Evaluation of anti-Wnt/β-catenin signaling agents by pGL4-TOP transfected stable cells with a luciferase reporter system

Refractory and relapsed leukemia is a major problem during cancer therapy, which is due to the aberrant activation of Wnt/β-catenin signaling pathway. Activation of this pathway is promoted by wingless (Wnt) proteins and induces co-activator β-catenin binding to lymphoid enhancer factor (LEF)/T-cell factor protein (TCF). To provide a convenient system for the screening of anti-Wnt/β-catenin agents, we designed a bi-functional pGL4-TOP reporter plasmid that contained 3X β-catenin/LEF/TCF binding sites and a selectable marker. After transfection and hygromycin B selection, HEK 293-TOP and Jurkat-TOP stable clones were established. The luciferase activity in the stable clone was enhanced by the recombinant Wnt-3A (rWnt-3A; 100-400 ng/mL) and GSK3β inhibitor (2’Z,3’E)-6-bromoindirubin-3’-oxime (BIO; 5 µM) but was inhibited by aspirin (5 mM). Using this reporter model, we found that norcantharidin (NCTD; 100 µM) reduced 80 percent of rWnt-3A-induced luciferase activity. Furthermore, 50 µM NCTD inhibited 38 percent of BIO-induced luciferase activity in Jurkat-TOP stable cells. Employing ³H-thymidine uptake assay and Western blot analysis, we confirmed that NCTD (50 µM) significantly inhibited proliferation of Jurkat cells by 64 percent, which are the dominant β-catenin signaling cells and decreased β-catenin protein in a concentration-dependent manner. Thus, we established a stable HEK 293-TOP clone and successfully used it to identify the Wnt/β-catenin signaling inhibitor NCTD.

Evaluation of anti-Wnt/ß-catenin signaling agents by pGL4-TOP transfected stable cells with a luciferase reporter system.

Refractory and relapsed leukemia is a major problem during cancer therapy, which is due to the aberrant activation of Wnt/ß-catenin signaling pathway. Activation of this pathway is promoted by wingless (Wnt) proteins and induces co-activator ß-catenin binding to lymphoid enhancer factor (LEF)/T-cell factor protein (TCF). To provide a convenient system for the screening of anti-Wnt/ß-catenin agents, we designed a bi-functional pGL4-TOP reporter plasmid that contained 3X ß-catenin/LEF/TCF binding sites and a selectable marker. After transfection and hygromycin B selection, HEK 293-TOP and Jurkat-TOP stable clones were established. The luciferase activity in the stable clone was enhanced by the recombinant Wnt-3A (rWnt-3A; 100-400 ng/mL) and GSK3ß inhibitor (2'Z,3'E)-6-bromoindirubin-3'-oxime (BIO; 5 µM) but was inhibited by aspirin (5 mM). Using this reporter model, we found that norcantharidin (NCTD; 100 µM) reduced 80% of rWnt-3A-induced luciferase activity. Furthermore, 50 µM NCTD inhibited 38% of BIO-induced luciferase activity in Jurkat-TOP stable cells. Employing ³H-thymidine uptake assay and Western blot analysis, we confirmed that NCTD (50 µM) significantly inhibited proliferation of Jurkat cells by 64%, which are the dominant ß-catenin signaling cells and decreased ß-catenin protein in a concentration-dependent manner. Thus, we established a stable HEK 293-TOP clone and successfully used it to identify the Wnt/ß-catenin signaling inhibitor NCTD.

Seselin from Plumbago zeylanica inhibits phytohemagglutinin (PHA)-stimulated cell proliferation in human peripheral blood mononuclear cells.

Effects of seselin (C(14)H(12)O(3); MW 228) identified from Plumbago zeylanica on phytohemagglutinin (PHA)-stimulated cell proliferation were studied in human peripheral blood mononuclear cells (PBMC). The data demonstrated that seselin inhibited PBMC proliferation-activated with PHA with an IC(50) of 53.87+/-0.74 microM. Cell viability test indicated that inhibitory effects of seselin on PBMC proliferation were not through direct cytotoxicity. The action mechanisms of seselin may involve the regulation of cell cycle progression, interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production in PBMC. Since cell cycle analysis indicated that seselin arrested the cell cycle progression of activated PBMC from the G(1) transition to the S phase. Seselin suppressed IL-2 and IFN-gamma production in a concentration-dependent manner. Furthermore, seselin significantly decreased the IL-2 and IFN-gamma gene expression in PHA-activated PBMC. Therefore, results elucidated for the first time that seselin is likely an immunomodulatory agent for PBMC.