title: Tumor-selective gene expression in a hepatic metastasis model after locoregional delivery of a replication-competent retrovirus vector.
abstract: OBJECTIVE
  Replication-competent retrovirus (RCR) vectors have been shown to achieve highly efficient and tumor-restricted replicative spread and gene transfer in vivo after direct intratumoral injection in a variety of primary cancer models. In this setting, the intrinsic inability of retroviruses to infect postmitotic normal cells, combined with their unique ability to persist through stable integration, allow further transduction of ectopic tumor foci as the infected cancer cells migrate. However, i.v. delivery of RCR vectors has never been tested previously, particularly in an immunocompetent tumor model.
  
  
  METHODS
  We combined optical imaging, flow cytometry, and molecular analysis to monitor RCR vector spread after administration via locoregional infusion in a hepatic metastasis model of colorectal cancer.
  
  
  RESULTS
  Robust RCR replication was first confirmed in both human WiDr and murine CT26 colorectal cancer cells in vitro, with transduction levels reaching >90% in <12 days after virus inoculation at multiplicities of infection of 0.01 to 0.1. In vivo, infusion of RCR supernatant into the portal circulation resulted in progressive and significant transduction of multifocal intrahepatic CT26 tumors in syngeneic mice, averaging about 30% but with up to 60% transduction in some tumors within 4 weeks. However, immunohistochemistry and quantitative PCR analysis showed no evidence of RCR spread to adjacent normal liver or to any other normal tissues.
  
  
  CONCLUSIONS
  Our results thus show that locoregional infusion of RCR vectors can be used to deliver therapeutic genes selectively to tumor cells in the liver while sparing normal hepatocytes and without dissemination to extrahepatic normal tissues.
authors.affiliation: Department of Medicine, University of California at Los Angeles, California 90095, USA.
authors.forename: Kei
authors.initials: K
authors.lastname: Hiraoka
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kimura
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Logg
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kasahara
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D002404:Catheterization / Q000379:methods*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000628:therapy / Q000821:virology; D004195:Disease Models, Animal; D005260:Female; D020869:Gene Expression Profiling; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors / Q000008:administration & dosage* / Q000235:genetics; D006801:Humans; D036502:Infusions, Intralesional; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000556:secondary / Q000628:therapy; D051379:Mice; D008819:Mice, Nude; D011237:Predictive Value of Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014162:Transfection; D014183:Transplantation, Heterologous; D014779:Virus Replication; D023041:Xenograft Model Antitumor Assays