Protection of committed murine haemopoietic progenitors against BCNU toxicity does not predict protection of primitive, multipotent spleen colony-forming cells - implications for chemoprotective gene therapy.
The effect of expression of an O6-benzylguanine (O6-beG)-resistant mutant (hATPA/GA) of human O6-alkylguanine-DNA alkyltransferase (ATase) on the in vivo toxicity and clastogenicity of the anti-tumour agent N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) to murine bone marrow has been investigated. When compared with control animals, the bipotent granulocyte-macrophage colony-forming (GM-CFC) progenitor population of the hATPA/GA transduced mice were somewhat more resistant to BCNU (1.4-fold, P = 0.047) and this effect was more significant in the presence of the ATase inactivator O6-beG (3. 5-fold, P = 0.001). The polychromatic erythrocytes were also significantly protected against BCNU-induced clastogenicity both in the presence (P < 0.001) and absence of O6-beG (P < 0.05). The primitive, multipotent spleen colony-forming cells (CFU-S) in these animals also showed moderate (1.6-fold, P = 0.034) protection in the absence of O6-beG but in the presence of the inactivator they remained as sensitive to BCNU toxicity as those in the control animals (P = 0.133). This result contrasts with previous findings demonstrating significant hATPA/GA-mediated, O6-beG-resistant protection against the toxicity and clastogenicity of a number of O6-alkylating agents, including temozolomide, fotemustine and chlorozotocin. The possibility that our strategy for protective gene therapy may be highly agent and cell-type specific is unexpected and has possible implications for clinical trials of this approach using BCNU or related agents.
Chinnasamy
N
N
CRC Sections of Genome Damage and Repair, Paterson Institute for Cancer Research, Manchester, UK.
Rafferty
J
J
Lashford
L
L
Chinnasamy
D
D
Margison
G
G
Thatcher
N
N
Dexter
T
T
Fairbairn
L
L
D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity; D002330:Carmustine / Q000633:toxicity*; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D019008:Drug Resistance, Neoplasm; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D015316:Genetic Therapy; D006098:Granulocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006147:Guanine / Q000031:analogs & derivatives / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D008297:Male; D051379:Mice; D015162:Micronucleus Tests; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D009713:Nucleotidyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013154:Spleen / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D014161:Transduction, Genetic
D000970:Antineoplastic Agents; D009153:Mutagens; C064976:O(6)-benzylguanine; D006147:Guanine; D009713:Nucleotidyltransferases; C020658:glutamine-synthetase adenylyltransferase; D002330:Carmustine