Introduction
Glioblastoma (GBM) is the most common and aggressive malignant brain tumor. Forkhead Box M1 (FOXM1) has been shown to regulate cell proliferation, apoptosis, angiogenesis, DNA damage repair and tumorigenesis. The lignin, (−)-(2R,3R)-1,4-O-diferuloylsecoisolariciresinol (DFS), from Alnus japonica (Betulaceae) has shown anti-cancer effects against colon cancer cells by suppressing FOXM1. However, the efficacy of DFS in GBM has not yet been determined. The present study hypothesized that DFS can have anti-cancer effects against GBM tumorspheres (TSs).
Methods
Immunoprecipitation and luciferase reporter assays were performed to evaluate the ability of DFS to suppress nuclear translocation of β-catenin through β-catenin/FOXM1 binding. GBM TSs were treated with DFS to assess the ability of DFS to inhibit GBM TSs and to evaluate their transcriptional profiles. The in vivo efficacy of DFS was examined in orthotopic xenograft models of GBM.
Results
Expression of FOXM1 was higher in GBM than in normal tissues. DFS-induced FOXM1 protein degradation blocked β-catenin translocation into the nucleus and consequently suppressed downstream target genes of FOXM1 pathways. DFS considerably inhibited cell viability and ATP levels in GBM TSs, while increasing the proportion of apoptotic cells. Treatment with DFS also reduced neurosphere formation and the invasive properties of GBM TSs. Transcriptome analyses showed that DFS reduced the activities of transcription factors related to tumorigenesis, stemness, and invasiveness. In addition, DFS significantly inhibited tumor growth and prolonged the survival rate of mice in orthotopic xenograft models of GBM.
Conclusions
DFS inhibits the proliferation of GBM TSs by suppressing FOXM1. These findings suggest that DFS may be a potential therapeutic agent to treat patients with GBM.