Flow cytometry analysis

Cells were seeded at the same density and collected when cells reached 80–90% confluence. A million cells for each sample were washed twice in FACS buffer (1% BSA in PBS), resuspended in 100 μl FACS buffer, then stained with 20 μl FITC mouse anti-human CD44 and PE mouse anti-human CD24 antibodies (BD bioscience) or FITC mouse IgG2b and PE mouse IgG2a isotype controls on ice for 1 h. Cells were washed with cold PBS twice and analyzed by FACS Canto II flow cytometer.