RT Journal Article SR Electronic T1 Tumor Cell Responses to a Novel Glutathione S-Transferase–Activated Nitric Oxide-Releasing Prodrug JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1070 OP 1079 DO 10.1124/mol.65.5.1070 VO 65 IS 5 A1 Victoria J. Findlay A1 Danyelle M. Townsend A1 Joseph E. Saavedra A1 Gregory S. Buzard A1 Michael L. Citro A1 Larry K. Keefer A1 Xinhua Ji A1 Kenneth D. Tew YR 2004 UL http://molpharm.aspetjournals.org/content/65/5/1070.abstract AB We have used structure-based design techniques to introduce the drug O2-[2,4-dinitro-5-(N-methyl-N-4-carboxyphenylamino) phenyl] 1-N,N-dimethylamino)diazen-1-ium-1,2-diolate (PABA/NO), which is efficiently metabolized to potentially cytolytic nitric oxide by the π isoform of glutathione S-transferase, an enzyme expressed at high levels in many tumors. We have used mouse embryo fibroblasts (MEFs) null for GSTπ (GSTπ-/-) to show that the absence of GSTπ results in a decreased sensitivity to PABA/NO. Cytotoxicity of PABA/NO was also examined in a mouse skin fibroblast (NIH3T3) cell line that was stably transfected with GSTπ and/or various combinations of γ-glutamyl cysteine synthetase and the ATP-binding cassette transporter MRP1. Overexpression of MRP1 conferred the most significant degree of resistance, and in vitro transport studies confirmed that a GSTπ-activated metabolite of PABA/NO was effluxed by MRP1 in a GSH-dependent manner. Additional studies showed that in the absence of MRP1, PABA/NO activated the extracellular-regulated and stress-activated protein kinases ERK, c-Jun NH2-terminal kinase (JNK), and p38. Selective inhibition studies showed that the activation of JNK and p38 were critical to the cytotoxic effects of PABA/NO. Finally, PABA/NO produced antitumor effects in a human ovarian cancer model grown in SCID mice.