title: Efficient generation of double heterologous promoter controlled oncolytic adenovirus vectors by a single homologous recombination step in Escherichia coli.
abstract: BACKGROUND
  Oncolytic adenoviruses are promising agents for the multimodal treatment of cancer. However, tumor-selectivity is crucial for their applicability in patients. Recent studies by several groups demonstrated that oncolytic adenoviruses with tumor-/tissue-specific expression of the E1 and E4 genes, which are pivotal for adenoviral replication, have a specificity profile that is superior to viruses that solely target the expression of E1 or E4 genes. Presently the E1 and E4 regions are modified in a time consuming sequential fashion.
  
  
  RESULTS
  Based on the widely used adenoviral cloning system AdEasy we generated a novel transfer vector that allows efficient and rapid generation of conditionally replication-competent adenovirus type 5 based vectors with the viral E1 and E4 genes under the transcriptional control of heterologous promoters. For insertion of the promoters of interest our transfer vector has two unique multiple cloning sites. Additionally, our shuttle plasmid allows encoding of a transgene within the E1A transcription unit. The modifications, including E1 mutations, are introduced into the adenoviral genome by a single homologous recombination step in Escherichia coli. Subsequently infectious viruses are rescued from plasmids. As a proof-of-concept we generated two conditionally replication-competent adenoviruses Ad.Ki x COX and Ad.COX x Ki with the promoters of the Ki-67 protein and the cyclooxygenase-2 (COX-2) driving E1 and E4 and vice versa.
  
  
  CONCLUSIONS
  We demonstrated with our cloning system efficient generation of double heterologous promoter controlled oncolytic adenoviral vectors by a single homologous recombination step in bacteria. The generated viruses showed preferential replication in tumor cells and in a subcutaneous HT-29 colon cancer xenograft model the viruses demonstrated significant oncolytic activity comparable with dl327.
authors.affiliation: Ruhr-University Bochum, Institute of Microbiology and Hygiene, Department of Molecular and Medical Virology, Bldg, MA, Rm, 6/40, D-44801 Bochum, Germany. Dennis.Hoffmann@ruhr-uni-bochum.de
authors.forename: Dennis
authors.initials: D
authors.lastname: Hoffmann
authors.forename: Oliver
authors.initials: O
authors.lastname: Wildner
mesh_terms: D017498:Adenovirus E1 Proteins / Q000235:genetics / Q000378:metabolism; D017504:Adenovirus E4 Proteins / Q000235:genetics / Q000378:metabolism; D000260:Adenoviruses, Human / Q000235:genetics* / Q000502:physiology; D000818:Animals; D002648:Child; D051546:Cyclooxygenase 2 / Q000235:genetics; D003588:Cytopathogenic Effect, Viral; D004274:DNA, Recombinant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005818:Genetic Engineering / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics*; D019073:HT29 Cells; D006801:Humans; D019394:Ki-67 Antigen / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation / Q000235:genetics; D050504:Oncolytic Viruses / Q000235:genetics* / Q000502:physiology; D009928:Organ Specificity; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics*; D014779:Virus Replication; D023041:Xenograft Model Antitumor Assays
chemical_list: D017498:Adenovirus E1 Proteins; D017504:Adenovirus E4 Proteins; D004274:DNA, Recombinant; D019394:Ki-67 Antigen; D051546:Cyclooxygenase 2