Figure 2.

Analysis of irinotecan sensitivity in relation to CES2 activity in pancreatic cancer cell lines. A) Half-maximal inhibitory concentration (IC₅₀) values of irinotecan in pancreatic cancer cell lines. B) Percent survival of pancreatic cancer cell lines after treatment with increasing molar concentrations (log scale) of irinotecan. Curves were fitted by nonlinear regression analysis. C) CES2 activity in pancreatic cancer cell lines. Activity was assessed by monitoring transformation of para-nitrophenolic acetate into its hydrolyzed analogue, para-nitrophenol (p-NP), in the presence or absence of CES2-selective inhibitor, loperamide. Activity is expressed in unit of nmoles of p-NP formed per minute per one mg of cell lysate. D) Pearson’s correlation analysis between irinotecan IC₅₀ and CES2 activity values in pancreatic cancer cell lines. Results are the mean ± SD (error bars) of three independent experiments of five replicates. Two-sided P value was calculated by Pearson’s correlation analysis. IC₅₀ = half-maximal inhibitory concentration; p-NP = para-nitrophenol.