Staining of histological sections demonstrates tumor response, decreased PI3K signaling, and decreased cell proliferation following rapamycin treatment.

<p>Following necropsy, colonic tumor tissue with adjacent colon epithelial tissue was formalin-fixed, paraffin-embedded, and underwent histological sectioning. Tissue was stained with H&E (<i>A</i>). Compared to placebo, a dramatic decrease in size was noted in the tumors from rapamycin-treated mice. The tumor pictured in <i>A, rapamycin</i> is from a FC3K mouse treated in a pilot of this study and chosen for this figure due to the observed dramatic partial response. In addition, the malignant columnar epithelium surrounding the mucinous lakes was diminished following rapamycin treatment as compared to control. Fewer pAKT and pS6-positive cells were observed in the tumors from mice treated with rapamycin as compared to tumors from mice given placebo (<i>B</i> and <i>C,</i> respectively). Tumor proliferation, as measured by Ki67, was also reduced in tumors from mice treated with rapamycin compared to those treated with placebo (<i>D</i>). Size bar: <i>A</i>, 1 mm. <i>B–D</i> are ∼3× enlargements.