Expression of an Ets-1 dominant-negative mutant perturbs normal and tumor angiogenesis in a mouse ear model

We and others have shown that members of the Ets family of transcription factors are involved in morphogenic properties of endothelial cells in vitro. To investigate the role of these factors in the transcriptional regulation of angiogenesis in vivo, we set up a nontraumatic model that allows daily macroscopic examination of both growth factor- and tumor-induced angiogenesis in mouse ears. In the same animal, we were thus able to record variations in the patterns of neovessels induced and cell populations recruited by the angiogenic factors FGF-2 and VEGF. In this model, inhibition of FGF-2-induced angiogenesis by the pharmacological compound TNP-470 was readily observed, demonstrating that the mouse ear model is also useful in the evaluation of antiangiogenic strategies. Our functional analysis of Ets transcription factors activity utilized a competitor protein, Ets1-DB, a dominant negative Ets1 mutant lacking the transactivation domain. Retrovirus-mediated expression of Ets1-DB inhibited FGF-2-induced angiogenesis, while the expression of Ets1-DB in cancerous and stromal cells disturbed tumor-induced angiogenesis. These results illustrate the value of the ear model and highlight the role of Ets family members in the transcriptional regulation of tumor angiogenesis.