Negative growth regulation of SK-N-MC cells by bFGF defines a growth factor-sensitive point in G_2

摘要

Basic fibroblast growth factor (bFGF) has been shown to induce growth inhibition and cell scattering of the neuroepithelioma cell line SK-N-MC. Here we show that this growth inhibition occurs in G_2. We show that bFGF is active on these cells during S and early G_2 phase. Therefore, this constitutes a rather unusual mechanism of growth inhibition, since it is generally believed that cells become refractory to extracellular signals after passage through the restriction point. In addition, we show that bFGF treatment inhibits Tyrl5 dephosphorylation of cdc2, similar to what is seen upon activation of the G_2 DNA damage checkpoint. Interestingly, both DNA damage- and bFGF-induced inhibition of cdc2-Tyr15 dephosphorylation can be reverted by caffeine. Taken together, these data define a growth factor sensitive point in G_2, that might act in a similar fashion as the G_2 DNA damage checkpoint.