Abstract 4510: Analysis of antitumor effect of human papillomavirus E6 siRNA-loaded polymeric micelles on human cervical cancer.

Abstract Small interfering RNA (siRNA) therapies administered by intravenous injection have great potential for cancer treatments. E6 and E7 oncogenes of human papillpmavirus (HPV) are known to cause human cervical cancer, because E6 degrades tumor suppressor proteins such as p53, and E7 inactivates the performance of pRB tumor suppressor protein. Thus E6 and E7 oncogenes of HPV are supposed to be good targets of gene therapy against cervical cancers. However, therapeutic siRNA requires a delivery system for transport from the bloodstream into the cytoplasm of cancer cells to perform the function of gene silencing because siRNA is a large water-soluble polyion that can't easily diffuse across cell membrane. Furthermore, enzymatic activity in blood stream causes degradation of siRNA. Macromolecular carriers are supposed to improve the performance of drugs by prolonged blood circulation and preferential tumor accumulation due to the enhanced permeability and retention (EPR) effect. We applied nanosized polymeric micelles that deliver siRNA to solid tumors and elicit a therapeutic effect. Stable multifunctional micelle structures of 45 nm in size formed by spontaneous self-assembly of poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLL) block copolymers and the cyclo-Arg-Gly-Asp (cRGD) peptide on the PEG terminus were used to incorporate with HPV E6/E7 siRNAs. To evaluate the in vivo antitumor effect of E6/E7 loaded siRNA micelles (E6siRNA/m), subcutaneous xenograft models were established by transplanting human cervical cells (Hela and CaSki) into nude mice. In vivo toxicity of E6siRNA/m was estimated by weight of mice. The accumulation of E6siRNA/m into tumor and circulation of micelles in blood flow were evaluated by intravital real-time confocal laser scanning microscopy (IVRTCLSM). E6siRNA/m injected intravenously into mice with cervical cancer xenografts demonstrated gene silencing in the tumor mass and showed significantly stronger inhibition of tumor growth compared to control siRNA-loaded micelles (control). Also there was no significant difference in the weight of mice between control and E6siRNA/m groups. IVRTCLSM revealed that E6siRNA/m had prolonged blood circulation and enhanced accumulation into tumors. This new technology of gene delivery using micellar nanoparticle could potentially expand the utility of siRNA-based systemic gene therapies for cervical cancer treatments. Citation Format: Haruka Nishida, Matsumoto Yoko, Christie R. James, Kawana Kei, Inoue Tomoko, Taguchi Ayumi, Nagasaka Kazunori, Oda Katsutoshi, Miyata Kanjiro, Matsumoto Yu, Nishiyama Nobuhiro, Kataoka Kazunori, Fujii Tomoyuki. Analysis of antitumor effect of human papillomavirus E6 siRNA-loaded polymeric micelles on human cervical cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4510. doi:10.1158/1538-7445.AM2013-4510