title: Carcinoembryonic antigen directed herpes viral oncolysis improves selectivity and activity in colorectal cancer.
abstract: BACKGROUND
  G207 is an oncolytic herpes virus whose replicative cycle requires cellular ribonucleotide reductase (RR) for viral DNA synthesis. We attempt to enhance viral cytotoxicity in carcinoembryonic antigen (CEA)-producing colorectal cancer (CRC) cells through CEA-driven RR production.
  
  
  METHODS
  CEA enzyme-linked immunosorbent assay was performed on LS174T and HCT-8 human CRC cells. The CEA enhancer-promoter (CEA E-P) was functionally assessed by luciferase assay. CEA E-P was cloned upstream of UL39, the gene encoding the large subunit of RR. Cells were transfected with CEA E-P/UL39 and infected with G207 for cytotoxicity assays. LS174T, with or without CEA E-P/UL39, were implanted into athymic mouse flanks (n = 28) and treated with G207.
  
  
  RESULTS
  CEA levels were 7-fold higher in LS174T versus HCT-8 ( P <.00001). CEA E-P increased luciferase expression 7.5-fold in LS174T ( P <.01), with no increase in HCT-8. G207 cytotoxicity of'CEA E-P/UL39-transfected LS174T cells increased 69% by day 10 versus nontransfected cells ( P <.001), with no significant increase in HCT-8. Combining CEA E-P/UL39 with G207 in LS174T flank tumors resulted in a 65% decrease in tumor volume versus G207, phosphate-buffered saline, or'CEA E-P/UL39 alone ( P <.0001).
  
  
  CONCLUSIONS
  CEA-driven RR production by CEA-secreting CRC cells significantly improves oncolytic viral cytotoxicity and specificity in vitro, and reduces tumor burden in vivo.
authors.affiliation: Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors.forename: Maura
authors.initials: M
authors.lastname: Reinblatt
authors.forename: Richard H
authors.initials: RH
authors.lastname: Pin
authors.forename: Yuman
authors.initials: Y
authors.lastname: Fong
mesh_terms: D002272:Carcinoembryonic Antigen / Q000235:genetics*; D016923:Cell Death; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000628:therapy*; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D012264:Ribonucleotide Reductases / Q000502:physiology; D018139:Simplexvirus / Q000235:genetics*; D014779:Virus Replication / Q000502:physiology; D014780:Viruses / Q000235:genetics
chemical_list: D002272:Carcinoembryonic Antigen; D012264:Ribonucleotide Reductases