FIG. 2.

p16^Ink4a expression correlates with crisis in Arf^−/− transformants. (A) Primary transformants from Arf^−/− bone marrow cells were analyzed during the outgrowth period by Western blotting using anti-p16^Ink4a and anti-β-actin antibodies. Representative samples are shown. The designations above the lanes indicate the presence (+) or absence (−) of crisis. C, L1-2, a fully established Ab-MLV transformant that expresses abundant p16^Ink4a (29). (B) Densitometry was used to compare levels of p16^Ink4a in primary transformants undergoing crisis to that in those that did not display crisis. Each point represents an individual cell line; the P value was obtained by using an unpaired, two-tailed t test.