Effect of rapamycin on GSPC self-renewal. A, rapamycin attenuated the efficiency of neurosphere formation of GSPCs. The percentage of neurosphere-forming cells and the total number of cells were determined. B, representative images of SU-2 neurospheres treated as indicated. The neurosphere is significantly smaller in the rapamycin group than in control group and 3-MA plus rapamycin group, suggesting that rapamycin reduced the self-renewal ability of GSPCs and that 3-MA blocked this effect.