To further understand the relative contributions of p300 and Myc to the astrocytic differentiation of GBM cells, we overexpressed both p300 and Myc in U251 and U87 cells and observed that Myc overrode the p300 functions with respect to both GFAP promoter and Nestin enhancer activities in U251 (Figs. 6A and B) and U87 cells (Figs. 6C and D). This evidence concerns the gene GFAP and glioblastoma.