Increased cytotoxicity of ionizing radiation in combination with ErPC in U87MG cells. U87MG cells were irradiated with a single dose of 0, 2.5, 5 or 10 Gy and subsequently treated with 0, 50, 75 or 100 μM ErPC as indicated. Induction of cell death was quantified 24 h, 48 h and 72 h after treatment by fluorescence microscopy counting the cells with apoptotic and necrotic morphology upon combined staining with Hoechst 33342 and PI. The percentage of viable cells was calculated as indicated in Fig.1. Data show (A) one representative of three independent experiments or (B, C, D) means ± s.d.; n = 3. (A) Morphologic appearance of U87MG cells upon treatment with medium (control), 10 Gy, 75 μM ErPC or 10 Gy and 75 μM ErPC. (B) Concentration- and dose-dependent increase in cytotoxic efficacy of the combination. (C and D) Time-dependent increase in cytotoxicity of ErPC in combination with 10 or 5 Gy.