Abstract LB-113: Non-small cell lung cancer cells with high ALDH1 activity display cancer stem cell properties and show chemoresistance

Abstract

Abstract Introduction Cancer stem cells (CSC) are believed to possess tissue stem cell-like properties such as self-renewal and toxicity resistance. These characteristics would facilitate tumor propagation and development of chemoresistance. The biology and regulation of CSC have mostly been studied in acute leukemia and certain solid tumors such as breast cancer. Relatively little data are available regarding CSC in non-small cell lung cancer (NSCLC) due to the lack of a specific CSC marker. This study aims to analyze the applicability of candidate CSC markers by utilizing chemotherapy treatment to enhance CSC proliferation in NSCLC cells. Methodology The expression or activity of 4 putative stem cell markers, CD24, CD44, CD133 and aldehyde dehydrogenase (ALDH1) were measured by flow cytometry in the NSCLC cell lines H1650, HCC827 and H358 before and after chemotherapy treatment for 24 hours. Tumor cells with enhanced marker expression after treatment were regarded as potential CSC, and were selected by fluorescence-activated cell sorting (FACS). Functional analysis was used to test for CSC properties in the marker+ and marker-subpopulations of untreated cells. The expression of genes involved in tissue stem cell functions were also compared by quantitative RT-PCR. Results Flow cytometry analysis showed amongst the 4 markers, only ALDH1+ subpopulation was significantly enhanced by chemotherapeutic treatment, suggesting ALDH1 could be a CSC marker. Untreated ALDH1+ cells formed significantly higher numbers and larger cell spheres in non-adherent culture medium than ALDH1− cells. Likewise, ALDH1+ cells formed significantly more and larger colonies in colony formation assay. Furthermore, MTT assay demonstrated higher resistance to cisplatin and etoposide treatments in ALDH1+ than ALDH1− cells. In addition, ALDH1+ cells showed more prominent tumorigenicity than ALDH1− cells in vivo; as few as 500 ALDH1+ cells formed xenograft tumor in SCID mice which were serially transplantable to 2nd and 3rd recipients, while no tumor was formed from ALDH− cells. Finally, expression analysis of sorted cells revealed higher expression of the pluripotency genes, OCT4, NANOG, BMI1 and SOX9, in ALDH1+ cells. Conclusion NSCLC cells expressing ALDH1 displayed higher capacity for cell renewal, tumorigenecity and drug resistance, as well as showed higher expression of pluripotency genes, suggesting that ALDH1 could be a useful CSC marker in NSCLC. Pathways mediated by the differentially expressed genes studied could be involved in CSC maintenance and/or chemoresistance in NSCLC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-113. doi:10.1158/1538-7445.AM2011-LB-113