ABSTRACT
Aberrant accumulation of intracellular beta-catenin in intestinal epithelial cells is a frequent early event during the development of colon cancer. To identify small molecules that decrease the level of intracellular beta-catenin, we performed cell-based chemical screening using genetically engineered HEK293 reporter cells to detect compounds that inhibit TOPFlash reporter activity, which was stimulated by Wnt3a-conditioned medium. We found that isoreserpine promoted the degradation of intracellular beta-catenin by up-regulation of Siah-1 in HEK293 and HCT116 colon cancer cells. Moreover, isoreserpine repressed the expression of beta-catenin/T-cell factor (TCF)-dependent genes, such as cyclin D1 and c-myc, resulting in the suppression of HCT116 cell proliferation. Our findings suggest that isoreserpine can potentially be used as a chemotherapeutic agent against colon cancer.
Subject(s)
Antineoplastic Agents/pharmacology , Nuclear Proteins/metabolism , Reserpine/pharmacology , Ubiquitin-Protein Ligases/metabolism , beta Catenin/metabolism , Antineoplastic Agents/chemistry , Antineoplastic Agents/isolation & purification , Gene Expression/drug effects , HCT116 Cells , Humans , Reserpine/chemistry , Reserpine/isolation & purification , Stereoisomerism , Up-Regulation , Wnt Proteins/metabolismABSTRACT
Aberrant activation of Wnt/beta-catenin signaling and subsequent up-regulation of beta-catenin response transcription (CRT) is a critical event in the development of human colon cancer. Thus, Wnt/beta-catenin signaling is an attractive target for the development of anticancer therapeutics. In this study, we identified hexachlorophene as an inhibitor of Wnt/beta-catenin signaling from cell-based small-molecule screening. Hexachlorophene antagonized CRT that was stimulated by Wnt3a-conditioned medium by promoting the degradation of beta-catenin. This degradation pathway is Siah-1 and adenomatous polyposis colidependent, but glycogen synthase kinase-3beta and F-box beta-transducin repeat-containing protein-independent. In addition, hexachlorophene represses the expression of cyclin D1, which is a known beta-catenin target gene, and inhibits the growth of colon cancer cells. Our findings suggest that hexachlorophene attenuates Wnt/beta-catenin signaling through the Siah-1-mediated beta-catenin degradation.
Subject(s)
Anti-Infective Agents, Local/pharmacology , Hexachlorophene/pharmacology , Nuclear Proteins/metabolism , Protein Processing, Post-Translational/drug effects , Signal Transduction/drug effects , Ubiquitin-Protein Ligases/metabolism , Wnt Proteins/metabolism , beta Catenin/metabolism , Cell Proliferation/drug effects , Cells, Cultured , Colonic Neoplasms/pathology , Down-Regulation/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Glycogen Synthase Kinase 3/metabolism , Glycogen Synthase Kinase 3 beta , Hexachlorophene/chemistry , Humans , Nuclear Proteins/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Tumor Suppressor Protein p53/metabolism , Ubiquitin-Protein Ligases/genetics , Wnt3 Protein , Wnt3A Protein , beta Catenin/genetics , beta-Transducin Repeat-Containing Proteins/metabolismABSTRACT
Abnormal activation of the Wnt/beta-catenin pathway and subsequent up-regulation of beta-catenin response transcription (CRT) are associated with the development of colon cancer. Thus, the Wnt/beta-catenin pathway is an attractive target for chemoprevention and treatment of this cancer. We used a cell-based screen to identify a methanol extract of Polysiphonia japonica (EPJ) that suppresses the Wnt/beta-catenin pathway without altering the level of beta-catenin protein and reduces the expression of cyclin D1, which is a known beta-catenin/T cell factor (TCF)-dependent gene. EPJ inhibited the growth of various colon cancer cells. In addition, EPJ induced the nuclear translocation of nuclear factor-kappaB (NF-kappaB) in SW480 colon cancer cells. Our findings suggest that EPJ attenuates Wnt/beta-catenin signaling via activation of NF-kappaB and can potentially be used as a chemopreventive agent against colon cancer.
