593. Targeted Histidinylated Lipopolyplexes for siRNA Delivery in 4T1 Mammary Carcinoma Cells

Abstract

Breast cancer is the leading cause of death among women aged 35 to 50 years. siRNA-based therapies aiming at reducing the overexpression of oncogenes and genes involved in tumor progression are developed for the treatment of cancer. However, clinical applications are delayed due to the absence of very efficient and safe delivery systems. For this purpose, we develop siRNA lipopolyplexes (LPRi) which are ternary complexes between cationic liposomes comprising imidazole/imidazolium lipophosphoramidates, histidinylated-lPEI cationic polymer and siRNA (1). Compared to commercial reagents, LPRi containing anti-eGFP or anti-Luc siRNA give in vitro higher specific inhibition (80% at 50nM siRNA) of reporter gene expression in cultures of eGFP-HeLa, Luc-B16F10 and Luc-4T1 cancer cells. Transfection of the 4T1 mammary carcinoma cells line with anti-survivin siRNA induces 30% reduction in cell viability. In vivo imaging after endotracheal administration of LPRi comprising polymer or liposomes labeled with a near-infrared fluorophore indicates a sustained delivery in the lung of the formulation until 24 hours post injection.For in vivo application, PEGylated LPRi has been armed with uPA peptide or folate which binds to the urokinase receptor (uPAR) and the folate receptor (FR), respectively. These targeted LPRi exhibit a 200 nm size and a reduced positive zeta potential. When tested for their uptake efficiency in 4T1 cells, targeted LPRi show a higher endocytosis compared to untargeted LPRi. When transfected with 50nM anti-Luc siRNA formulated with LPRi containing 2% Folate or 5% uPA LPRi, a better specific inhibition (54% and 40%, respectively) of luciferase expression in Luc-4T1 cells is obtained compared to untargeted LPRi (32%). Therapeutic applications of these new targeted siRNA formulations are now tested by using the murine orthotopic 4T1 breast cancer model.