Purpose: To investigate the distribution, frequency, and clinical significance of mobilized endothelial progenitor cells (EPC) in hepatocellular carcinoma (HCC).

Experimental Design: In healthy controls and patients with HCC, the frequency of circulating EPCs was determined by colony-forming assays, fluorescence-activated cell sorting, and real-time PCR. One hundred sixty-five–amino acid form of vascular endothelial growth factor and platelet-derived growth factor-BB in plasma and tissue were quantified by ELISA. The distribution and frequency of EPCs were evaluated by immunofluorescence, immunohistochemistry, and real-time PCR in normal liver (n = 8), and tumor tissue (TT), adjacent nonmalignant liver tissue (AT), and tumor-free tissue 5 cm from the tumor edge (TF) from 64 patients with HCC. Clinicopathologic data for these patients were evaluated.

Results: Compared with values for healthy controls, colony-forming unit scores were higher in the peripheral blood of patients with HCC. Plasma 165-amino acid form of vascular endothelial growth factor and platelet-derived growth factor-BB correlated with the expression level of the AC133 gene, which was also higher in the peripheral blood of patients with HCC. Immunohistochemical analysis showed that EPCs were incorporated into the microvessels in cirrhotic and tumor tissue. Compared with normal liver (9.00), increased AC133⁺ microvessel density (microvessels/0.74 mm²) was found in TT (53.56), AT (84.76), and TF (48.33). The levels of AC133 gene expression and AC133-microvessel density in AT, which were the highest among four groups, correlated with clinicopathologic variables (the absence of tumor capsule, venous invasion, proliferating cell nuclear antigen intensity, and early recurrence).

Conclusions: Mobilized EPCs participate in tumor vasculogenesis of HCC. AC133 gene or antigen in peripheral blood and liver tissue could be used as a biomarker for predicting the progression of HCC.