Effect of obtusaquinone (OBT) on intracranial glioblastoma (GBM) tumors in vivo. U87 cells expressing Fluc were implanted intracranially in nude mice. One week later, mice were intraperitoneally injected once a day over 14 days with dimethyl sulfoxide (DMSO) (control [Ctrl]) or OBT (7.5mg/kg body weight) (n = 8 per group). A) Mice were imaged weekly, and the Fluc signal was quantified over 5 weeks after implantation. *P < .05, two-sided Student t test. B) At day 21 after implantation, two mice from each group were killed; brains were isolated, sectioned, and analyzed by hematoxylin and eosin staining. Micrographs from one representative mouse per group are shown. Scale bar = 500 µm. C) Kaplan–Meier survival curve for intracranial U87 xenografted mice (n = 6 for control and n = 7 for OBT) with P = .04 (two-sided log-rank test). D) Kaplan–Meier survival curve for intracranial U251 xenografted mice treated with OBT for 21 days (n = 6 for control and n = 8 for OBT) with P = .008 (two-sided log-rank test). The number of mice at risk at any given time point are indicated below the Kaplan–Meir curves in (C and D).