Figure 1.

LB-100 sensitized effects of radiation in vitro. (A) Three meningioma cell lines IOMM-LEE, GAR and CH-157 were used in vitro. XTT assays were performed after 48 hours of treatment. Increasing concentrations of LB-100 reduced cell viability, but cytotoxic effect was seen only at high drug concentration with IC50>10uM. (B) The effects of LB-100 on radiosensitivity of IOMM-LEE and GAR cells were demonstrated by clonogenic assay. Cells were seeded as a single-cell suspension with a specified number of cells. After allowing cells time to attach (6 hours), 2.5 uM of LB-100 was added and the plates were irradiated 3 hours later. Ten days after seeding, survival curves were generated by counting colonies with >50 cells. The surviving fractions of meningioma cells at various doses of irradiation ± 2.5 uM of LB-100 were compared. Data are representative of 2 independent experiments. (C) SER was calculated as the radiation dose needed for radiation only divided by the dose needed for 2.5 uM of LB-10 with radiation at surviving fraction of 0.5 (SF0.5). Data are the mean ± SEM from two independent experiments. P values were determined by student t-test. (D) In vitro PP2A activity of IOMM-LEE and GAR cells are shown. LB-100 (2.5 uM) was given 3 hours prior to RT (5Gy). PP2A activity was then assessed 3 hours after RT. PP2A activity was measured based on phosphatase assay and expressed as ratio relative to control. LB-100 inhibited RT induced increase in PP2A activity. Data are representative of two independent experiments.