PRMT5 expression correlates with expression of DSB repair proteins in clinical cancer samples. DISCUSSION/SIGNIFICANCE OF IMPACT: In summary, we provide evidence that PRMT5 is a master epigenetic regulator of IR-induced DSB repair through epigenetic activation of multiple target genes involved both HR and NHEJ as well as G2 arrest. Interestingly, the majority of genes regulated by PRMT5 are well-characterized, “core repair proteins” involved in HR (RAD51, BRCA1, BRCA2, RAD51D, and RAD51AP1), NHEJ (NHEJ1, Ku80, XRCC4, and DNAPKcs), and G2 arrest (Cdk1, CDC25C, CCNB2, and WEE1), which may explain why PRMT5 is essential to repair IR-induced DSBs in several cell lines. Although AR may also regulate DSB repair via both HR and NHEJ, several pieces of evidence in our study suggest that PRMT5 also regulates DSB repair independent of AR. First, PRMT5 targeting sensitizes both AR+ and AR− prostate cancer cells to IR. Second, exogenous expression of AR only partially rescues the impairment of IR-induced DSB repair by PRMT5 knockdown. Third, PRMT5 knockdown increases IR-induced DSB in AR− DU145 cells and several other cancer cell lines and normal cells. Fourth, PRMT5 expression correlates positively with the expression of its target genes in multiple human cancer tissues. During preparation of this project, Braun et al. reported that PRMT5 post-translationally regulates the splicing out of detained-introns (DI)s of genes to modulate gene expression. However, analysis of their data showed that the majority of DEGs we identified either do not contain DIs or DI splicing was not affected by targeting PRMT5. In addition, Clarke et al. reported that PRMT5 participates in the DSB repair choice process and promotes HR through methylation of RUVBL1. It is therefore likely that PRMT5 regulates repair of IR-induced DSB via multiple mechanisms. As PRMT5 is overexpressed in many human cancers and its overexpression correlates with poor prognosis, our findings suggest that increased DSB repair by PRMT5 overexpression in these human cancers may confer survival advantages particularly following DNA damaging treatment. Because targeting DSB repair has been proven to be a valid therapeutic approach for cancer treatment, our findings here also suggest that PRMT5 targeting may be explored as a monotherapy or in combination therapy with RT or chemotherapy for cancer treatment.

scholarly journals Targeting DNA Double-Strand Break Repair Pathways to Improve Radiotherapy Response

Genes ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 25 ◽  
Author(s):  
Mahmoud Toulany
Keyword(s):  
Dna Damage ◽  
Signaling Pathways ◽  
Tumor Cells ◽  
Tyrosine Kinases ◽  
Strand Break ◽  
Cell Cycle Checkpoints ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Repair Pathways ◽  
Cytoplasmic Signaling

More than half of cancer patients receive radiotherapy as a part of their cancer treatment. DNA double-strand breaks (DSBs) are considered as the most lethal form of DNA damage and a primary cause of cell death and are induced by ionizing radiation (IR) during radiotherapy. Many malignant cells carry multiple genetic and epigenetic aberrations that may interfere with essential DSB repair pathways. Additionally, exposure to IR induces the activation of a multicomponent signal transduction network known as DNA damage response (DDR). DDR initiates cell cycle checkpoints and induces DSB repair in the nucleus by non-homologous end joining (NHEJ) or homologous recombination (HR). The canonical DSB repair pathways function in both normal and tumor cells. Thus, normal-tissue toxicity may limit the targeting of the components of these two pathways as a therapeutic approach in combination with radiotherapy. The DSB repair pathways are also stimulated through cytoplasmic signaling pathways. These signaling cascades are often upregulated in tumor cells harboring mutations or the overexpression of certain cellular oncogenes, e.g., receptor tyrosine kinases, PIK3CA and RAS. Targeting such cytoplasmic signaling pathways seems to be a more specific approach to blocking DSB repair in tumor cells. In this review, a brief overview of cytoplasmic signaling pathways that have been reported to stimulate DSB repair is provided. The state of the art of targeting these pathways will be discussed. A greater understanding of the underlying signaling pathways involved in DSB repair may provide valuable insights that will help to design new strategies to improve treatment outcomes in combination with radiotherapy.

scholarly journals Genome-wide screen of cell-cycle regulators in normal and tumor cells identifies a differential response to nucleosome depletion

2016 ◽  
Author(s):  
Maria Sokolova ◽  
Mikko Turunen ◽  
Oliver Mortusewicz ◽  
Teemu Kivioja ◽  
Patrick Herr ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cancer Cells ◽  
Tumor Cells ◽  
S Phase ◽  
Replication Forks ◽  
Cell Cycle Regulators ◽  
Normal Cells ◽  
Viable Cells ◽  
Genome Wide

AbstractTo identify cell cycle regulators that enable cancer cells to replicate DNA and divide in an unrestricted manner, we performed a parallel genome-wide RNAi screen in normal and cancer cell lines. In addition to many shared regulators, we found that tumor and normal cells are differentially sensitive to loss of the histone genes transcriptional regulator CASP8AP2. In cancer cells, loss of CASP8AP2 leads to a failure to synthesize sufficient amount of histones in the S-phase of the cell cycle, resulting in slowing of individual replication forks. Despite this, DNA replication fails to arrest, and tumor cells progress in an elongated S-phase that lasts several days, finally resulting in death of most of the affected cells. In contrast, depletion of CASP8AP2 in normal cells triggers a response that arrests viable cells in S-phase. The arrest is dependent on p53, and preceded by accumulation of markers of DNA damage, indicating that nucleosome depletion is sensed in normal cells via a DNA-damage-like response that is defective in tumor cells.

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