BXPC-3, PANC-1 and SW1990 (all from Shanghai Genechem Co., Ltd., Shanghai, China) pancreatic cancer cell lines were cultured at 37°C in an atmosphere containing 5% CO2 in RMPI-1640 (Hyclone; Thermo Fisher Scientific, Inc.) or DMEM, supplemented with 10% FBS. Subsequently, CD44+CD24+ cells were sorted from the three cell lines using flow cytometry as previously described (19 (link),20 (link)).