Antitumor effects of flavopiridol, a cyclin-dependent kinase inhibitor, on human cholangiocarcinoma in vitro and in an in vivo xenograft model

Flavopiridol, a pan-cyclin-dependent kinase (CDK) inhibitor, was recently identified as an effective antitumor agent for several cancers. We investigated the antitumor effect of flavopiridol on cholangiocarcinoma (CCA), in vitro and in vivo. A methylthiotetrazole assay revealed that the proliferation of certain CCA cells was inhibited by flavopiridol, which induced the caspase-dependent apoptosis of CCA cells. Although increased cell cycle arrest was observed at the G2/M phase, caspase activation occurred earlier than 24 h, indicating that caspase-dependent apoptosis is the major pathway for the suppression of cell proliferation. Flavopiridol potently reduced the CCA tumor growth in a xenograft model without observable adverse effects. These findings indicated that flavopiridol could be a potential antitumor agent for the treatment of CCA.