Cell proliferation at the tumor periphery in glioma xenografts.

<p>Confocal composite image of U251 human glioma xenografts in mice (<b>A</b>, <b>B</b>, <b>C</b>), and biopsy GBM spheroid xenografts in rats (<b>D</b>, <b>E</b>, <b>F</b>). Low magnification image shows a halo of host nestin positive cells (green) surrounding the tumor. Note the macroscopically demarcated border toward the brain tissue (<b>A</b>). Immunostaining of PCNA (red) at the tumor periphery and peritumor region indicates active proliferation in these areas (arrows). Higher magnification from panel <b>A</b> reveals that the majority of dividing cells are in the tumor, but some nestin-positive host cells in the peritumor brain tissue stain are also dividing (<b>B</b>). Extensive proliferation of host nestin-positive cells in the mouse subventricular zone ipsilateral to the tumor (<b>C</b>). Photomicrographs taken at the tumor periphery (lower right side of images, marked ‘tu’) and the surrounding brain tissue (upper left side of the images) reveal proliferating cells (Ki-67, green). Again, the majority of proliferating cells are in the tumor, but proliferating cells are also in the adjacent brain (<b>D</b>, <b>E</b>). Magnified image from <b>E</b> showing double-labeled dividing (Ki-67, green nuclei) rat nestin-positive cells (red cytoplasm) (<b>F</b>). <i>Bars</i> F 10 µm, <b>D</b>, <b>E</b>, <b>B</b> insert, <b>C</b> insert 50 µm, <b>B</b>, <b>C</b> 100 µm, <b>A</b> 1 mm.