When we treated GBM stem cell-like spheroids with low doses of SAHA (1 μM and 2.5 μM), we found that both p53 protein and its phosphorylation at Ser33 were slight increased on 2 days after SAHA treatment, but they were risen significantly after 1 week of treatment (Fig. 5g and h). Here, TP53 is linked to glioblastoma.