Abstract 3580: The role of CDNB in understanding the mechanism of action of JS-K, a promising anti-leukemia compound
Authors: Monika Z. Kaczmarek, Stephen A. Lavanier, Jami Troxler, Joseph Saavedra, Joan Cmarik, Larry Keefer, Sandra Ruscetti
Journal: Cancer Research (2010)

Abstract Previous studies have shown that JS-K (O2-(2,4-dinitrophenyl)1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate), which belongs to the diazeniumdiolate group of compounds, is a promising anti-cancer agent which is active against human leukemia cells but not normal hematopoietic cells. The uniqueness of JS-K is due to its ability to exploit the defense system of cancer cells against xenobiotics that leads to chemotherapy failure. JS-K consists of two components - a diazeniamdiolate group necessary for the release of nitric oxide (NO) and an arylating ring - and it is unknown which is responsible for the biological effects of the compound. Because treatment with pure NO is impractical, studying the activity of the arylating ring of JS-K in comparison to the entire molecule should help us understand the biological mechanisms of this compound. CDNB (1-chloro-2,4-dinitrobenzene), which contains an arylating ring analogous to that of JS-K without the diazeniumdiolate group necessary to release NO, was used to investigate the role of arylation due to the similarity in electrophilicity between CDNB and JS-K. In this study, we used a murine erythroleukemia (MEL) cell line from mice infected with the Friend spleen focus-forming virus. These cells grow as tumors when injected subcutaneously into mice and cause meningeal leukemia when injected intraveneously, providing a unique and convenient small animal model to study the effects of anti-leukemic agents. To determine the in vitro effects of JS-K and CDNB on MEL cells, experiments were performed using several methods, including proliferation and apoptotic assays, DNA-laddering, Western blotting and cell cycle analysis. Our studies indicate that both JS-K and CDNB inhibit proliferation of MEL cells with low IC50 values and induce necrosis and apoptosis by a caspase-dependent mechanism (e.g. PARP and caspase-3 activation). Further studies indicate that both compounds cause DNA damage and disturb the cell cycle. Cell cycle arrest after treatment appears to be due to a block in the activation of the serine kinase Akt, which results in the activation of the transcription factor FoxO3a, which in turn upregulates the cyclin-dependent kinase inhibitor p27, blocking the cell cycle. Although both tested compounds activate apoptosis, cause DNA damage and alter the cell cycle, JS-K is slightly more effective than CDNB. We conclude from these data that the arylating capability of JS-K, in addition to its ability to release NO, is a major contributor to the anticancer effects of this compound in MEL cells. Studies are in progress to determine if JS-K can block the growth of MEL cells in vivo. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3580.