Gefitinib and gemcitabine coordinately inhibited the proliferation of cholangiocarcinoma cells.

BACKGROUND Cholangiocarcinoma (CCC) is the second most common type of primary liver cancer, and is associated with a high rate of mortality due to the difficulty of early detection and resistance to chemotherapeutic agents. To evaluate the possibility for new therapeutic strategies, we examined the combined effect of gefitinib and gemcitabine on CCC. MATERIALS AND METHODS The effect of gefitinib, an inhibitor of epidermal growth factor receptor (EGFR) signaling, gemcitabine, which is a pyrimidine analog, and the combined effect of gefitinib and gemcitabine on CCC cells were evaluated both in vitro and in vivo. RESULTS EGFR mRNA expression and phosphorylation of EGFR were elevated in both human CCC cell lines studied, HuCCT1 and RBE, suggesting EGFR signaling is up-regulated in CCC cell lines. Gefitinib treatment at high concentration inhibited the proliferation of the CCC cell lines. Furthermore, gefitinib reduced the transforming growth factor alpha (TGFα)-induced proliferation of these cells. Gemcitabine also suppressed the growth of the CCC cell lines in a concentration-dependent manner. The combination of gefitinib and gemcitabine synergistically suppressed the growth of the CCC cell lines and induced greater apoptosis compared to the use of either agent alone. As a mechanism for this effect, we found less phosphorylation of the extracellular signal-regulated kinase (ERK) protein, which means the suppression of EGFR signaling, when these compounds were administered together. Cell transplantation assay dramatically demonstrated the synergistic effect of this combination on HuCCT1 xenografts in vivo. CONCLUSION The combination of gefitinib and gemcitabine inhibited the proliferation of CCC cells via induction of apoptosis. The combination of EGFR inhibitor and additional chemicals could be a new therapeutic approach for CCC.