Cancer Prevention Research Deguelin Inhibits Growth of Breast Cancer Cells by Modulating the Expression of Key Members of the Wnt Signaling Pathway

An emphasis in early detection and more effective treatments has decreased the mortality rate of breast cancer. Despite this decrease, breast cancer continues to be the leading cause of death among women between 40 and 55 years of age and is the second overall cause of death among women. Hence, the aim of the present study was to assess the therapeutic efficacy of deguelin, a rotenoid isolated from several plant species, which has been reported to have chemopreventive and/or chemotherapeutic effects in skin, mammary, colon, and lung cancers. The effect of deguelin on cell proliferation was evaluated using four human breast carcinoma cell lines (MCF-7, BT474, T47D, and MDA-MB-231) by cell count and MTT. Moreover, apoptosis was evaluated by acridine/ethidium staining and DNA laddering. Gene expression changes following deguelin treatment in MDA-MB-231 cells was assessed through microarray analysis. Deguelin at 1 μmol/L was found to inhibit the growth of the breast cancer cell lines tested with a range of 37% to 87%. The highest inhibition was noted for the MDA-MB-231 cell line (MDA-MB-231>BT474>MCF7>T47D>MCF12F). An arrest at the S phase of the cell cycle and apoptosis were shown in the MDA-MB-231 cells treated with deguelin. The microarray profile indicated differential expression of two independent pathways, including clusters of apoptosis and Wnt/β-catenin signaling genes in cells as a result of deguelin treatment. These studies support the antiproliferative effects of deguelin in human breast cancer cells and, perhaps more importantly, illustrate novel actions by deguelin in the Wnt signaling pathway. Despite advances in novel therapeutic agents, breast cancer remains the second leading cause of malignancy-related death in women in the United States. Part of the cause may be related to the fact that the most widely used drugs, including tamofixen and aromatase inhibitors, work by blocking the ability of estrogen to trigger abnormal cell growth. Yet, some 65,000 breast cancer cases or about one third are considered as estrogen receptor (ER)–negative tumors; thus, medications that work by blocking estrogens have little effect on the incidence of cancers that are not sensitive to the hormone. As a result, women with ER-negative breast tumors find themselves in an especially grave need for safe and efficacious therapy. The discovery of agents that regulate biological pathways unrelated to hormone receptor status may provide new avenues for the treatment of breast cancer. The canonical Wnt signaling pathway is highly conserved in evolution, widely used throughout development, and frequently hyperactive in cancer. This pathway involves numerous proteins that control the production and destruction of Wnt signaling molecules, their interactions with crucial receptors, and the actions of target cells exposed to Wnt ligands (1, 2). In the last decade, research in this pathway has continued to expand and as a result the known components in or associated with the canonical Wnt signaling pathway has grown considerably with >50 proteins currently known to be associated with the pathway (3, 4). A large part of the research has focused on β-catenin, a transcription factor of the canonical Wnt signaling pathway. In the absence of ligand, cytoplasmic β-catenin interacts with APC and Axin and serves as a substrate for the kinases CKI and GSK3β. Phosphorylated β-catenin is then ubiquitinated and destroyed by the proteosome (3). When Wnt ligand binds to a Frizzled family receptor and a coreceptor (LRP-5 or LRP-6), the APC/Axin/CK1/GSK3β destruction complex is inhibited, leading to the stabilization of β-catenin and its translocation to the nucleus where it interacts with T-cell factor/lymphoid enhancer factor (TCF/LEF) family transcription factors. In the absence of signal, TCF/LEF factors bind DNA at Wnt-responsive genes and interact with other factors (e.g., Groucho, histone deacetylase) to repress transcription. β-Catenin binding to TCF/LEF proteins provides a transcription activation domain, which leads to target gene expression and/or activation. Authors' Affiliations: Division of Carcinogenesis and Chemoprevention, IIT Research Institute, Chicago, Illinois, and GenUs BioSystems, Northbrook, Illinois Received 12/9/08; revised 5/19/09; accepted 6/3/09; published OnlineFirst 10/27/09. Grant support: Penny Severns Breast Cancer and Cervical Cancer Research Fund, Illinois Department of Public Health. Requests for reprints: Rajendra G. Mehta, IIT Research Institute, 10 West 35th Street, Chicago, IL 60616. Phone: 312-567-4970; Fax: 312-567-4931; E-mail: [email protected]. ©2009 American Association for Cancer Research. doi:10.1158/1940-6207.CAPR-08-0232 942 Cancer Prev Res 2009;2(11) November 2009 www.aacrjournals.org Published Online First on October 27, 2009 as 10.1158/1940-6207.CAPR-08-0232 Cancer Research. on June 15, 2017. © 2009 American Association for cancerpreventionresearch.aacrjournals.org Downloaded from Published OnlineFirst October 27, 2009; DOI: 10.1158/1940-6207.CAPR-08-0232