Increased induction of apoptosis contributes to increased efficacy of the combination. (A, B) T98G cells were treated with a single dose of 10 Gy and subsequently treated with 0, 12.5, 25 or 50 μM ErPC or ErPC3 as indicated. The amount of apoptotic and necrotic cells was determined 48 h after treatment by fluorescence microscopy upon staining with Hoechst33342 and PI and counting of the cells with apoptotic morphology and necrotic morphology, respectively. (C) T98G cells were treated with a single dose of 5 Gy and subsequently treated with 0 or 25 μM ErPC. Cleavage of the caspase-3 substrate PARP was determined by Western blotting of cytosolic extracts obtained 24 h after treatment. (A) Dose dependent increase in the percentage of apoptotic and necrotic T98G cells upon combined treatment with increasing concentrations of ErPC and 10 Gy. (B) Efficient Increase in the percentage of apoptotic T98G cells upon combined treatment with ErPC3 and 10 Gy. (C) Improved cleavage of PARP upon combined treatment with 25 μM ErPC and 5 Gy. Data show (A, B) means ± s.d., n = 3 or (C) one representative of three independent experiments.