Figure 2
Pharmacological inhibitors of IP 3 Rs inhibited 5-FCS- and E 2 -induced MCF-7 cell growth. (A) The growth of MCF-7 cells induced by a 48 h treatment with 5-FCS was sensitive to pharmacological inhibitors of IP3R. Left bar graph shows the cell number obtained in 0-FCS and serves as a control experiment in order to estimate the proliferative effect of 5-FCS. Caffeine (500 μM) and 2-APB (75 μM) were both able to inhibit significantly 5-FCS-stimulated cell growth (P < 0.05 and P < 0.001, respectively). Values are the mean ± S.E.M. of 6 independent experiments. (B) Pharmacological inhibition of IP3R was responsible for the inhibition of E2-induced cell growth. Whereas caffeine (500 μM) was ineffective alone in control conditions, it inhibited the stimulation of cell growth by E2 (10 nM, P < 0.01). Values are the mean ± S.E.M. of 3 independent experiments. (C) XeC (10 μM) inhibited both 5-FCS and E2-induced MCF-7 cell growth. Values are the mean ± S.E.M. of 4 independent experiments. (D) Kinetics and reversibility of the inhibition by caffeine of E2-induced MCF-7 cell viability. Cells were starved for a 24 h period and were then stimulated by 10 nM E2. Caffeine (500 μM) was either added (+caf) at the beginning of the experiment (a), or after 36 h (b). In both cases, caffeine inhibited the E2-induced increase in cell viability (P < 0.001). The effect of caffeine was reversible since washout (-caf) of this compound after 36 h permitted to significantly restore the proliferative effect of E2 at 72 h (c). Arrows indicate the time of application (downward) or washout (upward) of caffeine. Values are the mean ± S.E.M. of 3 independent experiments.