Abstract
<div>Abstract<p>PR-104 is a dinitrobenzamide mustard currently in clinical trial as a hypoxia-activated prodrug. Its major metabolite, PR-104A, is metabolized to the corresponding hydroxylamine (PR-104H) and amine (PR-104M), resulting in activation of the nitrogen mustard moiety. We characterize DNA damage responsible for cytotoxicity of PR-104A by comparing sensitivity of repair-defective hamster Chinese hamster ovary cell lines with their repair-competent counterparts. PR-104H showed a repair profile similar to the reference DNA cross-linking agents chlorambucil and mitomycin C, with marked hypersensitivity of XPF<sup>−/−</sup>, ERCC1<sup>−/−</sup>, and Rad51D<sup>−/−</sup> cells but not of XPD<sup>−/−</sup> or DNA-PK<sub>CS</sub><sup>−/−</sup> cells. This pattern confirmed the expected dependence on the ERCC1-XPF endonuclease, implicated in unhooking DNA interstrand cross-links at blocked replication forks, and homologous recombination repair (HRR) in restarting collapsed forks. However, even under anoxia, the hypersensitivity of XPF<sup>−/−</sup>, ERCC1<sup>−/−</sup>, and Rad51D<sup>−/−</sup> cells to PR-104A itself was lower than for chlorambucil. To test whether this reflects inefficient PR-104A reduction, a soluble form of human NADPH:cytochrome P450 oxidoreductase was stably expressed in Rad51D<sup>−/−</sup> cells and their HRR-restored counterpart. This expression increased hypoxic metabolism of PR-104A to PR-104H and PR-104M as well as hypoxia-selective cytotoxicity of PR-104A and its dependence on HRR. We conclude that PR-104A cytotoxicity is primarily due to DNA interstrand cross-linking by its reduced metabolites, although under conditions of inefficient PR-104A reduction (low reductase expression or aerobic cells), a second mechanism contributes to cell killing. This study shows that hypoxia, reductase activity, and DNA interstrand cross-link repair proficiency are key variables that interact to determine PR-104A sensitivity. [Mol Cancer Ther 2009;8(6):1714–23]</p></div>
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
