Henryin, an ent-kaurane Diterpenoid, Inhibits Wnt Signaling through Interference with β-Catenin/TCF4 Interaction in Colorectal Cancer Cells

Aberrant Wnt/beta-catenin signaling has been strongly associated with the tumorigenesis of human colorectal cancer. Inhibitors of this pathway may then offer therapeutic strategies as well as chemoprevention for this malignant disease. Henryin is an ent-kaurane diterpenoid isolated from Isodon rubescens var. lushanensis, a plant long been used in folk medicine to prevent inflammation and gastrointestinal disease. In the present study, we report that henryin selectively inhibits the proliferation of human colorectal cancer cells with a GI(50) value in the nano-molar range. Microarray analysis and reporter assays showed that henryin worked as a novel antagonist of Wnt signaling pathway. Henryin reduced the expression of Cyclin D1 and C-myc, and induced G1/S phase arrest in HCT116 cells. Concurrently, henryin did not affect the cytosol-nuclear distribution of soluble beta-catenin, but impaired the association of beta-catenin/TCF4 transcriptional complex likely through directly blocking the binding of beta-catenin to TCF4. We also then analyzed the structure-activity relationship among the ent-kaurane type diterpenoids. Our data suggests that henryin, as a novel inhibitor of Wnt signaling, could be a potential candidate for further preclinical evaluation for colon cancer treatment, and as such warrants further exploration.