Colony Morphology and Heritability of Anchorage-IndependentGrowth Among Spontaneously Transformed Balb/3T3 Cells

A clone of spontaneously transformed Balb/3T3 cells produced four different types of colonies in agar. Flat colonies arose at the interface between bottom and top layers of agar. two types of somewhat flattened compact colonies arose within the top layer. and mixed colonies developed when the compact colonies contacted the interface. The proportions of different colony types could be altered by varying the volume, concentration, and gelling rate of the agar. Spherical colonies only appeared in ungelled medium. None of the colony types bred true, showing that their morphologies depended on local conditions. When cells from a subpopulation with low colony-forming efficiency in agar (CFE) were cloned on plastic, all clones formed colonies in agar and did so with about the same CFE as the parental population. Colonies isolated from agar had no higher CFE than the parental population. The results indicate a great phenotypic heterogeneity in anchorage-independent growth, even in cloned populations of transformed cells.