| First Author | Ellermeier J | Year | 2013 |
| Journal | Cancer Res | Volume | 73 |
| Issue | 6 | Pages | 1709-20 |
| PubMed ID | 23338611 | Mgi Jnum | J:196895 |
| Mgi Id | MGI:5490172 | Doi | 10.1158/0008-5472.CAN-11-3850 |
| Citation | Ellermeier J, et al. (2013) Therapeutic efficacy of bifunctional siRNA combining TGF-beta1 silencing with RIG-I activation in pancreatic cancer. Cancer Res 73(6):1709-20 |
| abstractText | Deregulated TGF-beta 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-beta 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-beta1 (ppp-TGF-beta) and studied its therapeutic efficacy in the orthotopic Panc02 mouse model of pancreatic cancer. Intravenous injection of ppp-TGF-beta reduced systemic and tumor-associated TGF-beta 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-beta significantly prolonged survival as compared with ppp-RNA or TGF-beta 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-beta gene silencing with RIG-I signaling confers potent antitumor efficacy against pancreatic cancer by breaking tumor-induced CD8(+) T cell suppression. |
