Tumorigenic lung tumorospheres exhibit stem-like features with significantly increased expression of CD133 and ABCG2

Accumulating evidence supports the existence of cancer stem cells (CSCs) in human tumors, and the successful certification of CSCs may lead to the identification of therapeutic targets, which are more effective for the treatment of cancer. The use of spherical cancer models has increased in popularity in cancer stem cell investigations. Tumorospheres, which are used as a model of CSCs and are established in serum-free medium supplemented with growth factors under non-adherent conditions, are one of the most commonly used cancer spherical models and are a valuable method for enriching the CSC fraction. To investigate whether this model is applicable in lung cancer (LC), the identification of lung CSCs and their capacities is essential. In the present study, lung CSCs were enriched by sphere-forming culturing and their stem-like properties were assessed. The results indicated that the lung tumorospheres had enhanced proliferation, clonality, invasion and cisplatin-resistance, and showed significantly increased expression levels of CD133 and breast cancer resistance protein (ABCG2). These results, together with findings previously reported in literature, indicated that the sphere-forming culturing of LC cells induced the enrichment of CSCs and that the tumorospheres exhibited stem cell characteristics. In addition, the higher expression levels of CD133 and ABCG2 in the tumorospheres may provide a rationale for therapeutic targets for LC.