[Research Articles] Therapeutic Targeting of a Robust Non-Oncogene Addiction to PRKDC in ATM-Defective Tumors

Sci Transl Med 12 June 2013:
Vol. 5, Issue 189, p. 189ra78
Sci. Transl. Med. DOI: 10.1126/scitranslmed.3005814 Cancer Arina Riabinska1,*, Mathias Daheim1,*, Grit S. Herter-Sprie1,†, Johannes Winkler2,3, Christian Fritz1,3, Michael Hallek1, Roman K. Thomas3,4,5, Karl-Anton Kreuzer1, Lukas P. Frenzel1,3, Parisa Monfared1, Jorge Martins-Boucas1, Shuhua Chen1,*,‡ and Hans Christian Reinhardt1,3,5,*,‡

1Department of Internal Medicine, University Hospital of Cologne, 50931 Cologne, Germany.

2Institute for Genetics, University of Cologne, 50937 Cologne, Germany.

3Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, 50674 Cologne, Germany.

4Department of Translational Genomics, University of Cologne, 50931 Cologne, Germany.

5Collaborative Research Center 832, Molecular Basis and Modulation of Cellular Interaction in the Tumor Microenvironment, 50937 Cologne, Germany. ?‡Corresponding author. E-mail: christian.reinhardt{at}uk-koeln.de (H.C.R.); shuhua.chen{at}uni-koeln.de (S.C.) ?* These authors contributed equally to this work.

?† Present address: Dana-Farber Cancer Institute, Boston, MA 02215, USA.

When the integrity of the genome is threatened, cells activate a complex, kinase-based signaling network to arrest the cell cycle, initiate DNA repair, or, if the extent of damage is beyond repair capacity, induce apoptotic cell death. The ATM protein lies at the heart of this signaling network, which is collectively referred to as the DNA damage response (DDR). ATM is involved in numerous DDR-regulated cellular responses—cell cycle arrest, DNA repair, and apoptosis. Disabling mutations in the gene encoding ATM occur frequently in various human tumors, including lung cancer and hematological malignancies. We report that ATM deficiency prevents apoptosis in human and murine cancer cells exposed to genotoxic chemotherapy. Using genetic and pharmacological approaches, we demonstrate in vitro and in vivo that ATM-defective cells display strong non-oncogene addiction to DNA-PKcs (DNA-dependent protein kinase catalytic subunit). Further, this dependence of ATM-defective cells on DNA-PKcs offers a window of opportunity for therapeutic intervention: We show that pharmacological or genetic abrogation of DNA-PKcs in ATM-defective cells leads to the accumulation of DNA double-strand breaks and the subsequent CtBP-interacting protein (CtIP)–dependent generation of large single-stranded DNA (ssDNA) repair intermediates. These ssDNA structures trigger proapoptotic signaling through the RPA/ATRIP/ATR/Chk1/p53/Puma axis, ultimately leading to the apoptotic demise of ATM-defective cells exposed to DNA-PKcs inhibitors. Finally, we demonstrate that DNA-PKcs inhibitors are effective as single agents against ATM-defective lymphomas in vivo. Together, our data implicate DNA-PKcs as a drug target for the treatment of ATM-defective malignancies.

Copyright © 2013, American Association for the Advancement of ScienceCitation: A. Riabinska, M. Daheim, G. S. Herter-Sprie, J. Winkler, C. Fritz, M. Hallek, R. K. Thomas, K.-A. Kreuzer, L. P. Frenzel, P. Monfared, J. Martins-Boucas, S. Chen, H. C. Reinhardt, Therapeutic Targeting of a Robust Non-Oncogene Addiction to PRKDC in ATM-Defective Tumors. Sci. Transl. Med. 5, 189ra78 (2013).

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[Research Articles] In Vivo-Directed Evolution of a New Adeno-Associated Virus for Therapeutic Outer Retinal Gene Delivery from the Vitreous

Sci Transl Med 12 June 2013:
Vol. 5, Issue 189, p. 189ra76
Sci. Transl. Med. DOI: 10.1126/scitranslmed.3005708 BLINDNESS Deniz Dalkara1,*, Leah C. Byrne1,*, Ryan R. Klimczak2, Meike Visel2, Lu Yin3, William H. Merigan3, John G. Flannery1,2,† and David V. Schaffer1,2,4,†

1Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720–1462, USA.

2Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720–1462, USA.

3Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA.

4Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720–1462, USA. ?†Corresponding author. E-mail: schaffer{at}berkeley.edu (D.V.S.); flannery{at}berkeley.edu (J.G.F.) ?* These authors contributed equally to this work.

Inherited retinal degenerative diseases are a clinically promising focus of adeno-associated virus (AAV)–mediated gene therapy. These diseases arise from pathogenic mutations in mRNA transcripts expressed in the eye’s photoreceptor cells or retinal pigment epithelium (RPE), leading to cell death and structural deterioration. Because current gene delivery methods require an injurious subretinal injection to reach the photoreceptors or RPE and transduce just a fraction of the retina, they are suitable only for the treatment of rare degenerative diseases in which retinal structures remain intact. To address the need for broadly applicable gene delivery approaches, we implemented in vivo–directed evolution to engineer AAV variants that deliver the gene cargo to the outer retina after injection into the eye’s easily accessible vitreous humor. This approach has general implications for situations in which dense tissue penetration poses a barrier for gene delivery. A resulting AAV variant mediated widespread delivery to the outer retina and rescued the disease phenotypes of X-linked retinoschisis and Leber’s congenital amaurosis in corresponding mouse models. Furthermore, it enabled transduction of primate photoreceptors from the vitreous, expanding its therapeutic promise.

Copyright © 2013, American Association for the Advancement of ScienceCitation: D. Dalkara, L. C. Byrne, R. R. Klimczak, M. Visel, L. Yin, W. H. Merigan, J. G. Flannery, D. V. Schaffer, In Vivo–Directed Evolution of a New Adeno-Associated Virus for Therapeutic Outer Retinal Gene Delivery from the Vitreous. Sci. Transl. Med. 5, 189ra76 (2013).

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