BACKGROUND: Talomerase activity inhibitor inhibits or kills renal carcinoma cells, and also affects stem cells that play importan roles in occurrence and development of renal carcinoma.OBJECTIVE: To observe renal carcinoma stem cell surface marker CD133 and telomerase activity expression in serum-free suspension culture, and to compare with renal carcinoma cells in serum suspension culture.DESIGN, TIME AND SETTING: The in vitro cytological study was performed at the Jiangsu University from June 2008 to Februar 2009.WIATERIALS: Fresh normal renal tissue surrounding renal carcinoma was obtained from Affiliated Hospital, Jiangsu University.Renal carcinoma stem cell line OS-RC-2 was supplied by Cell Bank, Chinese Academy of Sciences Shanghai Branch.METHODS: OS-RC-2 in logarithmic phase, digested by trypsin, and centrifuged. Supematant was removed. OS-RC-2 cell line in serum-free DMEM/F12 supplemented with epidermal growth factor and basic fibroblast growth factor was incubated at 2×105/L in 5% CO2 incubator at 37℃. Renal carcinoma cultured in serum and normal renal tissue served as controls.MAIN OUTCOME MEASURES: Cell growth was observed under an inverted microscope. Expression of CD133 and CD34 was detected using flow cytometry. Reel-time quantitative TRAP assay was applied to evaluate telomerase activity in renal carcinoma stem cells.RESULTS: After incubated in serum-free medium, renal carcinoma stem cells were round and suspended. Two days later, cell mass generated. Each cell mass contained 3-8 cells, with strong refraction. Seven days later, cell mass became more, presented big body that was regular, round or elliptical. CD133+CD34- rate in renal carcinoma stern cell mass was significantly greater in serum-free suspension culture compared with in serum suspension culture. CD133 and CD34 expression was not determined in normal renal tissue. There were significant differences among groups (F=328.25, P < 0.05). Telomerase activity was greater in renal carcinoma stem cells and renal carcinoma cells compared with normal renal ceils (F=-278.74, P < 0.05). No significant difference was detected between renal carcinoma stem cells and renal carcinoma cells.CONCLUSION: Compared with serum cultured renal carcinoma cells, serum-free cultured renal carcinoma cell surface marker CD133 presents high expression. Moreover, talomerase activity is high in renal carcinoma stem cells and renal carcinoma cells compared with normal renal tissue.