Fig. 4.

DDIT4 protects glioblastoma cells from temozolomide, irradiation and hypoxia-induced cell death. a LNT-229 control (Ctr, empty pcDNA3 plasmid) and HA-DDIT4-overepressing cells (pcDNA3 HA-DDIT4 plasmid) (left panel) or G55 DDIT4 Tet-off either in the presence or absence of doxycycline (right panel) were treated with temozolomide as indicated. Clonogenicity is depicted relative to the vehicle control condition (n = 3, mean±SD, NS = not significant, *p < 0.05, **p < 0.01, Student’s t test). b Cells were seeded as in a and exposed to irradiation as indicated. Clonogenicity is depicted relative to the unirradiated control condition (n = 3, mean ± SD, NS = not significant, **p < 0.01, Student’s t test). c G55 DDIT4 Tet-off cells were incubated in serum-free medium or DMEM with 10% FCS without glucose restriction (25 mM glucose) for 4 days under normoxia. Cell density was measured by CV staining after 4 days (n = 6). d G55 DDIT4 Tet-off cells were exposed to glucose-restricted (2 mM glucose) serum-free DMEM under normoxic conditions or 0.1% oxygen either with or without doxycycline (+Doxy and –Doxy, respectively). Cell death was quantified by LDH release (n = 4, mean ± SD, NS = not significant, *p < 0.05, Student’s t test)