Fig. 1.

CD166⁺ cells from primary OS tissues display stem cell-like features and erlotinib resistant. a CD166⁺ cells were sorted from spheres by fluorescence-activated cell sorting. b Phase-contrast images of the ability of tumor spheres formation by seeding with CD166⁺ cells and CD166⁻ cells in serum-free medium. Scale bar, 50 μm. c Immunofluorescent staining of CD166 (green) and CD133 (red) expression in CD166⁺ spheres (nuclei stained with DAPI). Scale bar, 10 μm. d With the presence of erlotinib, cell viability of CD166⁺ OSCs and CD166⁻ cells were determined by MTT. Note: Columns, mean of three individual experiments; SD,** P < 0.01. e In vivo serial transplantation assay. A total of 10 ⁴ CD166⁺ OSCs or CD166⁻ cells from OS-1 or OS-5 in serum-free medium were injected s.c. into nude mice. Derived tumor xenografts were dissociated to single-cell suspension and then serially re-injected in mice (10 ⁴ cells), generating secondary and then tertiary tumors. Tumor growth curves of primary and tertiary tumors are shown. Note: Columns, mean of three individual experiments; SD, *** P < 0.001; SD,** P < 0.01