Combined radiation and cytochrome CYP4B1/4-ipomeanol gene therapy using the EGR1 promoter ANTICANCER RESEARCH Hsu, H., Rainov, N. G., QUINONES, A., Eling, D. J., Sakamoto, K. M., Spear, M. A. 2003; 23 (3B): 2723-2728

Abstract

Cytochrome p450 isozyme CYP4B1 converts the inert prodrug 4-ipomeanol (4-IM) into toxic alkylating metabolites. Induction of cytotoxicity by 4-IM combined with ionizing radiation (IR) in cells transfected with a fusion protein of rabbit cytochrome CYP4B1 under control of the radiation inducible EGR1 promoter was investigated. The capability of activated 4-IM to sensitize cells to IR was also assessed.Survival fractions of cells, determined by MTT assays, stably transfected with EGR1-CYP4B1 were compared with that of cells transfected with a control plasmid after IR followed by 4-IM. Radiosensitization was tested by comparing clonogenic survival curves of cells transfected with the CYP4B1 cassette under a CMV promoter instead of EGR-1, irradiated with or without 4-IM.MTT assays for cytotoxicity indicated a decrease in relative survival fractions (survival with 4-IM/survival without 4-IM) of the EGR1-CYP4B1 transfected cells with increasing radiation dosage, but not of control cells. Clonogenic assays revealed decreased survival fractions with increasing radiation doses (CYP4B1 transfected and control cells) and 4-IM concentrations (CYP4B1 transfected cells), but showed no significant differences in slope of survival curves with 4-IM.The results indicate IR potentiates the cytotoxic activity of the EGR1-CYP4B1/4-IM transgene system, but activated 4-IM does not sensitize cells to IR. Thus, the EGR1-CYP4B1/4-IM system is a viable radiation-gene therapy system that may allow for improved spatial and temporal control of cytotoxicity by therapeutic radiation fields.

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View details for PubMedID 12894565