PLD1 and glioblastoma: Although TMZ, TMZ/IR, or TMZ/IR/vorinostat did not affect the sphere‐forming capacity of GBM‐MES‐83 cells, a combination of TMZ/IR/vorinosta/PLD1 inhibitor significantly suppressed the mean sphere‐forming capacity of GBM compared with that of PLD1 inhibitor alone (Figure 6e).