PPARγ is expressed in endothelium of normal and neoplastic tissues. (a) Immunofluorescent double staining for vWF and PPARγ demonstrates PPARγ expression in endothelium of normal skin. vWF-stained endothelial cells are shown in green, and PPARγ-positive cells are red. PPARγ-positive nuclei inside the endothelium appear yellow (arrows). Red cells are PPARγ-expressing mural cells. Scale bar, 20 μm. (b) In human glioblastoma tissue, PPARγ (red) is expressed in both tumor (arrowheads) and endothelial cells. Colocalization of red and green fluorescence indicates PPARγ in blood vessels (arrows). Scale bar, 20 μm. (c) Western blot analysis of PPARγ expression of cell lysates from isolated tumor endothelial cells from T241 fibrosarcoma (T-EC), and from cultured tumor cells including T241 fibrosarcoma (T241), rhabdomyosarcoma (RMS), liposarcoma (LS), glioblastoma (U87), and LLC. (d) Western blot analysis of PPARγ expression from isolated LLC tumor cells (LLC) and corresponding endothelial cells from LLC-GFP tumor (T-EC) and skin endothelial cells (N-EC). Levels of β-actin demonstrate protein loading. (e) Quantitation of autoradiographic signals. Values represent arbitrary densitometric units normalized for GAPDH signals. T-EC, tumor endothelium; N-EC, normal (skin) endothelium. (f) Western blot analysis of PPARγ protein showing higher expression in proliferating than in quiescent endothelium. Starv., starvation; Prolif., proliferation; Confl., confluent (contact inhibition). GAPDH levels are shown to demonstrate equal loading of protein in each lane.