title: Generation of a tumor- and tissue-specific episomal non-viral vector system.
abstract: BACKGROUND
  A key issue for safe and reproducible gene therapy approaches is the autologous and tissue-specific expression of transgenes. Tissue-specific expression in vivo is either achieved by transfer vectors that deliver the gene of interest into a distinct cell type or by use of tissue-specific expression cassettes. Here we present the generation of non-viral, episomally replicating vectors that are able to replicate in a tissue specific manner thus allowing tissue specific transgene expression in combination with episomal replication. The episomal replication of the prototype vector pEPI-1 and its derivatives depends exclusively on a transcription unit starting from a constitutively active promoter extending into the scaffold/matrix attachment region (S/MAR).
  
  
  RESULTS
  Here, we exchanged the constitutive promoter in the pEPI derivative pEPito by the tumor specific alpha fetoprotein (AFP) or the muscle specific smooth muscle 22 (SM22) promoter leading to specific transgene expression in AFP positive human hepatocellular carcinoma (HUH7) and in a SM22 positive cell line, respectively. The incorporation of the hCMV enhancer element into the expression cassette further boosted the expression levels with both promoters. Tissue specific-replication could be exemplary proven for the smooth muscle protein 22 (SM22) promoter in vitro. With the AFP promoter-driven pEPito vector hepatocellular carcinoma-specific expression could be achieved in vivo after systemic vector application together with polyethylenimine as transfection enhancer.
  
  
  CONCLUSIONS
  In this study we present an episomal plasmid system designed for tissue specific transgene expression and replication. The human AFP-promoter in combination with the hCMV enhancer element was demonstrated to be a valuable tissue-specific promoter for targeting hepatocellular carcinomas with non-viral gene delivery system, and tissue specific replication could be shown in vitro with the muscle specific SM22 promoter. In combination with appropriate delivery systems, the tissue specific pEPito vector system will allow higher tissue-specificity with less undesired side effects and is suitable for long term transgene expression in vivo within gene therapeutical approaches.
authors.affiliation: Department of Pharmacy, Center for Drug Research, Pharmaceutical Biotechnology, Ludwig-Maximilians-University, Munich, Germany. rudolf.haase@cup.uni-muenchen.de
authors.forename: Rudolf
authors.initials: R
authors.lastname: Haase
authors.forename: Terese
authors.initials: T
authors.lastname: Magnusson
authors.forename: Baowei
authors.initials: B
authors.lastname: Su
authors.forename: Florian
authors.initials: F
authors.lastname: Kopp
authors.forename: Ernst
authors.initials: E
authors.lastname: Wagner
authors.forename: Hans
authors.initials: H
authors.lastname: Lipps
authors.forename: Armin
authors.initials: A
authors.lastname: Baiker
authors.forename: Manfred
authors.initials: M
authors.lastname: Ogris
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D015870:Gene Expression; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000096:biosynthesis* / Q000235:genetics; D057809:HEK293 Cells; D006367:HeLa Cells; D064593:Heterografts; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism; D045170:Matrix Attachment Regions / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics*; D011401:Promoter Regions, Genetic; D054457:Tissue Scaffolds; D014162:Transfection; D019076:Transgenes; D000509:alpha-Fetoproteins / Q000235:genetics / Q000378:metabolism
chemical_list: C097353:AFP protein, human; D008840:Microfilament Proteins; D009124:Muscle Proteins; D000509:alpha-Fetoproteins; C051615:transgelin