812 Design and Hydrodynamic Gene Transfer of ‘Sticky’ IFNγ for Liver Directed Gene Therapy of Hepatic Metastasis of Cancer Cells Molecular Therapy Volume 19, Supplement 1, May 2011 Copyright © Th[.]
CANCER-TARGETED GENE & CELL THERAPY III 810 Down-Regulation of Breast Cancer Resistance Protein (BCRP) by siRNA Delivery Using Lipid-Substituted Aliphatic Polymers Hamidreza Montazeri Aliabadi,1 Breanne Landry,1 Parvin Mahdipoor,1 Hasan Uludag.1 Department of Chemical & Material Engineering, University of Alberta, Edmonton, AB, Canada Polycationic polymers have been promising carriers in siRNA delivering strategies However, their potential has been limited by unacceptable toxicities and/or inadequate efficacy Hydrophobic modification with lipophilic moieties is an effective approach to enhance the siRNA delivery efficiencies, and this study methodically evaluated the effect of a range of lipophilic substitutions on low molecular PEI for siRNA delivery against a major efflux protein involved in multidrug resistance, Breast Cancer Resistance Protein (BCRP) Although BCRP was discovered in a breast cancer cell line, this membrane protein is expressed in different leukemia and solid tumor cells The BCRP has been additionally proposed to play a key role in chemoresistance in cancer stem cells Therefore, specific down-regulation of BCRP is a promising approach in sensitizing cancer cells to chemotherapeutic agents In this study, we synthesized a series of hydrophobically modified kDa PEIs by using different lipophilic moieties and evaluated their characteristics and potential as a siRNA delivery system for protein down-regulation Lipid substitution increased the toxicity of PEI2 for some of the higher lipid substitutions; however, this toxic effect was significantly less than the toxicity displayed by the 25 kDa branched PEI routinely used for nucleic acid delivery A significant increase in siRNA cellular uptake in wild-type and transfected BCRP-positive MDCK cells was observed with polymer:siRNA ratios of 1:2 and 1:8 when lipidsubstituted polymers were used The extent of lipid substitution was directly proportional to the extent of siRNA delivery into the cells A significant down-regulation in the target protein expression was also detected after 48 hours using 9-36 nM siRNA (complexed with lipid-substituted polymers), with a linear dose-effect relationship in the evaluated concentration range The highest down-regulation effect was achieved with Linoleic Acid-substituted polymers, and a strong correlation was observed between the siRNA uptake and downregulation level BCRP down-regulation after treatment with 36 nM siRNA was shown to sensitize the drug-resistant cells to cytotoxic effect of mitoxantrone by a 14-fold drop in the IC50 of the drug in the siRNA treated resistant cells 811 Experimental Gene Therapy of Nasopharyngeal Carcinoma Targeted to Telomerase Wen Zhong.1 Dept of ENT, Dept of ENT, ZhuJiang Hospital, Guangzhou City, China Telomerase is closely related to tumorigenesis As an ideal target, regulating telomerase activity has become a new direction for cancer gene therapy TK suicide gene vectors with hTERT single promoter and hTERT/CMV double promoter as well as expression vector of telomerase inhibitor PinX1 are able to target to telomerase and kill nasopharyngeal carcinoma (NPC) in vitro and in vivo In this study, we constructed three expression vectors: hTERT-TK, CMV/hTERTp-TK and pEGFP-C3-PinX1, and studied their tumor inhibitory effects on NPC 5-8F cells and in NPC xenograft in nude mice Expression of TK was confirmed by immunostaining, fluorescent quantitative PCR, telomerase activity assay and flow cytometry The results indicates that TK expression in cells transfected with CMV/hTERTp-TK was 2∼5-fold of that in cells transfected with hTERTp-TK Consequently, transfection of CMV/hTERTp-TK significantly inhibited NPC viability and migration as examined by MTT assay and Boyden chamber invasion experiment, respectively, and attenuated growth of NPC exnograft in nude mice compared to transfection of hTERTpTK (p