Epithelial cell adhesion molecule-positive (EpCAM+) hepatocellular carcinoma (HCC) cells may constitute a tumor-initiating subpopulation in tumorigenic cell lines and HCC specimens. In the present study, EpCAM+ circulating tumor cells (CTCs) were identified prospectively in HCC patients undergoing curative resection, and the prognostic significance and their stem cell-like characteristics were investigated further. Blood samples from 123 HCC patients were tested prior to resection and 1 month thereafter. CTCs were present in 66.67% of patients, and the cell count measured in 7.5 mL of blood (CTC(7.5) ) ranged between 1 and 34. Fifty-one patients had CTC(7.5) of ≥2 preoperatively, and these patients developed tumor recurrence earlier than those with CTC(7.5) of <2 CTCs (P < 0.001). A preoperative CTC(7.5) of ≥2 was an independent prognostic factor for tumor recurrence (P < 0.001). Its prognostic significance also applied to patients with alpha-fetoprotein (AFP) levels of ≤400 ng/mL or subgroups with low recurrence risk (all P < 0.05). A significant decrease of CTC-positive rates (66.67% to 28.15%, P < 0.05) and CTC(7.5) values (2.60 ± 0.43 to 1.00 ± 0.36, P < 0.05) was observed 1 month after resection. Patients with consistent CTC(7.5) <2 had lower recurrence rates than those with values consistently ≥2 (15.5% versus 87.50%, P < 0.001). EpCAM+ CTCs displayed cancer stem cell biomarkers (CD133 and ABCG2), epithelial-mesenchymal transition, Wnt pathway activation, high tumorigenic potential, and low apoptotic propensity.
Conclusion: Stem cell-like phenotypes are observed in EpCAM+ CTCs, and a preoperative CTC(7.5) of ≥2 is a novel predictor for tumor recurrence in HCC patients after surgery, especially in patient subgroups with AFP levels of ≤400 ng/mL or low tumor recurrence risk. EpCAM+ CTCs may serve as a real-time parameter for monitoring treatment response and a therapeutic target in HCC recurrence.
Copyright © 2012 American Association for the Study of Liver Diseases.