PMAIP1 and glioblastoma: Counting transfected cells only, pertinently, we saw that knockdown of Noxa significantly attenuated the levels of apoptosis observed following treatment of MZ-294 cells with R-roscovitine alone and R-roscovitine + TRAIL (Fig 6c), demonstrating that Noxa must be present for R-roscovitine and R-roscovitine + TRAIL-induced apoptosis of GBM to proceed.