MTOR and glioblastoma: As shown in Fig. 6, unlike rapamycin (a specific mTOR inhibitor), melatonin did not reduce the phosphorylation level of mTOR or its substrates, ribosomal S6 protein kinase (p70S6K/p85S6K) and eukaryotic initiation factor 4E-binding protein1 (4E-BP1) in either of the glioblastoma cell lines.