GLV-1h68 colonization of GI-101A tumors leads to blood vessel dilatation, destruction of pericytes, and increased vessel permeability. Athymic nude mice bearing human GI-101A tumors were retro-orbitally (r.o.) injected with 5 × 106 pfu of GLV-1h68 and tumors were harvested 42 days p.i.. (a) GLV-1h68-colonized GI-101A tumors showed increased vessel size (mean diameter 24.17 +/- 9.07 μm) compared to GI-101A control tumors (10.09 +/- 4.01 μm). The tumor vasculature was labelled with anti-CD31 antibody (red) and the diameter of all blood vessels (12-18 vessels/image) in 5 images (× 200 magnification) was measured using Leica IM1000 4.0 software. Shown are the mean values +/- standard deviations. (b) Confocal images showed destruction of pericytes in GLV-1h68-infected GI-101A tumors. Pericytes were labelled using Cy3-conjugated anti-SMA antibody (red), tumor vasculature was labelled with anti-CD31 antibody (blue), and viral infection was indicated by GFP fluorescence (green). (c, d) Extravasation of unspecific rat IgGs in 42-days-colonized (c) and control GI-101A tumors (d); mice were injected with 11 mg/kg rat IgGs 6 h before the tumors were fixed, histologically prepared and labelled with Cy3-conjugated anti-rat antibody to visualize extravasated IgGs (red). The tumor vasculature was labelled with anti-CD31 antibody (blue), GLV-1h68-infection was indicated by GFP (green), and nuclei were stained with Hoechst (orange). Surface plot profiles (ImageJ) of the fluorescence intensity of rat IgGs measured in whole tumor cross-sections demonstrate the enhanced extravasation of IgGs in GLV-1h68-colonized tumors. The asterisk (a) indicate a significant difference between experimental groups (*** P < 0.001; Student's t test). All images are representative examples. Scale bars represent 500 μm (a), 300 μm (b), 1 mm (c, d).