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Much like replicative senescence, the irreversible cell-cycle arrest induced by eroded telomeres, accelerated senescence occurs when replicative cells suffer irreparable DNA double-strand breaks (DSBs). Along with apoptosis and necrosis, senescence is a desirable outcome in cancer treatment with ionizing radiation (IR) or chemotherapy. In both normal and cancer cells, DSBs promote the assembly of IR-induced foci (IRIF), domains of modified chromatin that serve a key role in DNA damage signaling. IRIF persistence is a critical determinant of accelerated senescence, making drugs that promote persistent IRIF an attractive strategy to sensitize cancer to genotoxic therapy. As an IRIF reporter, we have expressed an inducible green fluorescent protein (GFP) fusion to the IRIF-binding domain (IBD) of 53BP1 (GFP-IBD) in the breast cancer cell line MCF7. Within minutes of exposure to IR, the GFP-IBD relocalizes to form fluorescent nuclear foci, which disperse within several hours. A pair of high-content screening assays for IRIF formation and persistence were established in multiwell plates based on imaging and quantifying GFP-IBD foci per Hoechst-stained MCF7 nucleus at 2 hours and 24 hours. Using the ataxia telangiectasia-mutated inhibitor CGK733 to block IRIF formation and the topoisomerase II inhibitor etoposide to prevent IRIF resolution, we obtained a Z' >0.8 both for IRIF formation at 2 hours and IRIF persistence at 24 hours. Screening the diverse drugs and natural products in the National Cancer Institute Developmental Therapeutics Program Approved Oncology Drugs Set, the National Institutes of Health Clinical Collection, and the MicroSource Spectrum Collection yielded multiple hits that significantly delayed IRIF resolution. Secondary screening suggested some of these otherwise nontoxic drugs also enhance accelerated senescence, indicating strong potential for their repurposing as radiation sensitizers to improve the efficacy of cancer therapy.
Pubmed ID: 26097382
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Portal for preclinical information and research materials, including web-accessible data and tools, NCI-60 Tumor Cell Line Screen, compounds in vials and plates, tumor cells, animals, and bulk drugs for investigational new drug (IND)-directed studies. DTP has been involved in the discovery or development of more than 70 percent of the anticancer therapeutics on the market today, and will continue helping the academic and private sectors to overcome various therapeutic development barriers, particularly through supporting high-risk projects and therapeutic development for rare cancers. Initially DTP made its drug discovery and development services and the results from the human tumor cell line assay publicly accessible to researchers worldwide. At first, the site offered in vitro human cell line data for a few thousand compounds and in vitro anti-HIV screening data for roughly 42,000 compounds. Today, visitors can find: * Downloadable in vitro human tumor cell line data for some 43,500 compounds and 15,000 natural product extracts * Results for 60,000 compounds evaluated in the yeast assay * In vivo animal model results for 30,000 compounds * 2-D and 3-D chemical structures for more than 200,000 compounds * Molecular target data, including characterizations for at least 1,200 targets, plus data from multiple cDNA microarray projects In addition to browsing DTP's databases and downloading data, researchers can request individual samples or sets of compounds on 96-well plates for research, or they can submit their own compounds for consideration for screening via DTP's online submission form. Once a compound is submitted for screening, researchers can follow its progress and retrieve data using a secure web interface. The NCI has collected information on almost half a million chemical structures in the past 50 years. DTP has made this information accessible and useful for investigators through its 3-D database, a collection of three-dimensional structures for more than 200,000 drugs. Investigators use the 3-D database to screen compounds for anticancer therapeutic activity. Also available on DTP's website are 127,000 connection tables for anticancer agents. A connection table is a convenient way of depicting molecular structures without relying on drawn chemical structures. As unique lists of atoms and their connections, the connection tables can be indexed and stored in computer databases where they can be used for patent searches, toxicology studies, and precursor searching, for example.
View all literature mentionsSoftware tool for multi level analysis of applications optimized for ImageXpress instruments. High-content image analysis software featuring time lapse analysis. Used for 2D and 3D imaging.
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