In vitro and in vivo properties of CD133 expressing cells from human lung cancer cell lines

BACKGROUND: Tumor development is recently hypothesized to depend on a rare cell population with stem cell properties, such cells are called cancer stem cells (CSCs) or tumor-initiating cells (TICs). From various cancer tissues or cancer cell lines, CD133 expressing cells were found to define a unique CSC/TIC phenotype. To study whether that also could be the case in lung cancer, we examined different lung cancer cell lines for CD133 expression. RESULTS: Among the 4 cell lines studied, only the cell line LC-42 expressed CD133. Therefore, LC-42 was further characterized and studied with special emphasis on identifying the presence of CD133(+) CSCs/TICs. FACS sorted CD133(high) and CD133(dim) subpopulations from LC-42 showed no differences in soft agar colony-forming capacity and spheres-forming capacity in serum-free cultures. LC-42 cells contained Side Population (SP), and only SP cells were able to form spheres. Furthermore, Nanog expression was significantly higher in SP than in non-SP. However, no difference was observed of CD133 expression in SP and non-SP. When CD133(high) and CD133(dim) cells were serially xeno-transplanted in NOD/SCID mice, both formed tumours similar to their parental LC-42 cells. There were no expression differences for NANOG, OCT4 and SOX2 examined immunohistochemically in the xenografts from both cell fractions. CONCLUSION: Our data do not show a difference in tumorigenic potential of CD133(high) and CD133(dim) cells with respect to any of the parameters analyzed in vitro and in vivo, suggesting that CD133 expression is not restricted to cancer-initiating cells in the human lung cancer cell line LC-42.