Expression of CD133, a possible marker for cancer stem cells (CSCs), in small cell lung cancer (SCLC) cell lines and non- small cell lung cancer (NSCLC) cell lines

e22100 Background: Cancer stem cell (CSCs) are believed to play important roles in tumor development, recurrence or metastasis. Identification of CSCs may have a therapeutic significance. CD133 expression has been shown on a minority of various human cancer cells with high capability of self-renewal and proliferation. Therefore, CD133 is thought to be one of possible markers for CSCs. Regarding human lung cancers, the existence, prevalence or roles of CD133 positive cells has not been fully understood. Methods: We examined CD133 mRNA by quantitative real-time PCR and sorted CD133-positive cells by fluorescence-activated cell sorting (FACS) using human small cell lung cancer(SCLC) and non-small cell lung cancer (NSCLC) cell lines. We evaluated differences of cell proliferation between CD133-positive and -negative cells by MTS assay in vitro and by subcutaneous injection for non- obese diabetic/severe combined immunodeficiency (NOD/SCID) mice in vivo. Results: CD133 expression was almost restricted in SCLC cell lines. CD133 mRNA expression or CD133-positive cell population was scarcely observed in NSCLC cell lines. In two SCLC cell lines examined (NCI-H82 and NCI-H69), CD133 positive cells had higher tumorgenicity both in vivo and in vitro than NSCLC cell lines. Conclusions: The expression status of CD133 is totally different between NSCLCs and SCLCs, probably reflecting the difference of these progenitor cells. Our results indicate that CD133-positive cells in SCLC cell are responsible for tumor growth. However, in view of their wide prevalence, CD133-positive cells do not seem to be a candidate for CSCs, at least in cell lines. To investigate the molecular and functional characteristics of CD133-positive cells may lead to a new therapeutic strategy for human lung cancers, especially for SCLCs. No significant financial relationships to disclose.