Objective      To isolate and identify the lung cancer stem like cells from the established human lung adenocarcinoma cell line A549.       Methods      The A549 cells were cultured in serum-free condition medium to form tumor spheres. Colony formation assay and MTT assay were used to observe the colony formation ability. RT-PCR

Western blot analysis

and immunofluorescent staining were performed to compare the expression levels of stem cell markers between A549 cells and A549 tumor sphere cells.       Results      The stem  like cells were isolated from A549 cells in serum-free condition medium and formed typical neurospheres. The results showed that the proliferation and self-renewal capacity of the A549 sphere cells were stronger than A549 cells. A549 sphere cells expressed higher levels of stem cell markers Sox2 and Oct4 than A549 adhere cells (2.68±0.39 vs 0.05±0.02

1.23±0.12 vs 0.10±0.02

P0.05）.       Conclusion      The serum-free condition culture effectively enrich cancer stem like cells from human lung adenocarcinoma cell line A549.