Fig. 3.

TGF-β induced MT formation is associated with invasion. (a) GG6 GBM cells are not responding to TGF-β1 stimulation with increased MT formation in contrast to GG16 GBM cells. Immunofluorescence stainings for nestin are shown. Black and white pictures are presented to better visualize the MT network. Quantification of connections per cell and MT length is presented. Scale bar 20 µm. *P < .05; **P < .01; ***P < .001; ****P < .0001. (b) Invasion of GG16 GBM cells into brain organoids is inhibited by LY2157299. TGF-β stimulation does not significantly increase invasion most likely due to the presence of TGF-β in the microenvironment. In contrast, nonresponder GG6 GBM cells do not show significant invasion into brain organoids. Immunofluorescence pictures of organoids after 72 h showing green fluorescent protein (GFP) signal (GBM cells). Higher magnifications of the invasive areas are provided below each organoid picture. Quantification of invasive cells is provided after 24, 48, and 72 hours. Scale bar 70 µm (zoom 14 µm). Statistically significant differences of experimental groups compared to the control are shown on top of the respective bars. *P < .05; **P < .01; ***P < .001. (c) Immunohistochemical staining of GG6 and GG16 patient and xenograft GBM with nestin antibodies showing an extensive MT network in GG16, which is low to absent in GG6. Quantification of MT density is provided. Scale bar 100 µm (zoom 10 µm). Abbreviations: GBM, glioblastoma; MT, microtube; TGF-β, transforming growth factor-beta.