One million cells were stained by incubating with 50 mL diluted primary or direct conjugated antibodies at 4°C for 45 minutes. The cells were washed thrice with PBS containing 0.1% sodium azide. For unconjugated primary mouse IgG antibodies, cells were incubated for 45 minutes with secondary anti-mouse IgG FITC. Stained cells were analyzed by flow cytometry. Isotype controls for the corresponding antibodies were used. The markers analyzed were mouse anti-human CD133 (50 μg/mL at a dilution of 1:10), FcR blocking reagent 10 μL/million cells (Miltenyi Biotech, Gladbach, Germany), PE-conjugated anti-human CD44 (0.2 mg/mL), APC-conjugated anti-human CXCR4 (0.5 mg/mL), FITC-conjugated anti-human CD90 (0.5 mg/mL), APC-conjugated mouse IgG2a κ-isotype control (50 μg/0.5 mL), PE-conjugated rat IgG2b isotype control (0.2 mg/mL), FITC-conjugated mouse IgG1 κ-isotype control (0.2 mg/mL), FITC-conjugated anti-mouse IgG1 (0.5 mg/mL; eBioscience, San Diego, CA), and mouse anti-human ABCG2 (250 μL culture supernatant; Abcam, Cambridge, UK). 7-Amino actinomycin D (50 μg/mL; BD Biosciences, San Jose, CA) staining was performed to eliminate dead cells from analysis. All antibodies were used at 1:100 dilution. The cells were analyzed with flow cytometry (FACS Diva software; BD Bioscience) on a customized system (BD-FACS Aria; BD Biosciences) using 488-nm blue laser and 633-nm red laser. Drop delay was calculated using fluorescent beads (BD Accudrop; BD Biosciences). The sample of case 6 was sorted based on the expression of CD44 and CXCR4 markers.