Table 2.

Percent BrdUrd incorporation

Condition	Serum-free media	10% serum	EGF, 10 ng/ml	PDGF-BB, 10 ng/ml	PDGF-BB, 50 ng/ml
U87MG	19.4  ±  4.9	90.5  ±  7.8	45.5  ±  0.9	22.7  ±  4.4	36.9 ± 6.8
U87/T691-1	15.4  ±  0.7	83.6  ±  0.4	17.3  ±  7.0	19.5  ±  6.2	30.5 ± 4.7

DNA synthesis in response to either EGF or PDGF-BB for U87MG cells and U87/T691-1 cells (expressing the T691stop truncated form of Neu) is shown. After starvation in serum-free media for 48 hr, cells were either placed back into serum-free media, 10% FBS DMEM (complete growth media), or ligand in serum-free media at the indicated concentration for 24 hr. BrdUrd incorporation was determined by immunohistochemistry and positive cells were counted as described in Materials and Methods. The data shown are mean ± SD for triplicate samples. Similar results were observed in three independent experiments. The results of this representative experiment were confirmed by an independent observer.