Podcasts about h2ax

BUFFALO, NY- May 6, 2024 – A new research paper was published in Oncotarget's Volume 15 on May 3, 2024, entitled, “Transfected SARS-CoV-2 spike DNA for mammalian cell expression inhibits p53 activation of p21(WAF1), TRAIL Death Receptor DR5 and MDM2 proteins in cancer cells and increases cancer cell viability after chemotherapy exposure.” Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and COVID-19 infection has led to worsened outcomes for patients with cancer. SARS-CoV-2 spike protein mediates host cell infection and cell-cell fusion that causes stabilization of tumor suppressor p53 protein. In-silico analysis previously suggested that SARS-CoV-2 spike interacts with p53 directly but this putative interaction has not been demonstrated in cells. In this new study, researchers Shengliang Zhang and Wafik S. El-Deiry from Brown University and Lifespan Health System examined the interaction between SARS-CoV-2 spike, p53 and MDM2 (E3 ligase, which mediates p53 degradation) in cancer cells using an immunoprecipitation assay. “We observed that SARS-CoV-2 spike protein interrupts p53-MDM2 protein interaction but did not detect SARS-CoV-2 spike bound with p53 protein in the cancer cells.” The researchers further observed that SARS-CoV-2 spike suppresses p53 transcriptional activity in cancer cells including after nutlin exposure of wild-type p53-, spike-expressing tumor cells and inhibits chemotherapy-induced p53 gene activation of p21(WAF1), TRAIL Death Receptor DR5 and MDM2. The suppressive effect of SARS-CoV-2 spike on p53-dependent gene activation provides a potential molecular mechanism by which SARS-CoV-2 infection may impact tumorigenesis, tumor progression and chemotherapy sensitivity. In fact, cisplatin-treated tumor cells expressing spike were found to have increased cell viability as compared to control cells. Further observations on γ-H2AX expression in spike-expressing cells treated with cisplatin may indicate altered DNA damage sensing in the DNA damage response pathway. The preliminary observations reported here warrant further studies to unravel the impact of SARS-CoV-2 and its various encoded proteins including spike on pathways of tumorigenesis and response to cancer therapeutics. More efforts should be directed at studying the effects of the SARS-CoV-2 spike and other viral proteins on host DNA damage sensing, response and repair mechanisms. “A goal would be to understand the structural basis for maximal anti-viral immunity while minimizing suppression of host defenses including the p53 DNA damage response and tumor suppression pathway. Such directions are relevant and important including not only in the context of viral infection and mRNA vaccines in general but also for patients with cancer who may be receiving cytotoxic or other cancer treatments.” DOI - https://doi.org/10.18632/oncotarget.28582 Correspondence to - Wafik S. El-Deiry - wafik@brown.edu Sign up for free Altmetric alerts about this article - https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28582 Subscribe for free publication alerts from Oncotarget - https://www.oncotarget.com/subscribe/ About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ MEDIA@IMPACTJOURNALS.COM

BUFFALO, NY- March 25, 2024 – A new #research paper was #published in Oncotarget's Volume 15 on March 14, 2024, entitled, “ABT199/venetoclax synergism with thiotepa enhances the cytotoxicity of fludarabine, cladribine and busulfan in AML cells.” ABT199/venetoclax, an inhibitor of the pro-survival BCL-2 protein, has improved AML treatment. Its efficacy in hematopoietic stem cell transplantation (HSCT), when combined with other chemotherapeutic drugs, has not been thoroughly investigated. In this new study, researchers Benigno C. Valdez, Bin Yuan, David Murray, Jeremy L. Ramdial, Uday Popat, Yago Nieto, and Borje S. Andersson from The University of Texas MD Anderson Cancer Center and the University of Alberta demonstrate the synergistic cytotoxicity of ABT199/venetoclax with the DNA alkylator thiotepa (Thio) in AML cells. “The results may provide relevant information for the design of clinical trials using these drugs to circumvent recognized drug-resistance mechanisms when used as part of pre-transplant conditioning regimens for AML patients undergoing allogenic HSCT.” Cleavage of Caspase 3, PARP1 and HSP90, as well as increased Annexin V positivity, suggest potent activation of apoptosis by this two-drug combination; increased levels of γ-H2AX, P-CHK1 (S317), P-CHK2 (S19) and P-SMC1 (S957) indicate an enhanced DNA damage response. Likewise, the increased level of P-SAPK/JNK (T183/Y185) and decreased P-PI3Kp85 (Y458) suggest enhanced activation of stress signaling pathways. These molecular readouts were synergistically enhanced when ABT199/venetoclax and Thio were combined with fludarabine, cladribine and busulfan. The five-drug combination decreased the levels of BCL-2, BCL-xL and MCL-1, suggesting its potential clinical relevance in overcoming ABT199/venetoclax resistance. Moreover, this combination is active against P53-negative and FLT3-ITD-positive cell lines. Enhanced activation of apoptosis was observed in leukemia patient-derived cell samples exposed to the five-drug combination, suggesting a clinical relevance. “The results provide a rationale for clinical trials using these two- and five-drug combinations as part of a conditioning regimen for AML patients undergoing HSCT.” DOI - https://doi.org/10.18632/oncotarget.28563 Correspondence to - Benigno C. Valdez - mbalasik@yahoo.com Sign up for free Altmetric alerts about this article - https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28563 Subscribe for free publication alerts from Oncotarget - https://www.oncotarget.com/subscribe/ Keywords - cancer, acute myeloid leukemia, aml, pre-transplant regimens, venetoclax, thiotepa, busulfan About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. Oncotarget is indexed and archived by PubMed/Medline, PubMed Central, Scopus, EMBASE, META (Chan Zuckerberg Initiative) (2018-2022), and Dimensions (Digital Science). To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Spotify - https://open.spotify.com/show/0gRwT6BqYWJzxzmjPJwtVh Media Contact MEDIA@IMPACTJOURNALS.COM 18009220957

A new research paper was published in Aging (Aging-US) Volume 15, Issue 11, entitled, “Senescence and senotherapies in biliary atresia and biliary cirrhosis.” Premature senescence occurs in adult hepatobiliary diseases and worsens the prognosis through deleterious liver remodeling and hepatic dysfunction. Senescence might also arise in biliary atresia (BA), the first cause of pediatric liver transplantation. Alternatives to transplantation are needed. In this new study, researchers Giulia Jannone, Eliano Bonaccorsi Riani, Catherine de Magnée, Roberto Tambucci, Jonathan Evraerts, Joachim Ravau, Pamela Baldin, Caroline Bouzin, Axelle Loriot, Laurent Gatto, Anabelle Decottignies, Mustapha Najimi, and Etienne Marc Sokal from the Université catholique de Louvain in Brussels, Belgium, aimed to investigate premature senescence in BA and to assess senotherapies in a preclinical model of biliary cirrhosis. “As there is a need for new therapies to avoid or delay liver transplantation in pediatric biliary cirrhosis, the aim of our work was to investigate premature senescence in BA through a multi-technical approach and to assess senotherapies in a preclinical model of biliary cirrhosis.” BA liver tissues were prospectively obtained at hepatoportoenterostomy (n=5) and liver transplantation (n=30) and compared to controls (n=10). Senescence was investigated through spatial whole transcriptome analysis, SA-β-gal activity, p16 and p21 expression, γ-H2AX and senescence-associated secretory phenotype (SASP). Human allogenic liver-derived progenitor cells (HALPC) or dasatinib and quercetin (D+Q) were administered to two-month-old Wistar rats after bile duct ligation (BDL). Advanced premature senescence was evidenced in BA livers from early stage and continued to progress until liver transplantation. Senescence and SASP were predominant in cholangiocytes, but also present in surrounding hepatocytes. HALPC but not D+Q reduced the early marker of senescence p21 in BDL rats and improved biliary injury (serum γGT and Sox9 expression) and hepatocytes mass loss (Hnf4a). “BA livers displayed advanced cellular senescence at diagnosis that continued to progress until liver transplantation. HALPC reduced early senescence and improved liver disease in a preclinical model of BA, providing encouraging preliminary results regarding the use of senotherapies in pediatric biliary cirrhosis.” DOI - https://doi.org/10.18632/aging.204700 Corresponding author - Giulia Jannone - giulia.jannone@uclouvain.be Sign up for free Altmetric alerts about this article - https://aging.altmetric.com/details/email_updates?id=10.18632%2Faging.204700 Subscribe for free publication alerts from Aging - https://www.aging-us.com/subscribe-to-toc-alerts Keywords - aging, senescence, senotherapy, liver, biliary cirrhosis, biliary atresia About Aging-US Launched in 2009, Aging-US publishes papers of general interest and biological significance in all fields of aging research and age-related diseases, including cancer—and now, with a special focus on COVID-19 vulnerability as an age-dependent syndrome. Topics in Aging-US go beyond traditional gerontology, including, but not limited to, cellular and molecular biology, human age-related diseases, pathology in model organisms, signal transduction pathways (e.g., p53, sirtuins, and PI-3K/AKT/mTOR, among others), and approaches to modulating these signaling pathways. Please visit our website at https://www.Aging-US.com​​ and connect with us: SoundCloud - https://soundcloud.com/Aging-Us Facebook - https://www.facebook.com/AgingUS/ Twitter - https://twitter.com/AgingJrnl Instagram - https://www.instagram.com/agingjrnl/ YouTube - https://www.youtube.com/@AgingJournal LinkedIn - https://www.linkedin.com/company/aging/ Pinterest - https://www.pinterest.com/AgingUS/ Media Contact 18009220957 MEDIA@IMPACTJOURNALS.COM

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.11.24.517673v1?rss=1 Authors: Stylianakis, E., Festenstein, R., Vannier, J.-B. Abstract: TElomeric Repeat-containing RNA are long non-coding RNAs generated from the telomeres. TERRAs are essential for the establishment of heterochromatin marks at telomeres, which serve for the binding of Heterochromatin Protein 1 (HP1), a protein family of epigenetic modifiers involved with chromatin compaction and gene silencing. While HP1{gamma} is enriched on gene bodies of actively transcribed human and mouse genes, it is unclear if its transcriptional role is important for HP1{gamma} function in telomere cohesion and telomere maintenance. We aimed to study the effect of mouse HP1{gamma} on the transcription of telomere factors and molecules that can affect telomere maintenance. We investigated the telomere function of HP1{gamma} by using deficient mouse embryonic fibroblasts (MEFs) deriving from 13.5 embryonic day embryos compared to their litter mate controls. We used gene expression analysis of HP1{gamma} deficient MEFs and validated the molecular and mechanistic consequences of HP1{gamma} loss by telomere FISH, immunofluorescence, RT-qPCR and DNA-RNA Immunoprecipitation (DRIP). Loss of HP1{gamma} in primary MEFs leads to a downregulation of various telomere and telomere-accessory transcripts, including shelterin protein TRF1. Its downregulation is associated with increased telomere replication stress and DNA damage ({gamma}H2AX), effects more profound in females. We suggest that the source for the impaired telomere maintenance is a consequence of increased telomeric DNA-RNA hybrids and TERRAs arising at and from mouse chromosomes 18 and X. Our results suggest an important transcriptional control by mouse HP1{gamma} of various telomere factors including TRF1 protein and TERRAs that has profound consequences on telomere stability, with a potential sexually dimorphic nature. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.25.513730v1?rss=1 Authors: Rossi, M., Anerillas, C., Idda, M. L., Munk, R., Shin, C. H., Donega, S., Tsitsipatis, D., Herman, A. B., Martindale, J. L., Yang, X., Piao, Y., Mazan-Mamczarz, K., Fan, J., Ferrucci, L., De, S., Abdelmohsen, K., Gorospe, M. Abstract: Senescent cells release a variety of cytokines, proteases, and growth factors collectively known as the senescence-associated secretory phenotype (SASP). Sustained SASP contributes to a pattern of chronic inflammation associated with aging and implicated in many age-related diseases. Here, we investigated the expression and function of the immunomodulatory cytokine BAFF (B-cell activating factor), a SASP protein, in multiple senescence models. We first characterized BAFF production across different senescence models, including senescent human diploid fibroblasts (WI-38, IMR-90) and monocytic leukemia cells (THP-1), and tissues of mice induced to undergo senescence. We then identified IRF1 (interferon response factor 1) as a transcription factor required for promoting BAFF mRNA transcription in senescence. We discovered that suppressing BAFF production decreased the senescent phenotype of both fibroblasts and monocyte-derived THP-1 cells, overall reducing IL6 secretion, SA-{beta}-Gal staining, and {gamma}-H2AX accumulation. Importantly, however, the influence of BAFF on the senescence program was cell type-specific: in monocytes, BAFF promoted the early activation of NF-{kappa}B and general SASP secretion, while in fibroblasts, BAFF contributed to the production and function of TP53 (p53). We propose that BAFF is elevated across senescence models and is a potential target for senotherapy. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.07.321927v1?rss=1 Authors: Vicar, T., Gumulec, J., Kolar, R., Kopecna, O., Pagacova, E., Falk, M. Abstract: DNA double-strand breaks, marked by Ionizing Radiation-Induced (Repair) Foci (IRIF), are the most serious DNA lesions, dangerous to human health. IRIF quantification based on confocal microscopy represents the most sensitive and gold standard method in radiation biodosimetry and allows research of DSB induction and repair at the molecular and a single cell level. In this study, we introduce DeepFoci - a deep learning-based fully-automatic method for IRIF counting and its morphometric analysis. DeepFoci is designed to work with 3D multichannel data (trained for 53BP1 and {gamma}H2AX) and uses U-Net for the nucleus segmentation and IRIF detection, together with maximally stable extremal region-based IRIF segmentation. The proposed method was trained and tested on challenging datasets consisting of mixtures of non-irradiated and irradiated cells of different types and IRIF characteristics - permanent cell lines (NHDF, U-87) and cell primary cultures prepared from tumors and adjacent normal tissues of head and neck cancer patients. The cells were dosed with 1-4 Gy gamma-rays and fixed at multiple (0-24 h) post-irradiation times. Upon all circumstances, DeepFoci was able to quantify the number of IRIF foci with the highest accuracy among current advanced algorithms. Moreover, while the detection error of DeepFoci remained comparable to the variability between two experienced experts, the software kept its sensitivity and fidelity across dramatically different IRIF counts per nucleus. In addition, information was extracted on IRIF 3D morphometric features and repair protein colocalization within IRIFs. This allowed multiparameter IRIF categorization, thereby refining the analysis of DSB repair processes and classification of patient tumors with a potential to identify specific cell subclones. The developed software improves IRIF quantification for various practical applications (radiotherapy monitoring, biodosimetry, etc.) and opens the door to an advanced DSB focus analysis and, in turn, a better understanding of (radiation) DNA damaging and repair. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.11.245969v1?rss=1 Authors: Szikriszt, B., Poti, A., Nemeth, E., Kanu, N., Swanton, C., Szuts, D. Abstract: Platinum-based drugs are a mainstay of cancer chemotherapy. However, their mutagenic effect can increase tumour heterogeneity, contribute to the evolution of treatment resistance, and also induce secondary malignancies. We coupled whole genome sequencing with phenotypic investigations on two cell line models to compare the magnitude and understand the mechanism of mutagenicity of cisplatin, carboplatin and oxaliplatin. Cisplatin induced significantly more base substitution mutations than carboplatin or oxaliplatin when used at equitoxic concentrations on human TK6 or chicken DT40 cells, and also induced the highest number of short insertions and deletions. Assessment through histone H2AX phosphorylation and single cell agarose gel electrophoresis suggested that cisplatin caused more DNA damage than carboplatin or oxaliplatin. The analysis of base substitution spectra revealed that all three tested platinum drugs elicit both a direct mutagenic effect at purine dinucleotides, and an indirect effect of accelerating endogenous mutagenic processes. Whereas the direct mutagenic effect correlated with the level of DNA damage caused, the indirect mutagenic effects were equal. The different mutagenicity and DNA damaging effect of equitoxic platinum drug treatments suggests that DNA damage independent mechanisms significantly contribute to their cytotoxicity. Thus, the comparatively high mutagenicity of cisplatin should be taken into account in the design of chemotherapeutic regimens. Copy rights belong to original authors. Visit the link for more info

Human papillomavirus confers radiosensitivity in oropharyngeal cancer cells The cover for issue 16 of Oncotarget features Figure 6, "Radiation-induced DNA damage measured by γ-H2AX foci formation at a specified time point after 10 Gy irradiation," by Zhang, et al. HPV-negative UM-SCC4 with and without transfection of HPV E6 oncoprotein, HPV-negative UPCI-SCC-089, and HPV-positive UPCI-SCC-099 cell lines were used in this study. The survival fraction after 10 Gy was significantly lower for the HPV-positive SCC-099 cells than for the HPV-negative cells. In contrast, the HPV-positive UPCI-SCC-099 cells displayed persistent -H2AX activity; the expression of -H2AX remained high at 48 hours post-radiation. HPV-positive SCC-099 cells were more likely to show the classical apoptotic changes of increased cell thickness and increased motility after radiation. Dr. Angela Hong from The Faculty of Medicine and Health, Central Clinical School at The University of Sydney as well as The Department of Radiation Oncology, Chris O’Brien Lifehouse said, "Human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPSCC) is clinically and biologically distinct from smoking-related (HPV-negative) OPSCC." The overall better prognosis seen in HPV-positive OPSCC may be related to the disease's response to radiation therapy. Radiation therapy plays an important role in the management of OPSCC, either as definitive therapy or as adjuvant therapy after surgery. Cellular response to radiation treatment can be observed with a label-free dynamic Holo Monitor, which allows non-invasive visualization and live-cell analysis of radiation responses and the migration potential of cancer cells. The Hong Research Team concluded in their Oncotarget Research Paper that the enhanced cell motility is due to disruption of the actin-membrane interactions by radiation, initiating the membrane blubbing and generating force to enhance cell motility. In contrast, the HPV-negative UPCI-SCC-089 cells exhibited cell flattening and enlargement, which are the common cytological features of cell cycle blockage. DOI - https://doi.org/10.18632/oncotarget.27535 Full text - https://www.oncotarget.com/article/27535/text/ Correspondence to - Matthew H. Taylor - taylmatt@ohsu.edu Keywords - radiosensitivity, oropharyngeal cancer, human papillomavirus, double-strand break, radiobiology About Oncotarget Oncotarget is a weekly, peer-reviewed, open access biomedical journal covering research on all aspects of oncology. To learn more about Oncotarget, please visit https://www.oncotarget.com or connect with: SoundCloud - https://soundcloud.com/oncotarget Facebook - https://www.facebook.com/Oncotarget/ Twitter - https://twitter.com/oncotarget LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Oncotarget is published by Impact Journals, LLC please visit http://www.ImpactJournals.com or connect with @ImpactJrnls Media Contact MEDIA@IMPACTJOURNALS.COM 18009220957x105

Durch Fehler entstandene tetraploide Zellen sind chromosomal instabil und können zu Zelltransformation führen. Die Beweise verdichten sich, dass die Propagation von tetraploiden Säugetierzellen durch einen p53-vermittelten Arrest eingeschränkt wird; jedoch ist weiterhin unklar, was die Ursache dieses p53-vermittelten Arrests ist. Um die Ursache des p53-vermittelten Arrests zu identifizieren, wurden individuelle Zellen mittels zeitraffender Mikroskopie in Echtzeit verfolgt. Neu entstandene tetraploide Zellen können einen Zellzyklus vollenden, aber die Mehrzahl der Zellen starb oder verharrte in einem Arrest in der folgenden G1-Phase, abhängig davon ob die vorangegangene Mitose fehlerfrei verlief oder nicht. Tochterzellen, denen eine fehlerhafte Mitose voranging, akkumulierten p53 im Zellkern, was zum Zelltod oder einem irreversiblen Zellzyklusarrest führte. Es zeigte sich durch den Anstieg von 8-OHdG, einem Indikator für oxidative DNA Schädigung, dass tetraploide Zellen durch die vermehrten fehlerhaften Mitosen höheren Konzentrationen von reaktiven oxidativen Spezien (ROS) ausgesetzt sind. Der Anstieg von 8-OHdG korrelierte mit der p53-Akkumulation im Zellkern. Da keine vermehrte Phosphorylierung des Histons H2AX (γ-H2AX), ein Marker für DNA-Strangbrüche, detektiert wurde, lässt sich schlussfolgern, dass ROS entscheidend für den p53 vermittelten Arrest verantwortlich sind. Mehrere p53-aktivierende Kinasen wurden mittels RNA Interferenz (RNAi) und chemischer Genetik untersucht, ob sie einen Einfluss auf den Zellzyklusarrest von tetraploiden Zellen haben. Von den getesteten Kinasen hatte nur ATM einen Einfluss auf die Aktivierung von p53 nach fehlerhaften tetraploiden Mitosen. Zwar wird ATM in der Regel durch DNA-Schäden aktiviert, jedoch wurde bereits zuvor gezeigt, dass ATM auch durch erhöhte ROS Konzentrationen aktiviert werden kann. Um die Zusammenhänge des Zellzyklusarrests weiter aufzuklären, wurde ein genomübergreifender esiRNA Screen etabliert, der die Zellproliferation nach induzierter Tetraploidisierung analysiert. Durch Kombination der Zellzyklusanalyse an Hand des DNA-Gehalts zusammen mit den FUCCI-Zellzyklusindikatoren, konnten tetraploide und diploide Zellen nebeneinander mikroskopisch analysiert werden, ohne zuvor tetraploide und diploide Zellen isolieren zu müssen. Dieser neue experimentelle Ansatz ermöglichte die Identifikation von Genen, die spezifisch die Proliferation von tetraploiden Zellen verstärken oder einschränken Im Primärscreen wurden 1159 Gene identifiziert, deren Inhibition die Proliferation einschränken. Weiter wurden 431 Gene identifiziert, deren Inhibition die Proliferation der tetraploiden Zellen verstärken. Von den 431 Genen, deren Inhibition die Proliferation verstärken, wurden 371 Gene einem Konfirmationsscreen unterzogen, in dem 158 der identifizierten 371 Gene bestätigt wurden. Die bioinformatische Analyse der 158 Gene zeigte eine signifikante Anhäufung von Genen, die mit DNA-Replikation, dem kanonischen Wnt-Signalweg oder mit Tumorsignalwegen assoziiert sind. Unter letzteren ist CCDC6 sehr interessant, da dessen Genprodukt durch ATM phosphoryliert wird und nachgeschaltet den Tumorsuppressor 14-3-3σ reguliert. Des weiteren wurden mittels einer Meta Analyse der Ergebnisse des Primärscreens, zusammen mit den Daten aus dem “Project Achilles”, welches genomweit den Effekt von shRNA-vermittelter Geninhibition auf die Proliferation von 108 Krebszelllinien untersuchte, 18 Gene identifiziert, deren Inhibition sowohl die Proliferation von tetraploiden Zellen einschränkt, als auch die Proliferation von Zelllinien hemmt, welche von Krebsarten stammen, die zu meist chromosomale Instabilitäten (CIN) aufweisen. Damit bilden die präsentierten Daten nicht nur eine gute Basis zur Aufklärung des Zellzyklusarrests tetraploider Zellen, sondern auch für die Identifikation neuer potentieller Zielmoleküle, welche benutzt werden können um Tumorerkrankungen mit chromosomaler Instabilität zu behandeln, welche häufig resistent gegen die bislang verfügbaren Behandlungen sind.

Background: Radiation-induced alterations in posttranslational histone modifications (PTMs) may affect the cellular response to radiation damage in the DNA. If not reverted appropriately, altered PTM patterns may cause long-term alterations in gene expression regulation and thus lead to cancer. It is therefore important to characterize radiation-induced alterations in PTM patterns and the factors affecting them. Methods: A lymphoblastoid cell line established from a normal donor was used to screen for alterations in methylation levels at H3K4, H3K9, H3K27, and H4K20, as well as acetylation at H3K9, H3K56, H4K5, and H4K16, by quantitative Western Blot analysis at 15 min, 1 h and 24 h after irradiation with 2 Gy and 10 Gy. The variability of alterations in acetylation marks was in addition investigated in a panel of lymphoblastoid cell lines with differing radiosensitivity established from lung cancer patients. Results: The screening procedure demonstrated consistent hypomethylation at H3K4me3 and hypoacetylation at all acetylation marks tested. In the panel of lymphoblastoid cell lines, however, a high degree of inter-individual variability became apparent. Radiosensitive cell lines showed more pronounced and longer lasting H4K16 hypoacetylation than radioresistant lines, which correlates with higher levels of residual gamma-H2AX foci after 24 h. Conclusion: So far, the factors affecting extent and duration of radiation-induced histone alterations are poorly defined. The present work hints at a high degree of inter-individual variability and a potential correlation of DNA damage repair capacity and alterations in PTM levels.

Mon, 30 Jan 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/14079/ https://edoc.ub.uni-muenchen.de/14079/1/Seiler_Doris.pdf Seiler, Doris ddc:570, ddc:500, Fakul

Fri, 17 Jul 2009 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/10628/ https://edoc.ub.uni-muenchen.de/10628/1/Schulz_Vanessa.pdf Schulz, Vanessa ddc:5

Recent work has underlined the importance of animal models in discovery and characterisation of molecular mechanisms determining radiosensitivity and radioresistance. Enhanced sensitivity of LEC rats to ionizing radiation in terms of the acute radiation syndrome was investigated in the present work on the cellular level and compared to that of LE rats. To understand the molecular basis for the increased radiation sensitivity a series of studies were performed, which included the classical clonogenic survival assay, investigation of double strand break repair by means of PFGE and gH2AX evaluation, comet assay for evaluation of repair of single strand breaks and alkaline labile sites, and analysis of cell cycle progression of asynchronous fibroblast population. Survival assay, PFGE, and H2AX analysis were performed in a standardised experimental system - confluent fibroblasts, synchronized in G1 phase of cell cycle, and comet assays were performed in G0 lymphocytes. The data suggests a mild radiosensitization of LEC fibroblasts compared to LE. The results of studies using the selected model did not reflect the degree of animal sensitivity on the molecular level, since values of dose modifying factor (DMF) were much lower in fibroblasts (DMF2 = 1.32) compared to that of animal sensitivity (DMF = 2.36 for bone marrow syndrome (LD50/30) and DMF = 1.95 of intestinal death (LD50/7)). The investigation of DNA repair and cell cycle did not reveal a significant defect in the studied pathways in synchronized fibroblasts and cell cycle progression was not different from wild type cells. The presented data contradict the published LEC cellular phenotype. Of the possible candidate genes, which are located in the radiosensitivity locus, several were further analysed. Among those, Gata-2 appeared to be the most promising of the positional and functional candidates. However, no mutation in the coding sequence could be identified and mRNA expression levels were similar between control and LEC cells. The presented data suggests that radiosensitivity of LEC rats might be attributed to a mechanism specific for certain target tissue, like bone marrow, or enhanced in cell cycle stages other than G0/G1.