For cell proliferation assay, cells (800 well−1) were seeded on a 96-well plate and MTT assay was carried out daily over a 5-day course to evaluate cell proliferation. At the end of each culture period, 10 µl of the 12 mm MTT (#M6494, Invitrogen) was added to each well. After incubation for 4 h, 100 µl of 10% SDS solution was added, followed by incubation for another 4 h. The absorbance was read at 570 nm. For colony-formation assay, 1 × 103 K1 cells or 5 × 103 BCPAP cells were plated in triplicate on a six-well plate with a bottom layer of 0.7% agar and a top layer of 0.35% agar. The total number of colonies ≥100 μm in diameter was counted and representative areas were photographed under a microscope after 3 weeks of culture.