The development of drugs for the control of
tumor angiogenesis requires a simple, accurate, and economical assay for
tumor-induced vascularization. We have adapted the orthotopic implantation model to angiogenesis measurement by using human
tumors labeled with
Aequorea victoria green fluorescent protein for grafting into nude mice. The nonluminous induced capillaries are clearly visible against the very bright
tumor fluorescence examined either intravitally or by whole-body luminance in real time. The orthotopic implantation model of human
cancer has been well characterized, and fluorescence shadowing replaces the laborious histological techniques for determining blood vessel density. Intravital images of orthotopically implanted human pancreatic
tumors clearly show angiogenic capillaries at both primary and metastatic sites. A quantitative time course of angiogenesis was determined for an orthotopically growing human prostate
tumor periodically imaged intravitally in a single nude mouse over a 19-day period. Whole-body optical imaging of
tumor angiogenesis was demonstrated by injecting fluorescent
Lewis lung carcinoma cells into the s.c. site of the footpad of nude mice. The footpad is relatively transparent, with comparatively few resident blood vessels, allowing quantitative imaging of
tumor angiogenesis in the intact animal. Capillary density increased linearly over a 10-day period as determined by whole-body imaging. Similarly, the
green fluorescent protein-expressing human
breast tumor MDA-MB-435 was orthotopically transplanted to the mouse fat pad, where whole-body optical imaging showed that blood vessel density increased linearly over a 20-week period. These powerful and clinically relevant angiogenesis mouse models can be used for real-time in vivo evaluation of agents inhibiting or promoting
tumor angiogenesis in physiological microenvironments.