Figure 3.

Induction of mutant K-Ras with doxycycline promotes lung cell proliferation. The relative proportions of proliferating lung cells were determined by injection of Brdu and immunohistochemical staining after 3 h incorporation in bitransgenic mice that did not receive inducer (A), that received inducer for 14 d (B) or 2 mo (C), and that had inducer withdrawn for 3 d following 2 mo of treatment (D).