CD133 is a temporary marker of cancer stem cells in small cell lung cancer, but not in non-small cell lung cancer

Lung cancer is the most common cause of cancer-related death worldwide. Current investigations in the field of cancer research have intensively focused on the 'cancer stem cell' or 'tumor-initiating cell'. While CD133 was initially considered as a stem cell marker only in the hematopoietic system and the nervous system, the membrane antigen also identifies tumorigenic cells in certain solid tumors. In this study, we investigated the human lung cancer cell lines A549, HI57, H226, Calu-1, H292 and H446. The results of real-time PCR analysis after chemotherapy drug selection and the fluorescence-activated cell sorting analysis showed that CD133 only functioned as a marker in the small cell lung cancer line H446. The sorted CD133(+) subset presented stem cell-like features, including self-renewal, differentiation, proliferation and tumorigenic capacity in subsequent assays. Furthermore, a proportion of the CD133(+) cells had a tendency to remain stable, which may explain the controversies arising from previous studies. Therefore, the CD133(+) subset should provide an enriched source of tumor-initiating cells among H446 cells. Moreover, the antigen could be used as an investigative marker of the tumorigenic process and an effective treatment for small cell lung cancer.