Angiostatin induces apoptosis in endothelial cells. BCE (1 and 2) or B16-F10 (3 and 4) cell monolayers were exposed overnight to phAst (2 μg/mL) in 0.5% serum, and apoptosis was assessed (A) by propidium iodide or (B) by TUNEL staining. (Lower panel) Quantitation of apoptosis as determined by TUNEL staining; data are pooled from two experiments, and results are expressed as the mean percentage (±SEM) of cells with evidence of apoptosis. Original magnification in (A) × 40.