Epigenetic regulation of angiogenesis

DNA methylation and histone deacetylation are two key epigenetic modifications that play central role in regulation of gene expression. Several studies have shown that histone deacetylases (HDAC) and DNA methyltransferases (DNMT) inhibitors are potent anti-angiogenic compounds. Though combination of HDAC and DNMT inhibitors are now being examined in clinical trials of hematological malignancies, little work has been done to understand the effect of this combination on physiological and tumoral angiogenesis. We designed a family of twin drugs with intrinsic HDAC and DNMT inhibitory activities and tested in relevant models of angiogenesis in vitro (Human Umbilical Vein Endothelial Cells – HUVEC and aortic ring) and in vivo (chick chorioallantoic membrane and Zebrafish). We have identified a lead compound (EPI) affecting global histone acetylation and having quantifiable anti-angiogenic action without cytotoxic and apoptotic effect. In order to elucidate its anti-angiogenic mechanism, we characterized gene expression pattern simultaneously with the methylation profile of HUVEC cells treated with EPI and reference epigenetic modulators. This approach based on parallel microarray analyses permitted us to underscore a list of genes exclusively affected by EPI but not by other HDAC or DNMT inhibitors. These genes were then analyzed using the Ingenuity Pathway Analysis software revealing potential involvement of a subset of genes in angiogenesis. Our present aim is to validate the expression levels of a series of genes with respect to epigenetic mechanisms (histone modifications and DNA methylation). Finally, the biological relevance of the target genes will be explored by RNA silencing. Hence, we are using these novel epigenetic modulators as a tool to understand the regulatory mechanism of angiogenesis and to develop effective approaches to treat cancer