The sphere formation and tumorigenesis of lung cancer stem cells / 肿瘤

ABSTRACT

Objective: To induce the sphere formation from human lung adenocarcinoma cell line SPC-A1, identify cancer stem cells among the spheres, and evaluate their tumorigenic potential. Methods: The spheres were induced by incubation of cancer cells in the serum-free medium. The sphere formation was induced by epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), and fibroblast growth factor-10 (FGF-10). The stem cell-related markers were measured by RT-PCR and immunofluorescent staining in the resultant sphere-forming cells. Their tumorigenesis was tested in NOD/SCID mice. Results: The float-growing spheres (named pulmospheres) were developed after SPC-A1 cells were cultured for 5-10 days. RT-PCR demonstrated that the pulmospheres expressed the lung cancer stem cell surface markers (CD24 and CD221), the bronchioalveolar stem cell markers [surfactant proteins C (SP-C) and Clara cell secretory protein (CCSP)], the embryonic stem cell stemness genes (OCT4, Nanog, and Bmi-1), and the lung stem cell stemness gene (TTF-1). Among these markers, the expressions of SP-C, CCSP, and OCT4 were further evaluated with the immunofluorescent staining. Approximately 80 % of the sphere cells were shown to be positive for the proteins. The pulmosphere cells were highly tumorigenic in NOD-SCID mice, with tumor development after implantation of 5 × 103 cells per mouse. Conclusion: The lung cancer stem cells are enriched in the pulmosphere-forming cell population, which are tumorigenic.