Fig. 1.

High frequency of tumorigenic cells in a murine brain tumor. (A) Development of brain tumors. (i) Gross appearance of a recipient brain. A massive lesion can be seen in the cerebrum. (ii–iv) H&E staining of representative sections of brain tumors. Regions of increased cell density, nuclear pleomorphism, and prominent mitotic figures can be seen. Arrows, giant cells; arrowheads, areas of necrosis with pseudopalisading; asterisks, invading tumor cells adjacent to blood vessels. (Scale bars: 200 μm.) (B) Survival of recipient mice after transplantation of 1,000, 100, or 10 huKO⁺ tumor cells, as indicated.