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

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.

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.

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 viv o, suggesting that CD133 expression is not restricted to cancer-initiating cells in the human lung cancer cell line LC-42.