Possible Involvement of Cyclophilin A Processing in Fumagillin-Induced Suppression of Cholangiocarcinoma Cell Proliferation

Methionine aminopeptidase 2 (MetAP2), a proteolytic enzyme that removes the N-terminal methioninefrom newly synthesized cellular proteins, plays roles in the development of various cancers and has been foundto be over-expressed in cholangiocarcinoma (CCA). Fumagillin, a specific MetAP2 inhibitor, suppresses CCAcell proliferation. In order to determine the molecular mechanisms involved in the suppression of CCA cellproliferation caused by fumagillin, proteomic analysis was performed on fumagillin-treated CCA cells. Proteinsaffected by fumagillin were analyzed using 2D gel electrophoresis and matrix-assisted laser desorption ionizationtimeof flight tandem mass spectrometry (MALDI-TOF/TOF). The results showed that the processed form ofcyclophilin A (CypA) was greatly decreased in parallel with the suppression of CCA cell proliferation. Theseresults suggest that CypA is possibly a protein substrate of MetAP2 cleavage. Removal of N-terminal methionineby MetAP2 may be essential for proper function of CypA in CCA cell proliferation. MetAP2 and CypA maythus serve as potential therapeutic targets for CCA treatment.