Effects of leucine supplementation on Panc02 tumor growth and apoptosis. (A) Differences in tumor volume between mice on control and calorie restriction (CR) diets with and without leucine (LEU) supplementation 4 weeks after tumor cell injections (control, control + LEU, and CR, n = 14/group; and CR + LEU, n = 13) (P <0.01 between control and both leucine-supplemented groups; P <0.001 between all other groups with different letters). (B) Comparison of immunohistochemical analyses performed on tumor sections for Ki-67 (n = 5/group; P <0.001 between all groups with different letters) and cleaved-caspase 3 (CC3) (n = 5/group; P <0.01 between the two leucine-supplemented groups; P <0.05 between all other groups with different letters). Scale bars represent 200 μm. Tumor volume is presented as mean ± SD, and Ki-67 and CC3 data are presented as mean ± SEM. Differences are considered significant if P <0.05. Abbreviations: CON, control diet; CR,calorie restriction diet; LEU, leucine-supplemented diet.