Abstract: Objective To isolate CD90⁺ （Thy-1⁺） cells from human hepatocellular carcinoma （HCC） cell lines and to study their stem cell properties. Methods Fluorescence-activated cell sorting was used to detect CD90 expression in five HCC cell lines：HepG2，SMMC-7721，Bel-7404，Bel-7403 and SK-Hep-1.The tablet clone formation test was used to measure the colony-forming ability of the sorted CD90⁺ cells，and the CCK-8 assay was used to analyze their proliferation ability and their sensitivity to cisplatin. Results CD90 expression was detected in 66.02% of Sk-Hep-1 cells.The pelletizing rate of these CD90⁺ cells was（18.6±2.95）% in the tablet colony formation assay， significantly higher than that of CD90^- and unsorted cells（P＜0.05）. Proliferation after 4 days in culture was significantly greater for CD90⁺ cells than for CD90^- and unsorted cells.Cisplatin inhibited growth of CD90⁺ cells by 14.8%，significantly less than it inhibited the growth of CD90^- cells （29.7%，P＜0.05） and unsorted cells （24.0%，P＜0.05）. Conclusion CD90⁺ cells are a subpopulation with tumor stem cell properties.CD90 may be a candidate biomarker for HCC stem cells.

Key words: Hepatocellular neoplasm, Fluorescence-activated cell sorting, CD90, Thy-1, Stem cell, Cisplatin, Drug resistance,neoplasm, Biological characteristics