(A & B) HMLERshECAD cells were treated with 30 µM PS for 48 h, and after removing the remaining compound were cultured for 14 days in serum-free culture media as floating cells to form mammospheres. SK-3rd cells were cultured with various concentrations of PS for 12 days to form mammospheres. 300 HMLERshECAD or SK-3rd cells were seeded in each well of 96 well plates. ***, P < 0.001 compared with control. (C) HMLERshECAD cells were treated with PS or salinomycin for 24 h and the relative mRNA levels of the indicated genes were determined by real-time PCR. *, P < 0.05; **, P < 0.01; ***, P < 0.001 compared to control.