In order to verify that TYMS expression is involved in the modulation of 5-FU sensitivity in CCA cells, TYMS expression was silenced using siRNA in both the 5-FU-resistant HuCCA and 5-FU-sensitive KKU-D131 cells, and the effects of TYMS knockdown on 5-FU sensitivity investigated using clonogenic assay. Here, TYMS is linked to cholangiocarcinoma.