and antagonist effects as well as purely inhibitory features. Nevertheless, that with the same drug (ATV) both, sigmoidal and biphasic dose-responses occurred for a certain cell-line depending on the kind of formulation (DMSO or A-pBuOzi-A) is somehow surprising and needs to be evaluated further. Important to note, IC 50 of DMSO/ATV for U87 (≈ 8 µM (48 h) or ≈ 1.6 µM (48 h) ) or U251 (≈ 10 µM; 48 h ) cells reported in the literature were somewhat lower than the presently reported ones. However, different experimental setups (# cell passage, number of cells seeded, utilized assays) might have unintentionally caused such minor deviations. Important to note, inhibitory effects of ATV on growth and survival of U251 glioblastoma cells were attributed to decreased active Ras levels due to prenylation inhibition by ATV. In the same study, 5 µM ATV inhibited proliferation of four different glioblastoma cell lines slightly stronger than temozolomide at 10 µM.