Fig. 1

Effect of TMZ on TMZ-sensitive and -resistant U87MG cells in both in vitro and in vivo. (A) The determination of TMZ sensitivity was conducted by assessing the IC50 values for non-treated parent U87MG cells, TMZ-sensitive cells, and TMZ-resistant cells. (B) The proliferation capacity of TMZ-sensitive or -resistant cells was evaluated with a clonogenic assay under gradient TMZ concentrations (0, 200, 400, 600, 800 µM). (C) Cell viability assay results illustrating the optical density (OD) at 450 nm for TMZ-sensitive and -resistant cells following treatment with either DMSO (control) or TMZ (200 µM) within 96 h. (D) Representative fluorescence microscopy images of DAPI/γH2AX staining in TMZ-sensitive and -resistant cells exposed to TMZ (600 µM) for 8 h are presented. The fluorescence of DAPI (blue) and γH2AX (red) indicate the presence of nucleus DNA damage foci, respectively. (E) A quantitative assessment of the DNA damage response in TMZ-sensitive and -resistant cells treated with TMZ was expressed by the mean tail moment of the comet assay. (F) In vivo imaging of tumors in response to TMZ chemotherapy in tumor-bearing mice that had been injected with either TMZ-sensitive or TMZ-resistant cells. All data from more than three independent experiments are presented as SD. A two-tailed t-test was used for comparisons between the two indicated groups (** p < 0.01, *** p < 0.001)