title: BCR-ABL-expressing cells transduced with the HSV-tk gene die by apoptosis upon treatment with ganciclovir.
abstract: The potential efficacy of prodrug activation of a transduced suicide gene in a cancer cell may be impaired or enhanced by oncoproteins produced by that cell. In the context of a gene therapy protocol for chronic myeloid leukemia (CML) we examined whether the Bcr-Abl fusion protein would have either of these effects. Thus, the mechanism of cell killing by transfer of herpes simplex virus thymidine kinase (HSV-tk) and subsequent ganciclovir (GCV) treatment was examined in pre-B (TonB210.1) cells and myeloid cells (32D) and in their BCR-ABL-expressing counterparts. HSV-tk-transduced cell lines, either in the presence or in the absence of BCR-ABL expression, became susceptible to GCV at concentrations which were nontoxic to the nontransduced cells. This susceptibility was represented by apoptotic cell death in all cases. Apoptosis was observed after 24 h of treatment with GCV in the tk-transduced parental cells and in the BCR-ABL-expressing TonB210.1 cells but only after a delay of more than 24 h in the 32Dp210 cells compared to 32D. Cell death in the BCR-ABL-expressing clones was preceded by S- and G2/M-phase cell cycle arrest. Activation of FAS/APO-1 and caspase-8 was observed in all the tk-transduced cell lines after GCV treatment. However, the caspase-8 inhibitor Z-IETD-FMK only partially abrogated tk/GCV-induced apoptosis. A possible role for inhibition of Bcl-2 or Bcl-x(L) expression in the apoptosis induced by GCV was observed in the tk-transduced TonB210.1 cells but not in the 32D or 32Dp210 cells. The data demonstrate that expression of the Bcr-Abl oncoprotein does not block the apoptosis induced by the HSV-tk/GCV system, suggesting that this suicide gene therapy strategy could be considered for the treatment of CML in blast crisis.
authors.affiliation: Department of Haematology, Imperial College of Science, Technology and Medicine, Hammersmith Hospital, Du Cane Road, London W12 ONN, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Rivas
authors.forename: A R
authors.initials: AR
authors.lastname: Miller
authors.forename: M
authors.initials: M
authors.lastname: Collado
authors.forename: E W
authors.initials: EW
authors.lastname: Lam
authors.forename: J F
authors.initials: JF
authors.lastname: Apperley
authors.forename: J V
authors.initials: JV
authors.lastname: Melo
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000494:pharmacology; D000998:Antiviral Agents / Q000494:pharmacology*; D017209:Apoptosis; D001752:Blast Crisis / Q000188:drug therapy; D015153:Blotting, Western; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000096:biosynthesis; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis*; D015774:Ganciclovir / Q000494:pharmacology*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D009369:Neoplasms / Q000628:therapy; D018139:Simplexvirus / Q000235:genetics*; D013937:Thymidine Kinase / Q000235:genetics*; D013997:Time Factors; D014161:Transduction, Genetic; D019014:fas Receptor / Q000096:biosynthesis
chemical_list: D017304:Annexin A5; D000998:Antiviral Agents; D004792:Enzyme Precursors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D019014:fas Receptor; D013937:Thymidine Kinase; D016044:Fusion Proteins, bcr-abl; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D015774:Ganciclovir