Anchorage-independent cell growth by soft agar assay. Soft agar assay was used to compare the colony forming ability of NPC-BM00 and NPC-BM29 cells in medium containing different concentrations of fetal calf serum (FBS) and cell numbers. Both the NPC-BM00 and NPC-BM29 cells were seeded with 1250, 2500, 5000 and 10000 cells per well in 24-well plates. The colonies were counted after 6 days of culture. Data are presented as the means ± standard deviation from experiments that were performed in triplicate wells. * referred to the level of significance at P < .05 and # P > .05.