Antitumor effects of CCI-779. (A) Ki-67 staining of tumors. OPM-2- or 8226-challenged mice were treated with vehicle alone or 20 mg/kg CCI-779. Tumors were harvested at days 6 and 13 (8226 mice) or day 6 (OPM-2 mice), and sections were stained for Ki-67. Results represent area of microscopic field (original magnification, 20×) stained positively, assessed as described in “Materials and methods.” Data are mean ± SD, n = 10 fields, for each group. ^* denotes significant differences (P < .05) between control and CCI-779-treated mice. (B) Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining of tumors. Mice challenged and treated similarly to those described in panel A. Tumor sections stained by TUNEL assay to identify apoptosis. Results are number of TUNEL-stained apoptotic nuclei/microscopic field (original magnification, 20×), mean ± SD, n = 10 fields for each group. Asterisks denote significant differences (P < .05) between control and CCI-779-treated mice.