Molecular mechanisms of action of angiopreventive anti-oxidants on endothelial cells: Microarray gene expression analyses

The anti-oxidants N-acetyl-l-cysteine (NAC) and (−)-epigallocatechin-3-gallate (EGCG) inhibit tumor vascularization by reducing endothelial cell migration and invasion in a similar, non additive and non synergistic manner but do not alter the growth of human umbilical vein endothelial cells. Here we address the effects of the two chemopreventive drugs on endothelial cell signaling by means of expression profiling and real-time PCR validation. We identify a series of angiogenesis related genes that are similarly regulated by the two drugs. Anti-oxidant treated endothelial cells show gene expression profiles compatible with a less activated, less apoptosis prone and less migratory phenotype. The anti-oxidants affect expression of several components of the TNFα response pathway including downstream genes that are regulated in the opposite direction in the absence of the inflammatory cytokine. The interference with the TNFα pathway is reflected by reduced NFκB activation in anti-oxidants treated cells but the compounds are not able to contrast TNFα mediated activation of NFκB. The chemopreventive action of these compounds thus relies on a reduction of basal levels of endothelial cell activation. Down-regulation of the TNFα responsive pro-metastatic, pro-inflammatory genes, urokinase plasminogen activator and selectin E, further implies anti-metastatic effects for these drugs.