SP1 and glioblastoma: In LN229 and U87MG glioblastoma cells, either tetra-methyl-O-nordihydroguaiaretic acid (M4N) or tetra-acetyl-O-nordihydroguaiaretic acid (A4N) suppressed SP1 and only a few stem cell-related proteins and induced only a small amount of cell death; in contrast, the combination treatment of M4N with A4N greatly suppressed the expression of SP1, MYC, and HIF1A, as well as all of the stem cell-related proteins examined, and greatly induced cell death.