Legumain Protease Substrate Modified Tat-Liposome Cargo: An Efficient Tool For Targeting Malignant Diseases.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Tumor targeting specificity and efficacy of the internalization of macro-biomolecular drugs have emerged as two major obstacles hampering the application of liposome-based delivery system against tumor. Trans-activating transcriptional activator (TAT) is a member of the cell-penetrating peptides which enhance the penetration of various macro-biomolecular cargos. In this study, we developed a modified TAT-Liposome cargo in which the activation of TAT peptide was blocked by Legumain protease substrate Ala-Ala-Asn-(AAN). Firstly, we confirmed the extremely high level of Legumain expression in a variety of solid tumors, as well as its specific effect on recognition and digestion of AAN. Then we conjugated AAN with the TAT peptide and constructed the modified liposome (AAN-TAT-Lipo) cargo. Flow-cytometry assay showed the internalization of AAN-TAT-Lipo was significantly higher than that of AAN-Lipo in 4T1 cells which expressed active Legumain. In vivo, the concentration of Dox encapsulated in AAN-TAT-Lipo was significantly higher in the tumor sites and lower in normal tissues compared with Free-Dox, AAN-Lipo-Dox and TAT-Lipo-Dox groups after administration in mouse model of orthotopic breast cancer. Luciferase assay showed that the AAN-TAT-Lipo-Dox dramatically inhibited tumor growth compared with other groups. TUNEL staining demonstrated that the apoptotic cells in tumor sites were significantly increased in the group of AAN-TAT-Lipo-Dox, compared with other groups. Whereas, the apoptotic cells in the heart, liver, spleen and kidney were decreased in the group of AAN-TAT-Lipo-Dox. Taken together, the modified TAT-lipo cargo via blocking TAT peptide activation with a Legumain specific substrate, AAN, is proven effective for improving the efficacy of internalization, and reducing the systemic toxicity of the tumor targeting delivery system as well. Citation Format: Ze Liu, Min Xiong, Debbie Liao, Dan Lv, Ralph A. Reisfeld, Wolfgang Wrasidlo, Si Chen, Dwayne G. Stupack, Peiqing Sun, Xiaoyue Tan, Rong Xiang. Legumain protease substrate modified TAT-liposome cargo: an efficient tool for targeting malignant diseases. [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 5614. doi:10.1158/1538-7445.AM2013-5614