Fig. 2. Colony formation and tumorigenesis assays. (A) Cells were grown in soft agarose gel. Vector-transfected U87 cells formed colonies but G3EGF-transfected U87 cells did not. Each treatment was done in triplicate wells and the experiment was repeated twice. (B) Both vector- and G3EGF-transfected cells were injected into the nude mice at 10⁷ cells per mouse. Six weeks after injection, tumors were formed by vector-transfected cells (arrows) but not by G3EGF-transfected cells. The photos are results from one experiment. The tumor sizes were measured, and the results from two experiments are given in (C).