Migrating glioma cells activate the PI3-K pathway and display decreased susceptibility to apoptosis

Abstract

Glioma cells that migrate out of the main tumor mass into normal brain tissue contribute to the failure of most gliomas to respond to treatment. Treatments that target migratory glioma cells may enhance the therapeutic response. Multiple lines of evidence suggest that suppression of apoptosis accompanies activation of the migratory phenotype. Here, we determine whether migration and apoptosis are consistently linked in glioma cells and whether manipulation of migration influences cytotoxic therapy-induced apoptosis. Camptothecin and Trail-induced apoptosis were decreased 2-5-fold in actively migrating glioma cells relative to migration-restricted cells. Consistent with a mechanistic link between migration and apoptosis, the dose-response for stimulation of migration on laminin was inversely proportional to apoptosis induction. Treatment of glioma cells with migration inhibitors alone had little effect on basal rates of apoptosis and had little effect on Trail-induced or camptothecin-induced apoptosis in migration-restricted cells. By contrast, migration inhibitors increased camptothecin and Trail-induced apoptosis in actively migrating glioma cells. Migrating glioma cells have increased amounts of phosphorylated Akt and its downstream substrate glycogen synthase kinase-3 relative to migration restricted cells. Treatment of migrating cells with a specific inhibitor of phosphoinositide 3-kinase (PI3-K), LY294002, blocked the phosphorylation of Akt and increased the sensitivity to apoptosis. LY294002 had no effect on the migration of restricted cells. This suggests that migrating glioma cells activate the PI3-K survival pathway, protecting migrating cells from apoptosis. Taken together, these data provide support for a link between migration and apoptosis in glioma cells. In addition, evidence indicates that treatment with migration inhibitors, while not affecting apoptosis-induction in migration-restricted cells, can sensitize migrating glioma cells to cytotoxic agents.

Correlation of in vitro infiltration with glioma histological type in organotypic brain slices

“…There is evidence that migrating cells do not proliferate (Giese et al, 1996) because they downregulate genes involved in cell proliferation (Mariani et al, 2001). The concomitant upregulation of antiapoptotic programmes (Mariani et al, 2001;Joy et al, 2003) indicates that these nondividing cells may also be longer-lived. This particular kinetic profile of migrating cells should be taken into account by models studying the relationships between the infiltration and proliferation determinants of glioma growth.…”

The Tumor Necrosis Factor-like Weak Inducer of Apoptosis (TWEAK)-Fibroblast Growth Factor-inducible 14 (Fn14) Signaling System Regulates Glioma Cell Survival via NFκB Pathway Activation and BCL-XL/BCL-W Expression

“…Apoptosis Assays-Apoptotic cells were evaluated by nuclear morphology of DAPI-stained cells as described previously (40). Briefly cells with condensed, fragmented chromatin were manually scored as apoptotic cells.…”

Developing a Novel Embryo–Larval Zebrafish Xenograft Assay to Prioritize Human Glioblastoma Therapeutics

“…[34][35][36] PTEN dephosphorylates phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5)-P 3 )-mediated activation of serine/threonine kinase (AKT), thereby controlling cell proliferation, survival, migration, and invasion. 22,30,37 Inhibiting PI 3-kinase activity with LY294002 decreases glioblastoma proliferation, migration, and invasion by mitigating enhanced AKT phosphorylation.…”

“…This suggests that identifying therapeutics that inhibit glioblastoma migration and invasion may be important in sensitizing glioblastoma to apoptosis. 22 This embryo-larval zebrafish xenograft model allows for identification of anti-invasive as well as antiproliferative therapeutics in one assay, which is very challenging in orthotopic rodent models.…”

“…We validated the sensitivity of the assay through testing the selective phosphatidylinositide 3-kinase (PI 3-kinase) inhibitor LY294002, known to inhibit glioblastoma proliferation, migration, and invasion in both cell culture and rodent xenograft models. [20][21][22] We also assessed novel zinc oxide nanoparticles (ZnO NPs), which demonstrate selective toxicity toward cancer cells in vitro, 23 for conserved preferential anticancer efficacy in vivo in this refined zebrafish xenograft assay.…”