Expression of some proteins in tumourspheres. Tumourspheres from glioblastoma were mainly negative for the aquaporins 4 and 9 but were positive for immature and glial markers. (a, b) A few tumourspheres were weakly positive for aqp4 (a, red) but most were negative (b). (c) Few sphere cells were found to express aqp9. (d) Many sphere cells expressed aqp1. (e) A sphere showing the immature markers nestin (green) and Sox2 (red). (f) A sphere stained for nestin (green) and GFAP (red). Scale bars: (a, b, d, and e) 20 μm; (c) 50 μm.