CD133 has been widely used for identification and isolation of cancer stem cells in tumors although its role as a marker for cancer stem cell is still controversial . We isolated the CD133+ and CD133- cells from SW620 human colon cancer cell line and compared their biological characteristics, such as tumorigenicity,drug sensitivity, etc. Our study revealed that CD133+ SW620 cells were more tumorigenic and resistant to anti-cancer drugs. Correspondingly, they displayed different gene expression profile. However, it was observed that CD133- cells and CD133+ cells could mutually convert, indicating that CD133 expression was under dynamic and reversible regulations which might impose significant infulence on cells behaviors. Thus, our data challenge the role of CD133 as a marker for cancer stem cell.