The eluted biotin from samples was detected by anti-biotin immunoblotting representing total nuclear S-NO content.Fig. any indicated JS-K concentration. The -catenin/TCF-4 transcriptional inhibitory activity was reduced by 32 8, 63 5, and 93 2% at 2, 10, and 25 M JS-K, respectively, based on luciferase reporter assays. JS-K reduced nuclear -catenin and cyclin D1 protein levels, but cytosolic -catenin expression did not change. Based on a time-course assay ofS-nitrosylation of proteins by a biotin switch assay,S-nitrsolyation of nuclear -catenin was determined to precede its degradation. A comparison of theS-nitrosylated nuclear -catenin to the total nuclear -catenin showed that -catenin protein levels were degraded at Indolelactic acid 24 h, whileS-nitrosylation of -catenin occurred earlier at 06 h. The NO scavenger PTIO abrogated the JS-K mediated degradation of -catenin demonstrating the need for NO. Keywords:Leukemia, JS-K,S-nitrosylation, -Catenin, Chemoprevention == 1. Introduction == Acute Lymphoblastic Leukemia (ALL) is the most common malignant disease in children accounting for 70% of all childhood leukemias [1]. ALLs with certain chromosomal translocations constitute a high-risk subgroup of leukemia found in approximately 60% of infants. They are particularly resistant to conventional chemotherapy, thus requiring alternative treatment strategies [2]. Agents that induce nitric oxide SRSF2 (NO) or nitric oxide donors have recently emerged as novel cancer chemopreventive agents. Evidence is accumulating for the role of NO as a new oncopreventive agent and more recently as a novel therapeutic to overcome tumor cell resistance [3]. Nitric oxide can also prevent or stimulate cell death by apoptosis, depending on cell type and dose [4,5]. O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K) is a member of the arylated diazeniumdiolate class of nitric oxide prodrugs that has shown promise as an anti-cancer drug [6,7]. Due to the poor bioavailability of gaseous NO, drugs that release NO such as diazeniumdiolates are used as donors of NO [8]. JS-K has shown potent anti-leukemia activity both in vitro and in vivo using a xenograft model [6]. JS-K has also been shown to inhibit hepatoma Hep 3B cell proliferation [9], enhance arsenic and cisplatin-induced cytolethality in arsenic-transformed rat liver cells [10], and induce apoptosis in human multiple myeloma cell lines [11]. In addition, J-SK was also shown to be effective against leukemia, renal, prostate, and brain cancer cells [12,13]. The protein -catenin is a central player of the Wnt signaling pathway that regulates cellcell adhesion Indolelactic acid and may promote leukemia cell proliferation [14]. It is known that elevated levels of -catenin-targeted genes including cyclin D1 promote genetic instability, leading to tumorigenesis [15,16]. Small molecules modulating the -catenin/TCF-4 signaling pathway are thus attractive as cancer therapeutic agents. In the present study, we aimed to characterize the molecular basis of JS-K action. We specifically tried to delineate whether JS-K may modulate the Wnt/-catenin/TCF-4 signaling pathway, including expression of its downstream target gene, cyclin D1, in Indolelactic acid Jurkat T-ALL cells. -Catenin is expressed in T-ALL cells, tumor lines of hematopoietic origin, and primary leukemia cells but is undetectable in normal peripheral Indolelactic acid blood T cells. JS-K induces differentiation and apoptosis in human myeloid leukemia HL-60 cells [6,9]. However, these cells poorly express -catenin whereas among the leukemia cell lines, -catenin is expressed in high levels in Jurkat T cells [14,17]. Therefore, in the present study we evaluated the effects of the nitric oxide-releasing produg JS-K on -catenin in Jurkat T cells. In view of the fact that the plasma and cellular milieux contain reactive species that can rapidly inactivate NO, it has been postulated that NO is stabilized by a carrier molecule that preserves its biological activity. Reduced thiol species are candidates for this role, reacting readily in the presence of aerobic NO to yield biologically activeS-nitrosothiols that are more stable than NO [18,19]. In this study we examined the effect of JS-K on proliferation and apoptosis in Jurkat T cells and also evaluated whether JS-Ks effects on -catenin could be NO-mediated. == 2. Materials and methods == == 2.1. Reagents and cell culture == O2-(2,4-dinitrophenyl)1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate (JS-K,Fig. 1) was synthesized as previously described [20]. Stock solutions (100 mM) were made in DMSO; final DMSO concentration was adjusted in all media to 1%. Jurkat cells (ATCC TIB-152, Manassas, VA) were grown per ATCC instructions. 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), methylmethanethiosulfate (MMTS), neocuproine, sodium ascorbate, streptavidin-agarose and Hanks balanced salt solution (HBSS) were from Sigma-Aldrich (St. Louis, MO). 3-([3-Cholamidopropyl]dimethylamino)-1-propanesulfonate (CHAPS) and N-[6-(Biotinamido) hexyl]-3 (2-pyridyldithio) propionamide (Biotin-HPDP) were from Thermo Scientific (Rockford, IL). == Fig. 1. == Structure of JS-K (O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate). == 2.2. LDH release assay == For determination of lactate dehydrogenase (LDH) activity, Jurkat cells (1 105cells/well) were incubated in 96-well plates with different concentrations.