A chorioallantoic membrane model for the determination of anti-angiogenic effects of imatinib.

Tumor angiogenesis is of major importance in the growth and metastasis of solid tumors, and the development of anti-angiogenic treatment strategies is thus a relevant option in oncology. The chorioallantoic membrane (CAM) model is a rapid and simple alternative to in vivo studies for the evaluation of anti-angiogenic compounds, thus allowing to reduce animal experiments and, upon establishment of robust and reproducible procedures, to more efficiently and objectively assess the anti-angiogenic efficacy of a given drug. In this paper, we compare two different methods for tumor establishment on a CAM model: (i) a Murine Urothelial Carcinoma (MB49) cell suspension mixed with Matrigel and (ii) an MB49 cell suspension absorbed in Gelfoam gelatin sponges. Based on the applicability of both methods for implant formation, we identify Gelfoam gelatin sponges as superior due to better attachment of the tumors on the membrane surface. For the precise quantitation of tumor xenograft growth and angiogenesis, we furthermore establish in this paper the electronic capturing of the xenografts and the computer-based analysis of the microscopic CAM images in order to determine the number of intersecting vessels and to measure vessel diameters. Beyond its direct effect on tumor cells by inhibiting the tyrosine kinase domain of the abl gene, imatinib has been reported to reduce the Bcr-Abl-mediated secretion of the angiogenesis factor VEGF and hence to interfere with angiogenesis. To test our CAM model for its ability to monitor anti-angiogenic effects, Gelfoam gelatin sponge-based tumor implants were treated by topical application of imatinib at various concentrations. Besides anti-tumor effects, we observed an inhibition of angiogenesis as determined by the number or total diameter of intersecting vessels. We also demonstrate that the calculation of the "blood vessel index" (vessel total diameter/tumor circumference) in our model allows to assess anti-angiogenic effects of imatinib independently of tumor growth inhibition. We conclude that our CAM assay and computer-based analysis represent a useful in vitro technique for the rapid assessment of anti-angiogenic effects of various agents.