Fig. 4.

PGE₂ signaling regulates self-renewal in mouse glioblastoma (GBM) primary cultures in an Id1-dependent manner. (A) Primary mouse GBM cells treated with 0.5 µM dmPGE₂ were replated at 0.5 cell/µL under nonadherent conditions. The percentage of spheres formed was significantly higher in the dmPGE₂-treated group than for control cells. This stimulatory effect was not seen in Id1 ^−/− , Id3 ^+/− tumor cells, which also displayed notably lower sphere-forming potential. Error bars represent mean ± SEM (n = 3). *, P < .05. (B) Mouse GBM cells were cultured as spheres at clonal density (0.5 cell/uL) under DMSO or 0.5 uM dmPGE₂ treatment and subsequently harvested, dissociated into single cells, and replated under identical conditions. Percentage of sphere-forming cells was quantified at passage 1 and passage 2. Error bars represent mean ± SEM (n = 6). **, P < .01. (C) A significant decrease in sphere-forming potential occurred in GBM cells treated with either 5 µM celecoxib or 1 µM AH23848. Error bars represent mean ± SEM (n = 3). *, P < .05.