Gemcitabine, a pyrimidine analog, also inhibits the growth of CC cells in a concentration-dependent manner, and the combination of gefitinib and gemcitabine showed a synergistic effect in suppressing the tumor growth of CC cells in vivo and in vitro through significant inhibition of EGFR/ERK1/2 activation relative to treatment with either gefitinib or gemcitabine alone [137]. Here, EGFR is linked to cholangiocarcinoma.