Purpose: The DNA-repair protein, O6-alkylguanine-DNA alkyl transferase, may account for resistance of CNS tumors to DNA-alkylating drugs, such as bis-(2-chloroethyl)-1-nitrosourea (BCNU). The therapeutic effects of BCNU can be potentiated by inhibiting the repair protein with an alkylated guanine analog, O6-benzyl guanine (O6BG). To investigate potential toxicity of this inhibition, we examined the effects of O6BG in mice treated with intracranial (i.c.) BCNU given via a biodegradable polymer. Methods: Mice were treated with escalating doses of BCNU chronically delivered i.c., and with chronically delivered O6BG. The O6BG was delivered via a 7-day intraperitoneal (i.p.) or i.c. osmotic minipump. Toxicity of the combination therapies was measured from survival data. Bone marrow response was estimated from white blood cell counts. Results: Combining systemic (i.p.) O6BG with locally (i.c.) delivered BCNU resulted in a decrease in the maximum tolerated dose (MTD) of local BCNU. With local delivery of O6BG, the MTD of BCNU in combination with O6BG was increased. Conclusions: Based on the results of this study, a dose escalation study will be necessary when combining systemic O6BG with the higher doses of i.c. BCNU.
- Bis-chloroethyl nitrosourea (BCNU)
- O6-alkylguanine-DNA alkyl transferase (AGAT, MGMT)
- O6-benzyl guanine (O6BG)
ASJC Scopus subject areas
- Cancer Research
- Pharmacology (medical)