Glucocorticoid Receptor ß Acts as a Co-activator of T-Cell Factor 4 and Enhances Glioma Cell Proliferation.

We previously reported that glucocorticoid receptor ß (GRß) regulates injury-mediated astrocyte activation and contributes to glioma pathogenesis via modulation of ß-catenin/T-cell factor/lymphoid enhancer factor (TCF/LEF) transcriptional activity. The aim of this study was to characterize the mechanism behind cross-talk between GRß and ß-catenin/TCF in the progression of glioma. Here, we reported that GRß knockdown reduced U118 and Shg44 glioma cell proliferation in vitro and in vivo. Mechanistically, we found that GRß knockdown decreased TCF/LEF transcriptional activity without affecting ß-catenin/TCF complex. Both GRα and GRß directly interact with TCF-4, while only GRß is required for sustaining TCF/LEF activity under hormone-free condition. GRß bound to the N-terminus domain of TCF-4 its influence on Wnt signaling required both ligand- and DNA-binding domains (LBD and DBD, respectively). GRß and TCF-4 interaction is enough to maintain the TCF/LEF activity at a high level in the absence of ß-catenin stabilization. Taken together, these results suggest a novel cross-talk between GRß and TCF-4 which regulates Wnt signaling and the proliferation in gliomas.