Figure 6.

Pre-treatment with erlotinib induces stem cell-like features. (a) Staining of tumor cells for expression of ALDH following pre-treatment with erlotinib via FACS. Numbers indicate the percentage of ALDH^bright cells and the corresponding mean fluorescence intensity. (b) Tumor spheroid growth was assessed in both cells lines as indicated in ‘Materials and Methods' section. (c) Colony formation assay with indicated tumor cell lines left untreated or pre-treated with 100 nM erlotinib for 72 h. Graph depicts the average colony number from triplicate wells; right panel shows representative wells for each cell line. (d) HCC827 xenograft sections were stained for p27 via IHC. Tissues were counterstained with hematoxylin; original magnification of all images: 20 ×. (e) HCC827 and PC9 cells were transfected with a control non-targeting or a pool of small interfering RNAs directed against Slug; each transfected group was left untreated or exposed to erlotinib for 72 h and subsequently utilized in a TRAIL-mediated assay