The ataxia-telangiectasia mutated (ATM) protein plays a central role in DNA damage response and cell cycle checkpoints, and may be a promising target for cancer therapy if normal tissue toxicity could be avoided. Our strategy to target ATM for breast cancer therapy involves the use of liposomal-encapsulated, gene-specific ATM small interfering RNA (siRNA) delivered with a well-characterized porous silicon-based multistage vector (MSV) delivery system (MSV/ATM). Here we have shown that biweekly treatment of MSV/ATM suppressed ATM expression in tumor tissues, and consequently inhibited growth of MDA-MB-231 orthotopic tumor in nude mice. At the therapeutic dosage, neither free liposomal ATM siRNA nor MSV/ATM triggered acute immune response in BALB/c mice, including changes in serum cytokines, chemokines or colony-stimulating factors. Weekly treatments of mice with free liposomal ATM siRNA or MSV/ATM for 4 weeks did not cause significant changes in body weight, hematology, blood biochemistry, or major organ histology. These results indicate that MSV/ATM is biocompatible and efficacious in inhibiting tumor growth, and that further preclinical evaluation is warranted for the development of MSV/ATM as a potential therapeutic agent.

Citation Format: Rong Xu, Yi Huang, Jun Hua Mai, Guo Dong Zhang, Xiao Jing Guo, Xiao Jun Xia, Eugene J Koay, Xue Wu Liu, Mauro Ferrari, Hai Fa Shen. Multistage vectored siRNA targeting ataxia-telangiectasia mutated for breast cancer therapy. [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 3206. doi:10.1158/1538-7445.AM2013-3206