USP28 and glioblastoma: circ_FBXW7 expression is positively associated with overall survival in GBM patients, while FBXW7-185aa induces cell cycle arrest and reduces proliferation by competitively interacting with USP28 (ubiquitin specific peptidase 28) and releasing FBXW7α (F-box and WD repeat domain containing 7 alpha) to degrade c-Myc in glioma cells.