Cordycepin Regulates GSK-3 beta/beta-Catenin Signaling in Human Leukemia Cells

Background: Leukemia stem cells (LSCs) are a limitless cell source for the initiation and maintenance of leukemia. Activation of the Wnt/beta-catenin pathway is required for the survival and development of LSCs. Therefore, targeting beta-catenin is considered a therapeutic strategy for the treatment of leukemia. The goal of this study was to explore whether cordycepin, an active component of the traditional medicine Cordyceps sinensis, regulates beta-catenin expression in leukemia cells. Methodology and Principal Findings: In this study, we found that cordycepin significantly suppressed cell proliferation in all malignant cancer cells, including U937, K562, A549, HepG2, SK-Hep1 and MCF7 in a dose-dependent manner. However, cordycepin reduced beta-catenin levels in U937, K562 and THP1 leukemia cells and had no effect on other solid cancer cells. In addition, treatment with cordycepin significantly suppressed leukemia colony formation in soft agar assay. Cordycepin enhanced proteasome-dependent degradation and inhibited nuclear translocation of beta-catenin in leukemia cells. Cordycepin-reduced beta-catenin stability was restored by the addition of a pharmacological inhibitor of GSK-3 beta, indicating that cordycepin-suppressed beta-catenin stability is mediated by the activation of GSK-3 beta. Furthermore, cordycepin abolished the effect of Wnt3a-induced beta-catenin in leukemia cells. In addition, cordycepin-impaired beta-catenin is regulated by Akt activation but is not significantly influenced by AMPK or mTOR signal pathways. Significance: Our findings show for the first time that codycepin selectively reduces beta-catenin stability in leukemia but not in other solid tumor cells. This suppressive effect is mediated by regulating GSK-3 beta. A synergistic combination of cordycepin with other treatments should be used as a novel strategy to eradicate leukemia via elimination of LSCs