title: A hypoxia- and {alpha}-fetoprotein-dependent oncolytic adenovirus exhibits specific killing of hepatocellular carcinomas.
abstract: OBJECTIVE
  Oncolytic adenoviruses (Ad) constitute a new promising modality of cancer gene therapy that displays improved efficacy over nonreplicating Ads. We have previously shown that an E1B 19-kDa-deleted oncolytic Ad exhibits a strong cell-killing effect but lacks tumor selectivity. To achieve hepatoma-restricted cytotoxicity and enhance replication of Ad within the context of tumor microenvironment, we used a modified human α-fetoprotein (hAFP) promoter to control the replication of Ad with a hypoxia response element (HRE).
  
  
  METHODS
  We constructed Ad-HRE(6)/hAFPΔ19 and Ad-HRE(12)/hAFPΔ19 that incorporated either 6 or 12 copies of HRE upstream of promoter. The promoter activity and specificity to hepatoma were examined by luciferase assay and fluorescence-activated cell sorting analysis. In addition, the AFP expression- and hypoxia-dependent in vitro cytotoxicity of Ad-HRE(6)/hAFPΔ19 and Ad-HRE(12)/hAFPΔ19 was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cytopathic effect assay. In vivo tumoricidal activity on subcutaneous and liver orthotopic model was monitored by noninvasive molecular imaging.
  
  
  RESULTS
  Ad-HRE(12)/hAFPΔ19 exhibited enhanced tumor selectivity and cell-killing activity when compared with Ad-hAFPΔ19. The tumoricidal activity of Ad-HRE(12)/hAFPΔ19 resulted in significant inhibition of tumor growth in both subcutaneous and orthotopic models. Histologic examination of the primary tumor after treatment confirmed accumulation of viral particles near hypoxic areas. Furthermore, Ad-HRE(12)/hAFPΔ19 did not cause severe inflammatory immune response and toxicity after systemic injection.
  
  
  CONCLUSIONS
  The results presented here show the advantages of incorporating HREs into a hAFP promoter-driven oncolytic virus. This system is unique in that it acts in both a tissue-specific and tumor environment-selective manner. The greatly enhanced selectivity and tumoricidal activity of Ad-HRE(12)/hAFPΔ19 make it a promising therapeutic agent in the treatment of liver cancers.
authors.affiliation: Brain Korea 21 Project for Medical Sciences, Institute for Cancer Research, Yonsei Cancer Center, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Oh-Joon
authors.initials: OJ
authors.lastname: Kwon
authors.forename: Pyung-Hwan
authors.initials: PH
authors.lastname: Kim
authors.forename: Steven
authors.initials: S
authors.lastname: Huyn
authors.forename: Lily
authors.initials: L
authors.lastname: Wu
authors.forename: Minjung
authors.initials: M
authors.lastname: Kim
authors.forename: Chae-Ok
authors.initials: CO
authors.lastname: Yun
mesh_terms: D000256:Adenoviridae / Q000235:genetics* / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D050130:Oncolytic Virotherapy / Q000379:methods*; D011401:Promoter Regions, Genetic; D013379:Substrate Specificity / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D000509:alpha-Fetoproteins / Q000235:genetics*
chemical_list: D000509:alpha-Fetoproteins