and incubated for 14 days at
37 1C in a humidified atmosphere with 5% CO2. After culture, the
morphology of the colonies was examined using an inverted
microscope. A cluster containing more than 40 cells was considered
to be a colony. Individual colonies were plucked with a
10-ml micropipette tip under the inverted microscope; the colony
cells were then washed twice with PBS and stained with MayGrunwald
Giemsa