Figure 1.

Spatial relationship between tumor blood vessels and hypoxic regions in a malignant solid tumor. A tumor-bearing mouse with human cervical cancer cells, HeLa, was administrated with a hypoxia-marker, pimonidazole (red), and a perfusion marker, Hoechst33342 (blue), 90 and 1 min before sacrificing the animal, respectively. The tumor xenograft was surgically excised and its frozen section was stained with anti-pimonidazole antibody. Chronic hypoxia exists 70–100 μm from tumor blood vessels. Intermittent/cycling hypoxia influenced by fluctuations in tumor blood flow can be detected proximal to tumor blood vessels.