Nevertheless, these SSEA-4+ cell-containing xenografts hardly expressed any Stro-1, CD117, ABCG2 or CD133 that were shown to label TICs evident in several osteosarcoma cell lines (Supplementary Fig. 1d)27, 28, nor did these xenografts contain any Hoechest-expelling side population (Supplementary Fig. 1e). This evidence concerns the gene ABCG2 and osteosarcoma.