title: Mechanisms of cell death induced by suicide genes encoding purine nucleoside phosphorylase and thymidine kinase in human hepatocellular carcinoma cells in vitro.
abstract: For gene therapy of hepatocellular carcinoma (HCC), the Escherichia coli purine nucleoside phosphorylase (PNP)/fludarabine suicide gene system may be more useful than the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system as a result of a stronger bystander effect. To analyze the molecular mechanisms involved in PNP/fludarabine-mediated cell death in human HCC cells in comparison with HSV-tk/GCV, we transduced human HCC cells of the cell lines, HepG2 and Hep3B, with PNP or HSV-tk using adenoviral vectors, followed by prodrug incubation. Both systems predominantly induced apoptosis in HepG2 and Hep3B cells. PNP/fludarabine induced strong p53 accumulation and a more rapid onset of apoptosis in p53-positive HepG2 cells as compared with p53-negative Hep3B cells, but efficiency of tumor cell killing was similar in both cell lines. In contrast, HSV-tk/GCV-induced apoptosis was reduced in p53-negative Hep3B cells as compared with p53-positive HepG2 cells. HSV-tk/GCV, but not PNP/fludarabine, caused up-regulation of Fas in p53-positive HepG2 cells and of Fas ligand (FasL) in both HCC cell lines. These results demonstrate cell line-specific differences in response to treatment with PNP/fludarabine and HSV-tk/GCV, respectively, and indicate that PNP/fludarabine may be superior to HSV-tk/GCV for the treatment of human HCC because of its independence from p53 and the Fas/FasL system.
authors.affiliation: Department of Medicine II, University Hospital Freiburg, Germany.
authors.forename: T U
authors.initials: TU
authors.lastname: Krohne
authors.forename: S
authors.initials: S
authors.lastname: Shankara
authors.forename: M
authors.initials: M
authors.lastname: Geissler
authors.forename: B L
authors.initials: BL
authors.lastname: Roberts
authors.forename: J R
authors.initials: JR
authors.lastname: Wands
authors.forename: H E
authors.initials: HE
authors.lastname: Blum
authors.forename: L
authors.initials: L
authors.lastname: Mohr
mesh_terms: D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy*; D016923:Cell Death / Q000235:genetics; D053222:Fas Ligand Protein; D015316:Genetic Therapy; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy*; D008562:Membrane Glycoproteins / Q000378:metabolism; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
chemical_list: C505661:FASLG protein, human; D053222:Fas Ligand Protein; D018840:HSP70 Heat-Shock Proteins; D008562:Membrane Glycoproteins; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D011683:Purine-Nucleoside Phosphorylase; D013937:Thymidine Kinase