Objective    To compare different sorting methods of side population cells in human tongue squamous carcinoma Tca8113 cells for side population cell enrichment.     Methods    Tca8113 cells were cultured in a conventional serum-supplemented medium (SSM) and a serum-free medium (SFM) separately

and side population cells were isolated through flow cytometry. The side population cells (SP cells) isolated from Tca8113 cells cultured with SSM were compared with those (TSC-SP cells) isolated from Tca8113 cells cultured with SFM through morphological observation

colony-formin

g assay

and tumorigenesis experiment.     Results    Tca8113 cells could grow in SFM and proliferate to form suspended tumor spheres containing stem-like cells after 3 to 5 d. The tumor spheres became more compact and had a larger volume when culture time increased. The content of SP cells in Tca8113 cells was 0.2%

while that of TSC-SP cells was 0.4%. The colony formation rates of SP cells and TSC-SP cells were both 100%. In the tumorigenesis experiment

tumors emerged on the backs of all nude mice 16 days after inoculated with 10

4

and 10

5

TSC-SP cells and SP cells.     Conclusion    Human tongue squamous  carcinoma Tca8113 cell line contains a small amount of side population cells

and SFM can be used for enriching tumor stem cell subgroups.