Background/aims: The immunosuppressive agent rapamycin is currently being evaluated for its antineoplastic effect. In the present study, the antineoplastic effect of rapamycin against cholangiocarcinoma was studied in vitro.
Methodology: To explore the therapeutic potential of rapamycin, expression of mTOR in four cholangiocarcinoma cell lines--TFK1, HuCCT1, NOZW, and OZ--was evaluated by real-time PCR. The cell lines were then cultured with rapamycin (200 nM), and changes in the expression of Akt, phosphorylated PTEN (pPTEN), and phosphorylated S6 (pS6) were evaluated by western blotting. Finally, the cell lines were cultured with rapamycin (0, 25, 50, 100, 200 nM), gemcitabine (0, 0.5, 1, 2 microM), or both, and the antiproliferative effect was evaluated by MTT assay.
Results: All four cholangiocarcinoma cell lines expressed endogenous mTOR-mRNA, the of expression being highest in HuCCT1 (65.8) and lowest in TFK1 (17.6). Western blotting revealed that rapamycin treatment decreased Akt expression significantly in all four cell lines (TFK1; 15.5%, HuCCT1; 6.3%, NOZW; 9.8%, OZ; 19.5%), and also decreased the expression of p-PTEN (TFK1; 10.6%, HuCCT1; 5.4%, NOZ-W; 12.2%, OZ; 12.2%) and pS6 (TFK1; 64.0%, HuCCT1; 73.9%, NOZW; 78.6%, OZ; 47.6%) in all four cell lines. Finally, rapamycin significantly inhibited the growth of all four cell lines in a dose-dependent manner. Gemcitabine inhibited the growth of NOZW and HuCCT1, but its effect was less marked on TFK1 and OZ. Furthermore, a synergistic anti-proliferative effect of rapamycin and gemcitabine was observed in TFK1, NOZW, and OZ, but not in HuCCT1.
Conclusion: Rapamycin effectively inhibited the growth of the four cholangiocarcinoma cell lines tested, and a synergistic effect with gemcitabine was observed in three of them. Rapamycin offers a new therapeutic strategy to inhibit the growth of cholangiocarcinoma.