SP1 and glioblastoma: Sp1 knockdown significantly increased the radiosensitivity of all the GBM cell lines, and the sensitizer enhancement ratios at 10% survival level (SER10) were 1.34, 1.32, 1.42 and 1.41 for U87, T98G, M059K and U251 cells, respectively (Figure 3B,D,F,H).