Alpha-fetoprotein producing cells act as cancer progenitor cells in human cholangiocarcinoma

We aimed to demonstrate that alpha-fetoprotein (AFP)-producing cells in cholangiocarcinomas possessed cancer stem cell (CSC)-like properties. AFP enhancer/promoter-driven EGFP gene was transfected into human cholangiocarcinoma cell lines. One cell line, RBE, expressed both AFP and EGFP. Clonal analyses revealed that one EGFP-positive cell generated both EGFP-positive and EGFP-negative cell fractions. However, one EGFP-negative cell never produced EGFP-positive cells. The EGFP-positive cells had a greater tumorigenic potential. Only the EGFP-positive cells expressed Notch1. AFP and Notch1 expression was observed in clinical intrahepatic cholangiocarcinomas. The AFP-producing cells were suggested to be CSCs. The Notch pathway might play an important role in maintaining the CSC characteristics.