Figure 1.

Concentration-dependent induction of DNA synthesis by PGE2 in CRC cell lines. A HT-29, Caco-2, Lovo and SW480 cells were seeded in 24-well plates, deprived of serum overnight and challenged with 10% FCS or the indicated doses of PGE2 for further 3 days. Proliferation was scored by [³H]-thymidine incorporation into cellular DNA. Data are mean ± S.E.M. of counts per minute (normalized values to average of control) of tetraplicates of three independent experiments. B Time response of PGE2-induced DNA synthesis. Serum-starved cells were exposed to 10 nM PGE2 for various days and [³H]-thymidine incorporation was monitored and plotted as in A. A more prolonged time response is shown for HT-29 cells in the right panel. Two further experiments yielded similar results. C PGE2-dependent cell proliferation scored by automatic cell counting. Serum-starved HT-29 cells were challenged with varying doses of PGE2 for 7 days and subjected to automatic cell counting as described in the experimental section. Data are mean ± S.E.M. of cells/well of 4 experiments with triplicate measurements. D COX-2 inhibition does not affect PGE2 induced cell proliferation. Serum-starved HT-29 cells were challenged with 10 nM PGE2 or 10% FCS alone or in combination with 10 μM NS398. 4 days later DNA synthesis was assessed as before. Two-sample comparisons (all vs. control) were performed with Student's t test. P values ***P < 0,001, **P < 0,01, *P < 0,05.