The mechanisms governing the development of angiogenic blood vessels, which not only deliver the nutrients to growing tumors but also provide the conduits for tumor cell dissemination, are still not fully resolved. The model systems based on the grafting of human tumor cells onto the chorioallantoic membrane (CAM) of the chick embryo offer several advantages to study complex processes underlying tumor angiogenesis and tumor cell dissemination. In particular, the CAM model described here allows for investigation of multiple microtumors as independent entities, thereby greatly facilitating quantification and statistical analyses of tumor neovascularization and cancer spreading. This CAM microtumor system was designed specifically to measure the level of tumor cell intravasation in combination with quantitative analyses of the microarchitecture and permeability of the intratumoral angiogenic blood vessels. By using this newly established microtumor model we have demonstrated the functional involvement of tumor matrix metalloproteinase-1 (MMP-1) and epidermal growth factor receptor (EGFR) in regulating the development of a distinct angiogenic vasculature capable of sustaining tumor cell intravasation and metastasis.
Keywords: Animal models of cancer dissemination; Cancer metastasis; Chick embryo; Chorioallantoic membrane; Epidermal growth factor receptor; Matrix metalloproteinase 1; Tumor angiogenesis; Tumor cell intravasation; Tumor invasion; Vascular permeability.