Liver weight, cell proliferation, and apoptosis in EGFRi, ΔMET + EGFRi, and ΔMET mice. A: The percentage liver/body weight ratio. B: The percentage of Ki-67–positive hepatocytes. Labeled and total hepatocytes from three different microscopic fields/mouse were counted to determine the percentage labeling; each treatment group contained a minimum of three mice; a minimum of 2000 total hepatocytes were counted for each condition tested. C: The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)–positive hepatocytes per high-power optic field (20× objective) was counted. Labeled hepatocytes from three different microscopic fields/mouse were counted, with a minimum of three mice/condition. D: The number of TUNEL-positive nonparenchymal cells (NPCs) per high-power optic field (20× objective) was counted. Labeled NPCs from three different microscopic images/mouse were counted, with a minimum of three mice/condition. E: Representative TUNEL staining photomicrographs from day 10 control, EGFRi, ΔMET + EGFRi, and ΔMET mice. Arrow depicts a TUNEL-positive hepatocyte. Images taken using a 20× objective. Data are expressed as means ± SEM (A–D). ∗P ≤ 0.05, ∗∗P ≤ 0.01, and ∗∗∗P ≤ 0.001 versus control animals.