title: Increased tumor distribution and expression of histidine-rich plasmid polyplexes.
abstract: BACKGROUND
  Selecting nonviral carriers for in vivo gene delivery is often dependent on determining the optimal carriers from transfection assays in vitro. The rationale behind this in vitro strategy is to cast a net sufficiently wide to identify the few effective carriers of plasmids for in vivo studies. Nevertheless, many effective in vivo carriers may be overlooked by this strategy because of the marked differences between in vitro and in vivo assays.
  
  
  METHODS
  After solid-phase synthesis of linear and branched histidine/lysine (HK) peptides, the two peptide carriers were compared for their ability to transfect MDA-MB-435 tumor cells in vitro and then in vivo.
  
  
  RESULTS
  By contrast to their transfection activity in vitro, the linear H2K carrier of plasmids was far more effective in vivo compared to the branch H2K4b. Surprisingly, negatively-charged polyplexes formed by the linear H2K peptide gave higher transfection in vivo than did those with a positive surface charge. To examine the distribution of plasmid expression within the tumor from H2K polyplexes, we found widespread expression by immunohistochemical staining. With a fluorescent tdTomato expressing-plasmid, we confirmed a pervasive distribution and gene expression within the tumor mediated by the H2K polyplex.
  
  
  CONCLUSIONS
  Although mechanisms underlying the efficiency of gene expression are probably multifactorial, unpacking of the H2K polyplex within the tumor appears to have a significant role. Further development of these H2K polyplexes represents an attractive approach for plasmid-based therapies of cancer.
authors.affiliation: Department of Pathology, University Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Qixin
authors.initials: Q
authors.lastname: Leng
authors.forename: Szu-Ting
authors.initials: ST
authors.lastname: Chou
authors.forename: Puthupparampil V
authors.initials: PV
authors.lastname: Scaria
authors.forename: Martin C
authors.initials: MC
authors.lastname: Woodle
authors.forename: A James
authors.initials: AJ
authors.lastname: Mixson
mesh_terms: D000818:Animals; D001704:Biopolymers / Q000737:chemistry*; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D015316:Genetic Therapy; D006639:Histidine / Q000737:chemistry*; D006801:Humans; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008819:Mice, Nude; D010316:Particle Size; D010957:Plasmids / Q000235:genetics*; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D001704:Biopolymers; D006639:Histidine; D008239:Lysine
keywords: cancer; gene therapy; nonviral; plasmid