Diameter of tumor blood vessels is a good parameter to estimate HIF-1-active regions in solid tumors.

As the transcriptional activity of hypoxia-inducible factor 1 (HIF-1) is associated with resistance of tumor cells to current antitumor therapies, the spatiotemporal dynamics of HIF-1-active regions has been of great interest as a therapeutic target. In the present study, we established a unique cancer cell line, which changes color HIF-1-dependently, and monitored it during tumor progression. In imaging experiments, HIF-1-active cells appeared over the tumor xenograft, but dramatically decreased in number as blood vessels developed around the tumor. The remaining HIF-1-active cells at the center of the xenograft also disappeared after neovascularization. Thereafter, tumor growth was accelerated and HIF-1-active cells reappeared in different regions. The distance between HIF-1-active cells and the nearest vessels correlated to the diameter of the vessel (r=0.801). These results provide a basic knowledge of how to estimate the spatiotemporal dynamics of HIF-1-active cells using information about the image-guided architecture of tumor blood vessels.