title: Therapeutic efficacy of bifunctional siRNA combining TGF-β1 silencing with RIG-I activation in pancreatic cancer.
abstract: Deregulated TGF-β signaling in pancreatic cancer promotes tumor growth, invasion, metastasis, and a potent immunosuppressive network. A strategy for disrupting this tumor-promoting pathway is silencing TGF-β by siRNA. By introducing a triphosphate group at the 5' end of siRNA (ppp-siRNA), gene silencing can be combined with immune activation via the cytosolic helicase retinoic acid-inducible gene I (RIG-I), a ubiquitously expressed receptor recognizing viral RNA. We validated RIG-I as a therapeutic target by showing that activation of RIG-I in pancreatic carcinoma cells induced IRF-3 phosphorylation, production of type I IFN, the chemokine CXCL10, as well as caspase-9-mediated tumor cell apoptosis. Next, we generated a bifunctional ppp-siRNA that combines RIG-I activation with gene silencing of TGF-β1 (ppp-TGF-β) and studied its therapeutic efficacy in the orthotopic Panc02 mouse model of pancreatic cancer. Intravenous injection of ppp-TGF-β reduced systemic and tumor-associated TGF-β levels. In addition, it induced high levels of type I IFN and CXCL10 in serum and tumor tissue, systemic immune cell activation, and profound tumor cell apoptosis in vivo. Treatment of mice with established tumors with ppp-TGF-β significantly prolonged survival as compared with ppp-RNA or TGF-β siRNA alone. Furthermore, we observed the recruitment of activated CD8(+) T cells to the tumor and a reduced frequency of CD11b(+) Gr-1(+) myeloid cells. Therapeutic efficacy was dependent on CD8(+) T cells, whereas natural killer cells were dispensable. In conclusion, combing TGF-β gene silencing with RIG-I signaling confers potent antitumor efficacy against pancreatic cancer by breaking tumor-induced CD8(+) T cell suppression.
authors: Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Germany.
authors: Jonathan
authors: J
authors: Ellermeier
authors: Jiwu
authors: J
authors: Wei
authors: Peter
authors: P
authors: Duewell
authors: Sabine
authors: S
authors: Hoves
authors: Mareike R
authors: MR
authors: Stieg
authors: Tina
authors: T
authors: Adunka
authors: Daniel
authors: D
authors: Noerenberg
authors: Hans-Joachim
authors: HJ
authors: Anders
authors: Doris
authors: D
authors: Mayr
authors: Hendrik
authors: H
authors: Poeck
authors: Gunther
authors: G
authors: Hartmann
authors: Stefan
authors: S
authors: Endres
authors: Max
authors: M
authors: Schnurr
mesh_terms: D000818:Animals; D017209:Apoptosis; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D054357:Chemokine CXCL10 / Q000097:blood; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D020868:Gene Silencing; D007370:Interferon Type I / Q000097:blood; D051379:Mice; D008810:Mice, Inbred C57BL; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics* / Q000627:therapeutic use; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000235:genetics*
chemical_list: D054357:Chemokine CXCL10; C485433:Cxcl10 protein, mouse; D007370:Interferon Type I; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; C503356:Ddx58 protein, mouse; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases