@phdthesis{Zimnol2017,
  author    = {Zimnol, Anna},
  title     = {Relevance of angiotensin II type 1a receptor and NADPH oxidase for the formation of angiotensin II-mediated DNA damage},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137469},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {Das Renin-Angiotensin-Aldosteron-System (RAAS) reguliert den Blutdruck sowie den Elektrolyt- und Wasserhaushalt. Das aktive Peptid, Angiotensin II (AngII), f{\"u}hrt dabei zur Vasokonstriktion und in h{\"o}heren Konzentrationen zu Bluthochdruck. Hypertensive Patienten haben ein erh{\"o}htes Risiko an Krebs zu erkranken, vor allem an Nierenkrebs. Wir konnten bereits in vivo zeigen, dass AngII in der Lage ist, den Blutdruck zu steigern und dosisabh{\"a}ngig zu DNA-Sch{\"a}den {\"u}ber den Angiotensin II Typ 1-Rezeptor (AT1R) f{\"u}hrt. Ein stimuliertes RAAS kann ferner {\"u}ber die Aktivierung der NADPH-Oxidase, einer Hauptquelle der Generierung reaktiver Sauerstoffspezies (ROS) in der Zelle, zu oxidativem Stress f{\"u}hren. Zielsetzung dieser Arbeit war es zum einen, mit Hilfe von AT1a-Rezeptor-defizienten M{\"a}usen in vivo zu pr{\"u}fen, ob die Bildung von ROS, sowie die Bildung von DNA-Sch{\"a}den in der Niere und im Herzen unabh{\"a}ngig von einem erh{\"o}hten Blutdruck auftreten. Zum anderen sollte, ebenfalls in vivo, untersucht werden, ob eine oder beide von zwei untersuchten Isoformen der NADPH-Oxidase (Nox) f{\"u}r die Ausl{\"o}sung oxidativen Stresses in der Niere verantwortlich ist. Zun{\"a}chst wurden f{\"u}r den Versuch zur {\"U}berpr{\"u}fung der Abh{\"a}ngigkeit AngII-induzierter DNA-Sch{\"a}den vom Blutdruck m{\"a}nnliche C57BL/6-M{\"a}use und AT1a-Knockout (KO)-M{\"a}use mit osmotischen Minipumpen ausgestattet, die AngII in einer Konzentrationen von 600 ng/kg min {\"u}ber einen Zeitraum von 28 Tagen abgaben. Zus{\"a}tzlich wurde eine Gruppe von AngII-behandelten Wildtyp (WT)-M{\"a}usen mit dem AT1-Rezeptor-Blocker Candesartan (Cand) behandelt. W{\"a}hrend des Versuchszeitraumes fanden regelm{\"a}ßige, nicht-invasive Blutdruckmessungen an den wachen M{\"a}usen statt. In WT-M{\"a}usen induzierte AngII Bluthochdruck, verursachte erh{\"o}hte Albumin-Level im Urin und f{\"u}hrte zur Bildung von ROS in Niere und im Herzen. Außerdem traten in dieser Gruppe DNA-Sch{\"a}den in Form von Einzel- und Doppelstrangbr{\"u}chen auf. All diese Reaktionen auf AngII konnten jedoch durch gleichzeitige Behandlung mit Cand verhindert werden. AT1a-KO-M{\"a}use hatten, verglichen mit WT-Kontrollm{\"a}usen, einen signifikant niedrigeren Blutdruck und normale Albumin-Level im Urin. In AT1a-KO-M{\"a}usen, die mit AngII behandelt wurden, konnte kein Anstieg des systolischen Blutdrucks sowie kein Einfluss auf die Nierenfunktion gefunden werden. Jedoch f{\"u}hrte AngII in dieser Gruppe zu einer Steigerung von ROS in der Niere und im Herzen. Zus{\"a}tzlich wurden genomische Sch{\"a}den, vor allem in Form von Doppelstrangbr{\"u}chen signifikant in dieser Gruppe induziert. Auch wenn AT1a-KO-Tiere, unabh{\"a}ngig von einer AngII-Infusion, keine eingeschr{\"a}nkte Nierenfunktion zeigten, so wiesen sie erhebliche histopathologische Sch{\"a}den im Hinblick auf die Glomeruli und das Tubulussystem auf. Diese Art von Sch{\"a}den deuten auf eine besondere Bedeutung des AT1aR im Hinblick auf die embryonale Entwicklung der Niere hin. Zusammenfassend beweisen die Ergebnisse dieses Experiments eindeutig, dass eine AngII-induzierte ROS-Produktion und die Induktion von DNA-Sch{\"a}den unabh{\"a}ngig von einem erh{\"o}hten Blutdruck auftreten. Da in der AngII-behandelten AT1a-KO-Gruppe eine signifikant h{\"o}here Expression des AT1b-Rezeptors zu finden war und die Blockade von beiden Rezeptorsubtypen mit Cand zu einer Verhinderung der sch{\"a}dlichen Effekte durch AngII f{\"u}hrte, scheint der AT1bR im Falle einer AT1aR-Defizienz f{\"u}r die Entstehung der Sch{\"a}den zust{\"a}ndig zu sein. Ziel des zweiten Experimentes war es, den Beitrag der Nox2 und Nox4 zum oxidativen DNA-Schaden in vivo zu untersuchen. Hierf{\"u}r wurden m{\"a}nnliche C57BL/6-M{\"a}use und Nox2- oder Nox4-defiziente M{\"a}use mit osmotischen Minipumpen ausgestattet, die AngII in einer Konzentration von 600 ng/kg min {\"u}ber einen Zeitraum von 28 Tagen abgaben. Im WT-Stamm und in beiden Nox-defizienten St{\"a}mmen induzierte AngII Bluthochdruck, verursachte erh{\"o}hte Albumin-Level im Urin und f{\"u}hrte zur Bildung von ROS in der Niere. Außerdem waren in allen AngII-behandelten Gruppen genomische Sch{\"a}den, vor allem in Form von Doppelstrangbr{\"u}chen, erh{\"o}ht. Auch in Abwesenheit von AngII wiesen Nox2- und Nox4-defiziente M{\"a}use mehr Doppelstrangbr{\"u}che im Vergleich zu WT-Kontrollm{\"a}usen auf. Interessanterweise kompensieren allerdings weder Nox2 noch Nox4 das Fehlen der jeweils anderen Isoform auf RNA-Basis. Aufgrund dieser Ergebnisse schließen wir, dass bislang keine Isoform alleine f{\"u}r die Generierung von oxidativen DNA-Sch{\"a}den in der Niere verantwortlich gemacht werden kann und dass eine Beteiligung einer weiteren Nox-Isoform sehr wahrscheinlich ist. M{\"o}glicherweise k{\"o}nnten aber auch andere ROS-generierende Enzyme, wie Xanthinoxidase oder Stickoxidsynthase involviert sein. Da genomische Sch{\"a}den in Nieren von Nox2- und Nox4-defizienten M{\"a}usen in Abwesenheit von AngII gegen{\"u}ber den Sch{\"a}den in WT-Kontrollm{\"a}usen erh{\"o}ht waren, k{\"o}nnten die beiden Isoformen auch eine sch{\"u}tzende Funktion im Bereich von Nierenkrankheiten {\"u}bernehmen. Da dies aber bislang nur f{\"u}r Nox4 beschrieben ist, ist es wahrscheinlicher, dass das Fehlen von einer der beiden Isoformen eher einen Einfluss auf die Embryonalentwicklung hat. Um dies jedoch abschließend zu kl{\"a}ren w{\"a}re es sinnvoll mit induzierbaren Knockout-Modellen zu arbeiten, bei denen m{\"o}gliche entwicklungsbedingte Effekte minimiert werden k{\"o}nnen.},
  subject      = {Angiotensin II},
  language  = {de}
}
@article{TrifaultMamontovaBurger2022,
  author    = {Trifault, Barbara and Mamontova, Victoria and Burger, Kaspar},
  title     = {In vivo proximity labeling of nuclear and nucleolar proteins by a stably expressed, DNA damage-responsive NONO-APEX2 fusion protein},
  series = {Frontiers in Molecular Biosciences},
  volume    = {9},
  journal   = {Frontiers in Molecular Biosciences},
  issn      = {2296-889X},
  doi       = {10.3389/fmolb.2022.914873},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-276707},
  year      = {2022},
  abstract  = {Cellular stress can induce DNA lesions that threaten the stability of genes. The DNA damage response (DDR) recognises and repairs broken DNA to maintain genome stability. Intriguingly, components of nuclear paraspeckles like the non-POU domain containing octamer-binding protein (NONO) participate in the repair of DNA double-strand breaks (DSBs). NONO is a multifunctional RNA-binding protein (RBP) that facilitates the retention and editing of messenger (m)RNA as well as pre-mRNA processing. However, the role of NONO in the DDR is poorly understood. Here, we establish a novel human U2OS cell line that expresses NONO fused to the engineered ascorbate peroxidase 2 (U2OS:NONO-APEX2-HA). We show that NONO-APEX2-HA accumulates in the nucleolus in response to DNA damage. Combining viability assays, subcellular localisation studies, coimmunoprecipitation experiments and in vivo proximity labeling, we demonstrate that NONO-APEX2-HA is a stably expressed fusion protein that mimics endogenous NONO in terms of expression, localisation and bona fide interactors. We propose that in vivo proximity labeling in U2OS:NONO-APEX2-HA cells is capable for the assessment of NONO interactomes by downstream assays. U2OS:NONO-APEX2-HA cells will likely be a valuable resource for the investigation of NONO interactome dynamics in response to DNA damage and other stimuli.},
  language  = {en}
}
@phdthesis{Schmid2008,
  author    = {Schmid, Ursula},
  title     = {Protection against oxidative DNA damage by antioxidants, hormone-receptor blockers and HMG-CoA-reductase inhibitors},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28379},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {In the course of this study, several endogenous compounds and model substances were used to mimic the conditions in patients suffering from hypertension. As endogenous compounds, angiotensin II and aldosterone were chosen. As model substances, 4-nitroquinoline-1-oxide (NQO), hydrogen peroxide and phorbol 12-myristate 13-acetate (PMA) were selected. Benfotiamine as well as \&\#945;-tocopherol proved in the course of the experiments to be able to prevent angiotensin II-induced formation of oxidative DNA strand breaks and micronuclei. This could be due to a prior inhibition of the release of reactive oxygen species and is in contrast to results which were achieved using thiamine. Furthermore, experiments in which cells were pre-incubated with benfotiamine followed by incubation with NQO showed that benfotiamine was not able to prevent the induction of oxidative stress. The hypothesis that benfotiamine has, like \&\#945;-tocopherol, direct antioxidative capacity was fortified by measurements in cell free systems. In brief, a new working mechanism for benfotiamine in addition to the ones already known could be provided. In the second part of the study, angiotensin II was shown to be dose-dependently genotoxic. This effect is mediated via the angiotensin II type 1 receptor (AT1R) which. Further experiments were extended from in vitro settings to the isolated perfused kidney. Here it could be shown that angiotensin II caused vasoconstriction and DNA strand breaks. Co-perfusion of kidneys with angiotensin II and candesartan prevented vasoconstriction and formation of strand breaks. DNA strand break formation due to mechanical stress or hypoxia could be ruled out after additional experiments with the thromboxane mimetic U 46619. Detailed investigation of the DNA damage in vitro revealed that angiotensin II induces single strand breaks, double strand breaks and 8-hydroxydeoxyguanosine (8-oxodG)-adducts as well as abasic sites. Investigations of the effects of aldosterone-treatment in kidney cells showed an increase of oxidative stress, DNA strand breaks and micronuclei which could be prevented by the steroidal mineralocorticoid receptor antagonist eplerenone. Additional experiments with the non-steroidal mineralocorticoid receptor antagonist (S)-BR-4628 revealed that this substance was also able to prevent oxidative stress and genomic damage and proved to be more potent than eplerenone. In vivo, hyperaldosteronism was imitated in rats by aid of the deoxycorticosteroneacetate (DOCA) salt model. After this treatment, levels of DNA strand breaks and chromosomal aberrations in the kidney could be observed. Furthermore, an increase in the release of ROS could be measured. Treatment of these animals with spironolactone , BR-4628 and enalaprile revealed that all antagonists were effective BR-4628 was the most potent drug. Finally, rosuvastatin was investigated. In HL-60 cells phorbol 12-myristate 13-acetate caused oxidative stress. Rosuvastatin was able to prevent the release of ROS and subsequent oxidative DNA damage when co-incubated with PMA. Furthermore, not only an inhibition of PMA-induced oxidative stress but also inhibition of the unspecific release of ROS induced by hydrogen peroxide was observable. Addition of farnesyl pyrophosphate (FPP), geranylgeranyl pyrophosphate (GGPP), and mevalonate, intermediates of the cholesterol pathway, caused only a marginal increase of oxidative stress in cells treated simultaneously with PMA and rosuvastatin, thus indicating the effect of rosuvastatin to be HMG-CoA-reductase-independent. Investigation of the gene expression of subunits of NAD(P)H oxidase revealed a down-regulation of p67phox following rosuvastatin-treatment. Furthermore, it could be shown that rosuvastatin treatment alone or in combination with PMA increased total glutathione levels probably due to an induction of the gene expression and enzyme activity of \&\#947;-glutamylcysteine synthetase (\&\#947;-GCS).},
  subject      = {Oxidativer Stress},
  language  = {en}
}
@article{OthmanNaseemAwadetal.2016,
  author    = {Othman, Eman M. and Naseem, Muhammed and Awad, Eman and Dandekar, Thomas and Stopper, Helga},
  title     = {The Plant Hormone Cytokinin Confers Protection against Oxidative Stress in Mammalian Cells},
  series = {PLoS One},
  volume    = {11},
  journal   = {PLoS One},
  number    = {12},
  doi       = {10.1371/journal.pone.0168386},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-147983},
  pages     = {e0168386},
  year      = {2016},
  abstract  = {Modulating key dynamics of plant growth and development, the effects of the plant hormone cytokinin on animal cells gained much attention recently. Most previous studies on cytokinin effects on mammalian cells have been conducted with elevated cytokinin concentration (in the μM range). However, to examine physiologically relevant dose effects of cytokinins on animal cells, we systematically analyzed the impact of kinetin in cultured cells at low and high concentrations (1nM-10μM) and examined cytotoxic and genotoxic conditions. We furthermore measured the intrinsic antioxidant activity of kinetin in a cell-free system using the Ferric Reducing Antioxidant Power assay and in cells using the dihydroethidium staining method. Monitoring viability, we looked at kinetin effects in mammalian cells such as HL60 cells, HaCaT human keratinocyte cells, NRK rat epithelial kidney cells and human peripheral lymphocytes. Kinetin manifests no antioxidant activity in the cell free system and high doses of kinetin (500 nM and higher) reduce cell viability and mediate DNA damage in vitro. In contrast, low doses (concentrations up to 100 nM) of kinetin confer protection in cells against oxidative stress. Moreover, our results show that pretreatment of the cells with kinetin significantly reduces 4-nitroquinoline 1-oxide mediated reactive oxygen species production. Also, pretreatment with kinetin retains cellular GSH levels when they are also treated with the GSH-depleting agent patulin. Our results explicitly show that low kinetin doses reduce apoptosis and protect cells from oxidative stress mediated cell death. Future studies on the interaction between cytokinins and human cellular pathway targets will be intriguing.},
  language  = {en}
}
@article{MaierhoferFlunkertDittrichetal.2017,
  author    = {Maierhofer, Anna and Flunkert, Julia and Dittrich, Marcus and M{\"u}ller, Tobias and Schindler, Detlev and Nanda, Indrajit and Haaf, Thomas},
  title     = {Analysis of global DNA methylation changes in primary human fibroblasts in the early phase following X-ray irradiation},
  series = {PLoS ONE},
  volume    = {12},
  journal   = {PLoS ONE},
  number    = {5},
  doi       = {10.1371/journal.pone.0177442},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170895},
  pages     = {e0177442},
  year      = {2017},
  abstract  = {Epigenetic alterations may contribute to the generation of cancer cells in a multi-step process of tumorigenesis following irradiation of normal body cells. Primary human fibroblasts with intact cell cycle checkpoints were used as a model to test whether X-ray irradiation with 2 and 4 Gray induces direct epigenetic effects (within the first cell cycle) in the exposed cells. ELISA-based fluorometric assays were consistent with slightly reduced global DNA methylation and hydroxymethylation, however the observed between-group differences were usually not significant. Similarly, bisulfite pyrosequencing of interspersed LINE-1 repeats and centromeric α-satellite DNA did not detect significant methylation differences between irradiated and non-irradiated cultures. Methylation of interspersed ALU repeats appeared to be slightly increased (one percentage point; p = 0.01) at 6 h after irradiation with 4 Gy. Single-cell analysis showed comparable variations in repeat methylation among individual cells in both irradiated and control cultures. Radiation-induced changes in global repeat methylation, if any, were much smaller than methylation variation between different fibroblast strains. Interestingly, α-satellite DNA methylation positively correlated with gestational age. Finally, 450K methylation arrays mainly targeting genes and CpG islands were used for global DNA methylation analysis. There were no detectable methylation differences in genic (promoter, 5' UTR, first exon, gene body, 3' UTR) and intergenic regions between irradiated and control fibroblast cultures. Although we cannot exclude minor effects, i.e. on individual CpG sites, collectively our data suggest that global DNA methylation remains rather stable in irradiated normal body cells in the early phase of DNA damage response.},
  language  = {en}
}
@article{LeikamHufnagelOttoetal.2015,
  author    = {Leikam, C and Hufnagel, AL and Otto, C and Murphy, DJ and M{\"u}hling, B and Kneitz, S and Nanda, I and Schmid, M and Wagner, TU and Haferkamp, S and Br{\"o}cker, E-B and Schartl, M and Meierjohann, S},
  title     = {In vitro evidence for senescent multinucleated melanocytes as a source for tumor-initiating cells},
  series = {Cell Death and Disease},
  volume    = {6},
  journal   = {Cell Death and Disease},
  number    = {e1711},
  doi       = {10.1038/cddis.2015.71},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148718},
  year      = {2015},
  abstract  = {Oncogenic signaling in melanocytes results in oncogene-induced senescence (OIS), a stable cell-cycle arrest frequently characterized by a bi-or multinuclear phenotype that is considered as a barrier to cancer progression. However, the long-sustained conviction that senescence is a truly irreversible process has recently been challenged. Still, it is not known whether cells driven into OIS can progress to cancer and thereby pose a potential threat. Here, we show that prolonged expression of the melanoma oncogene N-RAS\(^{61K}\) in pigment cells overcomes OIS by triggering the emergence of tumor-initiating mononucleated stem-like cells from senescent cells. This progeny is dedifferentiated, highly proliferative, anoikis-resistant and induces fast growing, metastatic tumors. Our data describe that differentiated cells, which are driven into senescence by an oncogene, use this senescence state as trigger for tumor transformation, giving rise to highly aggressive tumor-initiating cells. These observations provide the first experimental in vitro evidence for the evasion of OIS on the cellular level and ensuing transformation.},
  language  = {en}
}
@article{HenrikssonCalderonMontanoSolvieetal.2022,
  author    = {Henriksson, Sofia and Calder{\´o}n-Monta{\~n}o, Jos{\´e} Manuel and Solvie, Daniel and Warpman Berglund, Ulrika and Helleday, Thomas},
  title     = {Overexpressed c-Myc sensitizes cells to TH1579, a mitotic arrest and oxidative DNA damage inducer},
  series = {Biomolecules},
  volume    = {12},
  journal   = {Biomolecules},
  number    = {12},
  issn      = {2218-273X},
  doi       = {10.3390/biom12121777},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-297547},
  year      = {2022},
  abstract  = {Previously, we reported that MTH1 inhibitors TH588 and TH1579 selectively induce oxidative damage and kill Ras-expressing or -transforming cancer cells, as compared to non-transforming immortalized or primary cells. While this explains the impressive anti-cancer properties of the compounds, the molecular mechanism remains elusive. Several oncogenes induce replication stress, resulting in under replicated DNA and replication continuing into mitosis, where TH588 and TH1579 treatment causes toxicity and incorporation of oxidative damage. Hence, we hypothesized that oncogene-induced replication stress explains the cancer selectivity. To test this, we overexpressed c-Myc in human epithelial kidney cells (HA1EB), resulting in increased proliferation, polyploidy and replication stress. TH588 and TH1579 selectively kill c-Myc overexpressing clones, enforcing the cancer cell selective killing of these compounds. Moreover, the toxicity of TH588 and TH1579 in c-Myc overexpressing cells is rescued by transcription, proteasome or CDK1 inhibitors, but not by nucleoside supplementation. We conclude that the molecular toxicological mechanisms of how TH588 and TH1579 kill c-Myc overexpressing cells have several components and involve MTH1-independent proteasomal degradation of c-Myc itself, c-Myc-driven transcription and CDK activation.},
  language  = {en}
}
@article{DjuzenovaFischerKatzeretal.2021,
  author    = {Djuzenova, Cholpon S. and Fischer, Thomas and Katzer, Astrid and Sisario, Dmitri and Korsa, Tessa and Streussloff, Gudrun and Sukhorukov, Vladimir L. and Flentje, Michael},
  title     = {Opposite effects of the triple target (DNA-PK/PI3K/mTOR) inhibitor PI-103 on the radiation sensitivity of glioblastoma cell lines proficient and deficient in DNA-PKcs},
  series = {BMC Cancer},
  volume    = {21},
  journal   = {BMC Cancer},
  doi       = {10.1186/s12885-021-08930-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265826},
  year      = {2021},
  abstract  = {Background: Radiotherapy is routinely used to combat glioblastoma (GBM). However, the treatment efficacy is often limited by the radioresistance of GBM cells. Methods: Two GBM lines MO59K and MO59J, differing in intrinsic radiosensitivity and mutational status of DNA-PK and ATM, were analyzed regarding their response to DNA-PK/PI3K/mTOR inhibition by PI-103 in combination with radiation. To this end we assessed colony-forming ability, induction and repair of DNA damage by gamma H2AX and 53BP1, expression of marker proteins, including those belonging to NHEJ and HR repair pathways, degree of apoptosis, autophagy, and cell cycle alterations. Results: We found that PI-103 radiosensitized MO59K cells but, surprisingly, it induced radiation resistance in MO59J cells. Treatment of MO59K cells with PI-103 lead to protraction of the DNA damage repair as compared to drug-free irradiated cells. In PI-103-treated and irradiated MO59J cells the foci numbers of both proteins was higher than in the drug-free samples, but a large portion of DNA damage was quickly repaired. Another cell line-specific difference includes diminished expression of p53 in MO59J cells, which was further reduced by PI-103. Additionally, PI-103-treated MO59K cells exhibited an increased expression of the apoptosis marker cleaved PARP and increased subG1 fraction. Moreover, irradiation induced a strong G2 arrest in MO59J cells (similar to 80\% vs. similar to 50\% in MO59K), which was, however, partially reduced in the presence of PI-103. In contrast, treatment with PI-103 increased the G2 fraction in irradiated MO59K cells. Conclusions: The triple-target inhibitor PI-103 exerted radiosensitization on MO59K cells, but, unexpectedly, caused radioresistance in the MO59J line, lacking DNA-PK. The difference is most likely due to low expression of the DNA-PK substrate p53 in MO59J cells, which was further reduced by PI-103. This led to less apoptosis as compared to drug-free MO59J cells and enhanced survival via partially abolished cell-cycle arrest. The findings suggest that the lack of DNA-PK-dependent NHEJ in MO59J line might be compensated by DNA-PK independent DSB repair via a yet unknown mechanism.},
  language  = {en}
}
@article{DjuzenovaFiedlerMemmeletal.2019,
  author    = {Djuzenova, Cholpon S. and Fiedler, Vanessa and Memmel, Simon and Katzer, Astrid and Sisario, Dmitri and Brosch, Philippa K. and G{\"o}hrung, Alexander and Frister, Svenja and Zimmermann, Heiko and Flentje, Michael and Sukhorukov, Vladimir L.},
  title     = {Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells},
  series = {BMC Cancer},
  volume    = {19},
  journal   = {BMC Cancer},
  doi       = {10.1186/s12885-019-5517-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200290},
  pages     = {299},
  year      = {2019},
  abstract  = {Background Most tumor cells show aberrantly activated Akt which leads to increased cell survival and resistance to cancer radiotherapy. Therefore, targeting Akt can be a promising strategy for radiosensitization. Here, we explore the impact of the Akt inhibitor MK-2206 alone and in combination with the dual PI3K and mTOR inhibitor PI-103 on the radiation sensitivity of glioblastoma cells. In addition, we examine migration of drug-treated cells. Methods Using single-cell tracking and wound healing migration tests, colony-forming assay, Western blotting, flow cytometry and electrorotation we examined the effects of MK-2206 and PI-103 and/or irradiation on the migration, radiation sensitivity, expression of several marker proteins, DNA damage, cell cycle progression and the plasma membrane properties in two glioblastoma (DK-MG and SNB19) cell lines, previously shown to differ markedly in their migratory behavior and response to PI3K/mTOR inhibition. Results We found that MK-2206 strongly reduces the migration of DK-MG but only moderately reduces the migration of SNB19 cells. Surprisingly, MK-2206 did not cause radiosensitization, but even increased colony-forming ability after irradiation. Moreover, MK-2206 did not enhance the radiosensitizing effect of PI-103. The results appear to contradict the strong depletion of p-Akt in MK-2206-treated cells. Possible reasons for the radioresistance of MK-2206-treated cells could be unaltered or in case of SNB19 cells even increased levels of p-mTOR and p-S6, as compared to the reduced expression of these proteins in PI-103-treated samples. We also found that MK-2206 did not enhance IR-induced DNA damage, neither did it cause cell cycle distortion, nor apoptosis nor excessive autophagy. Conclusions Our study provides proof that MK-2206 can effectively inhibit the expression of Akt in two glioblastoma cell lines. However, due to an aberrant activation of mTOR in response to Akt inhibition in PTEN mutated cells, the therapeutic window needs to be carefully defined, or a combination of Akt and mTOR inhibitors should be considered.},
  language  = {en}
}
@article{DjuzenovaFiedlerKatzeretal.2016,
  author    = {Djuzenova, Cholpon S. and Fiedler, Vanessa and Katzer, Astrid and Michel, Konstanze and Deckert, Stefanie and Zimmermann, Heiko and Sukhorukov, Vladimir L. and Flentje, Michael},
  title     = {Dual PI3K-and mTOR-inhibitor PI-103 can either enhance or reduce the radiosensitizing effect of the Hsp90 inhibitor NVP-AUY922 in tumor cells: The role of drug-irradiation schedule},
  series = {Oncotarget},
  volume    = {7},
  journal   = {Oncotarget},
  number    = {25},
  doi       = {10.18632/oncotarget.9501},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177770},
  pages     = {38191-38209},
  year      = {2016},
  abstract  = {Inhibition of Hsp90 can increase the radiosensitivity of tumor cells. However, inhibition of Hsp90 alone induces the anti-apoptotic Hsp70 and thereby decreases radiosensitivity. Therefore, preventing Hsp70 induction can be a promising strategy for radiosensitization. PI-103, an inhibitor of PI3K and mTOR, has previously been shown to suppress the up-regulation of Hsp70. Here, we explore the impact of combining PI-103 with the Hsp90 inhibitor NVP-AUY922 in irradiated glioblastoma and colon carcinoma cells. We analyzed the cellular response to drug-irradiation treatments by colony-forming assay, expression of several marker proteins, cell cycle progression and induction/repair of DNA damage. Although PI-103, given 24 h prior to irradiation, slightly suppressed the NVP-AUY922-mediated up-regulation of Hsp70, it did not cause radiosensitization and even diminished the radiosensitizing effect of NVP-AUY922. This result can be explained by the activation of PI3K and ERK pathways along with G1-arrest at the time of irradiation. In sharp contrast, PI-103 not only exerted a radiosensitizing effect but also strongly enhanced the radiosensitization by NVP-AUY922 when both inhibitors were added 3 h before irradiation and kept in culture for 24 h. Possible reasons for the observed radiosensitization under this drug-irradiation schedule may be a down-regulation of PI3K and ERK pathways during or directly after irradiation, increased residual DNA damage and strong G2/M arrest 24 h thereafter. We conclude that duration of drug treatment before irradiation plays a key role in the concomitant targeting of PI3K/mTOR and Hsp90 in tumor cells.},
  language  = {en}
}