PIK3CA and glioblastoma: As shown in Fig. 5c, d and Additional file 3: Figure S3, the γ-H2AX-positive fraction of U251 cells increased significantly upon treatment with BKM120 and TH588 compared with that in cells that received single-agent treatment, suggesting that the combination of PI3K and MTH1 inhibitors dramatically elevates DSB levels in GBM or lung cancer cells.