Fig. 5. Immunofluorescent CD31 (endothelial cells) and TUNEL(apoptosis) double-labeling of human pancreatic cancer growing in the pancreas of nude mice. Pancreatic tumors (L3.6pl cells) from mice treated with HBSS (control) gemcitabine, PKI166, or gemcitabine plus PKI166 were harvested on days 11, 18, and 23 of the treatment. The tissues were processed for immunohistochemistry using anti-CD31 antibodies (Texas Red) and TUNEL (FITC-green). A representative sample(×400) of this CD31/TUNEL fluorescent double-staining is shown. Fluorescent red, CD31-positive endothelial cells; fluorescent green, TUNEL-positive cells; fluorescent yellow, TUNEL-positive endothelial cells.