Fig. 5

Effects of siramesine in brain slice cultures with spheroids. Spheroids were implanted into organotypic corticostriatal brain slice cultures and exposed to siramesine. a Initially, organotypic corticostriatal brain slice cultures without spheroids were exposed to siramesine and the uptake of propidium iodide (PI) was used to visualize potential siramesine-induced death of normal cultured brain tissue. No PI uptake was seen in control cultures and in cultures exposed to 10 μM siramesine. A pronounced PI uptake was observed with 100 μM siramesine, PI uptake at this concentration exceeded cell death in the N-Methyl-D-aspartate (NMDA) treated cultures used as positive control. NMDA is an excitatory amino acid inducing pronounced neuronal cell death in high concentrations. b Densitometric measurements of PI uptake in both cortex and striatum revealed significant cell death already at day 3 when the brain slice cultures were exposed to both 50 and 100 μM siramesine. Data was normalized to NMDA-induced cell death at day 3 set to 100%. c–d Both T78 (c) and T86 (d) spheroids were implanted into brain slice cultures. The spheroids were labelled with DiO (green) before implantation, whereby tumor cell invasion into the brain slices could be monitored by confocal microscopy. Confocal z-stacks were recorded before (day 0) and 6 days after (day 6) 10 and 100 μM siramesine exposure. Tumor cell invasion was found in controls and at both siramesine concentrations at day 3 and 6 in cultures implanted with both T78 and T86 spheroids. No cell death as visualized by PI uptake was present in spheroids and invasive cells (yellow - overlap between DiO (green) and PI (red)). Results were confirmed by histology in Fig. 6. Control cells received culture medium or DMSO (images not shown) both without siramesine. Scalebar 600 μm (a), Scalebar 100 μm (c–d). Data are displayed as mean values ± SEM, and **P < 0.01, ***P < 0.001 were assessed by one-way ANOVA