Protein Kinase C-α–Mediated Regulation of Low-Density Lipoprotein Receptor–Related Protein and Urokinase Increases Astrocytoma Invasion
Aggressive and infiltrative invasion is one of the hallmarks of glioblastoma. Low-density lipoprotein receptor–related protein (LRP) is expressed by glioblastoma, but the role of this receptor in astrocytic tumor invasion remains poorly understood. We show that activation of protein kinase C-α (PKC-α) phosphorylated and down-regulated LRP expression. Pretreatment of tumor cells with PKC inhibitors, phosphoinositide 3-kinase (PI3K) inhibitor, PKC-α small interfering RNA (siRNA), and short hairpin RNA abrogated phorbol 12-myristate 13-acetate–induced down-regulation of LRP and inhibited astrocytic tumor invasion in vitro. In xenograft glioblastoma mouse model and in vitro transmembrane invasion assay, LRP-deficient cells, which secreted high levels of urokinase-type plasminogen activator (uPA), invaded extensively the surrounding normal brain tissue, whereas the LRP-overexpressing and uPA-deficient cells did not invade into the surrounding normal brain. siRNA, targeted against uPA in LRP-deficient clones, attenuated their invasive potential. Taken together, our results strongly suggest the involvement of PKC-α/PI3K signaling pathways in the regulation of LRP-mediated astrocytoma invasion. Thus, a strategy of combining small molecule inhibitors of PKC-α and PI3K could provide a new treatment paradigm for glioblastomas.
Glioblastoma multiforme, brain tumor invasion, urokinase, PKC, LRP brain/central nervous system cancers, tumor microenvironment and modification
Amos, Samson; Mut, Melike; diPierro, Charles G.; Carpenter, Joan E.; Xiao, Aizhen; Kohutek, Zachary A.; Redpath, Gerard T.; Zhao, Yunge; Wang, Jiahu; Shaffrey, Mark E.; and Hussaini, Isa M., "Protein Kinase C-α–Mediated Regulation of Low-Density Lipoprotein Receptor–Related Protein and Urokinase Increases Astrocytoma Invasion" (2007). Pharmaceutical Sciences Faculty Publications. 94.