Expression of the bifunctional suicide gene CDUPRT increases radiosensitization and bystander effect of 5-FC in prostate cancer cells
Received 8 January 2009; received in revised form 9 March 2009; accepted 6 April 2009. published online 12 May 2009.
Abstract
Purpose
To test the hypothesis that, with 5-fluorocytosine (5-FC) treatment, the co-expression of cytosine deaminase (CD) and uracil phosphoribosyltransferase (UPRT) can lead to greater radiosensitization and bystander effect than CD-expression alone.
Methods and materials
R3327-AT cell lines stably expressing CD or CDUPRT were generated. The 5-FC and 5-FU cytotoxicity, and the radiosensitivity with/without 5-FC treatment, of these cells were evaluated under both aerobic and hypoxic conditions. The bystander effect was assessed by apoptosis staining and clonogenic survival. The pharmacokinetics of 5-FU and 5-FC metabolism was monitored in mice bearing CD- or CDUPRT-expressing tumors using 19F MR spectroscopy (MRS).
Results
CDUPRT-expressing cells were more sensitive to 5-FC and 5-FU than CD-expressing cells. CDUPRT-expression further enhanced the radiosensitizing effect of 5-FC, relative to that achieved by CD-expression alone. A 25-fold lower dose of 5-FC resulted in the same magnitude of radiosensitization in CDUPRT-expressing cells, relative to that in CD-expressing cells. The 5-FC cytotoxicity in co-cultures of parental cells mixed with 10–20% CDUPRT cells was similar to that in 100% CDUPRT cells. 19F MRS measurements showed that expression of CDUPRT leads to enhanced accumulation of fluorine nucleotide (FNuc), relative to that associated with CD-expression alone.
Conclusion
Our study suggests that CDUPRT/5-FC strategy may be more effective than CD/5-FC, especially when used in combination with radiation.
aDepartment of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
bDepartment of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
cDepartment of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, PR China
dDepartment of Nuclear Medicine, Shandong Cancer Hospital and Institute, Jinan, PR China
Corresponding author. Address: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, P.O. Box #72, New York, NY 10065, United States.
ABSTRACT