Direct identification of drug-selected cancer stem-like cells from tumor xenografts by molecular imaging technique

1345 Objectives Cancer stem cells (CSCs) are a small subset of cancer cells capable of self-renewal and able to escape chemotherapy and metastasis. Although CSCs can be generated in vitro by non-adherent suspension culture in serum-free medium, the biologic characteristic of tumorspheres was far from CSCs in real tumors due to the distinct environmental factors, such as stroma cells, inflammation and hypoxia within tumor, which may profoundly reprogram CSCs. Histone deacetylase inhibitors (HDACIs) could induce epithelial to mesenchymal transition (EMT) and CSC characteristics in tumor cells. This study aimed to develop an in vivo CSCs-screening system using suberoylanilide hydroxamic acid (SAHA) to enrich the CSC population and facilitate the isolation of CSCs from solid tumor. Methods We established a H1299 non-small cell lung cancer cell clone that stably expressed a triple fused reporter gene (DsRedm-Fluc-tTKsr39). Tumor growths were tracked by in vivo luminescence imaging during continuous SAHA treatment of tumor-bearing mice. Using the Aldefluor assay, viable CSCs were isolated from xenografted tumors which co-express the reporter gene and ALDH activity. The stem cell phenotype of CSCs was assessed by a cell invasion assay, by analyzing CSC-related gene expression, and by immunohistochemical staining for ALDH1A1. Results Tumor tissues from SAHA-treated mice had enriched CSC population. Percent increased CSCs in SAHA-treated mice relative to vehicle-treated control mice was 4.14%, v.s. 1.50%. Genes involved in the maintenance of CSCs, self-renewal and metastasis were upregulated in isolated CSCs from SAHA-treated mice. In addition, the invasive ability of these cells was also significantly enhanced as compared to controls. Conclusions Using reporter gene and differential ALDH activity may allow us to track CSCs in a real-time manner and consequently to better understand the molecular mechanism of CSCs and lead to progress in cancer management.