Jf. Liu et al., Functional Rac-1 and Nck signaling networks are required for FGF-2-inducedDNA synthesis in MCF-7 cells, ONCOGENE, 18(47), 1999, pp. 6425-6433
The effects of Fibroblast Growth Factor-2 (FGF-2) on breast cancer cell DNA
synthesis are controversial. To elucidate the mechanisms by which FGF-2 st
imulates or inhibits DNA synthesis, we analysed FGF-2 signaling pathways in
breast cancer MCF-7 and MCF-7 cells overexpressing Ha-Ras (MCF-7ras), We f
ound that FGF-2-induction of DNA synthesis correlates with Ras transient ac
tivation, FRS-2 tyrosine phosphorylation and low level of expression of p66
(She). In addition, Nck-associated proteins are highly tyrosine phosphoryla
ted and JNK reaches a higher level of activation when FGF-2 triggers DNA sy
nthesis. Interestingly upon FGF-2 treatment, JNK activation and DNA synthes
is are dependent on Rac-1 activity. These results confirm that in MCF-7 cel
ls, induction of DNA synthesis by FGF-2 requires a transient activation of
the Ras/MAPK cascade and demonstrates for the first time that intact Rac-1
and Nck signaling networks are required.