Glycogen Synthase Kinase 3β Sustains Invasion of Glioblastoma via the Focal Adhesion Kinase, Rac1, and c-Jun N-Terminal Kinase-Mediated Pathway

The failure of current treatment options for glioblastoma stems from their inability to control tumor cell proliferation and invasion. Biologically targeted therapies offer great hope and one promising target is glycogen synthase kinase-3 beta (GSK3 beta), implicated in various diseases, including cancer. We previously reported that inhibition of GSK3 beta compromises the survival and proliferation of glioblastoma cells, induces their apoptosis, and sensitizes them to temozolomide and radiation. Here, we explore whether GSK3 beta also contributes to the highly invasive nature of glioblastoma. The effects of GSK3 beta inhibition on migration and invasion of glioblastoma cells were examined by wound-healing and Transwell assays, as well as in a mouse model of glioblastoma. We also investigated changes in cellular microarchitectures, cytoskeletal components, and proteins responsible for cell motility and invasion. Inhibition of GSK3 beta attenuated the migration and invasion of glioblastoma cells in vitro and that of tumor cells in a mouse model of glioblastoma. These effects were associated with suppression of the molecular axis involving focal adhesion kinase, guanine nucleotide exchange factors/Rac1 and c-Jun N-terminal kinase. Changes in cellular phenotypes responsible for cell motility and invasion were also observed, including decreased formation of lamellipodia and invadopodium-like microstructures and alterations in the subcellular localization, and activity of Rac1 and F-actin. These changes coincided with decreased expression of matrix metalloproteinases. Our results confirm the potential of GSK3 beta as an attractive therapeutic target against glioblastoma invasion, thus highlighting a second role in this tumor type in addition to its involvement in chemo- and radioresistance. (C)2014 AACR.