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A novel technique to monitor carboxypeptidase G2 expression in suicide gene therapy using 19F magnetic resonance spectroscopy.
- Source :
- NMR in Biomedicine; Jun2009, Vol. 22 Issue 5, p561-566, 6p
- Publication Year :
- 2009
-
Abstract
- Development and evaluation of new anticancer drugs are expedited when minimally invasive biomarkers of pharmacokinetic and pharmacodynamic behaviour are available. Gene-directed enzyme prodrug therapy (GDEPT) is a suicide gene therapy in which the anticancer drug is activated in the tumor by an exogenous enzyme previously targeted by a vector carrying the gene. GDEPT has been evaluated in various clinical trials using several enzyme/prodrug combinations. The key processes to be monitored in GDEPT are gene delivery and expression, as well as prodrug delivery and activation. {4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoyl}-L-glutamic acid, a prodrug for the GDEPT enzyme carboxypeptidase-G2 (CPG2; K<subscript>m</subscript> = 1.71 µM; k<subscript>cat</subscript> = 732 s<superscript>−1</superscript>), was measured with <superscript>19</superscript>F magnetic resonance spectroscopy (MRS). The 1 ppm chemical shift separation found between the signals of prodrug and activated drug (4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoic acid) is sufficient for the detection of prodrug activation in vivo. However, these compounds hydrolyze rapidly, and protein binding broadens the MR signals. A new CPG2 substrate was designed with hydroxyethyl instead of chloroethyl groups ( K<subscript>m</subscript> = 3.5 µM, k<subscript>cat</subscript> = 747 s<superscript>−1</superscript>). This substrate is nontoxic and stable in solution, has a narrow MRS resonance in the presence of bovine and foetal bovine albumin, and exhibits a 1.1 ppm change in chemical shift upon cleavage by CPG2. In cells transfected to express CPG2 in the cytoplasm (MDA MB 361 breast carcinoma cells and WiDr colon cancer cells), well-resolved <superscript>19</superscript>F MRS signals were observed from clinically relevant concentrations of the new substrate and its nontoxic product. The MRS conversion half-life (470 min) agreed with that measured by HPLC (500 min). This substrate is, therefore, suitable for evaluating gene delivery and expression prior to administration of the therapeutic agent. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 09523480
- Volume :
- 22
- Issue :
- 5
- Database :
- Complementary Index
- Journal :
- NMR in Biomedicine
- Publication Type :
- Academic Journal
- Accession number :
- 64208919
- Full Text :
- https://doi.org/10.1002/nbm.1375