MEK inhibition prevents K-Ras V12–mediated disruption of normal morphology. (A) 3D cultures expressing control (pQCXIP GFP) or K-Ras V12 (pQCXIP GFP K-Ras V12) were continuously treated with 5, 10, or 20 µM of the MEK inhibitor U0126 or 0.5, 1.0, or 2.0 µM of the PI3K inhibitor PIK-90. At day 10, these structures were fixed and stained for aPKC and DNA. Representative images are shown. Bar, 50 µm. (B) The midplanes of ≥50 structures were imaged for each condition in three independent experiments. Both the proportion of structures with normal morphology and the number of nuclei in the midplane of each structure were quantified. The means ± SEM are shown. ***, P < 0.0005.