Figure 3.

Dissociation of uPA upregulation from mitogenicity in L6 transfectants. (A) wt-FGFR1 (•), FGFR1–3F (▴), and FGFR1–4F (▾) cell lines were stimulated with FGF2. Cell-associated uPA activity was evaluated after 24 h. For each cell line, uPA activity measured in corresponding nonstimulated cells (ranging from 0.1 to 0.2 OD at 405 nm) was subtracted from all the values. (B) Parallel cultures were incubated overnight in the absence or presence of 10 ng/ml FGF2. Then, total RNA was extracted and analyzed by Northern blot using a murine uPA probe. Uniform loading of the gel was judged by methylene blue staining of the filter (28S). (C) Parental L6 myoblasts (1), wt-FGFR1 (2), FGFR1–3F (3), and FGFR1–4F (4) cell lines were seeded in 48-well plates, starved for 48 h in the presence of 0.1% FCS, and treated with 30 ng/ml FGF2 (gray bar) or vehicle (open bar) for 20 h. Then [³H]thymidine was added, and 6 h later samples were collected and [³H]thymidine incorporation was evaluated. Data are the mean ± SD of three determinations.