Proliferation/viability of cells was determined using MTS assay as previously described with minor modifications . Briefly, a total of 3 × 103 cells in 100 μL of 10% FBS culture medium were seeded in 96-well plates. Once confluent, cells were cultured for 72 h before analysis. Then, the medium was aspirated and incubated with MTS solution (Promega, Madison, WI, USA) for 1 h. The viable cell number was reflected as the MTS absorbance which was measured spectrophotometrically at 490 nm. For evaluating the long-term proliferation of cells (colony formation assay), 1 × 103 tumor cells were plated into 60-mm dishes in 10% FBS culture medium. After 14 days, the cells were washed with PBS, fixed with methanol and 0.1% crystal violet. The colonies were counted and then photographed. All experiments were carried out in triplicate.