Growth arrest states of RNA virus- and chemically transformed mouse cells.

Moloney virus- and benzo(a)pyrene-transformed cells, like the mouse BALB/c 3T3 cell line from which they are derived, arrest with a G1 DNA content in serum-deficient medium. The arrested cells are stimulated to proliferate by readdition of serum. The stimulated Moloney virus-transformed cells show identical kinetics of entry into S phase and also synthesize the same marker proteins as do growth-stimulated quiescent (G0) BALB/c 3T3 cells. In contrast, the benzo(a)pyrene-transformed cells enter S phase about 2 hr earlier and show a lower level of marker protein synthesis. Studies with cycloheximide indicate that protein synthesis is required for all three lines to resume DNA synthesis. Thus, it appears that transformed tumorigenic cells can have kinetic and biochemical growth properties very similar to those of their nontumorigenic parental cells.