Figure 2.
(a) Drug resistance of pancreatic cancer cells to 5-FU+GEM. Cultured cells (5 × 103 cells/well) were exposed to graded concentrations of gemcitabine (0, 10−2–104 nM) together with several 5-FU concentrations (0, 0.1, 1.0 μM) for 72 h. Drug resistance was expressed as the concentration of drug that inhibited colony formation by 50% (IC50). The control for each cell line (5-FU, 0 μM) showed statistical significance with each of the same cell lines (∗) (P < .01). (b) Effect of TS expression on GEM resistance. Knockout of TS expression significantly decreased resistance to GEM in pancreatic cancer cells as evidenced by the detected change in IC50s from 77.0 ± 2.6 nM to 7.7 ± 1.1 nM. Results are expressed as mean ± SD. Bar, SD; TS, thymidylate synthase.