To investigate whether the inhibitory activity of β-eudesmol on NQO1 activity and protein expression in the CCA cells resulted in an enhanced sensitivity of the cells to chemotherapeutic agents, the KKU-100 cells were incubated with β-eudesmol in the absence and presence of 5-FU or DOX for 24 or 48 h. The gene discussed is NQO1; the disease is cholangiocarcinoma.