1,723,647 research outputs found
FMU 5461
No full textEn onämnd (electus Arvid Kurck) till en domprost (Hemming Gadh?) angående realiserandet av avkastningen från dennes prebende vid Åbo domkyrka samt med hälsning till ärkedjäknen Vernerus (Nicolai) och en magister Henricus (Nicolai?) samt andra vänner.Koncept, av fukt mycket skadat och därför svårtytt.Regesta (content description) and physical description from R. Hausen, Finlands medeltidsurkunder. Spelling modernised by the Diplomatarium Fennicum project.One leaf contains drafts of two documents (FMU 5460 and 5461). FMU 5461 is on the verso side
CX-5461 activates the DNA damage response and demonstrates therapeutic efficacy in high-grade serous ovarian cancer
No full textAcquired resistance to PARP inhibitors (PARPi) is a major challenge for the clinical management of high grade serous ovarian cancer (HGSOC). Here, we demonstrate CX-5461, the first-in-class inhibitor of RNA polymerase I transcription of ribosomal RNA genes (rDNA), induces replication stress and activates the DNA damage response. CX-5461 co-operates with PARPi in exacerbating replication stress and enhances therapeutic efficacy against homologous recombination (HR) DNA repair-deficient HGSOC-patient-derived xenograft (PDX) in vivo. We demonstrate CX-5461 has a different sensitivity spectrum to PARPi involving MRE11-dependent degradation of replication forks. Importantly, CX-5461 exhibits in vivo single agent efficacy in a HGSOC-PDX with reduced sensitivity to PARPi by overcoming replication fork protection. Further, we identify CX-5461-sensitivity gene expression signatures in primary and relapsed HGSOC. We propose CX-5461 is a promising therapy in combination with PARPi in HR-deficient HGSOC and also as a single agent for the treatment of relapsed disease.Full Tex
CX-5461 Preferentially Induces Top2α-Dependent DNA Breaks at Ribosomal DNA Loci
No full textWhile genotoxic chemotherapeutic agents are among the most effective tools to combat cancer, they are often associated with severe adverse effects caused by indiscriminate DNA damage in non-tumor tissue as well as increased risk of secondary carcinogenesis. This study builds on our previous work demonstrating that the RNA Polymerase I (Pol I) transcription inhibitor CX-5461 elicits a non-canonical DNA damage response and our discovery of a critical role for Topoisomerase 2α (Top2α) in the initiation of Pol I-dependent transcription. Here, we identify Top2α as a mediator of CX-5461 response in the murine Eµ-Myc B lymphoma model whereby sensitivity to CX-5461 is dependent on cellular Top2α expression/activity. Most strikingly, and in contrast to canonical Top2α poisons, we found that the Top2α-dependent DNA damage induced by CX-5461 is preferentially localized at the ribosomal DNA (rDNA) promoter region, thereby highlighting CX-5461 as a loci-specific DNA damaging agent. This mechanism underpins the efficacy of CX-5461 against certain types of cancer and can be used to develop effective non-genotoxic anticancer drugs
Investigating the p53-independent responses to inhibition of RNA Polymerase I transcription by CX-5461
Get PDF© 2017 Dr. Jaclyn QuinIncreased rates of DNA-dependent RNA Polymerase I (Pol I) transcription of the 47S pre-ribosomal RNA (rRNA) genes are observed in almost all cancer types. Cancer cells may require high rates of Pol I transcription and ribosome biogenesis to achieve their unrestrained growth and proliferative capacity, thus presenting a therapeutic window for selectively targeting cancer cells with inhibitors of Pol I transcription. Our laboratory helped develop and validate a first-in-class small molecule selective inhibitor of Pol I transcription, CX-5461 (Senhwa Biosciences). Here, we have investigated the response of cells at defined stages of malignant transformation to inhibition of Pol I transcription, utilising a panel of isogenically matched BJ fibroblast cell lines.
We compared the response of non-transformed and transformed cells of the same genetic background, and demonstrated that CX-5461 can selectively induce cell death in cancer cell lines in vitro. We investigated the phenotypic response of a nontransformed BJ fibroblast cell line minimally immortalized with hTERT (BJ-T) to CX- 5461, and demonstrated that they display a proliferation defect. The proliferation defect is associated with the activation of p53 and a p53-dependent G1 cell cycle checkpoint, as well as p53-independent S-phase and G2 cell cycle checkpoints and senescence. Escape from cell cycle arrest in transformed BJ fibroblast cell lines is associated with increased rates of cell death in response to CX-5461.
To identify pathways mediating the p53-independent responses to inhibition of Pol I transcription, we have performed RNA-sequencing analysis in CX-5461 treated BJ-T cells in which p53 was silenced (BJ-T p53shRNA). The analysis identified ATM (Ataxia-telangiectasia mutated) / ATR (ATM and RAD3-related) signaling and transcriptional programs associated with senescence to be modulated following treatment with CX-5461. Further, we have demonstrated that inhibition of Pol I transcription by CX-5461 rapidly and potently activates the ATM/ATR kinase signaling pathways in the absence of global DNA damage. Combined ATM/ATR inhibition and CX-5461 treatment results in bypass of CX-5461 mediated S-phase and G2 arrest, and induced cell death in the BJ-T p53shRNA cell line.
We investigated the mechanisms by which inhibition of Pol I transcription by CX-5461 activates the ATM/ATR signaling pathways. We demonstrated that inhibition of Pol I transcription initiation by CX-5461 results in ‘exposed’ rRNA genes (rDNA) that are in an open chromatin conformation but devoid of Pol I. Inhibition of Pol I transcription by CX-5461 also results in reorganization of nucleolar structure and translocation of proteins to and from the nucleoli. We observed increased levels of NBS1 (Nijmegen Breakage Syndrome 1) activation by ATM specifically within the nucleoli during S/G2. We propose CX-5461 treatment induces an unusual chromatin structure at the rDNA that is sufficient to activate ATM/ATR in the nucleoli. Finally, we have shown that DNA damage repair is attenuated following treatment with CX-5461. Together, our studies identify activation of ATM/ATR signaling as a key p53-independent pathway of response to inhibition of Pol I transcription, that can be targeted to improve the efficacy of CX-5461 in cancer therapy
Inhibition of RNA polymerase I transcription initiation by CX-5461 activates non-canonical ATM/ATR signaling
No full textRNA polymerase I (Pol I)-mediated transcription of the ribosomal RNA genes (rDNA) is confined to the nucleolus and is a rate-limiting step for cell growth and proliferation. Inhibition of Pol I by CX-5461 can selectively induce p53-mediated apoptosis of tumour cells in vivo. Currently, CX-5461 is in clinical trial for patients with advanced haematological malignancies (Peter Mac, Melbourne). Here we demonstrate that CX-5461 also induces p53-independent cell cycle checkpoints mediated by ATM/ATR signaling in the absence of DNA damage. Further, our data demonstrate that the combination of drugs targeting ATM/ATR signaling and CX-5461 leads to enhanced therapeutic benefit in treating p53-null tumours in vivo, which are normally refractory to each drug alone. Mechanistically, we show that CX-5461 induces an unusual chromatin structure in which transcriptionally competent relaxed rDNA repeats are devoid of transcribing Pol I leading to activation of ATM signaling within the nucleoli. Thus, we propose that acute inhibition of Pol transcription initiation by CX-5461 induces a novel nucleolar stress response that can be targeted to improve therapeutic efficacy
The primary mechanism of cytotoxicity of the chemotherapeutic agent CX-5461 is topoisomerase II poisoning
No full text© 2020 National Academy of Sciences. All rights reserved. Small molecules can affect many cellular processes. The disambiguation of these effects to identify the causative mechanisms of cell death is extremely challenging. This challenge impacts both clinical development and the interpretation of chemical genetic experiments. CX-5461 was developed as a selective RNA polymerase I inhibitor, but recent evidence suggests that it may cause DNA damage and induce G-quadraplex formation. Here we use three complimentary data mining modalities alongside biochemical and cell biological assays to show that CX-5461 exerts its primary cytotoxic activity through topoisomerase II poisoning. We then show that acquired resistance to CX-5461 in previously sensitive lymphoma cells confers collateral resistance to the topoisomerase II poison doxorubicin. Doxorubicin is already a frontline chemotherapy in a variety of hematopoietic malignancies, and CX-5461 is being tested in relapse/refractory hematopoietic tumors. Our data suggest that the mechanism of cell death induced by CX-5461 is critical for rational clinical development in these patients. Moreover, CX-5461 usage as a specific chemical genetic probe of RNA polymerase I function is challenging to interpret. Our multimodal data-driven approach is a useful way to detangle the intended and unintended mechanisms of drug action across diverse essential cellular processes
CX-5461 potentiates imatinib-induced apoptosis in K562 cells by stimulating KIF1B expression
No full textThe selective RNA polymerase I inhibitor CX-5461 has been shown to be effective in treating some types of leukemic disorders. Emerging evidence suggests that combined treatments with CX-5461 and other chemotherapeutic agents may achieve enhanced effectiveness as compared to monotherapies. In the present study, we tested whether CX-5461 could potentiate the effect of imatinib in the human chronic myeloid leukemia cell line K562. Cells were divided into 3 treatment groups (with 3 independent biological replications in each group): control, imatinib (100 nM for 48 hr) alone, and imatinib+CX-5461 (100 nM for 48 hr). Genome-wide mRNA sequencing was performed.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Inhibition of RNA polymerase I transcription initiation by CX-5461 activates non-canonical ATM/ATR signaling
Get PDFRNA polymerase I (Pol I)-mediated transcription of the ribosomal RNA genes (rDNA) is confined to the nucleolus and is a rate-limiting step for cell growth and proliferation. Inhibition of Pol I by CX-5461 can selectively induce p53-mediated apoptosis of tumour cells in vivo. Currently, CX-5461 is in clinical trial for patients with advanced haematological malignancies (Peter Mac, Melbourne). Here we demonstrate that CX-5461 also induces p53-independent cell cycle checkpoints mediated by ATM/ATR signaling in the absence of DNA damage. Further, our data demonstrate that the combination of drugs targeting ATM/ATR signaling and CX-5461 leads to enhanced therapeutic benefit in treating p53-null tumours in vivo, which are normally refractory to each drug alone. Mechanistically, we show that CX-5461 induces an unusual chromatin structure in which transcriptionally competent relaxed rDNA repeats are devoid of transcribing Pol I leading to activation of ATM signaling within the nucleoli. Thus, we propose that acute inhibition of Pol transcription initiation by CX-5461 induces a novel nucleolar stress response that can be targeted to improve therapeutic efficacy
Table1_A transcriptional program associated with cell cycle regulation predominates in the anti-inflammatory effects of CX-5461 in macrophage.DOCX
No full textCX-5461, a novel selective RNA polymerase I inhibitor, shows potential anti-inflammatory and immunosuppressive activities. However, the molecular mechanisms underlying the inhibitory effects of CX-5461 on macrophage-mediated inflammation remain to be clarified. In the present study, we attempted to identify the systemic biological processes which were modulated by CX-5461 in inflammatory macrophages. Primary peritoneal macrophages were isolated from normal Sprague Dawley rats, and primed with lipopolysaccharide or interferon-γ. Genome-wide RNA sequencing was performed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases were used for gene functional annotations. Enrichment analysis was conducted using the ClusterProfiler package of R software. We found that CX-5461 principally induced a molecular signature related to cell cycle inhibition in primed macrophages, featuring downregulation of genes encoding cell cycle mediators and concomitant upregulation of cell cycle inhibitors. At the same concentration, however, CX-5461 did not induce a systemic anti-inflammatory transcriptional program, although some inflammatory genes such as IL-1β and gp91phox NADPH oxidase were downregulated by CX-5461. Our data further highlighted a central role of p53 in orchestrating the molecular networks that were responsive to CX-5461 treatment. In conclusion, our study suggested that limiting cell proliferation predominated in the inhibitory effects of CX-5461 on macrophage-mediated inflammation.</p
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