Fig. 3.

Long-term in-vitro culture and in vivo serial transplantation of PDGF-induced AOL-like tumor cells. a1–3 GFP-positive tumor cells are enriched in the course of long term culture (a1 GFP-immunocytochemistry, a2 nuclear staining with DAPI, a3 merged image). Scale bar 20 μm. b–d Histological changes in the tumor tissues over a series in-vivo transplantations (b1–3 the first-generation tumor, c1–3 the second-generation tumor, d1–6 the fourth-generation tumor). While the first-generation tumor showed diffuse proliferation of the tumor cells with round, monomorphous nuclei and perinuclear halo (b1), the second-generation tumor shows the presence of giant tumor cells (c1, arrowheads). Most of the tumor cells are immunopositive for Olig-2 throughout the generations (b2, c2, d2). The first generation tumor contains a subset of proviral HA-expressing tumor cells (b3), however, in the second generation and thereafter, most of the tumor cells show diffuse HA expression (c3, d3). The fourth generation tumor focally shows increased nuclear polymorphism (d1) and the presence of bizarre, multinucleated giant cells (d4). A fraction of giant tumor cells strongly express GFAP (d5, arrowhead). There are giant tumor cells with proliferative activity as revealed by PCNA-immunostaining (d6, arrowheads). Scale bar 50 μm