FINAL PROGRAM - American Society of Gene & Cell Therapy

70American Society of Gene & Cell TherapyProgram ScheduleAl Charest, PhDNanoparticle-Mediated Delivery of siRNA in a Pre-Clinical Mouse Model of Glioblastoma MultiformeSmall interfering RNAs mediate cleavage of specific, complementary mRNA sequences and thus regulate gene expression. Not surprisingly, their use for treatment ofdiseases that are rooted in aberrant gene expression, such as cancer, has become a paradigm that has gained wide interest. We utilized dendrimer-conjugated magnetofluorescentnanoparticles to deliver anti-EGFR siRNA in vivo in an EGFR-driven transgenic model of glioblastoma. These nanoparticles were well tolerated in the CNS anddemonstrated specific and significant suppression of EGFR expression by convection-enhanced delivery to the mouse brain. Our data demonstrate the feasibility of siRNAdelivery in animals using a nanoplatform to efficiently knockdown target proteins.Scientific Symposium 4058:30 am - 10:30 amRoom: Marriott Ballroom Salons 2 & 3Special Considerations with Using Viral Vectors for Gene Modification of Stem CellsChairPhilip D. Gregory, PhDSpeakersMatthew Hirsch, PhDThe AAV Induced DNA Damage Response in Human Pluripotent CellsThe ability to genetically engineer stem cells ex vivo, then re-introduce them into a host for therapeutic purposes is an attractive approach for a variety of human geneticdiseases. Critical in this process is the ability to efficiently deliver transgenic DNA into the nucleus of stem cells in a manner that is well tolerated by the cell and withoutextensive host chromosome integration. A concern at the cellular level is the characterization of the cell type modified, and in particular, understanding the relationshipbetween “stemness” and oncogenesis. For example, the DNA damage response of pluripotent human embryonic stem cells (hESCs), in general, differs from that ofdifferentiated cells in that checkpoint functions are impaired and that these cells appear primed for rapid apoptosis. In this work, incidentally, we demonstrate that theadeno-associated virus (AAV) origin of replication, found ubiquitous in nature and currently used in human clinical trials for DNA delivery, induces a rapid, specific, andcomplete apoptotic response following transduction of non-differentiated hESCs. Cell cycle analysis by flow cytometry suggested that AAV-infected hESCs fail to induce aG1 checkpoint response and display an accumulation of cells in early S phase followed by apoptosis, suggesting that the AAV ITRs mimic stalled replication forks and/orperhaps uncapped telomeres. In contrast to reports of AAV-induced apoptosis in p53-deficient cancers, hESCs depleted of p53 survived significantly longer following AAVinfection than the parental control. Collectively, these data demonstrate that the AAV origin of replication (present on all AAV vectors) induces a lethal signaling cascadeduring S-phase in hESCs and a subsequent p53-dependent apoptotic response. This unexpected phenomenon is the first report of AAV vector toxicity in a wild type humancell and is reminiscent of previous reports of toxicity in p53-deficient cancers cells following AAV transduction. Understanding such unique DNA damage responses in stemcells and cancers following DNA delivery is necessary for optimization of conditions for efficient genetic engineering and safety in cell replacement therapies.Saturday, May 22 ndPhilip D. Gregory, hDStem Cell Modification with Zinc Finger NucleasesFrederic Paques, PhDMeganucleases and Viral Vectors: Alternative or Complementary ApproachesTargeted approaches have emerged today as an alternative to current random insertion strategies for gene therapy. Meganucleases, the most specific natural endonucleasesrepresent ideal tools for targeted genome editing, or “genome surgery”. Natural as well as engineered can be used to induce up to 20% of gene insertion into chosenhuman genes. The introduction of meganucleases into different cell types can be achieved by various means, including viral and non viral vectorization.Andrew M. Scharenberg, MDGene Editing Using Lentiviral Expression of Homing EndonucleasesGene editing and targeted integration approaches to gene therapy offer the potential to avoid idiosyncratic side effects associated with the random integration ofpromoter/gene cassettes in traditional gene therapy. The Northwest Genome Engineering Consortium is exploring the development of lentiviral vector-mediated expressionof homing endonucleases for gene editing and targeted integration in hematopoietic cells. Preliminary data on the efficacy of this approach in cultured and primaryhematopoietic cell models will be presented, and challenges and future directions in the field will be discussed.Break10:30 am – 11:00 amEXHIBITOR PROSPECTUSfinal program