Rationale: Angiogenesis is a balanced process controlled by pro- and anti-angiogenic molecules of which the regulation is not yet fully understood. Besides classical gene regulation, miRNAs have emerged as post-transcriptional regulators of angiogenesis. In addition, epigenetic changes caused by histone modifying enzymes have emerged as modulators of angiogenesis as well. So far, the interplay between miRNA modulation and histone-modulating enzymes during angiogenesis is unclear.

Objective: To investigate the functions of miR-101 and of its target, the histone methyltransferase EZH2 in endothelial cells and angiogenesis.

Methods and Results: We show that the pro-angiogenic effects caused by VEGF-mediated down-regulation of miR-101 are partly mediated through reduced translational repression of the histone methyltransferase EZH2. In vitro, the sprouting and migratory properties of primary endothelial cell cultures were reduced by inhibiting EZH2 through up-regulation of miR-101, siRNA-mediated knockdown of EZH2, or treatment with 3-Deazaneplanocin A (DZNep), a small molecule inhibitor of EZH2 methyltransferase activity. In addition, we studied the effects of EZH2 inhibition on tumor angiogenesis in vivo. We found that systemic DZNep administration reduced the number of blood vessels in a subcutaneous glioblastoma mouse model, without showing adverse toxicities.

Conclusion: By determining a pro-angiogenic VEGF/miR-101/EZH2 axis in endothelial cells we provide evidence that there is a functional link between growth factor-mediated signaling, post-transcriptional silencing, and histone methylation in the angiogenesis process. Inhibition of EZH2 may prove therapeutical in diseases in which aberrant vascularization plays a role.

Citation Information: Clin Cancer Res 2010;16(7 Suppl):B30