Direct Isolation and Characterization of “Flat” SV40-transformed Cells

Abstract

UNDER standard culture conditions cells of the permanent mouse embryo line BALB/c-3T3 cease to divide when cell to cell contact is made, and thus are characterized as sensitive to density dependent inhibition of growth. A loss of this aspect of growth control is commonly used as a selective means for recovering SV40-transformants because such transformed cells continue to divide in conditions in which nontransformed cells remain confined to the monolayer¹. SV40-transformants selected by their ability to overgrow the monolayer commonly attain population densities ten to fifteen times greater than nontransformed cells, although viral transformants of low saturation density termed “flat revertants” may be obtained from transformed clonal lines by negative selection with 5-fluoro-2-deoxyuridine², or by passage on cell layers fixed with glutar aldehyde³.