title: Improving cellular uptake and in vivo tumor suppression efficacy of liposomal oligonucleotides by urea as a chemical penetration enhancer.
abstract: BACKGROUND
  Liposomes are among the most widely used carriers for the delivery of antisense oligonucleotides (AsODNs) to intracellular targets. Although different strategies have been employed, the question of how to improve liposomal uptake and enhance the release of AsODN into cytoplasm still remains to be answered with respect to the use of a safe, easy and economic method. In the present study, the possibility of enhancing such processes at cellular and animal levels using urea as a penetration enhancer was investigated.
  
  
  METHODS
  To perform this investigation, a cationic liposome containing an AsODN against protein kinase (PKC)-α was prepared, and the effect of urea on its cellular internalization and the related sequence-specific inhibition of gene expression in human lung adenocarcinoma A549 cells were investigated by flow cytometry and the reverse transcriptase-polymerase chain reaction, respectively. In in vivo studies, a xenograft lung tumor was established in nude mice by A549 cells and the enhancement effect of urea toward the effects of liposomal AsODN on tumor growth was investigated.
  
  
  RESULTS
  Cellular studies revealed that urea treatment increases liposomal uptake and the release of AsODN into the cytoplasm by approximately 40%. Sequence-specific inhibition of target gene PKC-α expression was also increased by approximately two-fold by urea at 200-300 nM AsODN. In animal studies, urea significantly decreased the tumor volume (approximately 40%) and increased its doubling time from approximately 13 days to 17 days.
  
  
  CONCLUSIONS
  Urea, and possibly other membrane fluidizers, could be regarded as penetration enhancers for liposomal AsODN delivery and may improve the therapeutic effect of these gene-therapy vectors at both cellular and animal levels.
authors.affiliation: School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Saffari
authors.forename: Ali Mohammad
authors.initials: AM
authors.lastname: Tamaddon
authors.forename: Farshad Hoseini
authors.initials: FH
authors.lastname: Shirazi
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Oghabian
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Moghimi
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D018014:Gene Transfer Techniques; D006801:Humans; D016014:Linear Models; D008081:Liposomes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014508:Urea / Q000378:metabolism*
chemical_list: D008081:Liposomes; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D014508:Urea; C496630:Prkca protein, mouse; D051571:Protein Kinase C-alpha