title: Retroviral transfer of a bacterial alkyltransferase gene (ada) into human bone marrow cells protects against O6-benzylguanine plus 1, 3-bis(2-chloroethyl)-1-nitrosourea cytotoxicity.
abstract: The antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) is limited by the O6-alkylguanine-DNA alkyltransferase (ATase) in tumor cells and by delayed myelosuppression. Inactivation of neoplastic ATase by O6-benzylguanine (BG) improves the therapeutic index for BCNU. We have demonstrated previously that BG + BCNU-induced myelosuppression in mice is reduced by expression of the BG-resistant ATase ada in murine bone marrow. We have now generated an amphotropic retrovirus containing the ada gene and tested the effectiveness of ada expression in preventing BG + BCNU cytotoxicity in human hematopoietic progenitor cells. A retroviral producer clone with a biological titer of 6.5 x 10(4) colony-forming units/ml and 4.4 pmol ATase/mg protein was used for transduction of bone marrow. Cocultivation of these ada producer cells with progenitor cells from six normal individuals resulted in 1.9-3. 9-fold protection against BG + BCNU-induced cytotoxicity in committed progenitor cell assays. Furthermore, this cytoprotective effect was associated with a high transduction efficiency (40%) and a 2-fold increase of ATase activity in the surviving committed progenitor cell colonies. These data provide a basis for testing the clinical effectiveness of retroviral ada gene transfer into hematopoietic cells to increase the therapeutic index of BG + BCNU.
authors.affiliation: Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: U K
authors.initials: UK
authors.lastname: Marathi
authors.forename: L C
authors.initials: LC
authors.lastname: Harris
authors.forename: C C
authors.initials: CC
authors.lastname: Venable
authors.forename: T P
authors.initials: TP
authors.lastname: Brent
mesh_terms: D016475:3T3 Cells; D000293:Adolescent; D000328:Adult; D019883:Alkyl and Aryl Transferases / Q000096:biosynthesis / Q000235:genetics* / Q000494:pharmacology; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D002330:Carmustine / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005822:Genetic Vectors; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D051379:Mice; D020011:Protective Agents / Q000494:pharmacology; D012190:Retroviridae / Q000235:genetics; D013234:Stem Cells / Q000187:drug effects / Q000201:enzymology; D014161:Transduction, Genetic
chemical_list: D020011:Protective Agents; C064976:O(6)-benzylguanine; D006147:Guanine; D019883:Alkyl and Aryl Transferases; D002330:Carmustine