Fig. 1

Cytotoxicity of curcumin in RT4 schwannoma cells. a Various concentrations of curcumin (0, 5, 10, 20, and 40 μM) were added to RT4 schwannoma cells and cell viability was assessed. b Various concentrations of Taxol (0, 5, 10, 20, and 40 μM) were added to RT4 cells and the MTT assay was performed. c Curcumin treatment (0, 10, or 20 μM) in RT4 schwannoma cells enhanced the expression of caspase-3, but attenuated proPARP, procaspase-3 and -9. Western blot analyses were performed with antibodies against PARP, caspase-3, caspase-9, and actin. Bar graphs represent the relative expression of proPARP, procaspase-9, or cleaved caspase-3 to β-actin determined using ImageJ software. d Curcumin treatment showed TUNEL-positive activity by microscopy. Fluorescent signals from fragmented DNA (green) and DAPI (blue) were visualized and photographed on a FLUOVIEW FV10i confocal microscope. Bar graph shows the quantitative analyses of apoptosis by the TUNEL assay. Data are presented as the mean ± standard deviation (SD) of triplicate samples. ***p < 0.001, **p < 0.01, and *p < 0.05